Gorgosterol structure

Establishment of the dietary or symbiotic origin of sterols could be a difficult task, unless the tracer sterol has an unusual structure and restricted occurrence. There is little doubt, for example, that petrosterol (59) found in the nudibranch Peltodoris atromaculata [112] arises from predation of the mollusc on the sponge Petrosia ficiformis, from which the sterol was first isolated [113]. However, the origin of gorgosterol (60) in Tridacna species has not yet been established [114] despite its unusual structure. 

Crystal structures and absolute configurations have been determined by X-ray methods for two marine sterols (8) and (9), related to gorgosterol, with a cyclopropane ring in the side-chain, for 8-aza-oestradiol, 3 -acetoxy-17a-iodoandrost-5-ene, and withanolide E, which is found to have the unusual 17a-configuration (10). Structure determinations of 2 -hydroxytestosterone... 

A new remarkable side chain alkylation pattern has been found in calysterol, the principal sterol component of the sponge Calyx nicaensis 75a). Structure (181), reminiscent of those of gorgosterol (175) and its relatives (176) and (177), has been proposed for this unique sterol on the basis of spectral data (m.s. and n.m.r.) of the acetate, m.p. 105—106°, [a]o-34.3°, and Lemieux oxidation of the corresponding stanol to a p-diketone (182). Interestingly, calysterol (181) completely decomposes on an alumina-silver nitrate column to give four compounds the major one has been characterized as (182 a). 

Ling, N. C., R. L. Hale, and Carl Djerassi The Structure and Absolute Configuration of the Marine Sterol Gorgosterol. J. Amer. Chem. Soc. 92, 5281 (1970). 

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