To a stirred solution of (2S,4S)-2-amino-N-{4-[(4-amino-benzenesulfonyl)-isobutyl-amino]-5-hydroxy-pentyl}-3-naphthalen-1-yl-propionamide (product of example 8) (0.023 g, 0.044 mmol) in DMF (0.7 mL) was added triethylamine (12.0 μL, 0.087 mmol) and methyl bromoacetate (4.0 μL, 0.054 mmol). The mixture was stirred to room temperature for 1 h. Ethyl acetate was added and the organic layer was washed with a saturated solution of NaHCO3, then dried with MgSO4 and concentrated. The residue was purified by flash chromatography eluting with a mixture of hexane/EtOAc. The yield obtained was 47%.
