16783-93-0 2,7-(Epoxypentadeca[1,11,13]trienimino)naphtho[2,1-b]furan-1,6,9,11,17(2H)-pentone, 5,16,19,21-tetrahydroxy-23-methoxy-2,4,12,16,18,20,22-heptamethyl-, 21-acetate, stereoisomer AIDS-070664 AIDS070664 Rifamycin YS