Biomimetic oxidn. of the pheomelanin precursor 5-S-cysteinyldopa in the presence of Zn2+ 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 Et ester/ethoxycarbonyl isoquinolines 8 and 9. Compd. 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 chem. degrdn. a thiazolylpyridinecarboxylic acid fragment. Model chem. studies allowed the proposal of a formation mechanism for the benzothiazole and dihydroisoquinoline systems in compd. 5.
Uncovering the structure of human red hair pheomelanin: benzothiazolylthiazinodihydroisoquinolines as key building blocks
d'Ischia M.;
2011
Abstract
Biomimetic oxidn. of the pheomelanin precursor 5-S-cysteinyldopa in the presence of Zn2+ 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 Et ester/ethoxycarbonyl isoquinolines 8 and 9. Compd. 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 chem. degrdn. a thiazolylpyridinecarboxylic acid fragment. Model chem. studies allowed the proposal of a formation mechanism for the benzothiazole and dihydroisoquinoline systems in compd. 5.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
