Structural revision of peribysins C and D

The terpenes constitute the largest family of substances of natural occurrence, being widely distributed in the plant kingdom and to a lesser extent in the animal kingdom They are divisible according to the number of carbon atoms present into several groups, one of which is labeled sesqui-terpenes and is comprised of molecules containing fifteen carbon atoms The sesquiterpenes are the largest group of terpenes, and are themselves subdivisible according to the arrangement of the carbon atoms in the molecular skeleton In this chapter we shall be concerned with a subgroup having its carbon atoms arranged, in the main, in a bicyclic framework corresponding to a parent hydrocarbon formulated, for the moment without stereochemical implication, as (1) and named eremo-philane These sesquiterpenes have been reviewed earlier (1, 2, 2a) We shall include with them a small group of closely-related sesquiterpenes having a carbon skeleton in which ring B in (1) has been contracted to a five-membered carbocycle, as in (2)

The Chemistry of the Eremophilane and Related Sesquiterpenes

The title compound, formula C15H20O2, is orthorhombic, P212121 witha=8.747(2),b=12.025(3),c=12.554(3)A,Z=4, andD m =1.32(2)g/ml. The structural analysis shows that the compound corresponds to eudesma-4(15),7(11)-dien-8α,12-olide, a sesquiterpene lactone previously isolated fromAster umbellatus but whose crystal structure was unknown.

The crystal structure of eudesma-4(15),7(11)-dien-8α, 12-olide: a sesquiterpene lactone fromTrattinickia rhoifolia Willd

The structure of eremophilenolide is confirmed to be (1) by X-ray analysis. The cis-fused decalin system takes all chair “steroid-like conformation.”

Naoko Takada

Papers

X-ray structure determination of eremophilenolide