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  • 1985-1989  (767)
  • 1965-1969  (645)
  • 1988  (767)
  • 1967  (645)
  • Organic Chemistry  (1,398)
  • Obesity
  • 1
    Electronic Resource
    Electronic Resource
    Die Beziehung zwischen Körperfettverteilung, Insulinspiegeln und Glukosetoleranz bei übergewichtigen Frauen (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 216-222 
    Details
    ISSN: 1432-1440
    Keywords: Fat distribution ; Hyperinsulinemia ; Obesity ; Glucose tolerance ; Non-insulin dependent diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Relationship between body fat distribution, serum insulin, and glucose tolerance in obese, non-diabetic women. Recent studies suggest that hyperinsulinemia and upper body obesity are predictive factors for the development of non-insulindependent diabetes mellitus. To further characterize the relationship between body fat distribution, serum insulin, and glucose tolerance an oral glucose tolerance test was performed in 48 obese, nondiabetic women. Fasting insulin levels were correlated to both total body fat calculated as body mass index (r=0.58,p〈0.001) and upper body fat distribution expressed as waist-to-hip ratio (WHR,r=0.47,p〈0.01). In the women with upper body fat localization (WHR〉0.90) significantly higher basal and glucose-stimulated insulin concentrations were established than in the women with a lower body type of obesity (WHR〈0.78) (basal insulin 27.4±11.5 vs. 15.4±8.8 mU/l,p〈0.05, insulin area 779±320 vs. 468±237 U,p〈0.05). They also had impaired glucose tolerance (glucose area 925±139 vs. 633±147 U,p〈0.01). Fasting triglyceride concentrations were correlated both with WHR (r=0.63,p〈0.001) and fasting insulin (r=0.33,p〈0.05) but not with BMI (r=−0.02, n.s.). A positive association was found between systolic and diastolic blood pressure and both WHR (r=0.43 andr=0.44 resp.,p〈0.01) and BMI (eachr=0.35,p〈0.05). Interestingly, basal insulin was also associated with blood pressure (r=0.30,p〈0.1, andr=0.40,p〈0.01 resp.). These results suggest a close relationship between upper body obesity, hyperinsulinemia, and impaired glucose tolerance. Women with an upper body tpye of obesity also show tendencies to hypertriglyceridemia and hypertension. Obese women with upper body obesity represent a subgroup of the obesity population with an increased risk to develop type-II diabetes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01728200
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  • 2
    Electronic Resource
    Electronic Resource
    Reduced insulin removal and erythrocyte insulin binding in obese children (1988)
    Springer
    European journal of pediatrics 148 (1988), S. 233-237 
    Details
    ISSN: 1432-1076
    Keywords: Insulin and C-peptide ; Metabolism ; Receptor ; Obesity ; Weight loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To study the relationship between childhood obesity, weight loss, hyperinsulinaemia and the erythrocyte insulin receptor, we measured the plasma concentrations of immunoreactive insulin (IRI) and C-peptide and the binding of 125I-insulin to erythrocytes in 12 obese children with a mean age ±SD of 11.4±2.5 years and a mean relative weight score ±SD of 4.8±1.4 and 12 age-matched normal-weight children. Eight obese children were re-evaluated after 1 year's participation in a weight reduction programme. The obese children had higher fasting plasma concentrations of IRI (P〈0.01) and C-peptide (P〈0.05) and a lower C-peptide to IRI molar ratio (P〈0.01) than the normal-weight children. The obese children had in addition a reduced erythrocyte insulin binding (P〈0.05 or less) over the physiological range of circulating insulin concentration. There was a negative correlation (r=−0.60; P〈0.01) between the insulin tracer binding and the relative weight. The weight reduction programme resulted in a decrease of 1.0SD (P〈0.05) in the mean relative weight score. At the end of the therapy the obese children had lower fasting blood glucose levels (P〈0.05) and lower plasma IRI concentrations at 90 min (P〈0.05) after an oral glucose load than at the onset of therapy. There were no significant differences between the insulin binding characteristics at the commencement and at the end of the treatment. The low C-peptide to IRI molar ratio in obese children provides evidence of a decreased insulin clearance likely to contribute to their hyperinsulinaemia. The inverse relationship between insulin tracer binding and relative weight suggests a mechanism by which weight changes may be directly reflected in the peripheral insulin sensitivity. A moderate weight loss reduces hyperinsulinaemia in childhood obesity but does not normalize the impaired binding of insulin to its receptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00441410
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  • 3
    Electronic Resource
    Electronic Resource
    Die stereoisomeren Sinensiaxanthine und Sinensiachrome: Trennung und Bestimmung ihrer absoluten Konfiguration. 7. Mitteilung über Rosenfarbstoffe6. Mitteilung, s. [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 24-30 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoisomeric Sinensiaxanthins and Sinensiachromes: Separation and Absolute ConfigurationThe so-called sinensiaxanthins and sinensiachromes, important apocarotenols from various fruits, have been separated into 2 and 4 stereoisomers, respectively, and their absolute configurations have been determined: (3S,5R,6S)-5,6-epoxy-5,6-dihydro-10′-apo-β-carotene-3,10′-diol (2), its (9Z)-stereoisomer 7, the (8R)- and (8S)-epimers of (3S, 5R)-5,8-epoxy-5,8-dihydro- 10′ -apo-β-carotene-3, 10′-diol (4 and 5), and their (9Z)-stereoisomers 3 and probably 6. Thus, sinensiaxanthins are cleavage products from (Z/E)-isomeric antheraxanthins or violaxanthins (scission at C(9′)-C(10′)) and sinensiachromes analogously from mutatoxanthins or auroxanthins.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710103
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  • 4
    Electronic Resource
    Electronic Resource
    Enantioselektive Verseifung der Diacetate von 2-Nitro-1,3-diolen mit Schweineleber-Esterase und Herstellung enantiomerenreiner Derivate von 2-Nitro-allylalkoholen (chirale Verknüpfungsreagenzien)Kurzmitteilung mit ausführlicher Beschreibung der Isolierung und Anwendung von Schweineleber-Esterase Rohpräparaten, s. [1].Teilweise erwähnt in einem Übersichtsartikel über EPC-Synthesen unter C,C-Verknüpfung mit Hilfe von Enamine, s. [2]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1-23 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective Saponification of Diacetates of 2-Nitro-1,3-propanediols by Pig-Liver Esterase and Preparation of Enantiomerically Pure Derivatives of 2-Nitro-allylic Alcohols (Chiral Multiple-Coupling Reagents)The reproducible enantioselective saponification of open-chain and cyclic diacetates of meso-2-nitro-1,3-propanediols (see 4b-13b) with pig-liver esterase (PLE) gives monoacetates (see 4c-l3c) of 〉 95% enantiomeric excess. The Re enantiotopic acetate group appears to be saponified preferentially, as proved by the X-ray crystal structure analysis of three camphanoates 4d, 6d, and 7d. Elimination of H2O or AcOH from the hydroxy acetates thus available gives derivatives of nitro-allylic alcohols (see 20-24, 27, and 29) which are subjected to diastereoselective Michael additions or SN2′ substitutions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710102
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  • 5
    Electronic Resource
    Electronic Resource
    New Pterocarpinoids from Dolichos marginata ssp. erecta (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 72-76 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four new pterocarpinoids, sphenostylin A, B, C, and D (1-4), have been isolated from the CHCl3 extract of the root bark of Dolichos marginata ssp. erecta (Leguminosae) by preparative liquid chromatography. The structures have been established by spectroscopic methods (UV, 1H-NMR, 13C-NMR, EI-MS, DCI-MS, CD) and chemical transformations. The isolated compounds showed weak antifungal activity against Cladosporium cucumerinum.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710109
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  • 6
    Electronic Resource
    Electronic Resource
    Condensed Heterotricycles. Synthesis and Reactions of b-Fused 1(2H)-Isoquinolinones with unusual enaminic propertiesContribution No. 822 from Hindustan Ciba-Geigy Ltd., Research Centre. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 77-92 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homophthalic acid (1) undergoes reaction with 1,2-, 1,3-, and 1,4-diamines to give condensed 1(2H)-isoquinolinones like 2, 4, 13, and 25, which exhibit marked enamine character. These are attacked by electrophiles at the N or C terminus. Some notable reactions of imidazoisoquinolone 2 are those with maleic and acrylic acids to form the tetracycles 48 and 51, respectively. With propiolic acid, 5 underwent an interesting reaction to form the benzimidazonaphthyridine 53. An equally interesting behaviour was elicited from 2 in its reaction with formaldehyde, when in addition to the expected methylene-bridged molecule 59, the novel spiro derivative 60 was formed by the dimerisation of a presumed azadiene intermediate 63.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710110
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  • 7
    Electronic Resource
    Electronic Resource
    The dimeric and polymeric anhydride of 2,3-O-isopropylidene-β-D-ribofuranose. An NMR study (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 120-123 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H- and 13C-NMR data of the dimeric anhydride 1 of 2,3-O-isopropylidene-β-D-ribofuranose are reported together with the 1H-NOE values. The data show that the products of the polymerization of 1,5-anhydro-2,3-O-isopropylidene-β-D-ribofuranose are α- and β-D-ribofuranans and not an α-D-ribofuranan and a β-D-ribofuranan and a β D ribo-pyranan as claimed before [2] [3].
