[OH:1][C:2]1C(=O)N2C(C3(CCCC3)OCC2)=N[C:3]=1[C:17]([O:19][CH2:20][CH3:21])=[O:18].[CH2:22](O)CO>C1C=CC=CC=1.CCOCC.CC1C=CC(S(O)(=O)=O)=CC=1.O>[O:18]1[C:17]2([CH2:3][CH2:2][O:1][CH2:22]2)[O:19][CH2:20][CH2:21]1A mixture of ethyl 3′-hydroxy-4′-oxo-6′,7′-dihydro-4′H-spiro[cyclopentane-1,9′-pyrimido[2,1-c][1,4]oxazine]-2′-carboxylate (15.79 g, 183.5 mmol), ethylene glycol (16.7 mL, 300 mmol) and cat. TsOH.H2O (100 mg) in benzene (100 mL) was heated at reflux using Dean-Stark trap. After 17 h, the reaction mixture was cooled, diluted with ether (150 mL), washed with sat. Na2CO3 and brine (50 mL each), dried (Na2SO4), filtered and concentrated to give yellow liquid. Distillation under reduced pressure afforded the title compound as a yellow liquid (19.13 g, 80%). 1H NMR (500 MHz, CDCl3) δ: 3.9.4 (2H, t, J=7.0 Hz), 3.94-3.90 (4H, m), 3.68 (2H, s), 2.09 (2H, t, J=7.0 Hz).
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