PROTEASE INHIBITORS

摘要

Novel procidins having the structure wherein R1 and R2, which may either be identical or different, represent isopropyl or isobutyl; and R4 represents hydrogen, carboxyl or methyl carboxylate when both R1 and R2 are isopropyl, or R4 represents carboxylic when R1 and R2 are both isobutyl, or R1 and R2 differently represent isopropyl or isobutyl, such procidin occurring as a mixture of compounds when R1 and R2 are different are provided herein. Such procidins are produced and accumulated in the cultured product of a novel strain Streptomyces procidinanus. Such procidins are effective in the preventive treatment of ulcers.