Stereoselective photochemical transformations of hexopyranosyl imides to highly functionalised heterocycles

Reaction of O-protected glycosylamines with succinic anhydride and subseque nt acylation afford both anomers of gluco- and manno-configurated N-glycosy lsuccinimides. Irradiation with UV light of 254 nm wavelength leads to abst raction of H-2 and H-5, respectively, by the excited carbonyl function. The stereoselective recombination of the resulting 1,4- and 1,5-diradicals giv es the annelated azacyclobutanol and azacyclopentanol derivatives, respecti vely. Owing to the strained four-membered rings, the azacyclobutanol deriva tives fragment by an aza-analogous retroaldol addition to give the hexopyra nosyl-annelated azepanedione systems.