Minor and trace sterols in marine invertebrates 30. Isolation, structure elucidation and partial synthesis of 26-methylstrongylosterol and 28-methylxestosterol - two marine sterols arising by a novel quadruple biomethylation sequence

✍ Scribed by Lian Niang Li; Carl Djerassi

• Publisher: Elsevier Science
• Year: 1981
• Tongue: French
• Weight: 247 KB
• Volume: 22
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)83001-x

✦ Synopsis

Two new sterols, 26-methylstronqylosterol (3) and 28-methylxestosterol (5), arlSiW from a hitherto unknown quadruple biomethylationsequence, together with the biogenetically important "missing link", durissimasterol (6), were isolated from the Indo-Pacific sponge Strongylophora durissina. Recently we documented the first examples of quadruple biomethylation in the sterol side chain -xestospongesterol (J),3 isoxestospongesterol (2)3 and 25-methylxestosterol (J).4 The played the diagnostic peaks (E/Z 215,233,255 and 273) for the nucleus of a saturated stanol. The absence of a C-6 vinylic proton in its NMR spectrum and the expected 15 chemical shifts for the C-18 and C-19 methyl groups (0.631 and 0.797 ppm) were only consistent with a 3@-hydroxy-5asaturated nucleus. The nature of the extra unsaturation in the nuclei of N and 11 was demonstrated easily by the characteristic mass and NMR spectra of such A 5,7 and A5y7yg~1)-unsaturated 3B-hydroxy sterols.16y17