反应详情

Water (4 mL) was added dropwise to a stirred mixture of (R)-acetate 158 (427 mg, 1.67 mmol) and K2CO3 (256 mg, 1.85 mmol) in MeOH (36 mL). After stirring at room temperature for 4 h, the mixture was cooled in ice and treated with 0.1M HCl (37 mL, 3.70 mmol). The solvents were removed under reduced pressure and the residue was chromatographed on silica gel. Elution with 0-1% MeOH/CH2Cl2 firstly gave foreruns, and then further elution with 1-2.5% MeOH/CH2Cl2 gave [(7R)-7-methyl-2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazin-7-yl]methanol (159) (343 mg, 96%) as a pale yellow solid that was used directly in the next step; 1H NMR [(CD3)2SO] δ 8.03 (s, 1H), 5.23 (br t, J=5.4 Hz, 1H), 4.13 (dt, J=13.0, 6.0 Hz, 1H), 4.05 (ddd, J=12.9, 8.1, 5.6 Hz, 1H), 3.54 (dd, J=11.6, 4.9 Hz, 1H), 3.48 (dd, J=11.6, 5.2 Hz, 1H), 2.21 (ddd, J=14.4, 8.1, 5.9 Hz, 1H), 2.00 (dt, J=14.4, 5.8 Hz, 1H), 1.32 (s, 3H); [α]D27−16.0° (c 1.00, DMF).

1. temperaturethe mixture was cooled in ice
2. customThe solvents were removed under reduced pressure
3. customthe residue was chromatographed on silica gel
4. washElution with 0-1% MeOH/CH2Cl2 firstly gave foreruns
5. washfurther elution with 1-2.5% MeOH/CH2Cl2