Enantiospecific synthesis and pharmacological evaluation of a series of super-potent, conformationally restricted 5-HT(2A/2C) receptor agonists

Serotonin 2A Receptor (5-HT2AR) Agonists: Psychedelics and Non-Hallucinogenic Analogues as Emerging Antidepressants

Psychedelics make up a group of psychoactive compounds that induce hallucinogenic effects by activating the serotonin 2A receptor (5-HT2AR). Clinical trials have demonstrated the traditional psychedelic substances like psilocybin as a class of rapid-acting and long-lasting antidepressants. However, there is a pressing need for rationally designed 5-HT2AR agonists that possess optimal pharmacological profiles in order to fully reveal the therapeutic potential of these agonists and identify safer drug candidates devoid of hallucinogenic effects. This Perspective provides an overview of the structure-activity relationships of existing 5-HT2AR agonists based on their chemical classifications and discusses recent advancements in understanding their molecular pharmacology at a structural level. The encouraging clinical outcomes of psychedelics in depression treatment have sparked drug discovery endeavors aimed at developing novel 5-HT2AR agonists with improved subtype selectivity and signaling bias properties, which could serve as safer and potentially nonhallucinogenic antidepressants. These efforts can be significantly expedited through the utilization of structure-based methods and functional selectivity-directed screening.

Design, Synthesis, Molecular Docking, and Biological Evaluation of Novel Pimavanserin-Based Analogues as Potential Serotonin 5-HT2A Receptor Inverse Agonists

There is concern for important adverse effects with use of second-generation antipsychotics in Parkinson's disease psychosis (PDP) and dementia-related psychosis. Pimavanserin is the only antipsychotic drug authorized for PDP and represents an inverse agonist of 5-HT_2A receptors (5-HT2AR) lacking affinity for dopamine receptors. Therefore, the development of serotonin 5-HT2AR inverse agonists without dopaminergic activity represents a challenge for different neuropsychiatric disorders. Using ligand-based drug design, we discovered a novel structure of pimavanserin analogues (2, 3, and 4). In vitro competition receptor binding and functional G protein coupling assays demonstrated that compounds 2, 3, and 4 showed higher potency than pimavanserin as 5-HT2AR inverse agonists in the human brain cortex and recombinant cells. To assess the effect of molecular substituents for selectivity and inverse agonism at 5-HT2ARs, molecular docking and in silico predicted physicochemical parameters were performed. Docking studies were in agreement with in vitro screenings and the results resembled pimavanserin.

Receptor Interaction Profiles of 4-Alkoxy-3,5-Dimethoxy-Phenethylamines (Mescaline Derivatives) and Related Amphetamines

3,4,5-Trimethoxyphenethylamine (mescaline) is a psychedelic alkaloid found in peyote cactus. Related 4-alkoxy-3,5-dimethoxy-substituted phenethylamines (scalines) and amphetamines (3C-scalines) are reported to induce similarly potent psychedelic effects and are therefore potential novel therapeutics for psychedelic-assisted therapy. Herein, several pharmacologically uninvestigated scalines and 3C-scalines were examined at key monoamine targets in vitro. Binding affinity at human serotonergic 5-HT_1A, 5-HT_2A, and 5-HT_2C, adrenergic α_1A and α_2A, and dopaminergic D₂ receptors, rat and mouse trace amine-associated receptor 1 (TAAR1), and human monoamine transporters were assessed using target specific transfected cells. Furthermore, activation of human 5-HT_2A and 5-HT_2B receptors, and TAAR1 was examined. Generally, scalines and 3C-scalines bound with weak to moderately high affinity to the 5-HT_2A receptor (K_i = 150–12,000 nM). 3C-scalines showed a marginal preference for the 5-HT_2A vs the 5-HT_2C and 5-HT_1A receptors whereas no preference was observed for the scalines. Extending the 4-alkoxy substituent increased 5-HT_2A and 5-HT_2C receptors binding affinities, and enhanced activation potency and efficacy at the 5-HT_2A but not at the 5-HT_2B receptor. Introduction of fluorinated 4-alkoxy substituents generally increased 5-HT_2A and 5-HT_2C receptors binding affinities and increased the activation potency and efficacy at the 5-HT_2A and 5-HT_2B receptors. Overall, no potent affinity was observed at non-serotonergic targets. As observed for other psychedelics, scalines and 3C-scalines interacted with the 5-HT_2A and 5-HT_2C receptors and bound with higher affinities (up to 63-fold and 34-fold increase, respectively) when compared to mescaline.

