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  • 1995-1999  (7,736)
  • 1975-1979  (4,294)
  • 1935-1939  (2,943)
  • General Chemistry  (14,087)
  • Magnetic resonance imaging
  • Nuclear reactions
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  • 101
    Electronic Resource
    Electronic Resource
    Chronic spinal subdural haematoma associated with intracranial subdural haematoma: CT and MRI (1999)
    Springer
    Neuroradiology 41 (1999), S. 137-139 
    Details
    ISSN: 1432-1920
    Keywords: Key words Spinal subdural haematoma ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Chronic spinal subdural haematoma is a uncommon. We describe the CT and MRI appearances of chronic spinal and intracranial subdural haematomas following minor trauma. The aetiology, pathogenesis and differential diagnosis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050719
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  • 102
    Electronic Resource
    Electronic Resource
    Cryptococcus meningoencephalitis in AIDS: parenchymal and meningeal forms (1999)
    Springer
    Neuroradiology 41 (1999), S. 129-133 
    Details
    ISSN: 1432-1920
    Keywords: Key words Cryptococcosi ; Acquired immunodeficiency syndrome ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract CT and MRI in one case of Cryptococcus neoformans infection showed contrast-enhancing parenchymal lesions resembling granulomata or abscesses. After an initial phase without contrast enhancement, the full extent of the lesions was visible within 2 weeks of presentation. The enhancing masses were assumed to represent intracerebral cryptococcomas. Despite evidence of massive meningeal infection on cerebrospinal fluid (CSF) examination, no radiological signs of meningitis, invasion of the Virchow-Robin spaces or ventriculitis could be demonstrated. With antimycotic treatment the contrast enhancement disappeared and cystic, partly calcified lesions remained. Recurrence of meningeal infection without radiological correlates was apparent in this stage. In a second case of proven cryptococcus meningitis, dilation of Virchow-Robin spaces or cysts in the adjacent parenchyma were the main abnormalities on MRI. Enhancing masses were not detected. These cases may represent two different reactions of the immunocompromised hosts to infection with C. neoformans: widening of the perivascular spaces as a correlate of the more typical meningeal infection and enhancing parenchymal lesions as a sign of further invasion from the CSF spaces. Enhancement of cryptococcomas, indicating an inflammatory response in the surrounding brain, is not typical in patients with impairment of immune function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050717
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  • 103
    Electronic Resource
    Electronic Resource
    MRI characteristics of midbrain tumours (1999)
    Springer
    Neuroradiology 41 (1999), S. 158-162 
    Details
    ISSN: 1432-1920
    Keywords: Key words Midbrain ; tumours ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We diagnosed 60 cases of midbrain tumours by MRI between 1993 to 1997. There were 39 males and 21 females, aged 2–64 years, mean 25.6 years. We found 38 patients with true intramedullary midbrain tumours, 11 predominantly in the tectum, 20 in the tegmentum and 7 with a downward extension to the pons; there were 7 within the cerebral aqueduct. There were 22 patients with infiltrating midbrain tumours extending from adjacent structures, 11 cases each from the thalamus and pineal region. All patients received surgical treatment. Gross total resection was achieved in 42 cases, subtotal (〉 75 %) resection in 18. Pathological diagnoses included 16 low-grade and 15 high-grade astrocytomas; 5 oligodendroastrocytomas; 2 ependymomas; 11 glioblastomas; and 11 pineal parenchymal or germ-cell tumours. Midbrain tumours are a heterogeneous group of neoplasms, with wide variation in clinical and MRI features, related to the site and type of tumour. MRI not only allows precise analysis of their growth pattern, but also can lead to a correct preoperative diagnosis in the majority of cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050723
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  • 104
    Electronic Resource
    Electronic Resource
    Hyperacute infarction: a comparison of CT and MRI, including diffusion-weighted imaging (1999)
    Springer
    Neuroradiology 41 (1999), S. 175-178 
    Details
    ISSN: 1432-1920
    Keywords: Key words Infarct ; cerebral ; Computed tomography ; Magnetic resonance imaging ; diffusion-weighted
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared CT and MRI obtained within the first 3 h of onset of a cerebral infarct. Echo-planar diffusion-weighted MRI delineated the infarcted areas most clearly, and subtle low-density areas on CT were consistent with those shown to be abnormal by diffusion-weighted MR. The signal changes of affected areas on fast spin-echo proton-density, T2-weighted and fast FLAIR images were subtler than the low density on CT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050727
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  • 105
    Electronic Resource
    Electronic Resource
    High-intensity basal ganglia lesions on T1-weighted images in two toddlers with elevated blood manganese with portosystemic shunts (1999)
    Springer
    Neuroradiology 41 (1999), S. 195-198 
    Details
    ISSN: 1432-1920
    Keywords: Key words Shunt ; portosystemic ; Globus pallidus ; Manganese ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report two toddlers with portosystemic shunts who had symmetrical high-signal globus pallidus lesions on T1- but not T2-weighted MRI, and measurement of whole blood manganese at 2 years of age. These cases suggest that portosystemic shunts can cause elevation of blood manganese and result in manganese accumulation in the globus pallidus, causing high signal on T1-weighted images even in asymptomatic toddlers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050733
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  • 106
    Electronic Resource
    Electronic Resource
    MRI of acute cerebral infarcts: increased contrast enhancement with continuous infusion of gadolinium (1999)
    Springer
    Neuroradiology 41 (1999), S. 242-248 
    Details
    ISSN: 1432-1920
    Keywords: Key words Cerebral infarcts ; Magnetic resonance imaging ; Contrast enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared contrast enhancement on T1-weighted MRI of acute cerebral infarcts after conventional bolus administration and continuous infusion of gadolinium. We examined 12 patients with a history of acute stroke with contrast-enhanced MRI once a week for a 1 month. Only ischaemic lesions were investigated after cerebral haemorrhage had been excluded by CT. Each MRI study included T2- and proton density-weighted sequences for determination of the size and site of the infarct, immediate postinjection T1-weighted imaging after bolus administration of 0.1 mmol/kg gadolinium-DPTA and delayed T1-weighted imaging after additional continuous infusion of 0.1 mmol/kg over 2 h. A total of 42 MRI studies was performed. In the first week after the onset of stroke, most infarcts (8 of 10) did not enhance after bolus administration, whereas all showed distinct contrast enhancement after the infusion. In the following weeks all but two infarcts showed contrast enhancement after bolus administration; after continuous infusion contrast enhancement could be seen in all cases. While contrast enhancement after bolus administration showed the typical gyriform pattern, enhanced areas were more extensive after the infusion and usually covered the entire infarcted area shown on T2- and proton density-weighted images. We presume that the disturbed blood-brain barrier in ischaemic areas favours delivery of contrast medium to the infarcted tissue if it is offered continuously so that a steady state can develop.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050740
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  • 107
    Electronic Resource
    Electronic Resource
    Cortical tubers without other stigmata of tuberous sclerosis: imaging and pathological findings (1999)
    Springer
    Neuroradiology 41 (1999), S. 428-432 
    Details
    ISSN: 1432-1920
    Keywords: Key words Tuberous sclerosis ; Magnetic resonance imaging ; Focal cortical dysplasia ; Cortical dysgenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is immense variability in the clinical presentation of tuberous sclerosis and many incomplete forms (formes frustes) exist. To investigate the imaging characteristics of cortical tubers seen in tuberous sclerosis unaccompanied by other stigmata, we reviewed MRI and CT of six patients who met the criteria for a definitive diagnosis of TS, established solely by the presence of a histologically confirmed cortical tuber. Five of the patients had a solitary cortical tuber and the last had three lesions, one of which was resected and confirmed histologically. The other two lesions were included in our study. CT showed five tubers as low density, but three were not identified. No calcified or dense lesions were observed. MRI revealed peripheral components and inner cores of seven cortical tubers in five patients, with differing signal characteristics. The subcortical cores, with T1 and T2 prolongation, were separated from the overlying cortex. Abnormal inhomogeneous high signal was observed in both the cortex and subcortical white matter on proton-density weighted or FLAIR images. A radially orientated white-matter band was observed in one patient, and central depression of the expanded gyri in another. In one patient, a cortical tuber was atypical, with a thick cortex on T1-weighted images and a blurred grey/white matter junction with diffusely increased signal on T2-weighted images. Cortical tubers without other stigmata of tuberous sclerosis are shown to be distinct from focal cortical dysplasia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050777
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  • 108
    Electronic Resource
    Electronic Resource
    Cerebellar and basal ganglion involvement in Langerhans cell histiocytosis (1999)
    Springer
    Neuroradiology 41 (1999), S. 443-446 
    Details
    ISSN: 1432-1920
    Keywords: Key words Langerhans cell histiocytosis ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Langerhans cell histiocytosis (LCH) is a disease of unknown cause characterised by proliferation of histiocytic granulomas in tissues; the primary cerebral manifestation is diabetes insipidus caused by hypothalamic infiltration. We present a patient in whom, except for the absence of high signal on T 1 weighting in the posterior pituitary, consistent with central diabetes insipidus, MRI showed no evidence of hypothalamic involvement by histiocytosis, despite the long duration of the disease. However, there was bilateral, symmetrical involvement of the cerebellum and globus pallidus in addition to a calvarial lesion. High signal in the cerebellar white matter on T 2-weighted images may represent demyelination, gliosis and cell loss, as previously reported on pathologic examination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050781
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  • 109
    Electronic Resource
    Electronic Resource
    Successful surgical treatment of a dural arteriovenous fistula at the craniocervical junction with reference to pre- and postoperative MRI (1999)
    Springer
    Neuroradiology 41 (1999), S. 463-467 
    Details
    ISSN: 1432-1920
    Keywords: Key words Dural arteriovenous fistula ; Craniocervical junction ; Magnetic resonance imaging ; Venous hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a 62-year-old woman who presented with a myelopathy at the lower thoracic level. Left vertebral angiography revealed a dural arteriovenous fistula (DAVF) at the craniocervical junction, draining into an anterior spinal vein. Below the T 7 level, the spinal cord gave high signal on T 2-weighted images and enhanced with Gd-DTPA. The patient was successfully treated by simple clipping of vein draining the DAVF. The abnormal signal intensity and contrast enhancement rapidly regressed, except in the conus medullaris. Regression of the parenchymal abnormality on serial MRI following treatment corresponded closely with postoperative improvement of neurological function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050785
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  • 110
    Electronic Resource
    Electronic Resource
    Die spontane intrazerebrale Blutung aus klinisch- neuroradiologischer Sicht (1999)
    Springer
    Der Radiologe 39 (1999), S. 828-837 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Zerebrovaskuläre Erkrankungen ; Intrazerebrale Blutung ; Magnetresonanztomographie ; Computertomographie ; Key Words Cerebrovascular diseases ; Intracerebral hemorrhage ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Intracerebral hemorrhage is a common cause of acute neurological deterioration and a frequent indication for emergency neuroimaging. Stroke symptoms are caused in 10 to 15% by intracerebral hemorrhage. It is often not possible to differentiate intracerebral hemorrhage from cerebral ischemia by clinical examination. The therapeutic decision between thrombolysis or conservative therapy is comprised by the etiology. To exclude intracerebral hemorrhage as the cause of clinical symptoms, a CT is usually performed. Localisation and extension of the acute intracerebral hemorrhage are easy to detect. Subacute and chronic intracerebral hemorrhage are better delineated with magnetic resonance imaging. The different signal of the hemorrhage can be used for the age of the intracerebral hemorrhage. The cause of a non-traumatic intracerebral hemorrhage is in over 60% hypertony, less frequent alcoholism, malformation, or amyloid angiopathy. Uncommon causes of hemorrhage are head trauma, blood dyscrasia, tumor or venous thrombosis. Non-traumatic intracerebral hemorrhage are most common in patients between 50 and 70 years. In younger patients a malformation should be excluded with a cerebral angiography. Intracerebral hemorrhages are usually conservatively treated, in some cases an operative decompression is performed.
    Notes: Zusammenfassung Die intrazerebrale Blutung ist eine häufige Ursache akut auftretender neurologischer Symptome und führt oft zu einer notfallmäßigen neuroradiologischen Untersuchung. Etwa 15% der „Schlaganfälle” sind auf eine intrazerebrale Blutung zurückzuführen. Intrazerebrale Blutungen sind klinisch oft nicht von ischämischen Infarkten zu unterscheiden. Eine Computertomographie ist zur Zeit für die Diagnosesicherung – und damit auch zur weiterführenden Therapie – unerläßlich. Ausdehnung und Lokalisation der akuten intrazerebralen Blutung können damit schnell und sicher erfaßt werden. Subakute und chronische Blutungen sind dagegen verläßlicher mit der Magnetresonanztomographie nachweisbar. Aus der unterschiedlichen Signalgebung in den verschiedenen MR-Sequenzen kann auf das Alter der Blutung geschlossen werden. Die Ursache einer nicht-traumatischen intrazerebralen Blutung ist in über 60% der Fälle eine Hypertonie, weniger häufig die Folgen des Alkoholismus, Gefäßfehlbildungen oder die Amyloidangiopathie. Seltener sind Blutgerinnungsstörungen, Traumen, Tumoren, Venenthrombosen oder Intoxikationen die Ursachen einer intrazerebralen Blutung. Nicht-traumatische intrazerebrale Blutungen treten am häufigsten zwischen dem 5.–7. Lebensjahrzehnt auf. Bei jüngeren Patienten sind vor allem Gefäßfehlbildungen als Ursache zu berücksichtigen. Insbesondere bei jüngeren Patienten sollte zur ätiopathogentischen Klärung eine zerebrale Angiographie durchgeführt werden. Spontane intrazerebrale Blutungen werden in der Regel konservativ behandelt, außer man verspricht sich von der operativen Dekompression eine Verbesserung des klinischen Zustandes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050719
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  • 111
    Electronic Resource
    Electronic Resource
    Wertigkeit der Magnetresonanztomographie in der Diagnostik der Neurosarkoidose (1999)
    Springer
    Der Radiologe 39 (1999), S. 889-893 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Sarkoidose ; Neurosarkoidose ; Magnetresonanztomographie ; Key words Sarcoidosis ; Neurosarcoidosis ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Neurological involvement is a significant cause of morbidity and mortality in patients with sarcoidosis. The aim of this study was to evaluate the role of magnetic resonance imaging (MRI) in the diagnosis of patients with neurosarcoidosis. The MRI brain scans of 22 patients with sarcoidosis were retrospectively reviewed, along with the clinical information provided in the request form. All patients had signs and symptoms referable to the head and were examined with gadolinium enhancement. Cranial (facial) nerve paralysis was the most common clinical manifestation identified in 10 patients. A wide spectrum of MR findings was noted: periventricular and white matter lesions on T2 W spin echo images, mimicking multiple sclerosis (46%); multiple supratentorial and infratentorial brain lesions, mimicking metastases (36%); solitary intraaxial mass, mimicking high-grade astrocytoma (9%); solitary extraaxial mass, mimicking meningioma (5%); leptomeningeal enhancement (36%). The diagnosis of neurosarcoidosis is often difficult, particularly so in patients who lack either pulmonary or systemic manifestations of sarcoidosis. MRI shows a wide spectrum of brain abnormalities associated with neurosarcoidosis. These findings, however, are not specific for sarcoidosis and one must consider appropriate clinical circumstances in arriving at the correct diagnosis. In selected cases with isolated brain involvement, meningeal or cerebral biopsy may be required.
