Optically active [m.n.l]propellanones have been prepared by diastereoselective cyclopropanation of homochiral ene ketals derived from 1,4-di-O-benzyl-L-threltol and readily available bicyclic enones. Propellanones are a synthetically useful subset of the structurally and theoretically interesting propellane family. I [m.n.l]Propellanes are most conveniently prepared by cyclopropanation of the corresponding bicyclic alkene.2 Cm.n.llPropellanones, although more difficult to prepare by direct cyclopropanation, are particularly attractive as precursors of bicyclic ring systems bearing angular methyl3 or functionalized angular methyl substituents4 found in a number of natural products. An enantioselective synthesis of such systems would render them all the more attractive as synthetic intermediates. We herein report a general, efficient, enantioselective synthesis of [m.n.l]propellanones which utilizes chiral protecting group methodology. Recently we described a novel diastereoselective cyclopropanation of homochiral ketals derived from simple monocyclic enones and 1,4-di-l)-benzyl-l-threitol (Scheme I, First Equation).5 Following this observation, we sought to extend the applicability of the method to more complex bicyclic systems (Scheme I, Second Equation). The results of our survey appear in Table .