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  • 2000-2004
  • 1990-1994  (950)
  • 1920-1924
  • 1992  (950)
  • Organic Chemistry  (916)
  • MRI
  • 1
    Electronic Resource
    Electronic Resource
    MRI of syphilitic myelitis (1992)
    Springer
    Neuroradiology 34 (1992), S. 105-106 
    Details
    ISSN: 1432-1920
    Keywords: syphilis ; spinal cord ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary MR imaging was performed on a patient with syphilitic myelitis. T2-weighted images showed high intensity areas in the thoracic spinal cord. On T1-weighted images after gadolinium-DTPA injection, heterogeneous enhancement was observed in the superficial portion of the spinal cord. The intramedullary high intensity areas on T2-weighted images disappeared after antibiotic therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588152
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  • 2
    Electronic Resource
    Electronic Resource
    Multiple occult vascular malformations of the brain and spinal cord: MRI diagnosis (1992)
    Springer
    Neuroradiology 34 (1992), S. 110-111 
    Details
    ISSN: 1432-1920
    Keywords: Angioma ; Central nervous system, angioma ; MRI, spinal cord ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We report a patient with multiple angiographically occult vascular malformations in the brain and spine. Magnetic resonance imaging showed multiple lesions in brain and spine with hypointense areas on both T1 and T2-weighted images. These hypointense areas are usually secondary to hemosiderin deposits consistent with remote bleeding in the lesions. We conclude that when magnetic resonance reveals an intraspinal lesion with signal intensity characteristics consistent with a vascular malformation, an examination of the brain should be performed to rule out associated intracranial lesions. The finding of multiple lesions in the brain with identical signal intensity characteristics reinforces the diagnosis of vascular malformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588154
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  • 3
    Electronic Resource
    Electronic Resource
    Cranial CT and MRI in diseases with DNA repair defects (1992)
    Springer
    Neuroradiology 34 (1992), S. 117-121 
    Details
    ISSN: 1432-1920
    Keywords: Cockayne's syndrome ; Ataxia telangiectasia ; Fanconis anaemia ; Central nervous system ; MRI ; CT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The CT and MRI appearances of 5 patients with Cockayne's syndrome, 5 with ataxia telangiectasia and 1 with Fanconi's anaemia are reported. These conditions, together with Bloom's syndrome and xeroderma pigmentosum are regarded as disorders of DNA repair. Characteristic CT and MRI features of Cockayne's syndrome include generalised atrophy, calcification in basal ganglia and dentate nuclei and white matter low density. Neuroradiological findings in the other DNA repair disorders are nonspecific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588156
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  • 4
    Electronic Resource
    Electronic Resource
    Lethal midline granuloma: impact of imaging studies on the investigation and management of destructive mid facial disease in 13 patients (1992)
    Springer
    Neuroradiology 34 (1992), S. 155-161 
    Details
    ISSN: 1432-1920
    Keywords: Granuloma paranasal sinuses ; Computed tomography ; MRI ; Lethal midline granuloma ; Lymphoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In 13 patients presenting as lethal midline granuloma (LMG), computed tomography proved essential for determining the extent of the disease, guiding biopsy and planning radiotherapy. Magnetic resonance imaging (MRI) was also helpful for the latter, because it could distinguish fluid retained within the paranasal sinuses from solid masses and tumour from granulation tissue; it was of little value for detecting bone lysis. Eight of the 13 patients proved to have T-cell lymphoma, two had Crohn's disease, in one the lesion was factitious and two had granulomas without diagnostic histological features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588164
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  • 5
    Electronic Resource
    Electronic Resource
    Multiple sclerosis masquerading as a mass lesion (1992)
    Springer
    Neuroradiology 34 (1992), S. 150-154 
    Details
    ISSN: 1432-1920
    Keywords: Multiple sclerosis ; MRI ; Mass lesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Six patients presenting with new neurological deficits underwent magnetic resonance imaging (MRI) that displayed mass lesions leading to diagnoses of tumor or abscess. Biopsy revealed demyelinating lesions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588163
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  • 6
    Electronic Resource
    Electronic Resource
    Arteriovenous malformations of the posterior fossa (1992)
    Springer
    Acta neurochirurgica 116 (1992), S. 119-127 
    Details
    ISSN: 0942-0940
    Keywords: Arteriovenous malformation ; cavernous angioma ; MRI ; surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary AVMs of the posterior fossa are reviewed on the basis of personal experience of 47 cases including 2 venous angiomas, 7 cavernous angiomas, 5 arteriovenous fistulas and 33 true arteriovenous malformations and of the few series reported in the literature. MRI is now an indispensable tool to define the exact localization of any malformation. Combined with angiography, it permits one to choose the most adequate therapeutic strategy and the best surgical approach. Radical cure is to be contemplated in most cases considering the often dramatic consequences of bleeding at the infratentorial level. Deep AVMs and moreover cavernous angiomas, even those located in highly functional structures such as the brain stem, can now be discussed for treatment. Encouraging results have already been obtained using, alone or in association, the recently advanced modalities of treatment: interventional neuroradiology, radiosurgery, and microsurgery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01540864
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  • 7
    Electronic Resource
    Electronic Resource
    Diagnosis of cervical disc disease (1992)
    Springer
    Acta neurochirurgica 116 (1992), S. 44-48 
    Details
    ISSN: 0942-0940
    Keywords: Cervical discectomy ; cervical radiculopathy ; cervical myelopathy ; disc herniation ; myelography ; magnetic resonance imaging ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In a prospective study of 63 surgical patients cervical myelography was compared with MRI to establish the relative value of the 2 diagnostic procedures in patient selection for surgery of ruptured cervical discs and bony nerve root compression. While MRI in the T1-weighted and gradient echo modes matched the diagnostic accuracy of invasive myelography (95%), T1 and T2-weighted MRI images alone were associated with an error rate of 10%. In patients with medial protrusion myelography did not always show the true extent of compression, whereas MRI tended to miss small laterally protruding disc fragments. Cervical myelography continues to have a place in the diagnosis of cervical disc disease, whenever clinical signs and symptoms do not agree with MRI data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01541252
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  • 8
    Electronic Resource
    Electronic Resource
    Malignancy and viability of intraparenchymal brain tumours: Correlation between Gd-DTPA contrast MR Images and proliferative potentials (1992)
    Springer
    Acta neurochirurgica 117 (1992), S. 187-194 
    Details
    ISSN: 0942-0940
    Keywords: Intraparenchymal brain tumour ; malignancy ; Gd-DTPA ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The feasibility of diagnosing the malignancy and viability of intraparenchymal brain tumours using Gd-DTPA, enhanced and unenhanced T1-weighted MRIs was investigated. The relationship between the Gd-DTPA enhancement pattern, the growth fraction (GF) determined by using the anti-bromode-oxyuridine (BrdU) monoclonal antibody, the clinical condition, the proliferative potential and the change of Gd-DTPA enhancement over time was studied. Forty-five patients with intracranial tumours were studied with the static method of Gd-DTPA MRI. The enhanced effect in Gd-DTPA MRIs was dependent on tumour-cell density, vascularization, necrosis, and dilatation of vascular lumen. Tumour-cells were observed in eighty-seven of eighty-nine specimens taken from areas with Gd-DTPA enhanced MRIs. Seventy-four percent of these specimens (64 of 87) showed a malignancy of more than 5% growth fraction. On the other hand, tumour cells were observed in twentyseven of fifty-six specimens taken from areas with Gd-DTPA unenhanced MRIs. Eighty-five percent of these specimens (23 of 27) showed a malignancy value of less than 5% GF. However, fifteen percent of these specimens showed values between 5 and 15% GF. In the kinetic study of Gd-MRIs five patients who were in a clinically stable condition and one patient who had radionecrosis showed a constant pattern of enhancement or slightly increased enhancement 30 min after injection compared to 4 min after injection. Therefore, GD-DTPA MRI can be used effectively in the diagnosis of tumour viability and malignancy after treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01400619
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  • 9
    Electronic Resource
    Electronic Resource
    Cystic mediastinal lesions in children: Evaluation by magnetic resonance and conventional imaging (1992)
    Springer
    European journal of pediatrics 151 (1992), S. 38-41 
    Details
    ISSN: 1432-1076
    Keywords: Mediastinal cysts ; MRI ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The signals obtained from mediastinal cystic lesions in children by magnetic resonance imaging (MRI) have been analysed. The advantages and pitfalls in establishing the final diagnosis by MRI are compared to the conventional radiographic technique and to computed tomography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02073888
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic resonance imaging of urinary bladder carcinoma: Tumor staging and gadolinium contrast-enhanced imaging (1992)
    Springer
    European radiology 2 (1992), S. 124-129 
    Details
    ISSN: 1432-1084
    Keywords: Urinary bladder carcinoma ; Pelvis ; MRI ; Gadolinium-DTPA ; T-Staging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Forty-nine patients with urinary bladder carcinomas underwent pre-operative examinations using magnetic resonance (MR) imaging. The results of the MR examinations were correlated with the clinical-pathological findings following transurethral resection (TUR) and bimanual palpation (n = 47) or radical cystectomy (n = 2). The results of pre-contrast MR tumor staging (T1, T2), viewing stages Tis-T2 collectively, and subsequent to separate assessments of stages T3b-T4b, were correct 76.6% of the time. Gadolinium-DTPA (Gd-DTPA) contrast-enhanced examinations (pre-contrast T1 and after Gd-DTPA) showed a staging accuracy rate of 85.7%. T2-weighted images did not indicate any advantage when compared to T1-weigthed images follwing Gd-DTPA. The signal intensity ratios of tumor/fat and tumor/muscle tissue were measured on T1-weighted pre-contrast images and following Gd-DTPA and then evaluated statistically, whereby the increased tumor signal intensity was statistically significant (Wilcoxon test, P 〈 0.01). Due to the relatively short examination time needed for T1-weighted images and the specific tumor enhancement, the administration of Gd-DTPA proves valuable in the diagnosis of bladder carcinomas. T2-weighted images are not necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171398
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  • 11
    Electronic Resource
    Electronic Resource
    Shoulder MRI: routine examinations using gradient recalled and fat-saturated sequences (1992)
    Springer
    European radiology 2 (1992), S. 142-147 
    Details
    ISSN: 1432-1084
    Keywords: MRI ; Shoulder ; Fat saturation ; Gradient-echo sequences ; Soft-tissue contrast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Although the signs of complete rotator cuff tears on MRI are well established, tendinitis and partial rotator cuff tears cannot always be readily depicted. In order to optimize the soft-tissue contrast of shoulder imaging without increasing imaging time for routine applications, we compared spin-echo and gradient-echo sequences with and without fat saturation and studied the soft-tissue contrast of spoiled gradient-echo sequences with several different parameters. We conclude, that fat-saturation is not necessary in order to improve the soft-tissue contrast. Successful fat suppression was only achieved in 50% of cases. We found a gradient-echo sequence with a double echo acquisition (echo times TE: 11 and 34 ms) with a long repetition time (TR: 600 ms) and a moderate flip angle (20°) very helpful in diagnosing rotator cuff pathology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171402
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  • 12
    Electronic Resource
    Electronic Resource
    Three-dimensional reconstruction (1992)
    Springer
    European radiology 2 (1992), S. 508-510 
    Details
    ISSN: 1432-1084
    Keywords: MRI ; Knee joint ; Three-dimensional reconstruction: preprocessing, segmentation, shading, surface rendering, volume rendering, hybrid rendering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We tried to improve the basic three-dimensional reconstruction technique by comparing preprocessing, segmentation, shading and rendering techniques in 15 examples of MR investigations of the knee joint. We conclude that signal-normalising, combined threshold and tracking segmentation, grey-level-gradient shading, and combined surface and volume rendering (i. e. hybrid rendering) are the methods of choice for the three-dimensional reconstruction process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187542
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  • 13
    Electronic Resource
    Electronic Resource
    Ultrasound and MRI in the diagnosis of penile induration (Peyronie's Disease) (1992)
    Springer
    European radiology 2 (1992), S. 230-232 
    Details
    ISSN: 1432-1084
    Keywords: Induratio penis plastica (IPP) ; Peyroni'es Disease ; Ultrasound ; MRI ; Gadolinium-enhanced
