As the results of our screening of culture filtrates of microorganisms for chemical color reactions, dienonlycins, sphydrofuran and arglecin had already been found as metabolites of Streptomyces. As a continuation of this work, we report the isolation and structural elucidation of a new metabolite phosphoramidon produced by Streptomyces termshiensis and identified via color screening with Ehrlich reagent. Phosphoramidon in the culture filtrate was adsorbed on charcoal, eluted with methanol at pH 8.0, and isolated by column chromatography with cellulose and Sephadex LH-20, then crystallized as ammonium, cyclohexylammonium or dicyclohexylammonium salts. Mild acid hydrolysis of phosphoramidon afforded L-leucyl-L-tryptophan (a dipeptide) and L-rhamnopyranose (a monosaccharide). Derivatization (e.g., methylation) combined with NMR analysis—including comparison with the NMR spectrum of α-L-rhamnopyranosyl-l-phosphate (revealing 1C conformation and anomeric proton couplings J₁,₂ ~1.5Hz and Jₚ,CH ~8Hz)—confirmed the anomeric configuration. Based on elemental analysis, spectral data (IR, UV, NMR), hydrolysis products, and derivatization studies, phosphoramidon was concluded to be N-(α-L-rhamnopyranosyloxyhydroxyphosphinyl)-L-leucyl-L-tryptophan. Notably, this chemical screening procedure disclosed a metabolite containing a labile phosphoramido group.