5-ethyl-8-oxo-2,3,5,8-tetrahydrofuro<3,2-b><1,8>naphthyridine-7-carboxylic acid

ethyl 6-ethoxy-1-ethyl-7-(2-hydroxy-3,3,3-trichloropropyl)-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylate

5-ethyl-8-oxo-5,8-dihydrofuro<3,2-b><1,8>naphthyridine-2,7-dicarboxylic acid

triethyl 5-ethyl-3-hydroxy-8-oxo-2,3,5,8-tetrahydrofuro<3,2-b><1,8>naphthyridine-2,2,7-tricarboxylate

3-(6-ethoxy-3-ethoxycarbonyl-1-ethyl-4-oxo-1,4-dihydro-1,8-naphthyridin-7-yl)acrylic acid

ethyl 6-ethoxy-4-hydroxy-7-(2-hydroxy-3,3,3-trichloropropyl)-1,8-naphthyridine-3-carboxylate

5-nitro-2,3-dihydrofuro<3,2-b>pyridine

5-amino-2,3-dihydrofuro<3,2-b>pyridine

diethyl (2,3-dihydrofuro<3,2-b>pyridin-5-yl)aminomethylenemalonate

6-benzyloxy-7-(2,2-diethoxyethyl)-1-ethyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid

ethyl 7-(2-bromovinyl)-1-ethyl-6-hydroxy-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylate

ethyl 5-ethyl-8-oxo-5,8-dihydrofuro<3,2-b><1,8>naphthyridine-7-carboxylate

ethyl 2,3-dibromo-3-(6-ethoxy-3-ethoxycarbonyl-1-ethyl-4-oxo-1,4-dihydro-1,8-naphthyridin-7-yl)propionate

3-(6-ethoxy-3-ethoxycarbonyl-4-hydroxy-1,8-naphthyridin-7-yl)acrylic acid

ethyl 5-ethyl-8-oxo-2,3,5,8-tetrahydrofuro<3,2-b><1,8>naphthyridine-7-carboxylate

ethyl 7-(2-bromovinyl)-6-ethoxy-1-ethyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylate