Enantiopure α-silyl-substituted α-hydroxyacetic acids using O-H insertion methodology and boron-based asymmetric reductions

Two routes to optically active alpha-silyl-substituted alpha-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-Boranee(R) afford the corresponding alpha-hydroxy esters with up to 91% ee.