An alkaloid of Dioscorea hispida, Dennstedt–IV Further investigations on the lactose ring

Reductive degradation of the lactone ring of dioscorine has yielded a saturated tertiary alcohol, the formation of which means that the previously proposed formula (I) for the alkaloid is incorrect. The lactone and tropane systems are linked in a spiro manner, as in (VI) or (VII), of which the former is preferred for dioscorine. The behaviour of the alkaloid on Hofmann degradation can be explained on the basis of structure (VI). From infra-red studies on the above tertiary alcohol dioscorine is derived from 7-hydroxytropane, and the (–)-base is therefore (XX) or its optical enantiomorph.