The Allyl Group for Protection in Carbohydrate Chemistry. XXXI. Conversion of Allyl 2,6-Di-O-benzyl-α-D-galactopyranoside Into Allyl 2,6-Di-O-benzyl-α-D-glucopyranoside and 2,6-Di-O-benzyl-D-glucopyranose

Abstract

Allyl 2,6-di-O-benzyl-α-D-galactopyranoside was converted by tin-mediated alkylation into the 3-O-p-methoxybenzyl ether which gave the 4-O-mesyl derivative. Sodium benzoate in refluxing N,N-dimethylformamide converted the last compound into allyl 4-O-benzoyl-2,6-di-O-benzyl-3-O-p-methoxybenzyl-α-D-glucopyranoside in high yield. This was saponified and the product was treated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to give the required allyl 2,6-di-O-benzyl-α-D-glucopyranoside whose structure was confirmed by conversion into the known 2,3,4,6-tetra-O-benzyl-D-glucopyranose. Removal of the allyl group from allyl 2,6-di-O-benzyl-α-D-glucopyranoside by a standard procedure gave 2,6-di-O-benzyl-D-glucopyranose. Both of the title compounds are required as intermediates for the synthesis of analogues of the 'adenophostins'.