7-Carboxy pyridine

Reasons for reaction at C-4 rather than C-6 are not clear, but one possibility is that reaction actually occurs via the carboxy-pyridine form. If that is so, then both steric bulk around the 6-position and the greater acidity of the 4-proton could favor deprotonation at C-4 (Scheme 122). 

It might be considered that the way in which to understand the water complex ion chemistry of the lanthanide ions in aqueous solution would be to start from their hydrates. In fact the hydrates prove to be most intransigent complexes. Their structures are still somewhat uncertain. I shall therefore start from a study of the tris-dipicolinates, i.e. tris 2,2 -carboxy-pyridine complexes, Ln(dipic)3, about which a great deal is known. 

Die Reaktion lafit sich auf 2-AminomethyI-pyridine und 5-Chlor-2-amino-pyridin sowde auf 2-Methylamino- und 2-Benzylamino-pyridin iibertragen. Dagegen biiden 2,5-Diamino-pyridin, 5-Nitro-2-amino- und 6-Amino-3-carboxy-pyridin keine Dimere. 

This has restricted many of our studies of Pt(II) complexes to intermediate fields (e.g. 4 7 T). Pt(IV) complexes are less anisotropic and the effect is less marked It is probable that CSA relaxation is partly responsible for our failure to observe Pt signals directly from Pt bound to macromolecules. CSA relaxation of Pt can also lead to the disappearance of Pt satellites from C or spectra. These are normally used as indications of binding sites. Pt couplings appear in the spectra of coupled ligand nuclei as 1 4 1 multiplets only if relaxation times are the same in Pt(I 0) and Pt species. Indications that differences could exist were noted in NMR studies by Erickson et al ( ) on 1,2-diaminoethane complexes, and Lallemand et al ( ) for nucleoside complexes. We have recently shown ) for trans-Pt(ethene)(2-carboxy-pyridine)Cl2 that the broadening of satellites at high field arises from Pt relaxation via the CSA mechanism. The effect on the satellite linewidths is proportional... 

Zur Oxygcnicrung mit dcm Silber(II)-Salz des Carboxy-pyridins s. Lit.127. x,/J-ungesattigte Aldehyde lassen sich mit Silber(II)-oxid und Cyanid unter Erhalt der Konfiguration an der C = C-Binaung oxygenieren128 z.B. ... 

Nicotinic amide, C H4N.CO.NH2, is a constituent of the coenzymes, co-dehydrase I and II, and as such acts as a hydrogen carrier in tissue respiration. The amide is derived from nicotinic acid, or carboxy pyridine, and is combined with ribose phosphate and adenosine in nucleotide structure in the co-dehydrases. Its hydrogen-carrying power is due to the reducibility of the onium nitrogen in the pyridine ring (p. 258). 

Pyridine-4-carboxylate is hydroxylated by Mycobacterium sp. strain INAl to 2,6-dihydroxypyridine-4-carboxylate. Two different hydroxylation enzymes were involved and were apparently Mo-dependent (Kretzer and Andreesen 1991). The formation of 2-ketoglutarate can, however, be rationalized equally as (3-oxidation to hexahydropyridine-2,3,6-trione-4-carboxy-CoA ester followed by hydrolysis. 

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