53969-01-0 BRN 1419445 Hydroxyrubromycin Purpuromycin Spiro(benzo(1,2-b:5,4-c)-dipyran-2(3H),2'(3'H)-naphtho(2,3-b)furan)-7-carboxylic acid, 4,5',8',9-tetrahydro-4,4',9',10-tetrahydroxy-7'-methoxy-5',8',9-trioxo-, methyl ester