A solution of 3-{(1S)-1-(t-butoxycarbonylamino)-2-methyl-propyl}-5-phenoxymethyl-4,5-dihydro-isoxazole-5-carboxylic acid ethyl ester (2.00 g, 4.76 mmol) in dry CH2Cl2 (10 mL) at 0° C. under N2 was treated with TFA (6 mL) and stirred for 1.5 h. After removal of volatiles, the residue was taken up with ethyl acetate (200 mL), washed with sat'd NaHCO3(100 mL×2), dried (anh Na2SO4), filtered and concentrated. To a solution of the crude product, EDC (1.09 g, 1.2 eq), 2-naphthoic acid (983 mg, 1.2 eq) and HOBt (771 mg, 1.2 eq) in DMF (20 mL) at 0° C. was added triethylamine (663 uL, 1.0 eq). The reaction was stirred overnight at room temperature. After removal of volailes in vacuo, the residue was taken up with ethyl acetate (250 mL), washed with water(100 mL), sat'd NaHCO3 (100 mL×2), dried (anh Na2SO4), filtered and concentrated. Flash chromatography with 25-33% ethyl acetate/hexanes gave 2.04 g (90%) of the title compound.
