tert-butyl ((3S,4S,5S,5aS,13aS,14R)-14-bromo-4,12-dihydroxy-11,14-dimethoxy-7-methyl-13-oxo-3,4,5,5a,6,13-hexahydro-2H-3,13a-methanoanthra[2,3-b]oxepin-5-yl)carbamate