The asymmetricsynthesis of novel cyclohexene nucleosideanalogues 12 and 15 is described. An enantiospecific Diels–Alder reaction between (E,E)-diene 2 and (+)-5-(d-mentyloxy)-2(5H)-furanone 3 provided the cycloadduct isomer 4. Three additional steps yielded amine 8 allowing the constructions of the thymine and adenine moieties to afford intermediates 11 and 14, respectively. Amination or cyclization