In vitro assays for the functional characterization of (psychedelic) substances at the serotonin receptor 5-HT2A R

Serotonergic psychedelics are substances that induce alterations in mood, perception, and thought, and have the activation of serotonin (5-HT) 2A receptors (5-HT_2A Rs) as a main pharmacological mechanism. Besides their appearance on the (illicit) drug market, e.g. as new psychoactive substances, their potential therapeutic application is increasingly explored. This group of substances demonstrates a broad structural variety, leading to insufficiently described structure-activity relationships, hence illustrating the need for better functional characterization. This review therefore elaborates on the in vitro molecular techniques that have been used the most abundantly for the characterization of (psychedelic) 5-HT_2A R agonists. More specifically, this review covers assays to monitor the canonical G protein signaling pathway (e.g. measuring G protein recruitment/activation, inositol phosphate accumulation, or Ca²⁺ mobilization), assays to monitor non-canonical G protein signaling (such as arachidonic acid release), assays to monitor β-arrestin recruitment or signaling, and assays to monitor receptor conformational changes. In particular, focus lies on the mechanism behind the techniques, and the specific advantages and challenges that are associated with these. Additionally, several variables are discussed that one should consider when attempting to compare functional outcomes from different studies, both linked to the specific assay mechanism and linked to its specific execution, as these may heavily impact the assay outcome.

2C-B-Fly-NBOMe Metabolites in Rat Urine, Human Liver Microsomes and C. elegans: Confirmation with Synthesized Analytical Standards

Compounds from the N-benzylphenethylamine (NBPEA) class of novel psychoactive substances are being increasingly utilized in neurobiological and clinical research, as diagnostic tools, or for recreational purposes. To understand the pharmacology, safety, or potential toxicity of these substances, elucidating their metabolic fate is therefore of the utmost interest. Several studies on NBPEA metabolism have emerged, but scarce information about substances with a tetrahydrobenzodifuran ("Fly") moiety is available. Here, we investigated the metabolism of 2-(8-bromo-2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran-4-yl)-N-(2-methoxybenzyl)ethan-1-amine (2C-B-Fly-NBOMe) in three different systems: isolated human liver microsomes, Cunninghamella elegans mycelium, and in rats in vivo. Phase I and II metabolites of 2C-B-Fly-NBOMe were first detected in an untargeted screening and identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Several hypothesized metabolites were then synthesized as reference standards; knowledge of their fragmentation patterns was utilized for confirmation or tentative identification of isomers. Altogether, thirty-five phase I and nine phase II 2C-B-Fly-NBOMe metabolites were detected. Major detected metabolic pathways were mono- and poly-hydroxylation, O-demethylation, oxidative debromination, and to a lesser extent also N-demethoxybenzylation, followed by glucuronidation and/or N-acetylation. Differences were observed for the three used media. The highest number of metabolites and at highest concentration were found in human liver microsomes. In vivo metabolites detected from rat urine included two poly-hydroxylated metabolites found only in this media. Mycelium matrix contained several dehydrogenated, N-oxygenated, and dibrominated metabolites.

Thiourea Derivative of 2-[(1R)-1-Aminoethyl]phenol: A Flexible Pocket-like Chiral Solvating Agent (CSA) for the Enantiodifferentiation of Amino Acid Derivatives by NMR Spectroscopy

Thiourea derivatives of 2-[(1R)-1-aminoethyl]phenol, (1S,2R)-1-amino-2,3-dihydro-1H-inden-2-ol, (1R,2R)-(1S,2R)-1-amino-2,3-dihydro-1H-inden-2-ol, and (R)-1-phenylethanamine have been compared as chiral solvating agents (CSAs) for the enantiodiscrimination of derivatized amino acids using nuclear magnetic resonance (NMR) spectroscopy. Thiourea derivative, prepared by reacting 2-[(1R)-1-aminoethyl]phenol with benzoyl isothiocyanate, constitutes an effective CSA for the enantiodiscrimination of N-3,5-dinitrobenzoyl (DNB) derivatives of amino acids with free or derivatized carboxyl functions. A base additive 1,4-diazabicyclo[2.2.2]octane(DABCO)/N,N-dimethylpyridin-4-amine (DMAP)/NBu4OH) is required both to solubilize amino acid derivatives with free carboxyl groups in CDCl3 and to mediate their interaction with the chiral auxiliary to attain efficient differentiation of the NMR signals of enantiomeric substrates. For ternary systems CSA/substrate/DABCO, the chiral discrimination mechanism has been ascertained through the NMR determination of complexation stoichiometry, association constants, and stereochemical features of the diastereomeric solvates.

