To a suspension of N-Boc-trans-4-fluoro-L-proline (4.5 g, 19.29 mmol) in CH2Cl2 (68 mL) were added DCC (4.78 g, 23.15 mmol), DMAP (0.236 g, 1.93 mmol) and benzyl alcohol (2 mL, 19.29 mmol). The resulting white suspension was stirred at RT for 48 h and filtered. The filtrate was concentrated to give a colorless oil which was purified by flash column chromatography on silica gel (c-hexane to c-hexane/EtOAc 4-1) to give the desired compound. TLC, Rf (c-hexane/EtOAc 3:1)=0.3; MS: 346.0 [M+Na]+; tR (HPLC conditions a): 3.85 min.
