Monosubstituted 2,2‐Dimethyl‐3‐Formyl‐L‐Thiazolidine‐4‐Carbonyl‐Insulins

The treatment of insulin in aqueous solution at pH 6.9 and 8.5, with the hydroxysuccinimide ester of 2,2‐dimethyl‐3‐formyl‐l‐thiazolidine‐4‐carboxylic acid leads to the incorporation of thiazolidine residues into the protein. Examination by DEAE‐Sephadex chromatography of the products formed shows the presence of three products. The relative amount of products formed depends upon the reaction conditions. Characterisation of these products by end‐group analysis, cellulose acetate electrophoresis, amino acid analysis of the performic acid‐oxidised chains and treatment with TPCK‐treated trypsin suggests that they are monosubstituted derivatives formed by reaction at each of the free amino groups of insulin. The effect of modification on the biological activity and crystallisation properties of the hormone is discussed as well as the application of the preparation of covalent heavy atom derivatives of proteins.