Acetic acid, [(2S,6S)-tetrahydro-2-methoxy-2-[(2E)-4-[(4-methoxyphenyl)methoxy]-1, 1-dimethyl-2-butenyl]-6-[(2R,3R)-2-[(4-methoxyphenyl)methoxy]-3-(phen ylmethoxy)butyl]-3-oxo-4H-pyran-4-ylidene]-,