Search results for "Stereoselectivity"
showing 10 items of 325 documents
Stereochemistry of terpene derivatives. Part 3: Hydrolytic kinetic resolution as a convenient approach to chiral aminohydroxyiminocaranes with local …
2002
Abstract We have developed a stereoselective hydrolytic kinetic resolution process for diastereoisomeric mixtures of epoxyiminocarene intermediates in the presence of ( R , R )-(−)-(salen)Co(III)OAc catalyst, this was applied as the first step in the synthesis of novel chiral aminohydroxyiminocarane derivatives with local anaesthetic activity. The absolute configuration of the product was confirmed by X-ray crystallography.
Use of Saccharomyces cerevisiae as a whole cell system for aldol condensation in organic medium: Study of the factors affecting the biotransformation
2011
Abstract Saccharomyces cerevisiae has been employed as a whole cell catalyst for a number of asymmetric transformations. This work explores the ability of this microorganism to carry out the asymmetric aldol condensation between 4-nitrobenzaldehyde and acetone. For this purpose, lyophilized cells of the FY86 laboratory strain from stationary phase cultures were employed. This reaction shows stereoselectivity, and its progress is affected by the water concentration in the medium, temperature and the growth stage of the yeast culture. Cell lysis experiments indicate that activity responsible for this biotransformation is located in the soluble fraction.
Metabolic Activation of the (+)-S,S- and (−)-R,R-Enantiomers of trans-11,12-Dihydroxy-11,12-dihydrodibenzo[a,l]pyrene: Stereoselectivity, DNA Adduct…
1997
Polycyclic aromatic hydrocarbons require metabolic activation in order to exert their biological activity initiated by DNA binding. The metabolic pathway leading to bay or fjord region dihydrodiol epoxides as ultimate mutagenic and/or carcinogenic metabolites is thought to play a dominant role. For dibenzo[a,l]pyrene, considered as the most potent carcinogenic polycyclic aromatic hydrocarbon, the formation of the fjord region syn- and/or anti-11,12-dihydrodiol 13,-14-epoxide (DB[a,l]PDE) diastereomers has been found to be the principal metabolic activation pathway in cell cultures leading to DNA adducts. In order to further elucidate the stereoselectivity involved in this activation pathway…
Covalent DNA adducts formed in mouse epidermis by benzo(g)chrysene
1996
The metabolic activation in mouse skin of benzo[g]chrysene (B[g]C), a moderately carcinogenic polycyclic aromatic hydrocarbon (PAH) present in coal tar, was investigated. Male Parkes mice were treated topically with 0.5 micromol B[g]C and DNA was isolated from the treated areas of skin at various times after treatment and analysed by 32P-post-labelling. Seven major adduct spots were detected, at a maximum level of 6.55 fmol adducts/microg DNA. Mouse skin treated with the PAH benzo[c]phenanthrene (B[c]Ph) gave a total of 0.24 fmol adducts/microg DNA. B[g]C-DNA adducts persisted in skin for at least 3 weeks. Treatment of mice with 0.5 micromol of the optically pure putative proximate carcinog…
Synthesis of fjord region tetraols and their use in hepatic biotransformation studies of dihydrodiols of benzo[c]chrysene, benzo[g]chrysene and diben…
1998
Metabolic activation of the racemic benzo[c]chrysene-trans-9,10-, benzo[g]chrysene-trans-11,12- and dibenzo[a,l]pyrene-trans-11,12-dihydrodiols to fjord region syn- and anti-dihydrodiol epoxides by microsomes of Aroclor 1254-treated Sprague-Dawley rats has been examined. Since the fjord region dihydrodiol epoxides were hydrolytically unstable under the experimental conditions, their enzymatic formation was determined by analyzing the tetraols as their products of acidic hydrolysis upon addition of perchloric acid. The various stereoisomeric tetraols formed were separated by HPLC and identified by co-chromatography with authentic tetraols, which had been prepared by acidic hydrolysis of synt…
