Amino acids metal complexes

The methylene group of a-amino acid metal complexes such as the copper(II) glycinato complex is activated to some extent by the polarizing influence of the metal.46,47 Consequently, carban-ion-type reactions can be carried out at this position, while the amino and carboxyl groups are protected by coordination. These reactions cannot be performed on either the free ligand or the conjugate base. 

In addition to this we have several examples of which the polymer conformation of the polymeric complex leads the asymmetrical selectivity Hydrogenation reactions of 1-methylcinnamic acid and 1-acetamidocinnamic acid by several poly(L-amino acid)-Pd complexes are observed (142-144). Poly(L-valine) (/3-form) and poly(/3-benzyl-L-aspartate) (a-helix, sinistral) give dextrorotative products, and poly(L-leucine) and poly( 3-benzyl-L-aspartate) (a-helix, dextral) do levo-rotatory products. Also, optical active poly-/3-hydroxyl esters-Raney Ni catalyst (145) and Ion-exchange resin modified by optical active amino acid-metal complex (146,147) are observed in asymmetrically selective hydrogenations. 

The stability constants as shown in Table 3 are in the same order of magnitude as those of amino acid metal complexes (79). It is interesting to note that with the stepwise addition of phosphate residues, the stability of the corresponding metal complex is progressively increased. Here we come right into the discussion as to where the binding site of... 

Figure 4.3 Common binding modes of amino acid metal complexes. Monodentate through (a) carboxy terminus, (b) amine terminus, and (c) side chains (met and his shown) bidentate through (d) amine and carboxy termini and (e) carboxy terminus.8...

An alternative technique for the resolution of enantiomers which lack polar functional groups is a diastereomeric complex formation via non-ionic mechanisms. These complexes may be of the external or the inclusion type. Chiral amino acids, metal complexes or host compounds may serve as useful complexing agents (Table 2) [49-64]. 

Pirkle or brush type bonded phases Helical chiral polymers (polysaccharides) Cyclodextrins and crown ethers Immobilised enzymes Amino acid metal complexes Three-point interaction Attractive hydrophobic bonding Host guest interaction within chiral cavity Chiral affinity Diastereomeric complexation... 

Racemization amino acids metal complexes, 467 Radioactive waste high level disposal, 895 Radiochemical purity technetium-99 in medicine, 976 Radionuclides... 

These methods have most often been utilized to investigate the chiral recognition of biorelevant molecules such as amino acids and amino acid esters. Chiral crown ethers as well as cyclodextrins and amino acid metal complexes have been used in a number of studies. " To illustrate the ability of MS to analyze chiral recognition, we focus now on the serine octamer. ... 

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