An Electrosynthesis of 1,3,4-Oxadiazoles from N-Acyl Hydrazones.

The 1,3,4-oxadiazole is a widely encountered motif in the areas of pharmaceuticals, materials, and agrochemicals. This work has established a mild, mediated electrochemical synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from N-acyl hydrazones. Using DABCO as the optimal redox mediator has enabled a mild oxidative cyclisation, without recourse to stoichiometric oxidants. In contrast to previous methods, this indirect electrochemical oxidation has enabled a broad range of substrates to be accessed, with yields of up to 83%, and on gram scale. The simplicity of the method has been further demonstrated by the development of a one-pot procedure, directly transforming readily available aldehydes and hydrazides into valuable heterocycles.

Investigation on the Influence of Solvents Environment on the Optoelectronic Properties of the Fluorescent Probe 1,3,4-Oxadiazole Analogues: A Combined Theoretical and Experimental Study.

This study investigates the photophysical properties of a nitrobenzene-substituted 1,3,4-oxadiazole derivative (OX-NO) using both theoretical and experimental methods. The impact of the solvent on OX-NO absorption and fluorescence spectra, as well as its fluorescence quantum yield, was initially studied. A noticeable bathochromic shift in the Stokes shift indicated a π→ π* transition within the molecules. Solute-solvent interactions were analysed using Catalan parameters, distinguishing between specific and nonspecific interactions. Excited state dipole moments were derived from Lippert's, Bakshiev's, and Chamma Viallet's equations, showing increased polarity in the excited state compared to the ground state. Ground state dipole moments were determined via solvatochromic shift methods and ab initio techniques. Additionally, detailed analyses of bond length, angles, dihedral angles, Mulliken charge distribution, and HOMO-LUMO energy gap were conducted using the DFT-B3LYP-6-311G basis set in Gaussian-09 W. The energy band gap values obtained from theoretical calculations and experimental methods (cyclic voltammetry and UV-Visible spectroscopy) exhibited excellent agreement. Reactive sites such as electrophilic and nucleophilic regions were identified through total electron density, electrostatic maps, molecular electrostatic potential, and 3D plots using DFT computational analysis. Global descriptors were employed to characterize the compounds' chemical reactivity comprehensively. The observed photophysical attributes underscore the potential of these fluorophores in various applications like organic light-emitting diodes, solar cells, and chemosensors. This study contributes crucial insights into the optoelectronic properties of nitrobenzene-substituted 1,3,4-oxadiazole derivatives, paving the way for their future integration in advanced technological domains.

Design, synthesis, anti-mycobacterial activity, molecular docking and ADME analysis of spiroquinoxaline-1,2,4-oxadiazoles via [3 + 2] cycloaddition reaction under ultrasound irradiation.

The development of anti-tuberculosis (anti-TB) drugs has become a challenging task in medicinal chemistry. This is because Mycobacterium tuberculosis (TB), the pathogen that causes tuberculosis, has an increasing number of drug-resistant strains, and existing medication therapies are not very effective. This resistance significantly demands new anti-TB drug profiles. Here, we present the design and synthesis of a number of hybrid compounds with previously known anti-mycobacterial moieties attached to quinoxaline, quinoline, tetrazole, and 1,2,4-oxadiazole scaffolds. A convenient ultrasound methodology was employed to attain spiroquinoxaline-1,2,4-oxadiazoles via [3 + 2] cycloaddition of quinoxaline Schiff bases and aryl nitrile oxides at room temperature. This approach avoids standard heating and column chromatography while producing high yields and shorter reaction times. The target compounds 3a-p were well-characterized, and their in vitro anti-mycobacterial activity (anti-TB) was evaluated. Among the screened compounds, 3i displayed promising activity against the Mycobacterium tuberculosis cell line H37Rv, with an MIC99 value of 0.78 µg/mL. However, three compounds (3f, 3h, and 3o) exhibited potent activity with MIC99 values of 6.25 µg/mL. To further understand the binding interactions, the synthesized compounds were docked against the tuberculosis protein 5OEQ using in silico molecular docking. Moreover, the most active compounds were additionally tested for their cytotoxicity against the RAW 264.7 cell line, and the cytotoxicity of compounds 3f, 3h, 3i, and 3o was 27.3, 28.9, 26.4, and 30.2 µg/mL, respectively. These results revealed that the compounds 3f, 3h, 3i, and 3o were less harmful to humans. Furthermore, the synthesized compounds were tested for ADME qualities, and the results suggest that this series is useful for producing innovative and potent anti-tubercular medicines in the future.

iNOS/PGE2 inhibitors as a novel template for analgesic/anti-inflammatory activity: Design, synthesis, in vitro biological activity and docking studies.