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710114
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  • 8
    Electronic Resource
    Electronic Resource
    Complexes with a Pincers. 2,6-Diphenylpyridine as Twofold-Deprotonated (C ∧ N ∧ C) terdentate ligand in C,C-trans-, and as mono-deprotonated (C ∧ N) chelate ligand in chiral C,C-cis-complexes of platinum(II) and palladium(II). Preliminary communication (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 130-133 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,6-Diphenylpyridine forms, as twofold-deprotonated, terdentate ligand, complexes with Pt(II) and Pd(II), having two adjacent five-membered metallocycles. As mono-deprotonated, bidentate ligand, it forms cis-bis-complexes having a chirality axis. Pt(II) complexes undergo thermal and photochemical oxidative addition reactions, yielding stable Pt(IV) compounds. Pd(II) complexes yield substitued 2,6-diphenylpyridine in photochemical reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710116
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  • 9
    Electronic Resource
    Electronic Resource
    Silicon-Directed Nazarov Cyclizations. Part V. Substituent and heteroatom effects on the reaction (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 168-194 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability to incorporate alkyl, alkenyl, aryl, and heteroatomic groups into substrates for the silicon-directed Nazarov cyclization and their subsequent reactions has been investigated. In general, most of the groups are compatible with the conditions for the cyclization and do not interfere even when directly attached to the divinyl ketone. The influence of substituents on the rate of the cyclization has been addressed and is consistent with a simple mechanistic picture. O- and N-Containing functions are tolerated except when attached to the α-vinyl C-atom of the divinyl ketone. The diastereoface-directing effect of a fused cyclobutane is discussed.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710120
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of Aristotelia-Type Alkaloids. Part III.Part II: [1]. (3R,4R)- and (3R,4S)-1-p-menthene-3,8-diol and the corresponding racemates: Preparation and assignment of configuration (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 209-217 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 1:1 mixture of the racemic trans- and cis-1-p-menthene-3,8-diols ((±)-3 and (±)-4, resp.) was readily prepared in 3 steps starting from 3-methyl-2-cyclohexen-1-one. The relative configuration of the diols, purified via the corresponding cyclocarbonates, was assigned by 1H-NMR spectroscopy and found to be at variance with tentative claims in the literature. Optically active samples of 3 and 4 were prepared by resolution of the racemates with (R)-1-phenylethylamine. The absolute configuration of the resulting diols was determined by chemical correlation with standards of known absolute configuration.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710122
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  • 11
    Electronic Resource
    Electronic Resource
    Herstellung enantiomerenreiner, α-alkylierter Lysin-, Ornithin- und Tryptophan-Derivate (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 224-236 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Enantiomerically Pure, α-Alkylated Lysine, Ornithine, and Tryptophan DerivativesThe imidazolidinones 9 and 10 as well as the oxazolidinone 18a were prepared in several steps by known methods from lysine and ornithine with an overall yield of ca. 20%. After double deprotonation with LDA, the corresponding dianionic derivatives could be diastereoselectively alkylated with electrophiles (MeI, C6H5CH2Br, C6H5CHO, CH3CHO). Acid hydrolysis led to the two enantiomeric 2-methyl- and 2-benzyllysines and to the enzyme inhibitor (S)-2-methylornithine. Several α-alkylated tryptophan derivatives were obtained through alkylation of the heterocycles derived from various amino acids with 1-(tert-butyloxycarbonyl)-3-(bromomethyl)indole (26). Alkaline hydrolysis of the five-membered auxiliary ring of 30b followed by treatment with HCl afforded (S)-2-methyltryptophan (31).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710124
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  • 12
    Electronic Resource
    Electronic Resource
    Hydrogénation de sels de flavylium: formation de composés heptacycliques; structure radiocristallographique du [tétrahydro-10b,10c,16,16a-diméthyl-16,16a-méthylène-10b,16-5aH-di(benzo[1]pyranno)[4,3-b:3′,4′,-c;2,3:2′,3′]-benz[1]oxépinyl-5a]-2-phénol (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 254-257 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenation of Flavylium Salts: Formation of Heptacyclic compounds; X-Ray Crystal Structure of 2-[10b,10c,16,16a-Tetrahydro-16,16a-dimethyl-10b,16-methylene-5aH-di[1]benzopyrano[4,3-b:3′,4′ -c; 2,3:2′,3′][1]benzoxepin-5a-yl]phenolThe hydrogenation of flavylium salts 1 either by catalytic reduction or by chemical reduction afforded the unexpected heptacyclic compound 2, the structure of which was determined by X-ray analysis. The latter was confirmed by 1H-NMR and mass spectra.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710128
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  • 13
    Electronic Resource
    Electronic Resource
    Konformationsanalysen von Modell-Tripeptiden: Der Einfluss von α,α-disubstituierten α-Aminosäuren auf die Sekundärstruktur. Teil II. Röntgenstrukturanalyse und Konformationsenergie-Berechnungen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 268-273 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational Analysis of Tripeptide Models: The Influence of α,α-disubstituted α-Amino Acids on the Secondary Structure. X-Ray Analysis and Conformational Energy CalculationsThe X-ray analysis of tripeptide Z-Ile-Val(2-Me)-benzocaine (1f) reveals the presence of a type-III β-turn. Moreover, MMP2 calculations on tripeptides, e.g. Z-Ile-Aib-benzocaine (1c), Z-Ile-D-Val(2-Me)-benzocaine (1g), Z-Ile-Gly(2,2-Pr2)-benzocaine (1h), Z-Ile-Gly-benzocaine (1a), and 1f, fit well into the frame of NMR and CD investigations. They allow considerations on the relative stability of different types of β-turns depending on the peptide sequence, e.g. the kind of α,α-disubstituted amino-acid moieties.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710130
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  • 14
    Electronic Resource
    Electronic Resource
    Synthese von (-)-(R)-Nephthenol und (-)-(R)-Cembren A (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 292-297 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of (-)-(R)-Nephthenol and (-)-(R)-Cembren AStarting for L-serine,(-)-(R)-nephthenol((-)-2) and (-)-(R)-cembren A((-)-3) were synthesized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710133
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  • 15
    Electronic Resource
    Electronic Resource
    Low-Temperature X-ray Crystal-Structure Analysis of the Thermally Unstable Lithiated 2-Butenyl tert-Butyl Sulfide: A comparison with model ab initio MO calculationsPart of the projected Dissertation of Th. M., ETH Zürich. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 299-311 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single crystals of the N,N,N′,N′-tetramethylethylenediamine (TMEDA) complex 6 of the title compound have been isolated. Compound 6 decomposes in the crystalline state above -20°. From the bond lengths and angles obtained by X-ray crystal-structure analysis (data collected at -70°), compound 6 is best described as a (E)-1-(tert-butylthio)-1-lithio-2-butene with the double bond acting as an additional ligand on lithium (unsymmetrical allylic group). The S-atom is in a cisoid arrangement in a common plane with the four C-atoms of the butenyl system. The t-Bu group and the Li-atom are located above and below this plane. The structure is discussed with respect to the reactivity of 6 (α/γ reactivity). The gross structure is reproduced surprisingly well by an ab initio SCF MO calculation of the model lithiopropene-1-thiol 7(HS instead of t-BuS, CH2 instead of CHCH3, no solvation of Li). The prominent difference is the symmetry of the allyllic moiety in the calculated structure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710202
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  • 16
    Electronic Resource
    Electronic Resource
    Notiz zur Synthese Eines Optisch Aktiven Ace-Hemmers mit Amino-oxo-benzazepin-1-alkansäure-Struktur mittels enantiokonvergierender kristallisationsinduzierter Racemat-Trennung (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 337-343 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Note on the Synthesis of an Optically Active ACE Inhibitor with Amino-oxo-benzazepine-1-alkanoic-Acid Structure by Means of an Enantioconvergent Crystallization-Based ResolutionAn enantioselective synthesis of the potent angiotensin-converting enzyme inhibitor (1′S,3S)-3-[(1′-(ethoxy-carbonyl)-3′-phenylpropyl)amino]-2,3,4,5-tetrahydro-2-oxo-1H-1-benzazepine-1-acetic acid hydrochloride (3) is described which user a crystallization-based resolution of a racemic amino intermediate with concomitant racemization of the unwanted enantiomer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710205
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  • 17
    Electronic Resource
    Electronic Resource
    Polycyclopentane Als Steroid-Analoga (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 363-368 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polycyclopentanes as Steroid AnalogaThe synthesis of linearly annellated pentaquinanes from a readily available triquinane is reported.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710209
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  • 18
    Electronic Resource
    Electronic Resource
    Synthese Eines Optisch Aktiven Penem-Zwischenprodukts Mittels Asymmetrischer Amidoalkylierung (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 395-403 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of an Optically Active Penem Intermediate by Asymmetric AmidoalkylationThe amidoalkylation of an optically active, cationic glycine derivative with methyl acetoacetate furnishes an intermediate 10a (Scheme 2) that is transformed in six steps to the optically active, silyl-protected 4-acetoxy-3-(1-hydroxyenthyl)-2-azetidinon 18a, a well known intermediate in penem synthesis.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710213
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  • 19
    Electronic Resource
    Electronic Resource
    Circular Dichroism of Planar, Exocyclic S-cis-Butadienes Remotely PerturbedInteraction between non-conjugated chromophores, Part 29. Part 28, see [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 419-428 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically pure 5,6-dimethylidenebicyclo[2.2.1]hept-2-yl derivatives have been prepared. The sign of the Cotton effects associated with lowest-energy transition of 2-(dicyanomethylidene)-((-)-(1S,4S)-15), (E)-2-(methoxyimino)-((+)-(1S,4S)-16), (Z)-2-(methoxyimino)-5,6-dimethylidenebicyclo[2.2.1]heptane ((-)(1S,4S)-17), and 2,3,5-trimethylidenebicyclo[2.2.1]heptane ((-)-(1R,4S)-18) is opposite to the chirality constituted by the coupling of the electric transition moments of the two homoconjugated π-chromophores (Kuhn-Kirkwood dipole-coupling mechanism). When the substituents at C(2) are not π-functions, no general rule can be retained for the chiroptical properties of the 5,6-dimethylidenebicyclo[2.2.1]hept-2-yl systems as shown for dimethyl acetal (-)-(1S,4S)-19, ethylene acetal (+)-(1R,4R)-20, exo and endo methyl ethers (+)-(1R,2S,4R)-21 and (+)-(1R,2R,4R)-22, and for spirol[5,6-dimethylidenebicyclo[2.2.1]heptane-2.2'-oxiranes](-)-(1S,2S,4S)-23 and (-)-(1S,2S,4S)-24.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710215
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    Ferroelectric Liquid Crystals. Part 2.‘Ferroelectric Liquid Crystals’, Part 1: [1]. Chiral phenyl benzoates incorporating a trans-1,4-disubstituted cyclohexane ring (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 451-460 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: About forty novel phenyl benzoates also incorporating a trans-1,4-disubstituted cyclohexane ring and a chiral centre have been prepared. The dependence of the liquid-crystal transition temperatures of this new class of compounds on lateral substituents, diverse central linkages, chain lengths, and position of the chiral centre has been studied systematically. The synthesis and liquid-crystal transition temperatures of these new compounds are described in detail.
    Additional Material: 7 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710218
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  • 21
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    [4 + 2]-Cycloadditionen von α,β-ungesättigten Hydrazonen. Teil 1. Pyridin-2,3-dicarboximide aus 1-(Dimethylamino)-1,4-dihydropyridin-Derivaten (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 486-492 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [4 + 2] Cycloadditions of α,β-Unsaturated Hydrazones to Pyridine-2,3-dicarboximides via 1-(Dimethylamino)-1,4-dihydropyridine DerivativesThe [4 + 2] Cycloaddition of α,β-unsaturated hydrazones of type 1 (1-aza-1,3-butadienes) with 2-halogenomaleimides 4 affords 1,4-dihydropyridines 6 which, after treatment with an acid, yield highly substituted pyridine-2,3-dicarboximide derivatives 7 (Scheme 1).
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710222
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  • 22
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    Photochemistry of 2,2-Dimethyl-2H-Furo[3,4-b]Pyran-4,7(3H, 5H)-Dione (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 498-501 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation (λ 〉 340 nm) of the title compound 2a in t-BuOH affords 3,3,10,10-tetramethyl-2,8-dioxatricyclo-[4.3.2.01,6]undecane-5,9-dione (3) via photoextrusion of 2-methylpropene and subsequent photocycloaddition of 2a to the alkene. The same regioisomer 3 is formed selectively and in much higher yields on irradiating 2a in the presence of excess 2-methylpropene. Irradiation of 3 (λ = 300 nm) in t-BuOH in the presence of the same alkene gives a 6:1 mixture of spirooxetanes 7a and 7b but not α-cleavage products. In 2-propanol, 2a is photoreduced to a 2:1 mixture of diastereoisomeric hydrodimers 9.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710224
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    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/hlca.19880710301
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  • 24
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    Une synthèse générale des tétraazamacrocycles mono-C-fonctionnalisés (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 602-608 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A General Synthesis for Mono-C-Functionalized TetrazamacrocyclesA new synthesis, under usual conditions of concentration, medium, and temperature, of a series of mono-C-functionalized tetraazamacrocycles is given. The method may easily be generalized. The new procedure allows the modification of the length of the side-chain or the size of the cavity by choosing fitted staring materials. The key intermediate has a tosylated linear side-chain susceptible to be transformed into a large variety of functional groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710313
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  • 25
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    Enantiomerically pure 7-oxabicylo[2.2.1]hept-5-en-zyl derivatives as synthetic intermediates. Part IIIPart I, see [1]; Part II, see [2].. Total synthesis of D- and L-ribose derivativesFor a preliminary communication, see Y. Auberson, R. Bimwala, J. Wagner, P. Vogel, Société Suisse de Chimie, Berne, 16 Oct. 1987, Abstract p. 29. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 624-630 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure methyl 5-bromo-5-deoxy-2,3-O- isopropylidene-β-D- (D-5b) and -β-l-ribofuranoside (l-5b) have been derived from (-)-(1R,2S,4R)-2-exo-cyano-7-oxabicylo[2.2.1]hept-5-en-endo,-yl (1′S)-camphanate (1) and (+)-(1S,2R,4S)-2-exo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl(1′R)-camphanate (2), respectively, in 5 synthetic steps and 28% overall yield. Hydrolysis of D-5b and L-5b afforded methyl 2,3-O isopropylidene-β-D-ribofuranoside (D-5a) and methyl 2,3-O-isopropylidene β-L-ribofuranoside (L-5a), respectively. The intermediate (+)-(1R,4R,5R,6R) 5-exo,6-exo-(isopropylidenedioxy)-7-oxabicyclo[2.2.1]heptan-2-one ((+)-7) and its enantiomer(-)-7 were also obtained enantiomerically pure by resolution of (=)-7 by the Johnson-Zeller method. In bothe approaches, the chiral auxiliaries ((-)- and (+)-camphanic acids, or (+)-(S)-N,S-dimethyl-S-phenylsulfoximide) were recovered at an early stage of the synthesis.
