CHAPTER 5: Question 10

Simple Answers

In both cases, the enzyme selectively hydrolyses the ester (or thioester) of one of the two enantiomers of the starting material. However, under the reaction conditions the starting materials (but not the products) undergo rapid racemization. Thus the enantiomer of the starting material that is not a substrate for the enzyme is constantly being equilibrated with the enantiomer which is a substrate. In both cases, this results in the formation of a >50% chemical yield of a product with hight enantiomeric purity. The reason why the ee of the products is not 100% is probably due to competing non-enymatic hydrolysis of the ester / thioester, especially for compound A why is hydrolysed under basic conditions.

This question is taken from: H. Stecher, and K. Faber; Synthesis, 1997, 1-16.

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