ADDITION OF HALOGENOAZIDES TO GLYCALS

Article abstract of DOI:10.1016/S0008-6215(00)87138-4

Addition of chloroazide to 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-lyxo- (1) and -D-arabino-hex-1-enitol (2) under u.v. irradiation proceeds regio- and stereo-selectively yielding mainly O-acetyl derivatives of 2-azido-2-deoxy-D-galactopyranose and -D-glucopyranose, respectively. 3,4,6-Tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranosyl azide and 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-D-talopyranose (from 1), and 1,3,4,6-tetra-O-acetyl-2-chloro-2-deoxy-α-D-glucopyranosyl azide and 1,3,4,6-tetra-O-acetyl-2-azido-2-deoxy-α-D-mannopyranose (from 2) are byproducts. 1,5-Anhydro-3,4,6-tri-O-benzyl-2-deoxy-D-lyxo- and -D-arabino-hex-1-enitol reacted more rapidly with chloroazide, to give, under irradiation, derivatives of 2-azido-2-deoxy-D-galactose and -D-glucose, respectively.However, reaction in the dark gave mainly O-benzyl derivatives of 2-chloro-2-deoxy-α-D-galacto- and -α-D-glucopyranosyl azide.The difference between the products obtained may depend on the existence of two parallel processes, one radical (under irradiation), and the other ionic (reaction in the dark).