Oxalate salts

Beyond pharmaceutical screening activity developed on aminothiazoles derivatives, some studies at the molecular level were performed. Thus 2-aminothiazole was shown to inhibit thiamine biosynthesis (941). Nrridazole (419) affects iron metabohsm (850). The dehydrase for 5-aminolevulinic acid of mouse liver is inhibited by 2-amino-4-(iS-hydroxy-ethyl)thiazole (420) (942) (Scheme 239). l-Phenyl-3-(2-thiazolyl)thiourea (421) is a dopamine fS-hydroxylase inhibitor (943). Compound 422 inhibits the enzyme activity of 3, 5 -nucleotide phosphodiesterase (944). The oxalate salt of 423, an analog of levamisole 424 (945) (Scheme 240),... 

Chemical Designations - Synonyms Potassium acid oxalate Salt acetosella Salt of sorrel Chemical Formula KHC2O4. 

H- and 3//-Azepines are generally unstable in aqueous acid solution and the few examples of simple azepinium salts, namely perchlorates,77 bromides,105 picrates35201 and a solitary iodide,105 have been prepared under nonaqueous conditions. The fractional crystallization of oxalate salts has been used for the separation of mixtures of 4- and 6-substituted 3f/-azepines,66 and 3,6-di-tm-butyl- and 2,5-di-tert-butyl-3//-azepine, on treatment with tetrafluoroboric acid in acetonitrile, are converted quantitatively into their crystalline tetrafluoroboratc salts.70... 

In the studies on rats, the amounts of spinach, cocoa, rhubarb, or oxalate salts fed were much higher than would normally be included in diets. The levels of calcium and vitamin D were generally low. 

Music, S. Gessner, M. Wolf, R.H.H. (1979b) Sorption of trace amounts of gallium(III) on iron(III) oxide. Radiodiim. Acta 26 51-53 Music, S. Gotic, M. Popovic, S. (1994) Formation of y-Fe203 by thermal decomposition of a mixture of Fe(II)- and Fe(III)-oxalate salts. 

Many compounds of curium are known. They include the oxides, Cm02 and Cm203, fluorides CmF4 and CmFs, other halides, CmXa hydroxide, Cm(OH)3, and oxalate Cm2(C204)3. The oxide, hydroxide, fluoride, and oxalate salts are insoluble in water and may be obtained by precipitation reactions. 

The acid is a colorless moderately strong diprotic acid which gives anions 204 and HC204 with log Kp values of 4.3 and 1.2. Neutralization of the acid with bases produces oxalate and hydrogen oxalate salts which are white unless a colored cation is involved. Most of these salts are insoluble except those of the alkali metal cations. The acid and oxalates can be readily oxidized to CO2 andHOHbyMn04 and Cr04, but lesser oxidants maybe... 

An intramolecular [3 + 2] nitrone cycloaddition reaction has been employed in the chiral assembly of L-acosamine and L-daunosamine (81JA3956). Heating the masked aldehyde (503) with the oxalate salt of (-)-(S)-7V-hydroxy-a-methylbenzenemethanamine generated a nitrone which underwent intramolecular cycloaddition to give an 82 18 mixture of diastereomers (504) and (505). The N—O bond of the major isomer was cleaved with zinc... 

The distilled product was dissolved in an equal volume of MeOH, and treated with a half-equivalent of oxalic acid dihydrate, dissolved in 10 volumes of MeOH. This combination gave the slow deposition of crystals of the full oxalate salt (one acid, two bases) as a white crystalline product. The mp of the crude salt was in the 130-150 °C range, and after recrystallization from CH(CN, N-hydroxy-N-methyl-3,4-methylenedioxyamphetamine oxalate (FLEA) had a mp of 146-147 °C. 

To a solution of 4-methoxycarbonyl-4-[(l-oxopropyl)phenylamino]-piperidine (200 mg, 0.68 mmol) in acetonitrile (1.1 ml) is added methyl acrylate (124 pi, 1.36 mmol) at room temperature. The solution is stirred at 50°C for 2 hours, cooled to room temperature, and concentrated to an oily residue. The residue is chromatographed on silica gel (ethyl acetate) to give 3-[4-methoxycarbonyl-4-[(l-oxopropyl)phenylamino]-l-piperidine]propanoic acid, methyl ester as an oil 253 mg, 97%. An equimolar amount of oxalic acid is added to a solution of the free base in ethyl acetate. The precipitated salt is recrystallized by adding methanol and heating until the solid goes back into solution. Upon cooling the salt precipitates as a white solid oxalate salt. It is recrystallized from methanol and 2-butanone m.p. 170°-172°C. 

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