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Penile induration, a disease of connective tissue, requires the precise delineation and differentiation of inflammatory changes (plaques) for accurate therapy. Seventy two patients with clinically suspected Induratio penis plastica (IPP) underwent ultrasound examination between 1984 and 1991. In 37 patients (aged 18 to 80) the diagnosis was proven by ultrasound. Out of this group 27 patients were examined with magnetic resonance imaging (MRI), 15 of them with additional intravenous application of adolinium DTPA (Gd-DTPA). All examinations were performed within four weeks. The results showed, that ultrasound was able to detect plaques and changes of the tunica albuginea in all 37 cases, but MRI was more sensitive in the detection of possible inflammatory change (T2-prolongation and moderate Gd-DTPA enhancement in gradient-echo sequences. MRI revealed inflammatory changes in 22 of 27 examined patients while ultrasound detected only nine such cases out of 37. Ultrasound is the method of choice in diagnosing IPP, due to the overall sensitivity to plaques and changes in the tunica. On the other hand MRI offers valuable additional information with respect to inflammatory changes particularly after Gd-DTPA. Therefore MRI has the potential to improve therapeutic planning and should be used in monitoring therapeutic effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00595835
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  • 14
    Electronic Resource
    Electronic Resource
    Status of contrast media research in MRI, ultrasound and X-ray (1992)
    Springer
    European radiology 2 (1992), S. 2-13 
    Details
    ISSN: 1432-1084
    Keywords: Contrast media ; MRI ; Ultrasound ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714174
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  • 15
    Electronic Resource
    Electronic Resource
    Diffuse liver disease: MRI with Gd-DTPA versus CT and ultrasound (1992)
    Springer
    European radiology 2 (1992), S. 310-316 
    Details
    ISSN: 1432-1084
    Keywords: Diffuse liver disease ; MRI ; CT ; Ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Twenty-nine patients with diffuse liver disease were examined by ultrasound, CT and MRI. MRI was performed using T1- and T2-weighted spin-echo sequences as well as fast gradient-echo-sequences. The paramagnetic contrast agent Gd-DTPA was applied intravenously (0.1 mmol/kg). in patients with hepatitis, MRI could be used in guiding liver biopsies as inflammatory changes were clearly delineated. CT and ultrasound were superior to MRI in the detection of focal or diffuse fatty degeneration. On the other hand MRI was more helpful in differentiating fatty changes and neoplasm. In liver cirrhosis, fibrotic changes were most clearly demonstrated by MRI. In patients suffering from hemochromatosis MRI offers advantages over CT and ultrasound in the diagnosis and follow up due to the paramagnetic properties of iron, resulting in a reduction in signal intensity. In patients with Wilson's disease a characteristic pattern of parenchymal changes was seen. Administration of Gd- DTPA contributes additional information about perfusion conditions in the liver parenchyma, however this information was not of diagnostic relevance in the cases we studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175433
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  • 16
    Electronic Resource
    Electronic Resource
    White matter lesions in psychiatric patients: a retrospective MRI study (1992)
    Springer
    European radiology 2 (1992), S. 244-246 
    Details
    ISSN: 1432-1084
    Keywords: MRI ; Psychiatry ; white matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract T2-weighted MRI scans of psychiatric patients with at least one white matter lesion (WML) were compared to 83 non-psychiatric controls with respect to WML number and distribution. MANOVA results in significant effects for sex, age and patient group with respect to WML number. In the psychiatric patients, infratentorial WML prevailed in organic psychoses. WML number was positively correlated with age with the exception of rith temporal lobe WML. Based on WML spatial distribution, four patient clusters were found. Clusters with widely distributed WML comprised older patients with late onset of illness; right frontal and temporal WML were associated with mania, euphoria and unstable mood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00595838
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  • 17
    Electronic Resource
    Electronic Resource
    Intracranial cavernous angioma (1992)
    Springer
    Neurosurgical review 15 (1992), S. 125-133 
    Details
    ISSN: 1437-2320
    Keywords: Angiography ; cavernous angioma ; CT ; epilepsy ; hemorrhage ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report 14 cases of intracranial cavernous angioma, analyzing the clinical features, with special reference to the risk of bleeding, radiological images and treatment in these and in 153 published cases, 167 in all. Cerebral hemorrhage occurred in 44%: typical (intraparenchymal or subarachnoid) in 24.6%, and masked by epilepsy, headache or neurological deficits in 19.2%. In patients with the typical hemorrhagic pattern posthemorrhagic mortality was 12.2%. Of the patients who had a hemorrhage 42.5% were left with more or less disabling neurological deficits, and 16.4% had a rebleed. In discussing treatment we consider four groups of intracranial cavernous angioma: A) symptomatic in a zone of low surgical risk; B) asymptomatic with low surgical risk; C) symptomatic with high surgical risk; D) asymptomatic with high surgical risk. The treatment is surgical, except in the high risk asymptomatic variety, best followed initially with sequential CT scan and MRI and then considered for surgery if the lesion becomes symptomatic, increases in size or presents neuroradiological signs of bleeding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313508
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  • 18
    Electronic Resource
    Electronic Resource
    Detection of aortic dissection by magnetic resonance imaging in adults with Marfan's syndrome (1992)
    Springer
    The international journal of cardiovascular imaging 8 (1992), S. 249-254 
    Details
    ISSN: 1573-0743
    Keywords: Marfan ; MRI ; aortic dilatation ; dissection ; symptomatic ; asymptomatic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Marfan's syndrome is a connective tissue disorder, which mainly affects the cardiovascular system, together with ocular, skeletal and connective tissue. The cardiovascular manifestations in particular determine the mortality of this disorder. We studied 13 patients, suffering of Marfan's syndrome, with suspected aortic dilatation by means of magnetic resonance imaging (MRI). Aneurysmal dilatation of the aortic root and dissection were the two major findings in our study. Two of the five patients with dissections presented without relevant symptoms in the medical history nor at the time of the MRI examination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01146023
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  • 19
    Electronic Resource
    Electronic Resource
    Marchiafava-Bignami disease. A case studied by structural and functional brain imaging (1992)
    Springer
    European archives of psychiatry and clinical neuroscience 242 (1992), S. 69-71 
    Details
    ISSN: 1433-8491
    Keywords: Marchiafava-Bignami disease ; CT ; MRI ; SPECT ; Corpus callosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Marchiafava-Bignami disease (MBD) is a rare complication of chronic alcoholism. The clinical features, X-ray, CT and MRI findings are well documented. However, functional brain imaging has not been used in cases of MBD. We used single-photon emission computed tomography (SPECT) to monitor the regional cerebral blood flow in a patient suffering from a acute form of MBD, from which he subsequently recovered. Several abnormalities were found. A more frequent use of functional brain imaging in MBD could improve our knowledge of pathogenesis and prognosis for MBD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02191548
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  • 20
    Electronic Resource
    Electronic Resource
    Chondrosarcoma of the mandibular condyle: Report of a case (1992)
    Springer
    Oral radiology 8 (1992), S. 37-43 
    Details
    ISSN: 1613-9674
    Keywords: Chondrosarcoma ; Mandibular condyle ; CT ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A rare case of chondrosarcoma of the mandibular condyle is reported. CT and MRI were available in the diagnosis of chondrosarcoma, but plain radiograms were nearly non-contributory. Microscopically, the malignant chondroid tissue and malignant chondrocytes were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02347276
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  • 21
    Electronic Resource
    Electronic Resource
    A case of treatment-related leukoencephalpathy: sequential MRI, CT and PET findings (1992)
    Springer
    Journal of neuro-oncology 14 (1992), S. 143-149 
    Details
    ISSN: 1573-7373
    Keywords: CT ; irradiation ; leukoencephalopathy ; methotrexate ; MRI ; PET
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of treatment-related leukoencephalopathy is presented. A patient with medulloblastoma was postoperatively treated with craniospinal axis irradiation. One month after irradiation, weekly intrathecal administration of methotrexate was performed 4 times to treat cerebrospinal fluid dissemination of the tumor. Two months after the initiation of intrathecal chemotherapy, the patient became somnolent and developed decerebrate posturing. Magnetic resonance imaging showed diffuse leukoencephalopathy. Positron emission tomography revealed a diffuse decrease in glucose uptake in the deep white matter. Auditory evoked potential also showed diffuse abnormalities, not only in the cerebrum, but also in the brain stem. High dose intravenous leucovorin rescue was attempted without any neurologic improvement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00177618
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  • 22
    Electronic Resource
    Electronic Resource
    Comparison of myelography combined with postmyelographic spinal CT and MRI in suspected metastatic disease of the spinal canal (1992)
    Springer
    Journal of neuro-oncology 13 (1992), S. 231-237 
    Details
    ISSN: 1573-7373
    Keywords: metastatic disease ; spinal cord ; MRI ; myelography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Comparison between myelography (MY) and magnetic resonance imaging (MRI) was carried out in 36 patients with clinical suspicion of spinal cord or root compression due to metastatic disease in the spinal canal. In 3 patients metastatic lesions were visualized on MY but not on MRI, while there were no cases with a negative MY and a positive MRI. In 44% of the cases MY alone or combined with postmyelographic CT (pm-CT) showed a larger tumor extension than did MRI, while the opposite occurred in 25%. As for detection of bony metastases and tumor masses localized outside the spine there was no difference between MRI and MY + pm-CT. The results indicate that the choice between MRI and MY + pm-CT still can be based on the availability and quality of the procedure at a given institution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172475
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  • 23
    Electronic Resource
    Electronic Resource
    The role of MRI in the diagnosis of olivopontocerebellar atrophy (1992)
    Springer
    Neurological sciences 13 (1992), S. 151-156 
    Details
    ISSN: 1590-3478
    Keywords: Olivopontocerebellar atrophy ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Sotto il termine di atrofia olivo-pontocerebellare si raggruppano quadri nosografici di verosimile diversa origine, caratterizzati tutti dalla presenza di segni clinici deficitari pontini e cerebellari. La diagnosi è stata sino ad ora solo clinica con conferma autoptica del danno pontocerebellare. Sono descritti tre casi di atrofia olivo-pontocerebellare, appartenenti, a tre distinti sottogruppi ed in fasi diverse della malattia. In tutti e tre i casi la MRI ha evidenziato un quadro di atrofia pontina e cerebellare ed una riduzione dimensionale delle olive bulbari che risultava in un allargamento dell'angolo pontobulbare normalmente rilevabile sulla faccia anteriore del tronco in proiezione laterale. L'esame si conferma di importanza diagnostica essenziale nella malattia sin dalle sue fasi iniziali.
    Notes: Abstract Under the term of olivopontocerebellar atrophy different nosological pictures are grouped, all characterized by showing clinical signs of deficiency of the structures of the pons and of the cerebellum. The diagnosis of olivopontocerebellar atrophy has been made, until now, by clinical criteria while typical anatomopathological changes are found at the autoptic studies. We describe three patients affected by olivopontocerebellar atrophy, of different types and at different stages of disease. In all cases MRI showed a similar and typical picture of atrophy of the olivary eminences of the medulla oblongata resulting in straightening of the angle usually present on the ventral frontier between pons and medulla oblongata. This diagnostic tool demonstrated thus to be of primary relevance yet in the early phases of the disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02226964
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  • 24
    Electronic Resource
    Electronic Resource
    Bickerstaff brainstem encephalitis. A case report (1992)
    Springer
    Neurological sciences 13 (1992), S. 165-168 
    Details
    ISSN: 1590-3478
    Keywords: Bickerstaff brainstem encephalitis ; Miller Fisher syndrome ; SOAA ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Viene descritto il caso di una paziente che, tre settimane dopo aver sofferto una sindrome influenzale, presentò un quadro clinico caratterizzato da oftalmoplegia, atassia ed are flessia osteotendinea il quale, come è noto, caratterizza sia la sindrome di Bickerstaff che quella di Miller Fisher. La normalità degli esami neurofisiologici (SEPs, VEPs, BAEPs, studio della VCM, VCS), il reperto liquorale e, soprattutto, l'esame di risonanza magnetica encefalica hanno permesso di ricondurre il quadro sindromico osservato and una compromissione del mesencefalo.
