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  • Organic Chemistry  (362)
  • 1995-1999  (362)
  • 1980-1984
  • 1975-1979
  • 1998  (362)
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  • 1995-1999  (362)
  • 1980-1984
  • 1975-1979
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 362-363 
    ISSN: 0899-0042
    Keywords: Jacobsen's catalyst ; enantiomeric purity determination ; chiral HPLC ; cyclodextrin chiral stationary phases ; enantioseparation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A HPLC method is described for the chiral analysis of the commercially available Jacobsen's catalyst. A hydroxypropyl β-cyclodextrin stationary phase was used in conjunction with a nonaqueous, polar-organic mobile phase. The method can be applied to control the enantiomeric purity of the catalyst, which is of great importance for quality control of that product. High accuracy in the determination of trace levels of the unwanted enantiomer in the presence of large amounts of the desired enantiomer is demonstrated. Chirality 10:362-363, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 274-277 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 755-756 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal reaction of Fischer carbene complexes 1 - 3 with cyclooctyne 4 followed by oxidation with Ce(IV)ammonium nitrate furnished tricyclic quinone derivatives 5 - 7 incorporating an eight-membered ring.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 204-213 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 1-O-trimethylsilyl-glycoses, 1-O-acylglycoses and glycosyl fluorides, respectively, with silylated alcohols (glycodesilylations) are summarized. Synthetic strategies toward oligosaccharides using glycodesilylations are discussed as well and some typical experimental procedures are given.
    Additional Material: 3 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 210-216 
    ISSN: 0899-0042
    Keywords: enantiospecific assay ; rat ; dog ; human ; enantiomer disposition ; HIV protease inhibitor ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: PNU-103017, 4-Cyano-N-(3-(cyclopropyl(5,6,7,8,9,10-hexahydro-4-hydroxy-2-oxo-2H-cycloocta(b) pyran-3-yl)methyl)phenyl)-benzenesulfonamide, is a selective HIV aspartyl protease inhibitor under evaluation as a potential oral treatment of Acquired Immunodeficiency Diseases. PNU-103017 is a racemic mixture of two enantiomers, designated PNU-103264 (R-) and PNU-103265 (S-). Stereoselective pharmacokinetics of the two enantiomers of PNU-103017 were observed in the dog, rat, and human after single and multiple dose administration of the racemate and were apparently species-dependent. Mean enantiomeric ratios of plasma concentrations (R-/S-) at each time point were greater than 1 in the dog, ranging from 1.22 to 3.06, but less than 1 in the rat and in the human, ranging from 0.44 to 0.80 and 0.23 to 0.73, respectively. A trend towards increased or decreased (farther from 1:1, R-/S-) enantiomeric ratio of plasma concentrations with time after each administration was also observed. The enantiomeric ratio remained unchanged after multiple dose administration in the rat, dog, and human although enzyme induction and increased plasma clearance were observed for both enantiomers. Chirality 10:210-216, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 81 (1998), S. 174-181 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (S)-5,5,5,5′,5′,5′-Hexafluoroleucine ((S)-13) of 81 % ee is prepared from hexafluoroacetone (l) and ethyl bromopyruvate (= ethyl 2-oxopropanoate) in 7 steps with an overall yield of 18% (Schemes 1 and 2). Key step in this sequence is the highly enantioselective reduction of the carbonyl group in α-keto ester 4 either by bakers' yeast (91 % ee) or by ‘catecholborane’ 6 utilizing an oxazaborolidine catalyst, yielding hydroxy ester (R)-5 with 99% ee. The absolute configuration was determined by X-ray analysis of the HCl adduct (S,R)-9b of (2S)-N-[(R)- l-phenylethyl]-5,5,5,5′,5′,5′-hexafluoroleucine ethyl ester.
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 81-83 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 676-681 
    ISSN: 0899-0042
    Keywords: β-glucosidase from almond ; reverse hydrolysis ; transglucosylation ; enantioselectivity ; enantiomeric excess ; absolute configuration ; alkyl β-D-glucopyranoside ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Almond β-glucosidase was used to catalyze the synthesis of alkyl β-d-glucopyranosides 1b-3b starting from either d-glucose (4) or phenyl-β-d-glucopyranoside (5) and the racemic alcohols 1a-3a. The enzymic reactions were provided in different acetonitrile/water mixtures [9:1 (v/v) for the reverse hydrolysis, and 1:9 (v/v) for the transglycosylation]. Both enzymic reactions, that is, the reverse hydrolysis and the transglucosylation, are enantioselective processes. The enantiomeric purity of products 1b-2b of the enzymic reactions varied between 75 and 86% ee, the values of which were based on the analysis of the aglyconic parts (1c-2c) of the alkyl β-d-glucopyranoside molecules (1b-2b). Chirality 10:676-681, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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  • 9
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of α-nitro ketones to the corresponding α-hydroxy ketones under basic aqueous conditions, a novel transformation, was studied. The investigation revealed that the reaction is only possible with α-nitro ketones that are CH-acidic in the α′-position and readily deprotonated under the reaction conditions. The NO2/OH exchange was established to proceed with retention of configuration at the stereogenic center, and labeling experiments have shown that the OH O-atom originates, to a great extent, from the solvent. In particular, the stereochemical course of the reaction and the incorporation of external nucleophiles led us to propose a mechanism that involves neighboring-group participation. The product formation is explained by a double SN2 reaction, which proceeds via a Favorskii-like cyclopropanone intermediate.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 742-746 
    ISSN: 0899-0042
    Keywords: methamphetamine ; enantiomer ; serum albumin ; CD spectra ; association equilibrium ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The association equilibria for complex formation between serum albumin (bovine, rat) and the optical isomers of methamphetamine (MAMP) was determined using an ultrafiltration method. It was found that serum albumin/d-MAMP and serum albumin/l-MAMP complexes had distinctly different Scatchard plots with bovine and rat albumin. The binding parameters of each association equilibrium were estimated from the Scatchard plots by Rosenthal's graphic method. This distinguished two kinds of specific binding sites in terms of the association equilibrium between bovine serum albumin and d-MAMP, and one binding site for rat serum albumin and d-MAMP. One specific binding site was found between serum albumin and l-MAMP in both bovine and rat. Molar ellipticities, [θ], of peaks were decreased in the CD spectra of the complexes formed between bovine serum albumin and d-MAMP or l-MAMP when compared with the CD spectrum of bovine serum albumin alone. However, no difference in [θ] was found between the CD spectra of the enantiomers of MAMP in the measured wavelength range. The non-specific binding site was distinct from the specific binding site and resulting from altered tertiary structure of the albumin molecule. Chirality 10:742-746, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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