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.
1. The optical rotatory dispersion and circular dichroism of the antibiotic A-128-OP and derivatives of it have been investigated in the wavelength range from 230 to 450 nm.
1. Seven different derivatives of the polypeptide antibiotic A-128-OP at its α-amino group have been obtained for the first time, and their physicochemical and antibiotic properties have been studied.
1. Derivatives of the polypeptide antibiotic A-128-OP at positions 1, 2, and 3 of the indole rings of the β-methyltryptophan and dehydrotryptophan residues have been obtained for the first time, and their physicochemical properties have been studied.