<jats:title>Abstract</jats:title><jats:p>The constitution of Chlamydocin – a metabolite of <jats:italic>Diheterospora chlamydosporia</jats:italic> with pronounced cytostatic activity – is proposed on the basis of chemical reactions and physical data. The synthesis of a derivative of a new amino acid is described. The biological activities of this compound and of derivatives of Chlamydocin are discussed.