A slurry of 2-(benzotriazol-1-yl)-N-(benzyloxycarbonyl)glycine (1.1 equiv.; Katritzky, A. R. et al. J. Org. Chem. 1990, 55, 2206, incorporated herein by reference) in THF (0.3 M) was cooled to 0° C. and treated with oxalyl chloride (1.1 equiv.) in a dropwise manner. To the slurry was added dropwise DMF (0.1 equiv.); stirring was continued at 0° C. for 1 hour. A solution of 1-(2-aminophenyl)-1-butanone and N-methylmorpholine (2.2 equiv.) in THF (1 M in butanone), pre-cooled to 0° C., was added via cannula. Upon completion of the addition, the reaction was warmed to ambient temperature. The mixture was filtered, washing the filter cake with THF. The filtrate was transferred to a three-neck flask and treated with ammonia gas through a dispersion tube for 15 minutes. Methanol (0.3 M in butanone) was added and the ammonia continued to be bubbled through the solution for 1 hour. The reaction was concentrated, diluted with ethyl acetate, and re-concentrated; this was repeated again. The residue was diluted with ethyl acetate and washed twice with 1 N NaOH. The aqueous washes were back-extracted with ethyl acetate. The combined organics were washed with brine, dried over Na2SO4, filtered, and concentrated. Acetic acid was added and concentrated in vacuo. The syrup was dissolved in acetic acid (0.6 M in butanone) and treated with ammonium acetate (4.0 equiv.). The reaction was stirred at ambient temperature for 18 hours. The resultant solid was filtered, washing with H2O.