    Notes: Zusammenfassung Klinische Untersuchungen an Patienten mit systemischer Sarkoidose sprechen in 5%, Autopsieberichte in 25% für eine Beteiligung des Zentralnervensystems. Ziel der Studie ist eine Beurteilung der Beitrags der Magnetresonanztomographie (MRT) in der Diagnostik der Neurosarkoidose. Die MR-Tomogramme von 22 Patienten mit gesicherter Sarkoidose und neurologischer Symptomatik wurden retrospektiv ausgewertet. Häufigstes klinisches Symptom der Neurosarkoidose war eine Fazialisparese (10 Patienten). MR-tomographisch konnte eine Vielzahl verschiedener Befunde erhoben werden: periventrikuläre und Marklagerläsionen in T2-gewichteten Bildern in 46%, multiple bzw. miliare supratentorielle und infratentorielle Läsionen in 36%, solitäre intraaxiale Raumforderungen in 9%, solitäre extraaxiale Raumforderungen in 5% und meningeale Kontrastmittelanreicherung (nodulär oder diffus) in 36%. Schlußfolgerung: Die MR-tomographischen Befunde bei Neurosarkoidose sind oft wenig spezifisch. Die Diagnose wird meist bei gleichzeitigem Nachweis sarkoidosetypischer Granulome in anderen Organen gestellt, eine isolierte zerebrale Manifestation kann erhebliche diagnostische Schwierigkeiten bereiten. Die Neurosarkoidose sollte bei unklaren zerebralen Symptomen und Befunden stets in die Differentialdiagnose einbezogen werden, weil sie behandelbar ist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050727
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  • 112
    Electronic Resource
    Electronic Resource
    Rheumatische Erkrankungen des Sprunggelenkes und der Fußwurzel (1999)
    Springer
    Der Radiologe 39 (1999), S. 60-67 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Kalkaneus ; Talus ; Gelenkinstabilität ; Radiologische Diagnostik ; Ultraschall ; Magnetresonanztomographie ; Sprunggelenk ; Synovialmembran ; Arthritis ; Diagnose ; Bildgebende Diagnostik ; Key words Calcaneus ; Joint instability ; Plain film radiography ; Ultrasonography ; Magnetic resonance imaging ; Subtalar joint ; Ankle joint ; Arthritis ; Synovial membrane ; Synovitis ; Diagnosis ; Differential ; Diagnostic imaging ; Rheumatic disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Diseases of the hindfoot are associated with considerable functional impairment and therefore may hamper patients’ movements during gait considerably. Because of biomechanical overload, articular structures, tendons and ligaments are prone to early degenerative changes during the course of rheumatic diseases as visible with plain film radiography, sonography (US), or magnetic resonance imaging (MRI). Findings may occur as arthritis of major joints or in the form of fibroostitis and bursitis of the os calcis. Despite the progressive course of rheumatic diseases and characteristic imaging findings, high variability of X-ray signs may occur. Plain film radiograms and high-resolution ultrasonography play a key role in imaging rheumatic diseases of the hindfoot. MRI supports imaging diagnosis in selected cases. The principal goals of diagnostic imaging are precise and reproducible documentation of morphologic abnormalities and differentiated analysis for planning proper conservative or surgical treatment.
    Notes: Zusammenfassung Erkrankungen des Sprunggelenks und der Fußwurzel sind, da mit einer deutlichen Einschränkung der Beweglichkeit dieser Region einhergehend, für den Patienten meist sehr belastend. Bei rheumatischen Krankheitsbildern steht neben der Funktionseinschränkung vor allem in späteren Stadien die Destruktion biomechanisch stark beanspruchter Strukturen (hyaliner Knorpel, subchondraler Knochen, Bänder und Sehnen) im Vordergrund des klinischen wie auch des radiologischen Bildes. Grundsätzlich sind Arthritiden der großen Gelenke und die Calcaneopathia rheumatica zu beobachten. Trotz des meist stadienhaften Verlaufes mit charakteristischem Befallsmuster ist die bildgebende Diagnostik wegen der großen Formvariabilität der unterschiedlich ausgeprägten Veränderungen oft schwierig. Zusätzlich zu nativröntgenologischen Aufnahmen gehören die hochauflösende Sonographie, ergänzt durch die MRT, mit denen Gelenke und Sehnen direkt darstellbar sind, heute zur Standarddiagnostik. Ziel der Diagnostik ist einerseits die präzise reproduzierbare Dokumentation morphologischer Veränderungen zur Verlaufskontrolle, andererseits ihre möglichst differenzierte Analyse zur Einleitung adäquater konservativer oder operativer Therapiemaßnahmen, um Patienten zu einer aktiveren Lebensweise verhelfen zu können.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050478
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  • 113
    Electronic Resource
    Electronic Resource
    Das kernspintomographische Erscheinungsbild der spontanen intrazerebralen Blutung (1999)
    Springer
    Der Radiologe 39 (1999), S. 838-846 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Intrazerebrale Blutung ; Kernspintomographie ; MR-Angiographie ; Key words Intracerebral hematoma ; Magnetic resonance imaging ; Magnetic resonance angiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We review the signal characteristics of intracerebral hematomas (ICH) on magnetic resonance imaging (MRI), with special emphasis on the diagnosis of intracerebral hemorrhage within the first hours after stroke. The detection of peracute ICH was evaluated in 42 patients of a prospective, MR randomized stroke trial. These patients underwent a protocol of T1 and T2 weighted sequences, diffusion weigthed sequences and MR – angiography within 6 hours after onset of acute hemiparesis. The signal behaviour of ICH in any stage after bleeding was additionally reviewed in a retrospective series of 63 patients, who were submitted for MRI over a 12 months period because of known ICH. MRI correctly identified 4 hyperacute ICH in the prospective group and 4 hyperacute ICH in the retrospective group. These ICHs had high signal on T2 weighted images, were isointense in T1 weighted images and had signal voids on the diffusion weighted sequences. The signal intensities of acute, subacute and chronic ICHs correlated to previous experiences as reported in the literature. In conclusion, MRI reliably identified all hematomas even in the hyperacute stage. Diffusion weighted images were most sensitive to the presence of deoxyhemoglobine and helpful for the differentiation and characterization of acute ischemia. Therefore, MRI at 1.5 T can be employed as an alternative to CT for the emergency diagnosis of acute stroke.
    Notes: Zusammenfassung In dieser Übersicht wird das kernspintomographische (KST) Erscheinungsbild der intrazerebralen Blutung (IZB) anhand eigener Erfahrungen und der Literatur diskutiert. Besonderes Gewicht wurde auf den KST Nachweis der hyperakuten IZB innerhalb der ersten Stunden gelegt. Es wurden einerseits die Befunde von 42 Patienten einer prospektiven, KST randomisierten Schlaganfallstudie ausgewertet, bei denen die KST als Erstuntersuchung innerhalb von 6 Stunden durchgeführt worden war. Andererseits werteten wir retrospektiv jene KST Untersuchungen aus, die im Jahr 1998 unter der Fragestellung einer IZB (n=63) erfolgten. Die KST erwies sich als sensitiv im Nachweis auch der hyperakuten IZB. Es wurden weder falsch-negative noch falsch-positive Befunde erhoben. Die hyperakute IZB kommt in der T2-Gewichtung hyperintens und in der T1-Gewichtung isointens zur Darstellung. Auf den diffusionsgewichteten Sequenzen führen minimale Deoxyhämoglobinkonzentrationen bereits in dieser Phase zu Signalauslöschungen. Das Erscheinungsbild der akuten, subakuten und chronischen IZB entsprach dem, in der Literatur mitgeteilten, Signalverhalten. Zusammenfassend waren alle IZB, unabhängig vom Stadium in der KST nachweisbar. Die Diffusionsgewichtung war in der hyperakuten Blutungsdiagnose und deren Abgrenzung von der akuten Ischämie hilfreich. Zumindest bei 1,5T erscheint die KST somit für die Diagnostik des akuten Schlaganfalls geeignet und sollte, da Ischämien besser als mit der Computertomographie charakterisiert werden können, für die Akutdiagnostik verfügbar gemacht werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050720
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  • 114
    Electronic Resource
    Electronic Resource
    Vergleich der Wertigkeit der Computertomographie und der Magnetresonanztomographie in der Diagnostik der akuten intrazerebralen Blutung (1999)
    Springer
    Der Radiologe 39 (1999), S. 855-859 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Schlaganfall ; Intrazerebrale Blutung ; Magnetresonanztomographie ; Computertomographie ; Ratten ; Key words Cerebrovascular diseases ; Intracerebral hemorrhage ; Magnetic resonance imaging ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Background and Purpose: Stroke symptoms are caused in 10 to 15% by intracerebral hemorrhage. From the clinical examination it is often impossible to differentiate intracerebral hemorrhage from cerebral ischemia. To exclude intracerebral hemorrhage as the cause of clinical symptoms a CT is usually performed. The aim of our study was a direct comparison of the sensitivity of Computed Tomography and MRI using different MR sequences for the detection of acute intracerebral hemorrhage. Methods: In 8 male Wistar rats intracerebral hemorrhage was induced by infusion of collagenase into the caudate nucleus. After 1hour the brains were subsequently imaged with CT and MRI using T2- and T1-weighted Spin Echo sequences, diffusion-weighted sequences, T2*-weighted gradient echo sequences and FLAIR-sequences. Visibility of the intracerebral hemorrhage was examined using a scoring system from 1=not visible to 5=excellent visible. Finally, the intracerebral hemorrhage was verified by histological staining. Results: In all animals, intracerebral hemorrhage was visible in T2*-weighted gradient echo and diffusion weighted MR images 1 h after infusion of collagenase. T2- and PD-weighted SE images were positive in 7/8 rats. T1-weighted images revealed signal changes in 5/8 rats, and FLAIR sequence was positive in 8/8 rats. In CT intracerebral hemorrhage was only visible in 3/8 rats. When measuring the increase of Hounsfield units within the suspected hemisphere we saw a mean increase of 7% compared to the normal hemisphere in 3/8 rats. Conclusions: In this animal model, T2*-weighted magnetic resonance imaging proved to be the most sensitive imaging modality in the detection of acute intracerebral hemorrhage and is by far more sensitive than CT.
    Notes: Zusammenfassung Hintergrund und Ziel: Die Symptome eines Schlaganfalls sind in 10 bis 15% durch eine intrazerebrale Blutung verursacht. Oft ist es in der klinischen Untersuchung nicht möglich, zwischen einer intrazerebralen Blutung und einer zerebralen Ischämie zu differenzieren. Um eine intrazerebrale Blutung bei Schlaganfallsymptomatik auszuschließen, wird in der Regel zuerst eine Computertomographie (CT) durchgeführt. Ziel der vorliegenden Studie ist ein direkter Vergleich der Sensitivität der CT mit verschiedenen magnetresonanztomographischen (MR) Sequenzen in der Diagnostik der akuten intrazerebralen Blutung. Material und Methoden: Durch intrazerebrale Applikation von Kollagenase wurde bei 8 männlichen Wistar-Ratten eine intrazerebrale Blutung im linken Nucleus caudatus induziert. Nach einer Stunde wurden die Gehirne zunächst im CT und direkt anschließend in einem klinischen MR-Tomographen unter Verwendung von Protonendiche-, T2- und T1-gewichteten Spinechosequenzen, T2*-gewichten Gradientenechosequenzen, FLAIR-Sequenzen sowie diffusions- und perfusionsgewichteten Gradientenechosequenzen untersucht. Die Visibilität der Blutung wurde anhand einer Skala von 1 (=nicht sichtbar) bis 5 (=klar sichtbar) bewertet. Die Größe der Blutungsherde wurde für jede Untersuchungstechnik bestimmt und mit der Histologie verglichen. Ergebnisse: Bei allen Tieren konnte die Blutung in den T2*-gewichteten Gradientenecho-, FLAIR- sowie diffusionsgewichteten MRT-Bildern 1 h nach Kollagenaseinfusion erkannt werden. Auch in den T2- und Protonendichte-gewichteten Bildern konnte die Blutung bei 8/8 Ratten erkannt werden, wohingegen sie in den T1-gewichteten Aufnahmen nur bei 5/8 Ratten zu erkennen war. In der CT war die intrazerebrale Blutung nur bei 3/8 Ratten sichtbar, wobei bei diesen Tieren eine Zunahme der Dichte in Hounsfield-Einheiten (HE) in der Läsion um 15% auftrat. Schlußfolgerung: In dem verwendeten Tiermodell erwiesen sich T2*-und diffusionsgewichtete Aufnahmen sowie FLAIR-Sequenzen als sehr sensitive Methode in der Diagnostik der akuten intrazerebralen Blutung. Sie waren hierbei sensitiver als die CT. Deshalb sollte ein MR-tomographisches Untersuchungsprotokoll zur Diagnostik des akuten Schlaganfalls T2*- und diffusionsgewichtete Sequenzen beinhalten. Hierdurch gelingt eine rasche Unterscheidung zwischen der akuten intrazerebralen Blutung und der Frühphase der zerebralen Ischämie.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050722
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    Motor-learning-related changes in piano players and non-musicians revealed by functional magnetic-resonance signals (1999)
    Springer
    Experimental brain research 125 (1999), S. 417-425 
    Details
    ISSN: 1432-1106
    Keywords: Key words Motor learning ; Motor cortex ; Magnetic resonance imaging ; Musicians ; Hand motor skill
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study, we investigated blood-flow-related magnetic-resonance (MR) signal changes and the time course underlying short-term motor learning of the dominant right hand in ten piano players (PPs) and 23 non-musicians (NMs), using a complex finger-tapping task. The activation patterns were analyzed for selected regions of interest (ROIs) within the two examined groups and were related to the subjects’ performance. A functional learning profile, based on the regional blood-oxygenation-level-dependent (BOLD) signal changes, was assessed in both groups. All subjects achieved significant increases in tapping frequency during the training session of 35 min in the scanner. PPs, however, performed significantly better than NMs and showed increasing activation in the contralateral primary motor cortex throughout motor learning in the scanner. At the same time, involvement of secondary motor areas, such as bilateral supplementary motor area, premotor, and cerebellar areas, diminished relative to the NMs throughout the training session. Extended activation of primary and secondary motor areas in the initial training stage (7–14 min) and rapid attenuation were the main functional patterns underlying short-term learning in the NM group; attenuation was particularly marked in the primary motor cortices as compared with the PPs. When tapping of the rehearsed sequence was performed with the left hand, transfer effects of motor learning were evident in both groups. Involvement of all relevant motor components was smaller than after initial training with the right hand. Ipsilateral premotor and primary motor contributions, however, showed slight increases of activation, indicating that dominant cortices influence complex sequence learning of the non-dominant hand. In summary, the involvement of primary and secondary motor cortices in motor learning is dependent on experience. Interhemispheric transfer effects are present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050698
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    Pseudomyxoma retroperitonei (1999)
    Springer
    European radiology 9 (1999), S. 457-459 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Retroperitoneal neoplasms ; Retroperitoneal space ; Computed tomography ; Magnetic resonance imaging ; Ultrasonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We report a rare case of pseudomyxoma retroperitonei in a 58-year-old woman with a past history of severe appendicitis. The imaging showed a multicystic mass similar to pseudomyxoma peritonei, but the tumor was located in the retroperitoneal space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050692
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  • 117
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    Depression in Parkinson’s disease: brainstem midline alteration on transcranial sonography and magnetic resonance imaging (1999)
    Springer
    Journal of neurology 246 (1999), S. 1186-1193 
    Details
    ISSN: 1432-1459
    Keywords: Key words Parkinson’s disease ; Depression ; Brainstem midline ; changes ; Transcranial sonography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent studies using transcranial sonography (TCS) have provided evidence of alterations in the mesencephalic midline structures in patients with unipolar depression and depression in Parkinson’s disease (PD), suggesting an involvement of the basal limbic system in primary and secondary mood disorders. This study tested the hypothesis of brainstem midline abnormality in depression and investigated 31 PD patients by magnetic resonance imaging (MRI) and TCS. Signal intensity of the pontine and mesencephalic brainstem midline was rated on T2-weighted images and measured by relaxometry. In addition, two blinded investigators assessed the echogenicity of the brainstem midline by TCS. The severity of motor symptoms and depression were graded independently using standard research scales. Rating of signal intensity and T2 relaxometry of the pontomesencephalic midline structures revealed significant difference between depressed and nondepressed PD patients (P 〈 0.05). This corresponded to a significant reduction in mesencephalic midline echogenicity of depressed PD patients on TCS images. No correlation was found between raphe signal intensity, T2 relaxation times, or TCS echogenicity and the severity of motor symptoms or depression. This study is the first to show changes in signal intensity and T2 relaxation time of the pontomesencephalic midline structures on MRI in depressed PD patients confirming previous TCS findings. As these midline structures comprise fiber tracts and nuclei of the basal limbic system, the findings may support the hypothesis of an alteration in the basal limbic system in mood disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050541
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    Magnetic resonance imaging outcome of new enhancing lesions in relapsing-remitting multiple sclerosis patients treated with interferon β1a (1999)
    Springer
    Journal of neurology 246 (1999), S. 443-448 
    Details
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetic resonance imaging ; Enhancing lesions ; Interferon-β1a
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We investigated whether interferon-β1a modifies the course of new enhancing lesions in relapsing-remitting multiple sclerosis. Sixty-eight patients were studied by monthly magnetic resonance imaging (MRI) in a pretest-posttest design including 6 months of observation and 6 months of treatment. We examined the course of new Gd-enhancing lesions on two consecutive scans during observation and during treatment. Lesions detected during treatment were also analyzed by MRI 1 year later for persistence of enhancement, persistence of T2 hyperintensity, development of T1 hypointensity, or disappearance. Among the enhancing lesions detected by observation and treatment MRI, respectively, Gd-enhancement persisted at 2 months in 20% and 3% (P 〈 0.001), T2 hyperintensity persisted in 86% and 63% (P 〈 0.03), and T1 hypointensity developed in 49% and 15% (P 〈 0.01). Progression to T1 hypointensity was significantly more frequent in larger lesions during both the observation and treatment periods (P 〈 0.01). No reenhancement of plaques was present at 1-year follow-up; a further reduction in T2 hyperintensity (63% vs. 39%) was observed while T1 hypointensity remained unchanged. Both the duration of Gd enhancement and the short-term MRI course of new enhancing lesions benefited by treatment with recombinant interferon-β1a treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050380
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  • 119
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    Multiple sclerosis: interobserver agreement in reporting active lesions on serial brain MRI using conventional spin echo, fast spin echo, fast fluid-attenuated inversion recovery and post-contrast T1-weighted images (1999)
    Springer
    Journal of neurology 246 (1999), S. 920-925 
    Details
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetic resonance imaging ; Disease activity ; Fast spin echo ; Fast fluid-attenuated inversion ; recovery ; Reproducibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies have addressed the question of the precision in assessing multiple sclerosis (MS) activity by counting enhancing lesions on gadolinium enhanced brain magnetic resonance imaging (MRI). However, counting the active lesions on serial unenhanced MRI obtained by various pulse sequences has not been yet considered. We compared the interobserver levels of agreement in reporting active MS lesions on serial enhanced and unenhanced MRI to assess whether the use of various unenhanced techniques may change the degree of interobserver measurement reproducibility. Dual-echo conventional spin echo (CSE), dual-echo fast spin echo (FSE), fast fluid-attenuated inversion recovery (FLAIR) and Gd-enhanced T1-weighted brain MRI were obtained from five MS patients at baseline and monthly for 2 months. Six experienced observers independently identified and counted active MS lesions on the two follow-up MRI scans. Active lesions were considered to be all the enhancing lesions and any new or enlarging lesion on enhanced and unenhanced scans. Interobserver levels of agreement were calculated by weighted κ values. Very good agreement was reached only for counting total and new Gd-enhancing lesions. Good agreement was achieved for counting new lesions on the three unenhanced techniques, whereas the agreement for counting enlarging lesions was poor with all the MRI techniques. The level of agreement was significantly heterogeneous for various MRI techniques but not for various lesion sites. These results confirm that counting enhancing lesions is the most reliable method for assessing MS activity, but the use of any of the available unenhanced MRI techniques did not result in different levels of interobserver agreement when reporting new and enlarging MS lesions on serial scans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050483
