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 ^1^4C, ^1^3C, ^2H and ^3H and, particularly in
connection with E-ring biosynthesis, required new approaches to the
demanding chemical and stereochemical requirements of the experimentation.