Chirality/Chiral background

Catalytic asymmetric Diels-Alder reactions are presented by Hayashi, who takes as the starting point the synthetically useful breakthrough in 1979 by Koga et al. The various chiral Lewis acids which can catalyze the reaction of different dieno-philes are presented. Closely related to the Diels-Alder reaction is the [3-1-2] carbo-cyclic cycloaddition of palladium trimethylenemethane with alkenes, discovered by Trost and Chan. In the second chapter Chan provides some brief background information about this class of cycloaddition reaction, but concentrates primarily on recent advances. The part of the book dealing with carbo-cycloaddition reactions is... 

Library of Cyclic Oligopeptides as Additives to Background Electrolyte for Chiral Capillary Electrophoresis... 

Enantioresolution in capillary electrophoresis (CE) is typically achieved with the help of chiral additives dissolved in the background electrolyte. A number of low as well as high molecular weight compounds such as proteins, antibiotics, crown ethers, and cyclodextrins have already been tested and optimized. Since the mechanism of retention and resolution remains ambiguous, the selection of an additive best suited for the specific separation relies on the one-at-a-time testing of each individual compound, a tedious process at best. Obviously, the use of a mixed library of chiral additives combined with an efficient deconvolution strategy has the potential to accelerate this selection. 

In the following sections we will first in Section 2 briefly discuss the necessary background to understand optical activity effects in linear and nonlinear optics and to illustrate the similarities and differences between both types. In Section 3 we present a more thorough analysis of nonlinear optical effects in second-harmonic generation, both from a theoretical and an experimental point of view. Section 4 deals with experimental examples that illustrate the usefulness of nonlinear optical activity in the study of chiral thin films and surfaces. Finally, in Section 5 we give an overview of the role of chirality in the field of second-order nonlinear optics and show that chiral molecules can be useful for applications in this field. 

Fig. 7. Separation of R- and S-propranolol using MIP particles as chiral additive in the background electrolyte, MIP prepared using S-propranolol as template. Reprinted with permission from Walshe M, Garcia E, Howarth J, Smyth MR, Kelly MT (1997) Anal Commun 34 119. Copyright 1997 The Royal Society of Chemistry...

The use of CLEA preparations of commercially available HNLs allowed for the enantiocomplementary production of cyanohydrins from a pyridinecarboxaldehyde at a much higher chiral purity than had previously been demonstrated with any chemical catalyst. The key to the success of this process was the use of the CLEA -immobilized biocatalysts that allowed reaction conditions to be chosen to minimize the negative effects of the nonspecific background reaction. 

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