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    Detection of anterior horn lesions by MRI in central European tick-borne encephalomyelitis (1999)
    Springer
    Journal of neurology 246 (1999), S. 1169-1171 
    Details
    ISSN: 1432-1459
    Keywords: Key words European tick-borne encephalitis ; Magnetic resonance imaging ; Central nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a case of central European tick-borne encephalitis with cervical myelitis presenting clinically as a lower motor neuron syndrome of the upper limbs with proximal asymmetrical pareses and atrophies. There were no sensory deficits nor signs of lesions of the spinal pathways or signs of encephalitis or meningitis. The affected motor fibers of the upper limbs were electrically inexcitable, but sensory findings were normal. Electromyography of the paralyzed muscles revealed pathological denervation activity without voluntary activation. The initial magnetic resonance imaging (MRI) showed a large hyperdense lesion in the anterior part of the cervical cord from C3 to T1. Despite the fact that MRI changes disappeared completely within 6 weeks the patient showed only little improvement in the paralyzed muscles after 6 months. To our knowledge, these MRI changes in patients with tick-borne encephalitis, consistent with an isolated anterior horn lesion, have never been reported previously. The course may have been aggravated by an initial antibiotic treatment with cephalosporins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050537
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    Bilateral reductions of hippocampal volume, glucose metabolism, and Wada hemispheric memory performance are related to the duration of mesial temporal lobe epilepsy (1999)
    Springer
    Journal of neurology 246 (1999), S. 926-933 
    Details
    ISSN: 1432-1459
    Keywords: Key words Temporal lobe epilepsy ; Hippocampus ; Magnetic resonance imaging ; Fluoro-2-deoxy-d-glucose positron-emission tomography ; Wada test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In refractory temporal lobe epilepsy (TLE) temporal lobe structures and functions are continuously or intermittently affected by abnormal brain electrical events, noxious neurochemical agents, and metabolic disturbances. There is conflicting evidence regarding the relationship between the duration of refractory mesial TLE and quantitative measures of temporal lobe functions and volumes of the hippocampi. Twenty patients (aged 28 ± 7 years, 14 males) with an initial precipitating injury before the age of 5 years were subjected to high-resolution magnetic resonance imaging, fluoro-2-deoxy-d-glucose positron-emission tomography (PET), and the Wada test. We investigated whether the duration of unilateral refractory TLE (12 left, 8 right) affects hippocampal volume, glucose metabolism, or Wada hemispheric memory performance. Ipsilateral to the epileptogenic zone the hippocampal volume, metabolism, and Wada hemispheric memory performance were reduced compared to the corresponding contralateral measures. The duration of epilepsy controlled for age at investigation, side of seizure origin, underlying cause, and sex were negatively correlated with ipsi- and contralateral hippocampal volume, hippocampal metabolism, and Wada hemispheric memory performance. Moreover, ipsilateral Wada hemispheric memory performance and contralateral hippocampal glucose metabolism were correlated with the frequency of habitual seizures. Refractory TLE seems to be associated with a slow but ongoing bilateral temporal lobe damage. These cross-sectional results require verification by longitudinal studies carried out over a period of more than two decades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050484
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  • 122
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    Disease activity in multiple sclerosis studied by weekly triple-dose magnetic resonance imaging (1999)
    Springer
    Journal of neurology 246 (1999), S. 689-692 
    Details
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetic resonance imaging ; Gadolinium-DTPA ; Triple dose ; Blood-brain barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study assessed whether dysfunction of the blood-brain barrier is an obligatory early event in lesion formation in multiple sclerosis. Dual-echo and T1-weighted magnetic resonance imaging after the injection of a triple dose (0.3 mmol/kg) of gadolinium-DTPA were obtained from ten patients with relapsing-remitting multiple sclerosis every week for 2 months. Sixty-four newly active lesions were detected by the two techniques. All the 44 new lesions seen on dual-echo scans enhanced during the early phases of their formation: 33 at their first appearance, 10 1 week before their appearance on the dual-echo scans, and one the week thereafter. When the every fourth (monthly) scan was analyzed, a total of 55 newly active lesions were detected (i.e., 14% active lesions would have been missed compared to the number found on weekly scanning). Thirty-one of them were detected by both dual-echo and triple-dose scans, 15 only by enhanced scans, and nine only by dual-echo scans. This study confirms that with highly sensitive magnetic resonance imaging techniques dysfunction of the blood-brain barrier is an obligatory early event in new lesion formation in relapsing-remitting multiple sclerosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050433
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    Contrast agents for magnetic resonance angiographic applications: 1H and 17O NMR relaxometric investigations on two gadolinium(III) DTPA-like chelates endowed with high binding affinity to human serum albumin (1999)
    Springer
    JBIC 4 (1999), S. 766-774 
    Details
    ISSN: 1432-1327
    Keywords: Gadolinium(III) complexes ; Contrast agents ; Magnetic resonance imaging ; Human serum albumin ; Proton relaxation enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: N,N′,N″,N‴ -pentaacetic acid) bearing different substituents for binding to human serum albumin (HSA) are compared. In spite of the structural differences of the recognition synthon and of the residual electric charge, the two chelates display an analogous binding affinity for the serum protein. Upon formation of the adducts with HSA, the exchange rates of the coordinated water appear slowed down by an amount corresponding to ca. 50% of the rates found for the free complexes. The relaxivity of [Gd(BOM)3DTPA (H2O)]2 −  is significantly higher than that of MS-325 either in the free complex or in the macromolecular adduct. Finally, the effect of pH on the stability of the HSA adducts and on the values of their relaxivities has been investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050349
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    Past, present and future of pediatric neuroradiology (1999)
    Springer
    Child's nervous system 15 (1999), S. 624-634 
    Details
    ISSN: 1433-0350
    Keywords: Key words Brain imaging ; Magnetic resonance imaging ; brain ; Magnetic resonance spectroscopy ; brain ; Computed tomography ; brain ; Diffusion imaging ; brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The last century has seen the evolution of neuroimaging from nonexistent to a group of techniques that, in our eyes, appears to be highly sophisticated. The rapidity of advancement in imaging has been concentrated in the last quarter century. There is no reason to expect this continual forward expansion of neuroradiology to abate; rather it seems likely that it will continue to increase at an even faster rate. The near future is one of refinement in imaging, faster and higher resolution as well as a much greater emphasis on physiology and biochemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003810050451
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    Dermal sinus and intramedullary spinal cord abscess Report of two cases and review of the literature (1999)
    Springer
    Child's nervous system 15 (1999), S. 202-207 
    Details
    ISSN: 1433-0350
    Keywords: Key words Abscess ; Spinal cord ; Dermal sinus ; Epidermoid ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intramedullary abscesses of the spinal cord are uncommon. Most of them occur in association with heart, pulmonary or urogenital infections. We report two cases of intramedullary spinal cord abscesses secondary to congenital dermal sinus. Only 14 cases of such an association have previously been reported. In our cases, dermal sinus was associated with an epidermoid tumour. The clinical presentation, pathogenesis, magnetic resonance imaging findings, surgical management and outcome are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003810050370
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    Giant posterior fossa teratoma (1999)
    Springer
    Child's nervous system 15 (1999), S. 359-361 
    Details
    ISSN: 1433-0350
    Keywords: Key words Computerized tomography ; Intracranial tumor ; Magnetic resonance imaging ; Posterior fossa ; Teratoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study we report a rare case of a giant midline posterior fossa teratoma; its clinical presentation, radiological appearance, treatment and outcome, with an extensive review of the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003810050413
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    Magnetic resonance imaging features of allografts (1999)
    Springer
    Skeletal radiology 28 (1999), S. 383-389 
    Details
    ISSN: 1432-2161
    Keywords: Key words Allografts ; Osteoarticular ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To investigate the magnetic resonance imaging (MRI) features of allografts at various time intervals after surgery in patients with osteoarticular allografts. Design and patients. Sixteen patients who were treated with osteoarticular allografts and who were followed over time with MRI studies as part of their long-term follow-up were retrospectively selected for this study. T1-weighted images were obtained both before and after gadolinium administration along with T2-weighted images. All images were reviewed by an experienced musculoseletal radiologist, with two other experienced radiologists used for consultation. Imaging studies were organized into three groups for ease of discussion: early postoperative period (2 days to 2 months), intermediate postoperative period (3 months to 2 years), and late postoperative period (greater than 2 years). Results. In the early postoperative period, no gadolinium enhancement of the allograft was visible in any of the MR images. A linear, thin layer of periosteal and endosteal tissue enhancement along the margin of the allograft was visible in images obtained at 3–4 months. This enhancement apeared gradually to increase in images from later periods, and appears to have stabilized in the images obtained approximately 2–3 years after allograft placement. The endosteal enhancement diminished after several years, with examinations conducted between 6 and 8 years following surgery showing minimal endosteal enhancement. However, focal enhancement was noted adjacent to areas of pressure erosion or degenerative cysts. All the cases showed inhomogeneity in the marrow signal (scattered low signal foci on T1 with corresponding bright signal on T2), and a diffuse, inhomogeneous marrow enhancement later on. Conclusion. We have characterized the basic MRI features of osteoarticular allografts in 16 patients who underwent imaging studies at various time points as part of routine follow-up. We believe that the endosteal and periosteal enhancement observed on MRI during the first few months to 2 years following surgery represents vascular ingrowth and early skeletal repair. The zone of periosteal enhancement could also include the new bone laid on the surface of the allograft through which the soft tissues bind to the cortex. The exact reason for the inhomogeneity in the marrow signal, and the diffuse, inhomogeneous marrow enhancement is not clear. This may represent saponified and/or necrotic marrow fat interspersed with the fibrovascular tissue. The features noted here should provide radiologists with useful information regarding imaging characteristics they can expect to see in other allograft replacement patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050534
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    The plantar fasciotomy: MR imaging findings in asymptomatic volunteers (1999)
    Springer
    Skeletal radiology 28 (1999), S. 447-452 
    Details
    ISSN: 1432-2161
    Keywords: Key words Plantar fascia ; aponeurosis ; Fasciitis ; Fasciotomy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To determine the postoperative appearance of the plantar fascia on MR imaging after a fasciotomy has been performed, and to compare the postsurgical appearance of the fascia after an open and endoscopic procedure.〈@head-abs-p1.lf〉Design and patients. Fifteen asymptomatic volunteers (12 women, 3 men; age range 22–49 years, mean age 33 years) with prior fasciotomies for treatment of longstanding plantar fasciitis were studied. Fourteen volunteers had a unilateral release and one volunteer had bilateral releases, allowing for assessment of 16 ankles. Eight fasciotomies were performed through an open incision and eight were performed endoscopically. The average time between surgery and imaging was 24 months (range 11–46 months). The site of surgery was established from the operative reports. Proton density (PD)-weighted and T2-weighted images in three orthogonal planes were obtained on a 1.5-T magnet. In eight studies, T1-weighted sagittal and STIR sagittal images were included. The fascia in each ankle was assessed for morphology and signal intensity. Perifascial soft tissues and bone marrow were assessed for edema. Preoperative MR studies were available in five volunteers.〈@head-abs-p1.lf〉Results. There was no apparent difference in the postoperative appearance of the ankle after an open or endoscopic procedure except for scar formation in the subcutaneous fat which was common after an open procedure (P〈0.05). Three ankles had a gap in the fascia (one open, two endoscopic). The plantar fascia measured a mean of 7.0 mm (range 5–10 mm) at the fasciotomy, and 8.3 mm (range 6–12 mm) at the enthesis. At the fasciotomy, 11 of 13 ankles had an indistinct deep contour and 9 of 13 had an indistinct superficial contour. At the enthesis, 13 of 16 ankles had an indistinct deep contour and 6 of 16 had an indistinct superficial contour. Compared with preoperative MR studies there was an average reduction in the fascial thickness at the enthesis of 14% (range 9–20%), but the thickness at the fasciotomy nearly doubled. No edema was evident in the fascia, perifascial tissues, deep plantar muscles, or calcaneal bone marrow.〈@head-abs-p1.lf〉Conclusions. The average thickness of the plantar fascia in asymptomatic volunteers after surgery is nearly 2–3 times that of normal. While there is increased thickness at the site of surgery, the changes in morphology and signal intensity were most prominent at the enthesis. The key observation was absence of edema in the fascia and perifascial soft tissues. This baseline information may be of value when assessing MR studies of symptomatic patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050544
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    Masses and pseudomasses of the hand and wrist: MR findings in 134 cases (1999)
    Springer
    Skeletal radiology 28 (1999), S. 498-507 
    Details
    ISSN: 1432-2161
    Keywords: Key words Hand ; Wrist ; Magnetic resonance imaging ; Soft tissue mass ; Neoplasm ; Tumour ; Tendon diseases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract   Objective. To assess the utility of magnetic resonance imaging (MRI) in the investigation of palpable masses in the hand or wrist.〈@head-abs-p1.lf〉Design and patients. We retrospectively reviewed the MRI examinations and case records of 134 patients referred because of a palpable mass in the hand or wrist. MRI was performed on a 1.0 T magnet using an extremity coil. Intravenous gadolinium-DTPA was injected when considered appropriate.〈@head-abs-p1.lf〉Results and conclusions. MRI demonstrated the cause of the palpable mass in 126 cases (94.02%). Soft tissue neoplasms were found in 34 cases (25.37%). The majority were benign and included giant cell tumours of tendon sheath, lipomas and hemangiomas and had a characteristic appearance. There were three malignant tumours (myxoid liposarcoma, malignant fibroushistiocytoma and rhabdomyosarcoma). Ganglia were found in 36 cases (26.86%) and non-tumour tendon pathology in 31 cases (23.13%). Less common causes included articular diseases (5.97%) and anatomical variants (4.47%). No focal lesion was present in 8 cases (5.97%). In conclusion, MRI is an accurate diagnostic technique in patients who present with a palpable mass of the hand and wrist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050553
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  • 130
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    Granular cell tumor of the subcutis: CT and MRI findings (1999)
    Springer
    Skeletal radiology 28 (1999), S. 96-99 
    Details
    ISSN: 1432-2161
    Keywords: Key words Computed tomography ; Granular cell tumor ; Magnetic resonance imaging ; Subcutis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Three cases of granular cell tumor (GCT) of the subcutis are presented. Computed tomography showed a mass isodense with muscle with an ill-defined margin. Magnetic resonance imaging showed a mass with inhomogeneous low signal intensity on both T1- and T2-weighted images. Another characteristic feature of subcutaneous GCT is its attachment in part to muscle. Histological examination confirmed the diagnosis in all cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050481
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  • 131
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    Electronic Resource
    Meningioma of the cavernous sinus in a child (1999)
    Springer
    Child's nervous system 15 (1999), S. 8-10 
    Details
    ISSN: 1433-0350
    Keywords: Key words Cavernous sinus ; Meningioma ; Child ; Ophthalmoplegia ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intracranial meningiomas in children are rare, representing 1–4.2% of central nervous system tumors and 1.5–1.8% of all intracranial meningiomas. Meningiomas arising from the lateral wall of the cavernous sinus account for less than 1% of all intracranial meningiomas. To our knowledge, only one case of a meningioma arising from the cavernous sinus has been reported in childhood. A 6-year-old boy presented with left ophthalmoplegia. A slight drooping of the left eyelid was noted at the age of 1 year. Magnetic resonance imaging (MRI) with contrast administration revealed an enhancing mass lesion located in the left cavernous sinus. The tumor, arising from the lateral wall of the cavernous sinus, was totally removed and the oculomotor nerve was reconstructed with a sural nerve graft. MRI displayed total tumor removal 1 month after the surgery. The pathological diagnosis was of a psammomatous meningioma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003810050318
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  • 132
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    Anterior sacral meningocele completely occupied by an epidermoid tumor (1999)
    Springer
    Child's nervous system 15 (1999), S. 209-211 
    Details
    ISSN: 1433-0350
    Keywords: Key words Anterior sacral meningocele ; Epidermoid tumor ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 2-year-old girl presented with an anterior sacral meningocele completely occupied by an epidermoid tumor. Preoperative magnetic resonance imaging had shown the meningocele with contents of the same intensity as cerebrospinal fluid. Surgery via a posterior sacral approach disclosed the tumor beneath an unexpected membrane inside the meningocele. Additionally, the presence of pus inside epidermoid tumor suggested that possible episodes of asymptomatic meningitis or other infection might have occurred before treatment, these being the major complication in anterior sacral meningocele. Therefore, we recommend that surgical treatment should be performed at the earliest possible stage in childhood, once the diagnosis is established, and dural plasty carried out to prevent infectious complications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003810050372
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  • 133
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    Die intrazerebrale Blutung im Rahmen der Amyloidangiopathie (1999)
    Springer
    Der Radiologe 39 (1999), S. 847-854 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Zerebrale Amyloidangiopathie ; Intrazerebrale Blutung ; Computertomographie ; Kernspintomographie ; Key words Cerebral amyloid angiopathy ; Intracerebral hemorrhage ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The purpose of our study was to evaluate the characteristic findings of acute hemorrhage due to amyloid angiopathy with computed tomography. 14 patients of intracranial hemorrhage with histologically confirmed cerebral amyloid angiopathy were observed over a period of 4 years. Characteristic findings were a lobar hemorrhage in superficial localisation, cortical involvment, subarachnoid hemorrhage, the multiplicity of hemorrhages and repeated episodes. Severe cerebral amyloid angiopathy is often accompanied by multiple petechial hemorrhages, restricted to a cortical-subcortical distribution, detectable by magnetic resonance imaging. These findings suggest that cerebral amyloid angiopathy is not a rare cause of atraumatic lobar hemorrhage. Amyloid angiopathy should be considered in any elderly patient with superficial intracerebral hemorrhage in an atypical location.
