17aH-8a,16-endo-Oxiranonaphtho(2',3':5,6)cyclohepta(1,2-c)xanthene-17a-carboxylic acid, 7-chloro-1,2,3,5,8,9,15,16-octahydro-1,4,6,10,13,14-hexahydroxy-18-methyl-5,9,15-trioxo-, methyl ester, (1S-(1alpha,8aalpha,16alpha,17aalpha,18S*,20R*))-