EPICUBENOL SYNTHASE AND THE ENZYMATIC CYCLIZATION OF FARNESYL DIPHOSPHATE

Incubation of [1-H-3]farnesyl diphosphate (2) with a cell-free extract obtained from Streptomyces sp. LL-B7 gave tritiated epicubenol (1), as confirmed by recrystallization of the derived triol 3 to constant activity. Cyclization of [13,13,13-H-2(3)]farnesyl diphosphate (2a) with crude epicubenol synthase gave [13,13,13-H-2(3)]epicubenol (1a), as established by H-2 NMR analysis. The existence of a 1,3-hydride shift was demonstrated by conversion of [1,1-H-2(2)]-farnesyl farnesyl diphosphate (2b) to epicubenol (1b) which was shown by H-2 NMR to be labeled with deuterium at C-5 and C-11. These results can be explained by a proposed cyclization mechanism involving the intermediacy of nerolidyl diphosphate (4).