2,7-(Epoxypentadeca[1,11,13]trienimino)naphtho[2,1-b]furan-1,6,9,11(2H)-tetrone, 5,17,19,21-tetrahydroxy-23-methoxy-2,4,12,16,18,20,22-heptamethyl-, 21,?-diacetate 31692-65-6 8-O-Acetylrifamycin S NSC251227 Rifamycin, 1,4-dideoxy-1,4-dihydro-1,4-dioxo-, 8-acetate