containing a thiomalonamide moiety was developed. Isothiocyanate derivatives of amino acids react smoothly with 2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione (Meldrum'sacid) to yield new thiocarbamoyl derivatives of Meldrum'sacids. Thermal decomposition of these new derivatives leads to thiocarbamoyl ketenes, which acylate amino acid esters to give pseudo‐tripeptides.