反应详情

温度

100 °C

5.0 g of triethyl 5-ethyl-3-hydroxy-8-oxo-2,3,5,8-tetrahydrofuro[3,2-b]-1,8-naphthyridine-2,2,7-tricarboxylate was added to 80 ml of 20% sulfuric acid and stirred at 100° C. for 2 hours. After allowing it to cool, the reaction solution was poured into ice water. The precipitated crystals were collected by filtration and recrystallized from dimethylformamide to obtain 2.61 g of 5,8-dihydro-5-ethyl-8-oxofuro-[3,2-b]-1,8-naphthyridine-2,7-dicarboxylic acid (Compound X where R1 =C2H5), m.p. >300° C.

1. temperatureto cool
2. filtrationThe precipitated crystals were collected by filtration
3. customrecrystallized from dimethylformamide