Exploiting the borono-Mannich reaction in bioactive alkaloid synthesis

Abstract

We have demonstrated that the borono-Mannich reaction is a versatile and efficient reaction for the diastereoselective preparation of chiral 1,2-amino alcohols. These Mannich products are valuable starting materials as shown in this report by the synthesis of bioactive polyhydroxylated pyrrolizidine and indolizidine alkaloids. Initial studies, directed at the more complex Stemona alkaloids and using the borono-Mannich reaction on cyclic N-acyliminium ions, are encouraging, as demonstrated by the synthesis of the pyrido[1,2-a]azepine core structure of stemocurtisinol.