Stereoselective α-alkylation of methyl 6-deoxy-3,4-di-O-(tert-butyldimethylsilyl)-2-O-(2-methyl-3-oxobutanoyl)-α-d-glucopyranoside

Allylation and benzylation at the α-carbon of α-methylated acetoacetyl (2-methyl-3-oxobutanoyl) group incorporated into the 2-OH of methyl 6-deoxy-3,4-O-(tert-butyldimethylsilyl)-α-d-glucopyranoside provided the respective α,α-differentially alkylated acetoacetyl derivatives, both with high diastereoselectivity. Thus-obtained doubly alkylated products possess an all-carbon quaternary stereogenic center with an absolute stereochemistry opposite to that introduced by using the 4-O-acetoacetyl regioisomer as the alkylation substrate.