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    URL: http://dx.doi.org/10.1002/hlca.19880710316
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    Mécanisme de solvolyse des cis- et trans-(p-toluènesulfonates) d'aryl-2-cyclopentyle I. Etude de la première étape de la solvolyse: effets isotopiques de l' atone de deutérium en position 2, effets de sel basique et effet spécial de sel (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 648-657 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Solvolysis Mechanism of cis - and trans-2-Arylcylopentyl p-Toluenesulfonates. The Step: 1-Deuterium Isotope Effects, Basic Salt Effects, and Special Salt EffectWe have studied the first step of the solvolysis of cis and trans-2-arylcyclopentyl p-toluenesulfonates in HCOOH, AcOH, and EtOh. All substrates show a high kinetic 1-deuterium isotope effect (kH/kD(1) 〉1.15). This fact indicates that first step leads to classical intimate ion-pair Which dissociates to a solvet-separated ion-pair, without participation either of solvent, the 2-aryl group, or a H-atom at C(2). The slight influence of added basic ions on reaction rate allows us to exclude any direct solvent attack on the covalent substrate even in the most favorable case, i.e. ethanolysis of 2-(p-nitrophenyl)cylopentyl-p-toluenesulfonates. Furthermore, solvent-separated ion pair formation is indicated by the special salt effect induced by LiClO4.
    Notes: No abstract.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710319
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    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/hlca.19880710401
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    Anion-receptor molecules: Synthesis of a chiral and functionalized binding subunit, a bicyclic guanidinium group derived from L- or D- asparaginePresented in part at the 11th International Congress of Heterocyclic Chemistry, Heidelberg, Federal Republic of Germany, August, 1987. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 685-693 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optically active (4S,8S)-4, 8-bis(hydroxymethyl)-1,5,7-triazabicyclo[4.4.0]dec-5-ene ((S,S)-1) has been synthesized in nine steps from L-asparagine with a total yield of 5.1%. Similarly, the enantiomer (R,R)-1 has been prepared from D-asparagine. (S,S)- and (S,S)-1 are representative examples of rigid and functionalized bicyclic guanidine systems and constitute useful intermediates in the construction of chiral selective anion-receptor molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710402
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    Studies on Antifungal Agents. Part 22. 3-aryl-5-[(aryloxy)alkyl]-3-[(1H-imidazol-1-yl)methyl]-2-methylisoxazolidines and related derivatives (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 718-732 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and antifungal activity of a novel series of 3-aryl-5-[(aryloxy)alkyl]-3-[(1H-imidazol-1-yl)-methyl]-2-methylisoxazolidines and related compounds, are discussed. The synthesis of the title compounds was accomplished via a 1,3-dipolar cycloaddition of α-substituted ketonitrones with l-alkenyl phenyl ethers (Scheme 2 and 3). The compounds were evaluated for in vitro antifungal activity in solid agar cultures against a broad variety of yeast and systemic mycoses and dermatophytes. While antifungal activity was evident throughout the series, in general, derivatives having halogen atom(s) in either or both aryl rings demonstrated the highest potency, especially against Trichophyton rubrum and Candida albicans. The dichloro analog 20 (PR 967-248) was found to possess the most useful activity. Its minimum inhibitory concentration (MIC) values ranged between 0.2 and 2.0 μg/ml, as compared to 0.2-20.0 μg/ml for the standard drug ketoconazole (4).
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710406
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    Captodative olefins in normal and inverse Diels-Alder ReactionsPart 3 of Thermal Reactions of Donor-Acceptor Systems. Part 2: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 742-748 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Olefins with captodative substitution are reactive dienophiles in Diels-Alder reactions with normal and inverse electron demand. This is shown for reactions of 2-(tert-butylthio)acrylonitrile (1) with various dienes and heterodienes, e.g. 1,3-cyclohexadiene, hexachloro-1, 3-cyclopentadiene, acrolein, methacrolein, and methyl vinyl ketone (Schemes 2 and 3). In case of the hetrodienes, 3,4-dihydro-2H-pyrans are formed beside small amounts of tetrahydrothiophenes; however, with methyl vinyl ketone, both reaction pathways are equally followed. The high reactivity of captodative olefins in Diels-Alder reactions are rationalized on the basis of Sustmann's FMO model under consideration of Viehe's concept of captodative substitution of alkenes.
    Additional Material: 1 Tab.
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    A novel rearrangement of 2(5H)-furanones (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 783-787 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel rearrangement of 2(5H)-furanones is described. When refluxed in aq. Ethanolic solution in the presence of excess KOH, the 2,5-dihydro-2-oxofuran-3-carboxamides 6 underwent a novel rearrangement to the corresponding 4,5-dihydro-4-oxo-2-(phenylamino)-3-furancarboxylic acids 1 in moderate-to-excellent yields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710413
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    Kurze Totalsynthesen von (±)-Sativen und (±)-cis-Sativendiol (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 788-807 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Short Total Syntheses of (±)-Sativene and (±)-cis-SativenediolOur approach to (±)-sativene (7) and (±)-cis-sdtivenediol (9) involves: (a) reaction of 3-methylbutanoyl chloride with Et3N/cyclopentadiene to give the endo-isopropyl-ketone 1 (here improved to 71%), (b) NBS bromination of 1 to a 5:1 mixture (87%) of the bromo-ketones 2 and 3, (c) NFD-reaction sequence initiated by the attack of 1,2-butadienyl titanate (complex of 15, obtained from 2-butine) on 2/3 to afford 52% of the brexenone derivative 4 (along with 8% of its epimer 16), (d) addition of dibromomethane to 4 forming 63% of the diene-alcohol 5 (along with 13% of the diene-carbaldehyde 38), and (e) carbenoid ring-expansion with MeLi applied to 5 resulting in 41% the diene-ketone 6 (along with 15% of a 1:3 mixture of the diene-ketones 32 and 33). Wolff-Kishner reduction of 6 led to 81% of (±)-sativene (7), when enough O2 was present, but to 97% of the diene 8 in the strict absence of O2. (±)-cis-Sativenediol (9) was obrained (86%) by OsO4 hydroxylation of 8. The brexenone derivatives 4 and 16 (6:1, 50%) were also produced when the NFD-reaction sequence was applied to the isomeric bromo-ketone mixture 13/13 (1:3). The latter was obtained by NBS bromination of 10, which in turn was available by base epimerization of 1, followed by destructive removal of unreacted 1 by repeated gas-flow thermolysis. An analogous (less convenient) route to (±)-sativene (7) passed through a series of dihydro compounds (the ene series) it started with the methylidene-ketone 36, which was the product (97%) of a partial hydrogenation of 4. Addition of dibromomethane to 36 led t 62% of the methylidene-alcohol 39 (along with a little tetracyclic ether 40). Carbenoid ring expansion of 39 with MeLi afforded ca. 42% of the methylidene-ketone 41 (along with 7% of the methylidene-ketone 43 or, under slightly different condition, along with 9% of the methylidene-ketone 42 and 10% of the methylidene-carabaldehyde 44). The methylidene-alcohol 39 and the methylidene-ketone 43 were also obtained by partial hydrogenation of 5 and 33, respectively. Wolff-Kisher reduction converted 41 into (±)-sativene (7 99%); the same conditons applied to 42 afforded only ca. 8% 7 (along with three other hydrocarbons, one of them (ca. 21%) probably being (±)-copacamphene (45)). In the diene series, the two succeeding reactions (4→5 and 5→6) competed with the same side reaction, a rearrangement leading to the brendene-aldehyde 38. In the ene series, the corresponding dihydro-by-product 44 was found in the reacton 39→41, but not during 36→39. These side reactons could largely be suppressed by keeping the reaction temperature low. An explanation is proposed.
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    Reactions of Haloarenes with Thiolate Anions in Tetraglyme: Competition between electron transfer and SNAr mechanisms (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 859-866 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the bromo-substituted naphthalene 1 with the alkanethiolate anions 2a-b and arenethiolate 2c in tetraglyme gave the corresponding 1-naphythyl thio-ethers 3a-c. Thio-ethers 3a-c were oxidized to the corresponding sulfones 4a-c with m- chloroperoxybenzoic acid. The reaction of the dichloro-substituted anthracene 5a with 2b gave the disubstutution product 6a. The reaction of 9-bromoanthracene 5c with the alkanethiolate 2b gave 6b, whereas the reaction of 5c with the arenethiolate 2c gave a mixture of substitution product 6c and anthracene 7. The observation of the formation of both 6c and 7 is explained by the competition between substitution (SnAr) and electron-transfer (ET) mechanisms. Consistent with this interpretation, the reaction of the monochloro-substituted 5b, which has a higher-energy σ* orbital, with 2c gave 6c without the formation of 7. Zn/KOH in tetraglyme was shown to reduce the aryl halides 5b-c and thio-ether 6c to 7.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710421
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    Synthèse de l'acide décarboxythamnolique (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 876-880 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Decarboxythamnolic AcidThe total synthesis of the meta-depside decarboxythamnolic ( = 3-[(3-formyl-2-4-dihydroxy-6-methyl-phenyl)oxy]-2-hydroxy-6-methoxy-4-methylbenzoic acid; 25) by the biomimetic condensation of the substituted β-orcinol units 9 and 22 is described.
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    URL: http://dx.doi.org/10.1002/hlca.19880710424
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    Metabolism of Carotenoids in Salmonids. Part 3Part 1: [4]; Part 2:[1].. Metabolites of astaxanthin and canthaxanthin in the skin of atlantic salmon (salmo salar, L.) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 887-896 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diets supplemented with astaxanthin and canthaxanthin, respectively, and a control diet without carotenoid additions, were fed to 1½-year-old Atlantic salmon (Salmo salar, L.) for one year. The integuments were investigated as to their quantitative and qualitative carotenoid composition. Astaxanthin and canthaxanthin deposited in the skin amounted to 20 and 14% of the total carotenoids only. Seventy % must be considered as metabolites of astaxanthin and canthaxanthin and 10% as basic xanthophylls also present in the control groups. Astaxanthin apparently underwent the following metabolic pathway: astaxanthin→idoxanthin→adonixanthin→zeaxanthin→zeaxanthin 5,6-epoxides. Reduction of the 4′-carbonyl group was stereospecific leading to the (4′R)-idoxanthin. Canthaxanthin was obviously converted to β,β-carotene via 4′-hydroxyechinenone, echinenone, and 4-hydroxy-β,β-carotene.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710426
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    Antifungal Polyphenols from Cordia goetzeiGürke (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1210-1219 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four highly oxygenated polyphenols 1-4, have been isolated from the stem bark of Cordia goetzei Gürke (Boraginaceae) and their structures elucidated by a combination of one- and two-dimensional (including COLOC) NMR spectroscopic techniques, mass spectroscopy, and chemical methods. The first new compound, cordigone (1), is a tetrahydrofuran derivative and the second one, cordigol (2), a furobenzopyran derivative. The benzofurans 3 and 4 are orange pigments, responsible for the coloration of the stem bark of the tree. All four polyphenols are fungicidal against cladosporium cucumerinum.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710532
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    8-Aza-7-deaza-2′-deoxyguanosine: Phosphoramidite synthesis and properties of octanucleotides (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1191-1198 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Base-modified octanucleotides derived from d(G1-G2-A-A-T-T-C-C-) (11) but containing 8-aza-7-deaza-2′-deoxyguanosine (2) instead of 2′-deoxyguanosine (1) have been prepared by solid-phase synthesis employing P(III) chemistry. Isobutyrylation of 2, followed by 4, 4′-dimethoxytritylation and subsequent phosphitylation yielded the methyl or the cyanoethyl phosphoramidites 6a or 6b, respectively. They were used as building blocks in automated DNA synthesis. The resulting octanucleotides 12-14 containing 2 showed increased Tm values compared to the parent oligomer 11. The oligomers 11-14 were employed as sequence-specific probes in endo-deoxyribonuclease Eco RI oligonucleotide recognition. Whereas displacement of dG-2 (enzymic cleavage site of 11) abolished phosphodiester hydrolysis, replacement of dG-1 enhanced the cleavage rate compared to 11.
