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THE IMMOBILIZATION OF AMINOACYLASE AND THE RESOLUTION OF D,L-PHENYLALANINE

Science China Chemistry 1991年第6期34卷 641-650页

作者：韩际宏姜坪何炳林 Dept.of Biochem. Graduare School of medical SciencesCornell UniversityNew YorkNY 10021USA Institute of Polymer Chemistry Nankai University Tianjin 300071 PRC

A polymer with suitable physical characters and matched functional groups was synthesized,and used as a supporter to immobilize aminoacylase. The results showed that this supporterhad high immobilizing capacity and high selectivity for aminoacylase. Immobilized amino-acylase had high specific activity. In this paper, we determine the physical and chemicalcharacters of aminoacylase for resolution of D,L--phenylalanine, including its optimum tem-perature, pH, ion concentration, activated ion, substrate concentration, thermal stability anddenaturation. The immobilized aminoacylase was used to resolve the D,L-phenylalaninecontinuously. Thc resolved products was separated and purified with ion-exchange resins. L-phenylalanine solution was concentrated by vacuum evaporation and its hydrochloride wasformed. Checking of final product with polarimeter showed high yield and purity.

关键词： aminoacylase immobilization phenylalanine racemate resolution

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Is the required therapeutic effect always achieved by racemic switch of proton-pump inhibitors?

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World Journal of Gastroenterology 2008年第16期14卷 2617-2619页

作者： Quan Zhou Xiao-Feng Yan Wen-Sheng Pan Su Zeng Department of Clinical Pharmacy The 2nd Affiliated Hospital School of Medicine Zhejiang University Hangzhou 310009 Zhejiang Province China Department of Gastroenterology the 2nd Affiliated Hospital School of Medicine Zhejiang University Hangzhou 310009 Zhejiang Province China Department of Pharmaceutical Analysis & Drug Metabolism College of Pharmaceutical Sciences Zhejiang University Hangzhou 310058 Zhejiang Province China

Many of the drugs currently used in medical practice are racemates. The enantiomers of a racemic drug differ in pharmacodynamics and/or pharmacokinetics, thus in some cases it is preferable to develop pure enantiomers by racemic switch. In a recent study by Pai et al, dexrabeprazole [R(+)-rabeprazole] (10 mg) was found to be more effective than rabeprazole (20 mg) in the treatment of gastroesophageal reflux disease. We read with great interest in this study and discussed whether such racemic switch would be applicable to other proton-pump inhibitors (PPIs). A literature review indicates that stereoselective pharmacokinetics, rather than stereoselective pharmacological activity, is the main cause of differences in clinical efficacy between pure enantiomer and racemic PPI. Racemic switches of PPI provide the therapeutic advantages such as reducing metabolic load on the body, simplifying pharmacokinetics, providing benefit to the non-responders to standard dose of racemate, more homogenous response to treatment and better efficacy with equal safety. Further studies in quantitative structure-activity relationships (QSARs) are needed to address the fact that the preferred enantiomer of PPI is not always in the same absolute configuration, i.e., S-form is for omeprazole, pantoprazole and tenatoprazole whereas R-form is for lansoprazole and rabeprazole.

关键词： Proton-pump inhibitors Enantiomer racemate Stereoisomerism Racemic switch Pharmacokinetics Pharmacodynamics Cytochrome P450 Genotype

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Proposed Extension to the Natta Projection Notation System for Enabling an Indication of Relative Stereochemistry and the Stereochemical State

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International Journal of Organic Chemistry 2011年第4期1卷 215-217页

作者： Karel D. Klika 不详

A system of structure depiction, as an extension of the wedge and hashed wedge bonds (Natta projection), and text notation is herein suggested that embodies more explicit information—or reduced over-statement as circumstances warrant—on the stereochemical nature of the system at hand, in particular, for those cases where only the relative stereochemistry of a compound is known.

关键词： Stereochemistry Stereochemical Descriptors Natta Projection racemate Enantiomer

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International Journal of Organic Chemistry 2012年第3期2卷 224-232页

作者： Karel D. Klika Department of Chemistry University of Turku Turku Finland

Deficiencies in the terminology used to describe chiral systems exist for behaviors under various processes and thus a more general, robust terminology is considered. For example, the descriptions for characterizing melting point, solubility, and recrystallization behaviors were adopted well before it was realized that perturbation of the enantiomeric com-position (ec) due to self-disproportionation could be effected by processes other than recrystallization such as sublimation, chromatography over achiral substrates, and even distillation. Thus, an endeavor has been made to address the question of universally describing behaviors under processes that effect, or are dependent on, the ec. The main terms that have been defined with respect to behavior are homomate (analogous to a conglomerate), heteromate, bimate (analogous to a racemic compound), and unimate (analogous to a solid solution) and they apply to melting point, solubility, recrystallization, sublimation, distillation, and chromatographic processes. Additionally, suggestions for improving the terminology for describing the states of chiral systems are also considered and the defined terms are: holemate (hol, ec = 100%), scalemate (scl, 50% ec eqm, ec = 50%).

关键词： Stereochemistry Terminology Chirality State-Dependent Behavior Conglomerate racemate

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