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The reaction of benzoylation of bleomycetin, a glycopeptide antibiotic, and its cuprum complex was studied with the chloranhydride and carbodiimide methods. Acylation of the antibiotic cuprum complex by an equivalent quantity of benzoyl chloride resulted in formation of a mixture of mono- and disubstituted derivatives while with the use of a 3-fold excess of chloranhydride it was possible to obtain dibenzoylbleomycetin as a sole reaction product. Interaction of the bleomycetin cuprum complex with activated benzoic ether resulted in formation of a product monosubstituted by the antibiotic spermidine fragment. After acylation of the free antibiotic by the carbodiimide and chloranhydride methods tri- and tetrabenzoyl derivatives of bleomycetin were isolated respectively.

Bleomycetin, an antitumor antibiotic, was subjected to chemical modification by the C-end fragment i.e. the residue of 3-[(4-aminobutyl)amino]propylamine (spermidine++) with acylation, carbamoylation and reducing alkylation, which yielded its new semisynthetic derivatives. The use of physicochemical methods showed that the chemical modification involved the primary and secondary amino groups++ of spermidine++ and gave rise to N,N'-diacyl, N,N'-dicarbamoyl and N,N'-dialkyl bleomycetins. The biological properties of the derivatives, i.e. their cytotoxic activity, acute and pulmonary toxicities were studied. The transformation of bleomycetin by the C-end fragment lowered the antibiotic toxicity and was believed to be a promising approach to modifying its molecule.