Scalaradial, a Sesterterpenoid Metabolite from the Marine Sponge Cacospongia mollior

Abstract

The X-ray study of scalaradial [Cimino, De Stefano & Minale (1974). Experientia, 30, 846-847], the major secondary metabolite from the marine sponge Cacospongia mollior, is reported. In the crystal of 12-(acetyloxy)-4,4,8-trimethyl-D-homoandrost-16-ene-17,17a-dicarboxaldehyde, C 27 H 40 O 4 , the asymmetric unit comprises two molecules which display high geometrical and conformational similarity. All the saturated rings are in chair conformations, whereas the cyclohexene ring adopts a half-chair form. The molecule is highly bent in a direction normal to the average skeletal plane, with rings A and C forming an angle of about 30°. The four axial iso-oriented methyl groups in the tetracyclic system produce distortions of the skeletal geometry similar to those observed in other molecules with analogous sequences of axial substituents, and are probably responsible for the remarkable bend of the skeleton.