KF77-AG6, an antipain-related metabolite.

Recently we reported') the isolation and structural elucidation of a SAKAGUCHI-positive metabolite of Streptomyces, found in the course of chemical screening of microbial metabolites. The compound proved to be identical to antipain=' discovered as a protease inhibitor. In the present paper, we wish to report the isolation of another SAKAGUCHI-positive metabolite, KF77-AG6, which corresponds to the ureylene group-containing part of antipain, i.e. [(S)-1-carboxy-2-phenylethyl]carbamoyl-Larginine". KF77-AG6 is produced by a strain of Streptomyces fllipinensis3' (the Laboratory No. KF77-AG6), from which antipain was not produced. A part of the biological effect of KF77AG6 (described as AN) has already been reported'.