Picolinic acid, 6-Hydroxy

Wu, K.J. Steding, A. Becker, C.H. Matrix-Assisted Laser Desorption-TOF-MS of Oligonucleotides Using 3-Hydroxy-picolinic Acid As an Ultraviolet-Sensitive Matrix. Rapid Commun. Mass Spectrom. 1993, 7,142-146. 

Photodecomposition products included acidic compounds and five methylated derivatives (Plimmer, 1970). When picloram in an aqueous solution (25 °C) was exposed by a high intensity monochromatic UV lamp, dechlorination occurred yielding 4-amino-3,5-dichloro-6-hydroxy-picolinic acid which underwent decarboxylation to give 4-amino-3,5-dichloropyridin-2-ol. In addition, decarboxylation of picloram yielded 2,3,5-trichloro-4-pyridylamine which may undergo dechlorination yielding 4-amino-3,5-dichloro-6-hydroxypicolinic acid (Burkhard and Guth, 1979). 

Oxalic acid (3 structures)/Carbonate/ Bipyridine (4 structures)/Picolinic acid/3-hydroxy-picolinic acid/2,4-pyridine dicarboxylic acid/3-acetatoxy-picolinic acid/5-nitro-phenanthroline 2 26 174-183... 

In aqueous solution pristinamycin 1 shows two acid-base equilibria (determined by potentiometric methods [41]) associated with (i) protonation of the dimethylamino function of the iV-methyl 4-dimethylaminophenylalanine residue - pKji =4.1 and (ii) deprotonation of the hydroxy group of the hydroxy-picolinic acid residue - pK,2 = 7.3. The molecule is neutral between pH = 4 and pH = 7 and is water soluble at pH less than 3 as the corresponding acid-salt. 

C6H5N03 picolinic acid N-oxide 824-40-8 489.15 42.843 2 7020 C6H6N203 6-hydroxy-5-nitro-2-picoline 39745-39-6 377.15 32.218 2... 

Various reports in the literature indicate the influence of endocrine organs on tryptophan metabolism. Chiancone and co-workers (C5, V2) reported that ovariectomy or hypophysectomy of rats caused increased excretion of xanthurenic acid and that adrenalectomy caused a decrease. An adrenal mechanism is suggested for the regulation of 3-hydroxy-anthranilic acid conversion to nicotinic and picolinic acids (M7). 

IR spectra of the La(III) and Ce(III) complexes of Schiff bases from the condensation of 2-hydroxy-1-naphthaldehyde with a-aminoacids show ONO-tridentate coordination (except for the L-glutamine derivative, which is OONO-tetradentate.479 The IR spectra of Pr(III), Eu(III), Gd(III), Dy(III) and Yb(III) complexes of furohydroxamic acid show that the ligands are N.O-bidentate.480 Raman and IR spectra of [Er(pic)4]", where Hpic = picolinic acid, reveal that the complex is 8-coordinate, with each ligand coordinated through a (unidentate) carboxylate O and a ring N atom.481... 

Carboxylation of the potassium salt of 3-hydroxy-6-methylpyridine (145) gave the picolinic acid 146(84MI16). The Hammick condensation reaction of picolinic acid with benzaldehyde has been studied with regard to the effect of solvent, temperature, and molar ratio of reactants (85MI5). Benzoyl chloride, or benzaldehyde, and l-benzyl-4,6-diphenylpyridinium-2-carboxylate afford 2-benzoyl-4,6-diphenylpyridine (85JCS(P1)2167). Sulfur and 1,4,6-triaryl-pyridinium-2-carboxylates 147 in xylene at 140°C give the corresponding pyridine-2-thiones 148(838149). 

Substituted nicotinic acid derivatives, such as 6-hydroxy nicotinic acid are important building blocks for the synthesis of pesticides and pharmaceuticals, acting as specific inhibitors of NAD/NADP-dependent enzymes. In a process developed by Lonza (Switzerland), 6-hydroxy nicotinic acid is produced by whole-cell microbial hydroxylation of nicotinic acid with Achromobacter xylosoxidans (yield > 100 g 1 ) (Fig. 16). A similar process for the production of 6-hydroxypicolinic acid (98 g l-1) and derivatives from picolinic acid (derivatives), based on Alcaligenes faecalis, has also been established [174,175]. 