    Notes: Abstract A 33-year-old woman three weeks after a febrile illness presented with a syndrome of ophthalmoplegia, ataxia and areflexia (SOAA) that characterizes clinically both Bickerstaff and Miller Fisher syndromes. The normality of the electrophysiological tests performed, the CSF findings and the magnetic resonance images proved that the syndrome stemmed from brainstem pathology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02226967
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    Electronic Resource
    Electronic Resource
    MRI demonstration of the cerebellar damage in diffuse hypoxic-ischemic encephalopathy. Case report (1992)
    Springer
    Neurological sciences 13 (1992), S. 517-519 
    Details
    ISSN: 1590-3478
    Keywords: MRI ; cerebellum ; anoxic ; ischemic encephalopathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Un indagine di RM rivelò un quadro di alterazioni simmetriche nel putamen e negli emisferi cerebellari in una paziente sopravvissuta ad un arresto cardiorespiratorio dovuto a polineurite acuta idiopatica. Dal momento che alterazioni simili possono far seguito ad intossicazione da cianuro o da metanolo, la diagnosi differenziale di queste condizioni deve tener conto sia degli elementi clinico-anamnestici sia degli elementi della diagnostica per immagini.
    Notes: Abstract MRI demonstrated symmetric putaminal and cerebellar changes in a patient who survived a cardiorespiratory arrest due to acute idiopathic polyneuritis. Since similar aspects can be observed following cyanide or methanl poisoning differential diagnosis from these conditions has to rely on the combination of clinical and imaging findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02230874
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    Electronic Resource
    Electronic Resource
    Acute cervical radiculopathy due to vertebral A-V fistula (1992)
    Springer
    Neurological sciences 13 (1992), S. 603-605 
    Details
    ISSN: 1590-3478
    Keywords: Cervical radiculopathy ; vertebral A-V fistula ; CT ; MRI ; angiography ; embolization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Descriviamo il caso di una donna di 28 anni, che soffrì di una radicolopatia acuta prevalente motoria C5-C6 destra da fistola congenita artero-venosa vertebrale. Il reperto di un soffio latero-cervicale fece valorizzare i quadri T.A.C. e R.M. Lo studio arteriografico fu diagnostico, la fistola venne embolizzata con successo.
    Notes: Abstract We report the case of a 28 year old woman with acute, mainly motor, radiculopathy at C5-C6 on the right side secondary to a congenital vertebral arteriovenous fistula. The finding of a bruit at the side of the neck lent weight to the CT and MRI findings. Angiography was diagnostic. The fistula was embolized successfully.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02233405
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    Electronic Resource
    Electronic Resource
    Chronic spstic atrophic hemiparesis with benign course (1992)
    Springer
    Neurological sciences 13 (1992), S. 611-616 
    Details
    ISSN: 1590-3478
    Keywords: Mills syndrome ; chronic spastic atrophic hemiparesis (CSAH) ; MRI ; CT scan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Vengono presentati i dati clinici e neuroradiologici relativi a quattro pazienti (età media 62 anni, range 54–67; follow-up medio 19,5 anni, range 26 mesi-29 anni) affetti da emiparesi cronica spastica ed atrofica (CSAH). La TAC e la RMN cerebrale hanno evidenziato la presenza di lesioni localizzate nel centro semiovale in due casi, in regione parieto-occipitale e a livello del ponte in un caso ciascuno. Questo studio sottolinea il fatto che i pazienti con CSAH possono presentare una prognosi favorevole a lunggo termine. Lo studio con RMN cerebrale può evidenziare lesioni a livello della sostanza bianca emisferica o del tronco cerebrale ed è pertanto indicato in tutti i soggetti con CSAH. Tuttavia, ulteriori studi sono necessari al fine di chiarire la natura delle lesioni osservate.
    Notes: Abstract We present the clinical and neuroimaging data of 4 patients (mean age: 62 years, range 54–67; mean follow-up: 19.5 years, range: 26 months-29 years) with chronic spastic atrophic hemiparesis (CSAH). Neuroimaging findings were non specific, CT scan and MRI showing white matter lesions located within the centrum semiovale in two cases, parieto-occipital lobe and pons in one case each. This study underlines that patients with CSAH may have a good long-term prognosis. MRI studies may demonstrate associated lesions within the white matter or brainstem and are advisable in all subjects with CSAH, but further studies are necessary to clarify the nature of the observed lesions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02233407
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    Electronic Resource
    Electronic Resource
    Gd-DTPA enhanced MRI for the oral and maxillofacial cystic lesion (1992)
    Springer
    Oral radiology 8 (1992), S. 33-39 
    Details
    ISSN: 1613-9674
    Keywords: MRI ; Gd-DTPA ; Cystic lesion ; Odontogenic tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The authors present examples of the significantly improved diagnostic imaging for cystic lesions in the jaw bone, floor of the mouth and maxillary sinus with Gadolinium-DTPA (Gd-DTPA) enhanced MRI. Twelve cases of cystic lesions, which were 6 cases of intra-osseous odontogenic cysts and cystic tumors, 2 cases of epidermoid cysts in the floor of the mouth and 4 cases of cystic polyp of the maxillary sinus. Improved MR images provided useful information delineating the thickness of circumscribed soft tissue wall (cystic wall), the location of the intra-cystic substance and the configuration of the tumor masses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02347808
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  • 29
    Electronic Resource
    Electronic Resource
    Fuzzy rules to predict degree of malignancy in brain glioma (1992)
    Springer
    Medical & biological engineering & computing 40 (1992), S. 145-152 
    Details
    ISSN: 1741-0444
    Keywords: Brain glioma ; Classification ; Fuzzy rule extraction ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The current pre-operative assessment of the degree of malignancy in brain glioma is based on magnetic resonance imaging (MRI) findings and clinical data. 280 cases were studied, of which 111 were high-grade malignancies and 169 were low-grade, so that regular and interpretable patterns of the relationships between glioma MRI features and the degree of malignancy could be acquired. However, as uncertainties in the data and missing values existed, a fuzzy rule extraction algorithm based on a fuzzy min-max neural network (FMMNN) was used. The performance of a multi-layer perceptron network (MLP) trained with the error back-propagation algorithm (BP), the decision tree algorithm ID3, nearest neighbour and the original fuzzy min-max neural network were also evaluated. The results showed that two fuzzy decision rules on only six features achieved an accuracy of 84.6% (89.9% for low-grade and 76.6% for high-grade cases). Investigations with the proposed algorithm revealed that age, mass effect, oedema, post-contrast enhancement, blood supply, calcification, haemorrhage and the signal intensity of the T1-weighted image were important diagnostic factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02348118
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    Electronic Resource
    Electronic Resource
    Tomographic abdominal anatomy with magnetic resonance color composites (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 5 (1992), S. 169-184 
    Details
    ISSN: 0897-3806
    Keywords: MRI ; abdomen ; liver ; Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Magnetic resonance imaging (MRI) is an excellent modality for tomographically visualizing abdominal structures, particularly the liver, In an effort to simulate the natural color scheme of the living abdomen using MRI, we have generated color composites from sets of gray tone MR images obtained at corresponding anatomic slice positions from two healthy individuals. Pulse sequences used for our image sets included T1-, T2-, and proton density-weighted spin echo sequences as well as an angiographic FISP gradient echo sequence. A PC/AT-compatible computer with 24-bit graphics display capbilites, along with commerical and customized image-processing software, was used for composite generation. The applied colors were selected based on quantitative characteristics tissue intensity patterns so that tissue contrast could be optimized in the final image. The generated composites were correlated with cadaver sections to evaluate the color scheme of these false-colored images. With our composite generation techniques, it was possible to generated near-natural appearing color images of the abdomen. Color composites may be useful for teaching human cross-sectional anatomy and may also have diagnostic applications in abdominal MRI studies. © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980050302
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    Enantioselectivity of lipase-catalyzed hydrolysis of some 2-chloroethyl 2-arylpropanoates studied by chiral reversed-phase liquid chromatographySecond International Symposium on Chiral Discrimination, May 27 - 31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 98-102 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; lipase ; 2-chloroethyl esters ; 2-arylpropanoic acids ; chiral liquid chromatography ; enantiomer separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A technique based exclusively on chiral reversed-phase liquid chromatography has been shown to greatly facilitate studies of enantioselectivity in lipase-catalyzed hydrolysis of chiral organic esters. Only two sets of experimental data are needed to calculate the enantioselectivity (E) of a kinetically controlled enantiomer-differentiating reaction of this kind, viz. the enantiomeric excess of the product (eep) or substrate (ees), and the degree of substrate conversion (c). The product enantiomers are well separated on a BSA-based column, giving eep directly. In addition, separation of the (unresolved) ester substrate from the enantiomeric products gives c by integration. Via an optimization of the mobile phase used in the chiral chromatographic system, both these parameters can often be determined in a single run. Highly precise and detailed kinetic studies of the enzymatic reaction can thus be performed. In this way, E-values have been determined for a series of 2-chloroethyl 2-arylpropanoates hydrolyzed in the presence of a Candida cylindracea lipase at pH 6.0 and 7.1. Effects on the E-values from a partial purification and further processing of the lipase have also been studied.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040206
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    Enzymatic resolutions of α- and β-hydroxypropionic acid esters (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 103-109 
    Details
    ISSN: 0899-0042
    Keywords: dihydrocinnamic acid derivatives ; hydroxy azido acids ; hydroxy amino acids ; enantioselective hydrolysis ; Pseudomonas fl. lipase ; Candida cyclindracea lipase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of some acyloxy-methoxy-cinnamic acid derivatives, azidohydroxy butanoates, and azidohydroxy butanedioates in enantiomerically pure form is presented. Racemic diastereomerically pure educts were prepared in few steps. These racemates are resolved with lipases from Candida cylindracea (CC) and Pseudomonas fluorescens (P).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040207
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  • 33
    Electronic Resource
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    Optical resolution of β-lactams on 1-phenylethylcarbamates of cellulose and amylose (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 122-124 
    Details
    ISSN: 0899-0042
    Keywords: 4-acetoxy-2-azetidinone ; antibiotics ; carbapenem ; HPLC ; chiral stationary phases ; cellulose tris(1-phenylethylcarbamate) ; amylose tris(1-phenylethylcarbamate) ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical resolution of six β-lactams was examined by HPLC using chiral stationary phases consisting of tris((R)-, (RS)-, and (S)-1-phenylethylcarbamate)s of cellulose and amylose. All β-lactams were optically resolved at least by one of the carbamates. Amylose tris((S)-1-phenylethylcarbamate) showed high optical resolving abilities for some β-lactams.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040210
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    Cyclodextrin derivatives in GC separation of racemic mixtures of volatiles: Part IIISecond International Symposium on Chiral Discrimination, May 27 - 31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 125-131 
    Details
    ISSN: 0899-0042
    Keywords: capillary gas chromatography ; enantiomer resolution ; cyclodextrin derivatives ; chromatographic performance ; cyclodextrin/OV-1701 dilution ; operative temperature ; film thickness ; column length ; column conditioning ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas chromatographic performance of differently derivatized α-, β-, and γ-cyclodextrins in the separation of racemic mixtures of volatiles is investigated. The performances of 2,3,6-permethylated α-, β-, and γ;-cyclodextrins and 2,6-dimethyl-3-trifluoro-acetyl α-, β-, and γ-cyclodextrins mixed with different ratios of OV-1701 or OV-1701-OH terminated were tested with racemates with widely differing structures. The influence of the percentage of cyclodextrins in polysiloxane, of film thickness of the stationary phase, of the length of the column, of column conditioning, and of the operating temperatures in the separations of different racemates has been evaluated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040211
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  • 35
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    Stereoselective disposition and tissue distribution of carvedilol enantiomers in rats (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 148-154 
    Details
    ISSN: 0899-0042
