The first chemicalconversion of C-glycine in dipeptides into taurine has been achieved using a general substitution of a sulpho group for a halogeno or mesyl group via the corresponding amino acid 2-halogenoethyl-or 2-methanesulphonyloxyethyl-amides, each of which was prepared from the ethanolamide obtained by LiBH4 reduction of a protected dipeptide containing a C-glycine ester.
The physicochemical and immunochemical properties of fourteen taurine dipeptides (1-14) containing one of eleven neutral L-amino acids or three neutral D-amino acids were examined. These taurine peptides were synthesized by a conventional method using chemical coupling of taurine with an amino acid. Alternatively, the dipeptides (1-9) containing L-amino acid were also synthesized, with a few exceptions (10, 11), by a new method using a general substitution reaction of a sulfo group for chlorine or bromine via the β-halogenoethyl amide of each amino acid. When sodium sulfite or ammonium sulfite was used in the substitution, the new method gave pure taurine dipeptides in good yield without racemization. All the dipeptides (1-14), including naturally occurring Ser-Tau, showed high cross-reactivities with antisera against haptenic taurine or γGlu-Tau.
Although taurine-dipeptides containing an acidic α-amino acid (Glu or Asp) have been proposed to exist in the central nervous system, it is not yet clear how the acidic amino acid is linked with taurine in the peptides. This study aimed to analyze the mode of linkage of such peptides through analysis of their spectral data, such as proton nuclear magnetic resonance and mass spectra. Four pairs of taurine-oligopeptides (1-8) containing one acidic α-amino acid were examined, and spattered ion mass spectrometry B/E linked scan mass spectrometry was proved to be most useful to distinguish each pair of isomers. Further, immunochemical examination indiated that all the oligopeptides (1-8) synthesized by the conventional coupling method were highly cross-reactive with antisera against taurine and against γGlu-Tau.