Highly Stereoselective α-Alkylations, 1,4-Additions, and One-pot 1,4-Addition/α-Methylations Achieved on 4-O-Acyl and 4-O-Crotonyl Derivatives of Methyl 6-Deoxy-2,3-di-O-(t-butyldimethylsilyl)-α-D-glucopyranoside

Abstract

Benzylation or methylation of the enolate generated from 4-O-propionyl or 4-O-3-phenyl-propionyl derivatives of methyl 6-deoxy-2,3-di-O-(t-butyldimethylsilyl)-α-D-glucopyranoside provided the respective C-alkylated product stereoselectively. The 1,4-additions of a variety of carbon nucleophiles to the corresponding 4-O-crotonyl derivative provided adducts with high and complementary diastereoselection. The one-pot 1,4-additions of a phenyl nucleophile to the 4-O-crotonyl ester followed by the addition of methyl iodide provided vicinally substituted products with high diastereo- and enantioselectivity, from which diastereomeric α-methyl-β-phenylbutanols were obtained in enantioenriched form after reductive removal of the carbohydrate template.