Indole production

This test consists of incubating cells in a medium containing the amino acid tryptophan and measuring the production of indole. A culture 2-3 days old is added to Kovacs reagent (dimethylaminobenzaldehyde in HCl) and a pink/red colour gives a positive reaction. E. coli gives a positive result, and the test is frequently used to distinguish it from Klebsiella. 

The combination of Indole, Methyl Red, Voges-Proskauer and Citrate tests is frequently known under the acronym IMViC. 

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Entry Indole Product Oxidation conditions Yield (%) Ref. 

In the arylations of enamines with very reactive aryl halides (352,370) such as 2,4-dinitrochlorobenzene, the closely related mechanistic pathway of addition of the enamine to the aromatic system, followed by elimination of halide ion, can be assumed. The use of n-nitroarylhalides furnishes compounds which can be converted to indolic products by reductive cycliza-tion. Less reactive aryl halides, such as p-nitrochlorobenzene, lead only to N-arylation or oxidation products of the enamines under more vigorous conditions. 

In 1989, Bartoli reported that vinylmagnesium bromide reacted with 2-nitrotoluene (4) at -40 C in THF to furnish 7-methylindole (5) in 67% yield. The reaction process also proceeded well with other 2-substituted nitrobenzenes. However, the 3- or 4-substituted nitrobenzenes provided either no indole products or indoles in poor yield. ... 

Cyclization of an o-substituted arylhydrazone provides one isomer in many cases. However, the cyclization is more sluggish than the m- or p-substituted analogs. Sometimes the cyclization gives low yields of the desired indole products along with side products. Cyclization of the 2-substituted arylhydrazone can occur either to the unsubstituted side to provide the normal indole product (50), or to the substituted side, where other reactions take place (53 and 56). 

The best yields of 5-hydroxyindoles are obtained when equimolar amounts of the quinone and enamine are used. An excess of enamine gives rise to non-indolic products derived from reaction of two enamine units and one quinone unit or the product which results from the initial Michael addition of the enamine to the quinone. Use of excess quinone has been reported less frequently, but limited studies indicate no advantage. When 2,5-dichloro-l,4-benzoquinone (32) was treated with a 50% excess of ethyl 3-... 

The effectiveness of nitromethane can be attributed to its high dielectric constant, at least in part, which tends to promote reactions which involve electron-rich intermediates. It may also result from the low solubility of the indole products in nitromethane since the indoles precipitate out of the reaction mixture in many cases. ... 

However, thermolysis of the phosphonium salts (X=+PPh3) leads directly to the indolic products without need of acid catalyst or PPh3, and thus may not proceed via a normal Wittig pathway. Alternatively, Hughes has effected a solid-phase version of this reaction employing a polymer-hound phosphonium salt and potassium tert-butoxide as base <96TL7595>. In this case, the phosphine oxide by-product remains bound to the polymer resin. 

To assess the trapping of biological nucleophiles, the pyrido[l,2-a]indole cyclopropyl quinone methide was generated in the presence of 5 -dGMP. The reaction afforded a mixture of phosphate adducts that could not be separated by reverse-phase chromatography (Fig. 7.16). The 13C-NMR spectrum of the purified mixture shown in Fig. 7.16 reveals that the pyrido [1,2-a] indole was the major product with trace amounts of azepino[l,2-a] indole present. Since the stereoelec-tronic effect favors either product, steric effects must dictate nucleophilic attack at the least hindered cyclopropane carbon to afford the pyrido[l,2-a]indole product. Both adducts were stable with elimination and aromatization not observed. In fact, the pyrido [1,2-a] indole precursor (structure shown in Scheme 7.14) to the pyrido [l,2-a]indole cyclopropyl quinone methide possesses cytotoxic and cytostatic properties not observed with the pyrrolo [1,2-a] indole precursor.47... 

Goodacre, R. Kell, D. B. Rapid and quantitative analysis of bioprocesses using pyrolysis mass spectrometry and neural networks—Application to indole production. Anal. Chim. Acta 1993, 279,17-26. 

Somei adapted this chemistry to syntheses of (+)-norchanoclavine-I, ( )-chanoclavine-I, ( )-isochanoclavine-I, ( )-agroclavine, and related indoles [243-245, 248]. Extension of this Heck reaction to 7-iodoindoline and 2-methyl-3-buten-2-ol led to a synthesis of the alkaloid annonidine A [247]. In contrast to the uneventful Heck chemistry of allylic alcohols with 4-haloindoles, reaction of thallated indole 186 with 2-methyl-4-trimethylsilyl-3-butyn-2-ol affords an unusual l-oxa-2-sila-3-cyclopentene indole product [249]. Hegedus was also an early pioneer in exploring Heck reactions of haloindoles [250-252], Thus, reaction of 4-bromo-l-(4-toluenesulfonyl)indole (11) under Heck conditions affords 4-substituted indoles 222 [250], Murakami described the same reaction with ethyl acrylate [83], and 2-iodo-5-(and 7-) azaindoles undergo a Heck reaction with methyl acrylate [19]. 

Reaction of 4-cyanophenylhydrazine hydrochloride (70) with 4-benzoyloxycyclohexanone in refluxing acetic acid furnished the Fischer indole product... 

The reduction of adrenochrome (1) with ascorbic acid (59) was first reported in 1948,158 although the nature of the reaction products (which may be of physiological importance, cf. ref. 159) was not determined until several years later. It was shown by Heacock and Laidlaw in 1958 that reduction mixtures of this type contained at least three indolic products,147 one of which was isolated and shown to be 5,6-dihydroxy- -methylindole (28).147 The major component of aqueous adrenochrome-ascorbic acid reaction mixtures has recently been shown to be a secondary product (60) (which was isolated as its di- and tetra-acetyl derivatives) produced by the interaction of the o-dihydroxy group of 28 with the a-dicarbonyl function of dehydro-... 

Gierl, A. and Frey, M. 2001. Evolution of benzoxazinone biosynthesis and indole production in maize. Planta 213, 493-498... 

The structures of cleavamine and velbanamine are considered here since they are probably derived from precursors with the iboga skeleton. Cleavamine (XLVII), mp 109°-113°, [a]D +56° (CHCI3), was obtained along with deacetylvindoline when leurosine (structure unknown but closely related to XLI) was refluxed with concentrated hydrochloric acid, stannous chloride, and tin (42). Velbanamine (XLVIII), mp 139°-141°, [a]D +56° (CHCI3), was the indolic product when vincaleuko-blastine (XLI R = Me) or leurocristine (XLI R = CHO) were treated in the same way (42). Aside from the question of the mode of fission of the dimers (XLI), the production of the new tetracyclic systems in XLVII and XLVIII can be regarded as proceeding via a reverse Mannich... 

Rhodium(ll)-catalyzed decomposition of the diazoamide 235 has been shown to provide the indole 236 (Equation 74). In contrast, attempts involving Rh2(OAc)4 failed to give indolic products <1996T2489>. Decomposition of related substrates induced by zeolite K/3 leads to formation of oxindoles <1996J(P1)2793>. 

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