Psilocin analogs. III. Synthesis of 5-methoxy- and 5-hydroxy-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indoles

A Review of Synthetic Access to Therapeutic Compounds Extracted from Psilocybe

Psychedelics are used for various pathologies of the central nervous system and are currently the subject of much research, some of which relates to the compounds contained in various Psilocybe-type hallucinogenic mushrooms. It is difficult, however, to obtain and purify sufficient quantities of these compounds from fungi to carry out biological studies, hence the need to develop simple and efficient synthetic routes. We review here the various syntheses used to obtain these molecules, focusing first on the classic historical syntheses, then the use of more recent metallo-catalyzed couplings and finally the known biocatalytic methods for obtaining these molecules. Other access routes are certainly possible and should be the subject of future research given the therapeutic interest of these compounds.

Microwave assisted Leimgruber-Batcho reaction for the preparation of indoles, azaindoles and pyrroylquinolines

The development of enhanced conditions for Lewis acid catalysed Leimgruber-Batcho indole synthesis using microwave acceleration is described. This approach has permitted the preparation of a variety of heteroaromatic enamine intermediates in good yield and high purities. Subsequent catalytic hydrogenation reactions, under various conditions including the use of a solid-phase encapsulated catalyst, furnish the corresponding indole derivatives in good yields.

Binding of β-Carbolines at 5-HT 2 serotonin receptors

A series of ring-substituted (i.e., methoxy and bromo) 3,4-dihydro- and 1,2,3,4-tetrahydro-beta-carbolines was examined at 5-HT(2A) and 5-HT(2C) serotonin receptors. Whereas most of the methoxy-substituted derivatives typically displayed affinities similar to their unsubstituted parents, certain (particularly 8-substituted) bromo derivatives displayed enhanced affinity. A binding profile was obtained for selected beta-carbolines.

Preparation of the 4-hydroxytryptamine scaffold via palladium-catalyzed cyclization: a practical and versatile synthesis of psilocin

[reaction: see text] The 4-hydroxytryptamine scaffold of psilocin was successfully prepared via palladium-catalyzed cyclization of protected N-tert-butoxycarbonyl-2-iodo-3-methoxyaniline and an appropriately substituted silyl acetylene. Removal of the protecting groups afforded psilocin in good yield.

Syntheses of Tantalum(V) Complexes Containing Tetramethylpyrrolyl, Pyrrolyl, and Indolyl Ligands

The reaction of TaMe(3)Cl(2) with the lithium salt of tetramethylpyrrole (Li-TMP) led to the formation of (eta(5)-TMP)TaMe(3)Cl (1). Reactions of 1 with a series of anionic ligands have been carried out to form products of the formula (eta(5)-TMP)TaMe(3)X, where X = SR, Me, pyrrolyl, or indolyl. Crystals of (eta(5)-TMP)TaMe(3)(indolyl) (5), were isolated in space group P2(1)/c with a = 8.957(2) Å, b = 28.540(6) Å, c = 14.695(3) Å, beta = 99.40(3) degrees, V = 3706.1(14) Å(3), and Z = 8. The structure confirmed the eta(5)-bonding mode of the tetramethylpyrrolyl ligand and the eta(1)-N-coordination mode of the indolyl ligand.The derivatives (eta(5)-TMP)TaMe(3)X showed limited stability, and decomposition products which formed in toluene solutions at room temperature have been identified in some cases. The reaction of (eta(5)-TMP)TaMe(3)(pyrrolyl) with hydrogen (2-3 atm) in benzene-d(6) solution at room temperature was studied. The stoichiometric formation of cyclohexane-d(6) by hydrogenation of an equivalent of solvent was confirmed by (1)H and (13)C NMR and gas chromatographic/mass spectroscopic data. The characteristics and scope of the room temperature arene hydrogenation process are discussed.

