Aldol reactions with erythrulose derivatives:: Stereoselective synthesis of differentially protected syn-α,β-dihydroxy esters

Boron enolates of 1-O-silylated erythrulose 3,4-acetonides prepared with Brown's chloro-dicyclohexylborane/tertiary amine system have been shown to react with achiral aldehydes in a highly stereoselective way to yield a 1,2-syn/1,3-syn stereoisomer. Through oxidative cleavage of the aldol adducts with periodic acid hydrate, enantiopure syn-alpha,beta-dihydroxy esters with either hydroxyl group differently protected have been prepared. These erythrulose derivatives therefore behave as a chiral hydroxy acetate (glycolate) enolate equivalent. (C) 2000 Elsevier Science Ltd. All rights reserved.