Several acyl derivatives of hitachimycin have been synthesized and their activities, including antibacterial, cytocidal against HeLa cells and in vivo antitumor against sarcoma 180, evaluated. Some of these derivatives showed higher antitumor activity than hitachimycin. Among the derivatives, 11-O-propionyl-15-O-butyrylhitachimycin (12) and the 11-O-acylhitachimycins (15-17) were most effective in in vivo assay.