Abstract
A deep-orange isothiocyanate, 4-dimethylamino-3;5-dinitrophenvlisothiocyanate (DDPT) was synthesized. This isothiocyanate reacts with amino acids or peptides dissolved in water: acetone (1:3, vol./vol.) at the apparent pH 8-9, giving orange thiocarbamyl derivatives (DDP-thioureidoamino acids or DDP-thioureido-peptides)in practically quantitative yields. By the treatment of the DDP-thioureidoamino acids with glacial acetic acid (in the case of DDP-thioureidoglycine) or with water: acetic acid (in the case of other DDP-thioureidoamino acids ) the corresponding substituted 2-thiohydantoins (briefly called amino acid-DDP-thiohydantoins ) are formed in good yields(80-90%). By treatment of DDP-thioureidopeptides with water: acetic acid, the N-terminal amino acid residue splits off as an amino acid-DDP-thiohydantoin which can be isolated in a pure state by adsorption chromatography; the residual peptide can be treated with DDPT and the process repeated to determine the sequence of amino acids in the peptide. As an example the sequence detn. on alanylglycylglycine is descr. The amino acid-DDP-thiohy-dantoins can be hydrolyzed to the parent amino acids and these can be identified by paper chromatography.