反应详情

A suspension of 3-phenyl-4-(trifluoromethyl)isoxazole-5-carbonyl fluoride (2.91 g, 11.2 mmol), (Z)-tert-butyl 1-(4-(N′-hydroxycarbamimidoyl)benzyl)azetidine-3-carboxylate (Int.1, 3.43 g, 11.2 mmol), and Hunig's Base (2.55 mL, 14.6 mmol) in acetonitrile (20 mL) was stirred at room temperature over the weekend. The reaction mixture had completely solidified (pinkish-tan in color), but was judged complete by HPLC and LCMS. The reaction mixture was partitioned between a saturated aqueous of sodium bicarbonate (150 mL) and dichloromethane (150 mL). The aqueous layer was extracted with dichloromethane (2×100 mL), and the combined organic layers were dried over anhydrous sodium sulfate. Concentration under reduced pressure afforded a tan solid which was purified by flash silica gel chromatography using a mixture of ethyl acetate in hexane (0-50%) to afford tert-butyl 1-(4-(5-(3-phenyl-4-(trifluoromethyl) isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)benzyl)azetidine-3-carboxylate (4.60 g; 78%) as a white, crystalline solid. The material was suspended in methanol (−75 mL) and was sonicated for 5 minutes. The MeOH was removed under reduce pressure, and the residue was re-suspended in methanol (−50 mL) with sonication. Vacuum filtration and drying afforded tert-butyl 1-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)benzyl)azetidine-3-carboxylate (4.04 g, 7.67 mmol, 68% yield) as a white, crystalline solid. The methanol filtrate was concentrated to afford additional tert-butyl 1-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)benzyl)azetidine-3-carboxylate (570 mg; 10%) as a slightly off-white solid. The compound had an HPLC retention time=3.12 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=527.1. 1H NMR (500 MHz, CDCl3) δ ppm 1.47 (s, 9H) 3.28-3.37 (m, 3H), 3.60 (br. s., 2H), 3.74 (br. s., 2H), 7.49 (d, J=7.70 Hz, 2H), 7.53-7.62 (m, 3H), 7.69 (d, J=7.15 Hz, 2H), and 8.16 (d, J=7.70 Hz, 2H).

1. customThe reaction mixture was partitioned between a saturated aqueous of sodium bicarbonate (150 mL) and dichloromethane (150 mL)
2. extractionThe aqueous layer was extracted with dichloromethane (2×100 mL)
3. dry with materialthe combined organic layers were dried over anhydrous sodium sulfate
4. concentrationConcentration under reduced pressure
5. customafforded a tan solid which
6. customwas purified by flash silica gel chromatography
7. additiona mixture of ethyl acetate in hexane (0-50%)