HIGHLY DIASTEREOSELECTIVE BORON-MEDIATED ANTI-ALDOL REACTIONS OF 4-SILYL SUBSTITUTED 2,2-DIMETHYL-1,3-DIOXAN-5-ONE - DIASTEREOSELECTIVE ANDENANTIOSELECTIVE SYNTHESIS OF PROTECTED OXOPOLYOLS

The boron enolate of 4-silylated 2,2-dimethyl-1,3-dioxan-5-one (S)-3 r eacts with representative aldehydes in a highly anti diastereoselectiv e 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 t o protected oxopolyols (S,S)-5 in good yields (64-79%) with excellent diastereomeric and enantiomeric excesses (de,ee = 96-98%). The absolut e configuration was determined by X-ray structure analysis of (S,S)-5c .