OXIDATION OF GLYCALS WITH HYDROGEN-PEROXIDE

Tri-O-acetyl-D-glucal (8) treated with a mixture of hydrogen peroxide- molybdenum trioxide undergoes a Ferrier rearrangement to form 2,3-unsa turated anomeric hydroperoxides 14 and 15.Tri-O-acetyl-D-galactal (10) and tri-O-benzyl-D-glucal (9), under the same conditions, afford the hydroperoxides in a low yield, whereas tri-O-benzyl-D-galactal (11) do es not produce any unsaturated hydroperoxide. 2,3-Unsaturated anomeric hydroperoxides of alpha- and beta-D-eryihro- and alpha-D-threo-19, -2 0, and -24, respectively, were used for the enantioselective epoxidati on of prochiral allylic alcohols 25-27 and oxidation of sulfides 28 an d 29 to give stereoselectivities of up to 50% enantiomeric excess.