BENZYL 7-O-ALLYL-2,3-O-ISOPROPYLIDENE-4-O-P-METHOXYBENZYL-L-GLYCERO-ALPHA-D-MANNO-HEPTOPYRANOSIDE, A VERSATILE LD-MANHEPP DERIVATIVE

Benzyl 2,3-O-isopropylidene-4-O-p-methoxybenzyl-alpha-D-mannopyranoside was oxidized according to Swern, and the aldehyde obtained was treated with allyloxymethylmagnesium chloride to yield the title heptose derivative (7) as the main product. This compound had the hydroxyl group at C-6 free. Benzylation yielded the fully protected derivative 9. O-Deallylation furnished a heptose derivative (10) having the C-7 hydroxyl group free. Similarly, removal of the p-methoxybenzyl group from 9 led to a derivative (11) with the C-4 hydroxyl group free. Acid hydrolysis of 9 under controlled conditions led to 2,3-diol (12). This compound was benzylated under two-phase conditions to yield the 2-O-benzylated product (13) having a free OH group at C-3. Benzylation of the stannylene derivative obtained from the 2,3-diol and dibutyltin oxide gave the 3-O-benzyl derivative (14) with HO-2 free. The yields of all steps are good to very good.