Mesomeric Betaines Based on Adamantylated 1,2,4-Triazolo[4,3-a]pyrimidin-5-ones: Synthesis, Structure and Conversion into Anionic N-Heterocyclic Carbenes.

The C-N coupling of 1,2,4-triazolo[1,5-a]pyrimidin-7-ones with 1-adamantanol/1-bromoadamantane leads to 1,2,4-triazolo[4,3-a]pyrimidinium-5-olates, which are represented as mesomeric betaines (MBs). The formation of MBs involves not only N-alkylation of heterocyclic framework but also the rearrangement leading to a change in the type of fusion between pyrimidine and 1,2,4-triazole fragments. The structures of the obtained products were confirmed by the X-ray analysis and measurements of 13 C-13 C (JCC ) coupling constants in the 1D 13 C NMR spectra of selectively 13 C-labeled samples. Treatment of the betaines with lithium bis(trimethylsilyl)amide (LiHMDS) gave anionic carbenes, which were detected by 13 C NMR spectroscopy and were trapped by reactions with phenyl isothiocyanate and sulfur. Density functional theory (DFT) and the quantum theory of atoms in molecules (QTAIM) analyses allowed for an insight into the electronic structure of the obtained betaines and N-heterocyclic carbene derivatives.

15N Chemical Shifts and JNN-Couplings as Diagnostic Tools for Determination of the Azide-Tetrazole Equilibrium in Tetrazoloazines.

Selectively 15N-labeled tetrazolo[1,5-b][1,2,4]triazines and tetrazolo[1,5-a]pyrimidines bearing one, two, or three 15N labels were synthesized. The synthesized compounds were studied by 1H, 13C, and 15N NMR spectroscopy in DMSO and TFA solutions, where the azide-tetrazole equilibrium can lead to the formation of two tetrazole (T, T') isomers and one azide (A) isomer for each compound. Incorporation of the 15N-label(s) leads to the appearance of 15N-15N coupling constants (JNN), which can be easily measured via simple 1D 15N NMR spectra, even at natural abundance between labeled and unlabeled 15N atoms. The chemical shifts for the 15N nuclei in the azole moiety are very sensitive to the ring opening and azide formation, thus providing information about the azido-tetrazole equilibrium. At the same time, the 1-2JNN couplings between 15N-labeled atoms in the azole and azine fragments unambiguously determine the fusion type between tetrazole and azine rings in the cyclic isomers T and T'. Thus, combined analysis of 15N chemical shifts and JNN values in selectively isotope-enriched compounds provides an effective diagnostic tool for direct structural determination of tetrazole isomers and azide form in solution. This method was found to be the most simple and efficient way to study the azido-tetrazole equilibrium.

Psychopharmacological characterization of an emerging drug of abuse, a synthetic opioid U-47700, in adult zebrafish.

3,4-Dichloro-N-[2-(dimethylamino)cyclohexyl]-N-methylbenzamide (U-47700) is a selective µ-opioid receptor agonist originally synthesized as a prospective analgesic drug. Several times more potent than morphine, U-47700 has high abuse potential and may cause clinical neurotoxicity, euphoria, respiratory depression and occasional mortality. U-47700 also evokes analgesia, sedation and euphoria-like states in both humans and rodents. Despite the growing use and abuse of U-47700, its psychopharmacological and toxicological profiles in vivo remain poorly understood. The zebrafish (Danio rerio) is rapidly becoming a popular aquatic model organism for central nervous system (CNS) disease modeling and drug discovery. Here, we examine acute (1, 5, 10, 25 and 50 mg/L for 20-min) and chronic (0.1, 0.5 and 1 mg/L for 14 days) effects of U-47700 in adult zebrafish. Overall, we found overt sedation evoked in fish by acute, and hyperlocomotion with an anxiolytic-like action by chronic, drug treatments. Acute treatment with 1 and 10 mg/L U-47700 also resulted in detectable amounts of this drug in the brain samples, supporting its permeability through the blood-brain barrier. Collectively, these findings emphasize complex dose- and treatment-dependent CNS effects of U-47700 following its acute and chronic administration. Our study also supports high sensitivity of zebrafish to U-47700, and suggests these aquatic models as promising in-vivo screens for probing potential CNS effects evoked by novel synthetic opioid drugs.

Dibenzo[f,h]furazano[3,4-b]quinoxalines: Synthesis by Intramolecular Cyclization through Direct Transition Metal-Free C-H Functionalization and Electrochemical, Photophysical, and Charge Mobility Characterization.

Herein, we describe the synthesis of unsymmetrically substituted dibenzo[f,h]furazano[3,4-b]quinoxalines by intramolecular cyclization through direct transition metal-free C-H functionalization. The electrochemical and photophysical properties for several polycycles have been measured. In thin films of the dibenzo[f,h]furazano[3,4-b]quinoxalines, hole mobility is in the order of 10-4 cm2 V-1 s-1. The results show that the HOMO and LUMO energy levels are appropriate for using the compounds as hole-transport materials in thin-film devices, in particular, organic and perovskite solar cells.

