The reaction of taurin with α-naphthylisocyanate

Abstract

Although taurin differs from that particular group of amino acids which constitute the building stones of the proteins in that it contains a sulphonic instead of a carboxyl group, it nevertheless closely resembles the amino acids in its chemical properties. Like the amino acids taurin can be quantitatively estimated when in pure solution either by treating it with HNO₂ and determining the nitrogen set free or by titration with alkali in the presence of formalin. It possesses amphoteric properties 1 and reacts with many of the amino acid reagents. Thus Paal and Zitelmann 2 found that taurin reacts with phenylisocyanate to give α-phenyl-ureidoethylsulphonic acid, Gabriel 3 and his associates prepared benzoyl- and phthalyl-taurin, and Bergell 1 has attempted to use β-naphthalinsulphotaurin as a means of estimating taurin in urine.

We have found that taurin like the carboxy amino acids 2 reacts with α-naphthylisocyanate to yield the corresponding hydantoic acid. The barium salt of a-naphthylureidoethyl sulphonic acid was prepared by adding to a concentrated solution of taurin which contained an equivalent amount of KOH, 1¼ equivalents of a-naphthylisocyanate and the mixture was shaken at frequent intervals for an hour. The insoluble dinaphthyl urea was filtered off and on acidifying with HC1 the solution thickened but the free hydantoic acid did not separate. On addition of BaC1₂ solution the barium salt of the hydantoic acid was precipitated. This was washed with small quantities of ice water and then with alcohol and was dried to constant weight. Estimations of C, H, and Ba gave (per gram of substance) the following results.