Imidazole thioethers

These authors have reported some interesting electrochemical studies on the imidazole/thioether complex and the bis(imidazole) complex. Substitution of one imidazole by the thioether results... 

Oxidation of thiols (or thiones) can give disulfides or sulfonic acids. Imidazole thioethers are... 

Monodentate ligands such as imidazole, thioethers, pyridine etc. form complexes of all stoichiometric compositions 1 1, 1 2 and 1 3. In the presence of monodentate Ugands the substitution reaction stops at complexes of composition... 

A number of further thioether-imidazole ligands with NS, N2S, N2S2, and N4S2 donor set have been characterized by X-ray crystallography, and they show a comparable coordination behavior.1322-1328... 

In addition to the backbone donor system the amino acid residues can contain a variety of donor centers (679E). The most important of these are the imidazole N atoms of His, the S atom of Cys, and to some extent the, 3-carboxylate O atom of Asp. Other side chain donors like the O atoms of Ser and phenolic O atoms of Tyr or amino N atoms of Lys are of minor importance for coordination of Ni11 ions. Also, thioether S-donors of Met play only a minor role in the interactions with Ni11 ions.1730... 

From the standpoint of modeling Type I copper proteins,4,5,59,60 a variety of imidazole-based ligands containing thioether sulfurs and imidazole groups have been synthesized.61,62 The structures and spectroscopic properties of their copper(II) complexes (51)-(53) and (55)-(60) were investigated.65,79-82 To characterize apical copper(II)-thioether bonding, the complex (51) was... 

Method C l-Methyl-3W-imidazol-2-thione (5.7 g, 0.05 mol), the haloalkane (0.05 mol), and TBA-Br (0.97 g, 3 mmol) in aqueous NaOH (40%, 15 ml) are added to PhH (I50ml) and the mixture is stirred for ca. 6 h at 60 °C. The organic layer is separated, dried over molecular sieves, and evaporated. The imidazolyl thioether is isolated by distillation under reduced pressure. 

The distorted octahedral species [10] and [11] are the essential part of the cytochromes acting as redox catalysts. In these, a very specific porphyrin redox potential may have been adjusted by an appropriate choice of the axial ligands exerting a cis effect on the porphyrin system transmitted through the iron atom. In cytochrome c, these axial ligands are the imidazole of a histidine and the thioether function of methionine, as in [10], and in the cytochromes a or b5 they are presumably two imidazoles of histidine, as in [77] (7). 

Cobalt, Co " (cf ) 4, tetrahedral 5 -Thiolate, thioether, N-imidazole Alkyl group transfer, oxidases... 

Cimetidine contains an imidazole ring comparable to histamine, a sulfur atom (thioether group) in the side-chain, and a terminal functional group based upon a guanidine (see Section 4.5.4). Ranitidine bears considerable similarity to cimetidine, but there are some important differences. The heterocycle is now furan rather than imidazole, and the guanidine has been modified to an amidine (see Section 4.5.4). A newer drug, nizatidine, is a variant on ranitidine with a thiazole heterocyclic ring system. 

The major metal-binding amino acid side chains in proteins (Gurd and Wilcox, 1956 see Voet and Voet, 1990) (Table II) are carboxyl (aspartic acid and glutamic acid), imidazole (histidine), indole (tryptophan), thiol (cysteine), thioether (methionine), hydroxyl (serine, threonine, and tyrosine), and possibly amide groups (asparagine and glutamine, although... 

Recently the structures of silver(I) complexes with cyclo-(glycyl-L-histidyl), cyclo-(L-methionyl-L-histidyl) and cyclo-(L-histidyl-L-histidyl) were examined using 7H and 13CNMR spectroscopy. The NMR measurements suggested that the silver ion was bound to the sulfur atom of the thioether and to the nitrogen atom of imidazole groups in these cyclic peptides, but not to their amide groups.417... 

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