8-Methoxy-4 -quinoline-2-carboxylic

K17. Kotake, Y., and Kato, M., Xanthurenic acid, XVI. Action of 4-hydroxy-8-methoxy-quinoline-2-carboxylic acid as the inhibiting agent with regard to the diabetogenic property of xanthurenic acid. Proc. Japan Acad. 32, 210-213 (1956). 

Figure 3. Biotransformation cascade of oxolinic acid in fish. A, oxolinic acid B., Glucuronide of oxolinic acid C., 7-hydroxy-6-methoxy derivative (1-ethyl-1,4 dihydro-7-hydroxy-6-methoxy-4-oxo-3-quinoline carboxylic acid) D., 6-hydroxy-7-methoxy derivative (1 -ethyl-1,4-dihydro-6-hydroxy-7-methoxy-4-oxo-3-quinoline-carboxylic acid. E,F. Stars represent unconfirmed sites of glucuronidation of 7-hydroxy-6-methoxy and 6-hydroxy-7-methoxy oxolinic acid derivatives.

Quinolobactin, 8-hydroxy-4-methoxy-2-quinoline carboxylic acid, is an alkaloid produced by Pseudomonas fluorescens ATCC17400. The biosynthesis of quinolobactin involves the tryptophan-kynurenine-xanthurenic acid pathway (Figure 6.13). 

Under acidic conditions, the formation of a nearly 1 1 mixture of 5- and 7-substituted quinoline-3-carboxylates, with a slight excess of the former, was observed from the 3-chloro- and 3-methyl derivatives. The cycliza-tions of 3-nitro, 3-trifluoromethyl, and methoxy derivatives were carried out only in polyphosphate to give mainly the 7-substituted isomers. 

Interestingly, when carboxylate derivatives are considered, the SET process is irreversible (due to release of CO ) and the degradation rate is maximum when this mechanism is supposed to be operating. On the contrary, when a radical cation or a semiquinone intermediate is invoked, as in the case of quinoline or hydroxy-methoxy-chloro benzenes [60,64], the rate is minimum due to the back reaction. 

Ethyl 6-hydroxy-l-oxo-l//-pyrimido[l,2-a]quinoline-2-carboxylate was prepared from the 2-carboxylic acid in boiling ethanol in the presence of 3% hydrogen chloride for 4 h (77GEP2628751,77USP4031217). Heating ethyl 6-methoxy-l-oxo-l//-pyrimido[l,2-a]quinoline-2-carboxylate in ethylene glycol in the presence of triethylamine for 6 h yielded the 2-hydroxyethyl ester (75GEP2513930). 

Isomerization of benzo[/]-l,5-diazabicyclo[3,2,2]nonene in 8.8 N HBr at 140°C yielded l,2,3,5,6,7-hexahydropyrido[l,2,3-de]quinoxaline (83 KGS677). Photolysis of dimethyl l-(quinolin-8-yl)-l,2,3-triazole-4,5-di-carboxylates in MeCN resulted in stable an/tydro-2,3-dimethoxycarbonyl-3//-pyrido[l,2,3-de]quinoxalin-4-ium hydroxides [87JCS(P1)403]. 6-Hy-droxymethyl-2-methyl-7-methoxy-l,2,3,4-tetrahydro-6//-pyrazino-[1,2-h]isoquinolin-4-one (138) was prepared from 5- [A-methyl-Ar-(ethoxy-... 

Homologs of pyridine, quinoline, thiophen, and various other heterocycles can be oxidized to carboxylic acids generally without destruction of the hetero ring in the pyrrole series, however, this cannot be done directly but requires intervention of an intermediate (see Fischer et al.A05). More circuitous routes are also sometimes preferable in the quinoline series for instance, in their total synthesis of hydroquinine Rabe et a/.406 obtained the 4-carboxylic acid from 6-methoxy-4-methylquinoline by oxidizing the 4-styryl derivative (obtained by reaction with benzaldehyde) instead of oxidizing the methyl compound directly. Alkyl groups at positions 2 and 4 of pyridine are more easily oxidized than those at position 3. 

Fused pyrimidine-2 carboxylic acids Thienopyrimidines (22,74) and pyrimidoquinoxalines (75). both of which are related to our pyrimido-[4,5-b]quinoline-2-carboxylic acid esters (XXXV and XLIII), were recently reported in the patent literature by Mead Johnson and Mitsubishi, respectively. The most potent compound in the thienopyrimidine series is XCVIII which has an oral ED50 of 3.1 mg/kg (Z3), while ethyl 7,8-di-methoxy-3,4-dihydro-4-oxopyrimido[5,6-b]quinoxaline-2-carboxylate (XCIX) appears to be about equipotent (25) with our compound XXXV. 

Dehydroquinic acid, shikimic acid, and chorismic acid are carboxylated compounds containing a six-membered carbocyclic ring with one or two double bonds (Fig. 143). The secondary products derived from these substances either still contain the ring and the C -side chain of the acids (see the structure of the benzoic acid derivatives, of anthranilic and 3-hydroxyanthranilic esters, D 8, D 8.2, D 8.4 and D 8.4.1) or have additional rings (see the formulae of naphthoquinones and anthraquinones, D 8.1, of quinoline, acridine, and benzodiazepine alkaloids, D 8.3.2). The carbon skeletons may be substituted by isoprenoid side chains (see the structure of ubiquinones, D 8.3) and may carry different functional groups, e.g., hydroxy, carboxy, methoxy, and amino groups. 

Iodine-catalyzed and solvent-controlled selective method for the synthesis of iodopyrano[4,3-6]quinolines and o-alkynyl esters from o-alkynyl aldehydes in mild reaction conditions is developed for the first time by Verma et al. This novel oxidative esterification provides a powerful tool for the preparation of a wide range of functionalized pyranoquinolinones as well as isocoumarins, and it is applicable for a variety of functional groups including primary alcohol, carboxyl, and methoxy groups. 

Oa-Methoxy-1 -methyl-dihydrolysergol 5-bromonicotinate 5-Bromopyridine-3-carboxylate of [(6aR, 9R, 10aS)-10a-methoxy-4,7-dimethyl-4,6,6a, 7,8,9,10, lOa-octahydro-indolo- [4, 3-fg] quinoline-9-yl]methyl... 

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