    Keywords: carvedilol enantiomers ; kinetics ; tissue-to-blood partition coefficient ; plasma protein binding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: After intravenous bolus injection of rac-carvedilol at 2 mg/kg to the rat, the (+)-(R)- and ( - )-(S)-enantiomer levels in the blood and tissues (liver, kidney, heart, muscle, spleen, and aorta) were measured by stereospecific HPLC assay. As compared with the (+)-(R), the ( - )-(S) had a larger Vdss (3.32 vs. 2.21 liter/kg), MRT (33.4 vs. 25.6 min), and CLtot (96.1 vs. 83.8 ml/min/kg). AUC comparison after iv and po administration showed systemic bioavailability of the ( - )-(S) to be about half that of its antipode, explained by the fact that the free fraction of the ( - )-(S) in blood was 1.65-fold greater than that of the (+)-(R). Tissue-to-blood partition coefficient values for the ( - )-(S) were 1.6- to 2.1-fold greater than those for the (+)-(R) in all tissues, showing that the ( - )-(S) accumulates more extensively in the tissues. These results were consistent with the greater Vdss for the ( - )-(S) estimated from systemic blood data. The stereoselective tissue distribution of carvedilol enantiomers results from an enantiomeric difference in plasma protein binding rather than in tissue binding. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040304
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    Liquid chromatographic separation of chiral diarylcarbinolsSecond International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 170-173 
    Details
    ISSN: 0899-0042
    Keywords: chiral phases ; chiral recognition mechanism ; alcohols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct HPLC separation of three chiral carbinols of general formula Mesityl-CH(OH)-Aryl has been achieved using Pirkle (R)-DNBPG ionic or covalent columns and, for Aryl = o-tolyl, on a Chiralpak OP(+) phase. It is apparent that steric hindrance and hydrogen bonding play important roles in chiral recognition. Two compounds structurally very similar but lacking the hydroxyl group were not resolved in their enantiomeric pairs. © 1992 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040307
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    Electronic Resource
    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040401
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  • 38
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    Spontaneous racemization of chlorthalidone: kinetics and activation parameters (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 222-226 
    Details
    ISSN: 0899-0042
    Keywords: 3-hydroxy-3-phenylphthalimidines ; inversion (of configuration) ; barrier to inversion ; rate constants (of inversion) ; enantiomer interconversion ; carbonium ion (intermediate in racemization) ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of chlorthalidone (CTD) and a minor, achiral dehydration product, δ2-CTD, are shown to exist in dynamic equilibrium in aqueous media through a carbonium ion intermediate. The barrier to inversion at carbon is low for an uncatalyzed system: ΔG
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040404
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    Stereoselective binding of etodolac to human serum albuminPresented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 240-246 
    Details
    ISSN: 0899-0042
    Keywords: NSAID ; chirality ; enantiomers ; protein binding ; equilibrium dialysis ; fluorescent specific markers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The protein binding of etodolac enantiomers was studied in vitro by equilibrium dialysis in human serum albumin (HSA) of various concentrations varying from 1 to 40 g/liter, by addition of each enantiomer at increasing concentrations. In the 1 g/liter solution, at the lowest drug levels, the (R)-form is more bound than its antipode, the contrary being observed at the highest drug levels. For higher albumin concentrations, S was bound in a larger extent than R. Using the displacement of specific markers of HSA sites I and II, studied by spectrofluorimetry, it was suggested that R and S are both bound to site I, while only S is strongly bound to site II. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040407
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  • 40
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    Resolution of terfenadine enantiomers by β-cyclodextrin chiral stationary phase high-performance liquid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 268-272 
    Details
    ISSN: 0899-0042
    Keywords: HPLC ; chiral stationary phase ; optical isomers ; absolute configuration ; circular dichroism ; chiral ; enantiomers ; terfenadine ; cyclodextrin ; normal phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomers of terfenadine were resolved by high-performance liquid chromatography (HPLC) using a chiral stationary phase (CSP) column packed with β-cyclodextrin (β-CD) covalently bound to silica. Separation was achieved in both the reverse phase and normal phase modes. Resolution of enantiomers was confirmed by ultraviolet-visible absorption, circular dichroism, and mass spectral analysis.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040411
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    Obituary: professor goran schill (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 273-273 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040502
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  • 42
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    Effects of the stereochemical orientation of phenethylamines and imidazolines on α-adrenergic receptor-mediated dna synthesis in primary cultured rat hepatocytes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 279-285 
    Details
    ISSN: 0899-0042
    Keywords: stereochemistry ; catecholamines ; DNA synthesis ; liver regeneration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hepatic α1-adrenergic receptor mediates a variety of hepatic functions including respiration, glycogenolysis, gluconeogenesis, and growth. We have utilized a rat primary hepatocyte culture system to show that the α1-adrenergic receptor can be activated in a stereoselective manner by a series of phenethylamines and catecholimidazolines resulting in the stimulation of DNA synthesis as determined by [3H]thymidine incorporation. The phenethylamines adhered to the Easson-Stedman hypothesis with a rank order of potency of (-)-(R)-norepinephrine (NE) 〉 (+)-(S)-NE 〉 the desoxy analog dopamine (DA) for the stimulation of DNA synthesis. However, the 2-substituted catecholimidazolines did not follow this trend and demonstrated an order of potency of the desoxy analog 3,4-dihydroxybenzyl imidazoline (DHT) ≥ (-)-(R)-2-(3,4,α-trihydroxybenzyl)imidazoline (TBI) 〉 (+)-(S)-TBI. 4-Substituted catecholimidazolines were less potent as inducers of DNA synthesis than the corresponding 2-substituted analogs with an order of potency of (+)-(R)-4-(3,4-dihydroxybenzyl)imidazoline (DBI) 〉 (+, -)-(R,S)-DBI 〉 (-)-(S)-DBI. When the β-hydroxyl moiety of NE is replaced with an amino group as in 3,4-dihydroxyphenylethylenediamine, the isomers are less active than the β-hydroxylated analogs and also demonstrate no stereoselectivity for the stimulation of DNA synthesis. These results demonstrate that the hepatic α1-adrenergic receptor can recognize various isomeric forms of these compounds and that hepatocellular growth can be modulated in a stereoselective manner by phenethylamines and imidazolines. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040504
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    Some mechanistic aspects on chiral discrimination of organic acids by immobilized bovine serum albumin (BSA) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 24-29 
    Details
    ISSN: 0899-0042
    Keywords: organic acids ; enantiomers ; BSA ; chiral discrimination ; hydrophobic interaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although chiral anionic compounds, notably a large number of organic acids, have been found to be readily separated into enantiomers on BSA-based columns, the structural requirements for an efficient enantiomer discrimination by the protein is still not very well known. Since it is often observed that very hydrophobic acids, like many of the antiinflammatory “profens,” can be resolved with large separation factors for the enantiomers, a systematic study of a series of racemic α-substituted alkanoic acids was made. The series of analytes was prepared from α-amino acids, RCH(NH2)CO2H (where R = C1-C6), by reaction with N-(chloroformyl)-carbazole. A rapid increase in the capacity ratios of both enantiomers was found with increasing length of R. The effect, however, was larger for the last eluted enantiomer, leading to a substantial increase in the separation factor; this being 7.3 for R = C6 in 20 mM phosphate buffer (pH 8.0) with 30% of acetonitrile. Further, the separation factor also increased with decreasing organic modifier content. Thus when the R = C6-analyte was run at a mobile phase concentration of 20% acetonitrile and a flow rate of 1.5 ml/min, the time difference between the two eluted enantiomers exceeded 20 hr.A reasonable interpretation of our results seems to be that enantioselectivity is promoted by increased hydrophobic interaction. Since the anionic charge of the analyte is also taking part in the retention mechanism, a tight binding of the analyte will result from simultaneous electrostatic and hydrophobic interaction. When the latter is increased, less conformational freedom will be left for the analyte and the steric configuration at the α-carbon atom will become more and more important. Steric hindrance by the α-substituent in the first eluted enantiomer will counteract the tight binding caused by the combined binding interactions and lead to a smaller increase in the capacity ratio.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040107
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    4',6-Dichloroflavan (BW683C): Enantiomeric separation by hplc/dad and antirhinovirus activity (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 65-67 
    Details
    ISSN: 0899-0042
    Keywords: optical resolution ; chiral HPLC ; chiral stationary phase ; 4',6-dichloroflavan ; circular dichroism ; antirhinovirus activity ; BW683C ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic 4',6-dichloroflavan (BW683C), a highly effective inhibitor of rhinovirus serotype 1B in vitro, was resolved by high-performance liquid chromatography on a chiral stationary phase. The enantiomers were separately collected and circular dichroism curves were obtained, in order to determine the absolute configuration of the two enantiomers. The activity of the isomers was studied on human rhinovirus serotype 1B multiplication in HeLa cell cultures, by means of the plaque reduction assay. Both enantiomers were potent inhibitors of virus replication; by comparing the IC50 values, the S form was 3.5 times more effective than the R form.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040114
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    Erratum (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 71-71 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040116
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    Pulmonary inversion of 2-arylpropionic acids: Influence of protein binding (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 349-352 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; fenoprofen ; flurbiprofen ; rabbit lung ; first-pass ; presystemic ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The possible contribution of pulmonary metabolism to the putative first-pass metabolism of 2-arylpropionic acid nonsteroidal antiinflammatory drugs has not been documented. Isolated perfused rabbit lungs, perfused with 4.5% bovine serum albumin or 5% dextran, were used to study the pulmonary elimination of (R)- and rac-ibuprofen, fenoprofen, and flurbiprofen. In the absence of protein binding, ibuprofen was metabolized via inversion and other pathways, whereas fenoprofen metabolism was essentially restricted to inversion of the (R)-enantiomer; fraction inverted (± SE) was 0.37 ± 0.05 for (R)-ibuprofen and 0.85 ± 0.03 for (R)-fenoprofen. In the presence of protein, neither ibuprofen nor fenoprofen was metabolized. Flurbiprofen did not undergo pulmonary elimination under any condition studied. This study illustrates that even though a tissue is capable of metabolism, particularly inversion of 2-arylpropionics, the quantitative importance of such elimination pathways may be minimal in the presence of the high degree of protein binding that is characteristic of these drugs. © 1992 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040604
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    Formation of glycine conjugate and (-)-(R)-enantiomer from (+)-(S)-2-phenylpropionic acid suggesting the formation of the coa thioester intermediate of (+)-(S)-enantiomer in dogs (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 342-348 
    Details
    ISSN: 0899-0042
    Keywords: arylpropionic acid ; 2-phenylpropionic acid ; glycine conjugation ; stereoselectivity ; chiral inversion ; reverse chiral inversion ; glycine N-acyl transferase ; dog hepatocytes ; chiral HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been proposed that the chiral inversion of the 2-arylpropionic acids is due to the stereospecific formation of the (-)-R-profenyl-CoA thioesters which are putative intermediates in the inversion. Accordingly, amino acid conjugation, for which the CoA thioesters are obligate intermediates, should be restricted to those optical forms which give rise to the (-)-R-profenyl-CoA, i.e., the racemates and the (-)-(R)-isomers. We have examined this problem in dogs with respect to 2-phenylpropionic acid(2-PPA). Regardless of the optical configuration of 2-phenylpropionic acid administered, the glycine conjugate was the major urinary metabolite and this was shown to be exclusively the (+)-(S)-enantiomer by chiral HPLC. Both (-)-(R)- and (+)-(S)-2-phenylpropionic acid were present in plasma after the administration of either antipode, and further evidence of the chiral inversion of both enantiomers was provided by the presence of some 25% of the opposite enantiomer in the free 2-phenylpropionic acid and its glucuronide excreted in urine after administration of (-)-(R)- and (+)-(S)-2-phenylpropionic acid. The (+)-(S)-enantiomer underwent chiral inversion to the (-)-(R)-antipode when incubated with dog hepatocytes. These data suggests that both enantiomers of 2-phenylpropionic acid are substrates for canine hepatic acyl CoA ligase(s) and thus undergo chiral inversion, but that the CoA thioester of only (+)-(S)-2-phenylpropionic acid is a substrate for the glycine N-acyl transferase. These studies are presently being extended to the structure and species specificity of the reverse inversion and amino acid conjugation of profen NSAIDs. © 1992 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040603
