Combine N-t-butoxycarbonyl-N-(2-oxo-ethyl)-2-phenyl-ethylamine (5.10 g, 19.16 mmol) and (S)-2-(1H-indol-3-yl)-1-carboxymethyl-ethylamine hydrochloride salt ((S)-tryptophan methyl ester hydrochloride salt) (4.90 g, 19.23 mmol) in methanol (50 mL) and stir for 10 minutes. Add sodium cyanoborohydride in solution (19.0 mL, 1M in THF, 19.0 mmol) and stir under an inert atmosphere for 18 hours. Concentrate in vacuo to obtain a residue. Dilute the residue with ethyl acetate and extract with water. Separate the layers, dry the organic layer over MgSO4, filter, and evaporate in vacuo. Chromatograph on silica gel eluting with 50% ethyl acetate/hexane to give the title compound.
