(3S,4S,5R,8E,10R,11R,12E,14E,16S,17R)-3,4-bis(4-methoxybenzyloxy)-5-[(4-methoxybenzyloxy)methyl]-8,10,12,14,16-pentamethyl-11-(triphenylsiloxy)-17-[(1S)-1-methylundecyl]-1,6-dioxa-8,12,14-cycloheptadecatriene-2,7-dione