Glycine-copper complex

Chelate is pronounced kee late and is derived from the Greek word for claw. The copper/glycine complexation reaction is shown below. 

A variety of other metals and their complexes have been studied for radioprotective activity. Among these are copper glycinate, strontium chloride, ZnNa -diethylenetriaminepentaacetate (ZnDTPA), and selenium, which has been studied because of its relationship to endogenous antioxidant mechanisms, especiaHy GSH peroxidase and vitamin E. 

It has also been shown that the o -methylene group in chelated glycine will undergo substitution. The reaction of the copper (II)-glycine complex with ketones or aldehydes produces / -hydroxyamino acids (Equation 27) (1, 65). 

It has been known for many years that the rate of hydrolysis of a-amino acid esters is enhanced by a variety of metal ions such as copper(II), nickel(II), magnesium(H), manganese(II), cobalt(II) and zinc(II).338 Early studies showed that glycine ester hydrolysis can be promoted by a tridentate copper(II) complex coupled by coordination of the amino group and hydrolysis by external hydroxide ion (Scheme 88).339 Also, bis(salicylaldehyde)copper(II) promotes terminal hydrolysis of the tripeptide glycylglycylglycine (equation 73).340 In this case the iV-terminal dipeptide fragment... 

The ethyl glycinate-N,N-diacetic acid derivative (12) may be used to illustrate the general features of these reactions. Hydrolysis of the copper(II) complex in the pH range 5-7, studied by pH-stat, corresponds to equation (15) where EGDA2-= ethyl glycinate-AT,N-diacetate and... 

Catalyst screening experiments resulted in the discovery that copper(salen) complex 33 was a highly effective catalyst for the conversion of alanine derivative 16b into (f )-a-methyl phenylalanine 17 under the conditions shown in Scheme 8.16. The presence of just 1 mol% of catalyst 33 was sufficient to induce the formation of compound 17 with up to 92% ee and in >70% yield [33]. Allyl bromide, 1-chloromethylnaphthalene and ethyl iodide also reacted with substrate 16b to give the corresponding (H)-a-methyl a-amino acids in the presence of 2 mol % of complex 33 [34], Complex 33 also catalyzed the asymmetric mono-alkylation of glycine-derived substrate 34 by benzylic or allylic halides, to give (H)-a-amino acid derivatives 35 with 77-81% ee. and in greater than 90% yield, as shown in Scheme 8.17. 

Figure 11-7. Data table for multiple linear regression analysis of spectra of copper(II) complexes by UNEST. Ligand abbreviations GG, glycylglycinate Ga, glycinamide gly, glycinate en, ethylenediamine dien, diethylenetriamine 1,2-DAP, 1,2-diaminopropane tetmeen, tetramefnylethylenediamine. Data from E. J. Billo, Inorg. Nucl. Chem. Lett. 1974, 10, 613.

The chemical reactivity of coordinated glycine and other a-amino acids towards formaldehyde and other aldehydes in alkaline conditions has been under investigation for many years, since the initial work by Sato, Okawa and Akabori. While most of the work has been carried out on copper(II) complexes, some more recent studies on cobalt(III) systems have been made (Scheme 74) 291-295 majority of investigations the complexes resulting from the aldol condensation... 

Several features of the above studies were reinvestigated in a detailed kinetic study of the copper(II) complexes of glycine methyl ester and phenylalanine ethyl ester in glycine buffer at pH 7.3 (26). Glycine was selected as a buffer in this study in order that a small increase in the glycine concentration caused by the hydrolysis reaction would not increase the concentration of copper(II) complexes to a significant extent. It was found that the rate constant for the hydrolysis of the copper(II) complex of DL-phenylalanine ethyl ester was 106 times greater than the rate constant obtained for the alkaline hydrolysis of the free ester (25). 

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