The structure of anticapsin, a new biologically active metabolite of Streptomyces griseoplanus.

1. Physical and analytical data obtained on crystalline anticapsin indicated the empirical formula C(9)H(13)NO(4). Spectral data (u.v., i.r. and proton magnetic resonance) and formation of l-tyrosine on hydrolysis revealed the functionalities and carbon skeleton of the new epoxy keto amino acid. 2. The optical properties of anticapsin (optical rotatory dispersion and circular dichroism) permitted assignment of absolute configuration to the new metabolite. 3. Treatment of anticapsin with hot methanolic hydrochloric acid followed by acetylation gave C(18)H(19)NO(5), the alpha-alkoxycyclohexenone derivative. Analysis of the nuclear-magnetic-resonance and mass spectra of the latter allowed its structure to be determined and confirmed the assigned structure of anticapsin.