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    URL: http://dx.doi.org/10.1002/hlca.19880710530
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    Synthesis of Optically Pure Tricarbonyliron Complexes of 5,6-Dimethylidenebicyclo[2.2.2.]oct-2-yl derivatives. Crystal structure and absolute configuration of (+)-tricarbonyl(1S,2S,4R,5R,6S)-C,5,6,C,-η-(5,6-dimethylidenebicyclo[2.2.2]oct-2-yl p-bromobenzoate)iron (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1349-1353 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title complexes have been derived from tricarbonyl [(1R,4S,5S,6R,)-C,5,6,C-η-(5,6-dimethylidenebicyclo[2.2.2]oct-2-ene)]iron (1.). The crystal structure and absoulte configuration of (+)-tricarbonyl (1S,2S,4R,5R,6S)-C,5,6,C,-η-(5,6-dimethylidenebicyclo[2.2.2]oct-2-yl p,-bromobenzoate)]iron ((+)-6) determined by X-ray diffrac-tion studies proved earlier attribution of the relative configuration (endo us. exo,) of the tricarbonyliron moieties in complexes 1 and 2 of 5,6-dimethylidenebicyclo[oct-2-ene. The structure of (+)-6 confirms the absolute configuration derived earlier from circular-dichroism spectra of 5,6-dimethylidenebicyclo[2.2.2]oct-2-yl esters and 5,6-dimethylidenebicyclo[2.2.2]octan-2-one.
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  • 39
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    Photocycloadditions of 2-(trimethylsilyloxy)-1,3-butadiene to 2-cycloalkenones. Access to the basic pentalenolactone skeletonPreliminary communication: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1392-1398 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2 + 2] Photocycloaddition of 2-(trimethylsilyloxy)-1,3-butadiene to a number of 2-cycloalkenones proved to be quite a general reaction leading to good yields of the cycloadducts (Table). This finding is surprising since dienes, in general, are better known as quenchers of enone triplets rather than as photochemical reactants. Both the high substrate concentrations, which can be employed in these cycloadditions, and the remarkable regio and stereoselectivity of the processes qualify them as valuable for syntheses. In a first application, the photoproducts 1a, b were transformed in three steps into a viable precursor 4 of the pentalenolactone-G and -H antibiotics.
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  • 40
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    Transition-Metal Complexes with Bidentate Ligands Spanning trans-Positions. Part XVIIPart XVI: see [1].. Some platinum(II) complexes with anionic ligands such as methoxide, formate, carboxylate, hydride, and borohydride, and the X-ray crystal structure of [PtHCl()] (PP = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1442-1457 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexes trans-[PtXY(2] (X = H or Me; Y = OMe, OCHO, CO2H, and BH4; 2 = 2,11-bis{bis[3-(trifluoromethyl)phenyl]phosphinomethyl}benzo[c]phenanthrene) were prepared, and their decompositions to trans[PtHX(2)] were studied. Some binuclear hydrido-bridged complexes, e.g.[(2)HPt(μ-H)PtH(2)]+, were also obtained. The preparation of complexes trans-[PtHX(28)2] (X = H or Me, 28 = bis[3-(trifluoromethyl)phenyl]benzylphosphine) is also reported. The X-ray crystal structure of trans-[PtHCl1)] (1 = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene) was carried out.
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  • 41
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    Singlet-Oxygen Quenching by Carotenoids: Steady-state luminescence experiments (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1005-1010 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The near-infrared luminescence of singlet oxygen (1O2) has been measured in order to determine the efficiency of 1O2 quenching by two carotenoid compounds, β-carotene and canthaxanthin. 1H-Phenalen-1-one and rose bengal have been used as photosensitizers in those steady-state luminescence experiments. Stern-Volmer analysis of the 1O2 luminescence in solutions of CCl4 and CD3OD, containing different concentrations of the carotenoids, has shown a very efficient quenching by canthaxanthin. The rate constants are about a factor of 2 below the diffusion limited values for the given solvents, confirming earlier results in benzene. In comparison, the efficiency of 1O2 quenching by β-carotene is slightly lower than that by canthaxanthin in non-polar solvents and is reduced by an order of magnitude in CD3OD, due to the aggregation of this quencher.
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  • 42
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    Preparation of 3-Oxo- and 3-Ethylideneazetidine DerivativesThis work is part of the Ph. D. thesis of H. B. [1] (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1035-1041 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of 3-azetidinones with different N-substituents and their transformation to 3-ethylideneazetidines has been studied in relation with a projected synthesis of 3-ethylideneazetidine-2-carboxylic acid (= polyoximic acid; 1). The stable crystalline 3-azetidinone hydrochloride (18), obtained by hydrogenolysis of the known 1-(diphenylmethyl)-3-azetidenone (4), is described for the first time, From this key intermediate, 3-oxoazetidine-derived amides, exemplified by benzamide 12,urethanes (e.g. 17), and ureas (e.g. 20) can be prepared in good yield (Scheme 3). The olefination of 3-azetidinones with alkylidene(triphenyl)phosphoranes is a perparatively useful process only for derivatives with a pyramidal N-atom, e.g. the diphenylmethyl derivative 4, and not for the amide 12 or the urethane 17 (Scheme 4). 3-Alkylidene-azetidines with an amide N-atom should, therefore, be prepared by exchange of the N-substituent after the introduction of the double bond.
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  • 43
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    Absorption Spectra and Luminescence Properties of Isomeric Platinum (II) and Palladium (II) Complexes containing 1,1′-biphenyldiyl, 2-phenylpyridine, and 2,2′-bijpyridine as ligands (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1053-1059 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absorption spectra, luminescence spectra, and luminescence lifetimes of the isomeric [M(bph)(bpy)] and [M(phpy)2] complexes M = Pt(II) or Pd(II), bph2- = 1,1′-biphenyl-2,2′-diyl dianion, phpy- = 2-phenylpyridine-2′-yl anion, and bpy = 2,2′-bipyridine have been investigated and compared with those of [M(bpy)2]2+ complexes and of the free protonated ligands H2bph, Hbpy+, and Hphpy. In the absorption spectra, the region below 320 mm is dominated by ligand-centered (LC) transitions, whereas metal-to-ligand charge transfer (MLCT) transitions are responsible for the bands present in the near UV/VIS region. The MLCT bands move to higher energies on replacing Pt with Pd and in going from [M(bph)(bpy)] to the [M(phpy)2] isomer. For the mixed-ligand complexes, evidence for both M → bph2- (at higher energies) and M → bpy bands is found. The structured luminescence observed at 77 K shows lifetimes of 4.0 and 1.1 μs for [Pt(phpy)2] and [Pt(bph)(bpy)], respectively, and 480 and 250 μs for the analogous Pd complexes. On the basis of the energy and lifetime data, the luminescence of the Pt(II) complexes is assigned to the lowest triplet MLCT excited state, whereas for the Pd complexes the luminescent state is thought to result from a mixture of MLCT and LC triplet levels.
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  • 44
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    Ruthenium(II) Complexes with Three Different Diimine Ligands (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1108-1115 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of tri-heteroleptic complex of Ru(II) with diimine ligands is describe. Ten compounds [Ru(R2bpy) (biq) (L)][PF6]2 (R = H, CH3); L = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (Me2bpy), 2,2′-bipyrimidine (bpm), 2,2′-biisoquinoline (biiq), 1,10-phenanthroline (phen), dipyrido[3,2-c:2′,3′-e]pyridazine (taphen), 2,2′-biquinoline (biq), 6,7-dihydrodipyrido[2,3-b:3,2-j][1,10]-phenanthroline (dinapy), 2-(2[pyridyl)quinoline (pq), 1-(2-pyrimidyl)pyrazole] (pzpm), 2,2′-biimidazole (H2biim) are characterized by elemental analysis, electronic and 1H-NMR spectroscopy. The relative photosustitution rates of biq in MeCN are given at three temperatures.
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  • 45
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    (Benzylthio)- und (Arylthio)-substituierte Nitril-ylide: Thermische Erzeugung und Reaktionen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1177-1190 
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal Generation and Reactions of (Benzylthio)-and (Arylthio)-Substituted Nitrile YlidesThermolysis of 4-(benzylthio)- and 4-(arylthio)-1,3-oxazol-5(2H)-ones 6, at 110-155° in the presence of dipolarophiles with activated C≡C, C=C, C=O, C=S, and N=N bonds, led to 5-membered cyclo-adducts and CO2 (cf. Schemes 3, 5-7). Heating 6a and 6c in the presence of ethyl propiolate yielded ethyl quinoline-3-carboxylate (19) and ethyl pyridine-3-carboxylate(22), respectively (cf. Scheme 8). These results are rationalized on the basis of the intermediate formation of thio-substituted nitrile ylides of type 7 (cf. Scheme 2), which undergo regioselective 1,3-dipolar cycloadditions with reactive dipolarophiles. In the absence of such a dipolarophile, the nitrile ylides isomerize via a [1,4]-H shift to give 2-aza-1,3-butadienes of type 20. The latter are trapped in a Diels-Alder reaction with ethyl propiolate (cf. Scheme 8).
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  • 46
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    The Reversible Proxibarbal-Valofan Isomerisation. Part I. Kinetic and thermodynamic studies in aqueous solutions (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1220-1227 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tautomerisation between proxibarbal (I) and the two diastereoisomers of valofan, IIX and IIY, was investigated in aqueous solutions, and various rate and equilibrium caonstants were calculated by compartmental analysis. The proportion of I at equilibrium was found to increase with pH, and indeed, the two equilibrium constants are linear functions of pH. In contrast, the equilibrium-concentratio ratio of IIY/IIX was close to 63:37 and remained constant in the pH range investigated. The rate constants were also determined as a function of temperature, allowing calculation of the tehrmolynamic parameters. Under physiological conditions, the difference in free energy favouring I vs. IIX and IIY is 6.7 and 5.4KJ · mol-1, respectively.
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  • 47
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    Tandem Diels-Alder Reactivity Controlled by Remote Substituents. Regioselective synthesis of linearly annellated six-membered ring systems from (1RS,5SR,6RS,7SR)-6,7-bis(chloromethyl)-8,9-dimethylidene-2-oxabicyclo[3.2.2]nonan-3-one. Crystal structure of (1RS,5RS,6SR,11RS)-6,7-bis(chloromethyl)-3-oxo-2-oxatricyclo[7.4.0.1,5]tridec-8-en-11-yl methyl ketoneFor a preliminary communication, see [1].Part of the planned Ph. D. thesis of Bernard Demarchi, University of Lausanne. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1249-1267 
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthess of 6,7,8,9-tetramethylidene-2-oxabicyclo[3.2.2]nonan-3-one (12), 6,7,8,9-tetramethylidene-2-azatricyclo[3.2.2]nonan-3-one (13), and (1RS,5SR,6RS,7SR)-6,7-bis(chloromethyl)-8,9-dimethylidene-2-oxabicyclo-[3.2.2]nonan-3-one (14) are presented. The rate constants of the two successive Diels-Alder additions of a given dienophile to 12 and 13 were nearly the same. Lewis-acid-catalyzed Diels-Alder addition of methyl vinyl ketone to 14 gave adduct 39 with high regio- and stereoselectivity. Lewis acids isomerized 39 into(1RS,5RS,6SR,7SR,11RS)-6,7-bis(chloromethyl)-3-oxo-2-oxatricyclo[7.4.0.01,5]tridec-8-en-11-yl methyl ketone (40) whose structure was determined by single-crystal X-ray crystallography. Heating 39 with CsF/Cs2CO3 in DMF/HMPT gave (1RS,5RS,11RS)-6,7-dimethylidene-3-oxo-2-oxatricycl. [7.4.0.01,5]tridec-8-en-11-yl methyl ketone (42). The exocyclic butadiene moiety of triene 42 added to methyl propynoate and 2,3-didehydroanisole with good regioselectivity giving polysubstituted anthracenyl and naphthacenyl derivatives, respectively.
