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  • Organic Chemistry  (35)
  • 2020-2023
  • 1995-1999  (26)
  • 1970-1974  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Enzymatic Cleavage of N-Phenylacetyl-Protected Ethanolamine Phosphates (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1215-1220 
    Details
    ISSN: 0947-3440
    Keywords: L-glycero-α-D-manno-Heptopyranosides ; Ethanolamine phosphates ; Phenylacetyl, enzymatic cleavage of ; Carbohydrates ; Glucosylations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Immobilized penicillin-G acylase mediated removal of the N-phenylacetyl protective group in ethanolamine phosphates 7 and 9 furnished compounds 8 and 10, respectively. Deblocking of N-phenylacetyl-protected ethanolamine phosphate heptosyl disaccharide 22, a protected spacer-containing fragment of the inner-core lipopolysaccharide region of Neisseria meningitidis, immunotype L3 was readily accomplished with penicillin-G acylase, yielding target dimer 2. Disaccharide 22 was accessible by elongation of ethyl 1-thio-L-glycero-α-D-manno-heptopyranosyl donor 13 with acceptor 14 under the influence of N-iodosuccinimide/triflic acid. Protective group manipulations, phosphorylation with the reagent 2-cyanoethyl 2-(phenylacetylamino)ethyl N,N-diisopropylphosphoramidite (5) and deprotection furnished LD-Hepp dimer 22.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970625
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  • 2
    Electronic Resource
    Electronic Resource
    Biscalix[4]arene Ligands for Dinuclear Lanthanide Ion Complexation (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2587-2600 
    Details
    ISSN: 0947-3440
    Keywords: Biscalix[4]arene ; Lanthanide ions ; Energy transfer ; Luminescence ; Dinuclear complexes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three types of lower-lower rim linked biscalix[4]arenes that contain carboxylic ester (1) and/or amide functions (2 and 3) at their remaining phenolic oxygen atoms were synthesized. The homo- and heterodinuclear lanthanide ion complexes based on these ligands were used to study the energy transfer between different lanthanide ions. Photophysical studies comparing the luminescence properties of the homodinuclear Eu3+ complex and the heterodinuclear Eu3+-Nd3+ complex of 2 indicated that energy transfer is likely to occur from Eu3+ to Nd3+ with an efficiency of 〉 50%. The luminescence properties turned out to be strongly solvent dependent, which is attributed to structural changes leading to different positions of the lanthanide ions in the cavities provided by the biscalix[4]arene.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971226
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesen von Cholinphosphatiden, VI1) 3-Palmitoyl-glycerin-1-phosphorylcholin (D-α-Lysolecithin) und dessen Unwirksamkeit als Substrat für Acyltransferasen (Lecithin-Synthese) (1970)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 738 (1970), S. 161-169 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of Choline Phosphatides, VI1).3-Palmitoyl-glycerol-I-phosphorylcholine (D-α-LySO-lecithin) and its Inactivity as Substrate for AcyltransferasesEnzyme reactions controlling the content of the strong lytic agent lysolecithin (monoacylglycerol-3-phosphorylcholine) in cell membranes, i. e. by degradation or by reacylation, are of great importance for the living cell. Lysolecithins, well defined with respect to configuration and structure, can be used as substrates for studying the metabolic fate of these compounds in membranes. Five of the six theoretically possible isomers of lysolecithin have been prepared by De Haas and Van Deenen (1965). - In this paper the synthesis of the hitherto unknown 3-acyl-glycerol-I-phosphorylcholine (B) is described. 3,4-lsopropylidene-D-mannitol (1) has been benzylated to give 1,2,5,6-tetrabenzyl-3,4-isopropylidene-D-mannitol (2). Acid hydrolysis
    Notes: Als Modellsubstanzen für biologische Untersuchungen sind einheitliche, konfigurativ eindeutige Lysolecithine von allgemeinem Interesse. Wir beschreiben erstmals die Synthese eines 3-Acyl-glycerin-1-phosphorsäurecholinesters (B) 3.4-Isopropyliden-D-mannit (1) wird zur Tetrabenzyl-Verbindung 2 benzyliert. Saure Hydrolyse von 2 ergibt 1.2.5.6-Tetrabenzy-D-mannit (3), der mittels Bleitetraacetat zu 1.2-Dibenzyl-glycerinaldehyd (4) Gespalten wird. Reduktion von 4 mit Lithiumalant führt zum 1.2-Dibenzyl-glycerin(5), das durch Veresterung mit Palmitinsäurechlorid das 3-Palmitoryl-Dibenzyl 6 liefert. Aus 6 erhält man bei der katalytischen Hydrogenolyse 2-Benzyl-und 1-Benzyl-3-palmitoyl-glycerin (7bzw. ),die chromatographisch getrennt werden . die Phosphorylierung von 7 mittels ß-Brom-äthyl-dichlorphosphat und die nachfolgende Behandlung mit Trimethylamin ergeben 3-Palmitoyl 2-benzyl-glycerin-1-phosphorylcholin (9), das durch katalytische Hydrogenolyse in 3-Palmitoyl-glycerin-1-phosphorylcholin (10) umgewandelt wird. - Das so dargestellte D-αLysolecithin erweist sich im Gegensatz zu 1 -Palmitoyl-glycerin-3-phosphorylcholin (L-α-Lyso-lecithin) nicht als Substrat für Acyl-CoA : Acylglycerinphosphorylcholin-Acyltransferasen,
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19707380118
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  • 4
    Electronic Resource
    Electronic Resource
