3-Formyl-indole

Another approach to the l-oxo-l,2-dihydro-j8-carboline system is that due to King and Stiller. When 2-ethoxy carbonyl-3-formyl-indole is condensed with hippuric acid the azlactone 162 is formed, which, with 10% methanolic potassium hydroxide, gives a mixture of the orthoester 163 and the potassium salt 164. 

Benzyloxy-3-formyl-indol > 4-Benzyloxy-3-methyl-indoP 93% d.Th. F 83—84°... 

Bei der Gewinnung von Tryptophan bzw. Phenylalanin aus 3-Formyl-indol bzw. Benzaldehyd und 2,4-Dioxo-imidazolidin bedient man sich der elektrochemischen Re-duktion des zunachst entstehenden Methylen-Derivats I2 ... 

Formyl-indol bildet mit Chlor-diphenyl-phosphan entsprechend (Chlor-3-indolyl-me-thyl)-diphenyl-phosphanoxid in 71% Ausbeute88. Auch cyclische Chlorphosphane kon-nen erfolgreich mit Aldehyden umgesetzt werden z.B.89 ... 

Rcr 0-Cz> - coociHs R= H R = ch2-c,h, A 99-110 100 0.25 1 DMF 1,4- Dioxan 2-Ethoxy carbonyl-3-formyl-5-hydroxy-indol 5-Benzyloxy-2-ethoxycarbonyl-3- formyl-indol 77 99 250 432 4 33... 

N-(3-Indolylmethyl)-N-phenyl-hydroxylamin wird durch Nitrobenzol zum entsprechen-den Nitron oxidiert, dessen alkalisehe Hydrolyse 3-Formyl-indol liefert176. 

The Vilsmeier reaction is a very efficient method for the preparation of 3-formyl-indoles/° and for other 3-acyl-indoles using tertiary amides of other acids in place of dimethylformamide. Even indoles carrying an electron-withdrawing group at the 2-position, for example ethyl indole-2-carboxylate, undergo smooth Vilsmeier 3-formylation. ... 

Cwe-nucleophilic substitution of methoxy in a l-methoxy-3-formyl-indole produces the 2-substituted product. ... 

Whereas 2-formylthiophene and 3-formyl indole react with diethyl azodicarboxylate to give products arising from radical reactions at their respective formyl groups, 2-formylfuran gives a product derived from an initial 4+2 cycloaddition (Scheme 8) <9719313>. 

The reaction of N-protected 3-formyl and 3-acetylindole with ra-chloroperoxybenzoic acid has been investigated. 1-Benzenesulfonyl-3-formyl and 1-acetyl-3-formyl indoles gave modest yields of 3-indolones via hydrolysis of unstable formate esters. Some of the corresponding 2-hydroxyindol-3-ones were also formed. The 3-acetoxy derivative of 1-benzenesulfonylindole is more stable and was isolated in 80% yield from the oxidation of 3-acetyl-l-benzenesulfonylindole. <94S411>... 

Scheme 13.8 Visible-light-induced synthesis of 3-formyl Indole derivatives.

A general synthesis of tryptophan involves condensation of 3-formyl-indole with oxazolinones derived from N-acyl-glycine. Recently, Kirby and Varley 225) have used this method to synthesize tryptophan stereoselectively labelled with tritium and deuterium in the p-methylene group. The synthesis employed is depicted in the following scheme (21) to (24) and (25). The hydrogenation step leading to the racemate... 

Tritiated tryptophan has been prepared by catalytic dehalogenation of the 5-bromo-derivative by Birkofer and Hempel 44). Labelling with tritium at the a- 62) and P-carbon 318) of tryptophan has been reported. Kirby and Varley 225) prepared tryptophan stereoselectively labelled with tritium and deuterium at the p-methylene group by using labelled 3-formyl indole as a starting compound (see also Section II.2.). 

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