Nitrothiadiazolo[3,2-a]pyrimidines as promising antiglycating agents.

Managing the advanced glycation end-products (AGEs) concentration is a reliable approach to achieve control over the pathogenesis of diabetic vascular complications. Inhibition of dipeptidyl peptidase-4 (DPP-4) is also an attractive way to tackle type 2 diabetes mellitus (T2DM). We showed previously that azoloazine heterocycles have the potential to prevent the formation of AGEs and in this work, we conducted docking studies with DPP-4 of 5-alkylamino-6-nitro-1,3,4-thiadiazolo[3,2-a]pyrimidines. Consequently, we have developed a synthetic approach to these structures by chlorodeoxygenation and amination reactions. Antidiabetic properties of obtained compounds were studied by evaluating DPP-4 (ex vivo/in vitro) and AGEs formation inhibition (in vitro). It was shown that the nitrothiadiazolopyrimidines exhibit a higher antiglycation activity than reference compound aminoguanidine, but only moderate inhibition of DPP-4. The most active DPP-4 inhibitor 1l had IC50 of 55.87 µM and showed the ability to inhibit serum DPP-4 activity in rats after 10 mg/kg oral administration but with the less and shorter effect than vildagliptin. At the same time, 1l was the most active antiglycating compound in the series (IC50 134.4 µM). Copper chelation properties of synthesized compounds were also investigated since the formation of AGEs is catalyzed by the transition metal cations. A noticeable correlation between antiglycation activity and metal chelation was revealed. Both activities (antiglycation and copper chelation) correlated with quantum-chemical properties (calculated with ab initio) of the tested compounds. These findings will allow us to predict both activities in the future, without the need to model multiple steps of glycation reaction.

When fish take a bath: Psychopharmacological characterization of the effects of a synthetic cathinone bath salt 'flakka' on adult zebrafish.

Alpha-pyrrolidinopentiophenone (α-PVP) is a synthetic cathinone which exerts robust mental and physiological effects clinically, as well as causes aberrant stereotypic behaviors and altered locomotion in rodents. Given the rich spectrum of pharmacological activity of α-PVP in rodents and humans, as well as its high abuse potential, further studies are needed to better understand the pharmacology and toxicology of this drug. The zebrafish (Danio rerio) is a relatively novel model organism in neuropharmacology and toxicology research. Here, we characterize behavioral effects of α-PVP in adult zebrafish following its acute (1, 5, 25 and 50 mg/L for 20 min) and chronic (1, 5 and 10 mg/L for 7 days) treatments. Overall, acute exposure to α-PVP evoked psychostimulant (but not anxiolytic-like) effects in zebrafish novel tank test, with characteristic stereotypic 'side-to-side' bottom swimming at 5, 25 and 50 mg/L. The high-performance liquid chromatography/high-resolution mass spectrometry (HPLC/HRMS) analyses of zebrafish brains showed detectable levels of α-PVP following its acute administration, likely underlying the observed behavioral effects. Although acute 2-day discontinuation of chronic 7-day α-PVP at 1, 5 and 10 mg/L produced no effects, hypolocomotion occurred after a 7-day chronic treatment and repeated withdrawal, resembling rodent effects of some chronic psychostimulants. Collectively, these findings support zebrafish sensitivity to α-PVP and show some parallels with its effects in mammals and humans. This study also suggests that aquatic models based on zebrafish can help further examine the CNS effects evoked by α-PVP and screen for related synthetic new psychoactive drugs.

15N-Labelling and structure determination of adamantylated azolo-azines in solution.

