Minor and trace sterols in marine invertebrates V. Isolation, structure elucidation and synthesis of 3beta-hydroxy-26,27-bisnorcholest-5-en-24-one from the sponge Psammaplysilla purpurea.

The free sterol mixture of the sponge Psammaplysilla purpurea was shown to contain aplysterol as the major constituent. In addition to other sterols such as 5,7-cholestadien-3beta-ol, cholesterol, 5alpha-cholestan-3beta-ol, 24epsilon-methylcholesta-5,22-dien-3beta-ol, 24epsilon--methylcholesterol, 24epsilon-ethylcholesta-5,22-dien-3beta-ol and 24,28-dehydroaplysterol, a new minor sterol was isolated and shown by spectral analysis as well as partial synthesis to be 3beta-hydroxy-26,27-bisnorcholest-5-en-24-one. The sterol mixture contains no other short side chain or 24-keto sterols except for small amounts of 3beta-hydroxypregn-5-en-20-one and 3beta-hydroxy-5alpha-pregnan-20-one.