12b-acetyloxy-2a,3,4,4a,5,6,9,10,11,12,12a,12b-dodecahydro-4,11-dihydroxy-12-(2,5-dimethoxybenzyloxy)-4a,8,13,13-tetramethyl-5-oxo-7,11-methano-1H-cyclodeca(3,4)benz(1,2-b)oxet-9-yl 3-(tert-butyloxycarbonyl)amino-2-hydroxy-5-methyl-4-hexaenoate