Due to the serious gastrointestinal side effects associated with prolonged use of current anti-inflammatory therapies, various strategies such as the regulation of nitric oxide (NO) and prostaglandin E2 (PGE2) production have been explored in the field of anti-inflammatory drug development. In this study, a series of disubstituted 1,3,4-oxadiazoles (3a-f and 4a-f) and their cyclized 1,2,4-triazole derivatives (5a-e and 6a-e) were synthesized and tested for their NO, PGE2, and interleukin-6 (IL-6) releasing inhibition ability. All of the compounds were observed to reduce lipopolysaccharide (LPS)-induced nitrite production in a concentration-dependent manner. Moreover, compounds 3b (50 µM) and 6d (1 µM) exhibited 63% and 49% inhibition, respectively, while indomethacin showed 52% at 100 µM. Based on a preliminary NO inhibition assay, 10 of the compounds (3a, 3b, 3e, 4b, 4d, 6a-e) were selected to be evaluated for in vitro PGE2, IL-6, and inducible nitric oxide synthase (iNOS) inhibition. Notably, compound 6d proved to be the most active of the series with the lowest dose (1 µM), in comparison to the other further tested compounds (5-100 µM) and the reference drug indomethacin (100 µM). The inhibitory activity of the compounds was supported by docking simulations into the binding site of the iNOS protein receptor (Protein Data Bank [PDB]ID: 3E7G). The data showing that 4d reduced iNOS levels the most can be explained by the H-bond with Tyr347 through oxadiazole and π-halogen interactions through the p-bromo, in addition to aromatic interactions with protoporphyrin IX.

Hybrid 2D Supramolecular Organic Frameworks (SOFs) Assembled by the Cooperative Action of Hydrogen and Halogen Bonding and π⋯π Stacking Interactions.

The cis- and trans-isomers of 6-(3-(3,4-dichlorophenyl)-1,2,4-oxadiazol-5-yl)cyclohex-3-ene-1-carboxylic acid (cis-A and trans-A) were obtained by the reaction of 3,4-dichloro-N'-hydroxybenzimidamide and cis-1,2,3,6-tetrahydrophthalic anhydride. Cocrystals of cis-A with appropriate solvents (cis-A‧½(1,2-DCE), cis-A‧½(1,2-DBE), and cis-A‧½C6H14) were grown from 1,2-dichloroethane (1,2-DCE), 1,2-dibromoethane (1,2-DBE), and a n-hexane/CHCl3 mixture and then characterized by X-ray crystallography. In their structures, cis-A is self-assembled to give a hybrid 2D supramolecular organic framework (SOF) formed by the cooperative action of O-H⋯O hydrogen bonding, Cl⋯O halogen bonding, and π⋯π stacking. The self-assembled cis-A divides the space between the 2D SOF layers into infinite hollow tunnels incorporating solvent molecules. The energy contribution of each noncovalent interaction to the occurrence of the 2D SOF was verified by several theoretical approaches, including MEP and combined QTAIM and NCIplot analyses. The consideration of the theoretical data proved that hydrogen bonding (approx. -15.2 kcal/mol) is the most important interaction, followed by π⋯π stacking (approx. -11.1 kcal/mol); meanwhile, the contribution of halogen bonding (approx. -3.6 kcal/mol) is the smallest among these interactions. The structure of the isomeric compound trans-A does not exhibit a 2D SOF architecture. It is assembled by the combined action of hydrogen bonding and π⋯π stacking, without the involvement of halogen bonds. A comparison of the cis-A structures with that of trans-A indicated that halogen bonding, although it has the lowest energy in cis-A-based cocrystals, plays a significant role in the crystal design of the hybrid 2D SOF. The majority of the reported porous halogen-bonded organic frameworks were assembled via iodine and bromine-based contacts, while chlorine-based systems-which, in our case, are structure-directing-were unknown before this study.

