Reaction of cytisine with alka-1,3- and -2,3-dien-2-ylphosphonates

Abstract

Methods have been developed for functionalizing the alkaloid cytisine via introduction of alka-1,3- and -2,3-dien-2-ylphosphonate fragments. The main pathway of the reaction of cytisine with 2-(diethoxyphosphoryl) alka-2,3-dien-1-yl methanesulfonates is nucleophilic substitution of the methanesulfonyloxy group with retention of the alkadiene skeleton. A minor reaction pathway is nucleophilic substitution with formation of alka-1,3-dien-2-ylphosphonates. Cytisine conjugates with exclusively alka-1,3-dien-2-ylphosphonate fragment have been synthesized by copper(I)-catalyzed 1,3-dipolar cycloaddition of N-(prop-2-yn-1-yl)cytisine to 3-azidoalka-1,3-dien-2-ylphosphonates.