Chelidamic acid

Phthalate/sulphate 1 Chelidamic acid/sulphate J Ali Dzombak, 1996... 

Hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid) [138-60-3] M 183.1, m 254"(dec). Crystd from water. 

Azinecarboxylic acids lose C02 significantly more easily than benzoic acid. Pyridinecarboxylic acids decarboxylate on heating with increasing ease in the order (3 < < y < a. 2-Pyridazinecarboxylic acid gives pyrazine at 200°C, and 4,5-pyrimidinedicarboxylic acid forms the 5-mono-acid on vacuum distillation. Pyrone- and pyridone-carboxylic acids also decarboxylate relatively easily thus, chelidonic acid (680 Z = O) at 160°C over copper powder and chelidamic acid (680 Z=NH) at 260°C give (681 Z = 0, NH). 

Pyridones, pyrones, azinones, and A/-Oxides. 2- and 4-Pyridones and 2- and 4-pyrones readily give their 3-mono- and 3,5-dihalo derivatives even chelidamic acid 125 reacts in this way. Bromination of pyran-2-one 58 gives the substitution product 126 or the addition product 127 depending on the conditions. 

Chelidamic acid 6.6B Chelidonic acid 6.6B Chelidonium Chelidostatin 13.5B Chenopodium RIP-I 9.1A Chicoric acid 9.5Ap Chlamydocin 9.6C Chloramphenicol 9.2n Chloro-dihydroillicinone E 6.1 A Chloro-dimethylaminopropyl-phenothiazine 5.4n... 

Two syntheses of racemic betalamic acid have been carried out so far. In Dreiding s approach (Scheme 1) (11,90,91), chelidamic acid (62) was used as the starting material. Hydrogenation of 62 with a rhodium catalyst yielded an all-cw piperidine derivative, which was converted to the dimethyl ester 63. The conditions used for the hydrogenation step kept the concomitant removal of the hydroxyl group to a minimum. The oxidation of alcohol 63 to the corresponding piperidone derivative 64 required careful control of the reaction conditions to avoid overoxidation to pyridine derivatives. This was accomplished by use of a polymeric carbodiimide in the Pfitzer-Moffat oxidation, which afforded the desired product 64 in 90% yield. For the introduction of the side chain, a new... 

Temperature-jump experiments were performed with aqueous solutions of 2-chloro-4(l/7)-pyridone and 2,6-di(methoxycarbonyl)-4(17/)-pyridone (chelidamic acid dimethyl ester). It was suggested that when the tautomeric functional group is remote, tautomeric interconversion occurs through intermediate ionization and dissociation followed by ion recombination (77JA4438). 

The dipicolinic acid platform has proven to be extremely versatile, leading to numerous applications of its tris-complexes with Eu and Tb, in particular in analytical and bioanalytical chemistry (see Section 2.5 for photophysical properties and Section 6.2 for bioanalytical applications). As a consequence, researchers have invented ways of modulating the photophysical properties, principally by introducing substituents on the para position of the pyridine ring, a relatively easy synthetic procedure. Simple substituents (e.g.. Cl, Br, NH2, NHCOCH3) are introduced by substitution of the hydroxyl function of chelidamic acid under... 

The number of Lewis bases chelating the lanthanide ions also plays an important role in determining the solution stability of the polymerized liposomes. Thus, polymerized liposomes from the EDTA lipid (Figure 10.9) were stable and efficiently sensitized the chelated Tb + ions. On the other hand, polymerized liposomes containing Tb + ions chelated with chelidamic acid (Figure 10.9) were found to aggregate in solution. ... 

Eu(CDA)3] CDA = chelidamic acid D2O circularly polarized excitation (Metcalf et al., 1990b)... 

The acid dissociation constants of chelidamic acid chelates [2,6-dicarboxy-4-hydroxypyridine (X-123)] as a function of the metal M were deter-mined. The pK of the hydroxyl group in these chelates increased in the order Cu(ll) < Co(II) < Zn(Il) < Ni(II) < Mn(II). 

Stability constants have been determined for 1 1 bivalent metal complexes of UO2, Cu, Pb, Zn, Be, Ni, Co, Cd, and rare earths with 3-hydroxy-2-pyridone Stability constants of 1 1 complexes (XI-793) formed by chelidamic acid (HjL) and Ca, Ba, Sr, Mg, and Mn, and of 1 1 and 1 2 complexes, M(HL)j, from chelidamic acid and Co, Ni, Cu, and Zn have been determined. These complexes are stabilized by loss of the phenolic proton in alkaline solution. ... 

In a study designed to investigate the effect of the presence on a ligand of one or more protons on the mechanism of complex formation with nickel(n), Wilkins and co-workers have published a list of 13 rate constants for derivatives of imidazole, 2,2 -bipyridine, and 1,10-phenanthroline and for cysteine, penicillamine, chelidamic acids, and pyridine-2-aldoxime. As expected, if the proton is far removed from potential reaction sites it has little effect but if it blocks a binding position, as in bipyH+ and particularly phenH+, it has a much lar r effect on kt. Frequently, however, the effect of the proton appears to be merely to reduce Kos (and therefore kt) by increasing the positive charge on the ligand (cf Table 8). 

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