ACID-PROMOTED REARRANGEMENTS OF N-SUBSTITUTED 8-OXA-3-AZATRICYCLO[3.2.1.0/2,4]OCTANE-6,7-DICARBOXYLATES - REMOTE SUBSTITUENT EFFECTS ON THE REGIOSELECTIVITY OF THE N-ACYLAZIRIDINE/DIHYDROOXAZONE REARRANGEMENT

Preparations of dimethyl (1RS,2SR,4RS,5SR,6SR,7RS)‐ and dimethyl (1 RS,2SR,4RS,5SR,6RS,7SR)‐8‐oxa‐3‐azatricyclo[3;2.1.024] octane‐6,7‐dicarboxylate 15 and18, resp.) and of their N‐(tert‐butyloxy)carbonyl (14, 17) and V‐benzoyl (16, 19) derivatives are described. While treatment with nucleophilic acids (HCl, HBr. AcOH) of the exo, exo‐diesters 14 and 16 gave the corresponding products 23–27 of aziridine trans ‐addition, the exo, endo ‐diesters 17 and 19 led to the corresponding amino‐lactones 63 (methyl (1RS,2RS,3SR,6RS,7SR,9RS)‐2‐{[(tert‐butyloxy)carbonyl] amino}‐5‐oxo‐4,8‐dioxatricyclo[4.2.1.0 37] nonane‐9‐carboxylate) and 64 (methyl (1RS,2RS,3SR,6RS,7SR,9SR)‐2‐(benzoylamino)‐5‐oxo‐4,8‐dioxatricyclo[4.2.1.0 3′7] (nonane‐9‐carboxylate). Under non‐nucleophilic acidic conditions, the N‐benzoylaziridine 16 was rearranged quantitatively into dimethyl (1RS,2SR,26SR,67SR,7SR,8SR,9SR)‐4‐phenyl‐5,10‐dioxa‐3‐azatricyclo[4.3.1.02′7] dec‐3‐ene‐8,9‐dicarboxylate(31), and 19 into dimethyl (1RS,2SR,26SR,67SR,7SR,8SR,9SR)‐4‐phenyl‐3,10‐dioxa‐5‐azatricyclo [5.2.1.02′6] dec‐4‐ene‐8,9‐di‐carboxylate (65). Possible mechanisms of these highly selective reactions and rearrangements are discussed. Copyright © 1990 Verlag GmbH & Co. KGaA, Weinheim