    Toxic doses of rac-, (-)-(S)- and (+)-(R)-propranolol in rats and rabbits (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 411-417 
    Details
    ISSN: 0899-0042
    Keywords: rac-propranolol ; enantiomers ; drug intoxication ; cardiovascular function ; respiratory function ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The contribution of the individual enantiomers ([+]-[R]- and [-]-[S]-propranolol) to rac-propranolol intoxication was studied in anaesthetized, spontaneously breathing (SB) rats and artificially ventilated (AV) rats and rabbits. In the SB rat, propranolol (30 mg.kg-1.h-1 i.v.) decreased heart rate and mean arterial blood pressure and caused hypoventilation, serious hypoxaemia, respiratory acidosis, and death by respiratory arrest. Survival time (ST) in the (+)-(R)-propranolol group (ST 91 ± 5 min) was significantly longer than in the rac-propranolol group (ST 68 ± 6 min). In AV rats and rabbits toxic doses of rac-, (-)-(S)- and (+)-(R)-propranolol, 30 mg.kg-1.h-1 and 15 mg.kg-1.h-1 i.v., respectively, induced comparable effects on haemodynamic variables as in the SB rat. Artificial ventilation lengthened ST by a factor of three to four in rats. In the AV rat, ST's were not significantly different between the rac-, (-)-(S)- and (+)-(R)-propranolol groups. In the rabbit, as in the SB rat, ST in the (+)-(R)-propranolol group was significantly longer than ST's in the rac- and (-)-(S)-propranolol groups. The acute respiratory acidosis in SB rats and the prolonged ST in AV rats suggest that respiratory failure is the primary and cardiovascular failure the secondary cause of death in propranolol intoxication. The potentiation of the toxic effect of the enantiomers observed after dosing the racemate instead of the pure enantiomers could not be explained by a stereoselective difference in plasma propanolol concentration. © 1996 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of the enantiomers of citalopram, its demethylated and propionic acid metabolites in human plasma by chiral HPLC (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 389-395 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective HPLC ; depressive patients ; citalopram ; enantioselective metabolism ; human plasma ; racemization ; optical rotation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereoselective HPLC assay has been developed to analyze the enantiomers of citalopram and of its three main metabolites in plasma after their separation on a Chiracel OD column. Using a fluorescence detector, the limit of quantification in plasma samples was 15, 4, 5, and 2 ng/ml for the enantiomers of citalopram (CIT), desmethylcitalopram (DCIT), didesmethylcitalopram (DDCIT), and for the citalopram propionic acid derivative (CIT-PROP), respectively. Except for CIT, all metabolites were derivatized with achiral reagents. Identification of the enantiomers was realized with an optical rotation detector which showed that the enantiomers invert their rotation depending on the polarity and nature of the solvent. Under varying conditions, a racemization study has shown that the pure enantiomers of CIT and its demethylated metabolites are configurationally stable. Preliminary results obtained with five patients treated with CIT show a mean S/R ratio of 0.7 for both CIT and its active metabolite DCIT and of 3.6 for CIT-PROP in plasma. This suggests that the pharmacologically relevant (+)-(S)-isomers of CIT and DCIT could be preferentially and steroselectively metabolized to CIT-PROP. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070602
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  • 6
    Electronic Resource
    Electronic Resource
    Combined non-enzymatic and enzymatic reduction favors bioactivation of racemic lipoic acid: an advantage of a racemic drug? (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 362-366 
    Details
    ISSN: 0899-0042
    Keywords: lipoic acid ; reduction ; dihydrolipoamide dehydrogenase ; antioxidant ; enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the antioxidant effect of lipoic acid, reduction to dihydrolipoic acid is considered to be important. Dihydrolipoamide dehydrogenase (LipHD) preferentially reduces R-lipoic acid and in a subsequent reaction, the R-dihydrolipoic acid formed may non-enzymatically reduce S-lipoic acid. Using circular dichroism (CD) spectroscopy, the second order rate constant of the latter reaction was determined (k2 = 15 M-1 sec-1). In vitro, it was found that S-lipoic acid is reduced by LipDH using R-lipoic acid as a catalyst. The non-enzymatic dithiol-disulfide reaction leads to synergistic reduction of the enantiomers which can explain the higher antioxidant activity of racemic lipoic acid found in vivo (Maitra et al. Biochem. Biophys. Res. Commun. 