Dibenzofuranylethylamines as 5-HT2A/2C Receptor Agonists

The human 5-HT₂ receptor subtypes have high sequence identity in their orthosteric ligand-binding domain, and many agonists are poorly selective between the 5-HT_2A and 5-HT_2C subtypes. Nevertheless, their activation is associated with different pharmacological outcomes. We synthesized five phenethylamine analogs in which the benzene ring is replaced by a bulky dibenzo[b,d]furan moiety and found a couple with >70-fold 5-HT_2C selectivity. Molecular docking studies of the most potent compound (5) at both receptor subtypes revealed the likely structural basis of its selectivity. Although in both cases, some crucial interactions are conserved, the change of the Ala222^5.46 residue in the 5-HT_2C receptor to the larger Ser242^5.46 in the 5-HT_2A subtype, which is the only structural difference between the orthosteric binding pockets of both receptors, weakens a π-π stacking interaction between the dibenzofuran moiety and the important Phe^6.52 residue and breaks a hydrogen bond between the dibenzofuran oxygen and Ser^5.43, explaining the selectivity of compound 5 for the 5-HT_2C receptor. We believe that this effect of the residue at position 5.46 merits further exploration in the search for selective 5-HT_2C receptor agonists that are of considerable interest in the treatment of schizophrenia and substance abuse.

Receptor Interaction Profiles of 4-Alkoxy-Substituted 2,5-Dimethoxyphenethylamines and Related Amphetamines

Background: 2,4,5-Trimethoxyamphetamine (TMA-2) is a potent psychedelic compound. Structurally related 4-alkyloxy-substituted 2,5-dimethoxyamphetamines and phenethylamine congeners (2C-O derivatives) have been described but their pharmacology is mostly undefined. Therefore, we examined receptor binding and activation profiles of these derivatives at monoamine receptors and transporters.

Methods: Receptor binding affinities were determined at the serotonergic 5-HT_1A, 5-HT_2A, and 5-HT_2C receptors, trace amine-associated receptor 1 (TAAR1), adrenergic α₁ and α₂ receptors, dopaminergic D₂ receptor, and at monoamine transporters, using target-transfected cells. Additionally, activation of 5-HT_2A and 5-HT_2B receptors and TAAR1 was determined. Furthermore, we assessed monoamine transporter inhibition.

Results: Both the phenethylamine and amphetamine derivatives (K_i = 8–1700 nM and 61–4400 nM, respectively) bound with moderate to high affinities to the 5-HT_2A receptor with preference over the 5-HT_1A and 5-HT_2C receptors (5-HT_2A/5-HT_1A = 1.4–333 and 5-HT_2A/5-HT_2C = 2.1–14, respectively). Extending the 4-alkoxy-group generally increased binding affinities at 5-HT_2A and 5-HT_2C receptors but showed mixed effects in terms of activation potency and efficacy at these receptors. Introduction of a terminal fluorine atom into the 4-ethoxy substituent by trend decreased, and with progressive fluorination increased affinities at the 5-HT_2A and 5-HT_2C receptors. Little or no effect was observed at the 5-HT_1A receptor for any of the substances tested (K_i ≥ 2700 nM). Phenethylamines bound more strongly to the TAAR1 (K_i = 21–3300 nM) compared with their amphetamine analogs (K_i = 630–3100 nM).

Conclusion: As seen with earlier series investigated, the 4-alkyloxy-substituted 2,5-dimethoxyamphetamines and phenethylamines share some trends with the many other phenethylamine pharmacophore containing compounds, such as when increasing the size of the 4-substituent and increasing the lipophilicity, the affinities at the 5-HT_2A/C subtype also increase, and only weak 5-HT_2A/C subtype selectivities were achieved. At least from the binding data available (i.e., high affinity binding at the 5-HT_2A receptor) one may predict mainly psychedelic-like effects in humans, at least for some of the compound investigated herein.

