Antimetabolites produced by microorganisms. XII. (S)-alanyl-3-(.ALPHA.-(S)-chloro-3-(S)-hydroxy-2-oxo-3-azetidinylmethyl)-(S)-alanine, a new .BETA.-lactam containing natural product.

(S)-Alanyl-3-[alpha-(S)-chloro-3-(S)-hydroxy-2-oxo-3-azetidinylmethyl]-(S)-alanine was isolated from a fermentation broth of an unidentified Streptomyces species 372 A. The structure was determined by single crystal X-ray diffraction analysis. The substance inhibits the growth of several strains of gram-positive and gram-negative bacteria in a chemically defined medium but growth inhibition is relieved by addition of L-glutamine to the medium.