Indole derivatives

γ-Carbolines and their hydrogenated derivatives. 2.* Hydrogenated derivatives of γ-carbolines: methods of synthesis (review)

“…A decrease of branching at position 1 increases the yield of the hexahydro-γ-carboline. Replacement of the methyl radical at this position by phenyl does not have a substantial effect on the course of the reduction, which also leads to two reaction products, whereas 1,1-and 3,3-dimethyltetrahydro-γ-carbolines are only reduced to the corresponding hexahydro derivatives under these conditions [84]. Even in the case of 1,1,3-trimethyl-1,2,3,4-tetrahydro-γ-carboline only the hexahydro derivative is produced during reduction with a yield of 60% [68].…”

“…Thus, during the reduction of 1-phenyl-3,3-dimethyl-1,2,3,4-tetrahydro-γ-carboline with zinc dust both the corresponding hexahydro-γ-carboline 58 and 2-(2-aminosobutyl)indoline are formed [84]. The ratio of the reaction products depends on the arrangement of the alkyl substituents.…”

“…The medicinal drug Dicarbine 57b, which is the racemate of the cis isomer, was obtained similarly [120]. Tetrahydro-γ-carbolines polyalkylated in the piperideine ring are reduced by the action of zinc amalgam in hydrochloric acid to the hexahydro derivatives to an insignificant degree and mainly undergo reductive degradation with the formation of the corresponding indoline and isotryptamine derivatives [21,84,121] …”

“…The transformations take place under fairly mild conditions and with good yields of the required tetrahydro-γ-carboline compounds not substituted at positions 2 and 5 [17,22,[84][85][86][87] Intramolecular condensation takes place fairly smoothly both in an acetate buffer (pH 4.7) at room temperature [22] and when solutions of the isotryptamines hydrochlorides in the benzene-ethanol-water ternary system are boiled [84]. If glyoxalic acid is used it is possible to obtain tetrahydro-γ-carboline-1-carboxylic acid with a good yield from isotryptamines under very mild conditions [86].…”

Carbolines. Part 2: Comparison of some of the properties of α-, γ-, and δ-carbolines (Review)

“…Studies of the reduction of a series of polyalkyl-substituted tetrahydro-g-carbolines 37a-d with zinc powder in a mixture of hydrochloric acid and alcohol supplemented with mercuric chloride showed that formation of the corresponding hexahydro derivatives 38b-d was accompanied by formation of 2-(b-aminoisobutyl)indoline derivatives 39a-d due to destruction of the piperidine ring (Scheme 11) [24]. …”