Polypropionates from the South African Marine Mollusk <i>Siphonaria oculus</i>

Three new polypropionate metabolites, 6<i>Z</i>,8<i>E</i>-Δ⁸-siphonarienfuranone (<b>1</b>), 6<i>E</i>,8<i>E</i>-Δ⁸-siphonarienfuranone (<b>2</b>), and 6<i>E</i>,8<i>E</i>-3-hydroxy-4,6,8,10,12-pentamethylpentadeca-6,8-dien-5-one (<b>3</b>), and the known polypropionate siphonarienfuranone (<b>4</b>) were isolated from the intertidal South African marine mollusk <i>Siphonaria oculus</i>. Evidence is presented to suggest that <b>1</b>, <b>2</b>, and <b>4</b> may cyclize from an acylic precursor on chromatographic workup of the acetone extract of this mollusk