cysteinyldopa has been researched along with benzothiazole* in 2 studies
2 other study(ies) available for cysteinyldopa and benzothiazole
| Article | Year |
|---|---|
Uncovering the structure of human red hair pheomelanin: benzothiazolylthiazinodihydroisoquinolines as key building blocks.
Biomimetic oxidation of the pheomelanin precursor 5-S-cysteinyldopa in the presence of Zn(2+) ions led to the isolation of two isomeric products, one of which could be identified as the benzothiazolylthiazinodihydroisoquinoline 5, while the other proved too unstable for a complete characterization. Both these products were converted into more stable oxidized forms, which after ethylchloroformate derivatization were characterized as the ethyl ester/ethoxycarbonyl isoquinolines 8 and 9. Compound 5 exhibited absorption characteristics similar to those of red hair pheomelanin, including a main band around 400 nm in acids. Similarly to red hair pheomelanin and synthetic pigments, 5 afforded on chemical degradation a thiazolylpyridinecarboxylic acid fragment. Model chemical studies allowed the proposal of a formation mechanism for the benzothiazole and dihydroisoquinoline systems in compound 5. Topics: Benzothiazoles; Cysteinyldopa; Hair; Hair Color; Humans; Isoquinolines; Melanins; Models, Chemical; Molecular Structure; Oxidation-Reduction; Pigments, Biological; Stereoisomerism; Zinc | 2011 |
Metal ions as potential regulatory factors in the biosynthesis of red hair pigments: a new benzothiazole intermediate in the iron or copper assisted oxidation of 5-S-cysteinyldopa.
In the presence of iron or copper ions, the course of the oxidation in air of 5-S-cysteinyldopa (1), the main biosynthetic precursor of pheomelanins and trichochromes, was markedly changed affording two main products. One of these was identified as the oxobenzothiazine 8, previously obtained under nonphysiologically relevant conditions, while the other was characterized as the novel hydroxybenzothiazole 9. Besides 8 and 9, carboxylated and noncarboxylated benzothiazine products were obtained by persulfate oxidation of 1 in the presence of iron or copper ions. The ratio of formation yields of carboxylated/noncarboxylated benzothiazines, determined after reduction of the mixture, was lower than that of the control reaction run in the absence of metal ions, and much lower than that of the oxidation carried out in the presence of zinc ions, in agreement with a recent report. Notably, 8 and 9 were formed in variable yields under different oxidation conditions including tyrosinase/O(2), peroxidase/hydrogen peroxide, and the hydrogen peroxide/or (9E,11Z,13S)-13-hydroperoxyoctadeca-9,11-dienoic acid/Fe(III) systems. Mechanistic routes to 8 and 9 were proposed based on the results of experiments involving in situ generation of labile benzothiazine intermediates. Overall, these results allow to formulate an improved biosynthetic scheme in which metal ions act as critical regulatory factors determining pheomelanin vs. trichochromes formation. Topics: Animals; Benzothiazoles; Copper; Cysteinyldopa; Hair; Iron; Mammals; Oxidation-Reduction; Pigments, Biological; Thiazoles | 2002 |