Catalysis phosphate

Dunathan, H. C. Stereochemical aspects of pyridoxal phosphate catalysis. Advan. Enzymol. 35, 79-134 (1971). 

To obtain more insight into the nature of the phosphate catalysis model studies were carried out using glycine and a number of... 

The conversion of the single starting compounds was studied under the reaction conditions, revealing that at pH-7 and higher the monosaccharide was partially consumed by alkali-mediated decomposition,also shown to be enhanced by phosphate catalysis. Therefore all further experiments were performed at pH-5.6, which is the pH obtained by mixing the starting monosaccharides and glycine. 

Figure 5. The order of phosphate catalysis. Plotting of the logarithms of the rate of conversion of the monosaccharides against the concentration of phosphate...

The degree of phosphate catalysis (DPC = ratio of reaction rate in the presence and absence of phosphate) varies with the nature of the dipeptide. The plots suggest that, within each series, DPC is negatively correlated with the relative rate in the absence of phosphate. Phosphate is postulated to act as a proton transfer mediator between the dipeptide carboxy group and the reactive imine centre (see Scheme 3.4). If direct transfer from the dipeptide carboxy group is already sufficiently efficient, the enhancement is decreased. 

Zabinski RE, Toney MD (2001) Metal ion inhibition of nonenzy-matic pytidoxal phosphate catalysis of decarboxylation and transamination. J Am Chem Soc 123 193-198... 

It has been proposed by de Duve (see Further Reading) that primordial acetyl phosphate originates by reaction of acetyl-thioester with phosphate ions. According to the Iron-Sulfur World theory, phosphorylation energy may also result from a transfer of the redox energy of CO/H2S in the presence of amino acids (5), which received its first support by phosphate catalysis of peptide formation (16). Subsequently it was supported by the discovery of a formation of aminoacyl phosphate in reaction of phosphate with aminoacyl N-carboxyanhydride (21) ... 

Aramendia, MA Borau, V Jimenez. C Marinas, JM Romero, FJ. Tlie Mcerwein-Ponndorf-Verley-Oppenauer reaction between 2-hexanol and cyclohexanone on magnesium phosphates. Catalysis Letters, 1999 58, 53-58. 

The anti-tumour agent (4-)-CC-1063 (269) acts by selective alkylation of adenine N(3) which lies in the minor groove. It has been demonstrated that critically ordered water molecules are involved in the drug-DNA interactions and phosphate catalysis of the alkylation reac-... 

Figure 2. Phosphate Catalysis of Amino Proton Exchange vs pH for 2, 3 -cCMP. Additional pmr line broadening (WO due to (Na) phosphate addition (0.05 M) was measured at 3 1°C at 360 Ms for the separate -M9 resonances. Hy (upfield)(circles) and H (downfleld)(squares). Solid curves ware calculated from eq. 1.

The actual catalyst in phosphoric acid-catalyzed Mannich-type reaction of imines with 1,3-dicarbonyl compounds is certainly phosphoric acid itself [74], but metal contaminants, such as alkali or alkaline-earth metals, have interesting effects on the reactivity and stereoselectivity. HCl-washed, metal-free chiral phosphoric acid 149a and chiral calcium phosphate 149b are able to catalyze the Mannich-type reactions. The absolute stereoselectivity of the phosphoric acid catalysis is opposite that of the calcium phosphate catalysis (Scheme 28.16) [75]. 

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