An amino acid antimetabolite named YS-460 was isolated from the culture filtrate of a newly isolated Actinomycetes identified as Streptomyces sp. Fermentation was carried out in the synthetic medium at 30$circ$C for 5 days. Purification was done by ion exchange resin, active carbon, silica gel column chromatography and obtained 38 mg of pure active substance per liter of the broth. YS-460, an amino acid like substance, has the molecular formula of C$_{7}$H$_{11}$NO$_{3}$- Its structure determined to be furanomycin by spectral analysis. It is active against some bacteria on a chemically defined medium and reversed competitively by L-isoleucine and non-competitively by L-leucine and L-valine.