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    HPLC resolution of atropoisomeric compounds on a csp derived from (1R;2R)-diaminocyclohexane: Thermodynamic data from variable temperature chromatographyThis paper was presented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 384-388 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; polymeric CSPs ; enthalpy ; entropy ; H-bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and a preliminary chromatographic evaluation of a novel polymeric chiral stationary phase (CSP) derived from (1R;2R)-diaminocyclohexane (DACH) are presented. A radical copolymerization process has been employed to generate a silica-based chiral sorbent, showing considerable high chemical and thermal stability and stereoselectivity toward racemic compounds capable of H-bonding (3-hydroxy-benzodiazepin-2-ones, chlorthalidone, atropoisomeric sulfur compounds, etc.); in the present paper we present the investigation on the resolution of racemic dihydroxy biarylic atropoisomers; the effects of eluent composition and of temperature on the separation ability of the CSP have been studied in order to elucidate the recognition mechanism operating in these chiral separations. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040609
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    Announcement (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 406-406 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040614
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040701
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    Optical resolution of unusual amino acids using microbial proteases (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 427-431 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; amino acid enantiomers ; Aspergillus oryzae protease ; Bacillus subtilis protease ; enantioselectivity ; enantiomeric purity determination ; HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have developed novel enzymatic methods for the optical resolution of unusual amino acids. In this work, we tried two microbial proteases, available inexpensively in a crude state, from Aspergillus oryzae and from Bacillus subtilis. The enantioselective hydrolysis of the methyl esters of the N-benzyloxycarbonyl (Z) derivatives of a number of amino acids, both aliphatic and aromatic, was examined using these microbial proteases. The enantiomeric purities of the resolved Z-amino acids were determined accurately by methods based on the reversed-phase HPLC separation of diastereomeric derivatives or the HPLC separation of enantiomeric derivatives on chiral stationary phases. In general, B. subtilis protease yielded better results than A. oryzae protease. Using the former protease, the amino acids bearing aliphatic side chains were resolved with good to excellent enantioselectivities and reasonable hydrolysis rates. The speed of hydrolysis was reduced significantly when the length of the side chain was longer than 5 carbon atoms. Phenylalanine, halogenated phenylalanines, and phenylalanine homologs were also resolved, generally with high enantiomeric purities, though the hydrolysis rates were not always reasonably fast. In all the cases examined, the L-enantiomers were preferentially hydrolyzed as in the lipase-catalyzed enantioselective hydrolysis reported previously. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040705
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    Resolution and adrenergic activities of the optical isomers of 4-[1-(1-Naphthyl)ethyl]-1H-imidazole (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 432-438 
    Details
    ISSN: 0899-0042
    Keywords: α-adrenergic ; imidayole analogs ; metetomidine ; enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently we synthesized a naphthalene analog of medetomidine, 4-[1-(1-naphthyl)ethyl]-1H-imidazole hydrochloride (1), and found it to be highly potent in adrenergic systems. The separation of optical isomers of this naphthalene analog was achieved by using the isomers of tartaric acid. The optical purities of the isomers were determined by HPLC using a chiral column. Using X-ray analysis the (+)-isomer was determined to have the S absolute configuration. It has been reported that the (+)-isomer of medetomidine (2) is the most potent enantiomer on α2-adrenergic receptors. There were both qualitative and quantitative differences in biological activities of the optical isomers of 1 in α1- and α2-adrenergic receptor systems of guinea pig ileum and human platelets. (+)-(S)-1, but not ( - )-(R)-1 was a selective agonist of α2-mediated responses in ileum whereas ( - )-(R)-1 was more potent than (+)-(S)-1 as an inhibitor of α2-mediated platelet aggregation. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040706
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    Announcement (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 462-463 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040711
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    Optical stability of gossypol (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 216-221 
    Details
    ISSN: 0899-0042
    Keywords: atropisomerism ; gossypol stereochemistry ; molecular mechanics ; circular dichroism ; anhydrogossypol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical stability of gossypol [1,1',6,6',7,7'-hexahydroxy-3,3'-dimetyl-5,5'-bis(1-methylethyl)-2,2'-binaphthalene-8,8'-dicarboxaldehyde], a natural product exhibiting profoundly enantiospecific antitumor and male antifertility action, was investigated by means of computational methods and thermal racemization experiments. The calculations on gossypol and several derivatives and model compounds were carried out using the MM2 force field; energies and geometries of minimum energy conformations, as well as structures along various inversion pathways, were calculated. According to the calculations, gossypol (the dialdehyde form) and its simple analogues are not thermally racemizable (energy barriers for rotational inversion above 50 kcal/mol). By contrast, the calculations suggest that the acetal tautomer of gossypol and its dehydration product (anhydrogossypol) are thermally racemizable, although the energy barriers are still relatively high (35-40 kcal/mol). Optically pure (+)-anhydrogossypol was prepared and characterized; its racemization became rapid only at high temperatures (180-200°C). When dehydration of gossypol was hindered (in aqueous solution), no racemization of gossypol was observed after prolonged heating at 90°C. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040403
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    Synthesis and pharmacological investigation of stereoisomeric muscarines (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 230-239 
    Details
    ISSN: 0899-0042
    Keywords: total synthesis ; chiral muscarines ; iodocyclization process ; muscarinic receptor subtypes M1, M2, and M3 ; affinity states ; eudismic ratio ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the eight stereoisomers of muscarine has been efficiently accomplished by utilizing the two enantiomers of lactic esters as starting material. The synthetic strategy is based on a SnCl4-catalyzed addition of allyltrimethylsilane to O-protected lactic aldehydes followed by an iodocyclization process. All the final derivatives possess an enantiomeric excess higher than 98%. The four pairs of enantiomers bound to M1, M2, and M3 muscarinic receptor subtypes in membranes from cerebral cortex, heart, and salivary glands, respectively, and recognized heterogeneous states of the receptors. Of the eight isomers, only natural muscarine (+)-1 recognized three affinity states of the M2 receptor. The compound was also the only one to show selectivity in the binding study, demonstrating 37- to 44-fold higher affinity for the M2 than for the M1 or M3 receptors. In addition, the compounds were tested in functional assays on isolated guinea pig atria (M2 receptors) and ileum (mixed population of M2 and M3 receptors) and their muscarinic potencies were determined. Among the eight isomers, again only (+)-1 enantiomer was found to be very active on both tissues. Its potency was more than two orders of magnitude higher than that of its enantiomer (-)-1 as well as the other six isomers. The eudismic ratios (E.R.) deduced from the two functional tests were 324 and 331. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040406
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    Discrimination in resolving systems: Ephedrine-mandelic acid (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 494-504 
    Details
    ISSN: 0899-0042
    Keywords: diastereomers ; crystal structures ; isosterism ; organic salts ; molecular recognition ; hydrogen bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Resolution of mandelic acid with ( - )-(1R,2S)-ephedrine in water and ethanol produces intermediate diastereomeric salts with greatly disparate solubilities and melting points. Single crystal X-ray analysis of the less (L) and more (M) soluble ( - )-ephedrinium mandelates (I, II) shows crystal structures which are isosteric, each crystallizing in the monoclinic system, space group C2. Protonated ephedrines occupy the same relative positions in the L- and M-salts, and mandelates are in the same general locations. Hydrogen bonds link alternating protonated ephedrine nitrogens and mandelate carboxylate oxygens in each salt forming columns of ions. The helical H-bonded chain winds down the crystallographic 2-fold screw axis. Additional H-bonds form between 2-fold related mandelates in the L-salt. Mixed crystals, containing both mandelate isomers, (2R)- and (2S)-mandelates, are obtained from the resolving system partly depleted of the L-salt. A specimen with nearly equal amounts of the mandelates (III) is also isosteric with the commensurate structures. I (294K), L-salt: a = 18.160(7), b = 6.538(2), c = 13.898(4) Å, β = 92.02(3)°, V = 1649.1(9) Å3; IIa (294K), M-salt: a = 17.978(11), b = 7.164(4), c = 13.574(6)Å, β = 96.41(4)°, V = 1737.3(16) Å3; IIb (223K), M-salt: a = 17.805(8), b = 7.115(2), c = 13.50(5) Å, β = 96.89(3)°, V = 1697.9(15) Å3; III (294K), mixed-salt: a = 18.184(22), b = 6.792(7), c = 13.808(19) Å, β = 93.74(10)°, V = 1701.7(35) Å3. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040807
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    High enantiofacial selectivity in the OsO4 dihydroxylation of e-stilbene with a chiral biphenyl diamine catalyst (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 300-301 
    Details
    ISSN: 0899-0042
    Keywords: hydrobenzoin ; asymmetric oxidation ; osmium tetroxide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiral biphenyl-containing diamine 1 complexed with OsO4 oxidized trans-stilbene at -80°C to (+)-(1R;2R)-1,2-diphenyl-1,2-ethanediol in high enantiomeric excess. On the other hand, (R)- or (S)-2,2'-bis(dimethylamino)-6,6'-dimethylbiphenyl proved to be ineffective in promoting oxidation. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040507
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    Enantio- and regioselectivity in the epoxide-hydrolase-catalyzed ring opening of aliphatic oxiranes: Part II: Dialkyl- and trialkylsubstituted oxiranes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 185-192 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; regioselective hydrolysis ; epoxide hydrolase ; product enantioselectivity ; substrate enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent of substrate enantioselectivity and regioselectivity of a series of aliphatic 2,3-dialkyl- and trialkylsubstituted oxiranes in their in vitro epoxide-hydrolase-catalyzed hydrolysis depends on the size of the alkyl residues and on the substitution pattern of the oxirane ring. The enzyme-catalyzed hydrolysis of cis-oxiranes, containing at least one methyl substituent, shows complete or nearly complete substrate enantioselectivity and regioselectivity with nucleophilic attack by water occurring with inversion of configuration at the methylsubstituted ring carbon atom of (S)-configuration. In the hydrolysis of the isomeric trans-oxiranes, both enantiomers are metabolized with a higher rate for the (2S;3S)-enantiomer. The conversion of trimethyloxirane occurs with high substrate enantioselectivity in favor of the (S)-enantiomer and with complete regioselectivity at the monomethylsubstituted ring carbon atom. The differentiation of the enantiotopic ring carbon atoms (product enantioselectivity) in the smallest aliphatic meso-oxirane, cis-2,3-dimethyloxirane, leads to (2R;3R)-butane-2,3-diol with ee = 86%. cis-2-Ethyl-3-propyloxirane, possessing alkyl residues larger than methyl, represents an extremely poor substrate in the epoxide-hydrolase-catalyzed hydrolysis process. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040310
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    Structural characteristics of cyclodextrins in the solid state (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 205-215 
    Details
    ISSN: 0899-0042
    Keywords: cyclodextrins ; molecular mechanics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comparison of α-, β and γ-cyclodextrins in the solid state is made. Monomeric features analyzed include orientations of primary hydroxyl groups and pyran ring pucker. Macromolecular features examined include planarity of the oligomer, tilting of pyran rings, and, deviation from Cn symmetry where n = number of monomers. The mean values and standard deviations of these shape descriptors are given for cyclodextrins with and without guests embedded in their interiors. Molecular mechanics calculations using the MM2, AMBER, and CHARMM force fields show that most solid state cyclodextrins are trapped in high-energy conformations relative to the most stable forms found in this study. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040402
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    Enzymes in stereoselective pharmacokinetics of endogenous substancesPresented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 247-251 
    Details
    ISSN: 0899-0042
    Keywords: radioenzyme assay ; stereospecific assay ; carnitine acetyl transferase ; L-carnitine family ; L-carnitine ; acetyl-L-carnitine ; propionyl-L-carnitine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of enzymes to assay individual components of the L-carnitine family in pharmaceuticals, foodstuffs, and biological fluids with various forms of detection is reviewed. The most useful enzyme in the assay of compounds of the L-carnitine family is carnitine acetyl transferase (CAT), which catalyses the reversible interconversion of L-carnitine and its short-chain acyl esters. CAT can be used in one or more coupled reactions combined with U.V., or radiolabelled detection, or combined with HPLC, allowing, enantioselective, structurally specific, and, in the case of radiolabelled tracing, highly sensitive assays to be carried out. When compared with chromatographic separation of enantiomers or diastereoisomers, enantioselective enzyme mediated assays may be cheaper, more sensitive, and simpler, but they do not allow the nonpreferred isomer to be assayed. Consequently, they are appropriate for the specific assay of endogenous enantiomeric substrates of the enzyme concerned, in biological samples. The analysis of the other enantiomer in raw materials or in pharmaceuticals must be more properly approached by enantioselective chromatographic methods.
