Tropical Marine Algae. V. The Structure Determination of Two Novel Sesquiterpenes From the Red Alga Laurencia tenera (Rhodophyceae, Ceramiales, Rhodomelaceae)

Abstract

Laurencia tenera has been shown to contain two novel sesquiterpenes. The structure of the less abundant metabolite (3) was determined by single-crystal X-ray diffraction as (1S,2R,4S,5R,6R,8S,9R)-4,8-dibromo-2,5,6,9-tetramethyltricyclo[7.2.0.0^1.6] undecane-3-one.‡ The more abundant, but less stable metabolite (4) was investigated by extensive high-field N.M.R. spectroscopy. Its structure is proposed as (1S*,2R*,4R*,5R*,6R*,8R*)-4-bromo-2,5,6-trimethyl-11-methylenetricyclo[6.2.1.0^1.6]undecan-3-one.§ The sesquiterpene (3) is isomeric with the known metabolite perforatone (5).