Reaction Steps
To a solution of (R)-1-(tert-butyldimethylsilyl)-4-oxoazetidine-2-carboxylic acid (126 mg, 0.55 mmol) in THF (1.5 mL) was added to a solution of triphosgene (54 mg, 0.18 mmol). The reaction mixture was stirred for 5 min at rt, followed by addition of 2,4,6-trimethylpyridine (203 μL, 1.54 mmol), a solution of (R)-1-(3-fluoro-4-methoxyphenyl)-1-(3-fluoro-5-(1,1,2,2-tetrafluoroethoxy)phenyl)-2-phenylethanamine, prepared as described in Procedure 3, 62, 5 and 6, (50 mg, 0.11 mmol) in THF (0.6 mL), and N,N-diisopropylethylamine (268 μL, 1.54 mmol). The reaction mixture was stirred at room temperature for 40 min. Water (10 mL) was added and the reaction mixture was extracted with dichloromethane (3×15 mL) and the combined organic layers were washed with 2 N potassium carbonate and then sat. NaCl. The organic layers were dried over magnesium sulfate, filtered and concentrated under reduced pressure. The residue was purified by ISCO Flash chromatography (Analogix column 4.2 g, eluting with hexane/EtOAc) to yield (R)-1-(tert-Butyldimethylsilyl)-N-((R)-1-(3-fluoro-4-methoxyphenyl)-1-(3-fluoro-5-(1,1,2,2-tetrafluoroethoxy)phenyl)-2-phenylethyl)-4-oxoazetidine-2-carboxamide (Example 343, 41 mg, 55% yield). LCMS: RT=4.18 min [M+H] 667.1 (Phenominex, Luna C18, 4.6×50 mm, 10%-90% MeOH/H2O containing 0.1% TFA, flow rate 4 mL/min, 4 min gradient, monitoring at 220 nm); 1H NMR (500 MHz, CDCl3) δ ppm −0.04 (s, 3H), 0.24 (s, 3H), 0.91 (s, 9H), 2.79 (dd, J=15.4, 2.7 Hz, 1H), 3.32 (dd, J=15.4, 6.6 Hz, 1H), 3.79-3.85 (m, 1H), 3.86-3.90 (m, 2H), 3.91 (s, 3H), 5.87 (none, 2H), 6.59 (s, 1H), 6.64 (d, J=7.1 Hz, 2H), 6.75 (s, 1H), 6.80 (d, J=9.3 Hz, 1H), 6.87-6.94 (m, 4H), 7.15 (t, J=7.4 Hz, 2H), 7.20 (d, J=7.1 Hz, 1H).