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    Direct enantiomeric separation of β-blockers on ChyRoSine-a by supercritical fluid chromatography: Supercritical carbon dioxide as transient in situ derivatizing agent (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 252-262 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phases ; tyrosine chiral selector ; supercritical fluid chromatography ; 1,2-amino-alcohols ; β-blockers ; carbon dioxide ; 1H NMR ; ChyRoSine CSP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct enantiomeric separation of a series of β-blockers has been carried out on two chiral stationary phases (CSPs) derived from 3,5-dinitrobenzoyl tyrosine: the commercially available ChyRoSine-A and a recent improved version of this CSP.Using supercritical fluid chromatography (SFC), facile separations are achieved (1.1 〈Rs 〈7) within short analysis times. The parameters affecting the enantioselectivity (temperature, pressure, mobile phase nature, solute structure) have been investigated. The optimal mobile phase consists in a mixture of carbon dioxide-methanol-propylamine at 25°C. The solute structure has a great influence on the enantioselectivity. For instance, both amine and hydroxyl protons are necessary for chiral discrimination to occur. Furthermore, the steroselectivity value is directly connected to the amine substituent steric bulkiness.Surprisingly, these solutes are poorly resolved using normal phase liquid chromatography (NPLC). Accordingly, the specific influence of carbon dioxide on the enantiomeric separation of 1,2-amino-alcohols has been investigated using various techniques such as nuclear magnetic resonance (NMR) or molecular modelisation. It has been shown that carbon dioxide acts as a complexing agent toward the amino-alcohol by setting up of a bridge with the hydroxyl and the amine protons of the solute. In that way, the resulting complex possesses lower acido-basic properties and a higher conformational rigidity, responsible for chiral discrimination.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040409
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    A proposal for the representation of the stereochemistry of quadrivalent centers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 274-278 
    Details
    ISSN: 0899-0042
    Keywords: one-wedge diagram ; structure representation ; stereochemistry ; absolute configuration ; chiral center ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The broken wedge, broken line, solid bar, and broken bar are either not reasonable or can be replaced by only one type of solid wedge in the stereochemical formulation. A convention based on a one-wedge symbolization is proposed, where a or b is used instead of c, d, e, f, g, or h. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040503
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    Asymmetric synthesis polymerization of meso oxiranes and thiiranesThis work is dedicated to the memory of Professor Piero Pino. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 295-299 
    Details
    ISSN: 0899-0042
    Keywords: cis-dimethylthiirane ; cyclohexene sulfide ; cis-dimethyloxirane ; cyclohexene oxide ; chiral initiator system ; enantiogenic polymerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The asymmetric synthesis polymerization or “enantiogenic” polymerization of some meso oxiranes, cis-dimethyloxirane (cis-DMO) and cyclohexene oxide (CHO), and thiiranes, cis-dimethylthiirane (cis-DMT) and cyclohexene sulfide (CHS), initiated with different chiral systems was examined. Strong differences in behaviour were observed between oxiranes and thiiranes depending on the initiator used. The initiators based on ZnEt2 or CdMe2 and a chiral diol give optically active polymers from meso thiiranes but fail to induce an asymmetric polymer synthesis with meso oxiranes. A new chiral initiator based on ZnEt2 and (1S,2R)-ephedrine allowed us to prepare optically active poly CHOs, which can be fractionated into fractions exhibiting opposite optical activities. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/chir.530040506
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    Computer-Aided models for optimization of eluent parameters in chiral liquid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 316-322 
    Details
    ISSN: 0899-0042
    Keywords: chiral LC ; drug enantiomers ; modelling ; central composite desire ; optimization ; β-cyclodextrin ; response surface ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of a central composite design to the enantiomeric separation of the antifungal drug tioconazole is investigated. The design involves application of a mathematical model to the data to model the response in regions of the factor space not investigated in the experimental design. The significance of the variable terms in the model is assessed statistically and those terms declared not significant are removed from the model. The statistical adequacy of these reduced models is discussed, together with an examination of the prediction errors of the models. Three-dimensional predicted response surfaces for the complete models are presented and the predictive performance assessed. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040510
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    Resolution of the enantiomers of drugs containing amino alcohol structure after derivatization with bromoacetic acid (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 333-337 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; ligand exchange chromatography ; adrenergic drugs ; β-blockers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The separation of the enantiomers of drugs containing an amino alcohol structure like adrenergic drugs or β-blockers is described. The compounds are resolved on chiral ligand-exchange chromatography phases after derivatization with bromoacetic acid. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040512
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040601
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    Optical isomers of a leukotriene b4 antagonist have differential effects on granulocyte diapedesis in the guinea pig dermis (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 353-355 
    Details
    ISSN: 0899-0042
    Keywords: leukotriene B4 ; SC-41930 ; dermis ; granulocyte ; stereoselectivity ; guinea pig ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Leukotriene B4 (LTB4) is a proinflammatory product of arachidonic acid metabolism that has been implicated in a number of inflammatory diseases. When injected intradermally into the guinea pig, LTB4 has been shown to elicit a dose-dependent infiltration of granulocytes as assessed by the level of the neutrophil marker enzyme myeloperoxidase. SC-41930 [7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy]-3,4-dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid] is a potent LTB4 receptor antagonist. When compounds were coadministered along with LTB4 (35 ng) into the dermal site, racemic SC-41930, (+)-SC-41930, and (-)-SC-41930 each inhibited granulocyte accumulation with ED50 values of 340 ± 30, 98 ± 5.7, and 1000 ± 142 ng, respectively; when given intravenously inhibited with ED50 values of 0.5 ± 0.06, 0.3 ± 0.04, and 1.4 ± 0.19 mg/kg, respectively; and when given intragastrically inhibited with ED50 values of 1.7 ± 0.20, 1.4 ± 0.23, and 3.0 ± 0.41 mg/kg, respectively. © 1992 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040605
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    Stereoselective binding and activity of oxotremorine analogs at muscarinic receptors in rat brain (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 463-468 
    Details
    ISSN: 0899-0042
    Keywords: muscarinic receptors ; oxotremorine derivatives ; stereoselectivity ; adenylyl cyclase ; phosphoinositide metabolism ; receptor autoradiography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The activities of the enantiomers of BM-5 were examined to measure muscarinic cholinergic selectivity in the central nervous system. Autoradiographic studies assessed the ability of each enantiomer to inhibit the binding of [3H]-(R)-quinuclidinyl benzilate ([3H]-(R)-QNB) to muscarinic receptors in the rat brain. (+)-(R)-BM-5 inhibited [3H]-(R)-QNB binding to rat brain sections at concentrations below 1.0 μM, while 100-fold higher concentrations of ( - )-(S)-BM-5 were required for comparable levels of inhibition. Analysis of the autoradiograms indicated that both stereoisomers had a similar distribution of high affinity binding sites. Each enantiomer displayed higher affinity for muscarinic receptors in the superior colliculi and lower affinity for receptors in the cerebral cortex and hippocampus. (+)-(R)-BM-5 and oxotremorine inhibited adenylyl cyclase activity in the cerebral cortex with efficacies comparable to that for acetylcholine. (+)-(R)-BM-5 was 26-fold more potent than ( - )-(S)-BM-5 in inhibiting adenylyl cyclase. Oxotremorine-M and carbamylcholine stimulated phosphoinositide turnover in the cerebral cortex. Oxotremorine had lower activity and (+)-(R)-BM-5 was essentially inactive at comparable concentrations. The difference in activity of the two enantiomers indicates a remarkable stereochemical selectivity for muscarinic receptors. The stereoselectivity index is comparable for both the autoradiographic assays (48) and measures of adenylyl cyclase activity (26) in the cerebral cortex. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040802
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    Measurement of the (R)- and (S)-isomers of warfarin in patients undergoing anticoagulant therapy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 488-493 
    Details
    ISSN: 0899-0042
    Keywords: achiral/chiral coupled HPLC ; α1-acid glycoprotein column ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An achiral/chiral high-performance liquid chromatographic system for the analysis of total warfarin together with the (R)- and (S)-enantiomers in clinical samples has been developed. The achiral analysis is achieved using a C8 column, which is coupled to a chiral stationary phase, α1-acid glycoprotein (AGP), thereby allowing for analysis of warfarin isomers without interfering serum peaks. A 0.015 M phosphate buffer mobile phase with 15% v/v propan-2-ol (pH 7.0) was used on the C8/AGP system. UV analysis at 308 nm was used for quantitation of total warfarin on the C8 column and fluorescence (excitation 300 nm, emission 390 nm) detection was employed for isomer quantitation on the AGP. Retention time of total warfarin on the C8 column was 5.95 min, while that of the (S)- and (R)-warfarin on the AGP column was 10.38 and 12.69 min, respectively. Peak resolution of the warfarin isomers was 1.64. All serum samples were subjected to solid-phase extraction. Data from two patients in a single dose study indicate that a two-compartmental model could represent the warfarin concentration - time data with enterohepatic circulation. In some patients studied during steady state therapy, concentrations of (S)-warfarin were greater than (R)-warfarin indicating that the clearance of the former is slower in these patients. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040806
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    Announcement (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 521-521 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040811
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    Resolution and stability of oxazepam enantiomers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 443-446 
    Details
    ISSN: 0899-0042
    Keywords: oxazepam ; chiral stationary phases ; high-performance liquid chromatography ; enantiomer separation ; enantiomer stability ; racemization ; kinetics of racemization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A solvent mixture containing dioxane, acetonitrile, and hexane was found to be suitable as a mobile phase to resolve oxazepam enantiomers by chiral stationary phase high performance liquid chromatography using covalent Pirkle columns. The resolved oxazepam enantiomers in this solvent mixture had a racemization half-life greater than 3 days at 23°C. When desiccated at 0°C as dried residue, OX enantiomers were stable for at least 50 days with less than 2% racemization. The conditions which stabilized OX enantiomers significantly facilitated the determination of racemization half-lives of OX enantiomers in a variety of aqueous and nonaqueous solvents and at different temperatures. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040708
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040801
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    Cytochrome p-455 nm complex formation in the metabolism of phenylalkylamines. XII. Enantioselectivity and temperature dependence in microsomes and reconstituted cytochrome p-450 systems from rat liver (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 469-477 
    Details
    ISSN: 0899-0042
    Keywords: metabolic intermediate (MI) complex ; amphetamine ; 1-phenyl-2-pentanamine ; N-hydroxyamphetamine ; 2-nitroso-1-phenylpropane ; P450 2B1 ; P450 2C11 ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formation of metabolic intermediate (MI) complexes was studied with the enantiomers of amphetamine, 1-phenyl-2-pentanamine, N-hydroxyamphetamine, and 2-nitroso-1-phenylpropane (the C-nitroso analogue of amphetamine). Three different enzyme systems were used; liver microsomes from phenobarbital pretreated rats and two reconstituted systems containing the P450 2B1 and P450 2C11 forms of cytochrome P-450. Enantioselective complex formation in microsomes was shown for the amines and the nitroso compound, but not for the hydroxylamine. The highly purified P450 2B1 system formed the MI complex with all substrates tested, and the enantioselectivity observed with the microsomal system was reproduced. In the P450 2C11 system the nitroso compounds were completely inactive, whereas the enantiomers of N-hydroxyamphetamine still produced the complex at a high rate. Changes in temperature were shown to affect (R)-2-nitroso-1-phenylpropane more than its enantiomer. Both enantiomers showed biphasic Arrhenius plots for MI complex formation in microsomes (breaks around 22°C), but the activation energies of the (R)-isomer were about five times higher than those of the (S)-isomer. A theory is presented which suggests different modes of interaction with the active site of P-450 to account for the different behaviour of the various substrates. © 1992 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040803
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040101
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  • 75
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    Stereoselective aliphatic hydroxylation of 6-n-propylchromone-2-carboxylic acid by female Dutch rabbits (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 1-7 
    Details
    ISSN: 0899-0042
