AN ELECTROPHILE-MEDIATED CYCLIZATION ON THE 1,6-ANHYDRO-D-GLUCOPYRANOSE FRAMEWORK

Iodocyclization of O-tributylstannyl-D-glucal with iodine in acetonitrile gave 1,6-anhydro-2-deoxy-2-iodo-beta-D-glucopyranose (1) in high yield. The 3,4-di-O-acetyl derivative of 1 could be converted into the corresponding 2-deoxy compound and into the 2-C-allyl-2-deoxy branched sugar (5) by treatment with tributylstannane and allyltributylstannane, respectively. Controlled alkaline hydrolysis of 5 gave the 4-monoacetyl derivative. Complete hydrolysis of 5 gave the 3,4-diol, which underwent a 5-exo cyclization by treatment with N-bromosuccinimide. H-1 NMR spectroscopy and X-ray analysis showed that the cyclized product has the B3,O conformation in its pyranose ring, which is trans-fused to the newly formed tetrahydrofuran ring.