To a solution of compound 19 (0.042 mmol), HATU (16 mg, 0.042 mmol), HOAT (5.71 mg, 0.042 mmol) 1-fluorocyclopropane-1-carboxylic acid (4.3 mg, 0.042 mmol) in DMF (1 mL), DIPEA (25 µL, 0.141 mmol) was added. The reaction mixture was stirred at r.t. for 30 min. LC-MS analysis (acidic method) showed complete conversion of the starting material. Water (1 mL) was added and the resulting mixture was extracted with DCM (3 x 5 mL). After drying the organic phase over MgSO 4 and the solvent was removed under reduced pressure to afford the title compound (28.3 The trityl protected compound (0.04 mmol) was dissolved in 1.8 mL of DCM. TIPS (0.1 mL) and TFA (0.1 mL) were added, and the mixture was left to react at r.t. for 2 h. LC-MS analysis (acidic method) showed complete conversion of the starting material. Volatiles were removed and the crude was dissolved in MeOH, filtered and purified by preparative HPLC and freeze-dried to give pure deprotected compound as white solid (16 mg, 79% yield). ¹H 43.2, 36.9, 33.6, 28.9, 28.0, 25.8, 25.4, 24.4, 16.1, 14. Compound 21c (16.5 mg, 0.025 mmol, 1 eq.) was dissolved in a mixture of THF (1 mL) and water (0.25 mL). Then LiOH was added (1.2 mg, 0.0509 mmol, 2 eq.) and the mixture was stirred at r.t. for 2 h. LC-MS analysis (acidic method) showed complete conversion of the starting material. A solution of HCl 4N in dioxane was added to pH <6 and the mixture was evaporated to dryness to yield the deprotected carboxylic acid derivative (16.1 mg, yield: quantitative). Starting from the crude carboxylic acid (0.025 mmol, 1 eq.) and following the general method H, the desired compound was obtained (9.2 mg, yield: 39% [M+H] + : m/z = 933.3434; observed: m/z = 933.3263.