Synthesis of 1,3,5-Triazepines and Benzo[f][1,3,5]triazepines and Their Biological Activity: Recent Advances and New Approaches.

This review article discusses the recent progress in synthesizing seven-membered ring 1,3,5-triazepine and benzo[f][1,3,5]triazepine derivatives. These derivatives can be either unsaturated, saturated, fused, or separated. This review covers strategies and procedures developed over the past two decades, including cyclo-condensation, cyclization, methylation, chlorination, alkylation, addition, cross-coupling, ring expansions, and ring-closing metathesis. This review discusses the synthesis of 1,3,5-triazepine derivatives using nucleophilic or electrophilic substitution reactions with various reagents such as o-phenylenediamine, 2-aminobenzamide, isothiocyanates, pyrazoles, thiazoles, oxadiazoles, oxadiazepines, and hydrazonoyl chloride. This article systematically presents new approaches and techniques for preparing these compounds. It also highlights the biological importance of benzo[f][1,3,5]triazepine derivatives, which have been used as drugs for treating nervous system diseases. This review aims to provide researchers with the necessary information to create and develop new derivatives of these compounds as quickly as possible.

N-Halogenation by Vanadium-Dependent Haloperoxidases Enables 1,2,4-Oxadiazole Synthesis.

Nitrogen-containing compounds are valuable synthetic intermediates and targets in nearly every chemical industry. While methods for nitrogen-carbon and nitrogen-heteroatom bond formation have primarily relied on nucleophilic nitrogen atom reactivity, molecules containing nitrogen-halogen bonds allow for electrophilic or radical reactivity modes at the nitrogen center. Despite the growing synthetic utility of nitrogen-halogen bond-containing compounds, selective catalytic strategies for their synthesis are largely underexplored. We recently discovered that the vanadium-dependent haloperoxidase (VHPO) class of enzymes are a suitable biocatalyst platform for nitrogen-halogen bond formation. Herein, we show that VHPOs perform selective halogenation of a range of substituted benzamidine hydrochlorides to produce the corresponding N'-halobenzimidamides. This biocatalytic platform is applied to the synthesis of 1,2,4-oxadiazoles from the corresponding N-acylbenzamidines in high yield and with excellent chemoselectivity. Finally, the synthetic applicability of this biotechnology is demonstrated in an extension to nitrogen-nitrogen bond formation and the chemoenzymatic synthesis of the Duchenne muscular dystrophy drug, ataluren.

Tandem diazotization/cyclization approach for the synthesis of a fused 1,2,3-triazinone-furazan/furoxan heterocyclic system.

A straightforward protocol for the synthesis of a previously unknown [1,2,5]oxadiazolo[3,4-d][1,2,3]triazin-7(6H)-one heterocyclic system was developed. The described approach is based on tandem diazotization/azo coupling reactions of (1,2,5-oxadiazolyl)carboxamide derivatives bearing both aromatic and aliphatic substituents. The NO-donor ability of the synthesized furoxano[3,4-d][1,2,3]triazin-7(6H)-ones was additionally evaluated. The elaborated method provides access to novel nitrogen heterocyclic compounds with potential applications as drug candidates or thermostable components of functional organic materials.

Identification of new hit to lead magmas inhibitors as potential therapeutics for glioblastoma.

In continuation of our previous efforts for the development of potent small molecules against brain cancer, herein we synthesized seventeen new compounds and tested their anti-gliomapotential against established glioblastoma cell lines, namely, D54MG, U251, and LN-229 as well as patient derived cell lines (DB70 and DB93). Among them, the carboxamide derivatives, BT-851 and BT-892 were found to be the most active leads in comparison to our established hit compound BT#9.The SAR studies of our hit BT#9 compound resulted in the development of two new lead compounds by hit to lead strategy. The detailed biological studies are currently underway. The active compounds could possibly act as template for the future development of newer anti-glioma agents.

Design, synthesis, and biological evaluation of a novel series of 1,2,4-oxadiazole inhibitors of SLACK potassium channels: Identification of in vitro tool VU0935685.

