Highly Diastereoselective Boron-Mediated anti-Aldol Reactions of 4-Silyl Substituted 2,2-Dimethyl-1,3-dioxan-5-one. Diastereo- and Enantioselective Synthesis of Protected Oxopolyols

Abstract

The boron enolate of 4-silylated 2,2-dimethyl-1,3-dioxan-5-one (S)-3 reacts with representative aldehydes in a highly anti diastereoselective aldol reaction to give the corresponding adducts (S,S,S)-4 in 78-93% yield with diastereoisomeric excesses of de = 96-98%. The removal of the silyl group via the triethylamine-trihydrofluoride complex leads to protected oxopolyols (S,S)-5 in good yields (64-79%) with excellent diastereomeric and enantiomeric excesses (de,ee = 96-98%). The absolute configuration was determined by X-ray structure analysis of (S,S)-5c.