    Keywords: product enantioselectivity ; aliphatic hydroxylation ; 6-n-propylchromone carboxylic acid ; chiral HPLC ; chiral shift 1H-NMR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 6-n-Alkylchromone-2-carboxylic acids are metabolized solely by aliphatic oxidation. In the rabbit, the 6-n-propyl congener (PCCA) undergoes ω-1 hydroxylation exclusively. Following administration of PCCA to female Dutch rabbits (500 μmol/kg), some 77% of the dose was excreted in the urine, 41% as PCCA and 36% as 6-(2'-hydroxy-n-propyl)chromone-2-carboxylic acid. Since this metabolite is chiral, we have examined the stereochemistry of the excreted material. Diastereoisomeric (as camphanate and α-methoxy-α-(trifluoromethyl)phenylacetate esters) and direct chiral HPLC and chiral lanthanide shift NMR have each shown the S:R ratio of the excreted metabolite to be 76:24. When rabbits were dosed with the racemic metabolite, excretion of the compound was not stereoselective. The regio- and stereo-selectivity of the aliphatic hydroxylation of PCCA are thus reflections of the selectivities of the enzyme systems responsible for its formation and suggest PCCA to be an appropriate probe compound for the study of prochiral-chiral hydroxylations.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040103
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    Enantiospecificity of kappa receptors: Comparison of racemic compounds and active enantiomers in two novel series of kappa agonist analgesics (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 8-15 
    Details
    ISSN: 0899-0042
    Keywords: opioids ; piperidines ; 1,2,3,4-tetrahydroisoquinolines ; antinociception ; binding affinity ; QSAR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two novel series, Ia,b and IIa,b, of kappa opioid antinociceptive agents have recently been described. 2a,b,3a,b,c The biological activities of 16 racemic compounds and their corresponding (-) enantiomers are now compared in a battery of tests. Enantiomers of unsubstituted piperidines Ia were synthesized starting from S(-) pipecolic acid, whereas the enantiomerically pure substituted piperidines (Ib), tetrahydroisoquinolines (IIa), and thienopiperidines (IIb) were, in general, obtained after diastereomeric crystallization of the corresponding tartrate salts. The absolute stereochemistry of one representative enantiomer from series IIa was determined to be (1S) by X-ray crystallographic analysis. Antinociceptive activity in the mouse abdominal constriction and tail-flick tests following subcutaneous administration, and binding affinity for κ and μ receptors, were found to reside predominantly in the (-) enantiomers. Consequently, racemic compounds showed approximately half potency of the corresponding enantiomers. This potency difference was less clear after oral administration presumably due to small differences in bioavailability of the two corresponding enantiomers.For compounds with some affinity also for μ receptors (Ki 〈1,000 nM), the κ/μ selectivity was maintained within each enantiomeric pair, in contrast to results found for other κ agonists.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040104
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    Chiral discriminations with cinchona alkaloids (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 43-49 
    Details
    ISSN: 0899-0042
    Keywords: chiral discrimination ; enantiomeric separation ; chiral solvating agents ; asymmetric synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040110
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    Enantioselective chromatography of the antimalarial agents chloroquine, mefloquine, and enpiroline on a α1 -acid glycoprotein chiral stationary phase: Evidence for a multiple-site chiral recognition mechanism (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 30-35 
    Details
    ISSN: 0899-0042
    Keywords: chiral liquid chromatography ; α1 -acid glycoprotein ; antimalarial agents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of mobile phase pH and dimethyloctylamine (DMOA) on the retention (k') and stereoselectivity (α) of antimalarial agents mefloquine, enpiroline, and chloroquine on the α1-acid glycoprotein chiral stationary phase (AGP-CSP) was investigated. An increase of k' with increasing pH was observed while the effect on α was a function of the solute. The magnitude and direction of changes induced by DMOA depended on pH and the structure of the solute.The results of this study are consistent with a change of the conformation of the AGP between pH 5 and 7. At pH 7, the effect of DMOA on mefloquine was relatively well described by a competitive displacement from one enantioselective site. The effect on chloroquine and enpiroline suggests a multiple-site mechanism in which both competitive and allosteric interactions are involved.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040108
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    Preparation of α-substituted α-amino acids of high enantiomeric purity (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 302-307 
    Details
    ISSN: 0899-0042
    Keywords: hydantoin derivatives ; chiral isocyanates ; LC separation of diastereomers ; preparative LC separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic 5,5-dialkyl hydantoins derived from ketones are resolved by preparative liquid chromatography as the diastereomeric 1-carboxamide derivatives afforded by the reaction with optically pure configurationally known α-phenylethyl isocyanate. Hydrolysis of the resolved diastereomers affords α-substituted α-amino acids of high enantiomeric purity. The synthetic route is short, overall yields are high, and the absolute configuration of the amino acid enantiomers may be deduced from the chromatographic and NMR properties of the diastereomers. © 1992 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040508
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    Application of antibody-mediated extraction for the stereoselective determination of the active metabolite of loxoprofen in human and rat plasma (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 308-315 
    Details
    ISSN: 0899-0042
    Keywords: loxoprofen ; 2-arylpropionic acid ; active metabolite ; immobilized antibody column ; chiral hapten ; diastereomeric derivatization ; chiral inversion ; stereoselective ketone reduction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antibody-mediated extraction followed by chiral high-performance liquid chromatography (HPLC) was applied to stereoselective determination in human and rat plasma of the active metabolite [(2S,1]R,2[S)-trans-alcohol] with three chiral centers of Loxoprofen, a 2-arylpropionic acid antiinflammatory agent after oral administration. Antiserum against the (1'R,2'S)-cyclopentanol moiety was obtained from a rabbit immunized with bovine serum albumin conjugate linked to the propionic acid moiety, in which another chiral center is located. Then, the immunoglobulin G purified by a protein A column was coupled to BrCN-activated Sepharose 4B. Plasma samples were applied to the immobilized antibody column. After washing the column to remove unrequired stereoisomers, a mixture of two diastereomers whose configurations were 1'R,2'S in the cyclopentanol moiety was extracted with 95% methanol. The solvent was evaporated and the residue was derivatized with (+)-(R)-1-(1-naphthyl)ethylamine as a chiral reagent to separate the diastereomers by HPLC. This combined analytical method showed the stereoselective metabolism of Loxoprofen in human, that is, 64% of the total amount of four trans-alcohol stereoisomers was in the 2S, 1'R,2'S form, which is the active metabolite. This phenomenon was also observed in rats given Loxoprofen and its (2S)- and (2R)-isomers, and is explained by stereoselective ketone reduction of Loxoprofen to the (1'R,2'S)-trans-alcohol and inversion from 2R to 2S in the propionic acid moiety. Antibody-mediated extraction should be a selective and simple clean-up method for determining haptens with complicated structures, combined with an appropriate analytical method. © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040509
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    Editorial (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. i 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040102
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    Stereoselectivity at α-adrenoreceptor subtypes: observations with the enantiomers of WB 4101 separated through their amides of N-Tosyl-(S)-proline (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 16-20 
    Details
    ISSN: 0899-0042
    Keywords: optical resolution ; enantioselectivity ; chromatography ; dissociation constants ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a chromatographic method for the separation and determination of the optical purity of the enantiomers of WB 4101 [(±)-1], one of the most potent and selective α1-adrenoreceptor antagonists. (±)-1 was converted into the amide of N-tosyl-(S)-proline. The two diastereoisomers were separated on silica gel and analysed by HPLC reversed phase. The analytical method described is both accurate and sensitive and allows the optical purity to be determined at very low concentrations and to obtain WB 4101 enantiomers with a purity of more than 99.95%.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040105
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    Stereoselective effect of phenprocoumon enantiomers on the binding of benzodiazepines to human serum albumin (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 21-23 
    Details
    ISSN: 0899-0042
    Keywords: protein binding ; affinity chromatography ; resolution ; allosteric interaction ; increased enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of phenprocoumon enantiomers on the stereoselective binding of 3-substituted 1,4-benzodiazepines to human serum albumin (HSA) was studied by chromatography on HSA-Sepharose column. (S)-Phenprocoumon exerts stereoselective allosteric interaction on the binding of benzodiazepines. The structural requirements of enhanced stereoselectivities are similar to those found previously with (S)-warfarin.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040106
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    Improvement of the enantiorecognition ability of tyrosine-derived chiral stationary phases: Direct resolution of 1,2-amino-alcohols (β-blockers) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 36-42 
    Details
    ISSN: 0899-0042
    Keywords: tyrosine chiral selector ; enantiomeric separations ; chiral stationary phases ; HPLC ; subFC ; β-blockers ; 1,2-amino-alcohols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel chiral stationary phase (CSP) derived from tyrosine is evaluated with regard to the first generation commercially available (S)-ChyRoSine-A CSP, under normalphase or reversed-phase liquid chromatographic (NPLC or RPLC) and subcritical fluid chromatographic (SubFC) conditions. The complete scope of application of these CSPs is reviewed. The novel CSP, which bears a bulkier functional group, displays a higher enantiorecognition ability than previously described (S)-ChyRoSine-A toward about 15 families of racemates, whatever the mobile phase conditions.The direct enantiomeric separation of 1,2-amino-alcohols (β-blockers) is carried out on both CSPs. Facile separations are achieved within short analysis times using SubFC mode, whereas very poor separations are obtained using NPLC mode. These results disagree with previous theories (interchangeability between NPLC and SubFC modes).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040109
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  • 85
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    Use of cyclodextrins in capillary zone electrophoresis for the separation of optical isomers: Resolution of racemic tryptophan derivatives (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 56-61 
    Details
    ISSN: 0899-0042
    Keywords: capillary zone electrophoresis ; enantiomers ; cyclodextrins ; tryptophan derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this study capillary zone electrophoresis has been used for the separation of racemic tryptophan derivatives in their enantiomers. The effect of cyclodextrins with different shape, added to the background electrolyte, on the migration time of 10 compounds, including methyl tryptophan, hydroxy tryptophan, and tryptophan ester derivatives, has been studied. Furthermore, the effect of cyclodextrins with different shape and that of the composition of the background electrolyte on the enantiomer resolution are discussed. Among different cyclodextrins used α-cyclodextrin and heptakis(2,6-di-O-methyl)-β-cyclodextrin were found to possess the best complexing capacity and thus the resolution power toward analysed compounds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040112
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  • 86
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    Letter to the editors: Rootworm pheromones: The root of a stereochemical mixup (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 68-70 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040115
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  • 87
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    The influence of aging on the stereoselective pharmacokinetics of propranolol in the rat (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 73-79 
    Details
    ISSN: 0899-0042
    Keywords: aging ; β-adrenergic blocking agent ; enantiomers ; propranolol ; protein binding ; stereoselective pharmacokinetics ; tissue binding ; tissue concentrations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of aging on the pharmacokinetics and the tissue distribution of (R)- and of (S)-propranolol was studied in 3-, 12-, and 24-month-old rats. After both iv and oral administration of rac-propranolol, the plasma concentrations were higher for the (R)- than for the (S)-enantiomer. For the tissue concentrations, the reverse was true. The free fraction of (S)-propranolol in plasma was about 4 times larger than that of (R)-propranolol, and this is the main factor responsible for the differences in kinetics between the two enantiomers. There was a suggestion for a difference in tissue binding between the two enantiomers. With aging, the plasma and tissue concentrations of both enantiomers increase, probably due to a decrease in blood clearance. Tissue binding did not change much with aging. Notwithstanding the marked differences between the kinetics of the propranolol enantiomers, the changes which occur with aging affect both enantiomers to the same degree.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040202
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  • 88
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    The disposition of venlafaxine enantiomers in dogs, rats, and humans receiving venlafaxine (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 84-90 
    Details
    ISSN: 0899-0042