Synthesis and biological study of some new naphtho[2,1-b]furan and related heterocyclic systems

In the reaction of 1-cyano-2-naphthol (4) or its sodium salt with different alkylating agent, the O-alkylated derivatives (5a–d) were produced which underwent ring closure reactions using sodium ethoxide solution to give aminonaphtho [2,1- b]furan derivatives (6a–d). Ethyl 3-aminonaphtho[2,1- b]furan-2-carboxylate (8) was reacted with formamide to afford naphtho[1′,2′: 4,5]furo[3,2- d]pyrimidine (11) derivatives. The produced pyrimidino compound underwent various reactions to synthesise other heterocyclic compounds.

Comparison of the behavioral responses induced by phenylalkylamine hallucinogens and their tetrahydrobenzodifuran ("FLY") and benzodifuran ("DragonFLY") analogs

In recent years, rigid analogs of phenylalkylamine hallucinogens have appeared as recreational drugs. Examples include 2-(8-bromo-2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran-4-yl)ethan-1-amine (2C-B-FLY) and 1-(8-bromobenzo[1,2-b;4,5-b']difuran-4-yl)-2-aminopropane (Bromo-DragonFLY, DOB-DFLY). Although some rigid compounds such as DOB-DFLY reportedly have higher potency than their non-rigid counterparts, it is not clear whether the same is true for 2C-B-FLY and other tetrahydrobenzodifurans. In the present study, the head twitch response (HTR), a 5-HT2A receptor-mediated behavior induced by serotonergic hallucinogens, was used to assess the effects of 2,5-dimethoxy-4-bromoamphetamine (DOB) and its α-desmethyl homologue 2,5-dimethoxy-4-bromophenethylamine (2C-B), as well as their benzodifuranyl and tetrahydrobenzodifuranyl analogs, in C57BL/6J mice. DOB (ED50 = 0.75 μmol/kg) and 2C-B (ED50 = 2.43 μmol/kg) induced the HTR. The benzodifurans DOB-DFLY (ED50 = 0.20 μmol/kg) and 2C-B-DFLY (ED50 = 1.07 μmol/kg) had significantly higher potency than DOB and 2C-B, respectively. The tetrahydrobenzodifurans DOB-FLY (ED50 = 0.67 μmol/kg) and 2C-B-FLY (ED50 = 1.79 μmol/kg), by contrast, were approximately equipotent with their non-rigid counterparts. Three novel tetrahydrobenzodifurans (2C-I-FLY, 2C-E-FLY and 2C-EF-FLY) were also active in the HTR assay but had relatively low potency. In summary, the in vivo potency of 2,5-dimethoxyphenylalkylamines is enhanced when the 2- and 5-methoxy groups are incorporated into aromatic furan rings, whereas potency is not altered if the methoxy groups are incorporated into dihydrofuran rings. The potency relationships for these compounds in mice closely parallel the human hallucinogenic data. The high potency of DOB-DFLY is probably linked to the presence of two structural features (a benzodifuran nucleus and an α-methyl group) known to enhance the potency of phenylalkylamine hallucinogens.

Bromo-dragonfly, a psychoactive benzodifuran, is resistant to hepatic metabolism and potently inhibits monoamine oxidase A

Bromo-dragonfly is a benzodifuran derivative known as one of the most potent 5-HT_2A-receptor agonists within this chemical class, with long-lasting effects of up to 2-3 days. In addition to hallucinogenic effects, the drug is a potent vasoconstrictor, resulting in severe adverse effects, such as necrosis of the limbs. In some cases, intoxication has had fatal outcomes. Little is known about the metabolism of bromo-dragonfly. The aims of this study were to investigate the pharmacokinetics of bromo-dragonfly, determine the plasma protein binding, examine the human hepatic metabolism in vitro, and compare with those of its close analogue, 2C-B-fly. Additionally, we assayed the inhibition potency of both compounds on the monoamine oxidase (MAO) A- and B-mediated oxidative deamination of serotonin (5-HT) and dopamine, respectively. Liquid chromatography high-resolution mass spectrometry was used for metabolism studies in pooled human liver microsomes (HLM), pooled human liver cytosol (HLC) and recombinant enzymes. Inhibition studies of the deamination of 5-HT and dopamine were carried out using LC-MS/MS. Bromo-dragonfly was not metabolised in the tested in vitro systems. On the other hand, 2C-B-fly was metabolised in HLM by CYP2D6 and in HLC to some extent, with the main biotransformations being monohydroxylation and N-acetylation. Furthermore, MAO-A metabolised 2C-B-fly, producing the aldehyde metabolite, which was trapped in vitro with methoxyamine. Inhibition experiments revealed that bromo-dragonfly is a competitive inhibitor of MAO-A with a K_i of 0.352 μM. The IC₅₀ value for bromo-dragonfly indicated that the inhibition of MAO-A may be clinically relevant. However, more data are needed to estimate its impact on the increase of 5-HT in vivo.

