General Synthesis of Phenanthroindolizidine, Phenanthroquinolizidine, and Related Alkaloids: Preparation of (+/-)-Tylophorine, (+/-)-Cryptopleurine, (+/-)-Septicine, and (+/-)-Julandine

Article abstract of DOI:10.1021/jo00187a022

A general synthetic route to the pentacyclic phenanthro class and related indolizidine and quinolizidine alkaloids via β-amino ketone intermediates is reported.The synthesis of tylophorine, cryptopleurine, septicine, and julandine, in racemic forms, has been described.Synthetic steps in the preparation of these alkaloids involve 1,3-dipolar cycloadditions of the cyclic nitrones as a common feature followed by crucial ring closure by aldol reactions and photolyses.