Picolinic acid (pyridine 2-carboxylic acid) complexes of chromium(III) have been the subject of a number of studies. Complexation by picolinic acid in water/ethanol (30% v/v) follows an ion-pairing, Eigen-Wilkins type mechanism.Activation parameters suggest an associative character for the reaction of the aqua complex. Chelated complexes of chromiuni(ni) and picolinic acid are the products of the rapid, inner-sphere reduction of [Co (pico)(NH3)5p with chromium(II). The reaction of the related 4-carboxylic acid complex of cobalt(III) with chromium(II) is also rapid in contrast, pyridine-3-carboxylic acid (nicotinic acid) complexes undergo slower reactions. A -hydroxy-bridged dimeric complex [Cr2(pico)4(OH)2] has also been prepared. A study of magnetic properties in the temperature range 16-300 K leads to J - —6 cm and g = 2, typical for such complexes. 

HyPic, hydroxy-3-picolinic acid 4-oxo-LPip, 4-oxo-L-pipecolic acid. 

The I OH of the picolinic acid residue is involved in an internal hydrogen bond with the TCO but nevertheless this functionality is not sterically crowded and would therefore be predicted to be accessible for chemical modification (see Sect. 4.4.1). In contrast, the nitrogen atom of this residue is buried within the molecule and therefore on steric grounds inaccessible for chemical manipulation. However, alkylation of this nitrogen atom was shown to be possible (see Sect. 4.4.3). This may be due to a change in conformation associated with deprotonation of the 1-hydroxy of this residue under the reaction conditions. 

Acylations of the hydroxy function of the picolinic acid residue occurred readily using standard acylation procedures reaction of pristinamycin with acid chlorides or anhydrides in the presence of pyridine or triethylamine afforded the corresponding esters (15) and the use of N or 0-chlorocarbonyl reagents afforded carbamates or carbonates. 

Nicotinic Add Metabolism. The sequence of reactions leading to the formation of pyridine compounds is of particular interest as a source of nicotinic acid. Nutritional, isotopic, and genetic experiments have all shown that tryptophan and its metabolic derivatives including 3-hydroxy-anthranilic acid are precursors of nicotinic acid in animals and in Neuro-spora. The terminal steps in this sequence are not known. Under certain physiological conditions an increase in picolinic carboxylase appears to reduce nicotinic acid synthesis. This implies a common pathway as far as the oxidation of 3-hydroxyanthranilic acid. Whether quinolinic acid is a precursor of nicotinic acid is still uncertain. The enzyme that forms the amide of nicotinic acid also has not been isolated. Subsequent reactions of nicotinamide include the formation of the riboside with nucleoside phosphorylase and methylation by nicotinamide methyl-kinase. In animals W-methylnicotinamide is oxidized to the corresponding 6-pyridone by a liver flavoprotein. Nicotinic acid also forms glycine and ornithine conjugates. Both aerobic and anaerobic bacteria have been found to oxidize nicotinic acid in the 6-position. ... 

Rate increases of up to 10 have been identified in the reactions with alcohols where hydroxy-acids and oxalic acid are present. In accordance with the mechanism postulated, a co-oxidation of both substrates takes place with a single three-electron transfer. Acceleration of a similar order of magnitude has been shown to occur in the presence of picolinic acid but in this instance the added substrate acts only as a redox catalyst and not as a co-reductant. ... 

Mo(CO)a is decarbonylated on reaction with picolinic acid (picH) to give eight-co-ordinate [Mo(pic)4], and reaction of a mixture of Mo(CO)e, W(CO)8, and 2-hydroxy-6-methylpyridine (Hmhp) affords [MoW(mhp)4] containing a heteronuclear metal-metal quadruple bond. ... 

Mixed complex formation kinetics between LnEDTA and L, where L stands for 5-sulfosalicylate [74], 8-hydroxy quinoline-5 sulfonate and picolinate [75] were studied and two pathways namely acid-dependent and acid-independent pathways have been identified. The overall reaction stoichiometry may be written as... 

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