Marine natural products. VIII. Pachydictyol A, an exceptional diterpene alcohol from the brown alga, Pachydictyon coriaceum

The structure of one of the constituents of Pachydictyon coriaceum, which has mild antibiotic activity against Staphylococcus aureus is reported. Hexane extraction of the seaweed followed by column chromatography on silica gel led to isolation of a new diterpene alcohol, pachydictyol A. Its structure and absolute stereochemistry was obtained by an X-ray crystallographic analysis of its p-bromophenylurethane derivative. Its possible biosynthesis is discussed.