6,7-Dimorpholinoalkoxy quinazoline derivatives as potent EGFR inhibitors with enhanced antiproliferative activities against tumor cells

A series of novel 6,7-dimorpholinoalkoxy quinazoline derivatives was designed, synthesized and evaluated as potent EGFR inhibitors. Most of synthesized derivatives exhibited moderate to excellent antiproliferative activities against five human tumor cell lines. Compound 8d displayed the most remarkable inhibitory activities against tumor cells expressing wild type (A431, A549 and SW480 cells) or mutant (HCC827 and NCI-H1975 cells) epidermal growth factor receptor (EGFR) (with IC₅₀ values in the range of 0.37-4.87 μM), as well as more potent inhibitory effects against recombinant EGFR tyrosine kinase (EGFR-TK, wt or T790M) (with the IC₅₀ values of 7.0 and 9.3 nM, respectively). Molecular docking showed that 8d can form four hydrogen bonds with EGFR, and two of them were located in the Asp855-Phe856-Gly857 (DFG) motif of EGFR. Meanwhile, 8d can significantly block EGF-induced EGFR activation and the phosphorylation of its downstream proteins such as Akt and Erk1/2 in human NSCLC cells. Also, 8d mediated cell apoptosis and the prolongation of cell cycle progression in G0/G1-phase in A549 cells. The work would have remarkable implications for further design and development of more potent EGFR tyrosine kinase inhibitors (TKIs).

Chemistry and Structure-Activity Relationships of Psychedelics

This chapter will summarize structure-activity relationships (SAR) that are known for the classic serotonergic hallucinogens (aka psychedelics), focusing on the three chemical types: tryptamines, ergolines, and phenethylamines. In the brain, the serotonin 5-HT_2A receptor plays a key role in regulation of cortical function and cognition, and also appears to be the principal target for hallucinogenic/psychedelic drugs such as LSD. It is one of the most extensively studied of the 14 known types of serotonin receptors. Important structural features will be identified for activity and, where possible, those that the psychedelics have in common will be discussed. Because activation of the 5-HT_2A receptor is the principal mechanism of action for psychedelics, compounds with 5-HT_2A agonist activity generally are quickly discarded by the pharmaceutical industry. Thus, most of the research on psychedelics can be related to activation of 5-HT_2A receptors. Therefore, much of the discussion will include not only clinical or anecdotal studies, but also will consider data from animal models as well as a certain amount of molecular pharmacology where it is known.

Experimental evaluation of the generalized vibrational theory of G protein-coupled receptor activation

Recently, an alternative theory concerning the method by which olfactory proteins are activated has garnered attention. This theory proposes that the activation of olfactory G protein-coupled receptors occurs by an inelastic electron tunneling mechanism that is mediated through the presence of an agonist with an appropriate vibrational state to accept the inelastic portion of the tunneling electron's energy. In a recent series of papers, some suggestive theoretical evidence has been offered that this theory may be applied to nonolfactory G protein-coupled receptors (GPCRs), including those associated with the central nervous system (CNS). [Chee HK, June OS (2013) Genomics Inform 11(4):282-288; Chee HK, et al. (2015) FEBS Lett 589(4):548-552; Oh SJ (2012) Genomics Inform 10(2):128-132]. Herein, we test the viability of this idea, both by receptor affinity and receptor activation measured by calcium flux. This test was performed using a pair of well-characterized agonists for members of the 5-HT₂ class of serotonin receptors, 2,5-dimethoxy-4-iodoamphetamine (DOI) and N,N-dimethyllysergamide (DAM-57), and their respective deuterated isotopologues. No evidence was found that selective deuteration affected either the binding affinity or the activation by the selected ligands for the examined members of the 5-HT₂ receptor class.

