Chapter 4 Application of Enamide Cyclizations in Alkaloid Synthesis

Abstract

Publisher Summary Alkaloids are a group of naturally occurring compounds that contain at least one nitrogen atom. Because of their potent and interesting pharmacological activities, alkaloids have been widely studied. The syntheses of alkaloids have provided many useful novel synthetic methodologies in the field of synthetic organic chemistry. The most abundant and interesting groups of alkaloids are the isoquinoline and indole alkaloids, possessing at least one nitrogen-containing, six-membered ring. The well-known Bischler–Napieralski, Pictet–Spengler, and Pomerantz–Fritsch syntheses have been studied extensively and successfully applied to a great number of total syntheses of these groups of alkaloids. Although a number of other effective synthetic methodologies have been developed for the synthesis of isoquinoline alkaloids, there remain quite a number of alkaloids, which have not been synthesized, even by using newer methods. This chapter illustrates the application of a compound enamide in alkaloid synthesis. Enamides are a group of compounds having the structures of N-α,β-unsaturated acylenamines and N-α,β-unsaturated acylanilides. These enamides are readily prepared by acylation of the corresponding imines or anilines with α,β-unsaturated acid chloride and are found to be considerably stable compounds, although losing reactivity to some extent when compared with the parent enamines.