[CH3:1][N:2]1[C:7](=O)[CH2:6][O:5][C:4]2[CH:9]=[CH:10][CH:11]=[C:12]([O:13][CH2:14][C:15]([O:17][CH2:18][CH3:19])=[O:16])[C:3]1=2>C1COCC1.CO>[CH3:1][N:2]1[CH2:7][CH2:6][O:5][C:4]2[CH:9]=[CH:10][CH:11]=[C:12]([O:13][CH2:14][C:15]([O:17][CH2:18][CH3:19])=[O:16])[C:3]1=2A solution of ethyl 2-((4-methyl-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-5-yl)oxy)acetate (100 mg, 0.377 mmol) in anhydrous THF (3 mL) was cooled to 0° C. and BH3-Me2S (0.1 mL) added. The solution was stirred at 27° C. for 6 h, diluted with methanol and concentrated. The residue was partitioned between ethyl acetate (30 mL) and water (20 mL), the organic layer washed with brine, dried over sodium sulfate, filtered and concentrated. The crude product was purified by preparative TLC. (72 mg, yield 76%) MS (ESI+) e/z: 252.2 [M+1]+. 1H NMR (CDCl3, 400 MHz), δ ppm: 6.87-6.76 (m, 1H), 6.62-6.52 (m, 1H), 6.40-6.28 (m, 1H), 4.70 (s, 2H), 4.34-4.22 (m, 2H), 4.18-4.06 (m, 2H), 3.21-3.07 (m, 2H), 2.99-2.85 (m, 3H), 1.33-1.25 (m, 3H).
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