Neurotoxic Effects of 5-MeO-DIPT: A Psychoactive Tryptamine Derivative in Rats

5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT, 'foxy') is one of the most popular tryptamine hallucinogens in the illicit drug market. It produces serious adverse effects, but its pharmacological profile is not well recognized. In vitro data have shown that 5-MeO-DIPT acts as a potent serotonin transporter (SERT) inhibitor and displays high affinity at serotonin 5-HT1A, 5-HT2A, and 5-HT2C receptors. In this study, using microdialysis in freely moving rats, we examined the effect of 5-MeO-DIPT on dopamine (DA), serotonin (5-HT), and glutamate release in the rat striatum, nucleus accumbens, and frontal cortex. In search of a possible neurotoxic effect of 5-MeO-DIPT, we measured DA and 5-HT tissue content in the above rat brain regions and also determined the oxidative DNA damage with the comet assay. Moreover, we tested drug-elicited head-twitch response and a forepaw treading induced by 8-OH-DPAT. 5-MeO-DIPT at doses of 5, 10, and 20 mg/kg increased extracellular DA, 5-HT, and glutamate level but the differences in the potency were found between brain regions. 5-MeO-DIPT increased 5-HT and decreased 5-HIAA tissue content which seems to result from SERT inhibition. On the other hand, a decrease in DA, DOPAC, and HVA tissue contents suggests possible adaptive changes in DA turnover or damage of DA terminals by 5-MeO-DIPT. DNA single and double-strand breaks persisted up to 60 days after the treatment, indicating marked neurotoxicity of 5-MeO-DIPT. The induction of head-twitch response and potentiation of forepaw treading induced by 8-OH-DPAT indicate that hallucinogenic activity seems to be mediated through the stimulation of 5-HT2A and 5-HT1A receptors by 5-MeO-DIPT.

Synthesis, structural properties, electrophilic substitution reactions and DFT computational studies of calix[3]benzofurans

Synthesis of highly flexible calix[3]benzofurans; effects of substituent groups on calix[3]benzofuran conformations were studied by DFT computational methods.

Pharmacological profile of novel psychoactive benzofurans

BACKGROUND AND PURPOSE

Benzofurans are newly used psychoactive substances, but their pharmacology is unknown. The aim of the present study was to pharmacologically characterize benzofurans in vitro.

EXPERIMENTAL APPROACH

We assessed the effects of the benzofurans 5-APB, 5-APDB, 6-APB, 6-APDB, 4-APB, 7-APB, 5-EAPB and 5-MAPDB and benzodifuran 2C-B-FLY on the human noradrenaline (NA), dopamine and 5-HT uptake transporters using HEK 293 cells that express the respective transporters. We also investigated the release of NA, dopamine and 5-HT from monoamine-preloaded cells, monoamine receptor-binding affinity and 5-HT2A and 5-HT2B receptor activation.

KEY RESULTS

All of the benzofurans inhibited NA and 5-HT uptake more than dopamine uptake, similar to methylenedioxymethamphetamine (MDMA) and unlike methamphetamine. All of the benzofurans also released monoamines and interacted with trace amine-associated receptor 1 (TA1 receptor), similar to classic amphetamines. Most benzofurans were partial 5-HT2A receptor agonists similar to MDMA, but also 5-HT2B receptor agonists, unlike MDMA and methamphetamine. The benzodifuran 2C-B-FLY very potently interacted with 5-HT2 receptors and also bound to TA1 receptors.

CONCLUSIONS AND IMPLICATIONS

Despite very similar structures, differences were found in the pharmacological profiles of different benzofurans and compared with their amphetamine analogues. Benzofurans acted as indirect monoamine agonists that interact with transporters similarly to MDMA. The benzofurans also interacted with 5-HT receptors. This pharmacological profile probably results in MDMA-like entactogenic psychoactive properties. However, benzofurans induce 5-HT2B receptor activation associated with heart valve fibrosis. The pharmacology of 2C-B-FLY indicates predominant hallucinogenic properties and a risk for vasoconstriction.

Recreational drug discovery: natural products as lead structures for the synthesis of smart drugs

Covering: up to December 2013. Over the past decade, there has been a growing transition in recreational drugs from natural materials (marijuana, hashish, opium), natural products (morphine, cocaine), or their simple derivatives (heroin), to synthetic agents more potent than their natural prototypes, which are sometimes less harmful in the short term, or that combine properties from different classes of recreational prototypes. These agents have been named smart drugs, and have become popular both for personal consumption and for collective intoxication at rave parties. The reasons for this transition are varied, but are mainly regulatory and commercial. New analogues of known illegal intoxicants are invisible to most forensic detection techniques, while the alleged natural status and the lack of avert acute toxicity make them appealing to a wide range of users. On the other hand, the advent of the internet has made possible the quick dispersal of information among users and the on-line purchase of these agents and/or the precursors for their synthesis. Unlike their natural products chemotypes (ephedrine, mescaline, cathinone, psilocybin, THC), most new drugs of abuse are largely unfamiliar to the organic chemistry community as well as to health care providers. To raise awareness of the growing plague of smart drugs we have surveyed, in a medicinal chemistry fashion, their development from natural products leads, their current methods of production, and the role that clandestine home laboratories and underground chemists have played in the surge of popularity of these drugs.

