汎用性合成素子の不斉構築と高効率天然物合成

抄録

This article deals with a compilation of recent developments in the asymmetric synthesis of versatile chiral building blocks and with their application to the natural product syntheses carried out in our laboratories. The asymmetric construction of a versatile chiral building block for biologically active natural and non-natural compounds would provide us with powerful tools for the syntheses of these molecules. As one of the efforts to make a breakthrough for the enantioselective alkaloid synthesis, we designed, as chiral educts, some piperidines, pyrrolidines, and pyrrolidones provided with versatile functionality. These chiral azacycles were constructed by using an asymmetric intramolecular Michael reaction, the Katsuki-Sharpless asymmetric epoxidation followed by sequential regioselective amination and intramolecular cyclization, and the asymmetric cleavage of σ-symmetric 'fork head ketone'systems, respectively. The resulting chiral building blocks were converted to Rauwolfia alkaloids (e.g. ajmalicine, tetrahydroalstonine, and yohimbine), an unusual amino acid (e.g. bulgecinine), and indolizidine alkaloids (e.g. monomorine I and indolizidine 223 AB), respectively.