221:422-429, 1996) in comparison to the enantiomers. Lipoic acid is therapeutically active in several diseases via antioxidant activity. These findings suggest that racemic lipoic acid can be therapeutically more active than the separate enantiomers. Chirality 9:362-366, 1997. © 1997 Wiley-Liss, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    Toxicokinetics of a single intravenous dose of rac-propranolol versus optically pure propranolol in the rat (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 626-631 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; pharmacokinetics ; interaction ; protein binding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conscious male Wistar SPF Riv:TOX rats were dosed intravenously with 2.5, 5, or 10 mg/kg rac-propranolol·HCl, or with 5 mg/kg of either (-)-(S)- or (+)-(R)-propranolol·HCl. Disposition of (-)-(S)- and (+)-(R)-propranolol after dosing of rac-propranolol was linear in the dose range examined. Total plasma clearance was not changed in animals dosed with the individual enantiomers compared to the animals that were dosed with rac-propranolol. However, for (-)-(S)-propranolol both volume of distribution and elimination half-life decreased, whereas for (+)-(R)-propranolol increases were observed for these characteristics, in animals dosed with the individual enantiomers. Our observations suggest that the (+)-(R)-enantiomer competes with (-)-(S)-propranolol for plasma protein binding sites, resulting in lower plasma protein binding of the (-)-(S)-enantiomer when the racemate is administered. From recent toxicological experiments, it was concluded that rac-propranolol is more toxic than the individual enantiomers in the rat, when dosed iv at the same total mass. It is concluded that the observed potentiation of toxic effects of propranolol enantiomers when administered as a racemate can at least partly be explained by a pharmacokinetic interaction. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070813
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  • 8
    Electronic Resource
    Electronic Resource
    Application of chiralcel OJ in supercritical fluid chromatography for the resolution of different groups of frequently used drug racemates (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 126-132 
    Details
    ISSN: 0899-0042
    Keywords: supercritical fluid chromatography ; profens ; 2-arylpropionic acids ; barbiturates ; benzodiazepines ; tris(4-methylbenzoate) cellulose ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Supercritical fluid chromatography was applied to evaluate the direct chiral discriminative properties of Chiralcel OJ, a tris(4-methylbenzoate) cellulose column towards frequently administered drugs. Two groups of acidic drugs, profen and barbiturate derivatives, and a few basic drugs of the benzodiazepine type were analysed. The effect on enantioselectivity of carbon dioxide when using methanol are acetonitrile as primary modifier was studied. Acetonitrile proved to be a good alternative for methanol, especially for the profen compounds that were not well resolved using methanol. The results were compared to normal phase chromatographic applications on the same column. SFC was not necessarily superior to high-performance liquid chromatography. Chirality 9:126-132, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Structural study on quasi-phosphonium salts containing phosphorus-oxygen, phosphorus-oxygen, phosphorus-nitrogen and phosphorus-sulphur bonds (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 41-46 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal and molecular structues of six quasi-phosphonium salts containing phosphorus-heteroatom heteroatom=oxygen, sulphur or nitrogen0 bonds were determined. Comparison of the molecular parameters obtained with those available for reference structures demonstrated that the ‘double bond’ character for the P+ — Y bond decreases in the order Y = N ≫ O 〉 S.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080109
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  • 10
    Electronic Resource
    Electronic Resource
    Wechselwirkungen in Kristallen. 98. Mitt. Protonierte Hexamethylmelamin-Salze mit verschiedenen Anionen: Monomeres Tetraphenylborat, dimeres Trifluoracetat und polymeres Chlorid-DihydratProfessor Ekkehard Winterfeldt zum 65. Geburtstag gewidmet (1997)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 525-533 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interaction in Crystals. 98. Protonated Hexamethylmelamin Salts with Different Anions: Monomeric Tetraphenylborate, Dimeric Trifluoracetate and Polymeric Chloride-DihydrateHexamethylmelamin (2,4,6-tris(dimethylamino)-1,3,5-triazine), on monoprotonation at one of the triazine nitrogens keeps its close to planar skeleton. Its salts with different anions reflect biochemically interesting hydrogen-bridge networks: Crystallization of the hydrochloride from isopropanol solution containing Li⊕ [B⊖(C6H5)4], yields “naked” molecular cations, packed in herringbone fashion in between the lattice-dominating bulky, phenyl-shielded and non-protonable tetraphenylborate anions. From trifluoroacetic acid, crystals with sandwich-like subunits connected by hydrogen-bridged anions [F3CCOO⊖…HOOCCF3] are obtained. The hydrochloride salt, prepared by adding aqueous HCl to a diethylether solution, crystallizes in stacks of triazinium cation dimers with an intermolecular bridge N⊕-H…Cl⊖…H⊕N in between chloride-bydrate strands (…Cl⊖…HOH…O(H)H…Cl⊖…). Together, the structures of the three different hexamethyl-melaminium salts further illustrate the influence of anions on the crystallization of protonated nitrogen heterocycles and complement that of counter cation cation solvation in molecular anion salts.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19973390195
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