A new component, nanaomycin C, has been isolated from culture medium of Streptomyces rosa var. notoensis, which had been found to produce nanaomycins A and B. Nanaomycin C is an amide of nanaomycin A. Biological activities of nanaomycin C and several derivatives of nanaomycin A are also shown. Acetylnanaomycin A exhibits as strong activities against Gram-positive bacteria, fungi and Mycoplasma gallisepticum as nanaomycin A.