A simple procedure for the preparation of enantiopure ethyl α-hydroxyalkyl ketones

Amides derived from pyrrolidine and methyl ( S )-lactate, methyl ( S )-2-hydroxy-3-phenylpropanoate, or methyl ( S )-2-hydroxy-3-methylbutanoate, after O -benzylation and O -silylation have been treated with EtLi or EtMgCl under suitable conditions, to give excellent overall yields of enantiopure ethyl ketones. The chelating ability of α-OBn amides (and even of α-O-TBS amides, which has been demonstrated by NMR to be better than that of N -OMe amides) accounts for the performance of the approach.