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    Präparative chromatographische Enantiomerentrennung von synthetisch nützlichen cyclischen AcetalenTeil der Doktorarbeiten von St. M. (Dissertation Nr. 8616, ETH Zürich, 1988), J. Z. (Dissertation Nr. 8518, ETH Zürich, 1988) und der geplanten Dissertation von U. G. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1303-1318 
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparative Chromatographic Resolution of Synthetically Useful Cyclic AcetalsRacemic cyclic acetals derived from aldehydes and glycine, glycolic acid, thioglycolic acid, formylacetic acid, and acetoacetic acid (oxazolidinones 4-13, dioxolanones 14, 15, oxathiolanone 16, dioxinones 17-23) are resolved by preparative high-pressure liquid chromatography on silica gel coated with the polymer from N-acryloylphenylalanine ethyl ester (Chiraspher®). The separation factors α range from1,1 to 2,4. Use of a Prepbar®-chromatography system allows injection of several grams at a time. The enantiomeric acetals thus obtained are fully characterized. First application to amino-acid synthesis are mentioned.
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  • 49
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    Stereoselectivity in Reactions of Metal Complexes. Part XPart IX: [1]. Kinetics and stereoselectivity of the inner-sphere electron-transfer reaction between [Co(bamap)H2O]+ (bamap = 2,6-bis(3-carboxy-1,2-dimethyl-2-azapropyl)pyridine) and optically active iron(II) complexes (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1339-1348 
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the electron-transfer reaction between racemic or optically active [Co(bamap)H2O]+ and optically active Fe2+ complexes of the three new pentadentate ligands bamap, alamp, and valmp has been investigated. All the reacting species show C2 symmetry. With respect to aquo-Fe2+, the reaction rate for the Fe2+ complexes is enhanced by a factor of 104 to 105, and the observed kΔΛ/kΛΛ ratio is 1.0, 1,9, and 1.2, respectively. In all cases where stereoselectivity is observed, the reaction is faster between the complexes of opposite absolute configuration (ΔΛ or ΛΔ) than between species with the same configuration (ΛΛ or ΔΔ). The stereoselectivity effects are discussed of the basis of the structure of the transition state and the interatomic distances between the two metal centers at the moment of electron transfer.
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  • 50
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/hlca.19880710601
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  • 51
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    Synthesis of (+)-1,3:2,5-dianhydroviburnitol ((+)-(1R,2R,3S,5R,6S)-4,7-dioxatricyclo[3.2.1.03,6]octan-2-ol) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1399-1405 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epoxidation of (-)-(1R,2R,4R)-2-endo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl acetate ((-)-5) followed by saponification afforded (+)-(1R,4R,5R,6R)-5,6-exo-epoxy-7-oxabicyclo[2.2.1]heptan-2-one ((+)-7). Reduction of (+)-7 with diisobutylaluminium hydride (DIBAH) gave (+)-1,3:2,5-dianhydroviburnitol ( = (+)-(1R,2R,3S,4R,6S)-4,7-dioxatricyclo[3.2.1.03,6]octan-2-ol; (+)-3). Hydride reductions of (±)-7 were less exo-face selective than reductions of bicyclo[2.2.1]heptan-2-one and its derivatives with NaBH4, AlH3, and LiAlH4 probably because of smaller steric hindrance to endo-face hydride attack when C(5) and C(6) of the bicyclo-[2.2.1]heptan-2-one are part of an exo oxirane ring.
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    Lavandulifolioside: A New Phenylpropanoid Glycoside from Stachys lavandulifolia (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1483-1490 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new phenlypropanoid glycoside has been isolated from the methanolic extract of the aerial parts of Stachys lavandulifolia (Lamiaceae), lavandulifolioside (1). On the basis of chemical and spectral data the structure of the new compound 1 has been elucidated as β-(3,4-dihydroxyphenyl)ethyl O-α-L-arabinopyranosyl-(1→2)-α-L-rhamnopyranosyl-(1→3)-4-O-caffeoyl-β-D-glucopyranoside.
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  • 53
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    Applications of ENDOR spectroscopy to radical cations in freon matrices. Part 2Part 1, see [1].. The radical cation of 2,3-diazabicyclo[2.2.2]oct-2-ene (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1498-1501 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical cation of 2,3-diazabicyclo[2.2.2]oct-2-ene (1), generated by γ-rays in a CF2ClCFCl2 matrix, has been fully characterized by its hyperfine data with the use of ESR, ENDOR, and TRIPLE resonance spectroscopy. The isotropic coupling constants for \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} are +3.14 mT for the two 14N Nuclei in the azo group, -0.336 mT for the two protons at the bridgehead C atoms, and +151 and +0.135 mT for the sets of four exo- and four endo-protons, respectively. MO calculations indicate that these values are consistent with an electron removal from an orbital represented by the antibonding combination (n_) of the lone-pair atomic orbitals at the two N atoms. The corresponding radical anion \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} is persistent in fluid solution and its hyperfine data, combined with MO calculations, point to an electron uptake into the antibonding π orbital (π*) of the azo group. It is, thus, reasonable to classify \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{+}\kern-4pt {.} }}$\end{document} as a σ and \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} as a π radical.
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    Semicorrin Metal Complexes as Enantioselective Catalysts. Part 1. Synthesis of chiral semicorrin ligands and general conceptsTaken in part from the Ph.d. thesis of H. F., ETH-Zürich (in preparation); for a preliminary communication, see [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1541-1552 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient synthesis of chiral semicorrin ligands is described (see 6-9, Schemes 2 and 3). Both enantiomers are readily obtained in enantiomerically pure form starting either from D-or L-pyroglutamic acid (1). Semicorrins of this type possess several features that make them attractive ligands for enantioselective control of metal-catalyzed reactions. Their structure is characterized by C2 symmetry, a conformationally rigid ligand system, and two stereogenic centers adjacent to the coordination sphere. In a metal complex, the two substituents at the stereogenic centers shield the metal atom from two opposite directions and, therefore, are expected to have a pronounced effect on the stereochemical course of a reaction occurring in the coordination sphere. The structure of these two substituents can be easily modified in a variety of ways. A series of (semicorrinato)copper(II) complexes (see 10-14, Scheme 4) has been prepared, and in one case (14), the three-dimensional structure has been determined by X-ray analysis (Fig. 1).
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    URL: http://dx.doi.org/10.1002/hlca.19880710620
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    Stereoselective synthesis of pyrrolo[2,3-d]pyrimidine α- and β-D-ribonucleosides from anomerically pure D-ribofuranosyl chlorides: Solid-Liquid Phase-Transfer Glycosylation and 15N-NMR Spectra (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1573-1585 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-liquid phase-transfer glycosylation (KOH, tris[2-(2-methoxyethoxy)ethye]amine ( = TDA-1), MeCN) of pyrrolo[2,3-d]pyrimidines such as 3a and 3b with an equimolar amount of 5-O-[(1,1 -dimethylethyl)dimethylsilyl]-2,3-O-(1-methylethylidene)-α-D-ribofuranosyl chloride (1) [6] gave the protected β-D-nucleosides 4a and 4b, respectively, stereoselectively (Scheme). The β-D-anomer 2 [6] yielded the corresponding α-D-nucleosides 5a and 5b with traces of the β-D-compounds. The 6-substituted 7-deazapurine nucleosides 6a, 7a, and 8 were converted into tubercidin (10) or its α-D-anomer (11). Spin-lattice relaxation measurements of anomeric ribonucleosides revealed that T1 values of H—C(8) in the α-D-series are significantly increased compared to H—C(8) in the β-D-series while the opposite is true for T1 of H—C(1′). 15N-NMR data of 6-substituted 7-deazapurine D-ribofuranosides were assigned and compared with those of 2′-deoxy compounds. Furthermore, it was shown that 7-deaza-2′deoxyadenosine ( = 2′-deoxytubercidin; 12) is protonated at N(1), whereas the protonation site of 7-deaza-2′-deoxyguanosine (20) is N(3).
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710623
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    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/hlca.19880710701
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  • 57
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    Synthesis and Characterization of Crown-Ether-Containing Phthalocyanines with Group-IV-A Elements (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1616-1621 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Group-IV-A phthalocyanines with four crown ether substituents have been prepared from 4′,5′-dicyanobenzo(15-crown-5), 4′,5′-diiminoisoindolino(15-crown-5), or metal-free phthalocyanine and the corresponding metal salts. The axial ligands of dichloro[tetra(15-crown-5)phthalocyaninato]silicon or -tin have been converted into dihydroxy derivatives by hydrolysis in aqueous Et3N. The catalytic effect of H2O-free CaC12 in quinoline is used for the polycondensation of dihydroxysilicon-phthalocyanine to cofacially arrayed polymers. The thermal stability of group-IV-A-metal phthalocyanines is confirmed by the higher initial decomposition points (290-440°) compared to those of the corresponding transition-metal phthalocyanines.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710705
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  • 58
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    Facile Synthesis of Carbon Monoxide Isotopically Labelled at Oxygen from Enriched Water without Isotopic Dilution (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1659-1660 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: O-Labelled carbon monoxide was prepared on the gram scale from enriched water and acetals of norborn-2-en-7-one(= bicyclo[2.2.1]hept-2-en-7-one) in almost quantitative yields and without isotopic dilution.
    Type of Medium: Electronic Resource
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  • 59
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    Syntheses of Amino-dideoxyallose and Amino-deoxyribose Derivatives Using Acylnitroso DienophilesDedicated to Professor Elias J. Corey on the occasion of his 60th birthday (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1642-1658 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dimethyl acetals 4 of (E)-2,4-pentadienal and of (E,E)- and (E,Z)-2,4-hexadienals undergo regio- and stereospecific cycloaddition reactions with in-situ-generated acylnitroso dienophiles 5a and 5b, leading thereby to the corresponding dihydrooxazines 7a-d and 8c-d. cis-Glycolization of these latter adducts stereospecifically gave the dihydro derivatives 9a-d and 10d which, after sequential hydrogenolysis, deacetalization, and instant cyclization, led to the aminodeoxyribose derivatives 17a, 17f, and 18, and to the amino-dideoxyallose compounds 17c and 17h. These piperidino-deoxysugar derivatives exhibit a strong anomeric effect, i.e. OH—C(1) is always axial, which is explained in terms of a nN(π)-σ*(C—OH) orbital compression, as compared to the less pronounced one in the more classical pyranose series.
