BIOSYNTHESIS OF STEROID DERIVATIVES IN PLANTS .10. SPIROSTANOL BIOGENESIS FROM DELTA4-CHOLESTENONE AND OTHER POSSIBLE PRECURSORS

Labelled 22-oxocholesterol or 22-(ξ)-hydroxycholesterol are not converted, in Digitalis plants, to tigogenin or gitogenin. 3(α)-T-desmosterol gives radioactive cholesterol, but not labelled spirostanols, while 4-14C-cholestenone forms radioactive tigogenin and gitogenin. The biosynthesis of the spirostanols has to pass therefore through the 3-keto form. Tigogenin is metabolized little and forms, in Digitalis plants, no gitogenin and, in tomato plants, no tomatidine. © 1968.