Total Synthesis of balanol, Part 2. Completion of the Synthesis and Investigation of the Structure and Reactivity of Two Key heterocyclic Intermediates

A convergent enantioselective total synthesis of the natural product (-)-balanol (1) is described. In addition to benzophenone fragment 8, key intermediates are chiral bicyclic aziridine 3 and the corresponding epoxide 4, both of which undergo highly regio- and stereoselective nucleophilic ring-opening reactions, allowing control of the two stereogenic centres of the target molecule. The structure and reactivity of 3 and 4 have been investigated in some detail. (C) 1997 Elsevier Science Ltd.