Malignant migrating partial seizure of infancy (MMPSI) is a devastating and pharmacoresistant form of infantile epilepsy. MMPSI has been linked to multiple gain-of-function (GOF) mutations in the KCNT1 gene, which encodes for a potassium channel often referred to as SLACK. SLACK channels are sodium-activated potassium channels distributed throughout the central nervous system (CNS) and the periphery. The investigation described here aims to discover SLACK channel inhibitor tool compounds and profile their pharmacokinetic and pharmacodynamic properties. A SLACK channel inhibitor VU0531245 (VU245) was identified via a high-throughput screen (HTS) campaign. Structure-activity relationship (SAR) studies were conducted in five distinct regions of the hit VU245. VU245 analogs were evaluated for their ability to affect SLACK channel activity using a thallium flux assay in HEK-293 cells stably expressing wild-type (WT) human SLACK. Selected analogs were tested for metabolic stability in mouse liver microsomes and plasma-protein binding in mouse plasma. The same set of analogs was tested via thallium flux for activity versus human A934T SLACK and other structurally related potassium channels, including SLICK and Maxi-K. In addition, potencies for selected VU245 analogs were obtained using whole-cell electrophysiology (EP) assays in CHO cells stably expressing WT human SLACK through an automated patch clamp system. Results revealed that this scaffold tolerates structural changes in some regions, with some analogs demonstrating improved SLACK inhibitory activity, good selectivity against the other channels tested, and modest improvements in metabolic clearance. Analog VU0935685 represents a new, structurally distinct small-molecule inhibitor of SLACK channels that can serve as an in vitro tool for studying this target.

Synthesis of 1,2,4-triazole and 1,3,4-oxadiazole derivatives as inhibitors for STAT3 enzymes of breast cancer.

Disubstituted five-membered heterocycles (1,2,4-triazole and 1,3,4 oxadiazole) were synthesized and investigated as inhibitors for signal transducer and activator of transcription 3 (STAT3) enzyme of breast cancer. 3-(Benzylthio)-5-(4-chlorobenzyl)-4H-1,2,4-triazol-4-amine (12d) was found to be the most active among the synthesized compounds with a half-maximal inhibitory concentration (IC50 ) value of 1.5 µM on MCF7 cells and was found to show a great inhibitory effect on the STAT3 enzyme. Compounds 9a,b,d,e,f, 11, and 12a,b,f,e show IC50 values in the range of 3-12 µM for the MCF7 cell line. Molecular modeling was used to investigate the biological results of the synthesized compounds.

Novel Hydroxamic Acids Containing Aryl-Substituted 1,2,4- or 1,3,4-Oxadiazole Backbones and an Investigation of Their Antibiotic Potentiation Activity.

UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC) is a zinc amidase that catalyzes the second step of the biosynthesis of lipid A, which is an outer membrane essential structural component of Gram-negative bacteria. Inhibitors of this enzyme can be attributed to two main categories, non-hydroxamate and hydroxamate inhibitors, with the latter being the most effective given the chelation of Zn2+ in the active site. Compounds containing diacetylene or acetylene tails and the sulfonic head, as well as oxazoline derivatives of hydroxamic acids, are among the LpxC inhibitors with the most profound antibacterial activity. The present article describes the synthesis of novel functional derivatives of hydroxamic acids-bioisosteric to oxazoline inhibitors-containing 1,2,4- and 1,3,4-oxadiazole cores and studies of their cytotoxicity, antibacterial activity, and antibiotic potentiation. Some of the hydroxamic acids we obtained (9c, 9d, 23a, 23c, 30b, 36) showed significant potentiation in nalidixic acid, rifampicin, and kanamycin against the growth of laboratory-strain Escherichia coli MG1655. Two lead compounds (9c, 9d) significantly reduced Pseudomonas aeruginosa ATCC 27853 growth in the presence of nalidixic acid and rifampicin.

Structure-Activity Relationships and Antiplasmodial Potencies of Novel 3,4-Disubstituted 1,2,5-Oxadiazoles.

