Water-soluble siomycin-A derivatives. Preparation, chemical structures and biological properties of half-esters of the peptide antibiotic.

The peptide antibiotic siomycin-A was transformed into half-esters with dicarboxylic acids with the intention of making siomycin-A soluble in water. Sodium salts of the half-esters were also prepared. Some of the salts showed antibacterial activities comparable to siomycin-A against Gram-positive bacteria in vitro and exhibited better therapeutic effects in infected mice than siomycin-A. The chemical structures of siomycin-A hemiadipate-II and -III were elucidated by comparing their 13C and 1H NMR spectra with those of siomycin-A. Their physicochemical properties are described.