SYNTHESES OF GLYCOSYL PHOSPHATES BY PHASE-TRANSFER CATALYSIS

The peracetylated glycosyl bromides of D-glucose (1), D-galactose (2), and D-lactose (5) were treated with dibenzyl phosphate in a catalytic two-phase system using tetrabutylammonium hydrogen sulfate as catalyst. The reactions proceeded by complete inversion at the anomeric centers and afforded a new stereospecific entry into 1,2-trans-beta-D-glycosyl phosphates of peracetylated D-glucose (3), D-galactose (4), and the disaccharide D-lactose (6) in 83, 73, and 83% yields respectively. Interestingly, the glycosyl chloride 7 furnished the oxazoline 9 rather than the expected glycosyl phosphate 8.