(9,9'-Bi-4H-naphtho(2,3-b)pyran)-4,4'-dione, 5,5',6,6,8,8'-hexahydroxy-2,2'-dimethyl-, (R)- (R)-5,5',6,6,8,8'-Hexahydroxy-2,2'-dimethyl-(9,9'-Bi-4H-naphtho(2,3-b)pyran)-4,4'-dione 3692-07-7 Ustilaginoidin A