Bipyridine amino acid

Synthetic bipyridine amino acids have been used to construct polypeptides with bipyridine in the backbone. A bipyridine ligand with both an amino and an acid functionality, 4 -aminomethyl-2,2 -bipyridyl-4-carboxylic acid, was incorporated into a hexapeptide and used to coordinate and encapsulate a Ru11 ion. Because the bipyridine group is in the main chain, it can constrain the peptide backbone and influence its secondary structure.171... 

The coordination geometry around the copper atom in 4 is similar to simple Cu complexes of 6,6 -bis-(acylamino)-2,2 -bipyridine amino acids in that the Cu(II) is coordinated by the two bpy nitrogen atoms and the amide oxygens. Amide oxygen coordination to Cu(n) is observed also in Fairlie s complex. In their work, Fairlie and coworkers have... 

Crystal stmctures of complexes of copper(II) with aromatic amine ligands and -amino acids " " and dipeptides" have been published. The stmctures of mixed ligand-copper complexes of L-tryptophan in combination with 1,10-phenanthroline and 2,2 -bipyridine and L-tyrosine in combination with 2,2 -bipyridine are shown in Figure 3.2. Note the subtle difference between the orientation of the indole ring in the two 1,10-phenanthroline complexes. The distance between the two... 

Studies of the thermodynamics of formation of complexes of zinc with 2,2 -bipyridine in the presence of halide and thiocyanate ions in DMF has been carried out.205 The zinc complexes of 2,2 -bipyridine with A-(benzenesulfonyl)glycine and A-(toluene- -sulfonyl)glycine were synthesized and infrared data implied a structural analogy with the cadmium complexes. This suggests that the zinc promotes sulfonamide nitrogen deprotonation in the amino acid ligands in the solid state.206... 

Tris(2,2 -bipyridine)ruthenium(UI) complex ions (44) produce a chemiluminescence in the presence of amino acids in a FTA system. Amino acids containing secondary amino groups have the strongest response LOD 20 pmol for proline to 50 nmol for... 

The sweet potato enzyme could be inactivated by o-phenanthroline and 2,2 -bipyridine the activity could be restored by the addition of Zn2+ and partially by added Mn2+ or Co2+ (69). The amino acid composition revealed an usually large content of tyrosine. Later experiments were able to quantitate the amount of Mn present at two Mn per mole enzyme (70). Additionally, the native enzyme was shown to be EPR inactive however, treatment of the enzyme with acid led to the appearance of a six-line pattern typical of aqueous Mn2+ coincident with the loss of the purple color, further evidence for the association of Mn with the 555-nm absorbance band. 

Examples of amino acids with bipyridine units on the peptide side chain are also known.274 The 6-bromomethyl bipyridine has been used in the stereoselective synthesis and incorporation of an amino acid with a bipyridine binding site into short peptide chains.275 The ligand (5)-2-amino-3-(2,2 -bipyridin- -yl)propanoic acid, where n = 4-6,276 has been prepared in 98% ee.277... 

There has been considerable interest in the chemistry of ternary complexes of copper(II) containing a bidentate aromatic nitrogen base such as 1,10-phen-anthroline (phen) or 2,2,-bipyridine (bpy) and a bidentate oxygen donor ligand or an amino acid,1 6 as some of these could possibly serve as models for enzyme-metal ion-substrate complexes. Two procedures are described below for the convenient, high-yield preparation of two such complexes. 

Reductions can also be performed in water. Systems for reduction of ketones in water can be water-compatible sodium and lithium borohydrides, amino acid-based cationic surfactants to reduce aryl ketones [19], iridium hydrides used in transfer hydrogenations, such as [Cp Irm(bpy)H]+ (Cp — q5-C5Mes, bpy = 2,2 - bipyridine) [20], and IrHCI2(cod) 2 with a chiral diaminodiphosphine ligand to form secondary alcohols in high enantioselectivity and almost quantitative yield (Equation 4.12) [21]. 

Figure I. Conformational changes mediated by Cu(II) eoordination to the bipyridine group of the transoid 6,6 -bis-(acylanuno)-2,2 -bipyridine-peptide 3 to complex 4 having a cisoid conformation R = a-amino acid side chain (adapted from [8]).

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