THE ALLYL GROUP FOR PROTECTION IN CARBOHYDRATE-CHEMISTRY .31. CONVERSION OF ALLYL 2,6-DI-O-BENZYL-ALPHA-D-GALACTOPYRANOSIDE INTO ALLYL 2,6-DI-O-BENZYL-ALPHA-D-GLUCOPYRANOSIDE AND 2,6-DI-O-BENZYL-D-GLUCOPYRANOSE

Allyl 2,6-di-O-benzyl-alpha-D-galactopyranoside was converted by tin-m ediated alkylation into the 3-O-p-methoxybenzyl ether which gave the 4 -O-mesyl derivative. Sodium benzoate in refluxing N,N-dimethylformamid e converted the last compound into allyl benzyl-3-O-p-methoxybenzyl-al pha-D-glucopyranoside in high yield. This was saponified and the produ ct was treated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone tb give the required allyl 2,6-di- O-benzyl-alpha-D-glucopyranoside whose stru cture was confirmed by conversion into the known 2,3,4,6-tetra- O-benz yl-D-glucopyranose. Removal of the allyl group from allyl 2.6-di-O-ben zyl-alpha-D-glucopyranoside by a standard procedure gave 2,6-di-O-benz yl-D-glucopyranose. Both of the title compounds are required as interm ediates for the synthesis of analogues of the 'adenoptiostins'.