Studies on the formation and stability of isoindoles derived from amino acids, o-phthalaldehyde and N-acetyl-L-cysteine.

A kinetic-spectrophotometric study is performed on the formation and degradation of the isoindole derivatives of amino acids with o-phthalaldehyde and N-acetyl-L-cysteine. The experimental and structural factors which affect the formation and stability of the compounds are considered, and the results are compared with those obtained for mercaptoethanol. N-Acetyl-L-cysteine derivatives are highly stable, not requiring a strict control of the time of reaction as in the case of mercaptoethanol.