Regio- and stereo-selectivity in the induction of peroxisome proliferation by substituted hexanoic acids
1993
Summary Quantitative structure-activity relationship is an effective tool in order to predict drug potency. A similar approach is actually developed for peroxisome proliferation induced by substituted carboxylic acids issued from plasticizer metabolism in rats. The study is focused on acids found in rat urine after adipic diester dosings. Size, location of the substituted group and length of the chain have been studied. 3-D structure has also been taken in account for 2-ethyl hexanoic acids. The results obtained so far demonstrate that peroxisome proliferation potencies of the considered acids are modified according structure changes. At this time location of the group along the chain appea…
Blood-brain barrier penetration of the enantiomers of venlafaxine and its metabolites in mice lacking P-glycoprotein
2010
According to in vitro studies the enantiomers of venlafaxine display different degrees of serotonin and noradrenaline reuptake inhibition. Therefore, clarification of the enantiomeric drug distribution between serum and brain is highly warranted. To elucidate if P-glycoprotein (P-gp) in a stereoselective manner transports venlafaxine and its metabolites out of the brain we used abcb1ab double-knockout mice that do not express P-gp. A single dose of racemic venlafaxine (10 mg/kg bw) was intraperitoneally injected to knockout (-/-) and wildtype (+/+) mice. Serum and brain samples were collected 1, 3, 6 and 9 h following drug administration for analysis by LC/MS/MS. One to six hours post-dose,…
The hMTH1 paradox: antioxidants recommended in cancer?
2014
Summary Activated Ras GTPase signalling is a critical driver of oncogenic transformation and malignant disease. Cellular models of RAS-dependent cancers have been used to identify experimental small-molecules, such as SCH51344, but their molecular mechanism of action remains generally enigmatic. Here, using a chemical proteomic approach we identify the target of SCH51344 as the human mutT homologue MTH1, a nucleotide pool sanitising enzyme. Loss-of-function of MTH1 impaired growth of KRAS tumour cells whereas MTH1 overexpression mitigated sensitivity toward SCH51344. Searching for more drug-like inhibitors, we identified the kinase inhibitor crizotinib as a nanomolar suppressor of MTH1 acti…
Enantioselective syntheses of dopaminergic (R)- and (S)-benzyltetrahydroisoquinolines.
2001
Optically pure (1S,R)- and (1R,S)-benzyltetrahydroisoquinolines (BTHIQs), 12a,b as the major diastereomers, were prepared by stereoselective reduction of the isoquinolinium salt possessing (R)- and (S)-phenylglycinol as the chiral auxiliary, respectively. The absolute configurations of (1S,R)-13a hydrochloride (O-debenzoylated derivative from 12a) and (1R,S)-12b diastereomers were unambiguously determined by single-crystal X-ray analysis. Reductive removal of the chiral auxiliary group, subsequent N-propylation, and cleavage of the methylenedioxy group furnished the optically active catecholamines (1S)-16a and (1R)-16b in good overall yield. We have separately prepared for the first time pa…
Stereoselective drug distribution and anticoagulant potency of the enantiomers of phenprocoumon in rats
1977
Abstract The elimination, distribution and anticoagulant activity of S(—)-, R(+)-, and R,S(±)-phenprocoumon were determined in male Wistar-Lewis rats after intravenous injection of a single dose of 0·6 mg kg−1. From the plasma concentrations which elicited the same anticoagulant effect, S(—)-phenprocoumon was 4 to 5 times more potent than R(+)-phenprocoumon. The potency of the racemate was between those of the enantiomers. The mean biologic half-life of the S(—)-enantiomer was shorter (12·5 h) than that of R(+)-phenprocoumon (17·8 h). No differences were observed in the apparent volume of distribution. However, the mean liver: plasma concentration ratio was higher for the S(—)-(6·9) than fo…