A novel antitumor antibiotic, methylenolactocin, was isolated from the culture nitrate of a new isolate of fungus identified as Penicillium sp. The fermentation yield reached about 100 mg per liter of the broth. Methylenolactocin has the molecular formula of CnHi6O4 and possess an exomethylene lactone structure. Its structure was determined to be 3-carboxy-2-methylene-4-nonanolide by spectroscopic data. It is active against some Gram-positive bacteria and it prolongs the life span of mice inoculated with Ehrlich carcinoma.

The structure of plumbemycin A and B, new antimetabolites from Streptomyces plumbeus, which are antagonist of L-threonine, were assigned to be L-a1any1-L-aspartyl-D-2-amino-5phosphono-3-cis-pentenoic acid and L-alanyl-L-asparaginyl-D-2-amino-5-phosphono-3-cispentenoic acid, respectively.

New antimetabolite N-1409, an antagonist of L-threonine was isolated from the fermentation broth of Streptomyces. Taxonomical study on the producing strain made it a new species and named Streptomyces plumheus n. sp. Sakai et Park after its leaden color of matured aerial mycelium.N-1409 substance was isolated as colorless needles, mp 218~220°C. Its molecular formula C12H 21N.08P·3/2 H 20 was determined by elementary analysis and alkali titration. On acid hydrolysis, L-alanine, L-aspartic acid and a new phosphorus containing amino acid were obtained.

The structure of plumbemycin A and B, new antimetabolites from Streptomyces plumbeus , which are antagonist of L-threonine, were assigned to be L-alanyl-L-aspartyl-D-2-amino-5phosphono-3-cis-pentenoic acid and L-alanyl-L-asparaginyl-D-2-amino-5-phosphono-3-cispentenoic acid, respectively.

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