Synthesis and characterization of a series of novel glutamic γ-15N-anilide dipeptides

The preparation of a series of novel Cbz-Gln-Gly dipeptide derivatives is reported, wherein the gamma-carboxamide groups of the glutamine side chains have been modified to gamma-N-15-anilides which are substituted in the para position with -NO2, -Cl, -H, -CH3, -OCH3, and -N(CH3)(2). Characterization of the free anilines (pK(a) values and N-15 NMR chemical shifts) and corresponding gamma-anilides (N-15 NMR chemical shifts and FTIR wavenumbers) is also reported. Correlation of these physicochemical data to Hammett substituent parameters (sigma(para)) is discussed. These novel dipeptide derivatives should prove to be generally useful for structure-function enzymology studies of gamma-glutamyl transferring enzymes.