反应详情

The tert-butyl 1-(4-(5-(4-isobutyl-5-phenylisoxazol-3-yl)-1,2,4-oxadiazol-3-yl)benzyl)-azetidine-3-carboxylate intermediate was stirred in trifluoroacetic acid (3.64 mL, 47.2 mmol) for 30 min. and concentrated under reduced pressure to give the desired product as a pale yellow solid. The solid was dispersed in water with some methanol with sonication. The pH was adjusted to ˜4, and the resulting solid was collected by vacuum filtration, washed with water (3×), and dried. The white solid was triturated with methanol with sonication and filtered to give 1-(4-(5-(4-isobutyl-5-phenylisoxazol-3-yl)-1,2,4-oxadiazol-3-yl)benzyl)azetidine-3-carboxylic acid (0.074 g, 0.161 mmol, 34.2% yield) as a white, crystalline solid. The compound had an HPLC ret. time=2.99 min.−Column. CHROMOLITH® SpeedROD 4.6×50 mm (4 min.); Solvent A=10% MeOH, 90% H2O, 0.1% TFA; Solvent B=90% MeOH, 10% H2O, 0.1% TFA. LC/MS M+1=459.3. 1H NMR (500 MHz, DMSO-d6) δ ppm 0.87 (d, J=6.60 Hz, 6H), 1.93 (ddd, J=13.61, 6.74, 6.60 Hz, 1H), 2.99 (d, J=7.15 Hz, 2H), 3.24 (br. s., 3H), 3.43 (s, 2H), 3.66 (s, 2H), 7.53 (d, J=7.70 Hz, 2H), 7.58-7.67 (m, 3H), 7.87 (d, J=6.60 Hz, 2H), and 8.06 (d, 2H). The methanol filtrate was concentrated under reduce pressure to give additional 1-(4-(5-(4-isobutyl-5-phenylisoxazol-3-yl)-1,2,4-oxadiazol-3-yl)benzyl)azetidine-3-carboxylic acid (0.034 g, 0.066 mmol, 13.99% yield) as a pale yellow solid (HPLC purity=89%).

1. concentrationconcentrated under reduced pressure