A study on the stability of diphenylindenonesulphonyl derivatives of amino acids to acid hydrolyses.

The stability of the diphenylindenonesulphonyl (disyl) derivatives of tryptophan, proline, hydroxyproline, histidine, serine, threonine and aspartic acid, as well as of glycine, alanine, alpha-amino butyric acid, phenylalanine, valine, leucine and isoleucine to acid hydrolysis is studied. The results indicate that the disyl derivatives are much more stable in comparison with the corresponding DNP- and DNS-derivatives. Hence, the dysil-chloride method possesses definite advantages over these widely used methods for determination of N-terminal groups, not only because of its higher sensitivity, but also because of the higher stability of the disyl derivatives of amino acids to acid hydrolysis.