Enantiopure α-Silyl-Substituted α-Hydroxyacetic Acids Using O-H Insertion Methodology and Boron-Based Asymmetric Reductions

Two routes to optically active α-silyl-substituted α-hydroxyacetic acids are described. As a key step, the first utilizes O-H insertion reactions of (R)-and (S)-phenylethanol into benzyl 2-silyl-2-diazoacetates in the presence of [Rh 2 (OAc) 4 ]. Alternatively, asymmetric reductions of benzyl 2-silyl-2-oxoacetates using (R)-Alpine-Borane® afford the corresponding α-hydroxy esters with up to 91% ee.