Organometallic enantiomeric scaffolding: organometallic chirons. Total synthesis of (-)-Bao Gong Teng A by a molybdenum-mediated [5 + 2] cycloaddition

Bao Gong Teng A, an optically active tropane alkaloid with hypotensive and miotic activity isolated from the Chinese herb Erycibe obtusifolia Benth, was synthesized by an "organometallic chiron" strategy in which single enantiomers of TpMo(CO)(2)(eta(3)-pyridinyl) complexes are produced in quantity and then elaborated easily and efficiently to generate, after demetalation, highly enantiopure advanced synthetic intermediates possessing the tropane core.