129791-94-2 3'-Hydroxy-5'-(4-sec-butylpiperazinyl)benzoxazinorifamycin Krm 1668 Krm 1686 Krm 1687 Krm-1668 Rifamycin viii, 1',4-didehydro-1-deoxy-1,4-dihydro-3'-hydroxy-5'-(4-(1-methylpropyl)-1-piperazinyl)-1-oxo-