Selective modification of the free amino groups of the antibiotic ristomycin A

: Selective chemical modification of ristomycin A (I) by the free NH2 groups was performed. 6 different N-acyl and N-aminoacyl derivatives of I were obtained. 5 of them showed antibacterial activity within 0.4-10.0 micrograms/ml against 4 test microbes. The biological activity of the derivatives depended on the substituent type and the molecule total charge: mono-N-L-isoleucyl-I with the charge of +2 had the highest activity and N,N'-disuccinyl-I had the lowest activity.