Synthesis of Alkaloid Demissidine Stereoisomers and Analogues.

Demissidine is an indolizidine alkaloid isolated from several potato species. A simple synthesis of demissidine stereoisomers and analogues from a common steroidal sapogenin tigogenin is presented in the paper. The key intermediate in the synthesis of these compounds is readily available tigogenoic acid. Its step-by-step transformation to indolizidine yielded 20,25 or 20,25 products while the direct reductive amination produced the 20,25 compound (25--demissidine).