Although the “rothrockyl” skeleton represents a new structural class of naturally occurring organic molecules, its biological existence was predicted in 1973.2 The iso- lation of 6 provides support for the unified approach to irregular monoterpene biosynthesis and for the proposal that plant enzyme systems might act as simple models for the study of squalene biosynthesis in mammals. ... Registry No. (-)-tram-6,80082-35-5; (f)-trans-6, 80082-36-6; 7, 1530-32-1; ...