Quaternary tryptammonium salts: N,N-dimethyl-N-n-propyl-tryptammonium (DMPT) iodide and N-allyl-N,N-di-methyl-tryptammonium (DMALT) iodide

Synthesis, Structural Characterization, and Pharmacological Activity of Novel Quaternary Salts of 4-Substituted Tryptamines

Aeruginascin (4-phosphoryloxy-N,N,N-trimethyltryptammonium) is an analogue of psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) that has been identified in several species of psilocybin-containing mushrooms. Our team previously reported the synthesis, structural characterization, and biological activity of the putative metabolite of aeruginascin (4-hydroxy-N,N,N-trimethyltryptammonium; 4-HO-TMT) and its potential prodrug (4-acetoxy-N,N,N-trimethyltryptammonium; 4-AcO-TMT). Here, we report the synthesis, structural characterization, and pharmacological activity of several quaternary tryptammonium analogues of 4-HO-TMT and 4-AcO-TMT, namely, 4-hydroxy-N,N-dimethyl-N-ethyltryptammonium (4-HO-DMET), 4-hydroxy-N,N-dimethyl-N-n-propyltryptammonium (4-HO-DMPT), and 4-hydroxy-N,N-dimethyl-N-isopropyltryptammonium (4-HO-DMiPT), as well as their hypothesized prodrugs 4-acetoxy-N,N-dimethyl-N-ethyltryptammonium (4-AcO-DMET), 4-acetoxy-N,N-dimethyl-N-n-propyltryptammonium (4-AcO-DMPT), and 4-acetoxy-N,N-dimethyl-N-isopropyltryptammonium (4-AcO-DMiPT). Compounds were synthesized using established methods, and structures were characterized by single-crystal X-ray diffraction. Test compounds were screened for in vitro pharmacological activity at a variety of receptors and transporters to determine potential targets of action. None of the compounds exhibited measurable affinity for the serotonin 2A receptor (5-HT2A), but several analogues had low micromolar affinity (K i) for the serotonin 1D receptor (5-HT1D) and serotonin 2B receptor (5-HT2B), where they appeared to be weak partial agonists with low micromolar potencies. Importantly, 4-HO-DMET, 4-HO-DMPT, and 4-HO-DMiPT displayed sub-micromolar affinity for the serotonin transporter (SERT; 370-890 nM). The same 4-hydroxy analogues had low to sub-micromolar potencies (IC50) for inhibition of 5-HT uptake at SERT in transfected cells (3.3-12.3 μM) and rat brain tissue (0.31-3.5 μM). Overall, our results show that quaternary tryptammonium analogues do not target 5-HT2A sites, suggesting the compounds lack psychedelic-like subjective effects. However, certain 4-hydroxy quaternary tryptammonium analogues may provide novel templates for exploring structure-activity relationships for selective actions at SERT.

Bufotenidinium iodide

The structure of the natural product bufotenidine is reported as its iodide salt.

The title compound, 5-hy­droxy-N,N,N-tri­methyl­tryptammonium (5-HTQ) iodide {systematic name: [2-(5-hy­droxy-1H-indol-3-yl)eth­yl]tri­methyl­aza­nium iodide}, C₁₃H₁₉N₂O⁺·I⁻, has a single tryptammonium cation and one iodide anion in the asymmetric unit. The ions are held together by N—H⋯I and O—H⋯I hydrogen bonds in infinite chains along [100].

2,5-Di-methyl-bufo-tenine and 2,5-di-methyl-bufo-teni-dine: novel derivatives of natural tryptamines found in Bufo alvarius toads

The solid-state structure of the bufotenine derivative bis-(5-meth-oxy-2,N,N-tri-methyl-tryptammonium) (5-MeO-2-Me-DMT) fumarate (systematic name: bis-{[2-(5-meth-oxy-2-methyl-1H-indol-3-yl)eth-yl]di-methyl-aza-nium} (2E)-but-2-enedioate), 2C14H21N2O+·C4H2O4 2-, the bufotenidine derivative 5-meth-oxy-2,N,N,N-tetra-methyl-tryptammonium (5-MeO-2-Me-TMT) iodide {systematic name: [2-(5-meth-oxy-2-methyl-1H-indol-3-yl)eth-yl]tri-methyl-aza-nium iodide}, C15H23N2O+·I-, and the hydrate of the same {systematic name: [2-(5-meth-oxy-2-methyl-1H-indol-3-yl)eth-yl]tri-methyl-aza-nium iodide monohydrate}, C15H23N2O+·I-·H2O, are reported. The structure of 5-MeO-2-Me-DMT fumarate possesses one tryptammonium cation and a half of a fumarate dianion in the asymmetric unit, linked together by N-H⋯O hydrogen bonds in infinite two-dimensional networks parallel to the (101) plane. The structure of 5-MeO-2-Me-TMT iodide possesses one tryptammonium cation and one iodide anion in the asymmetric unit. The ions are linked via N-H⋯I hydrogen bonds, and indoles are coupled in dimers through π-π inter-actions. The hydrate of 5-MeO-2-Me-TMT iodide possesses one tryptammonium cation, one iodide anion and one water mol-ecule in the asymmetric unit. It shows N-H⋯I and O-H⋯I hydrogen bonds that couple the tryptammonium cations into dimers.