    Additional Material: 8 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710709
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  • 60
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    1,3-Dipolare Cycloaddition aromatischer Nitril-ylide und Nitril-oxide an Dicyan und Diazocyanide (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1681-1688 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3 Dipolar Cycloaddition of Aromatic Nitrile Ylides and Nitrile Oxides with Cyanogen and DiazocyanidesNitril ylides 2 generated from the imidoyl chlorides 1 react with cyanogen and aryldiazocyanides to 2,5(4)-dia-ryl-1H-imidazole-4(5)-carbonitriles 3a,b or 5(4)-(arylazo)-2,4(5)-diaryl-1H-imidazoles 4a and 2,3,5-triaryl-2,3-dihydro-1H-1,2,4-triazole-1-carbonitriles 5a-f, respectively (Scheme 1). Reactions of benzonitrile oxides 7 with these dipolarophiles lead to 3,3′-diaryl-5,5′-bi[1,2,4]oxadiazoles 8a-c or 3-aryl-5-(arylazo)-1,2,4-oxadiazoles 9a-j (Scheme 2).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710714
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  • 61
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    Synthese der Spermidin-Alkaloide (±)-Inandenin-10-ol, Inandenin-10-on und (±)-OncinotinHerrn Prof. Dr. Duilio Arigoni zum 60. Geburtstag gewidmet. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1708-1718 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of the Spermidine Alkaloids (±)-Inandenin-10-ol, Inandenin-10-one, and (±)-OncinotineNew syntheses of the title compounds using two-ring-enlargement reactions are described. Starting from the aldehyde 1, the corresponding 4′-aza derivative 15 could be obtained by reductive amination with the appropriate and protected spermidine derivative 14 (Scheme 4). Enlargement of the carbocyclic ring in 15 by five members gave, after further transformations, the hydroxylactam 18. Transamidation of 18, the second ring-enlargement step, led to (±)-inandenin-10-ol (7;22.9% overall yield) and, after oxidation, to inandenin-10-one (8; 22.5%, overall yield). (±)-Oncinotine 6 was synthesized by two pathways (Scheme 6): protection of the terminal NH2 group by treatment with the Nefkens reagent and replacement of the OH group by Cl gave 24, which by thermal transamidation followed by direct ring closure led to the oncinotine derivative 26. The same intermediate could be obtained in higher yield via 28 by oxidation and protection of 18 followed by transamidation and reductive ring closure. Treatment of 26 with hydrazine finally gave (±)-oncinotine 6 in 15.9% overall yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710718
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    Diastereoselektive Alkylierung von 3-Aminobutansäure in der 2-StellungSir Derek Barton, zum 70. Geburtstag gewidmet (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1824-1839 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diastereoselective Alkylation 3-Aminobutanoic Acid in the 2-PositionThe enantiomerically pure 3-aminobutanoic acids (R)- and (S)-6 are readily available by preparative HPLC separation of the two diastereoisomers 5 obtained from addition of (S)-phenethylamine to methyl crotonate and subsequent hydrogenolysis (Scheme 2). (S)-Methyl 3-(benzoylamino) butanoate ((S)-3) is also available by enzymatic kinetic resolution with pig-liver esterase. The N-benzyl- and N- benzyloxycarbonyl derivatives rac3,8, and 9 of 3-aminobutanoates are doubly deprotonated with LDA and alkylated or aminated in high selectivity (17 examples, relative topicity like; see Tables 1 and 2). The configuration of three of the products is assigned (Schemes 4-6), and in four cases, the free α-substituted β-amino acid is prepared by acidic hydrolysis (see Table 3). It is shown that the doubly lithiated β-amino-acid derivative is solubilized, and its reactivity may be strongly influenced by the presence of 3 equiv. of LiCl.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710724
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  • 63
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    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/hlca.19880710801
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  • 64
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    Energy-Minimized Structures and Calculated and Experimental Isomer Distributions in the Hexaaminecobalt(III) system [Co(trap)2]3+ (trap = 1,2,3-propanetriamine) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1875-1880 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two isomers of [Co(trap)2]3+ (meso-[Co(trap)2]3+ and rac-[Co(trap)2]3+; trap = 1,2,3-propanetriamine) have been studied by strain-energy minimization. The two isomers have been separated preparatively by fractional crystallization, and fully characterized by 13C-NMR and electronic spectroscopy, and microanalyses. The calculated isomer distribution (rac/meso = 60%: 40%) is in good agreement with HPLC analysis of thermodynamic equilibrium mixtures at 298 K and 353 K (rac/meso = 55% : 45%). These results are discussed in relation to the approach of calculating isomer distributions of hexaaminecobalt(III) systems by strain-energy minimization neglecting the differences in environmental effects.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710805
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    Synthesis of New unnatural Macrocyclic Trichothecenes: 4-epiverrucarin A. 47th Communication on verrucarins and roridins46th Commun.: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1904-1913 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 4-epiverrucarin A (24), a new unnatural macrocyclic trichothecene, was synthesized starting from 4-epiverrucarol (20). The latter was obtained by metal-hydride reduction of the 4-oxo derivative 19. Subsequent conversion of 20 into the monoester 30 and then the diester 32 followed by macrolactonization of the latter yielded 4-epiverrucarin A (24). Attempts to invert the configuration of the naturally occuring 3α-OH group of a trichothecene were unsuccessful. The cytostatic (P-815) and immunosuppressive (MLR) activity of several natural and unnatural trichothecenes was determined in vitro.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710809
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  • 66
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    Steric Crowding in Coordination Compounds: Electron-transfer kinetics of the [Co(tmen)3]3+/2+ couple (tmen = 2,3-dimethylbutane-2,3-diamine) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1966-1970 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [Co(tmen)3]3+ complex ion (tmen = 2,3-dimethylbutane-2,3-diamine) has been synthesized and its redox characteristics compared to those of its parent ion [Co(en)3]3+. The 12 peripheral Me groups significantly affect the properties of the [Co(tmen)3]3+ ion. The ligand-field bands are shifted to lower energies by about 1700 cm-1 compared to [Co(en)3]3+. The reduction potential for [Co(tmen)3]3+ is +0.28 V (vs. NHE) compared to -0.18 V for [Co(en)3]3+. The rate of the self-exchange reaction for the [Co(tmen)3]3+/2+ couple, k = 8.5 × 10-8 M-1·S-1 was determined by applying the Marcus cross-relation with the reductants Cr2+, V2+, Eu2+, Ru2+, and [Co(sepulchrate)]2+.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710814
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    First Total Synthesis of Enantiomerically Pure(-)-Silphiperfol-6-en-5-onFor a Preliminary communication of this work, see [1a,b][2]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 569-576 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The angular triquinane (-)-silphiperfol-6-en-5-on ((-)-14) has been synthesized for the first time time in enantiomerically pure form. A highly efficient triplet-sensitized photoreaction, the oxadi-π-methane rearrangement of the complex β,γ-enone(+)-6 to (-)-7, constitutes the key step. The know staring material, (1R, 7aR)-3,6,7,7a-tetrahydro-1-hydroxy-7a-methyl-1H-inden-5(2H)-one ((-)-2), is readily accessible in 〉 97% enantiomeric purity. This new approach should enable access also to other angularly fused triquinanes of the silphinene type and related structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710309
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  • 68
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    Fredericone, neue hochfunktionalisierte Abietanoide aus Blattdrüsen von Coleus fredericii G. TAYL (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 577-587 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fredericon A, B, C, and D, Novel and Highly Functionalized Abietanoids from Leaf-Glands of Coleus fredericiiFrom the leaf-glands of the title plant (fam. Labiatae) two novel, genuie spirocycloopropyl-coleons have been isolated and structurally characterized. Fredericon A (1) bears the unusal 1,1,2-tricarbonylcyclopropane substructure that renders the molecule very suseptible to nucleophile-promoted rearrangements. Biogenetically intriguing is the presence of a 3-acetoxypropyl side-chain in fredericon B (3). Its formation from the well known isopropyl group is explained by transformation of the latter into a spirocyclopropane, followed by a reductive opening of the cyclopropane and reducation of the aldehyde, MeOH addition to 1, yields fredericon C (5), a derivative of 1H-phenanthro[3,2-b]pyran-7,12(2H,8H)-dione by two consecutive introlecular nucleophilic openings of the cyclopropane ring and the derived methoxy-oxirane. Similar methanolysis of a crude fraction of 1, produced, in addition to 5, the fredericon D, a novel derivative of 3H-phenanthro[3,2-b]pyran-2-(4H)-one(6).
    Additional Material: 3 Ill.
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    A new synthesis of N-acetylneuraminic acid (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 609-618 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthesis of N-acetylneuraminic acid (Neu5Ac; 28) via aldehyde 10 is described. The aldehyde 10 was obtained from N, acetyl-D-glucosamine (11; 5 steps, overall yield ca. 6%) or from D-glucono-1,5-lactone (17; 6 steps, overll yield ca 57%). Thus, on the one hand, N-acetyl-D-mannosamine (12), obtained from 11, was transformed into the known dithioacetal 14 and hence into the (ethylthio)dihydrooxazole 16, which was cleaved under weakly acidic conditions to the aldehyde 10. On the other hand, the known ester 18, obtained from 17, was sulfonylated and further transformed via the azide 20 into the N-acetyl-D-mannonate 22. Reduction of 22 to 23 and oxidation of 23 with ‘periodinane’ again gave 10. The aldehyde 10 was treated with the organozinc reagent 8 obtained from tert-butyl 2-(bromomethyl)acrylate (2) to yield predominantly 24, which was transformed (two steps) into the 2-methylidene-D-glycero-nononic acid 27 and hence into Neu5Ac (28).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710314
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    (-)-N-[(Cyclopropyl) methyl]-3,4-dimethoxy-5-methylmorphinan-6-one, an opioid agonist with preference for kappa opioid receptors (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 642-647 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Allyl- and N-[(Cyclopropyl)methyl]-3,4-dimethoxy-5-methylmorphinan-6-one (9 and 10, resp.) were synthesized from 5-methyldih drothebainone (1). This essential intermediate was prepared from the baine via 5-methylthebaine (5) employing a novel route. The Pharmacological studies showed 9 and 10 to be potent opioid agonists. Compound 10 was found to have preference for kappa rather than mu opioid receptors.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710318
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    Mécanisme de solvolyse des cis - et trans-(p-toluénesulfonates) d'aryl1-2-cyclopentyle II. Etude des étapes ultérieures à l'ionisation lors de la solvolyse des cis-(p-toluénesulfonates) d'aryl-2-cyclopentyle (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 658-673 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Solvolysis Mechanism of cis- and trans-2-Arylylopentylp- Toluenesulfonates, Subsequent Step in cis-2-Arylcyclopentyl p-Toluenesulfonate SolvolysisThe solvolysis of a series of 1-deuteriated, 2-deuteriated, and undeuteriated cis-2-arylcyclopentyl p-toluenesulfonates in HCOOH, AcOH, and EtOH has been studied. We have shown that classical secondary carbocation arising from substrate ionisation undergoes two concurrent processes, namely kc (direct products formation) and kip (hydrogenium bridged ion formation as tertiary carbocation or products precursor). The intrinsic properties of solvent and the aryl substitutant electronic effects the total solvolysis rate and the respective contributions of k c and k ip processes. Comparing the observed and calculated kinetic isotope of D-C(2) allows one to conclude that no step can called ‘rate-determining step’ but that the steps following ionisation have a preponderent effect on the total solovolysis rate.
    Notes: No abstract.
