Copper complexes glycinates

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). 

The reaction of the chelate of copper(II) and glycine at elevated temperatures in basic solution (100°C and pH 11) with formaldehyde gives the copper complex of serine and with acetaldehyde gives the copper complexes of threonine and allothreonine in 64% yield (1, 176). 

Copper complexes of amino acids have also been found to be effective in preventing and reducing the severity of Shay ulcers [267, 268]. As data in Table 6.17 show, the copper complex of glycine was the most effective of all of the amino-acid complexes studied and it was essentially as effective as Propantheline in reducing ulcer number as well as ulcer severity [267]. 

Because /3 is the symbol for the product of individual stability constants, we write j8 = KxK for the combination of copper with glycine and for all other cases where a metal becomes saturated after combining with two portions of a ligand. For zinc and ethylenediamine, where the zinc becomes saturated after fixing three portions of the ligand, we write = KxK2K and, for the complex of a metal that is saturated when it has combined with one unit of ligand (for instance, zinc and EDTA), = Kx. 

For methyl glycinate at 25°C, ko - is 7.6 x 10 M s and k for water attack is 4.3 x 10 s. The observed first order rate constant for water attack can be converted to a second order rate constant by dividing by the molar concentration of water OChk) = k/55.5 = 7.7 X 10 M s ). The ratio Icoh- hjo = 10" and is a measure of the relative nucleophilicities of hydroxide ion and water towards the copper complex. The ratio kou-/kg = 7.6 X lOVl.28 10 and this is within the normal range of rate enhancements (10 -10 fold) observed for copper(II) promoted hydrolysis of carboxylic esters where copper(II) interacts directly with the alkoxycarbonyl group of the ester. 

The above method, contrary to the methods of estimation of amino acids based on copper complexes, is selective. A threefold excess of several common amino acids (including histamine) does not interfere. The method thus enables free histidine to be determined in protein hydrolysates, provided that the histidine concentration is sufficiently high. Tryptophane deforms the polaro-graphic waves when present in an amount corresponding to half that of histidine (above 1 mg/10 ml.). Mercaptoamino acids also interfere, but most of the types of compounds are destroyed during the protein acidic hydrolysis. Glycine affects the end-point if present in amounts larger than 10 mg/10 ml. of the sample. 

Interaction of a copper complex of glycine with ethanal yields the threo and erythro isomers in the ratio of 2 1. They are separated on the basis of their differences in solubility ... 

The copper complex of glycine has been used for the synthesis of j3-hydroxy-ot-amino acids. Under alkaline conditions the carbanion (1) formed from the complex adds to aliphatic and aromatic aldehydes, as in the formation of threonine (2) [18]. Further work on this reaction has shown that the protons on nitrogen in (1) also dissociate under the basic conditions and this has led to an improved procedure which employs the tridentate complex (3), having the double protection of Schiff s base and chelate formation [19]. 

Thermodynamics of ion association. Copper complexes of diglycine and tri- 273 glycine... 

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. 

---