Tripeptides metal complexes

Trimethylenediamine, N-(2-aminoethyl)-metal complexes, 49 Tripeptides metal complexes blood plasma, 966... 

The kinetics and mechanisms of substitution reactions of metal complexes are discussed with emphasis on factors affecting the reactions of chelates and multidentate ligands. Evidence for associative mechanisms is reviewed. The substitution behavior of copper(III) and nickel(III) complexes is presented. Factors affecting the formation and dissociation rates of chelates are considered along with proton-transfer and nucleophilic substitution reactions of metal peptide complexes. The rate constants for the replacement of tripeptides from copper(II) by triethylene-... 

Buryak and Severin have described the use of dynamic libraries of Cu(II) and Ni(II) complexes as sensors for tripeptides [61]. A notable aspect of this work is that as isolation of the metal complexes is not necessary (sensing is accomplished by observing changes in the UV-vis spectrum), potential concerns over the lability of coordination complexes do not apply. Specifically, three common dyes [Arsenazo I (41), Methyl Calcein Blue (42), and Glycine Cresol Red (43), Fig. 1.18] were mixed with varying ratios and total concentrations of Cu(II) and Ni(II) salts in a 4X5 array. Previous work had demonstrated that these conditions produced equilibrating mixtures of 1 1 and 2 1 homo- and heteroleptic complexes [62], These arrays were able to clearly and unambiguously differentiate tripeptides based on the differential pattern of response. The Severin laboratory has... 

Collman and Buckingham (1963) have reported preliminary results of studies on the hydrolytic cleavage of amino-terminal peptide bonds by m-hydroxyaquotriethylenetetraaminecobalt(III) ions. The amino-terminal residues of di- and tripeptides are selectively hydrolyzed by one equivalent of metal chelate and are converted to an inert metal complex. The reaction proceeds as shown on p. 63. 

Yan, X., Zeng, X., Cheng, S., Li, Y, Xie, J. Metallomicellar catalysis cleavage of p-nitrophenyl picolinate catalyzed by binuclear metal complexes coordinating tripeptide in CTAB micellar solution. J. Colloid Interface Sci. 2001, 255(1), 114-118. 

Buryak, A. Severin, K. Easy to optimize Dynamic combinatorial libraries of metal-dye complexes as flexible sensors for tripeptides. J. Comb. Chem. 2006, 8, 540-543. 

Severin and Buryak have utilized mixtures of commercial dyes and simple metals [Cu(II) and Ni(II)] to generate DCLs capable of distinguishing closely related di- and tripeptides [11]. The DCL was generated by the combination of metal and dye, which created a complex mixture of uniquely UV-Vis-absorbing coordination compounds. Addition of the analyte (usually a di- or tripeptide) shifted the library speciation that then created a new UV-Vis spectrum (Fig. 5.10). Combining this principle with linear discriminant analysis of the spectrum (in conjunction with learning datasets)... 

Amides. Metal ions catalyze the hydrolysis of a variety of amides, including acylamino acids, dipeptides and tripeptides, and amino acid amides. In all these compounds it is possible for a metal ion to complex with one or more ligand groups, either amine or carboxylate ion functions, in addition to the amide group. Thus the structural prerequisites for the metal ion catalysis of amide hydrolysis are the same as those for ester hydrolysis. 

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... 

Base-catalysed hydrolysis using alkali metal hydroxides or carbonates in aqueous methanol or THF remains the commonest method for cleaving simple esters limited mainly by the stability of the substrate to the basic conditions. In more complex substrates, lithium hydroxide in a mixture of THF-methanol-P O (2 2 1) is the base of choice.1-3 In a synthesis of Lepicidin A, Evans and Black4 accomplished the hydrolysis of a methyl ester with lithium hydroxide in aqueous /err-butyl alcohol at 35 °C [Scheme 6.1). Destannylation that accompanied hydrolysis with other solvents was not observed nor was harm inflicted on the TIPS and TES ethers. In a synthesis of cydoisodityrosine derivatives, Boger and co-workers attempted to hydrolyse methyl ester 2 1 [Scheme 6.2] with 1-3 equivalents of lithium hydroxide in a mixture of THF-methanol-HaO (3 1 1) at room temperature, but the desired hydrolysis was accompanied by scission of the tripeptide side chain from the ring system. However, when the reaction was conducted in the presence of the more nucleophilic lithium hydroperoxide, the desired hydrolysis was achieved in 97% yield without racemisation. 

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