Pintoxolanes A-C, Highly Functionalized 3,14-Oxa-bridged Cembranoids from the Caribbean Gorgonian Coral Eunicea pinta

Three new cembrane-based diterpenes possessing the rare 3,14-oxa-bridged moiety were isolated from the hexane extract of a southwestern Caribbean gorgonian octocoral, Eunicea pinta, together with seven known cembranoid diterpenes. The structures of pintoxolanes A-C (1-3, resp.), including their relative configurations, were deduced from spectroscopic data and chemical-correlation experiments. Experimental evidence hinting to a plausible biogenesis of the 3,14-oxalane moiety is provided. Preliminary cytotoxicity data for compounds 1-3 toward human cancer cell lines are also provided.