BIOSYNTHESIS OF SESQUITERPENES FROM DEUTERATED MEVALONATES IN PERILLA-CALLUS

Cyclization mechanisms of sesquiterpenes including cuparene, beta-bisabolene, and alpha-curcumene have been studied by GC/MS analyses of the deuterated sesquiterpenes that were biosynthesized from deuterated mevalonates in callus of Perilla fruterscens Britton var. crispa Decne f. purpurea Makino (akachirimenshiso in Japanese). The labeling patterns of cuparene demonstrate a concurrent mechanism of a 1,4-hydride shift, and a double 1,3-hydride shift to form the cyclopentane ring, and the losses of two H-5 atoms and one H-2 atom of mevalonate to form the aromatic ring. It is postulated that a C-C bond in the cyclohexene ring of beta-bisabolene might partly migrate to the neighboring C-C bond with the loss of one H-2 atom in mevalonate in its formation. The labeling patterns of deuterated alpha-curcumene indicate a 1,2-hydride shift to form the aromatic ring.