(1′R,2S,3R,4′S,5S,6S,8′R,10′Z,12′R,13′S,14′Z,20′R,21′R,24′S)-6-[(2E)-2-Buten-2-yl]-3,24′-dihydroxy-21′-methoxy-5,11′,13′,22′-tetramethyl-2′-oxo-3,4,5,6-tetrahydrospiro[pyran-2,6′-[3,7,19]trioxatetracy clo[15.6.1.1~4,8~.0~20,24~]pentacosa[10,14,16,22]tetraen]-12′-yl 2-methylpropanoate