The synthesis of vallartanone B, a γ-pyrone-containing polypropionate from the marine mollusc Siphonaria maura, is described. A γ-pyrone moiety, which was constructed by PPh3-CCl4 cyclization of a β-triketone, and a C1-C6 segment were joined by a Sn(OTf)2 aldol reaction and converted to vallartanone B. This synthesis allows for revision of the stereochemistry at C8. A conformational analysis was performed