methyl (E)-5-((2S,3R,4aS,5aR,7aS,9R,10S,12R,12aR,13aS,14aR)-3-(benzyloxy)-2-(2-(benzyloxy)ethyl)-10-hydroxy-2,4a,5a,12-tetramethylhexadecahydrooxepino[3,2-b]pyrano[2',3':5,6]pyrano[2,3-f]oxepin-9-yl)-4-((tert-butyldimethylsilyl)oxy)-4-methylpent-2-enoate