Structure-activity relationships of constrained phenylethylamine ligands for the serotonin 5-HT2 receptors

Serotonergic ligands have proven effective drugs in the treatment of migraine, pain, obesity, and a wide range of psychiatric and neurological disorders. There is a clinical need for more highly 5-HT₂ receptor subtype-selective ligands and the most attention has been given to the phenethylamine class. Conformationally constrained phenethylamine analogs have demonstrated that for optimal activity the free lone pair electrons of the 2-oxygen must be oriented syn and the 5-oxygen lone pairs anti relative to the ethylamine moiety. Also the ethyl linker has been constrained providing information about the bioactive conformation of the amine functionality. However, combined 1,2-constriction by cyclization has only been tested with one compound. Here, we present three new 1,2-cyclized phenylethylamines, 9–11, and describe their synthetic routes. Ligand docking in the 5-HT_2B crystal structure showed that the 1,2-heterocyclized compounds can be accommodated in the binding site. Conformational analysis showed that 11 can only bind in a higher-energy conformation, which would explain its absent or low affinity. The amine and 2-oxygen interactions with D3.32 and S3.36, respectively, can form but shift the placement of the core scaffold. The constraints in 9–11 resulted in docking poses with the 4-bromine in closer vicinity to 5.46, which is polar only in the human 5-HT_2A subtype, for which 9–11 have the lowest affinity. The new ligands, conformational analysis and docking expand the structure-activity relationships of constrained phenethylamines and contributes towards the development of 5-HT₂ receptor subtype-selective ligands.

Synthesis of Chiral 1,2-Dihydronaphtho[2,1-b]furans by Organocatalytic Domino Reactions Catalyzed with Multiple Catalysis

A chiral multiple catalysis with two chiral units has been proved effective in the domino Friedel–Crafts alkylation of β-naphthols with α-bromonitroalkenes. This novel and efficient domino reaction affords chiral 1,2-dihydronaphtho[2,1-b]furans in good to high yields and enantioselectivities (up to 93 % yield, 91 % enantiomeric excess).

Carbazolyl benzo[1,2-b:4,5-b']difuran: an ambipolar host material for full-color organic light-emitting diodes

We have designed an ambipolar material, 3,7-bis[4-(N-carbazolyl)-phenyl]-2,6-diphenylbenzo[1,2-b:4,5-b']difuran (CZBDF), and synthesized it by zinc-mediated double cyclization. Its physical properties clarified that CZBDF possesses a wide-gap character, well-balanced and high hole and electron mobilities of larger than 10(-3) cm(2) V(-1) s(-1), and a high thermal stability. Using CZBDF as a host material for heterojunction OLED devices, a full range of visible emission was obtained. Notably, CZBDF also enabled us to fabricate RGB-emitting homojunction OLEDs, with performances comparable or superior to the heterojunction devices composed of several materials.

A reported "new synthesis of lysergic acid" yields only the derailment product: methyl 5-methoxy-4,5-dihydroindolo[4,3-f,g]quinoline-9-carboxylate

The treatment of ethyl 6-formyl-5-(1H-indol-4-yl)pyridine-3-carboxylate (2) with NaOMe or NaOH in methanol solution at room temperature under the reported reaction conditions afforded solely product 4 in 80% yield, rather than anticipated product 3.

Prenatal Cocaine Disrupts Serotonin Signaling-Dependent Behaviors: Implications for Sex Differences, Early Stress and Prenatal SSRI Exposure