The 4-substituted 3-amino-1,2,5-oxadiazole 1 from the Malaria Box Project of the Medicines for Malaria Venture foundation shows very promising selectivity and in vitro activity against Plasmodium falciparum. Within the first series of new compounds, various 3-acylamino analogs were prepared. This paper now focuses on the investigation of the importance of the aromatic substituent in ring position 4. A number of new structure-activity relationships were elaborated, showing that antiplasmodial activity and selectivity strongly depend on the substitution pattern of the 4-phenyl moiety. In addition, physicochemical parameters relevant for drug development were calculated (logP and ligand efficiency) or determined experimentally (CYP3A4-inhibition and aqueous solubility). N-[4-(3-ethoxy-4-methoxyphenyl)-1,2,5-oxadiazol-3-yl]-3-methylbenzamide 51 showed high in vitro activity against the chloroquine-sensitive strain NF54 of P. falciparum (PfNF54 IC50 = 0.034 µM), resulting in a very promising selectivity index of 1526.

DFT Study of Regio- and Stereoselective 13DC Reaction between Diazopropane and Substituted Chalcone Derivatives: Molecular Docking of Novel Pyrazole Derivatives as Anti-Alzheimer's Agents.

In the present work, a combination of experimental and density functional theory (DFT) investigation of the (3+2) cycloaddition reactions of diazopropane with chalcone derivatives was reported. All calculations were performed using several DFT approaches (B3LYP, M06, M06-2X) and 6-311+G(d, p) basis set. Based on the NMR, MS analyses and IRC calculations, the pyrazole derivatives are the kinetic adducts over the oxadiazoles. The use of two equivalents of diazopropane leads to thermodynamical products. A molecular docking analysis was performed to investigate the efficiency of the obtained products against selected drug targets in anti-Alzheimer ligand-receptor interactions. We revealed that the ligands selected were bound mainly to the catalytic (CAS) and peripheral (PAS) anionic sites of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors, respectively. The selected ligands 1, 3, 4 and P14 may act as the best inhibitors against Alzheimer's disease (AD).

Neuroprotective evaluation of novel substituted 1,3,4-oxadiazole and aroylhydrazone derivatives.

The paper reports on the facile and convenient synthesis of a series of novel 2,5-substituted 1,3,4-oxadiazoles 3a-f and that of aroylhydrazone-based molecular hybrids 5a-g from readily available starting materials. The structure of the compounds was confirmed by IR, 1H NMR, 13C NMR and HRESI-MS spectral data. The toxicological potential of the compounds was evaluated by monitoring the synaptosomal viability and the levels of reduced glutathione in rat brain synaptosomes, isolated by Percoll gradient. The neuroprotective effects were assessed in vitro in a model of 6-hydroxydopamine-induced neurotoxicity. Administered alone, at a concentration of 40 µM, most of the 1,3,4-oxadiazole derivatives and all of the hydrazone derivatives exhibited weak statistically significant neurotoxic effects, compared to the control. Two of the compounds from the novel oxadiazoles 3a and 3d did not have any toxicity. In a model of 6-OHDA-induced oxidative stress, again 3a and 3d and all aroylhydrazone derivatives 5a-g revealed statistically significant neuroprotective effect by preserving the synaptosomal viability and the level of reduced glutathione, against the toxic agent. Some of the compounds may have neuroprotective effects due to possible stabilization of the synaptosomal membrane and/or because of the preserved reduced glutathione. Additionally, all the compounds display a good predicted ADME profile.

Novel O-acylated amidoximes and substituted 1,2,4-oxadiazoles synthesised from (+)-ketopinic acid possessing potent virus-inhibiting activity against phylogenetically distinct influenza A viruses.

This article describes the synthesis and antiviral activity evaluation of new substituted 1,2,4-oxadiazoles containing a bicyclic substituent at position 5 of the heterocycle and O-acylated amidoximes as precursors for their synthesis. New compounds were obtained from the (+)-camphor derivative (+)-ketopinic acid. The chemical library was tested in vitro for cytotoxicity against the MDCK cell line and for antiviral activity against influenza viruses of H1N1 and H7N9 subtypes. The synthesised compounds exhibited high virus-inhibiting activity against the H1N1 influenza virus. Some synthesised compounds were also active against the influenza virus of a different antigenic subtype: H7N9. The mechanism of the virus-inhibiting activity of these compounds is based on their interference with the fusion activity of viral hemagglutinin (HA). No interference with the receptor-binding activity of HA has been demonstrated. According to molecular docking results, the selective antiviral activity of O-acylated amidoximes and 1,2,4-oxadiazoles is associated with their structural features. O-Acylated amidoximes are likely more complementary to the binding site located at the site of the fusion peptide, and 1,2,4-oxadiazoles are more complimentary to the site located at the site of proteolysis. Significant differences in the amino acid residues of the binding sites of HA's of different types allow us to explain the selective antiviral activity of the compounds under study.