    Additional Material: 6 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710320
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    1H-and 13C-NMR study of the dilithium naphthalene and its TMEDA complex (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 694-702 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dilithium naphthalene (2) and its TMEDA complex 3 have been prepared, and their 1H-and 13C-NMR spectra were analyzed in terms of chemical shifts and coupling constants. From its Q value, 2 is characterized as delcoalized [4n] π system and the 1H - as well as the 6Li-NMR shifts classify the ion as strongly paratropic. For the quarternary C-atoms, a down-field shift of 30.4 ppm is observed. The conclusions drawn from the NMR parameters are compared with the results of MNDO calculations for naphthalene and biphenylene and their ions.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710403
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    Transition-metal complexes with bidentate ligands spanning trans-position. Part XVIPart XV:[1]. X-ray structural and 31P-NMR solution studies of 2,11-Bis(diethylphosphinomethyl)benzo[c]phenanthrenesilver(I) perchlorate (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 703-711 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of complexes {AgX(1c)} (X = Cl, Br, I, NO3 and ClO4; 1c = 2,11-bis(diethylphosphinomethyl)benzo[c]phenanthrene) is reported. The 31P-NMR spectra of the above complexes were recorded and the 1J(107Ag, 31P) values are compared with the corresponding data for related complexes. The X-ray crystal structure of [Ag(1c)](ClO4) was determined. There are two crystallographically independent molecules in the unit cell each containing two-coordinate silver, the O-atoms of the perchlorate anions being outside bonding range from the central atom. The two molecules, however, show different bonding parameters: Thus for ‘molecule 1’ P(1)—Ag(1)—P(2) = 167.6(1)°, Ag(1)—P(1) = 2.389(3) and Ag(1)—P(2) = 2.393(3) Å, while for ‘molecule 2’ P(3)—Ag(2)—P(4) = 164.8(1)°, Ag(2)—P(3) = 2.377(3), and Ag(2)—P(4) = 2.378(3) Å. These differences are probably due to packing forces in the crystal lattice.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710404
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    Anion-receptor molecules: Macrocyclic and macrobicyclic effects on anion binding by polyammonium receptor molecules (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 749-756 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability constants for anion binding by the acyclic hexaamine 1, its macrocyclic analogue 2, and the bicyclic compound 3 in their protonated forms are reported. Compound 3 forms stable and selective complexes with halide ions, the stability sequence being I- 〉 Br- 〉 Cl-. Compound 2 forms more stable complexes with sulfate, oxalate, and malonate dianions than its acyclic analogue 1 and shows a better selectivity pattern. Compound 3 forms stronger complexes with oxalate2- than 2 and shows a remarkably high binding selectivity between oxalate2- and malonate2-. The comparison of the ability of 1-3 to complex anions demonstrates the macrocyclic and macrobicyclic effects on anion binding stability and selectivity.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710409
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    Alkylation of Adenine, Adenosine, and NAD+ with 1,3-Propanesultone. Synthesis of N6-(3-sulfonatopropyl)-NAD+, a new NAD+ derivative with substantial coenzyme activity (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 762-772 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactivity of 1,3-propanesultone with adenine, adenosine, and NAD+ was studied in order to prepare N6-(3-sulfonatopropyl)-NAD+ (3b), a new NAD+ derivative substituted at the purine moiety with sunstantial coanzyme activity for several dehydrogenases. The regiochemistry of the alkylation at the purione nucleus was investigated by UV, 1H-NMR, and FAB-MS proved to be a powerful tool for determining the molecular weight of these polar and poorly volatile compounds. In addition, regular framgmentation of 3b and other NAD+ derivatives was observed.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710411
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  • 76
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    A (1,5)-Vinyl Shift (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 808-811 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of the by-product of the pyrolysis of 1 has been proved to be 3. It is proposed that a (1, 5) Shift of an (alkoxycarbonyl)vinyl group (8⇄10) is the step in formation of 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710415
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  • 77
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    Identifizierung von 2-Acetamido-2-desoxy-α-D-glucopyranosyl-1-phosphat in Kuhmilch als Wachstumsfaktor für Treponema vincentii (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 818-821 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Identification of 2-Acetamido-2-deoxy-α-D-glucopyranosyl 1-Phosphate in Cow-Milk as Growth Factor for Treponema vincentiiA 7:3 mixture of 2-acetamido-2-deoxy-α-D-glucopyranosyl and -α-D-galactopyranosyl 1-phosphate (1 and 2, resp.) was isolated from cow-milk and identified by 1H- and 13C-NMR spectroscopy. The 2-acetamido-2-deoxy-α-D-glucopyranosyl 1-phosphate is a growth factor for Treponema vincentii.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710417
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    The adamantane rearrangement of syn- and anti-Tricyclo[4.2.1.1.12,5] decane. Part IIFor Part I, see [1].. Rearrangements initiated by regioselective formation of carbocations at C(3) and C(9) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 848-858 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The endo- and exo-alcohols 5-12 of syn-(1) and anti-tricyclo[4.2.1. 12.5]decane (2) were treated with BF3/Et3SiH (ionic hydrogenation) in order to study the behaviour of the corresponding regioselectively generated carbocations at C(3) (a (syn), b (anti)) and C(9) (c (syn), d (anti)). The anti-hydrocarbon 2 is practically the sole product obtained starting with the four 3-alcohols (via a→b from 5 and 6 (syn) and via b from 9 and 10 (anti)). The four 9-alcohols in each case yield a mixture of 2-endo, 3-endo- (3) and 2-exo,3-exo-trimethylene-8,9,10-trinorbornane (4) (via c → e from 7 and 8 (syn) and via d → f from 11 and 12 (anti)), but no hydrocarbon 2, i.e. none of the 1,3-H shifts c → a and d → b is involved.
    Additional Material: 1 Ill.
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    Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part 1. Bromotri-μ-carbonyloctacarbonyltetrairidate(1-) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 867-871 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 2D and variable-temperature 13C-NMR study indicates that a CO-site exchange occurs in the title complex via several consecutive processes, the first being a ‘merry-go-round’ of the basal CO's, the second a switch of basal face not involving unbridged intermediates.
    Additional Material: 2 Ill.
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    Mitteilungen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 930-930 
    Details
    ISSN: 0018-019X
    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/hlca.19880710428
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  • 81
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    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/hlca.19880710501
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  • 82
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    EPC synthesesFor definition and discussion of the term, see [1]. from bicyclic dixoanones; (-)-5-epidehydrofukinone (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 977-980 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (-)-5-Epidehydrofukinone ((-)-15) has been synthesized from (2S,4aS,5S,8aS)-4a,5-dimethyl-2-(tert-butyl)-perhydro-4H-1,3-benzodioxan-4-one (4a), a counpound readily available by yeast reduction of ethyl 2-oxocyclohexanecarboxylate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710505
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  • 83
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    Synthese neuer Aryl-(3,-dichloro-4-pyridazinly)-ketone und ihre Reaktion mit N,N-DinucleophilenTeil der geplanten Dissertation von T. A. E. [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 988-991 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of New Aryl (3,6-Dichloro-4-pyridazinyl) Ketones and their Reaction with N,N-DinucleophilesThe synthesis of the new aryl (3,6-dichloro-4-pyridazinyl) ketones 3a-e vïa Friedel-Crafts acylation of the aromatic compounds 2a-e with 3,6-dichloro-4-pyridazincarbonyl chloride (1) is described. The ketones 3a-e cyclized with N,N-dinucleophilic reagents to the 3-aryl-5-chloro-l H -pyrazolo[3,4-c]pyridazines 4a-d, and 3a-c are converted into the 3-aryl-5-chloro-l H -pyrazolo[3,4-c]pyridazin - l -ethanols 5a-c and to the hitherto unknown ring system of the 5-aryl-3-chloro-7,8-dihydro-9 H -pyridazino[3,4-e][1,4]diazepines (6a-c).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710507
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    NorbornanesThe IUPAC name for norbornane: 8,9,10-trinorbornane.. Part 21. Bridging strain in norbornyl and oxanorbornyl cations (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1017-1024 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further evidence is presented that the 2-norbornyl cation is stabilized primarily by C(2)-C(6) bridging, and that C(2)-C(7) bridging leads to prohibitive strain. Thus, a comparison of the heats of hydrogenation of nortricyclene 17 and bicyclo[3. 2. 0. 0.2,7]heptane 18 indicates that the strain energy of the latter is ca. 21.5 kcal/mol higher that that of 17. Furthermore, 6-exo-2-oxabicyclo[2. 2. 1]heptyl sulfonates 8 ionize with strong O(2) participation to the bridged oxonium ion 12. In contrast, 2-endo-7-oxabicyclo[2.2.1]heptyl sulfonates 11 ionize without O(7) participation to form the unbridged carbenium ion 15.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710512
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    Synthesis and Characterisation of the Sodium and Lithium Cryptates of Macrobicyclic Ligands incorporating pyridine, bipyridine, and biisoquinoline unitsDedicated to the memory of Professor David Ginsburg (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1042-1052 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sythetic procedures have been deweloped for the preparation of sodium and lithium cryptates of the macrabicyclic ligands 1-11 containing pyridine, bipyridine, and biisoquinoline groups. They involve stepwise construction of the bicyclic system as will as direct macrobicyclisation procedures (Scheme 1) and give access to both symmetrical and dissymmetrical structures. Marked cation template effects have been found that facilitate the cyclisation processes. The ligands 1-11 were isolated as their cryptates with Na+ or Li+ cations.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710515
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    Asymmetric Catalysis by Vitamin B12. The isomerization of achiral epoxides to optically active allylic alcohols (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1073-1078 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Achiral epoxides are isomerized to optically active allylic alcohols under the influence of catalytical amounts of cob(I) alamin in protic polar solvents.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710520
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  • 87
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    4,10a-(Epidithio)-4,4a,10,10a-tetrahydro-1H-5-oxaanthracen-1-ones, tetracycles with a novel heterocyclic ring system (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1101-1107 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 4,4′,6,6′-tetrasubstituted 2,2′-alkylidene-bisphenols 1 reacted with sulfur monochloride to give 4,10a-(epidithio)-4,4a,10,10a-tetrahydro-1H-5-oxaanthracen-1-ones (3 and 4). The structure of the products were elucidated by a combination of X-ray crystal-structure analysis and 1H- and 13C-NMR spectroscopy.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710524
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  • 88
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    Synthesis and 1H-, 13C-, and 57Fe-NMR spectra of mono- and bis[tricarbonyl(η4-diene)iron], and (η3-allyl)tetracarbonyliron trifluoroborate complexesTransition-Metal NMR Spectroscopy, Part XI. Part X: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1116-1142 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variety of mono- and bis[Fe(CO)3(η4-diene)] complex with alky, CH2OH, CHO, COCH3, COOR, and CN substituents on the 1,3-diene system have been synthesized. Dienes with a (Z)-configuration terminal Me group show steric inhibition of metal complexation resulting in lower yields and formation of tetracarbonyl(η2-diene) and tricarbonyl(η4-heterodiene) complexes as additional products. Regioselective attack by C-nucleophiles at the carbonyl C-atoms of the functional group with or without concomitant 1,3 mogration of the Fe(CO)3 group was used to synthesize polyenes and isoprenoid building blocks as mono- or dinucliar Fe(CO)3 complexes. Wittig-Horner-type reactions of Fe(co)3-complexed synthons result in sterospecific formation of (E)-configurated olefins. The 1H-, 13C- and 57Fe-NMR spectra of olefinic and allylic organoiron complexes are reported, H,H,C,H, and C,C coupling constants have been evaluated and are analyzed in terms of the geometry of the coordinated diene. The results are corroborated by the crystal structure of tricarbonyl[3-6-η-((E)-6-methyl-3,5-heptadiene-2-one)]iron(34) which shows an unusual distortion of the (CH3)2C = group, The 57Fe-NMR chemical shifts extend over the ranges of 0-600 ppm for [Fe(CO)3(η4-diene)] complexes, 780-1710 ppm for [Fe(CO)4(η3-allyl)] [BF4] and [FeX(CO)3(η4-allyl)] complexes, and 1270-1690 ppm for [Fe(CO)3(η4-enone)] complexes, relative to Fe(CO)5.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710526
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    Colchicine Models: Synthesis and Binding to Tubulin of Tertamethoxybiphenyls (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1199-1209 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheis of tetramethoxybiphenyl 21 was accomplished from 4-phenylcylohexane-1,3-dione 13 by aromatization to biphenyl 19 and reductive removal of the phenolic OH group as phenyltetrazolyl ether. Tertramethoxybiphenyls 34 and 40 were obtained from 4-phenylcyclohexenone 26 via ester 27. The tetramethoxybiphenyls 21, 34, and 40, and analogs 28, 29, and 31 were evaluated for antitubulin activity and as antimitotic agents with L1210 murine leukemia cells. Compounds 31 and 34 had significant effects on the in-vitro polymerization of tubulin. Compound 31 was the most cytotoxic of the six new biphenyls studied (IC50 for cell growth, 0.6M) and caused the accumulation of cells in metaphase arrest.