Prenatal cocaine (PC) exposure negatively impacts the developing nervous system, including numerous changes in serotonergic signaling. Cocaine, a competitive antagonist of the serotonin transporter, similar to selective serotonin reuptake inhibitors (SSRIs), also blocks dopamine and norepinephrine transporters, leaving the direct mechanism through which cocaine disrupts the developing serotonin system unclear. In order to understand the role of the serotonin transporter in cocaine's effect on the serotonergic system, we compare reports concerning PC and prenatal antidepressant exposure and conclude that PC exposure affects many facets of serotonergic signaling (serotonin levels, receptors, transporters) and that these effects differ significantly from what is observed following prenatal SSRI exposure. Alterations in serotonergic signaling are dependent on timing of exposure, test regimens, and sex. Following PC exposure, behavioral disturbances are observed in attention, emotional behavior and stress response, aggression, social behavior, communication, and like changes in serotonergic signaling, these effects depend on sex, age and developmental exposure. Vulnerability to the effects of PC exposure can be mediated by several factors, including allelic variance in serotonergic signaling genes, being male (although fewer studies have investigated female offspring), and experiencing the adverse early environments that are commonly coincident with maternal drug use. Early environmental stress results in disruptions in serotonergic signaling analogous to those observed with PC exposure and these may interact to produce greater behavioral effects observed in children of drug-abusing mothers. We conclude that based on past evidence, future studies should put a greater emphasis on including females and monitoring environmental factors when studying the impact of PC exposure.

Some new psychoactive substances: precursor chemicals and synthesis-driven end-products

This paper describes some of the new classes of 'designer drugs' being encountered today by forensic scientists and law enforcement agencies in Europe, the United States, and Australia. In particular, it concentrates on new cathinone derivatives, the tryptamines, new-generation phenethylamines, and some of the synthetic cannabinoids. The synthetic approaches towards many of these designer drugs including a discussion of the chemical precursors used in the syntheses are presented. Many of today's so-called designer drugs exist as a result of legitimate research into medical conditions and the natural product chemistry. A link between synthetic approaches published in the open scientific and medical literature and the exploitation of this research by clandestine manufacture of drugs for illicit purposes is drawn.

Versatile strategy to access fully functionalized benzodifurans: redox-active chromophores for the construction of extended pi-conjugated materials

An efficient synthetic approach to construct a fully substituted benzo[1,2-b:4,5-b']difuran (BDF) 2a via base-catalyzed double annulations is presented. Compound 2a can readily undergo Suzuki, Heck, and Sonogashira coupling reactions to afford in good yields a manifold of extended pi-conjugated BDF derivatives, e.g., with pyridine termini (4-6) and with different spacers. These are highly luminescent materials that undergo two reversible one-electron oxidations. Remarkably, their photophysical and electrochemical properties can be largely tuned by methylation or protonation. Consequently, they can function as pH-dependent fluorescence switches. Finally, the observed electronic properties are explained on the basis of density functional theory.

Delayed onset of seizures and toxicity associated with recreational use of Bromo-dragonFLY

INTRODUCTION

Many countries have specific legislation, such as the Controlled Substances Act (1970) in the United States and the Misuse of Drugs Act (1971) in the United Kingdom to control recreational drugs. There is a growing market and supply of "novel" recreational drugs, which include the misuse of pharmaceutical compounds and research chemicals. These are often not covered under current legislation, despite the fact that they often have both similar chemical structures and/or clinical effects to controlled recreational drugs.

CASE REPORT

A male patient presented to an emergency department with delayed onset of severe agitation, hallucinations, and tonic-clonic seizures following the use of Bromo-dragonFLY and an unknown white powder. He settled following IV benzodiazepines and supportive care, and was discharged with no evidence of long-term sequelae. Analysis of the white powder by gas chromatography/mass spectrometry (GC/MS), ultraviolet/visible spectrophotometry (UV/VIS) and thin layer chromatography (TLC) showed the presence of Bromo-dragonFLY (1-(8-bromobenzo[1,2-b;4,5-b']difuran-4-yl)-2-aminopropane); serum analysis by GC/MS and liquid chromatography with tandem mass spectrometry (LC/MS/MS) confirmed that a combination of Bromo-dragonFLY (0.95 ng/mL), ketamine (20 ng/mL) and cannabis had been used by the patient. No other recreational drugs were detected in an extensive toxicological screen of serum and urine samples.

DISCUSSION

This is the first confirmed case to be reported of toxicity with delayed onset of severe agitation, hallucinations and tonic-clonic seizures associated with recreational use of Bromo-dragonFLY (1-(8-bromobenzo[1,2-b;4,5-b']difuran-4-yl)-2-aminopropane) in combination with ketamine and cannabis. In our view, this case provides further support for the need for a systematic approach to toxicological screening of patients with recreational drug toxicity, to identify emerging drugs and provide evidence for legislative authorities to assist in revising the legal status of emerging recreational drugs.