Synthesis and anti-HIV activity of a new isoxazole containing disubstituted 1,2,4-oxadiazoles analogs.

Continuing on our antiviral drug discovery research, we intended to diversify our lead anti-HIV-1 inhibitor by non-classical isosteric replacement of amide to 1,2,4-oxadiazoles. The resulting molecules isoxazole-1,2,4-oxadiazole analogs were synthesized using mild bases in ethanol under microwave irradiation. The anti-HIV potential was checked in human CD4+ reporter cell lines, TZM-bl and CEM-GFP, at the highest non-cytotoxic concentration (HNC), demonstrating that 3-((3-(p-tolyl)isoxazol-5-yl)methyl)-1,2,4-oxadiazole and 3-((3-(4-chlorophenyl)isoxazol-5-yl)methyl)-1,2,4-oxadiazole inhibit HIV-1 replication significantly and could be considered as a new lead candidate against HIV-1.

A review on synthetic account of 1,2,4-oxadiazoles as anti-infective agents.

Most of the currently marketed drugs consist of heterocyclic scaffolds containing nitrogen and or oxygen as heteroatoms in their structures. Several research groups have synthesized diversely substituted 1,2,4-oxadiazoles as anti-infective agents having anti-bacterial, anti-viral, anti-leishmanial, etc. activities. For the first time, the present review article will provide the coverage of synthetic account of 1,2,4-oxadiazoles as anti-infective agents along with their potential for SAR, activity potential, promising target for mode of action. The efforts have been made to provide the chemical intuitions to the reader to design new chemical entity with potential of anti-infective activity. This review will mark the impact as the valuable, comprehensive and pioneered work along with the library of synthetic strategies for the organic and medicinal chemists for further refinement of 1,2,4-oxadiazole as anti-infective agents.

Synthesis of a boron-containing amidoxime reagent and its application to synthesize functionalized oxadiazole and quinazolinone derivatives.

Herein, we report the design, synthesis and application of a borylated amidoxime reagent for the direct synthesis of functionalized oxadiazole and quinazolinone derivatives. This reagent exhibits broad synthetic utility to obtain a variety of biologically relevant drug-like molecules. It can be easily prepared at large scale from relatively inexpensive reagents, and can undergo facile transformations to obtain target compounds. The developed amidoxime reagent was synthesized from 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile and hydroxyl amine hydrochloride using N,N-diisopropylethylamine as a base in ethanol under reflux conditions. Overall advantages include a metal-free route to boronated oxadiazoles, quinazolinone derivatives, and restriction of the multistep sequences. Importantly, the boron-rich pharmacophore derived compounds were obtained through an efficient and inexpensive strategy.

New 1,2,4-oxadiazole derivatives with positive mGlu4 receptor modulation activity and antipsychotic-like properties.

Considering the allosteric regulation of mGlu receptors for potential therapeutic applications, we developed a group of 1,2,4-oxadiazole derivatives that displayed mGlu4 receptor positive allosteric modulatory activity (EC50 = 282-656 nM). Selectivity screening revealed that they were devoid of activity at mGlu1, mGlu2 and mGlu5 receptors, but modulated mGlu7 and mGlu8 receptors, thus were classified as group III-preferring mGlu receptor agents. None of the compounds was active towards hERG channels or in the mini-AMES test. The most potent in vitro mGlu4 PAM derivative 52 (N-(3-chloro-4-(5-(2-chlorophenyl)-1,2,4-oxadiazol-3-yl)phenyl)picolinamide) was readily absorbed after i.p. administration (male Albino Swiss mice) and reached a maximum brain concentration of 949.76 ng/mL. Five modulators (34, 37, 52, 60 and 62) demonstrated significant anxiolytic- and antipsychotic-like properties in the SIH and DOI-induced head twitch test, respectively. Promising data were obtained, especially for N-(4-(5-(2-chlorophenyl)-1,2,4-oxadiazol-3-yl)-3-methylphenyl)picolinamide (62), whose effects in the DOI-induced head twitch test were comparable to those of clozapine and better than those reported for the selective mGlu4 PAM ADX88178.