SESQUI-TERPENE AND DI-TERPENE BIOSYNTHESIS FROM C-13 LABELED ACETATE AND MEVALONATE IN CULTURED-CELLS OF HETEROSCYPHUS-PLANUS

Cultured cells of the liverwort, Heteroscyphus planus, accumulate a wi de variety of sesquiterpenes and diterpenes of the clerodane type. C-1 3 Atoms Of [2-C-13]acetate and [2-C-13]- and [4,5-C-13(2)]-mevalonates (MVAs) are incorporated into sesquiterpenes more extensively than int o diterpenes by cultured cells of H. planus. (1S)-7-Methoxy-1,2-dihydr ocadalene, a predominant sesquiterpene, and heteroscyphic acid A, a ma in diterpene, incorporating C-13 labelled precursors were analysed by C-13 NMR spectroscopy. Preferential labelling of the farnesyl diphosph ate (FPP)-derived portion of heteroscyphic acid A was confirmed by C-1 3 enriched peaks and C-13-C-13 couplings, while sesquiterpenes were la belled equivalently. From these results, it appears that separate site s for sesquiterpene and diterpene biosynthesis exist in cultured cells of H. planus as could be observed in higher plants. Since the same ty pe of nonequivalent labelling was observed in the phytyl side chain of chlorophyll by other experiments, it is suggested that all compounds, which are formed from GGPP within chloroplasts, are biosynthesized pa rtly via the condensation of FPP derived from exogenous MVA with endog enous isopentenyl diphosphate in chloroplasts. A 1,2-methyl migration of the methyl group originating at C-3 of MVA is also confirmed in the biosynthesis of the trans-clerodane skeleton.