Assignment of absolute configuration of bis-gamma-pyrone polypropionates from marine pulmonate molluscs.

The absolute configurations of onchidione (1), previously reported from the marine pulmonate Onchidium sp., and the related alcohols onchidiol (2) and 4-epi-onchidiol (3), first described as methanolysis products of 1, were assigned by X-ray diffraction analysis and solid-state time-dependent density functional theory electronic circular dichroism. Alcohol 3 was incorrectly reported as the C-16 epimer of 2.