    Notes: Zusammenfassung In der Arbeit werden die computertomographischen Befunde der intrazerebralen Blutung im Rahmen der Amyloidangiopathie untersucht. 14 Patienten mit Massenblutung und histologisch bestätigter Amyloidangiopathie wurden in einem Zeitraum von 4 Jahren beobachtet. Charakteristische Befunde waren eine lobäre, oberflächlich gelegene Blutung, eine kortikale Beteiligung, eine begleitende Subarachnoidalblutung sowie ein mehrfaches und mehrzeitiges Auftreten der Blutungen. Eine schwere Amyloidangiopathie geht oft mit multiplen petechialen Blutungen in kortiko-subkortikaler Lokalisation einher, die sich kernspintomographisch nachweisen lassen. Die Befunde zeigen, daß die Amyloidangiopathie keine seltene Ursache einer nicht traumatischen lobären Blutung ist. Sie sollte daher bei jedem älteren Patienten mit einer intrazerebralen, oberflächlich gelegenen Blutung in atypischer Lokalisation in Betracht gezogen werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050721
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  • 134
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    Radiologisches Staging von thorakalen und abdominalen Tumoren im Kindesalter (1999)
    Springer
    Der Radiologe 39 (1999), S. 538-545 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Staging thorakoabdominaler Tumoren ; Kinder ; Computertomographie (CT) ; Magnetresonanztomographie (MRT) ; Malignome ; Key words Staging of tumors ; Thoracoabdominal tumors ; Childhood ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Thoracoabdominal tumors in childhood can arise from all organs and affect children from the neonate to the adolescent. Better prognosis of childhood tumors, due to better biological understanding and improvement of chemotherapy, require sufficient radiological staging. Sufficiency in radiological staging needs modern cross-sectional techniques with high resolution, good availability and lower radiation dose. In general computed tomography (CT) is being used for radiological staging; increasingly MR imaging is being used because of multiplanar imaging techniques. Replacement of invasive techniques such as myelography and lymphography and modern cross-sectional techniques create painless staging conditions. Nevertheless, scintigraphy will always be a major examination technique, especially for evaluation of metastases and postoperative control examinations. The most common thoracoabdominal tumors in childhood and their staging are described.
    Notes: Zusammenfassung Thorakale und abdominale Tumoren im Kindesalter nehmen ihren Ausgang von allen Organsystemen und können vom Neugeborenen bis zum Adoleszenten auftreten. Verbesserte Prognose, bedingt durch das bessere biologische Verständnis der Tumorerkrankung, sowie der effiziente Einsatz von Chemotherapeutika machen ein radiologisches Staging unumgänglich. Üblicherweise wird zum Staging die Computertomographie (CT) eingesetzt. Durch die Möglichkeit der multiplanaren Schnittführung und die bessere Auflösung bei Tumoren mit Beteiligung des ZNS wird in zunehmendem Maße die Magnetresonanztomographie (MRT) eingesetzt. Diese modernsten Schnittbildverfahren haben invasive Methoden wie Lymphographie und Angiographie in den Hintergrund gedrängt. Im weiteren werden die häufigsten thorakalen und abdominalen Tumoren im Kindesalter besprochen und deren Stagingsysteme erläutert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050548
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  • 135
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    Electronic Resource
    Präoperatives Staging des Kolorektalen Karzinoms (1999)
    Springer
    Der Radiologe 39 (1999), S. 562-567 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Kolorektales Karzinom ; Präoperatives Staging ; Endosonographie ; CT ; MRT ; Key words Colorectal cancer ; Preoperative staging ; Endosonography ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Carcinoma of the colorectum is one of the most frequent neoplasias, with an incidence of 40 in 100 000. For the effective use of new, differentiated, less invasive treatment options, exact preoperative staging of the tumor is essential. The introduction of endosonography in rectal tumor staging allows for exact differentiation of the rectal wall layers and thus of tumor stages 1–3 with median accuracy of 89%. Magnetic resonance imaging of the rectum, especially in double-contrast technique, can also be employed in high and stenosing tumors and leads to an average accuracy of 85% for the stages 1–4. Computed tomography is the method of choice in screening for metastases. In lymph node staging, all modalities show only moderate accuracy around 75%.
    Notes: Zusammenfassung Das kolorektale Karzinom stellt mit einer Inzidenz von 40 auf 100000 eine der häufigsten Neoplasien dar. Für den effektiven Einsatz neuer differenzierter Therapien mit geringerer Invasivität ist ein exaktes präoperatives Staging erforderlich. Die Einführung der Endosonographie im Tumorstaging erlaubt eine exakte Differenzierung der Wandschichten und damit der Tumorstadien 1–3 mit einer mittleren Genauigkeit von 89%, die Magnetresonanztomographie des Rektums, insbesondere in Doppelkontrasttechnik, kann auch bei hohen und stenosierenden Tumoren angewendet werden, bei einer Genauigkeit von durchschnittlich 85% für die Stadien 1–4. Die Computertomographie ist Methode der Wahl im Metastasenscreening. Im Lymphknotenstaging zeigen alle Modalitäten nur bescheidene Genauigkeiten um 75%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050551
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  • 136
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    Serial magnetic resonance imaging of the donor site after harvesting the central third of the patellar tendon A prospective study of 37 patients after arthroscopic anterior cruciate ligament reconstruction (1999)
    Springer
    Knee surgery, sports traumatology, arthroscopy 7 (1999), S. 20-24 
    Details
    ISSN: 1433-7347
    Keywords: Key words Donor site morbidity ; Anterior cruciate ligament ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract The aim of this prospective study was to follow the development of repair tissue in the donor-site area using serial magnetic resonance imaging (MRI) evaluation and to assess whether the MRI findings were correlated with donor-site morbidity. Thirty-seven consecutive patients with unilateral anterior cruciate ligament injuries undergoing elective reconstruction of the ligament were included in the study. They were aged 27 (range 14–50) years. The graft was harvested through two 25-mm vertical incisions with the aim of protecting the infrapatellar nerve and sparing the paratenon. The tendon defect was left open. The patients underwent MRI evaluation at 6 weeks, 6 months and 27 months postoperatively. A final clinical follow-up was made 25 (range 23–29) months postoperatively. MRI demonstrated that the donor-site gap, i.e. the area corresponding to a pathological non-tendinous-like tissue signal, was 9 (range 4–18) mm at 6 weeks, 5 (range 2–14) mm at 6 months and 2 (range 0–5) mm at 27 months. The size of the donor-site gap had significantly decreased at 6 months compared with 6 weeks (P = 0.0001), as well as at 27 months compared with 6 months (P = 0.0001). We conclude that the patellar tendon at the donor site healed gradually, as expressed by a decrease in the area of non-tendinous-like tissue signal on the serial MRI evaluations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001670050115
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  • 137
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    Magnetic resonance imaging of meniscal degeneration in torn menisci: a comparison between anterior cruciate ligament deficient knees and stable knees (1999)
    Springer
    Knee surgery, sports traumatology, arthroscopy 7 (1999), S. 274-277 
    Details
    ISSN: 1433-7347
    Keywords: Key words Meniscus ; Degeneration ; Magnetic resonance imaging ; Histology ; Chronicity of the meniscal tear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract Signal anomalies observed in magnetic resonance imaging of the intrameniscal tissue adjacent to the tear were compared between stable knees (group 1, 54 menisci) and anterior cruciate ligament (ACL) deficient knees (group 2, 98 menisci). The histological significance of these signal anomalies was also studied (n = 25). The frequency of intrameniscal signal anomalies adjacent to the tear was significantly lower in ACL-deficient knees than in ACL-stable knees (P = 0.0022). There was a close correlation between the imaging anomalies and the presence of histological lesions (fissures, degeneration) within meniscal tissues adjacent to the tear (sensitivity: 0.95, specificity: 0.60). Our results suggest that the severity of intrameniscal degenerative changes adjacent to the tear are lower in ACL-deficient knees than in ACL-stable knees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001670050163
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  • 138
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    Early diagnosis of dementia: neuroimaging (1999)
    Springer
    Journal of neurology 246 (1999), S. 16-20 
    Details
    ISSN: 1432-1459
    Keywords: Key words Dementia ; Alzheimer’s disease ; Neuroimaging ; Magnetic resonance imaging ; Single photon emission computed tomography ; Atrophy ; Hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The use of neuroimaging is reviewed in the diagnosis of dementia, especially Alzheimer’s disease (AD). Computed tomography (CT) may be used to exclude other causes of dementia than AD. The finding of cortical or subcortical atrophy on CT or magnetic resonance imaging (MRI) itself does not indicate AD. Hippocampal atrophy on CT/MRI provides a useful early marker, although further longitudinal and neuropathological study is required. CT- and MRI-based measurements of hippocampal atrophy show promise in providing useful diagnostic information for discriminating patients with probable AD from normal elderly individuals. Using a standardized imaging protocol, including some assessment of hippocampal atrophy, can save costs since patients with suspected AD must undergo a cross-sectional imaging study to exclude other (treatable) causes of dementia. Combining an assessment of hippocampal atrophy with cerebral blood flow measurements by single photon emission computed tomography is not warranted either from a clinical or from an economic point of view.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050300
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  • 139
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    Electronic Resource
    Supratentorial atrophy in spinocerebellar ataxia type 2: MRI study of 20 patients (1999)
    Springer
    Journal of neurology 246 (1999), S. 383-388 
    Details
    ISSN: 1432-1459
    Keywords: Key words Spinocerebellar ataxia type 2 ; Magnetic resonance imaging ; Cerebral atrophy ; Disease duration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There have been only few studies of brain magnetic resonance imaging (MRI) in spinocerebellar ataxia (SCA) type 2. We investigated 20 SCA2 patients, from 11 Sicilian families, and 20 age-matched control subjects using MRI. Our data confirm that olivopontocerebellar atrophy (OPCA) is the typical pattern in SCA2. We found no significant correlation between infratentorial atrophy, disease duration, or the number of CAG repeats in our SCA2 patients, but there was supratentorial atrophy in 12 patients, with a significant correlation between supratentorial atrophy and disease duration. OPCA appears to represent the “core” of the SCA2: however, central nervous system involvement is not limited to pontocerebellar structures. We therefore consider central nervous system degeneration in SCA2 as a widespread atrophy. MRI is helpful in diagnosing SCA, but it is not diagnostic in the absence of clinical and molecular studies. We suggest that serial MRI may play a role in evaluating “in vivo” the progressive steps of neurodegeneration in SCA2, for a better comprehension of the pathophysiology of this disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050368
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  • 140
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    Electronic Resource
    Hochauflösende Kernspintomographie bei traumatischen Veränderungen an Fingergelenken (1999)
    Springer
    European journal of trauma 25 (1999), S. 224-229 
    Details
    ISSN: 1615-3146
    Keywords: Kerspintomographie ; Kollateralbandruptur ; Knorpelläsion ; Hochauflösende Oberflächenspule ; Magnetic resonance imaging ; Collateral ligament rupture ; Cartilage lesion ; High-resolution coil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Aim of this study was the evaluation of a prototype of a new high-resolution MRI coil for the detection of finger trauma. The practicability of this new coil for the assessment of traumatic lesions of the finger joints and the diagnostic value of this new method in clinical practice was assessed. Twenty patients between 13 and 50 years of age (mean 28 years) were examined with a 1.5-T whole-body-imager Magnetom SP 63 scanner (Siemens, Erlangen, Germany). A prototype of a high-resolution MRI coil with a diameter of 2.5 cm was used. T1- and T2-weighted images with an in plane resolution of 0.I95 x 0.098 mm were acquired. Bone structures, joint cartilage and capsule, ligaments, tendons and soft tissue alterations were assessed. All 19 patients with pathological changes at the finger joints had a joint effusion. With MR imaging, fractures were detected in almost all patients, compared with the X-ray examinations. Cartilage contusion showed high signal intensity. The collateral ligaments could best be assessed in the transversal, and ligament ruptures in the coronal plane. Hemorrhage in the tendon showed an increased signal intensity in T1- and T2-weighted, edema only in T2-weighted images. Especially traumatic lesions of cartilage and of ligaments can be sufficiently assessed by the high-resolution MRI due to its high anatomic resolution compared to common methods like X-ray. High-resolution MRI is practicable in clinical routine.
