- MUSHROOM TYROSINASE AS AN OXIDANT FOR THE SYNTHESIS OF 5,6-DIHYDROXYINDOLE DERIVATIVES
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Several catecholamines have been converted to 5,6-diacetoxyindole derivatives by the use of mushroom tyrosinase as oxidant.
- Lim, Mu-Ill,Patil, Dilip G.
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- The first entry to 5,6-dihydroxy-3-mercaptoindole, 5-hydroxy-3-mercaptoindole and their 2-carbomethoxy derivatives by a mild thiocyanation/reduction methodology
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The hitherto unknown 5,6-dihydroxy-3-mercaptoindole (4a) and its 2-carbomethoxy derivative (4b), as well as the analogous 5-hydroxy 3-mercaptoindoles, have been conveniently obtained as O,S-acetyl derivatives 3a-d by thiocyanation of the corresponding acetoxyindoles 1a-d with the NH4SCN/oxone system followed by SmI2 reduction and acetylation.
- Pezzella, Alessandro,Palma, Aniello,Iadonisi, Alfonso,Napolitano, Alessandra,d'Ischia, Marco
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- New insight into the oxidative chemistry of noradrenaline: Competitive o-quinone cyclisation and chain fission routes leading to an unusual 4-[bis-(1H-5,6-dihydroxyindol-2-yl)methyl]-1,2-dihydroxybenzene derivative
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Oxidation of 5×10-3 M noradrenaline in aqueous phosphate buffer, pH 7.4, with K3Fe(CN)6, NaIO4 or Fe2+/EDTA/H2O2 followed by extraction with ethyl acetate and acetylation with Ac2O/Pyr led to a main reaction product which was isolated and identified as 4-[bis-(1H-5,6-diacetoxyindol-2-yl) methyl]-1,2-diacetoxybenzene, an unprecedented [bis-(indol-2-yl)methyl]-benzene derivative unsubstituted on the 3-position of the indole rings. This product was also obtained in 40% yield by reaction of 5,6-dihydroxyindole with 3,4-dihydroxybenzaldehyde. Other components of the oxidation mixture were 1-acetyl-3,5,6-triacetoxyindole, derived from noradrenolutin, and 5,6-diacetoxyindole, originating from cyclisation/dehydration of the o-quinone of noradrenaline, along with some 3,4-diacetoxybenzaldehyde. Inspection of the aqueous phase revealed the presence of 3,4-dihydroxymandelic acid and 3,4-dihydroxybenzaldehyde, derived from oxidative breakdown of the 2-amino-1-hydroxyethyl chain via a p-quinomethane intermediate. These results disclose new aspects of the oxidative chemistry of noradrenaline beyond the aminochrome stage and provide a route to novel [bis-(indol-2-yl)methyl]-benzene derivatives of potential pharmacological interest.
- Manini, Paola,Pezzella, Alessandro,Panzella, Lucia,Napolitano, Alessandra,D'Ischia, Marco
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- Free radical coupling of o -semiquinones uncovered
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As a rule, o-semiquinones decay through disproportionation leading to equimolar amounts of catechol and o-quinone products. However, the o-semiquinone 1S generated by pulse radiolysis oxidation of the eumelanin precursor 5,6-dihydroxyindole (1) decays wit
- Pezzella, Alessandro,Crescenzi, Orlando,Panzella, Lucia,Napolitano, Alessandra,Land, Edward J.,Barone, Vincenzo,D'Ischia, Marco
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supporting information
p. 12142 - 12149
(2013/09/02)
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- Efficient synthesis of 5,6-dihydroxyindole dimers, key eumelanin building blocks, by a unified o-ethynylaniline-based strategy for the construction of 2-linked biindolyl scaffolds
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(Chemical Equation Presented) A unified convenient strategy for the synthesis of 5,6-dihydroxyindole-derived 2,7′-, 2,2′-, and 2,3′-biindolyls is reported, which is based on proper manipulation of key o-ethynylaniline precursors. By the same methodology 5
- Capelli, Luigia,Manini, Paola,Pezzella, Alessandro,Napolitano, Alessandra,D'Ischia, Marco
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supporting information; experimental part
p. 7191 - 7194
(2009/12/09)
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- Synthesis of Acetoxy Stabilised Indolequinones as Precursors to Model Eumelanin Polymers
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We report an efficient synthetic route to obtaining a stable analogue of 5,6-dihydroxyindole. These analogues can be used to build controlled composition model melanin biopolymers for solid state and spectroscopic studies of this important biomolecule.
- Atkinson, Sov,Meredith, Paul
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p. 1853 - 1855
(2007/10/03)
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- Expedient synthesis of 5,6-dihydroxyindole and derivatives via an improved Zn(II)-assisted 2,β-dinitrostyrene approach
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A facile 3-step synthesis of 5,6-dihydroxyindole (4a) is reported, featuring the Zn(II)-controlled regioselective nitration of 3,4- dihydroxynitrostyrene (2) with tetranitromethane at pH 8.0, and the reductive cyclization of the resulting 4,5-dihydroxy-2,β-dinitrostyrene (3a) with Na2S2O4/Zn(II) at pH 4. The latter procedure was successfully extended to the conversion of the 2,β-dinitrostyrenes 3b and 3c to 5,6-dibenzyloxyindole (4b) and 5,6-diacetoxyindole (4c) in good-to-high yields.
- Novellino, Luisa,D'Ischia, Marco,Prota, Giuseppe
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p. 793 - 796
(2007/10/03)
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- Product based on inorganic or organic lamellar particles, containing a melanotic pigment, process for preparing it and its use in cosmetics
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The invention relates to a product in powder form consisting of organic or inorganic particles having a lamellar structure, having a size of less than 50 microns and containing at least one synthetic melanotic pigment formed in situ by oxidation of an indole compound, and to its use for the protection of the human epidermis, in make-up products and for dyeing hair.
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- Process for the preparation of 5,6-diacetoxyindole
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An indole of the formula STR1 wherein R5 and R6 are acetoxy or hydrogen, at least one of R5 and R6 being acetoxy, is prepared, in good yield, in a one pot synthesis, without extraction, recrystallization or isolation of intermediate reaction product; A compound of the formula STR2 wherein R1 and R2 are benzyloxy or hydrogen, provided that at least one of R1 and R2 is benzyloxy, is subjected to reductive cyclization followed by acetylation of the resultant reaction product.
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- A NEW INTERMEDIATE IN THE TYROSINASE-CATALYZED CONVERSION OF TYROSINE TO MELANINE
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Reduction an subsequent acetylation of the products formed in the early stages of melanogenesis in vivo lead to the isolation, besides 5,6-diacetoxyindole and 5,6-diacetoxyindole-2-carboxylic acid, of a hitherto unknown dimeric derivative 3, probably arising from a 5,6-dihydroxyindole-dopachrome intermediate such as 4.
- Corradini, Maria Grazia,Prota, Giuseppe
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p. 627 - 628
(2007/10/02)
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