Indole oxidative cleavage

Oxidative dimerization of indoles has also been reported to be catalyzed by Tl(III) salts <78IJC(B)422), whilst Co(II) salts cause oxidative cleavage of indoles (79MI30503). 

Copper complexes are particularly effective catalysts for the oxidative cleavage of enamines (equation 284)613-615 and 3-substituted indoles (equation 285)6 6,617 under extremely mild conditions ( 0°C). 

Indole Groups. The indole group of tryptophan is susceptible to substitutions and to oxidative cleavage by several different reagents (see Figure 7). Less reactive than such nucleophiles as thiol and amino groups, and frequently located within the interior of protein molecules, tryptophans are unaffected by many commonly used reagents. 

A novel procedure for the oxidative cleavage of indole carbon double bonds in the presence of H2O2 using plant cell cultures, as a catalytic system, led to benzazonine diones 297 (Scheme 54) <2004TL8061>. 177-Benzo[ ][l,4]diazonines 298 were obtained in a highly substituted form and in high yields by ozonolysis of 1,2,3,4-tctrahydro-9//-pyrido[3,4- indole derivatives 296 (X = NAc) <2000JME3518>. 

Triphenylbismuth carbonate (2) displays remarkable chemoselecdvity, aUowing alcohol oxidation in the presence of benzenethiol, pyrrolidine, indole, aniline, dimethyl aniline and 3-pyrolidinocholesta-3,S-diene. The diol moiety in (3) is cleaved selectively without oxidizing the dithioacetal function (equation 3). The rate of the stoichiometric oxidative cleavage of ciJ-cyclohexane-l,2-diol to adipic aldehyde with Ph3BiC03 is faster than that of the trans isomer, suggesting the formation of a cyclic organobismuth intermediate (4 Scheme 1). ... 

An additional application of l-exo Heck cyclization was found in Kelly s synthesis of maxonine (223), which was isolated from the root of a plant Simira maxonii endemic to the Costa Rican tropical forest. As shown in Scheme 39, the migratory insertion step of the intramolecular Heck cyclization of substrate 220 took place to both the pendant olefin and the benzene ring of the indole moiety simultaneously, giving rise to dihydropyridine 221 and seven-membered 222, respectively [104]. Oxidative cleavage of the stilbene double bond in 222 produced maxonine (223), which was identical to authentic maxonine. Kelly s synthesis of maxonine (223) revised the original structural assignment of the natural indole alkaloid. 

The reactivity of the indole ring of tryptophan60 has attracted much interest and attention. This aromatic, electron-rich nucleus is susceptible to oxidative cleavage and to substitutions by a number of reagents. It can react as an electron donor with aldehydes or carbocations. 

The first step of tryptophan catabolism is the oxidative cleavage of the indole ring of L-tryptophan, which is catalyzed by members of the family of pyrrole dioxygenases. A key member of this family, indoleamine-2,3-dioxygenase (IDO, see Fig. 1, EC 1.13.11.17), is expressed in all tissues except in the liver and produces the central metabolite kynurenine (KYN). Two different and competing branches of the pathway then further metabolize KYN the first pathway includes a family of enzymes called kynurenine aminotransferases (KATs), which produce kynurenic acid (KYNA) in a terminal branch. In a second arm, KMO (or kynurenine... 

Oxidative cleavage of the indole 2,3-double bond can be achieved with ozone, sodium periodate, potassium superoxide, " with oxygen in the presence of cuprous chloride and with oxygen, photochemi-cally in ethanolic solution. ... 

In the Co(salen) catalyzed oxidative cleavage of 3-substituted indoles (35) to the corresponding o-formylaminophenyl ketone (36) in CH Cl at room temperature [210,211], the rate-determining step has... 

Many feeding experiments (72, 144) have established that, as monoterpenoid indole alkaloids, camptothecin is also generated from tryptamine and secola-ganin. From strictosidine, a nine-membered ring intermediate can be derived via strictosamide (73) by oxidative cleavage of the C2-C7 double bond. A C2--C6 condensation occurs and, finally, camptothecin, is generated (Fig. 5.2.21). 

Various convenient methods for the synthesis of protected indoles have been reported by several groups [7a-e]. Interesting C-H oxidative coupling reactions of various arenes with alkynes are shown in Eqs. (5.5)-(5.9). These methods allow quick access to a number of functional molecules in good yields via an N-N bond oxidative cleavage or use of an external oxidant. Excellent regioselectivity was achieved by using asymmetrically substituted alkynes. 

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