    Notes: Zusammenfassung Ziel der vorliegenden prospektiven Untersuchung war es, die Wertigkeit der hochauflösenden Kernspintomographie mittels einer speziellen Oberflächenspule in der Beurteilung von traumatischen Veränderungen der Fingergelenke zu evaluieren. Ferner sollte die Praktikabilität der Methode in der klinischen Routine überprüft werden. Es wurden 20 Patienten im Alter zwischen 13 und 50 Jahren (im Mittel 28 Jahre) an einem 1,5-T-Ganzkörpertomographen (Magnetom SP 63, Firma Siemens, Erlangen) untersucht. Als Spule wurde ein Prototyp einer hochauflösenden Oberflächenspule mit einem Durchmesser von 2,5 cm benutzt. T1- und T2-gewichtete Sequenzen mit einer maximalen Auflbsung in der Bildebene von 0,195 x 0,098 mm wurden zur Beurteilung von Knochen, Gelenkknorpel und -kapsel, der Sehnen und des Weichteilgewebes akquiriert. Kernspintomographisch fand sich bei 19 Patienten ein pathologischer Befund. Bei all diesen Patienten konnte ein Gelenkerguß nachgewiesen werden. Knöcherne Absprengungen, die anhand konventioneller Röntgenaufnahmen diagnostiziert wurden, zeigten sich kernspintomographisch als dislozierte signalreiche Strukturen. Gelenkknorpelkontusionen stellten sich hyperintens dar. Zur Beurteilung der Kollateralbānder eignete sich vor allem die koronare Schichtebene, da in dieser die Kollateralbdnder per continuitatem darstellbar sind. Sehneneinblutungen wiesen eine Signalerhöhung in T1- und T2-Wichtung auf. Ödeme der Weichteile und Bandstrukturen imponierten in T2-gewichteten Aufnahmen als signalreiche Strukturveränderungen. Aufgrund der hohen anatomischen Detailerkennbarkeit eignet sich die hochauflbsende Kernspintomographie als ergänzendes diagnostisches Verfahren zur nichtinvasiven Diagnostik von traumatischen Knorpel- und Bandläsionen. Unter Berücksichtigung des Zeitaufwandes handelt es sich dabei um eine im klinischen Alltag praktikable Methode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00596731
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  • 141
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    Perfusion impairments in infantile autism on technetium-99m ethyl cysteinate dimer brain single-photon emission tomography: comparison with findings on magnetic resonance imaging (1999)
    Springer
    European journal of nuclear medicine 26 (1999), S. 253-259 
    Details
    ISSN: 1619-7089
    Keywords: Key words: Autism ; Brain ; Technetium-99m ethyl cysteinate dimer ; Single-photon emission tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The neuro-anatomical substrate of autism has been the subject of detailed investigation. Because previous studies have not demonstrated consistent and specific neuro-imaging findings in autism and most such studies have been performed in adults and school-aged children, we performed a retrospective review in young children in search of common functional and anatomical abnormalities with brain single-photon emission tomography (SPET) using technetium-99m ethyl cysteinate dimer (ECD) and correlative magnetic resonance imaging (MRI). The patient population was composed of 23 children aged 28–92 months (mean: 54 months) who met the diagnostic criteria of autism as defined in the DSM-IV and CARS. Brain SPET was performed after intravenous injection of 185–370 MBq of 99mTc-ECD using a brain-dedicated annular crystal gamma camera. MRI was performed in all patients, including T1, T2 axial and T1 sagittal sequences. SPET data were assessed visually. Twenty patients had abnormal SPET scans revealing focal areas of decreased perfusion. Decreased perfusion of the cerebellar hemisphere (20/23), thalami (19/23), basal ganglia (5/23) and posterior parietal (10/23) and temporal (7/23) areas were noted on brain SPET. By contrast all patients had normal MRI findings without evidence of abnormalities of the cerebellar vermis, cerebellar hemisphere, thalami, basal ganglia or parietotemporal cortex. In conclusion, extensive perfusion impairments involving the cerebellum, thalami and parietal cortex were found in this study. SPET may be more sensitive in reflecting the pathophysiology of autism than MRI. However, further studies are necessary to determine the significance of thalamic and parietal perfusion impairment in autism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002590050385
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  • 142
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    Electronic Resource
    Effect of head-down tilt on brain water distribution (1999)
    Springer
    European journal of applied physiology 79 (1999), S. 367-373 
    Details
    ISSN: 1439-6327
    Keywords: Key words Cerebral edema ; Cerebrospinal fluid ; Head-down tilt ; Intracranial pressure ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Vascular and tissue fluid dynamics in the microgravity of space environments is commonly simulated by head-down tilt (HDT). Previous reports have indicated that intracranial pressure and extracranial vascular pressures increase during acute HDT and may cause cerebral edema. Tissue water changes within the cranium are detectable by T 2 magnetic resonance imaging. We obtained T 2 images of sagittal slices from five subjects while they were supine and during −13° HDT using a 1.5-Tesla whole-body magnet. The analysis of difference images demonstrated that HDT leads to a 21% reduction of T 2 in the subarachnoid cerebrospinal fluid (CSF) compartment and a 11% reduction in the eyes, which implies a reduction of water content; no increase in T 2 was observed in other brain regions that have been associated with cerebral edema. These findings suggest that water leaves the CSF and ocular compartments by exudation as a result of increased transmural pressure causing water to leave the cranium via the spinal CSF compartment or the venous circulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050522
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  • 143
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    Accuracy of Computational Hemodynamics in Complex Arterial Geometries Reconstructed from Magnetic Resonance Imaging (1999)
    Springer
    Annals of biomedical engineering 27 (1999), S. 32-41 
    Details
    ISSN: 1573-9686
    Keywords: Blood flow ; Magnetic resonance imaging ; Numerical flow modeling ; Carotid artery ; Three-dimensional ; Wall shear stress ; Atherosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Purpose: Combining computational blood flow modeling with three-dimensional medical imaging provides a new approach for studying links between hemodynamic factors and arterial disease. Although this provides patient-specific hemodynamic information, it is subject to several potential errors. This study quantifies some of these errors and identifies optimal reconstruction methodologies. Methods: A carotid artery bifurcation phantom of known geometry was imaged using a commercial magnetic resonance (MR) imager. Three-dimensional models were reconstructed from the images using several reconstruction techniques, and steady and unsteady blood flow simulations were performed. The carotid bifurcation from a healthy, human volunteer was then imaged in vivo, and geometric models were reconstructed. Results: Reconstructed models of the phantom showed good agreement with the gold standard geometry, with a mean error of approximately 15% between the computed wall shear stress fields. Reconstructed models of the in vivo carotid bifurcation were unacceptably noisy, unless lumenal profile smoothing and approximating surface splines were used. Conclusions: All reconstruction methods gave acceptable results for the phantom model, but in vivo models appear to require smoothing. If proper attention is paid to smoothing and geometric fidelity issues, models reconstructed from MR images appear to be suitable for use in computational studies of in vivo hemodynamics. © 1999 Biomedical Engineering Society. PAC99: 8719Uv, 8761-c, 0705Pj, 8710+e
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.163
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  • 144
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    Estimation of Tendon Moment Arms from Three-Dimensional Magnetic Resonance Images (1999)
    Springer
    Annals of biomedical engineering 27 (1999), S. 247-256 
    Details
    ISSN: 1573-9686
    Keywords: Medical imaging ; Magnetic resonance imaging ; Biomechanics ; Tendon moment arm ; Functional neuromuscular stimulation ; Tendon transfer surgery ; Hand biomechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract New three-dimensional (3D) magnetic resonance imaging (MRI) methods for measuring the tendon moment arm were created and were evaluated on the tendon moment arm of the flexor digitorum profundus at the third metacarpophalangeal joint. Using an open magnet MRI system and a hand holder, a series of static images were acquired at four joint angles and analyzed using specially created computer programs. Three methods were evaluated: (1) a 3D tendon excursion method that extended the method of Landsmeer; (2) a 3D geometric method whereby the moment arm was the perpendicular distance between the joint axis of rotation and the tendon path, and (3) a two-dimensional (2D) geometric method whereby single image slices were analyzed. Repeating the imaging and measurement processes, the 3D tendon excursion method was more reproducible (6% variation) than the 3D geometric method (12%), and both were much more reproducible than the 2D geometric method (27%). By having three operators analyze a single set of image data, we found that the precision of the 3D tendon excursion method was much less affected by segmentation error than the 3D geometric method. With the 3D imaging methods, tendon bowstringing and a displacement of the joint center of rotation toward the dorsal side of the hand were evident, leading to as much as a 60% increase in moment arm with joint flexion. Because of the dependence on flexion and variation between subjects, we recommend patient-specific measurements for target applications in functional neuromuscular stimulation interventions and tendon transfer surgery. © 1999 Biomedical Engineering Society. PAC99: 8761Pk, 8719Rr, 0705Pj
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.180
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  • 145
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    Photochemistry of 9,10-Dicarbonyl-9,10-dihydroanthracene - A Source of 9,10-Dehydroanthracene? (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 57-60 
    Details
    ISSN: 1434-193X
    Keywords: Benzyne ; Dehydroanthracene ; Matrix isolation ; Photochemistry ; Bergman reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -9,10-Didehydroanthracene (1) is an interesting derivative of p-benzyne that has been subject of several studies. In contrast to an earlier report, the photochemical decarbonylation of 9,10-dicarbonyl-9,10-dihydroanthracene (2) does not lead to 1 but rather to the ring-opened ene-diyne 4. The key intermediate for this reaction is keto carbene 7 which is formed by monodecarbonylation of 2. Carbene 7 is labile towards visible-light irradiation and easily looses the second CO molecule to give 4. Carbene 7 and diyne 4 are characterized by IR and UV/Vis spectra, the IR spectra are compared to calculations at the B3LYP/6-31G(d,p) level of theory.
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  • 146
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    Reversal Diastereofacial Selectivity in the n-Butyllithium Addition to O-Protected N-Trimethylsilylimines of (2S)-Lactal: Enthalpic versus Entropic Contributions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 61-65 
    Details
    ISSN: 1434-193X
    Keywords: Nucleophilic addition ; Solvent effect ; Reversal of diastereoselectivity ; Temperature effect ; Imines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Commonly observed, but rarely explored, is the possibility of modifying the diastereomeric excess (de%) by means of temperature. A complete reversal in the diastereofacial selectivity could be obtained whenever the diastereoisomers concerned are differentially favored by enthalpy and entropy. The enthalpic or entropic dominance of a diastereoisomer depends greatly on the reaction solvent used.
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  • 147
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    Syntheses of Donor-Acceptor-Substituted 2,6-Stellanes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 73-81 
    Details
    ISSN: 1434-193X
    Keywords: Donor-acceptor systems ; Cage compounds ; Stelladione ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A number of condensations could be carried out using tricyclo[3.3.0.03,7]octane-2-one (stellanone, 4) and tricyclo[3.3.0.03,7]octane-2,6-dione (2,6-stelladione, 5) as starting materials. The components for condensations were 2-trimethylsilyl-1,3-dithiane (6), 1,1-bis(trimethylsilyl)-1H-cyclopropa[b]naphthalene (7), its 3,6-dimethoxy-substituted analogue 8, fluorene (12), xanthene (13), diethyl malonate (14), and malononitrile (15). The condensation reactions with 5 yielded mono- and disubstituted products, among them were the donor-acceptor-substituted 2,6-stellanes 33-35. The structures of 18 (prepared from stellanone and fluorene), 19, 24, 27, 31 and 32 (synthesized by condensation of 2,6-stelladione and 2-trimethylsilyl-1,3-dithiane and malononitrile, respectively) were determined by X-ray crystallography.
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  • 148
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    Synthesis of ω-Nitro Acids and ω-Amino Acids by Ring Cleavage of α-Nitrocycloalkanones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 87-90 
    Details
    ISSN: 1434-193X
    Keywords: Water ; α-Nitrocycloalkanones ; ω-Nitro acids ; Surfactant ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reaction of various α-nitrocycloalkanones 1 with aqueous 0.05 M NaOH, at 80 °C, in the presence of cetyltrimethylammonium chloride (CTACl) as a cationic surfactant, produces ω-nitro acids 2 in good yields. Reduction of the latter with HCOONH4/Pd-C, in methanol, at 80 °C affords ω-amino acids 3. The synthesis of methyl 9-oxodecanoate (8) is also reported.
    Additional Material: 2 Tab.
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  • 149
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    On the Selective O-Alkylation of Ambident Nucleophiles - The Synthesis of Thiohydroxamic Acid O-Esters by Phase-Transfer Reactions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 97-106 
    Details
    ISSN: 1434-193X
    Keywords: O-Alkylation ; Ambident nucleophile ; Thiazolethione ; Thiohydroxamic acid ; Phase-transfer reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -O-Alkylation of cyclic thiohydroxamic acids 1 and 3-5 has been studied with a view to developing an efficient method for the synthesis of N-(alkoxy)pyridine-2(1H)-thiones and N-(alkoxy)thiazole-2(3H)-thiones. Four issues have been addressed and the following conclusions can be drawn: (i) Thiones 1 and 5 exist as O-H acids in the solid state. (ii) According to NMR investigations (1H, 13C), the thione structures should be largely retained in CDCl3, [D6]DMSO, and CD3OD solutions of acids 1, 3-5, as is also the case for pyridinethione salts 2a-h. (iii) O-Alkylation of pyridinethione salts occurs in competition with S-alkylation. Selective O-alkylation is however possible, if thiohydroxamate salts with large countercations, such as M = NBu4, are treated with hard alkylating reagents in polar aprotic media. (iv) As tetrabutylammonium thiohydroxamates, such as 2f, are highly useful in the synthesis of cyclic thiohydroxamic acid O-esters, we have developed an efficient protocol for the preparation of N-(alkoxy)pyridine-2(1H)-thiones directly from acid 1 using phase-transfer conditions (alkyl halide or sulfonic acid ester, CH3CN, K2CO3, Bu4NHSO4). This method has proved particularly successful for the synthesis of N-(alkoxy)thiazole-2(3H)-thiones 11, 20-28, which were obtained in yields of up to 87%.
    Additional Material: 2 Ill.
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  • 150
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    Palladium(0)-Catalyzed Asymmetric Synthesis of 1,2,3,4-Tetrahydro-2-vinylquinoxalines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 129-134 
    Details
    ISSN: 1434-193X
    Keywords: Tetrahydro-2-vinylquinoxaline ; Cyclization ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Reaction of (Z)-1,2-bis(methoxycarbonyloxy)but-2-ene (2) with various N,N-bis(arylsulfonyl)-o-phenylenediamines 1 was catalyzed by a palladium complex associated with chiral ligands to give optically active 1,4-bis(arylsulfonyl)-1,2,3,4-tetrahydro-2-vinylquinoxalines 3 with up to 62% ee. The use of (S)-MeOBIPHEP as the chiral ligand and N,N-bis(p-tolylsulfonyl)-o-phenylenediamine (1i) as the nucleophile led to the highest ee at 25 °C, regardless of the solvent used. The enantioselectivity of the cyclization is strongly affected by the nature of the substituents at the nitrogen atom.
    Additional Material: 4 Tab.
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  • 151
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    Stereoselective Synthesis of Enantiomerically Pure β-Fluoroalkyl γ-Butyrolactones by Sulfoxide-Directed Lactonization (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 111-115 
    Details
    ISSN: 1434-193X
    Keywords: Fluorine ; Lactones ; Annulation ; Ketene ; Sulfoxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Enantiomerically pure α,α-dichloro β-fluoroalkyl γ-p-tolylthio γ-butyrolactones trans-6a-c have been obtained with excellent stereocontrol (〉 98:2) and enantiomeric purity (〉 98:2) by sulfoxide-directed lactonization (Marino's annu-lation reaction) of β-fluoroalkyl vinyl sulfoxides (R)-(E)-5a-c with dichloroketene. Highly chemoselective dechlorination and desulfurization reactions performed on trans-6c efficiently provided the β-chlorodifluoromethyl γ-butyrolactone (S)-8c, the absolute stereochemistry of which was determined by X-ray diffraction analysis of its γ-p-tolylthio precursor (2R,3S)-7c.
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  • 152
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    Reaction of Nitrosobenzene with 4-Methoxy-N-methyleneaniline (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 141-143 
    Details
    ISSN: 1434-193X
    Keywords: Nitrosobenzene ; 4-Methoxy-N-methyleneaniline ; 1,3,5-Tris(4-methoxyphenyl)-1,3,5-triazinane ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A 1:1 adduct produced in the reaction of nitrosobenzene (2) with 1,3,5-tris(4-methoxyphenyl)-1,3,5-triazinane (3) has been shown by X-ray diffraction structure analysis to be the N′-(4-methoxyphenyl)-N-phenyl-N-oxyformamidinium species 5.
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  • 153
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    A New Diastereoselective Synthesis of anti-α-Alkyl α-Hydroxy β-Amino Acids (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 155-161 
    Details
    ISSN: 1434-193X
    Keywords: Alkylation ; Oxazolines ; anti-α-Alkyl α-hydroxy β-amino acids ; Lithium dianion ; Penicillin G acylase ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -As part of an ongoing project concerning the synthesis of enantiomerically pure α-hydroxy β-amino acids, we have now developed a general strategy allowing the synthesis of anti-α-alkyl α-hydroxy β-amino acids. Our procedure involves the intermediate formation of trans-oxazolines, which are alkylated at C-5 with good to high diastereoselectivity and then hydrolysed under mildly acidic conditions, affording in quantitative yield the corresponding hydroxy amides. The starting (R)-3-amino-3-phenylpropanoic acid and (S)-3-aminobutanoic acid were obtained in enantiomerically pure form by selective enzymatic hydrolysis of the corresponding phenylacetylamides with penicillin G acylase.
    Additional Material: 3 Ill.
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  • 154
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    Palladium(0)-Catalyzed Reaction of Acidic Anilines with (Z)-2-Butene-1,4-diyl Dicarbonate - Preparation of N-Aryl-4-vinyloxazolidin-2-ones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 181-186 
    Details
    ISSN: 1434-193X
    Keywords: Palladium catalysis ; Homogeneous catalysis ; Anilines ; Alkylation ; Oxazolidinones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Palladium-catalyzed reaction of acidic anilines with (Z)-2-butene-1,4-diyl dicarbonate affords N-aryl-4-vinyloxazolidin-2-ones. The success of the reaction depends on the acidity of the aniline and requires in situ conversion of the dicarbonate into carbamate carbonate by nucleophilic attack of the aniline conjugate base followed by palladium-catalyzed intramolecular cyclization.
