Synthetic Studies Toward Terpene Natural Products And Alkaloid (±)-Lepadiformine

The thesis mainly consists of the following two parts:Part I: Synthetic studies toward syntheses of terpene natural products which contain [5-8] and [5-5-5] fused-ring system.Two convenient procedures for syntheses of terpene natural products of hirsutene, (±)-pentalenene and (±)-asterisca-3(15),6-diene have been achieved, featuring Rh(I)-catalyzed [(5+2)+1] cycloaddition developed by Yu and co-workers in Peking University to construct a bicyclic cyclooctenone, which can be efficiently transformed to a symmetric or an unsymmetric bicyclic diketone regioselectively. These two kinds of diketones are advanced intermediates for the syntheses of natural products of hirsutene, (±)-pentalenene and (±)-asterisca-3(15),6-diene. We have also done some preliminary study of synthesis of (±)-coriolin.Part II: Synthetic studies toward synthesis of alkaloid (±)-lepadiformineVinylsilane-terminated cyclization reactions have proven to be particularly well-suited for the synthesis of complex natural products. we designed a general and efficient approach to synthesize alkaloid (±)-lepadiformine, featuring an intramolecular N-acyliminium ion initiated vinylsilane-terminated cyclization. After extensive experimental studies, we failed to complete this synthetic project. But this synthetic work gives us much valuable knowledge about the chemistry of alkaloids, vinylsilane and acyliminium ions.