SYNTHESIS OF HETARYL GLYCOSIDES AND THEIR GLYCOSYL DONOR PROPERTIES

Anomeric O-hetarylation of tetra-O-benzyl- and tetra-O-acetylglucose ( 1a, b) can be directly performed with electron-deficient heteroaromati c/heterocyclic systems 2-14, which contain imide halide moieties. The reactions were carried out in the presence of a base and led, through an exchange of the halide by the glucopyranosyloxy moiety, to the prod ucts 2a-14a, 7b-14b. Predominantly or exclusively beta-products were o btained. Systems bearing more than one imide halide moiety, such as cy anuric fluoride (15) or 5-chloro-2,4,6-trifluoropyrimidine (16), can b e employed for successive anomeric O-hetarylations. Investigation of t he glycosyl donor properties of O-glucosyl heteroaromatic imidates wit h 6-O- and 4-O-unprotected glucose derivatives 18 and 19 as accepters and comparison of the results obtained with data for the corresponding beta-trichloroacetimidates 17a beta and 17b beta, reveals that 2,3,5, 6-tetrafluoropyridin-4-yl glucopyranosides 14a beta and 14b beta exhib it similar properties. For specific tasks, for instance cr-glucopyrano side formation, 14a beta may even be advantageous.