Minor and Trace Sterols in Marine Invertebrates. 27. Isolation, Structure Elucidation, and Partial Synthesis of 25-Methylxestosterol, a New Sterol Arising from Quadruple Biomethylation in the Side Chain

Article abstract of DOI:10.1021/jo00332a021

A novel C31 sterol, 25-methylxestosterol, resulting from quadruple biomethylation in the side chain has been isolated as a trace constituent of the sterol fraction from a Caribbean sponge (Xestospongia sp.).Its structure (1, 24-methylene-25,26,27-trimethylcholesterol) has been elucidated by spectroscopic methods and confirmed by partial synthesis.A biosynthetic route leading to 1 is proposed that is consistent with the hypothesis of stepwise biomethylations and with earlier discoveries of "extended" side chains among marine sterols.