a- and ß-snyderol; new bromo-monocyclic sesquiterpenes from the seaweed Laurencia

Brominated bicyclic sesquiterpenes of the chamigrene ring system are cOnnmOn metabolites found in many species of the marine red alga Laurencia 1 . The biosynthesis of these compounds has been generally predictedA*' to involve the intermediacy of a brominated monocycle-farnesol derivative in analogy to the probable biosynthesis of the parent hydrocarbon3. To support these contentions, we wish to report that at least two species of Laurencia contain bromo monocyclonerolidol derivatives closely related to the proposed biosynthetic precursor. Standard chromatographic procedures resulted in the isolation of a-snyderol (A) from &. obtusa (Iluds.) Lamouroux (15% CHC13 extract) and B-snyderol (2 from &. snyderae Dawson (25% CIiC13 extract). &. obtusa was collected in Way, 1975 along the eastern Spanish coast in Tossa de War, while L. snyderae, a local species, was collected in June, 1974 in La Jolla, California.