A novel fluorinated tryptamine with highly potent serotonin 5-HT1A receptor agonist properties

Structural pharmacology and therapeutic potential of 5-methoxytryptamines

Psychedelic substances such as lysergic acid diethylamide (LSD) and psilocybin show potential for the treatment of various neuropsychiatric disorders1-3. These compounds are thought to mediate their hallucinogenic and therapeutic effects through the serotonin (5-hydroxytryptamine (5-HT)) receptor 5-HT2A (ref. 4). However, 5-HT1A also plays a part in the behavioural effects of tryptamine hallucinogens5, particularly 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), a psychedelic found in the toxin of Colorado River toads6. Although 5-HT1A is a validated therapeutic target7,8, little is known about how psychedelics engage 5-HT1A and which effects are mediated by this receptor. Here we map the molecular underpinnings of 5-MeO-DMT pharmacology through five cryogenic electron microscopy (cryo-EM) structures of 5-HT1A, systematic medicinal chemistry, receptor mutagenesis and mouse behaviour. Structure-activity relationship analyses of 5-methoxytryptamines at both 5-HT1A and 5-HT2A enable the characterization of molecular determinants of 5-HT1A signalling potency, efficacy and selectivity. Moreover, we contrast the structural interactions and in vitro pharmacology of 5-MeO-DMT and analogues to the pan-serotonergic agonist LSD and clinically used 5-HT1A agonists. We show that a 5-HT1A-selective 5-MeO-DMT analogue is devoid of hallucinogenic-like effects while retaining anxiolytic-like and antidepressant-like activity in socially defeated animals. Our studies uncover molecular aspects of 5-HT1A-targeted psychedelics and therapeutics, which may facilitate the future development of new medications for neuropsychiatric disorders.

Fluorinated indole-imidazole conjugates: Selective orally bioavailable 5-HT7 receptor low-basicity agonists, potential neuropathic painkillers

The 5-HT₇ receptor has recently gained much attention due to its involvement in multiple physiological functions and diseases. The insufficient quality of the available molecular probes prompted design of fluorinated 3-(1-alkyl-1H-imidazol-5-yl)-1H-indoles as a new generation of selective 5-HT₇ receptor agonists. A potent and drug-like agonist, 3-(1-ethyl-1H-imidazol-5-yl)-5-iodo-4-fluoro-1H-indole (AGH-192, 35, K_{i 5-HT7R} = 4 nM), was identified by optimizing the halogen bond formation with Ser5.42 as the supposed partner. The compound was characterized by excellent water solubility, high selectivity over related CNS targets, high metabolic stability, oral bioavailability and low cytotoxicity. Rapid absorption into the blood, medium half-life and a high peak concentration in the brain C_max = 1069 ng/g were found after i.p. (2.5 mg/kg) administration in mice. AGH-192 may thus serve as the long-sought tool compound in the study of 5-HT₇ receptor function, as well as a potential analgesic, indicated by the antinociceptive effect observed in a mouse model of neuropathic pain.

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.

Ruthenium-Catalyzed C-H Arylation of Benzoic Acids and Indole Carboxylic Acids with Aryl Halides

Herein we report the first Ru-catalyzed C-H arylation of benzoic acids with readily available aryl (pseudo)halides. The reaction, which does not require the use of silver salt additives, allows the arylation of previously challenging hindered benzoic acids and the use of generally unreactive ortho-substituted halorarenes. Furthermore, our new protocol can efficiently be applied to indole carboxylic acids, thus allowing access to C7-, C6-, C5- and C4-arylated indole compounds, a departure from the classical enhanced reactivity of the C2 and C3 positions of indole.

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.

Non-peptidic αvβ3 antagonists containing indol-1-yl propionic acids

We describe the synthesis and structure/activity relationship of RGD mimetics that are potent inhibitors of the integrin alpha(v)beta3. Indol-1-yl propionic acids containing a variety of basic moieties at the 5-position, as well as substitutions alpha and beta to the carboxy terminus were synthesized and evaluated. Novel compounds with improved potency have been identified.

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.

Preparation of 8-Amido-2-dimethylamino-1,2,3,4-tetrahydro-2-dibenzofurans and several fluorinated derivatives via [3,3]-sigmatropic rearrangement of O-aryloximes

Methodology to prepare 8-amido-2-amino-1,2,3,4-tetrahydro-2-dibenzofurans, analogues with a fluorine substituent incorporated in the 6-, 7-, and 9-positions, and a difluorinated analogue with fluorines in the 6- and 9-positions is described. The tetrahydrodibenzofuran ring systems are prepared by acid-catalyzed [3,3]-sigmatropic rearrangement of O-aryloximes. Regioselective reactions to prepare the requisite O-aryloxime intermediates from commercially available fluorobenzene derivatives are discussed.