Synthesis of allylsilane-containing amino acids via the Claisen rearrangement

The Claisen rearrangement of N-BOC-glycinate eaters la-ld led to the format ion of alpha -allylsilane-functionalized amino acids 2-3 in good yield (up to 80%). The diastereoselectivity of the reaction varied from 2:1 to 29:1 ( syn:anti) for la depending on reaction conditions. In the case of the Irela nd-Claisen variant, the relationship between size of the alkyl groups on th e enolate trap (Me2R'SiCl, R = Me, t-Bu, Ph) and diastereoselectivity was i nvestigated, showing that chlorotrimethylsilane gave the best results. The size of the alkyl groups on the allylsilane do not exert a significant effe ct on the diastereoselectivity or yield (Me2RSi, R = Me, t-Bu, Ph, i-Pr). ( C) 2000 Published by Elsevier Science Ltd.