The oxidation profile at C-18 of furanocembranolides may provide a taxonomical marker for several genera of octocorals

Abstract

The furanocembranolides 1–3 along with the known compounds pukalide, pukalidealdehyde, epoxypukalide, and leptolide were isolated from Leptogorgia spp. and their structures were determined by spectroscopic evidences. An NMR-based method using Pirkle's reagent at low temperature allowed us to determine the absolute configuration at C-10 of a γ-butenolide unit embedded in a flexible furanocembranolide network. The C-18 of furanocembranolides undergoes an oxidation cascade leading from a methyl group to a carboxylic acid/ester that appears to be genus specific. We introduce the concept genus-specific oxidation, a feature that provides a chemotaxonomical marker for several genera of octocorals. This concept also allowed us to propose a biogenetic pathway for these compounds.