Photoreaction of methyl and phenyl 4,6-O-benzylidene-2,3-dideoxy-2-C-p-tolylsulfonyl-beta-D-erythro-hex-2-enopyranosides in methanol.

The title compounds were irradiated with a high-pressure mercury lamp in methanol to give 2-C-hydroxymethyl derivatives having the gluco, altro, and allo configurations as well as an S(N)2' product. Equatorial attack of a hydroxymethyl radical slightly predominated over axial attack. During chromatographic separation on a silica gel column, partial migration of the 4,6-O-benzylidene group in the gluco and altro products occurred to yield the 3',4-O-benzylidene derivatives.