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    URL: http://dx.doi.org/10.1002/hlca.19880710531
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    The Reversible Proxibarbal-Valofan Isomerisation. Part II. Kinetic studies in a biphasic octanol/water system (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1228-1234 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tautomerisation between proxibarbal (I) and the two diasterloisomers of valofan (IIX and IIY) was investigated at pH 7.4 in a biphasic octanol/H2O system. The rate constants of isomerisation and the equilibrium constants of (partition coefficients) were calculated by compartmental analysis. The rate constants of isomerisation were comparable with those determined in monophasic aqueous solutions, whereas at pH 7.4 and 37° the duration necessary for a global equilibrium to be reached was 4-6 times longer in the biphasic system. These reduced rates and the higher lipophilicity of IIX and IIY as compared to I may be of pharmacokinetic and pharmacodynamic significance. They may also have relevance for a number of drugs known or suspected to form lactonic or lactamic metabolites.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710534
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    Conformational Flexibility of the Methoxyphenyl Group Studied by Statistical Analysis of Crystal Structure Data (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1291-1302 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a large sample of observed methoxyphenyl groups, the twist angle τ about the MeO-CPh bond measuring internal rotation of the MeO group shows a continuous distribution with maxima at (0°) (coplanar conformation) and (∼90°) (perpendicular conformation). The preferred conformation of methoxyphenyl depends on the nature of the ortho--substituents: In general, it is coplanar in the case of one or two ortho-hydrogens, and perpendicular in the case of two substituents. The internal rotation of the MeO group is accompained by systematic variations in bond angles and bond distances: 1 if MeO is twisted out of plane, the bond angle CH3—O—CPh decreases from 117.7°, until it reaches a minimum of 114.9° at τ = ±90°. The O—C—C angle which is syn to CH3 for τ = 0° decreases from 124.6° to a minimum of 115.4° at τ = ±180°. These angles changes keep the nonbonded distance CH3 … ortho substituent maximal during internal rotation of MeO and tend to minimize the corresponding strain energy. (2) In the perpendicular conformation, the O-atom is ∼ 0. 06 Å displaced from the Ph plane, O and CH3 and being on opposite sides of this plane. In addition, small but systematic increases of bond lengths MeO—CPh and CH3—O are observed. These variations indicate a decrease in conjugation with increasing twist angle. Their interdependence during twisting and the magnitudes of the changes are close values obtained by ab initio calculations.
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    Studies on the Biosynthesis of Iridals and Cycloiridals (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1331-1338 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The incorporation of [2-14C]acetate, [2-14C]mevalonate, and [3H]squalene proved the squalenoid nature of the iridals, novel triterpenoids from rhizomes of swordlilies. Methionine is readily incorporated into cycloiridalls of Iris pallida dalmatica, thus indicating that the methylation of iridals via S-adenosyl-L-methionine leads to the formation of the irone moiety of the bicyclic compounds. The 3H/14C ratio of the transferred labelled methyl group remained unchanged. Therefore, the methylation/cyclization of the terpenoid side chain of iridals must proceed by a concerted mechanism without formation of a cyclopropanoid intermediate.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710544
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    The Reaction of Water with Iron- and Rutheniuncarbonyl Complexes of Polyolefins: 1,2- and 1,4-hydrogenation of 1,3-dienes. hydrogenolysis of allylic ethereal bonds and deoxygenation of 7-oxabicyclo[2.2.1]hept-2-enes (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1354-1366 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under basic conditions, H2O reacts with tricarbonyl[(1R,2R,3S,4S,5R,6S)-C,5,6,C-η-(2-exo,3-exo-bis-(chloromethyl)-5,6-dimethylidene-7-oxabicyclo[2.2.1]heptane)]iron) (1), and -ruthenium (4), with tricarbonyl-[(1R,2R,3S,4S)-C,2,3,C-η-(2,3,5,6-teramethylidene)-7-oxabicyclo[2.2.1]heptane)]iron (6) and -ruthenium (7), and with cis-η-[1S,2S,3R,4S,5S,6R)-C,2,3,C-η : C-η-(2,3,5,6-tetramethylidene-7-oxabicyclo)[2.2.1]heptane)bis-(tricarbonyliron) (11)] to give products of demetallation and 1,2- or/and 1,4-hydrogenation. Reductive demetallation of tricarbonyl[C,5,6,C-η-(1-(dimethoxymethyl)-5,6-dimethylidenecylohexa-1,3-diene]iron (14) required heating under acidic conditions, giving 2,3-dimethylbenzaldehyde (16). H2O reacted under neutral conditions with cis-heptacarbonyl-μ-[(1RS,2SR,3RS,4SR,5RS,6SR)-2,3-η : C,5,6,C-η-(1-(dimethyoxymethyl)-5,6,-(dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene]diiron (17) and with tricaboyl[(1RS,2SR,3RS,4SR,5RS,6SR)-C-η5,6,C-η-(1-(dimethyoxymethyl)-5,6-dimethyldidene-7-oxabicyclo[2.2.1]hept-2-ene)]iron (18) to give the orthoquinodimethane complex 14 as major product. This reaction was accompanied by hydrogenolysis of the allylic ethereal C(4)—O(7) bond in 17 and 18 and gave tricarbonyl[(1RS,5RS,6SR)-C,5,6,C-η-(1-(dimethoxymethyl)-5,6-dimethylidenecylohex-2-en-1-ol)]iron (21) as minor product. The latter was not an intermediated of reaction 17 → 14. Reactions with D2O allowed one to discuss the possible mechanism of this deoxygenation process. With Trans-heptacarbonyl-μ-[(1RS,2SR,3RS,4SR,5RS,6SR)-2,3-η : C,5,6,C-η-(1-(dimethoxymethyl-5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene)diiron (38)], the reaction with THF/H2O gave 14 nearly quantitatively, with no D-incorporation in the presence of D2O.
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    Mitteilungen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1379-1381 
    Details
    ISSN: 0018-019X
    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/hlca.19880710549
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  • 95
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    Electronic Resource
    The solution structure and reactivity of decavanadate (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1406-1420 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxygen-exchange reaction of V10O286- with bulk water has been followed by time-dependent 17O-NMR spectroscopy (buffered solutions, pH ∼ 5.5, [V10]total ∼ 0.17m, T = 298 K). It is shown that all seven structurally different sites of O-atoms are kinetically similar but, in contrast to earlier studies, not identical (6 h ≤ ‘t1/2’ ≤ 11 h). The kinetic similarity of the various structural sites implies the some (but not full) O scrambling is involved. Two possible mechanisms with a ‘half-bonded’ and an ‘open’ intermediate are discussed in detail to interpret the experimental results. A computer simulation of the exchange reaction based on these models is presented. It is shown that the ‘half-bonded-intermediate’ mechanism is consistent with the experimental data and the following parameters are calculated: formation of the intermediate: k1 = 5.8 · 10-3 s-1, k-1 = 6.7 · 10-2 s-1, [intermediate]∞ ≈ 8%; all activated O-atoms exchange within the lifetime of the intermediate (τ ∼ 15 s), and the calculated exchange rate of the intermediate (k2 ≥ 0.60 s-1) is consistent with earlier assumptions (k2 ≈ 0.5 s-1). It is shown that a simulation based on the ‘open-intermediate’ mechanism results in kinetic parameters which are not consistent with the kinetics of the formation of cyclic metavanadates ((VO3-)n, n = 4,5) from decavanadate, since the required formation rate is by a factor ∼ 102 too fast, and the equilibrium concentration of metavanadates is by a factor of ∼ 2 too large (under the conditions of the O-exchange experiments of decavanadate (T = 298 K, [V10]total ≈ 0.17m, pH ∼ 5.55) the total amount of metavanadates present is ∼ 8%, with [(VO3-)4]/[(VO3-)5] ∼ 4:1; a qualitative analysis of the kinetics of the formation of metavanadates (vo kinetics; the exact mechanism of the back-reaction (at least second-order) is not known with certainty) leads to k1 ≥ 4·10-5 s-1). O exchange of decavanadates via equilibrated metavanadates would lead to full scrambling of the O sites and is not consistent with the observed differences in the exchange rates. From the qualitative kinetic parameters of the metavanadate formation kinetics, it can be concluded that any contribution of an ‘open’ or an ‘metavanadate’ mechanism is of the order of 1-2% at most.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710605
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  • 96
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    Reaktionen des Cumalinsäure-methylesters und Cumalinaldehyds mit ambidenten Nucleophilen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1467-1473 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of Methyl Coumalate and Coumalaldehyde with Ambident NucleophilesMethyl coumalate and coumalaldehyde show great diversity in their reactions with ambident nucleophiles both depending upon the 2H-pyran-2-one derivative and the nature of the ambident nucleophile used. The products are either pyridine or pyrimidine derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710610
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  • 97
    Electronic Resource
    Electronic Resource
    Rosafluin, ein neues Diapocarotindiol aus Rosenblüten. 8. Mitteilung über Rosenfarbstoffe7. Mitteilung: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1491-1497 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rosafluine, a Novel Diapocarotenediol from Rose PetalsA strongly fluorescent trace compound from rose petals was identified as the as yet unknown 10,10′-diapocarotene-10,10′-diol ( = 4,9-dimethyldodeca-2,4,6,8,10-pentaene-1,12-diol; 2).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710613
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  • 98
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    Efficient Synthesis of 1,2-Bis(2,2′-bipyridinyl)ethane and 1,2-bis(1,10-phenanthrolinyl)ethane ligands by oxidative coupling of the corresponding monomeric methylene carbanions (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1511-1516 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several dimeric 1,2-bis (2,2′-bipyridinyl)ethane (1,2,6,7, and 9 and 1,2-bis(1,10-phenanthrolinyl)) ethane (3,4, and 5) ligands have been synthesized in high yield by oxidative coupling of the corresponding monomeric methylene carbanions using as oxidating agents Br2, I2, and 1,2-dibromoethane. The structure of the compounds obtained from three tetramethyl-2,2′-bipyridines and one tetramethyl-1,10-phenanthroline have been assigned on the basis of their 1H-NMR spectra. The electronic absorption and emission properties of these new ligands are reported. They display intense fluorescence spectra.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710617
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  • 99
    Electronic Resource
    Electronic Resource
    Synthesis and Characterization of DNA Fragments Bearing an Adenine Radiation Product: 7,8-Dihydroadenin-8-one (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1566-1572 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 7,8-dihydroadenin-8-one is one of the base derivatives formed by the action of ionizing radiation upon DNA. In order in investigate the mutagenic effects and the repair of DNA lesions induced by gamma rays, the synthesis of oligonucleotides bearing this damage has been performed by the phosphoramidite methodology. The preparation of the corresponding protected mononucleotide 6 (see Scheme) and its insertion into a DNA fragment are described. The modified oligonucleotide was purified by HPLC, characterized by DNA sequencing, enzymatic hydrolysis, and FAB mass spectrometry. In the experimental conditions used herein, no basic or acidic degradation was observed. In the DNA chain, the lesion is stable on piperidine heating under the usual DNA sequencing conditions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710622
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  • 100
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    Electronic Resource
    β-Cleavage of Bis(homoallylic) Potassium Alkoxides. Synthesis of γ-damascone (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1587-1597 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from the γ-lactone cis-1, two new syntheses of γ-damascone ((E)-4) are described. In both syntheses, the key step involves the β-cleavage of a bis(homoallylic) potassium alkoxide, viz. the transformation of 3a to 20 and (E/Z)-4, and the conversion of 21a to 23 and (E/Z)-24.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710702
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