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  • 155
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    Substituent Effects on the Vinylcyclopropane-Cyclopentene Rearrangement - A Theoretical Study by Restricted and Unrestricted Density Functional Theory (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 215-220 
    Details
    ISSN: 1434-193X
    Keywords: Density functional calculations ; Vinylcyclopropane-cyclopentene rearrangement ; [1,3]-Sigmatropic shift ; Biradical-like transition structure ; Substituent effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The effect of donor substitution by the hydroxy group and of acceptor substitution by the cyano group on the activation energies of the vinylcyclopropane-cyclopentene rearrangement was calculated by the spin-restricted RB3LYP/6-31G* method for reactant structures and by the spin-unrestricted UB3LYP/6-31G* method for transition structures. The activation energies of the rearrangement of hydroxy- and cyano-substituted vinylcyclopropanes are very similar for substitution in the same position. In agreement with earlier findings the substituent effects on the activation energies are closely connected with the radical stabilizing properties of the substituents. As indicated by singlet/triplet splitting energies, the transition structures are essentially biradicaloid. In spite of spin pairing in the transition structure the substituent effects on bond lengths and on stabilization energies are very similar to those of the free radicals corresponding to the two radical substructures. Thus, the transition structures may be considered, in good approximation, as structures consisting of two weakly interacting radicals.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98349_s.pdf or from the author.
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  • 156
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    Syntheses and Reactions of 1-Amino-2,2-dialkylcyclopropane-1-carbonitriles and -carboxamides - Potential Precursors of ACC Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 239-250 
    Details
    ISSN: 1434-193X
    Keywords: Cyclopropanes ; Rearrangements ; Cyanohydrins ; Schiff bases ; Small ring systems ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The direct cyclization of 2-amino-4-chloro-3,3-dimethylbutanenitrile with potassium tert-butoxide in THF afforded 1-amino-2,2-dimethylcyclopropane-1-carbonitrile and a dimerization product. Various new cis- and trans-1-(tert-butylamino)-2-benzyl-2-methylcyclopropane-carbonitriles and© the corresponding cyclopropanecarboxamides have been synthesized, with focus on the isolation of the pure stereoisomeric cyclopropanecarboxamides. The relative configuration of the stereoisomers was established by X-ray crystallographic analysis of one of the model compounds. A new route to the latter functionalized cyclopropanes was developed by reaction of 1-methoxycyclopropylamines with potassium cyanide. Some remarkable rearrangements of 1-aminocyclopropane-1-carbonitriles into azetidine and oxazine derivatives via Favorskii-derived intermediates are reported. Various aspects of the chemistry of geminally functionalized cyclopropanes are discussed.
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  • 157
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    Regio- and Stereoselective Synthesis of Vinylallenes by 1,5-(SN′′)-Substitution of Enyne Acetates and Oxiranes with Organocuprates (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 267-275 
    Details
    ISSN: 1434-193X
    Keywords: Vinylallenes ; Organocuprates ; Substitution ; Stereoselective synthesis ; Copper catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Enyne acetates 2, 4, 6, and 8, as well as enyne oxiranes 10, with different substitution patterns react with organocuprates regioselectively under 1,5-(SN2′′)-substitution to provide vinylallenes 11 and 12. With lithium dimethylcuprate, reduced vinylallenes originating from a (formal) transfer of a hydride ion to the substrate are formed in some cases. The products are usually obtained as mixtures of (E/Z)isomers; however, pure (E)-vinylallenes are formed occasionally. The 1,5-substitutions can also be carried out with catalytic amounts of copper reagents. The reaction of chiral enyne acetate (S)-2a with tBu2CuLi · LiCN proceeds enantioselectively, so that this transformation constitutes a new case of remote stereocontrol.
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    Reactions of the Hydrofluoroborate Salts of Open-Chain Analogues of Reissert Compounds with Some α,β-Ethylenic Esters (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 297-303 
    Details
    ISSN: 1434-193X
    Keywords: Nitrogen heterocycles ; Open-chain analogue of Reissert compound ; Hydrofluoroborate salts ; α,β-Ethylenic esters ; 1,3-Dipolar cycloaddition ; Azomethine ylide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reaction of the hydrofluoroborate salt of an open-chain analogue of a Reissert compound with some α,β-ethylenic esters does not give a [4 + 2] cycloadduct, as previously described in the case of ethyl acrylate. The reaction starts with a 1,3-dipolar cycloaddition of a münchnone imine 5c, d. The [3 + 2] cycloadducts 13 evolve via a rearrangement-condensation sequence to give a substituted 2-pyridone derivative 18 or 19. The proposed mechanism has been verified by the isolation and structural X-ray analysis of some compounds of the reaction sequence.
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  • 159
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    EPC-Synthesis of β-Amino Acid Derivatives through Lithiated Hydropyrimidines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 335-360 
    Details
    ISSN: 1434-193X
    Keywords: 2-tert-Butylhydropyrimidinones ; 3-Aminocarboxylic acid derivatives ; Cyclic imino esters ; Lithium enaminates ; Alkylations ; β-Amino acids ; Asymmetric synthesis ; Kinetic resolution ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Racemic and enantiopure 2-tert-butyltetrahydropyrimidinones (from pivalaldehyde and 3-aminocarboxylic acids) are converted to Alloc-, Boc-, and Z-protected cyclic imino esters (7-10, Schemes 2-4). These are deprotonated to Li enaminates (K, L). Reactions with electrophiles (prim., sec. alkyl, allyl, benzyl, propargyl halides, aldehydes, imines, enoates) give good yields and are highly diastereoselective (products 11-42, Schemes 5-10). A two-step cleavage (removal of protecting group and hydrolysis) under very mild conditions converts the heterocyclic products to α-branched β-amino acid methyl esters (43-61, Schemes 11-13). The structure of the products is determined by NMR spectroscopy (Figure 1), by chemical correlation (Scheme 14), and by X-ray analysis (Figure 2, 3, 7, Table 1). A structure of the Li enaminates is proposed (Figure 4). Mechanistic models are derived for the reactions occurring with formation of two stereogenic centers with relative topicity like (Figures 5, 6).
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  • 160
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    A Unified Synthetic Strategy for the Indolopyridine Alkaloid Group (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 373-378 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cross-coupling ; N-Heterocycles ; Palladium ; Synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Thermal or acetyl chloride induced cyclization of bromoenamide 10 affords the pentacyclic derivative 12 with high yield and regioselectivity. From this common synthetic intermediate, palladium-catalyzed reactions allow the total synthesis of indolopyridine alkaloids 1-6.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98332_s.pdf or from the author.
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    Conformational Preferences of Peptides Containing Reverse-Turn Mimetic Bicyclic Lactams: Inverse γ-Turns versus Type-II′ β-Turns - Insights into β-Hairpin Stability (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 389-400 
    Details
    ISSN: 1434-193X
    Keywords: Reverse-turn mimics ; γ-Turns ; β-Turns ; β-Hairpins ; NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The solid-phase synthesis and characterization of a series of peptides (3-9), containing reverse-turn mimetic bicyclic lactams (1a, 1b), was reported in the preceding paper. The bicyclic lactams (1a, 1b) possess high structural similarity to the two central residues of a β-turn. The conformational preferences of the constrained peptides have been investigated by NMR spectroscopy and IR spectroscopy. Our experimental results have been complemented by computer modelling studies and show that the constrained peptides (3-9) form an inverse γ-turn or a type-II′ β-turn through intramolecular hydrogen bonding, depending on the nature of the reverse-turn mimic. In N-acetylated tetrapeptide mimics incorporating the two different bicyclic lactams (a series and b series), H5 is available for either a γ-turn (7-membered ring with the carbonyl group of the bicyclic lactam) or a β-turn (10-membered ring with the carbonyl group of residue 2), as shown in Figures 7 and 9. The a series incorporating the (5,7)-bicyclic lactam predominantly induces the γ-turn conformation, while the b series incorporating the (5,6)-bicyclic lactam can promote either a γ-turn or a β-turn conformation, with the β-turn usually being preferred and with varying degrees of β-hairpin formation.
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  • 162
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    Deprotonation of Oxazolinyloxiranes: Formation of Substituted Acyloxiranes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 409-417 
    Details
    ISSN: 1434-193X
    Keywords: Deprotonation ; Oxiranyloxazolines ; Oxazolinyloxiranyllithium compounds ; Oxazolidines ; Acyloxiranes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Deprotonation of oxazolinyloxiranes 1a, 1h, and 1k with sBuLi/TMEDA at -100 °C in Et2O furnishes oxazolinyloxiranyllithium compounds[1]1b, 1i, and 1l which are stable at low temperature and can be trapped with electrophiles to give substituted oxiranes 1c-1g and 1j. The reaction of 1b with aldehydes produced diastereomers syn (2a-d) and anti (3a-d). Oxiranyllithium 1i from trans-1-(4,4-dimethyl-2-oxazolinyl)-2-p-tolylepoxyethane (1h) was found to be configurationally stable while oxiranyllithium 1l, generated from the cis isomer 1k, was not. Oxazolinylepoxides 1d, 1j, and 1m could be deblocked to acyloxiranes 5a-e through oxazolidines 4a-e.
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  • 163
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    N-Substituted 1-Aminoindoles from Electrogenerated N-Substituted 2-(ortho-Nitrosophenyl)ethylamines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 419-430 
    Details
    ISSN: 1434-193X
    Keywords: Electrochemistry ; Electrosynthesis ; Nitrosobenzenes ; Nitrogen heterocycles ; 1-Aminoindoles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -An electrochemical methodology offering efficient access to N-alkyl- and N-aryl-substituted 1-aminoindoles has been developed. N-Substituted 2-(ortho-nitrosophenyl)ethylamines, electrogenerated in a “redox” flow cell, undergo intramolecular cyclization to hydrocinnoline-type intermediates. Under slightly basic conditions, these undergo spontaneous ring-contraction to produce the N-substituted heterocycles in good yields. The reactions have been studied in slightly acidic and slightly basic aqueous alcoholic media.
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  • 164
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    Synthesis of Enantiopure β- and γ-Amino Alcohols from Homochiral α- and β-Aminoacylsilanes as Stable Synthetic Equivalents of α- and β-Amino Aldehydes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 437-445 
    Details
    ISSN: 1434-193X
    Keywords: Aminoacylsilanes ; Amino aldehydes ; Amino alcohols ; Allylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A practical route is described for the synthesis of enantiopure β- and γ-amino alcohols with two stereocenters, starting from homochiral α- (1 and 5) and β- (13 and 16) -aminoacylsilanes, and involving stereoselective addition of allylmetal compounds and subsequent stereospecific protiodesilylation of the adducts. The degree of diastereoselectivity achieved in the nucleophilic addition step depends on both the nitrogen-protecting group and the reagents used. Diastereomeric excess (de) values equal to or higher than 98% were obtained in the TiCl4-promoted allylation of the N-Pht-aminoacylsilanes 1 and 13 and of the N-Ts-aminoacylsilane 5 with allyltrimethylsilane. Lower de values were obtained in the Sc(OTf)3-catalyzed allylation of 5 with tetraallyltin and in the additions of both allyltrimethylsilane and tetraallyltin to the N-Ts-β-aminoacylsilane 16. Protiodesilylation of the adducts, leading to the β- and γ-amino alcohols, was accomplished with TBAF, except in the case of the adducts obtained from 5. For these, a preliminary removal of the tosyl group was necessary, which was accomplished with simultaneous desilylation by treatment with Na in liquid ammonia.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98342_s.pdf or from the author.
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    Diastereoselective Intramolecular meta Photocycloaddition of Side-Chain-Substituted 5-(2-Methoxyphenyl)pent-1-enes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 463-470 
    Details
    ISSN: 1434-193X
    Keywords: meta Photocycloaddition ; Photochemistry ; Steric hindrance ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Irradiation of a series of 5-(2-methoxyphenyl)pent-1-enes substituted with a hydroxy or trimethylsilyloxy group at the α-, β-, or γ-position of the side-chain yields in all cases meta photocycloadducts, in which the configuration at the substituted carbon atom is mainly endo. This indicates that the diastereoselectivity originates from minimization of steric interactions between the side-chain substituent and the ortho-methoxy group at the arene unit. Hydrogen bonding does not seem to be involved. The introduction of the side-chain substituents also influences the regioselectivity of the addition: The linear to angular adduct ratios are significantly increased compared to the case of the parent compound.
    Additional Material: 3 Tab.
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  • 166
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    5-Aza-7-deaza-2′-deoxyguanosine: Oligonucleotide Duplexes with Novel Base Pairs, Parallel Chain Orientation and Protonation Sites in the Core of a Double Helix (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 485-496 
    Details
    ISSN: 1434-193X
    Keywords: 5-Aza-7-deaza-2′-deoxyguanosine ; Oligonucleotides ; Parallel DNA ; Protonated base pairs ; Tm values ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Oligonucleotides containing 5-aza-7-deaza-2′-deoxyguanosine (1) were synthesized. Solid-phase synthesis was performed with the phosphonate 15 or the phosphoramidite 5. The amino-unprotected phosphonate 4 was also employed. Hybridization studies of oligonucleotides containing 1 resulted in new base pairs leading to duplexes with parallel (ps) or antiparallel (aps) chain orientation. Among those with parallel chains a stable “purine-purine” base pair was observed between 5-aza-7-deazaguanine and guanine or 7-deazaguanine. Antiparallel stranded duplexes are formed when 5-aza-7-deazaguanine pairs with cytosine. This base pair has only two hydrogen bonds under neutral conditions but is stabilized by a third one in acidic medium. A new base pair is also detected between the base of 1 and isoguanine (neutral medium).
    Additional Material: 1 Ill.
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  • 167
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    Polar and Steric Substituent Effects in 5-exo-trig Cyclizations of 1-Aryl-4-penten-1-oxyl Radicals (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 523-523 
    Details
    ISSN: 1434-193X
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -By mistake wrong concentrations were given in the footnote of Table 1 and in the Discussion. Instead of c0 = 1.2 M read c0 = 0.12 M if 2-naphthalenethiol was used as hydrogen donor and instead of c0 = 1.8 M read c0 = 0.18 M if Bu3SnH was used to trap photoproducts. In Table 2 relative rate constants of radical 2d refer to radical 2e and vice versa as correctly stated in the Discussion. In the Experimental Section (Iodocyclization) read 2.25 g (8.86 mmol) of iodine instead of 2.25 g (1.10 mmol) of iodine.
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  • 168
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    Arylboron Compounds as Acid Catalysts in Organic Synthetic Transformations (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 527-538 
    Details
    ISSN: 1434-193X
    Keywords: Tris(pentafluorophenyl)borane ; Diarylborinic acid ; Arylboronic acid ; Chiral arylboron catalyst ; Lewis acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Arylboron compounds, ArnB(OH)3-n (n = 1-3), bearing electron-withdrawing aromatic groups such as triarylboranes, diarylborinic acids, and arylboronic acids represent a new class of air-stable and water-tolerant Lewis acid or Brønsted acid catalysts in organic synthesis. In particular, while tris(pentafluorophenyl)borane has primarily been used as a co-catalyst in metallocene-mediated olefin polymerization, its potential as a Lewis acid catalyst for organic transformation is now much more extensive. Diarylborinic acids and arylboronic acids have shown themselves to be powerful tools in the design of chiral boron catalysts. This article provides a comprehensive summary of the organic transformations catalyzed by arylboron compounds as acids.
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  • 169
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    2D-NMR-Guided Constitutional Analysis of Organic Compounds Employing the Computer Program COCON[#] (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 573-577 
    Details
    ISSN: 1434-193X
    Keywords: Structure elucidation ; Constitutional analysis ; Natural products ; HMBC ; Computational chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The computer program COCON is introduced as a tool for the comprehensive structure elucidation of unknown organic compounds. In particular, structural proposals made on the basis of the molecular formula and of 2D-NMR experiments can be analyzed for the existence of alternative constitutions being in agreement with the same data set. The computational speed grounds on the evaluation of ambiguous long-range connectivity information during the process of structure generation. The data set experimentally obtained for the marine natural product oroidin (1) was selected, because proton-poor compounds usually cause uncertainties in NMR-based structure determinations. The calculation results encourage to move from the experience-based analysis of NMR chemical shifts or of MS fragmentations to the automated evaluation of routinely available connectivity information.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98241_s.pdf or from the author.
    Additional Material: 6 Ill.
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  • 170
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    3,5-Dimesityl-1,2,4-oxadiphosphole - Synthesis and Reactivity of a Novel Heterocycle (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 587-595 
    Details
    ISSN: 1434-193X
    Keywords: Phosphaalkenes ; Heterodiphospholes ; Cycloadditions ; Phosphaalkyne cyclooligomers ; Phosphorus-carbon cage compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The first synthesis of a 1,2,4-oxadiphosphole 6 has been achieved by vacuum thermolysis of mesitylphosphaalkene 5. The novel heterocycle 6 exhibits an enormous potential for cycloaddition reactions, which predominantly proceed selectively at low temperatures. Compound 6 undergoes addition with two equivalents of phosphaalkynes 10 by a [4+2] cycloaddition/homo Diels-Alder reaction sequence to form novel oxatetraphosphadeltacyclenes 12 and 13. Tetrachloro-o-benzoquinone (14) undergoes a selective [4+1] cycloaddition with 12 and 13 leading to the spirocyclic products 15 and 16 containing λ5-phosphorus atoms. Treatment of the oxadiphosphole 6 with dimethyl acetylenedicarboxylate (17) provides the first access to a 1,2-oxaphosphole 18, which is formed after an initial [4+2] cycloaddition followed by a retro Diels-Alder reaction. An unexpected reaction of 6 is observed with tri-tert-butylazete (20) furnishing a new polycyclic system (→ 21).
