Acyclonucleosides of indazole and their rearrangements

2-[(2-Acetoxyethoxy)methyl]indazole (3), a kinetic product formed in the reaction of indazole (1) with 2-acetoxyethyl acetoxymethyl ether (2), undergoes an irreversible, acid-catalyzed isometrization of the 2Ž 1 transglycosylation type to the respective 1-regioisomer (4). In contrast to the purine acyclonucleosides series, however, product 4 undergoes a further rearrangement to the dimmer 5. On the basis of products distribution and kinetics of their formation, a mechanism of these conversions has been proposed and compared to the facile anomerization reactions of indazole ribofuranosides.