In vitro study of the aromatic hydroxylation of 1-methyltetrahydro-beta-carboline (methtryptoline) in rat

The incubation of 1-methyltetrahydro-beta-carboline (1-MeTHBC) with hepatocytes isolated from 3-methylcholanthrene-treated rats led to formation of the 5-, 6- and 7-hydroxylated products. The hydroxylating activity was associated with the microsomal fraction as indicated by testing different subcellular fractions. The highest activity for hydroxylating 1-MeTHBC was found in liver which was about ten times as active as lung. Only a trace amount of hydroxylating activity was present in brain and kidney tissue. Analysis using chiral gas chromatography revealed an unequal abundance of enantiomers in all three products. The formation of the 5-, 6- and 7-hydroxylated products was confirmed in vivo by analysis of 24 h urine samples after intraperitoneal administration of 1-MeTHBC to 3-methylcholanthrene-treated rats.

6-Hydroxymethtryptoline is naturally occurring in mammalian urine: identification by combined chiral capillary gas chromatography and high resolution mass spectrometry

The tricyclic indole derivative 6-hydroxymethtryptoline (7-hydroxy-1-methyltetrahydro-beta-carboline) was identified as a normal constituent of human and cat urine. The identification was based on the correct retention time on a chiral capillary gas chromatographic column and on selected ion monitoring of the molecular ion with the mass spectrometer set at high resolving power (RP 10,000). The quantitation utilized a 13C-labeled analog as internal standard and demonstrated levels of 135 +/- 35 and 174 +/- 42 (pmol ml-1, mean +/- SEM) for the S(-) and R(+) enantiomers, respectively, in human urine. In cat urine, the levels were 203 +/- 55 and 108 +/- 44 (pmol ml-1, mean +/- SEM) for the S(-) and R(+) enantiomers, respectively. In human urine, the compound occurred predominantly in a conjugated form while in cat urine the free compound predominated. It was concluded that 6-hydroxymethtryptoline is naturally occurring in mammalian urine and that it most likely constitutes a metabolite of endogenous methtryptoline (1-methyltetrahydro-beta-carboline).

Rapid hydroxylation of methtryptoline (1-methyltetrahydro-beta-carboline) in rat: identification of metabolites by chiral gas chromatography-mass spectrometry

Racemic methtryptoline (1-methyltetrahydro-beta-carboline) and 5-hydroxymethtryptoline-9-carboxylic acid (6-hydroxy-1-methyltetrahydro-beta-carboline-1-carboxylic acid) were administered intraperitoneally to rats and the components of their urine was subsequently investigated by chiral gas chromatography-mass spectrometry. Methtryptoline rapidly became hydroxylated in the 5- and 6-position and excreted in urine. There was about a ninefold predominance of the S(-) enantiomer over the other in the 5-hydroxylated species, while the 6-hydroxylation produced a small excess of the R(+) enantiomer. About 75% of the injected dose of methtryptoline was recovered in the urine as 5- and 6-hydroxylated compounds during the first 24 h period, demonstrating that hydroxylation represents the major metabolic pathway. Treatment with 6-hydroxymethtryptoline-9-carboxylic acid led to a fivefold increase in the urinary excretion of 5-hydroxymethtryptoline during the first 24 h period with a predominance of the S(-)-enantiomer, indicating a much smaller conversion rate than from methtryptoline. It was concluded that hydroxylation of methtryptoline is a likely pathway for the natural formation of 5-hydroxymethtryptoline.

[Simple compounds with high pharmacologic potential: beta-carbolines. Origins, syntheses, biological properties]

We reviewed the origins, the synthetic pathways and the biological properties of beta-carbolines, the condensation products of tryptophan and indole alkylamines with aldehydes. They were found in many plants, some of which have been used as hallucinogens. They also occur as minor constituents in tobacco smoke. In mammalian body, beta-carboline derivatives occur normally in plasma, platelets and urine, moreover it seems that some are formed in human body after alcohol intake. Due to interesting biological effects described in recent years (inhibition of monoamine oxidase, binding to benzodiazepine receptors, comutagenic and carcinogenic properties, 5-hydroxy tryptamine uptake inhibition), many attempts were made to prepare beta-carbolines starting from various indole derivatives. We reviewed the published methods up to 1975 and summarized the main patents related with pharmacological properties of synthetic beta-carbolines.