Oxidative Cyclization of 2′,3′-O-Isopropylidene-Adenosines into 5′-O,8-Cycloadenosines with Lead Tetraacetate: Remarkable Effect of N6-Substituents on the Oxidation

Abstract Oxidation of 2′,3′-O-isopropylideneadenosines (1) with lead tetraacetate (LTA) in dry benzene resulted in the formation of the corresponding 5′-O,8-cyclo-2′,3′-O-isopropylideneadenosines (2), which has a new methodological implication for the chemical modification of adenosines. The occurrence of the oxidative cyclization was remarkably affected by the nature of N6-substituents: N6-benzoyl substitution prominently accelerated the oxidative cyclization in comparison with none and dimethyl substitutions. In the oxidation of N6,N6-dimethyladenosine (1d), an intriguing oxidative demethylation was observed.