Chapter 27. Alkaloids and Other Natural Products

Abstract

Publisher Summary This chapter discusses studies focusing on alkaloids and other natural products. Three new Rhazya alkaloids, possessing the general structure of a hypothetical intermediate that could bridge the major types of indole alkaloids, were obtained from R. stricta and R. orientalis . The biogenetically modeled synthesis of minovine and ajmaline were reported. Both velbanamine, a degradation product of the antitumor alkaloids vinblastine and vincristine, and catharanthine were constructed from the same lactam intermediate. The application of transannular cyclization reactions to the synthesis of indole and dihydroindole alkaloids was described. In another study cherylline, an unusual tetrahydroisoquinoline alkaloid, was isolated from Crinum powellii . Cancentrine, from Dicentra canadensis , is a new type of dimeric benzylisoquinoline alkaloid (a morphine and cularine combination) whose structure was established by physical and chemical methods. Representatives of the optically active flavans, (−)-4'-hydroxy-7-methoxyflavan and (−)-4'-hydroxy-7-methoxy-8-methylflavan were obtained from species of Dianellinae. X-ray analysis established the structure of silydianin, from Silybum marianum . It is isomeric with the antihepatotoxic agent Silymarin and represents a unique combination of a dihydroflavonol and a phenylpropane.