Synthesis of Chiral Compounds

Use ofMethanesulfonyl Chloride (MSC) in the Synthesis of Chiral Compounds, Technical Bulletin A-70-11, Elf Atochem North America, Philadelphia, Pa., 1992. 

M. R. Kula, U. Kragl, Dehydrogenases in the synthesis of chiral compounds" in R. Patel, Stereoselective Biocatalysis, Marcel Dekker, 2000, 839. 

Hummel, W. (1997) New alcohol dehydrogenases for the synthesis of chiral compounds. Advances in Biochemical Engineering/Biotechnology, 58, 145-184. 

As already mentioned, the most important industrial application of homogeneous hydrogenation catalysts is for the enantioselective synthesis of chiral compounds. Today, not only pharmaceuticals and vitamins [3], agrochemicals [4], flavors and fragrances [5] but also functional materials [6, 7] are increasingly produced as enantiomerically pure compounds. The reason for this development is the often superior performance of the pure enantiomers and/or that regulations demand the evaluation of both enantiomers of a biologically active compound before its approval. This trend has made the economical enantioselective synthesis of chiral performance chemicals a very important topic. 

Enzyme reductions of carbonyl groups have important applications in the synthesis of chiral compounds (as described in Chapter 10). Dehydrogenases are enzymes that catalyse, for example, the reduction of carbonyl groups they require co-factors as their co-substrates. Dehydrogenase-catalysed transformations on a practical scale can be performed with purified enzymes or with whole cells, which avoid the use of added expensive co-factors. Bakers yeast is the whole cell system most often used for the reduction of aldehydes and ketones. Biocatalytic activity can also be used to reduce carbon carbon double bonds. Since the enzymes for this reduction are not commercially available, the majority of these experiments were performed with bakers yeast1 41. 

In the last two decades optically active sulfur compounds have found wide application in asymmetric synthesis. This is mainly because organic sulfur compounds are quite readily available in optically active form. Moreover, the chiral sulfur groupings that induce optical activity can be removed from the molecule easily, under fairly mild conditions, thus presenting an additional advantage in the asymmetric synthesis of chiral compounds. This section deals with reactions in which asymmetric induction in transfer of chirality from sulfur to other centers was observed. This subject has been treated only in a cursory manner in recent reviews on asymmetric synthesis (290-292). 

Example 1 Synthesis of Chiral Compounds Using Enzymes in Solid/Cas Reactors... 

Only a little research on the separation and synthesis of chiral compounds has been published so far. Because enzymes have extremely high selectivity, and owing to the great importance of enantioselective synthesis or enantiomeric resolution in the pharmaceutical industry, the most intense research in this area can be expected, along with minimizing the use of substances and maximizing their effect. 

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