(1S)-1,2,3,4a,9a,10-Hexahydro-2β,5,10α-trihydroxy-6-[(9,10-dihydro-1,8-dihydroxy-5-acetyl-6-methyl-9,10-dioxoanthracen)-2-yl]-2-methyl-1β-[(R)-1-acetoxyethyl]-4aα,9aα-epoxyanthracene-4,9-dione