A divergent approach to the preparation of cysteine and serine analogs

Malonate diesters containing a prochiral quaternary carbon have been successfully transformed into analogs of cysteine and serine. The chiral half-esters are obtained in good yield, and enantioselectivity by selective hydrolysis using Pig-Liver Esterase (PLE) as the catalyst. The resulting half-ester intermediates are transformed into alpha2, 2-, beta2, 2-, and beta3, 3-analogs of cysteine and serine. The methodology described here allows for the preparation of both enantiomers of the amino-acid analogs by selective manipulation of the ester and acid functionalities. This divergent strategy allows a common synthetic strategy to be used to prepare a variety of unnatural amino-acid classes from a common intermediate which should prove useful in the design of novel peptide libraries.