Two Novel Sesquiterpenes and A New Pregnane Derivative from the South China Sea Gorgonian Subergorgia suberosa

Two novel sequiterpenes isosuberosenol A (1), suberosain A (2), and a new pregnane derivative 4-hydroxymethyl-5 beta-pregnan-3, 20-dione (3) have been isolated from the South China Sea gorgonian Subergorgia suberosa. Their structure and relative stereochemistry were established based on the detailed spectroscopic analysis, including HR-ESI-MS, 1D- and 2D NMR spectra. The skeleton of isosuberosenol A (1) have been previously undescribed. The discovery of isosuberosenol A (1) provides some strong support for the plausible biogenetic pathway of quadrone type sesquiterpenes.