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R Enantiomer (r + enantiomer)
Selected AbstractsEnantioselective reduction of pentoxifylline to lisofylline using whole-cell Lactobacillus kefiri biotransformationBIOTECHNOLOGY JOURNAL, Issue 4 2007bieta P, kala; Dr. Abstract Lisofylline (LSF) is a drug candidate that has been under investigation for acute respiratory distress syndrome, acute lung injury, septic shock and mucositis. As LSF is not commercially available in our country, we produced it for pharmacokinetic studies. In the present work whole-cell reduction of pentoxifylline [1-(5-oxohexyl)-3,5-dimethylxanthine] to LSF [1-(5R-hydroxyhexyl)-3,5-dimethylxanthine] using Lactobacillus kefiri DSM 20587 was investigated. Glucose or 2-propanol was used as a co-substrate to regenerate the NADPH cofactor. The reaction conditions were optimized. The influence of different concentrations of co-substrates on the yield and enantioselectivity of the biotransformation of pentoxifylline into LSF were tested. Maximum yield (100%) of biotransformation was reached in the presence of glucose as a co-substrate. At glucose concentrations of 675 and 900 mM the bioreduction of pentoxifylline proceeded highly enantioselectively (enantiomeric excess for the R enantiomer of 98%). [source] Enantiomers of a nonylphenol isomer: Absolute configurations and estrogenic potenciesCHIRALITY, Issue 2 2009Haifeng Zhang Abstract Enantiomers of 4-(1,1,2-trimethylhexyl)phenol, a chiral isomer of the endocrine disrupting chemical nonylphenol, have been resolved and isolated by preparative chiral HPLC. The absolute configurations of the enantiomers were then determined by an X-ray crystallographic study of the (,)-camphanoyl derivative of the first eluted enantiomer NP35E1. The first enantiomer (NP35E1) and the second enantiomer (NP35E2) eluted were found to have the S and R absolute configurations, respectively. The estrogenic potencies of the S and R enantiomers were tested by the E-screen assay. A slight difference was observed in the relative proliferative effect between the S enantiomer and R enantiomer in the E-screen assay. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] HPLC enantioseparation of ,2 -homoamino acids using crown ether-based chiral stationary phaseJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2009Róbert Berkecz Abstract RP high-performance liquid chromatographic methods were developed for the enantioseparation of eleven unusual ,2 -homoamino acids. The underivatized analytes were separated on a chiral stationary phase containing (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as chiral selector. The effects of organic (alcoholic) and acidic modifiers, the mobile phase composition and temperature on the separation were investigated. The structures of the substituents in the ,-position of the analytes substantially influenced the retention and resolution. The elution sequence was determined in some cases: the S enantiomers eluted before the R enantiomers. [source] Enantiomers of a nonylphenol isomer: Absolute configurations and estrogenic potenciesCHIRALITY, Issue 2 2009Haifeng Zhang Abstract Enantiomers of 4-(1,1,2-trimethylhexyl)phenol, a chiral isomer of the endocrine disrupting chemical nonylphenol, have been resolved and isolated by preparative chiral HPLC. The absolute configurations of the enantiomers were then determined by an X-ray crystallographic study of the (,)-camphanoyl derivative of the first eluted enantiomer NP35E1. The first enantiomer (NP35E1) and the second enantiomer (NP35E2) eluted were found to have the S and R absolute configurations, respectively. The estrogenic potencies of the S and R enantiomers were tested by the E-screen assay. A slight difference was observed in the relative proliferative effect between the S enantiomer and R enantiomer in the E-screen assay. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||