Cyclopropanation of nitroso Diels–Alder cycloadducts and application to the synthesis of a 2′,3′-methano carbocyclic nucleoside

Treatment of nitroso Diels–Alder cycloadducts 1 with diazomethane in the presence of palladium acetate gives synthetically useful exo-6-oxa-7-azatricyclo[3.2.1.02,4]octane derivatives 7 in good to excellent yield. Using this methodology, a conformationally restricted 2′,3′-methano carbocyclic nucleoside was efficiently synthesized from nitroso cycloadduct 1a in seven steps.