    Additional Material: 4 Ill.
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  • 171
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    Synthesis of 1β-Methylcarbapenem Antibiotic Precursors by Cyclization Using π-Allylpalladium Complexes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 621-626 
    Details
    ISSN: 1434-193X
    Keywords: 1β-Methylcarbapenems ; Palladium ; Ruthenium ; Catalysis ; Cyclizations ; Stereoselective hydrogenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -An efficient diastereoselective multi-step synthesis of bicyclic 1β-methylcarbapenem antibiotic precursors has been developed, starting from the commercially available 4-acetoxyazetidin-2-one 4. Chiral ruthenium catalysts are used in the hydrogenation step to control the β-stereochemistry at the 1-position, and a π-allylpalladium ring-closure strategy is used to form the functionalized carbapenem skeleton.
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  • 172
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    Oligo-2,6-naphthylenevinylenes - New Building Blocks for the Preparation of Photoluminescent Polymeric Materials (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 643-651 
    Details
    ISSN: 1434-193X
    Keywords: Oligomers ; Synthesis design ; Substituent effects ; Luminescence ; Cyclic voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Synthetic strategies towards appropriate symmetric and unsymmetric functionalization of the naphthalene ring are presented. By means of Knoevenagel and Wittig condensation reactions new fluorescent, differently functionalized oligo(2,6-naphthylenevinylene)s have been synthesized, the presence of terminal aldehyde or bromine substitution opening the way to the incorporation of the fluorescent trimers in a variety of polymeric materials. The effect of substituting the phenylene ring by the more bulky dialkoxynaphthalene system in arylenevinylene-type materials is studied from the structural point of view and the possibility to tune the emission color and the electron affinity through the introduction of naphthylenevinylene and cyano-substituted naphthylenevinylene units is also investigated.
    Additional Material: 4 Ill.
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  • 173
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    New Type of Skipped Oligoaziridines: Synthesis of New Fatty AcidDerivatives Containing Aziridine Functions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 661-664 
    Details
    ISSN: 1434-193X
    Keywords: Aziridines ; N-Heterocycles ; Fatty acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The first successful preparation of the aziridines methyl cis-9,10;cis-12,13-diepiminooctadecanoate (3) derived from linoleic acid, and methyl cis-9,10;cis-12,13;cis-15,16-triepiminooctadecanoate (6) derived from linolenic acid, is reported. Remarkably, the bis- and trisaziridine were obtained in a reaction sequence that consists of only two steps, using technically pure methyl esters of epoxidized sunflower and linseed oil. The conversion of methyl 9,10;12,13-diepoxyoctadecanoate (1), with sodium azide and ammonium chloride in ethanol in the presence of water, yielded the new diazidodihydroxy compound methyl 9(10),12(13)-diazido-10(9),13(12)-dihydroxyoctadecanoate (2) in the first step. 2 was obtained as a regioisomeric mixture. The reaction of 2 with triphenylphosphane led to the bisaziridine 3. The analogous conversion of methyl 9,10;12,13;15,16-triepoxyoctadecanoate (4), via the new triazidotrihydroxy compound methyl 9(10),12(13),15(16)-triazido-10(9),13(12),16(15)-trihydroxyoctadecanoate (5), afforded trisaziridine 6.
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  • 174
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    Novel Ligands for the Separation of Trivalent Lanthanides and Actinides - Tetrakis(phosphane sulfide) and -(phosphinic acid) Cavitands (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 665-674 
    Details
    ISSN: 1434-193X
    Keywords: Cavitands ; Nuclear waste ; Actinide/lanthanide separation ; Solvent extraction ; Sulfur atoms ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Cavitands with phosphane sulfide moieties 4 and 8a,b were prepared in good yields from their phosphane oxide analogues, as more stable alternatives for the dithiophosphinic acids used at present. The cavitands 7a and 7b with flexible butoxyphosphane oxide ligating sites are more efficient than cavitand 3 having rigid methylphosphane oxide groups as was studied with EuIII picrate extractions. Due to the absence of an ionic functionality in the phosphane sulfides 4 and 8a,b AmIII and EuIII are not extracted, not even in the presence of synergents (e.g. TBP, TOPO, HDNNS). Cavitand 10 with phosphinic acid groups efficiently extracts EuIII in 1:1 or 2:1 complexes, depending on the metal-to-ligand concentration ratio (extraction constants Kex1 = 3.9·10-5M2 and Kex2 = 1.9·102M, respectively). Furthermore, in the case of 10 EuIII is preferentially extracted over AmIII with a separation factor SEu/Am up to 5.
    Additional Material: 5 Ill.
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  • 175
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    Preparation of 2,3,5-Tri-O-benzyl-4-thio-L-arabino-furanosides and the Corresponding 4′-Thionucleoside Analogues (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 691-696 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; 4-Thiofuranosides ; Nucleosides ; Reaction mechanisms ; NOE measurements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -1-O-Acetyl-2,3,5-tri-O-benzyl-4-thio-L-arabino-furanose (9) has been prepared from D-xylose via the 1,4-dithio-L-arabino-furanoside 8. The crucial step of the reaction, i.e. the intramolecular cyclization of the open-chain dithioacetal 5, has been achieved in a yield of 90% by applying tetrabutylammonium iodide as promoter. Reaction of 9 with bis(trimethylsilyl)uracil or -thymine led to the benzyl derivatives 12 and 13 from which the deprotected 4′-thionucleoside analogues 14 and 15 have been prepared by debenzylation with boron tribromide.
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  • 176
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    100 Years of Baeyer-Villiger Oxidations (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 737-750 
    Details
    ISSN: 1434-193X
    Keywords: Baeyer-Villiger oxidation ; Ketones ; Monopersulfate ; Peracids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -In the present review, we report the discovery of the formation of esters and lactones by oxidation of ketones with a peroxide derivative, namely the Baeyer-Villiger reaction. This reaction was first reported by Adolf von Baeyer and Victor Villiger a century ago in 1899, just one year after the oxidant they used (KHSO5) has been described. Furthermore, Baeyer and Villiger established the composition of this new inorganic peroxide and showed that its instability was the reason of a controversy between several European chemists between 1878 and 1893. For the first 50 years the mechanism of the Baeyer-Villiger reaction was a matter of debate. A side product, 1,2,4,5-tetraoxocyclohexane, was ruled out as an intermediate in the ester formation by Dilthey. Criegee postulated a nucleophilic attack of the oxidant on the carbonyl group. This mechanism was confirmed by von E. Doering by a labeling experiment with [18O]benzophenone. The rearrangement step occurs with retention of the stereochemistry at the migrating center. The competitive migration and the rate-determining step are also discussed in this review.
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  • 177
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    Transferase Activity of a β-Glycosidase from Thermus thermophilus: Specificities and Limits - Application to the Synthesis of β-[1→3]-Disaccharides (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 757-763 
    Details
    ISSN: 1434-193X
    Keywords: Transglycosylation ; Glycosidases ; Thermus thermophilus ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The aim of this paper is to test the ability of a β-glycosidase from Thermus thermophilus to catalyse transglycosylation reactions in the presence of nitrophenyl glycosides as donors and other monosaccharides as acceptors. Our results show that this enzyme is able to induce such reactions either with nitrophenylgalactosides, -glucosides and -fucosides. With the two former donors, the autocondensation of the donor, which thus acts also as an acceptor, is faster than the transglycosylation with other acceptors. Furthermore, as the regioselectivity of the reactions is mainly of the β-[1→3] type, good yields are obtained for the synthesis of 2-nitrophenyl-β-D-galactopyranosyl-[1→3]-β-D-galactopyranoside and 2-nitrophenyl-β-D-glucopyranosyl-[1→3]-β-D-glucopyranoside. Conversely, in the presence of p-nitrophenylfucoside, the autocondensation is very limited, and with methyl-α-D-galactoside as an acceptor, the regioselectivity is mainly of the β-[1→6]-type resulting in the synthesis of methyl-β-D-fucopyranosyl-[1→6]-α-D-galactopyranoside.
    Additional Material: 7 Ill.
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  • 178
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    Reduction of Acetylenic Compounds to (E)-Olefins by Alkali Metals - An Investigation of the Scope (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 775-779 
    Details
    ISSN: 1434-193X
    Keywords: Monoynes ; Polyynes ; Alkali metals ; Liquid NH3 ; Hexamethylphosphoric triamide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Efficient procedures have been developed for the stereospecific reduction by alkali metals of disubstituted acetylenes with long carbon chains. Acetylenes containing two or more (isolated) triple bonds are reduced considerably more easily than are monoynes.
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    Synthesis of Enantiopure o-Hydroxybenzylamines by Stereoselective Reduction of 2-Imidoylphenols: Application in the Catalytic Enantioselective Addition of Diethylzinc to Aldehydes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 805-811 
    Details
    ISSN: 1434-193X
    Keywords: Aminophenols /Asymmetric synthesis ; C-C coupling ; Reductions ; Conformation analysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Enantiopure o-hydroxybenzylamines 2a-i were synthesized by diastereoselective reduction of the 2-imidoylphenols (R)-1a-i. Conformational analysis enabled the assignment of the absolute configurations of compounds 2a-i. The accessible o-hydroxybenzylamine (R,R)-2h serves as an effective catalyst precursor for highly enantioselective addition of diethylzinc to aliphatic and aromatic aldehydes. This pathway represents a practical and operationally very simple methodology for the enantioselective synthesis of both the enantiomers of secondary alcohols 7a-f.
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  • 180
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    Cyclialkylation of Arylalkyl Epoxides with Solid Acid Catalysts (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 837-846 
    Details
    ISSN: 1434-193X
    Keywords: Friedel-Crafts reaction ; Hydroxyalkylation ; Aromatics ; Epoxides ; Zeolites ; Clays ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Solid acids, such as zeolites and clays, catalyse the intramolecular hydroxyalkylation (cyclialkylation) of several arylalkyl epoxides in moderate to excellent conversions and selectivities. The use of solid acids in these cyclialkylations provides a cleaner, better alternative to conventional Lewis and Brønsted acids, enabling a more facile workup of reaction mixtures and, in several cases, better selectivities.
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  • 181
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    Phosphorylating Power of Red Phosphorus towards Aldehydes in Basic and in Acidic Media (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 861-868 
    Details
    ISSN: 1434-193X
    Keywords: Red phosphorus ; Phosphane PH3 ; Phosphorylations ; Ultrasound irradiation ; Redox chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reactivity of red phosphorus towards aldehydes was investigated under basic and acidic media. It was demonstrated that the real phosphorylating agent involved in the reaction was phosphane (PH3) in basic media, and hypophosphorous acid (H3PO2) in acidic media. A convenient one-pot synthesis of (α-hydroxyalkyl)phosphinic acids from red phosphorus and aldehydes in basic media was realized under sonication. The same reaction under acidic media in the presence of hydriodic acid led to the corresponding phosphonic acids. The (α-hydroxyalkyl)phosphinic acids were readily prepared under sonication from hypophosphorous acid and aldehydes in the presence of catalytic amounts of hydrochloric acid. The mechanism of the addition reaction of PH3 to benzaldehyde was elucidated and shows the complexity of the reaction as a function of the experimental conditions.
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    A New Approach to Erythrinanes through Pummerer-Type Cyclization (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 909-915 
    Details
    ISSN: 1434-193X
    Keywords: Erythrina alkaloids ; Nitrogen heterocycles ; Nitro aldol reaction ; Michael addition ; Pummerer reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A successful new strategy for the synthesis of erythrinanes is reported. (Nitromethyl)arene derivative 16 was condensed with aldehyde 17 to give nitro aldol 19. After removal of the hydroxy group, the subunits 26a,b, containing the erythrinane rings A and D, were formed by intramolecular Michael addition. Reduction of the nitro function, followed by cyclization of the resulting amino group with the appended acetate group afforded the bicyclic lactams 29a,b, bearing an angular aryl group. Two-carbon elongation at the nitrogen atoms of 29a and 29b by means of hetero Michael addition of methyl phenyl sulfoxide, followed by Pummerer-type cyclization, gave cis- and trans-11-phenylthioerythrinan-8-ones 35a and 35b, respectively. Reductive desulfurization at C-11 furnished the desired erythrinan-8-ones 39a and 39b in 8 steps from 16.
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    Synthesis, X-ray Structure Analysis and Topochemical Photopolymerization of Substituted 1,6-Bis(2,5-dimethoxyphenyl)hexa-2,4-diynes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 917-922 
    Details
    ISSN: 1434-193X
    Keywords: Crystal engineering ; Diynes ; Photochemistry ; Solid-state chemistry ; Polymers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The 1,6-bis(2,5-dimethoxyphenyl)hexa-2,4-diynes 4a-c were obtained from the corresponding 2,5-dimethoxybenzenes 1 by bromination followed by a copper-catalyzed Grignard reaction with 3-bromoprop-1-yne. Catalyzed coupling of the resulting 3-(2,5-dimethoxyphenyl)prop-1-ynes 3 under Hay conditions gave the hexa-2,4-diynes 4a-c in good yields. The molecular structures of the diynes 4a and 4b were determined by X-ray diffraction analysis. In each crystal structure, an unusual 1,6-synperiplanar conformation of the hexa-2,4-diyne unit is observed, with the 1,6-diphenyl substituents arranged in a coplanar orientation. According to the crystal structure data obtained, irradiation of diynes 4a and 4b afforded the deeply-colored, highly-ordered polymers 5a and 5b under topochemical control. Oxidation of 4a and 4b with cerium(IV) ammonium nitrate gave the corresponding 1,6-bis(2,5-dimethoxyphenyl)hexa-2,4-diyne-1,6-diones 6a and 6b.
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    Synthesis of Acyclic Carba-Nucleoside Phosphonates, Structural Analogues to Natural Deoxyribonucleotides (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 931-936 
    Details
    ISSN: 1434-193X
    Keywords: Nucleosides ; Phosphonates ; Nucleophilic additions ; C-C coupling ; Reduction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Acyclic carba-nucleoside phosphonates, modelled on natural deoxyribonucleotides have been prepared starting from DNA nucleobases and tert-butyl acrylate. The products obtained from a Michael-type reaction were elongated to β-oxo esters that were first reduced to β-hydroxy esters and then transformed into protected β-hydroxy aldehydes. Wittig-Horner-Emmons reaction with the anion of tetraisopropyl methylenebisphosphonate gave, after deprotection, the desired 4-hydroxy-6-purinyl- or -6-pyrimidinyl-1-hexenylphosphonic acids. A dimer, potential precursor of acyclic polynucleotides (APN), homomorphous with DNA, was also prepared.
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    Electrochemically Induced N-Alkylation of Pyrroles (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 955-958 
    Details
    ISSN: 1434-193X
    Keywords: Tetraethylammonium peroxydicarbonate ; Tetraethylammonium carbonate ; N-alkylated pyrroles ; Electrochemistry ; Electrogenerated bases ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Electrochemically generated tetraethylammonium peroxydicarbonate (TEAPC) and tetraethylammonium carbonate (TEAC) react under very mild conditions with pyrroles affording, after addition of a suitable alkylating agent, the corresponding N-alkylated pyrroles in high yields. C-Alkylated pyrroles have not been isolated in any case reported.
    Additional Material: 2 Ill.
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  • 186
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    Simple Synthesis of (±)-Stigmolone (8-Hydroxy-2,5,8-trimethyl-4-nonanone), the Pheromone of Stigmatella aurantiaca (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 979-980 
    Details
    ISSN: 1434-193X
    Keywords: Ketones ; Myxobacterium ; Pheromones ; Stigmatellaaurantiaca ; Stigmolone ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The racemic myxobacterial pheromone (±)-1 (stigmolone), which induces the formation of the fruiting body of Stigmatellaaurantiaca, was synthesized from methyl isobutyl ketone (2) in 48% overall yield in four steps
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  • 187
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    Electronic Resource
    Photochemical Hydrogen Migration in Methylanthronylidenes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1005-1009 
    Details
    ISSN: 1434-193X
    Keywords: Hydrogen migration ; Anthronylidene ; Quinone methide ; Matrix isolation ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The photochemistry of 4-methyl-9,10-diazoanthrone (7a) and 1,4-dimethyl-9,10-diazoanthrone (7b) was investigated in argon matrices at 10 K. Visible-light irradiation results in the formation of the anthronylidenes 5a and b, respectively, which were identified by oxygen trapping, by comparison of the IR and UV/Vis spectra with that of the parent anthronylidene 6, and by comparison of the IR spectrum with that calculated by DFT methods. The carbenes 5 are thermally stable under the conditions of matrix isolation; however, irradiation with visible or UV light results in the rearrangement to the quinone methides 10a and b.
