Stereoisomerism enantiomeric resolution

It is well known that a chiral environment is essential for the enantiomeric resolution of the racemates. In CE, this situation is provided by the chiral compounds used in the BGE and is known as the chiral selector or chiral BGE additive. Basically, the chiral recognition mechanisms in CE are similar to those in chromatography using a chiral mobile-phase additive mode, except that the resolution occurred through different migration velocities of the dia-stereoisomeric complexes in CE. The chiral resolution occurred through diastereomeric complex formation between the enantiomers of the pollutants and the chiral selector. The formation of the diastereomeric complexes depends on the type and the nature of the chiral selectors used and the nature of the pollutants. 

Since both enantiomers of the substrate are reacting with virtually the same rate, a kinetic resolution is not possible. Rather, any stereoisomeric adduct can be prepared deliberately by starting either from racemic or enantiomerically pure enone and by conducting the reaction with or without epimerization at C6. For example, treatment of rac-281 under the previous conditions, but with basic epimerization in the presence of sodium methanolate furnished the diastereo- and enantiomerically pure /raTW-disubstituted ketone 282, whereas the same sequence with enantiomerically pure enone (i )-281 as the substrate, but without epimerization, afforded the m-disubstituted ketone 283. The enantiomers of 282 and 283 are available by using the enantiomeric ligand with rac-281 or ( -281 as the substrate under the appropriate reaction conditions.237... 

In light of these developments, we felt that it was necessary to review the content of the first edition and to update or supplement the information presented in this work. The new topics examined in this edition include (1) enzymatic synthesis and resolution of enantiomerically pure compounds (Chapter 8) (2) toxicological consequences and implications of stereoselective biotransformations (Chapter 9) (3) stereoselective transport across epithelia (Chapter 10) and (4) assessment of bioavailability and bioequivalence of stereoisomeric drugs (Chapter 11). The chapter on stereoselective protein binding (Chapter 12) has been completely revmtten and new contributions are presented on the regulatory, industrial, and clinical aspects of stereoisomeric drugs (Chapters 13-16). In addition, the chapters... 

It has been demonstrated in previous sections of this chapter that some substrates (e.g., furfuryl alcohols, vinylene carbonate telomers, etc.) are capable of being transformed, in a limited number of synthetic steps, into the full variety of stereoisomeric sugars. These syntheses are fairly general. In this section, carbohydrate preparations are described which start from some peculiar substrates and by exploitation of specific reactions lead to a single monosaccharide or, at most, to a limited number. Natural products have often been used for the purpose. Their structural features usually predetermine the type of sugar that can be obtained. These substrates, being optically active, afford eventually enantiomeric products. The usually troublesome resolution of racemic intermediates of final... 

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