Synthesis and reactivity of (RS)-6-chloro-7- or 9-(1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl)-7H- or 9H-purines bearing a nitrobenzenesulfonyl group on the nitrogen atom

The O,O-acetalic compounds (RS)-3-methoxy-1-[(2)- or (4)-nitrobenzenesulfonyl)]-1,2,3,5-tetrahydro-4,1-benzoxazepine have been studied in the Lewis acid-mediated condensation with 6-chloropurine. 6-Chloropurine leads to the N-7″ aminalic bond in the cyclic products and mainly to the N-9″ aminalic bond in the acyclic ones. Substitution of the chlorine atom at the 6″ position of the purine moiety is more feasible when the ring is alkylated at N-7″ than at N-9″. Exchange with a hydroxyl group is performed with water traces in deuterated dimethylsulfoxide at room temperature in a solvent-mediated process. The exchange with strong nucleophiles (e.g., thiophenol) does not need further activation.