Amino acids chromium complexes

The reaction of chromium(iii) with an excess of NH2C2H4OH affords [Cr(NH2CH2CH20)3] initially, which is converted into a dimeric species on standing. Several chromium(iii) amino-acid complexes have been prepared... 

Headlam HA, Weeks CL, Turner P, Hambley TW, Lay PA. 2001. Dinuclear chro-tnium(V) amino acid complexes from the reduction of chrotnium(Vl) in the presence of amino acid ligands XAFS characterization of a chromium(V) amino acid complex. Inorg Chem 40(20) 5097-5105. 

Attempts to isolate GTF from brewer s yeast have resulted in production of very active concentrates, but the substance is too labile to be obtained in the soHd state (136). However, it has been shown that GTF is a Cr(III) complex containing two coordinated nicotinate radicals and other amino acid anions (146). Active preparations containing similar complexes have been synthesi2ed (147). Chromium deficiency may also lead to atherosclerosis and peripheral neuropathy. 

Photodriven reactions of Fischer carbenes with alcohols produces esters, the expected product from nucleophilic addition to ketenes. Hydroxycarbene complexes, generated in situ by protonation of the corresponding ate complex, produced a-hydroxyesters in modest yield (Table 15) [103]. Ketals,presumably formed by thermal decomposition of the carbenes, were major by-products. The discovery that amides were readily converted to aminocarbene complexes [104] resulted in an efficient approach to a-amino acids by photodriven reaction of these aminocarbenes with alcohols (Table 16) [105,106]. a-Alkylation of the (methyl)(dibenzylamino)carbene complex followed by photolysis produced a range of racemic alanine derivatives (Eq. 26). With chiral oxazolidine carbene complexes optically active amino acid derivatives were available (Eq. 27). Since both enantiomers of the optically active chromium aminocarbene are equally available, both the natural S and unnatural R amino acid derivatives are equally... 

The percentage collection of chromium (III) with hydrated iron (III) oxide may decrease considerably in the neutral pH range when organic materials capable of combining with chromium (III), such as citric acid and certain amino acids, are added to the seawater [41]. Moreover, synthesised organic chromium (III) complexes are scarcely collected with hydrated iron (III) oxide over a wide pH range [41]. 

The Cotton effects in mixed amino acidate/acetylacetonate complexes [Cr(acac)2L] (L = l-alanine, L-valine or L-phenylalanine) have been studied 774 absolute configurations were assigned by reference to the parent tris(acetylacetonate) complexes. Synthesis was achieved by the photolysis of mixtures of the amino acid and [Cr(acac)3]. The partial photoresolution of both cis- and irans-(l,l,l-trifluoro-2,4-pentanedionato)chromium has been accomplished by irradiation with circularly polarized light (5461 A) in chlorobenzene solution.775 The results indicated that both bond rupture and twist mechanisms were important. A number of other jS-diketonates have also been investigated.776... 

For tridentate amino acids with three non-equivalent donor atoms such as L-aspartic acid or L-cysteine, the isomers possible are illustrated below (252-254). There have been a number of reports of the preparation of L-aspartic acid complexes.1180,1181,1182. In the earlier work the isomers were not identified, however in the later study, the complexes were tentatively identified by comparison of their spectroscopic properties with those of the corresponding cobalt(III) complexes.1183 The order of elution of the complexes on HPLC was also similar to that observed for the corresponding cobalt(III) complexes. Mixed complexes containing l- or D-aspartate and L-histidine were also prepared.1182 A crystal structure of one salt obtained from this kind of system, bis(L-histidinato-0,Ar,Ar )chromium(III) nitrate, has been determined.1184... 

Sodium bis(L-cysteinato)chromate(III) dihydrate has been prepared by refluxing L-cysteine with chromium(III) nitrate and neutralizing the solution.1185. The product is a dark blue solid in which cysteine is coordinated with the sulfur atoms trans (see 252-254). A number of chloro and other complexes of cysteine and related amino acids have been studied.1186 A related complex L-histidinato-D-penicillaminatochromium(III) has been prepared11 7 and its crystal structure reported. 

The amino acids believed to be involved in GTF are the constituents of the naturally occurring tripeptide glutathione (256). Anderson et al. have reported a complex of glutathione/nicotinic acid and chromium(III) to be particularly active in their in vitro assay.1198 The complex was described as being purified by HPLC, but the details of the preparation are not available. 

