Studies on the determination of the sequence of amino acids in peptides and proteins. 3. The synthesis of 3-(4′-dimethylamino-3′:5′-dinitrophenyl)hydantoin derivatives of various amino acids, and their use for the determination of N-terminal amino acids

Publisher Website
Google Scholar
Abstract
A red-colored isocyanate the 4-dimethyl-amino-3,5-dinitrophenyl isocyanate (DDPI) was synthesized. This isocyanate reacts quantitatively with the free amino groups of amino acids or peptides dissolved in water-dioxan at the apparent pH 9.6 at 0[degree], giving deep-orange colored carbamyl derivatives (DDP-ureidoamino acids or DDP-ureido peptides, for example, DDP-ureido glycine). DDP-ureidoamino acids when refluxed for 2 hrs. in 2[image]HCl, or when treated for several days at 40[degree] with nitromethane saturated with HCl, give by ring closure and elimination of water the corresponding hydantoins (amino acid-DDP-hydantoins, for example glycine -DDP-hydantoin) in quantitative yields. When DDP-ureido peptides are treated in the same way, the N-terminal amino acid carrying the DDP radical splits up, forming by ring closure the corresponding hydantoin which can be recovered in quantitative yields. The amino acid-DDP-hydantoins are deep-orange colored substances which crystallize well and have sharp melting points. They can be adsorbed on alumina columns, and their mixtures can be conveniently resolved by adsorption chromatography. The scope for the use of these derivatives for the detn. of N-terminal amino acids in peptides is discussed.