SYNTHESIS OF GLYCOSYL PHOSPHATES AND AZIDES

Anomerically enriched diphenyl hexopyranosyl phosphate triesters have been prepared from O-alkyl and -acylated hexopyranoses, using diphenyl chlorophosphate and 4-N,N-dimethylaminopyridine. Glycosyl phosphate triesters of D-gluco-, D-galacto-, D-manno, 2-acetamido-2-deoxy-D-gluco-, L-fuco-, and L-rhamno-pyranosyl derivatives have been obtained by this procedure. At temperatures 0-degrees and above, and under thermodynamic control, diphenyl glycosyl phosphates cis to the pyranosyl C-2 substituent are formed predominantly, whereas at low temperatures and under kinetic control, glycosyl phosphate triesters having 1,2-trans stereochemistry are obtained. The beta-glycosyl phosphate triesters of D-glucose and D-galactose derivatives are unstable and undergo anomerization to the alpha-glycosyl phosphate triesters, in contrast to the stable beta-phosphate derivatives of L-rhamnose and D-mannose. These phosphate triesters have been deprotected to glycosyl phosphate triethylammonium salts, suitable for the preparation of other key biological derivatives, such as nucleotide sugars. In addition, the diphenyl phosphate groups at the anomeric center have been displaced by azide to give the glycosyl azides, key intermediates in the synthesis of glycosyl amino acids.