Anchimeric assistance of a 5'-O-carbonyl function for inversion of configuration at the 3'-carbon atom of 2'-deoxyadenosine. Synthesis of 3'-azido-2',3'-dideoxyadenosine and 3'-azido-2',3'-dideoxyinosine

3′-Azido-2′,3′-dideoxyadenosine was synthesized in two steps from N6,5′-O-dibenzoyl-2′-deoxyadenosine in 65% yield. The configuration at the 3′ position was inverted by reaction of N6,5′-O-dibenzoyl-2′-deoxyadenosine with triflic anhydride-pyridine and water. The product distribution under different reaction conditions is described together with a benzoyl migration reaction. The azido group was introduced by a nucleophilic substitution reaction with lithium azide on the 3′-O-triflate of N-benzoyl-9-(5-O-benzoyl-2-deoxy-β-D-threo-pentofuranosyl)adenine. Enzymatic deamination of 3′-azido-2′,3′-dideoxyadenosine gave 3′-azido-2′,3'-dideoxyinosine.