[CH3:1][C:2]1[N:7]2[C:8](=[O:15])[C:9]([C:12]([OH:14])=O)=[CH:10][N:11]=[C:6]2[CH:5]=[CH:4][CH:3]=1.[CH2:16]([N:18](CC)[CH2:19][CH3:20])[CH3:17].ClC(OC)=O.N1CCCC1>C(Cl)(Cl)Cl>[CH3:1][C:2]1[N:7]2[C:8](=[O:15])[C:9]([C:12]([N:18]3[CH2:19][CH2:20][CH2:17][CH2:16]3)=[O:14])=[CH:10][N:11]=[C:6]2[CH:5]=[CH:4][CH:3]=1
A mixture containing 20.4 g (0.1 mol) of 6-methyl-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid and 15.5 ml (0.11 mol) of triethylamine in 600 ml of chloroform is cooled below -10° C. by ice-salt. A solution of 10 ml (0.1 mol) of methyl chloroformate dissolved in 50 ml of chloroform is dropped to the above mixture at -10° C. during 30 to 35 minutes. After stirring for 20 minutes, 9 g (0.11 mol) of pyrrolidine dissolved in 100 ml of chloroform are dropped to the above solution at a temperature between -5° C. and -8° C. during 1 hour. The reaction mixture is stirred at the same temperature for 1 hour, then allowed to stand overnight under cooling by ice. For working up, the reaction mixture is washed 3 times with 400 ml of 5% sodium hydrogen carbonate solution each, then 3 times with 400 ml of water each. The organic phase is dried over anhydrous sodium sulfate, filtered and evaporated. After suspending the oily residue in petroleum ether, 8.3 g (32.3%) of the named compound are obtained, which forms yellow crystals after recrystallization from ethanol, m.p.: 132°-134° C.
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