Naphthyl 3,4,6-tri-O-methyl-beta-D-glucopyranoside as a chiral auxiliary in an asymmetric 1,4-addition reaction

Naphthyl 3,4,6-tri-O-methyl-beta-D-glucopyranoside, easily synthesized from tri-O-acetyl-D-glucal, has been applied as a chiral auxiliary in an asymmetric Michael addition to the 2-O-crotonate. A very high facial diastereoselection (>95%) was obtained. No diastereoselection was observed when 1,3,4,6-tetra-O-methyl-beta-D-glucopyranoside was used as the chiral auxiliary. A stereochemical model, taking into account steric shielding and pi-stacking effects, is proposed on the basis of the observed results. (C) 1997 Elsevier Science Ltd.