    Keywords: high-performance liquid chromatography (HPLC) ; chiral assay ; naproxen chloride ; pharmacokinetics ; racemate ; stereoselective ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereospecific high-performance liquid chromatographic (HPLC) method was developed for the quantitation of the enantiomers of venlafaxine, an antidepressant, in dog, rat, and human plasma. The procedure involves derivatization of venlafaxine with the chiral reagent, (+)-S-naproxen chloride, and a postderivatization procedure. The method was linear in the range of 50 to 5,000 ng of each enantiomer per ml of plasma. No interference by endogenous substances or known metabolites of venlafaxine occurred. Studies to characterize the disposition of the enantiomers of venlafaxine were conducted in dog, rat, and human, following oral administration of venlafaxine. The Cmax, area under the curve (AUC) and (S)/(R) concentration ratios of the (R)- and (S)-enantiomers were compared. In rats, the mean plasma ratio of (S)-venlafaxine to that of (R)-venlafaxine over 0.5 to 6.0 h varied from 2.97 to 8.50 with a mean value of 5.51 ± 2.45. The Cmax, AUC0 - ∞, and t1/2 values of the (R)- and (S)-enantiomers in dogs were not significantly different from one another (P〉0.1). The mean ratios [(S)/(R)] of enantiomers of venlafaxine in human over a 2 to 6 h interval ranged from 1.33 to 1.35 with an overall ratio of 1.34 ± 0.26 (n = 12). These ratios of the enantiomers [(S)/(R)] were not statistically different from unity (P〉0.1) indicating that the disposition of venlafaxine enantiomers in humans is not stereoselective and is more similar to that in dogs than that in rats.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040204
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  • 89
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    Unusual amino acids I: Asymmetric synthesis of furylalanine derivatives (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 110-115 
    Details
    ISSN: 0899-0042
    Keywords: furyldehydroamino acid ; enantioselectivity ; hydrogenation ; chiral rhodium complexes ; amino-phosphine-phosphinite ; ligands enantiomers ; (R)- and (S)-isomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nonproteinogenic amino acids are valuable active compounds from their pharmacological and biochemical effects and also as novel building blocks for peptides. The preparation of furylalanine derivatives by asymmetric hydrogenation is described. Amino-phosphine-phosphinite-rhodium complexes catalyzed the hydrogenation of the prochiral dehydroamino acid precursors in high rate and with enantioselectivities of 70 - 90% ee. Substrate-catalyst ratios up to 2,000 can be used depending on the catalyst applied. The procedure turns out to be suitable for larger scale preparations.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040208
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  • 90
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    Effective methods for enantioselective analysis of glycidol derivatives by liquid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 132-135 
    Details
    ISSN: 0899-0042
    Keywords: sharpless asymmetric epoxidation ; chiral epoxide ; carbamate ; tin(IV) ; catalysis ; 4-hydroxy-2,3-epoxybutyrates ; Chiralcel OD ; Chiralcel® OB ; Zorbax® NH2 ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methodology for determination of the enantiomeric purity of sixteen 2,3-epoxy-1-propanols (glycidols) is delineated. Conversion of these epoxy alcohols and 1-naphthyl isocyanate (NIC) into the 1-naphthyl carbamates is catalyzed by dibutyltin diacetate. Enantiomers of these carbamates are resolved on a Chiralcel® OD column. Advantages of this method include mildness of reaction conditions, nonreliance on diastereomeric derivatization, and appendage of a UV-absorbing chromophore to the analyte.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040212
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  • 91
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    The effect of the enantiomers of ibuprofen and flurbiprofen on the β-oxidation of palmitate in the rat (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 137-141 
    Details
    ISSN: 0899-0042
    Keywords: 2-arylpropionic acids ; nonsteroidal antiinflammatory drugs ; stereoselective ; coenzyme A thioesters ; chiral inversion ; oxidative phosphorylation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of the enantiomers of ibuprofen (0.25 and 0.50 mmol/kg b.w.) and flurbiprofen (0.01, 0.03, and 0.06 mmol/kg b.w.) on the β-oxidation of palmitate were investigated in the rat. The mean cumulative exhalation of 14CO2 after ip administration of [U-14C]palmitic acid was significantly reduced over 6 h by ibuprofen at the higher dose but not at the lower dose for either enantiomer. There was no difference between the enantiomers, the reduction over 6 h being 31.3 and 33.0% for (R)- and (S)-ibuprofen, respectively. There was also a significant inhibition of β-oxidation by flurbiprofen at all 3 doses. Again, there was no stereoselectivity evident in this inhibition. Flurbiprofen was much more potent than ibuprofen in eliciting this effect, the 0.01mmol/kg dose giving a similar reduction in β-oxidation as observed for the 0.50 mmol/kg dose of ibuprofen. The data support the hypothesis that inhibition of the in vivo β-oxidation of palmitate by ibuprofen and flurbiprofen is primarily via a nonstereoselective noncoenzyme A-dependent mechanism. © 1992 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040302
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  • 92
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    Enantioselective pharmacokinetics of ethotoin in humans following single oral doses of the racemate (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 142-147 
    Details
    ISSN: 0899-0042
    Keywords: anticonvulsants ; epilepsy ; stereoisomers ; hydantoins ; metabolism ; HPLC assay ; chiral columns ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic ethotoin (1000 mg) was administered orally as a single dose to six healthy adult volunteers. Blood samples were collected at appropriate times for 120 h following the dose. Ethotoin was quantified enantioselectively in plasma using a novel chiral column HPLC procedure. One of the enantiomers of the chiral metabolite, 5-phenylhydantoin, was also quantified in the HPLC method. The Cmax and AUC0 - ∞ values for (+)-(S)-ethotoin were significantly greater than those for ( - )-(R)-ethotoin (ratio of mean AUC0 - ∞ values 0.88), but the elimination half-lives of the isomers were virtually identical [12.35 ± 5.15 h for ( - )-(R)-thotoin; 12.28 ± 5.34 h for (+)-(S)-ethotoin]. Parameters derived from AUC0 - ∞ (Cl0/F and Varea/F) also differed slightly between the isomers. The data were interpreted as indicating a small difference in the absorption of the two isomers; it seemed unlikely, in terms of the identical elimination rates, that their metabolic profiles would differ greatly. The 5-phenyl-hydantoin was eliminated with a significantly longer half-life (18.69 ± 6.11 h) than that of ethotoin. Enantioselectivity in the pharmacokinetics of ethotoin is therefore a minor issue. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040303
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  • 93
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    Chiroptical detection during liquid chromatographyPart 4. For Part 3, see Ref. 1.: Applications to stereoanalysis and stereodynamics (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 163-169 
    Details
    ISSN: 0899-0042
    Keywords: polarimetry ; circular dichroism spectra ; optical purity ; thermal interconversion of enantiomers ; optically active sorbents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Qualitative and quantitative use of polarimetry at one wavelength for detection during liquid chromatography is briefly reviewed. Acquisition of circular dichroism spectra by stopped-flow and nonstop measurements has been further developed. Reasons are given why the angle of rotation, i.e., the polarimeter, is preferred for monochromatic use and differential absorbance, i.e., the dichrograph, for polychromatic requirements. Both methods are demonstrated by novel applications, mainly to enantiomers which interconvert thermally via intramolecular processes. © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040306
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  • 94
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    Enantio- and regioselectivity in the epoxide-hydrolase-catalyzed ring opening of simple aliphatic oxiranes: Part I: Monoalkylsubstituted oxiranes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 178-184 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; regioselective hydrolysis ; epoxide hydrolase ; substrate enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The in vitro conversion of chiral aliphatic monoalkylsubstituted oxiranes into 1,2-diols catalyzed by epoxide hydrolase of rat liver microsomes occurs with substrate enantioselectivity and regioselectivity. Substrate enantioselectivity is generally low, and has the same sense, for methyloxirane, vinyloxirane, epichloro-, and epibromohydrin. In the hydrolysis of t-butyloxirane inhibitory effects are involved leading to a complex pattern of enantioselectivity. All investigated monosubstituted aliphatic oxiranes are hydrolyzed with high regioselectivity by nucleophilic attack of water at the unsubstituted ring carbon atom. The enantiomeric excess of the unreacted oxirane substrates and the diol metabolites formed were determined by complexation and inclusion gas chromatography. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040309
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  • 95
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    Separation of enantiomeric amines and acids using chiral ion-pair chromatography on porous graphitic carbon (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 323-332 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; chiral counterion ; ion-pair chromatography ; N-benzyloxycarbonylglycyl-L-proline ; quinine ; indirect detection ; porous graphitic carbon ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of porous graphitic carbon as adsorbing phase for direct separation of enantiomeric acids and amines using chiral ion-pair chromatography is described. The enantiomeric amines were separated as diastereomeric ion pairs with N-benzyloxycarbonylglycyl-L-proline, N-benzyloxycarbonylglycylglycyl-L-proline, or captopril as the chiral counterion. High enantioselectivities were obtained for amines having a hydrogen bonding function in the vicinity of the asymmetrical carbon atom. Quinine was the chiral counterion used to separate the enantiomeric acids. The strongly UV-absorbing quinine improved detection of solutes having low UV-absorbing properties, e.g., (R,S)-2-chloropropionic acid, by “indirect detection.” Retention and stereoselectivity of enanticmeric acids were regulated by the quinine concentration and by the addition of carboxylic acids as well as polar modifiers, e.g., methanol and 2-propanol, to the mobile phase. © 1992 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040511
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  • 96
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    Editorial: Chirality receives award from the association of american publishers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 341-341 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040602
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  • 97
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    Chiral hplc-cd studies of the antituberculosis drug (+)-ethambutolPresented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 227-229 
    Details
    ISSN: 0899-0042
    Keywords: circular dichroism ; exciton coupling ; derivatisation ; tetrabenzoylethambutol ; dibenzoyl-2-aminobutan-1-ol ; absolute stereochemistry ; Pirkle column ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Long standing errors in major pharmacopoeiae (BP,USP, and Eu.Ph.) concerning the absolute stereochemistry of the widely used antituberculosis drug (+)-ethambutol have been clarified by unambiguous synthesis and chiral HPLC. on a Pirkle, covalent D-phenylglycine column of perbenzoyl derivatives of each stereomer; the enantiomeric (-)-(R,R) and (+)-(S,S)-ethambutols together with the optically inactive (meso)-(R,S)-ethambutol. This paper describes how circular dichroism (CD) alone and combined with HPLC is used to demonstrate this chiral separation and also to confirm the absolute stereochemistry of each stereomer of ethambutol and its synthetic precursor 2-aminobutan-1-ol from studies of „exciton coupling.“ The strengths and weaknesses of these chiral techniques are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040405
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  • 98
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    Chirality evaluation in flavour and essential oil analysis (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 50-55 
    Details
    ISSN: 0899-0042
    Keywords: simultaneous stereodifferentiation of γ(δ)-lactones ; chiral monoterpenes ; stereoselective analysis ; modified cyclodextrins ; genuineness of flavours and essential oils ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simultaneous stereodifferentiation of all aromarelevant 4(5) alkylsubstituted γ(δ)-lactones is described, using enantioselective multidimensional gas chromatography (MDG), and the column combination OV 1701/octakis(3-O-butyryl-2,6-di-O-pentyl)-γ-cyclodextrin. The method is applicated to the lactone flavour compounds of fruits, indicating the advance to the analytical differentiation between “natural” and “nature-identical” aromas. Modified cyclodextrins are also proved to be powerful tools in the chirospecific CGC analysis of monoterpenoid constituents of essential oils. Optical purity control is discussed as an indicator for their natural origin.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040111
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  • 99
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    Determination of the enantiomeric purity of (--) 2-(N-propyl-n-2-thienylethylamino)-5-hydroxytetralin (n-0923) by chiral stationary phase HPLC (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 62-64 
    Details
    ISSN: 0899-0042
    Keywords: dopamine agonist ; direct chiral separation ; cellulose carbamate stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of the enantiomeric impurity, i.e., the percentage of (+) N-0437 (= N-0924) in several batches of (--) N-0437 (= N-0923) by chiral HPLC is described. Enantiomeric impurities were calculated based on the peak areas of the two baseline separated enantiomers in the chromatogram. The enantiomeric impurities found in different batches ranged from 0.02% to 0.11%. Calibration curves of the two isomers of N-0437 (Fig. 1,) were made twice to study the reproducibility and linearity of the method. The absorbance ratio, N-0923/N-0924, was found to be 1.02 with a relative standard deviation (RSD) of 9% over the whole concentration range used for the calibration curves.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040113
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  • 100
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040201
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