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Molecules 2008, 13(8), 1846-1863; doi:10.3390/molecules13081846
Article

Oligomerization of Indole Derivatives with Incorporation of Thiols

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1 Department of Pharmaceutical Biosciences, Division of Pharmaceutical Pharmacology, Uppsala Biomedical center, Uppsala University, S-751 24, Uppsala, Sweden 2 Latvian Institute of Organic Synthesis, Aizkraukles 21, LV-1006, Riga, Latvia 3 Department of Biochemistry and Organic Chemistry, Box 576, Uppsala University, S-751 23, Uppsala, Sweden
* Author to whom correspondence should be addressed.
Received: 10 June 2008 / Revised: 18 August 2008 / Accepted: 19 August 2008 / Published: 26 August 2008
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Abstract

Two molecules of indole derivative, e.g. indole-5-carboxylic acid, reacted with one molecule of thiol, e.g. 1,2-ethanedithiol, in the presence of trifluoroacetic acid to yield adducts such as 3-[2-(2-amino-5-carboxyphenyl)-1-(2-mercaptoethylthio)ethyl]-1Hindole-5-carboxylic acid. Parallel formation of dimers, such as 2,3-dihydro-1H,1'H-2,3'-biindole-5,5'-dicarboxylic acid and trimers, such as 3,3'-[2-(2-amino-5-carboxyphenyl) ethane-1,1-diyl]bis(1H-indole-5-carboxylic acid) of the indole derivatives was also observed. Reaction of a mixture of indole and indole-5-carboxylic acid with 2-phenylethanethiol proceeded in a regioselective way, affording 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H-indole-5-carboxylic acid. An additional product of this reaction was 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-2,3-dihydro-1H,1'H-2,3'-biindole-5'-carboxylic acid, which upon standing in DMSO-d6 solution gave 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H,1'H-2,3'-biindole-5'-carboxylic acid. Structures of all compounds were elucidated by NMR, and a mechanism for their formation was suggested.
Keywords: Side reaction; oligomerization of indole derivatives; incorporation of thiols; regioselectivity; NMR study Side reaction; oligomerization of indole derivatives; incorporation of thiols; regioselectivity; NMR study
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Mutulis, F.; Gogoll, A.; Mutule, I.; Yahorava, S.; Yahorau, A.; Liepinsh, E.; Wikberg, J.E. Oligomerization of Indole Derivatives with Incorporation of Thiols. Molecules 2008, 13, 1846-1863.

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