A similar argument can be applied to the results of later work by Idelson et al.i9 In this they prepared the chromium complex (133) by interaction of the 1 1 chromium complex of 1-phenyl-3-methyl-4-(2-hydroxy-4-cyanonaphth-l-ylazo)-5-pyrazolone and diethylenetriamine and by reaction of the azo compound with [Cr(CO)3dien]. Identical products were obtained and, since the diethylenetriamine occupies9 a facial position in [Cr(CO)3dien], it was concluded that the complex (133) had a facial configuration. Similarly, the reported77 separation of isomeric 2 1 chromium complexes of 2-amino-6-(2-hydroxy-6-nitro-4-sulfonaphth-l-ylazo)-5-naphthol-7-sulfonic acid is... 

It has been proposed that GTF is related to a dinicotinatotris(amino acid)chromium(III) complex, which forms a ternary complex at the membrane receptor with insulin. Porcine insulin binds a Cr(nic)2(glutathione) complex very tightly. 

Many relatively specific reagents, particularly a variety of metal complexes, have been developed as an aid to the isolation of individual amino acids. An example is provided by the isolation of L-proline from a gelatine hydrolysate using the chromium complex ammonium rhodanilate ammonium dianiline-... 

C.I. Solvent Orange 56, [12227-68-8], simliar to C.I. Solvent Orange 5, 518745 1, [13463-42-8], which is a 1 1 chromium-complex dye, synthesized by di-azotizing 2-hydroxy-3-amino-5-nitrobenzenesulfonic acid and coupling to 1-phe-nyl-3 -m ethyl-5 -pyrazolon e. 

The synthesis of the 1 1 complex 8 is an example of [10] demethylative chroma-tion. It is prepared by diazotization of 5-amino-2-chlorohydroquinone dimethyl ether and coupling onto 1-hydroxynaphthalene-5-sulfonic acid. The reaction product and Cr203 in formic acid are heated in an autoclave at 130 °C. The chromium complex 8 [80004-31-5] is obtained as a black powder that gives grayish blue dyeings on wool and leather. 

As an example of 1 2 chromation by the chromium(m) salicylic acid method [19], the sodium salt of the azo dye obtained from diazotized 1-amino-2-hydroxy-5-nitrobenzene and acetoacetic acid 3-sulfonamidophenylamide in water and a solution of chromium(m) sodium potasium salicylate are refluxed for several hours. The 1 2 chromium complex 11 is precipitated at below pH 4. It is a yellow brown powder, which is soluble in hot water with a greenish yellow color. 

As an example of 1 2-chromation by the dichromate-glucose method [20], the azo dye obtained by coupling of diazotized l-amino-2-hydroxy-5-nitrobenzene with l-methylsulfonylamino-7-hydroxynaphthalene is dissolved in dilute NaOH and boiled after addition of K2Cr20r2H20 and glucose. Chromation is complete after a few minutes. The resulting 1 2 chromium complex 12 [83748-22-5] is precipitated with NaCl to give a black powder that imparts bluish olive dyeings on wool in a weakly acidic dyebath. 

In the stepwise synthesis of the unsymmetrical complex dye 13 [ 70236-60-1] [10], the azo dye made from diazotized l-amino-2-hydroxy-5-nitrobenzene and 1-phenyl-3-methyl-5-pyrazolone and the 1 1 chromium complex obtained from 6-nitro-l-diazo-2-hydroxynaphthalene-4-sulfonic acid and 2-naphthol are heated together at 80 °C for 5 h. The adduct is salted out with NaCl. A black powder is obtained that dyes wool and leather in dark brown shades. The resulting colors are fast, particularly on shrink-resistant wool. 

Unsymmetrical 1 2 chromium complexes based on an azo and an azomethine dye ligand can be prepared directly from a mixture of a 1 1 chromium complex and equimolar quantities of an 2-aminophenol, an anthranilic acid, or an aliphatic amino acid, and of salicylicaldehyde or a substituted salicylaldehyde [22],... 

In the synthesis of the disulfonated 1 2 chromium complex dye 16 [82269-28-1] [28], a mixture of the azo compound made from diazotized 2-amino-1,4-dichlorobenzene-5-sulfonic acid and salicylaldehyde is heated to 50 °C with... 

A further example shows that one may add more amino acids to an amino acid ester -earbene complex by employing the customary methods of peptide chemistry (64). Starting from pentacarbonyl[GlyOMe (phenyl) -earbene]chromium(0) and using the. V-hydroxysuccinimide/dicyclohexyl-carbodiimide) (NHS/DCCD) method, we succeeded in synthesizing the sequence 14 to 17 of human proinsulin C-peptide (Scheme 3). 

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