Pyridine-4-carboxylate, degradation

Hydroxylation is also involved in the degradation of all the pyridine carboxylates and the interrelations of these pathways are shown (Fignre 10.11) ... 

Chloro-2-hydroxypyridine-3-carboxylate is a terminal metabolite in the degradation of 3-chloroquinoline-8-carboxylate, but can be degraded by Mycobacterium sp. strain BA to chlorofumarate by reactions analogous to those described above for pyridine carboxylates (Figure 10.18) (Tibbies et al. 1989a). 

Hofmaim degradations were carried out on 5pyridine carboxylic acids are treated with sodium azide in an oleum medium, a good yield (69%) of 3-aminopyridine and poorer yields (<30%) of 2- and 4-aminopyridine are realized. 3-Amino-5-nitropyridine is similarly prepared by the Schmidt reaction using 5-nitronicotinic and hydrazoic acid. ... 

The nature of the base, CmHijN, varies. When produced from pure Mupinine, m.p. 68-9°, it furnishes on oxidation only 3-methylpyridine-2-carboxylic acid (XV) and pyridine-2 3-dicarboxylic acid. If, however, lupinine, m.p. 63-3°, is used, the resulting pyridine base on oxidation furnishes in addition 2-n-butylpyridine-6-carboxylic acid (XVI) and 6-methylpyridine-2-carboxylic acid (XVII). The conclusion is drawn that lupinine, m.p. 63-3°, is a mixture of 1-lupinine (XI) with aZlolupinine (XII), each of these components furnishing its own lupinane (XIII and XIV), and that these two lupinanes contribute to the final degradation product, the tertiary pyridine base, CioHuN, the two isomerides 2-w-Ijutyl-3-inethylpyridine (XVIII) and 2-w-butyl-6-raethylpyridine (XIX) respectively. These interrelationships are shown by the following scheme —... 

The photodegradation of the contact herbicide paraquat yielded many degradation products, but the major pathway produced l,2,3,4-tetrahydro-l-ketopyrido[l,2-fl]-5-pyrazinium that was further degraded to pyridine-2-carboxamide and pyridine-2-carboxylate (Figure 1.11) (Smith and Grove 1969). 

The degradation of pyridine-4-carboxylate by Mycobacterium sp. strain INAl takes place by successive hydroxylations before reduction and ring fission (Kretzer and Andreesen 1991) (Figure 10.10). 

FIGURE 10.11 Interaction of pathways for degradation of pyridine-2-carboxylate, pyridine-3-carboxylate, and nicotine. (From Neilson, A.H. and Allard, A.-S., The Handbook of Environmental Chemistry, Springer, Heidelberg, 1998. With permission.)... 

As for the aerobic degradation of pyridines, hydroxylation of the heterocyclic ring is a key reaction in the anaerobic degradation of azaarenes by Clostridia. Whereas in Clostridium barkeri, the end products are carboxylic acids, CO2, and ammonium, the anaerobic sulfate-reducing Desulfococcus niacinii degraded nicotinate completely to CO2 (Imhoff-Stuckle and Pfennig 1983), although the details of the pathway remain incompletely resolved. 

A number of syntheses of substituted 2,3 -bipyridines are worthy of note. Tetracyclone heated at 215°C with nicotinonitrile affords 3,4,5,6-tetraphenyl-2,3 -bipyridine, whereas 3,4-di(2-pyridyl)pyridine is obtained by an oxidative degradation of the corresponding 6,7-disubstituted thiazolo[3,2-a]-pyridinium salt. Nicotinic acid on UV irradiation in aqueous solution at pH 4-6 gives 2,3 -bipyridine-5-carboxylic acid, whereas irradiation of picolinic acid in the same pH range in the absence of metal ions gives some 2,3 -bipyridine. 6,6 -Diphenyl-2,3 -bipyridine is thought to be formed from... 

Methyl-3,3 -bipyridine has been oxidized by permanganate to 3,3 -bi-pyridine-4-carboxylic acid. " 3,3 -Bipyridine carboxylic acids are easily decarboxylated and have been esterified and converted to amides, hydrazides, and acylazides. The Hofmann degradation, of the diamide of 3,3 -bipyridine-2,2 -dicarboxylic acid affords the expected 2,2 -diamino-3,3 -bipyridine, but some of the tricyclic system 108 is formed as well. A 2,2 -bis(acylazide) is converted to a similar tricyclic system with ethanol via the intermediate isocyanate, and several related reactions have been described. The simultaneous dehydration... 

When an alkyl acetylaroylacetate reacts with phosphorus penta-sulfide in pyridine, a complex reaction occurs, involving sulfuration, degradation, and condensation, that leads to an alkyl 2,5-diaryl-l,6,6a lv-trithiapentalene-3-carboxylate in moderate yields (Eq. 22).45... 

Apart from hydrogen evolution, the electrons of reduced ferredoxin can take alternative routes leading to biosynthesis. In anaerobic bacteria, reduced ferredoxin can be used directly for the reduction of pyridine nucleotides (Tagawa and Arnon (99) Valentine, Brill and Wolfe (107) Fredericks and Stadtman (44)) for the reduction of hydroxyla-mine to ammonia (Valentine, Mortenson, Mower, Jackson, and Wolfe (109) for COa fixation in the reductive carboxylation of acetyl-CoA to pyruvate (Bachofen, Buchanan, and Arnon (13) Raeburn and Rabino-witz (83) Andrews and Morris (3) Stern (98)) for the reduction of sulfite to sulfide (Akagi (1)) and, in the presence of ATP, it can be used for the reduction of N2 to NH3 (Mortenson (72,73) D Eustachio and Hardy (40)). The role of ferredoxin in these reactions as well as in the oxidative degradative reactions discussed above is summarized in Fig. 10. 

Cellulose esters of halogenated acids are exceptionally difficult to prepare. This is particularly true if the halogen is in the alpha position to the carboxyl group. Chloroacetic anhydride in the presence of acid catalysts esterifies cellulose only after severe degradation. The use of pyridine is prohibited because of side reactions with the reagent. Mixed... 

The final structural proof for guatterine (XVIII) rests upon its conversion by chromium trioxide in pyridine into the alkaloid athero-spermidine (XXI) which was also found in G. psilopus and whose structure was established by its oxidative degradation to 1-azaanthra-quinone-4-carboxylic acid (XXII). It is interesting to note that the relative stereochemistry of the C-7 hydroxyl group in guatterine is opposite to that of the hydroxyl in ushinsunine (XXIII) where the Jea,7 value is only 2.5 cps. The absolute configuration of guatterine has not yet been established. 

The problem was resolved essentially by stepwise degradation of the molecule to furan-3-carboxylic acid, pyridine-2,5-dicarboxylic acid (V), nupharidinic acid (XVIII), and anhydronupharanediol, C15H30O (XV), with the structure of the last-named supplying the key to that of deoxynupharidine (15, 16). Chart I show s the main steps of the degradation. 

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