Indole derivatives

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

“…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].…”

“…The respective 1,2-and 3,4-dihydro derivatives can also act as precursors of tetrahydro-γ-carbolines. Here the reduction of 1,2-dihydro-γ-carbolines is as a rule accomplished with hydrogen over Pd/C [6,13], whereas 3,4-dihydro-γ-carbolines can be reduced with hydrogen over platinum [17] or even with NaBH 4 in methanol [20].…”

“…Thus, 3,4-dihydro-γ-carbolines were synthesized from 2-acetamido-3-(2-indolyl)propionic acids 8a,b by the action of SOCl 2 [15,16]. Glutaric anhydride can be used as acylating agent for the isotryptamines 9 [17][18][19]; the reaction leads to the formation of the monoamide, which is transformed into the methyl ester 10 by the action of diazomethane. In reaction with POCl 3 the ester 10 undergoes cyclization to the substituted 3,4-dihydro-γ-carboline, which can be converted into the corresponding tetrahydro derivative by hydrogenation.…”

The synthesis and physiological activity of 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indoles

“…For example, compound 88 is prepared by the Bischler ± Napieralski cyclodehydration of indole 89, followed by hydrogenation of the dihydro-g-carboline 90 formed. 60 Similarly the reduction of 2,5-dihydropyridoindole 91 to 2-tert-butoxycarbonyl-5-methoxymethyl-2,3,4,5-tetrahydropyrido[4,3-b]indole 92 was accomplished. 61 Compound 91 is synthesized from indole 93 by a metathesis reaction in the presence of Grubbs' ruthenium catalysts (GC) that tolerate a wide range of functional groups under these conditions.…”

Simple synthesis of γ-carbolines

“…Thanks to the availability of tryptamine derivatives, electrophilic cyclizations of the Pictet-Spengler, Bischler-Napieralski and related type processes are widely used for the synthesis of β-carbolines [1]. Analogous reactions amongst methods for preparing γ-carbolines [2, 6-9] occupy a modest placement [10,11] and this is likely related to the lesser availability of the corresponding amines.…”