A solution of 0.5 g (1.5 mmol) of bis-(1-naphthylmethyl)-acetic acid, 0.77 g (3.0 mmol) of histidine ethyl ester dihydrochloride (His-OEt·2 HCl), and 0.22 g (1.6 mmol) of 1-hydroxybenzotriazole (HOBt) in 20 mL of THF was treated with 0.85 mL (6.0 mmol) of Et3N followed by 0.33 g (1.6 mmol) of N,N'-dicyclo hexylcarbodiimide (DCC) and the solution allowed to stir at room temperature overnight. The mixture was filtered and the solvent removed under reduced pressure. The residue was taken up in EtOAc and washed with a saturated solution of NaHCO3, then with a saturated solution of NaCl. Drying over MgSO4 and removal of the solvent under reduced pressure gave the crude product. Chromatography on silica gel, eluting with a gradient of methylene chloride (CH2Cl2) to CH2Cl2 /MeOH (96/4) gave 0.15 g of the product as a white foam. The structure was confirmed by NMR and mass spectroscopy; (m+H)+ =506.
