A solution of (S)-2-((benzyloxy)carbonyl)amino)-8-(tert-butoxy)-8-oxooctanoic acid (prepared as described in WO2006/061638), EDC.HCl (1.3 eq.), HOBt (1.3 eq.) in DMF (0.3 M) was stirred at room temperature for 10 min. Then F2 and DIPEA (3.0 eq.) were added and the resulting mixture was stirred at room temperature for 1 h 30 min. The reaction mixture was diluted with EtOAc, washed with sat. aq. NaHCO3 sol., brine, dried (Na2SO4), filtered and concentrated under reduced pressure to give a crude that was purified by column chromatography (eluent: Petroleum ether/EtOAc from 97:3 to 3:7) to give the title compound as yellow oil. MS (ES+) C32H39N3O7: 578 (M+H)+.
