- Substrate Specificity and Regioselectivity of Tryptophan 7-Halogenase from Pseudomonas fluorescens BL915
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Tryptophan 7-halogenase which is involved in pyrrolnitrin biosynthesis is the first halogenating enzyme to be isolated that has substrate specificity and regioselectivity. This FADH2-dependent halogenase catalyzes the chlorination of its natural substrate tryptophan exclusively at the 7-position, a position at which direct chemical chlorination is not possible. Other substrates such as N-Ω-methyltryptamine, 5-methyltryptamine, 5-methylindole, 3-methylindole, or indole-3-acetonitrile are also chlorinated by the enzyme, whereas compounds like 1-methyltryptophan, indole-3-carboxylic acid, indole-3-acetic acid, or indole are not accepted as substrates. In addition, phenylpyrrole derivatives are also chlorinated by the enzyme. However, in contrast to tryptophan, the tryptophan and indole derivatives are chlorinated at positions 2 or/and 3 of the indole ring system and not at the 7-position. Chlorination of the phenylpyrrole derivatives also proceeds without regioselectivity and a mixture of mono- and dichlorinated products is obtained.
- Hoelzer, Manuela,Burd, Wassily,Reissig, Hans-Ulrich,Van Pee, Karl-Heinz
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- Halogenation of indoles with copper(II) halides: Selective synthesis of 2-halo-, 3-halo-, and 2,3-dibromoindoles
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A simple and selective protocol for the halogenation of indoles with copper(II) bromide or chloride to synthesize 2-halo-, 3-halo-, and 2,3-dibromoindoles was developed. It was found that both base and water could be used as switches for the selectivity of the halogenation reactions. In the presence of copper(II) halide and sodium hydroxide, 3-haloindoles were obtained as the major products, whereas the selectivity was shifted toward 2,3-dihaloindoles when water was added instead of sodium hydroxide. Moreover, 2-halogenations of 3-substituted indoles were also performed successfully in moderate to good yields under the standard conditions. Georg Thieme Verlag Stuttgart.
- Tang, Shi,Li, Jin-Heng,Xie, Ye-Xiang,Wang, Nai-Xing
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p. 1535 - 1541
(2008/02/08)
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- Reactivity of 3-substituted indolin-2-ones in Vilsmeier-type reactions of 4,6-dimethoxyindoles
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4,6-Dimethoxy-2,3-diphenylindole 1 undergoes reaction with the 3-substituted indolin-2-ones 7,8,11-14 and either phosphoryl chloride or triflic anhydride to give the 2,7'-biindolyl 16, the 7,7'; 2,7'-terindolyls 19, 20 and the 7,7'-biindolyl 23.
- Black, David St.C.,Ivory, Andrew J.,Kumar, Naresh
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p. 7003 - 7012
(2007/10/03)
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- The chlorination of indoles by copper(II) chloride
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The reaction of indoles with copper(II) chloride has been studied in acetonitrile.At low copper(II):indole ratios, dimers are formed in the presence of dioxygen, oxygenated products are obtained, and at large copper(II):indole ratios, pyrrole ring-chlorinated products are formed in yields of up to 92percent.The reactions are postulated to proceed via the radical cations of the indoles formed in an electron-transfer reaction.
- Balogh-Hergovich, Eva,Speier, Gabor
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p. 2305 - 2309
(2007/10/02)
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