Biosynthesis in the rotenoid group of natural products: Applications of isotope methodology

Using the natural rotenoids rotenone, amorphigenin, deguelin, rotenonic acid, dalpanol and munduserone as examples, their phytochemical biosynthesis has been examined in Derris elliptica, Amorpha fruticosa and Tephrosia vogelii. The rotenoids are advanced isoflavonoids, and construction of their angular A/B/C/D-ring systems has been studied experimentally starting out from simple primary metabolites and passing through a series of mainly oxidative phases. The oxidative reactions of rot-2'-enonic acid which biosynthetically form the E-rings of rotenone, amorphigenin, dalpanol and deguelin have been studied in both chemical and stereochemical detail using seedling preparations and the enzyme deguelin cyclase. This investigation has extensively employed substrates isotopically labelled with C-14, C-13, H-2 and H-3 and, particularly in connection with E-ring biosynthesis, required new approaches to the demanding chemical and stereochemical requirements of the experimentation. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.