CHEMICAL INTERACTION BETWEEN THE AGLYCON AND THE ALLYL GROUP OF 6-O-ALLYLHEXOPYRANOSIDE DERIVATIVES

The free radical derived from 1-O-allyl-2,6-anhydro-3,4,7,9-tetradeoxy-8-O-phenoxythiocarbonyl-D-arabino-non-3-en-5-ulose ethylene acetal (4), in the presence of tributyltin hydride, gave the direct product of reduction (13) and also products (15), derived following tandem cyclisation, which are structurally related to the trichothecenes. In addition, evidence was found which indicated that the initial radical reacted intramolecularly with the allyl group. To establish whether radicals in aglycons can react with the alkene groups of 6-allyl ethers of hexopyranosides, 2-bromoethyl 2,3,4-tri-O-acetyl-6-O-allyl-beta-D-glucopyranoside (19) was treated with tributyltin hydride and a radical initiator. The 11-membered ring product 5'-hydroxypentyl 2,3,4-tri-O-acetyl-6,5'-anhydro-beta-D-glucopyranoside (21) was isolated (15%, unoptimised) as well as the product of direct reductive debromination.