    Additional Material: 3 Ill.
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  • 188
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    Metallated 2-Alkenyl Sulfoximines in Asymmetric Synthesis: Regio- and Stereoselective Synthesis of Highly Substituted Oxabicyclic Ethers and Studies Towards the Total Syntheses of the Euglobals G1 and G2 and Arenaran A (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1011-1031 
    Details
    ISSN: 1434-193X
    Keywords: Sulfoximines ; Oxabicyclic ethers ; Asymmetric synthesis ; Euglobal ; Arenaran ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -2-Cyclopentenyl- and 2-cyclohexenylmethyl sulfoximines can be converted into angular carbon-functionalised, highly substituted, isomerically pure (ds ≥ 98%) 2-oxabicyclo[3.3.0]octanes and 2-oxabicyclo[3.4.0]nonanes in high yields by a convenient one-pot sequence. Molecular frameworks such as these can be found in many biologically active natural products. In addition to the methodological work, we report on studies towards the total synthesis of the euglobals G1 and G2 and arenaran A.
    Additional Material: 1 Tab.
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  • 189
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    On the Behavior of 5,8-Bis(trimethylsilyl)cycloocta-1,3,6-triene in Cycloaddition Reactions and Subsequent Chemistry (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1041-1050 
    Details
    ISSN: 1434-193X
    Keywords: Phosphaalkynes ; Cycloadditions ; Polycycles ; Cage compounds ; λ3-Phosphinines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Phosphaalkynes 2 and electron-deficient alkynes 11 readily react in a [4 + 2] cycloaddition process with 5,8-bis(trimethylsilyl)cycloocta-1,3,6-triene (8) in its bicyclic form 10 to furnish regioselectively the tricyclodecadienes 12 and 13, respectively. The phosphorus-containing compounds 12 exhibit structural features which make them suitable for homo-Diels-Alder reactions with electron-deficient acetylenes. A single crystal structure analysis of the homo-Diels-Alder adduct 14b confirmed the structure and relative configuration of the phophatricyclodecadienes 12. In solution the tricyclodecadienes 13 are prone to facile cycloreversion yielding the phthalic esters 15 and the cyclobutene 16. The latter is rapidly converted into the corresponding 1,3-butadiene 18, which can be trapped in a Diels-Alder/phospha-ene/Diels-Alder tandem reaction sequence by phosphaalkyne 2a. The phosphatricyclodecadiene 12 is thermally more stable; loss of cyclobutene 16 only occurs under FVP conditions to afford the λ3-phosphinine 22.
    Additional Material: 1 Ill.
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  • 190
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    Totally Regio- and Stereoselective P-O-to-P-C Rearrangement in the Synthesis of Chiral P-(o-Hydroxyaryl)diazaphospholidine P-Oxides (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1099-1105 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Chiral synthons ; P-(o-Hydroxyaryl)diazaphospholidine P-oxides ; Rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The totally regio- and stereoselective P-O-to-P-C rearrangement in the synthesis of various chiral P-(o-hydroxyaryl)diazaphospholidine P-oxides has been investigated. This reaction proceeds with excellent yields ranging from 72 to 92%, total retention of configuration at the phosphorus atom, and complete regioselectivity. An exception was found with naphthyl derivatives, which gave mixtures of two regioisomers. In all cases, the products generated have been unambiguously characterized by 1H-, 13C-, and 31P-NMR spectroscopy as well as by X-ray-diffraction analysis.
    Additional Material: 3 Ill.
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  • 191
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    Palladium-Catalyzed Cyclocarbonylation of o-Ethynylphenols and Vinyl Triflates To Form 3-Alkylidene-2-coumaranones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1137-1141 
    Details
    ISSN: 1434-193X
    Keywords: Cyclocarbonylation ; Alkynes ; Catalysis ; Palladium ; Vinyl triflates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -o-Ethynylphenols react with vinyl triflates, in the presence of tetrakis(triphenylphosphane)palladium(0) and under carbon monoxide, to form 3-alkylidene-2-coumaranones in good yield.
    Additional Material: 1 Tab.
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  • 192
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    S-Linked Thiomimetics of Phytoalexin-Elicitor-Active, Branched Oligosaccharides, Their Synthesis, Protein-Binding Ability and Phytoalexin-Inducing Activity (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1143-1152 
    Details
    ISSN: 1434-193X
    Keywords: Sulfur-linked thiooligosaccharides ; Oligosaccharin thio analogs ; Phytoalexin elicitor thio analogs ; Soybean glucan-binding assays ; Structure-activity relationships ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The sulfur-linked pentathiohexasaccharide 3I,3IV-di-β-D-glucopyranosylthiogentiotetraose (12) has been prepared by a convergent approach involving the reaction of 1,2,4-tri-O-acetyl-6-deoxy-6-iodo-3-S-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-3-thio-β-D-glucopyranose (10) with the sodium salt of 2,3,4-tri-O-acetyl-6-S-[2,4-di-O-acetyl-3,6-di-S-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-3,6-dithio-β-D-glucopyranosyl]-1,6-dithio-β-D-glucopyranose (4). A further reaction, involving the sodium salt of the peracetylated β-1-thio derivative of 12 with 1,2,3,4-tetra-O-acetyl-6-deoxy-6-iodo-β-D-glucopyranose (26), afforded the homologous sulfur-linked hexathioheptasaccharide 3II,3V-di-β-D-glucopyranosylthiogentiopentaose (28). Related sulfur-linked positional isomers 3II,3IV-di-D-β-glucopyranosylthiogentiotetraose (34) and 3III,3V-di-β-D-glucopyranosylthiogentiopentaose (39) have been prepared using analogous synthetic strategies. Thus, SN2 displacement of the iodine atom in 10 by the sodium salt of 2,4-di-O-acetyl-3,6-di-S-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-1,3,6-trithio-β-D-glucopyranose afforded a tetrathiopentasaccharide, which resulted in the pentathiohexasaccharide 34 by a sequence of reactions involving the 1-thioglycose 32 in reaction with 26. The hexathioheptasaccharide 39 was obtained conveniently by the reaction of 26 with the acetylated 1-thio-6I, 3II, 6II, 3IV, 6IV-pentathio derivative 37, followed by deacylation. The four isomeric pentathiohexa- and hexathioheptasaccharides 12,34 and 28,39, respectively, were all found to be active in eliciting phytoalexin accumulation in soybean cotyledon tissue and in binding to a glucan-binding protein of soybean, although to a lesser extent than the corresponding O-oligosaccharides, the alternate thiohexa- and thioheptasaccharides 12,28 being more active as compared to the geminally branched isomers 34,39.
    Additional Material: 3 Tab.
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  • 193
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    Flash Vacuum Thermolysis of Acenaphtho[1,2-a]acenaphthylene, Fluoranthene, Benzo[k]- and Benzo[j]fluoranthene - Homolytic Scission of Carbon-Carbon Single Bonds of Internally Fused Cyclopenta Moieties at T ≥ 1100 °C (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1191-1200 
    Details
    ISSN: 1434-193X
    Keywords: Pyrolysis ; Ring contraction-ring expansion ; Rearrangements ; Homolytic scission ; IGLOIII//6-31G ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Flash vacuum thermolysis (FVT, 1000 °C ≥ T ≥ 1200 °C) of acenaphtho[1,2-a]acenaphthylene (3, C22H12) gave the C22H12 cyclopenta-fused polycyclic aromatic hydrocarbon (CP-PAH) acenaphtho[1,2-e]acenaphthylene (4), cyclopenta[cd]perylene (5) and cyclopenta[def]benzo[hi]chrysene (6). Whereas the formation of 4 is explained by a ring contraction/ring expansion rearrangement of 3, the identification of 5 and 6 suggests that 3 also undergoes homolytic scission of a five-membered ring's Carbon-Carbon single bond furnishing the transient diradical intermediate 7. Ring closure of 7to form 8 after rotation around the Carbon-Carbon single bond of the intact five-membered ring followed by hydrogen shifts will give 6. The latter can rearrange subsequently into 5by ring contraction/ring expansion. The structural assignment of 4 and 5 was supported by independent FVT of 6,12-bis(1-chloroethenyl)chrysene (14) and 3-(1-chloroethenyl)perylene (23), respectively. FVT of 14 (900-1200 °C) gave in a consecutive process 6,12-bis(ethynyl)chrysene (15), 9-ethynylbenz[j]acephenanthrylene (16) and bis(cyclopenta[hi,qr])chrysene (17). Although at T ≥ 900 °C 17 selectively rearranges into 4 by ring contraction/ring expansion, at 1200 °C the latter is converted into 5 presumably via a diradical intermediate obtained by homolytic scission of a single Carbon-Carbon bond of a five-membered ring. FVT of 23 gave in situ 3-ethynylperylene (25), which at 1000 °C is nearly quantitatively converted into 5. The propensity of internal cyclopenta moieties to undergo homolytic scission of a five-membered ring′s Carbon-Carbon single bond was corroborated by independent FVT of benzo[k]- (11) and benzo[j]fluoranthene (12). Previously unknown thermal pathways to important (CP)-PAH combustion effluents are disclosed at T ≥ 1000 °C.
    Additional Material: 4 Ill.
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  • 194
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    Chemical Reactions in the Axle of Rotaxanes - Steric Hindrance by the Wheel (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1233-1238 
    Details
    ISSN: 1434-193X
    Keywords: Electrophilic additions ; Bromine addition to double bonds ; Hydrogenation of double bonds ; Rotaxanes ; Supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Here we report on the possibility of using rotaxane wheels as noncovalent protecting groups which significantly decrease the activity of functional groups in the central part of the axle. The amide-linked rotaxanes 5aand 5b, each containing a C=C double bond in their axle, have been synthesised. The catalytic hydrogenation of these two rotaxanes proceeds slower than those of the corresponding free axle compounds 6a and 6b, indicating steric hindrance of the C=C double bond by the wheel of the rotaxane in each case. Nontheless, the rotaxane 9with an aliphatic (succinic acid) middle region in its axle can be prepared in this manner. Dehydrobromination of the axle in the rotaxane 15yields the rotaxane 16 with a C≡C triple bond located in the centre of the axle.
    Additional Material: 1 Tab.
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  • 195
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    The Cubane Cage - A Sensitive Probe for Assessing Substituent Effects on a Four-Membered Ring, Part II (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1253-1257 
    Details
    ISSN: 1434-193X
    Keywords: Cage compounds ; Cubanes ; Donor-acceptor systems ; Solid-state structures ; Substituent effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The crystal structures of methyl 4-methoxycubane-1-carboxylate (1), 1-acetamido-4-fluorocubane (2), methyl 4-acetoxycubane-1-carboxylate (3), 1,4-difluorocubane (4), 1,4-dichlorocubane (5), and N,N-diisopropylcubane-1,4-dicarboxamide (6) have been investigated by means of X-ray diffraction analysis. Fluorine and chlorine substituents cause a shortening of the vicinal bonds, as is seen in the 4-halocubane-1-carboxylates. The cage bonds vicinal to the ester substituent, with a favorable orientation with regard to the π-acceptor influence of this group become longer than the CH-CH bonds. Furthermore, the influence on bond length with respect to the orientation of this group relative to bonds within the cubane skeleton has been investigated experimentally. The effect of the methoxy group has also been found to depend on the orientation. The cage bond antiperiplanar to the methyl group is shortened, while the cage bonds in gauche orientation to this group are lengthened. As seen in the case of the halogen-substituted derivatives, the bonds bearing the acetoxy substituent are shortened due to the σ-acceptor property of this group. Ab initio calculations on compounds 1, 2, 4, and 5 performed at the 6-31G* level confirm the experimental results.
    Additional Material: 3 Ill.
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  • 196
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    Template-Directed Synthesis of a Rotacatenane (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1295-1302 
    Details
    ISSN: 1434-193X
    Keywords: Catenanes ; Mechanically interlocked molecules ; Molecular recognition ; Rotaxanes ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A [2]catenane, able to bind π-electron-rich guests inside the cavity of one of its two macrocyclic components has been designed and synthesized using supramolecular assistance. This recognition motif has been exploited to template the formation of a so-called rotacatenane - i.e., a molecule composed of a dumbbell-shaped component threaded through the cavity of one of the two mechanically interlocked macrocyclic components of a [2]catenane. The structure of this [2]catenane, as well as that of a model [2]catenane, have been characterized unequivocally by single-crystal X-ray analyses. Furthermore, some of the co-conformational changes associated with these mechanically interlocked molecules in solution have been probed by variable-temperature 1H-NMR spectroscopy.
    Additional Material: 10 Ill.
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  • 197
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    Diastereoselective Addition of Radicals to Chiral 1,3-Dioxin-4-ones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1057-1073 
    Details
    ISSN: 1434-193X
    Keywords: Free radicals ; Stereoselective addition ; Chiral 1,3-dioxin-4-ones ; Photoreactions ; Spirocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Intermolecular addition of radicals to the 1,3-dioxin-4-ones 1a,b and 2a,b with (-)-menthone incorporated as chiral auxiliary in 2-position were investigated. Photochemically generated radicals from 1,3-dioxolane, oxolane, and 2-propanol were added with high facial selectivity from the more exposed a-side. Intramolecular addition of 1,3-dioxolan-2-yl radicals to chiral dioxinones proceeded less efficiently and with lower selectivity also from the a-side. Nevertheless, it was possible to form the new spirocyclic compounds 22-27. The 1,3-dioxin-4-ones 32a,b possessing an unsaturated side chain were attacked by radicals at the terminal double bond. In the case of irradiation of 32b in 1,3-dioxolane a cyclization followed the intermolecular addition of a 1,3-dioxolan-2-yl radical and the dispiro compound 36 was formed. However, the formation of dispiro compound 40 required two reaction steps starting with irradiation of 32b and bromotrichloromethane. The achiral 1,3-dioxin-4-one 44 possessing an unsaturated side chain at C-2 was attacked by 1,3-dioxolan-2-yl radicals preferentially at C-6.
    Additional Material: 6 Ill.
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  • 198
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    Enantioselective Synthesis of the Chromane Moiety of Vitamin E (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1075-1084 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Atropisomerism ; Bis(hydroxylation) ; Conformational analysis ; Palladium ; Vitamin E ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Several new approaches for the enantioselective synthesis of the chromane moiety of vitamin E are described. Sonogashira coupling of 3a with the alkyne 4 and subsequent elimination gave 6, which was bis(hydroxylated) in 93% yield and with 85% ee. Recrystallization gave enantiopure 7a, which was hydrogenated and transformed into the vitamin E precursor 11. The bis(hydroxylation) of 18 and 21 to give 9 and 22, respectively, was less than satisfactory, proceeding with ee values of 28% and 18%. In contrast, stereoselective allylation of ketone 15 followed by removal of the protecting group or ozonolysis of the allyl moiety furnished the allyl alcohol 26 and the aldehyde 27, respectively, in almost enantiopure form, which again could be used as precursors for vitamin E. Partial hydrogenation of 5a gave the alkene 32a and that of 28 the alkene 30b, both of which show interesting atropisomerism.
    Additional Material: 3 Tab.
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  • 199
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    Crystalline Hosts Based on the Assembly of Anthracene and Bulky Alcoholic Groups - Host Synthesis, Complex Formation, and X-ray Crystal Structures of Several Inclusion Compounds (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1115-1125 
    Details
    ISSN: 1434-193X
    Keywords: Clathrate hosts ; Clathrates ; Crystalline inclusion compounds ; Clathrate structures ; Host-guest chemistry ; Anthracene derivatives ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A series of new clathrate host molecules (1-10) containing two diarylhydroxymethyl groups attached to different positions (1,5 or 1,8) of a basic anthracene construction unit have been synthesized. Their clathrate formation properties with a variety of organic guests, including amines, alcohols, ketones, and other dipolar aprotic compounds or aromatic hydrocarbons are reported (143 examples of clathrates). The inclusion properties and the clathrate stoichiometries depend in a systematic manner on the structure of the host molecules. The crystal structures of six selected clathrates of different classes of compound have been determined by X-ray diffraction.
    Additional Material: 6 Ill.
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  • 200
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    A Novel and Efficient Route towards α-GalNAc-Ser and α-GalNAc-Thr Building Blocks for Glycopeptide Synthesis (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1167-1171 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Glycals, nitro ; Michael additions ; Glycosylations ; Glycosides, galactosamine ; Reduction, nitro group ; Glycopeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Michael addition of serine and threonine derivatives 4a-4c to 3,4,6-tri-O-benzyl-2-nitro-D-galactal (1) afforded the corresponding 2-deoxy-2-nitro-α-D-galactopyranosides 5a-5c in good yield and stereoselectivity. 2-deoxy-2-nitroglycosides 5a and 5b were reduced to the 2-acetamido compounds by platinized Raney nickel T4. Manipulation of the protecting groups afforded known N-Fmoc-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-galactopyranosyl)-L-serine (8a) and -threonine (8b), valuable building blocks for O-glycopeptide synthesis.
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