Determining the accurate chemical structures of synthesized compounds is essential for biomedical studies and computer-assisted drug design. The unequivocal determination of N-adamantylation or N-arylation site(s) in nitrogen-rich heterocycles, characterized by a low density of hydrogen atoms, using NMR methods at natural isotopic abundance is difficult. In these compounds, the heterocyclic moiety is covalently attached to the carbon atom of the substituent group that has no bound hydrogen atoms, and the connection between the two moieties of the compound cannot always be established via conventional 1H-1H and 1H-13C NMR correlation experiments (COSY and HMBC, respectively) or nuclear Overhauser effect spectroscopy (NOESY or ROESY). The selective incorporation of 15N-labelled atoms in different positions of the heterocyclic core allowed for the use of 1H-15N (JHN) and 13C-15N (JCN) coupling constants for the structure determinations of N-alkylated nitrogen-containing heterocycles in solution. This method was tested on the N-adamantylated products in a series of azolo-1,2,4-triazines and 1,2,4-triazolo[1,5-a]pyrimidine. The syntheses of adamantylated azolo-azines were based on the interactions of azolo-azines and 1-adamatanol in TFA solution. For azolo-1,2,4-triazinones, the formation of mixtures of N-adamantyl derivatives was observed. The JHN and JCN values were measured using amplitude-modulated 1D 1H spin-echo experiments with the selective inversion of the 15N nuclei and line-shape analysis in the 1D 13С spectra acquired with selective 15N decoupling, respectively. Additional spin-spin interactions were detected in the 15N-HMBC spectra. NMR data and DFT (density functional theory) calculations permitted to suggest a possible mechanism of isomerization for the adamantylated products of the azolo-1,2,4-triazines. The combined analysis of the JHN and JCN couplings in 15N-labelled compounds provides an efficient method for the structure determination of N-alkylated azolo-azines even in the case of isomer formation. The isomerization of adamantylated tetrazolo[1,5-b][1,2,4]triazin-7-ones in acidic conditions occurs through the formation of the adamantyl cation.

Switchable Synthesis of 4,5-Functionalized 1,2,3-Thiadiazoles and 1,2,3-Triazoles from 2-Cyanothioacetamides under Diazo Group Transfer Conditions.

High yield solvent-base-controlled, transition metal-free synthesis of 4,5-functionalized 1,2,3-thiadiazoles and 1,2,3-triazoles from 2-cyanothioacetamides and sulfonyl azides is described. Under diazo transfer conditions in the presence of a base in an aprotic solvent 2-cyanothioacetamides operating as C-C-S building blocks produce 5-amino-4-cyano-1,2,3-thiadiazoles exclusively. The use of alkoxide/alcohol system completely switches the reaction course due to the change of one of the reaction centers in the 2-cyanothioacetamide (C-C-N building block) resulting in the formation of 5-sulfonamido-1,2,3-triazole-4-carbothioamide sodium salts as the only products. The latter serve as good precursors for 5-amino-1,2,3-thiadiazole-4-carboximidamides, the products of Cornforth-type rearrangement occurring in neutral protic medium or under acid conditions. According to DFT calculations (B3LYP/6-311+G(d,p)) the rearrangement proceeds via intermediate formation of a diazo compound, and can be catalyzed by acids via the protonation of oxygen atom of the sulfonamide group.

Mass spectrometric properties of N-(2-methoxybenzyl)-2-(2,4,6-trimethoxyphenyl)ethanamine (2,4,6-TMPEA-NBOMe), a new representative of designer drugs of NBOMe series and derivatives thereof.

Emergence of new psychoactive substances, hallucinogenic phenethylamines in particular, in illicit market is a serious threat to human health in global scale. We have detected and identified N-(2-methoxybenzyl)-2-(2,4,6-trimethoxyphenyl)ethanamine (2,4,6-TMPEA-NBOMe), a new compound in NBOMe series. Identification was achieved by means of gas chromatography/mass spectrometry (GC/MS), including high-resolution mass spectrometry with tandem experiments (GC/HRMS and GC/HRMS2 ), ultra-high performance liquid chromatography/high-resolution mass spectrometry with tandem experiments (UHPLC/HRMS and UHPLC/HRMS2 ), and 1 H and 13 C nuclear magnetic resonance spectroscopy. The peculiarities of fragmentation of the compound under electron ionization (EI) and collision-induced dissociation were studied. Despite of the empirical rule denying migration of the hydrogen atom in McLafferty rearrangement to the benzene ring with substituents in the both ortho-positions, it easily occurs for 2,4,6-TMPEA-NBOMe in EI conditions. We have noticed that electron-donating substituents, e.g. methoxy groups in the both ortho-positions and para-positions favor the rearrangement. For specially synthesized N-methyl and N-acyl derivatives McLafferty rearrangement is not observed. N-Acyl derivatives demonstrate McLafferty rearrangement, but the charge retains at the alternative fragment involving N-acyl carbonyl group. We have also showed that the hydrogen atoms in 2,4,6-trimethoxybenzene ring may be easily substituted for deuterium or for strong electrophiles like trifluoroacetyl. Analytical characteristics of 2,4,6-TMPEA-NBOMe and of some derivatives thereof which enable their determination in various criminal seizures are given. Copyright © 2016 John Wiley & Sons, Ltd.

Synthetic cannabinoid 3-benzyl-5-[1-(2-pyrrolidin-1-ylethyl)-1H-indol-3-yl]-1,2,4-oxadiazole. The first detection in illicit market of new psychoactive substances.

We were the first to detect 3-benzyl-5-[1-(2-pyrrolidin-1-ylethyl)-1H-indol-3-yl]-1,2,4-oxadiazole (given name BzODZ-EPyr) as a new synthetic cannabinoid, in illegal market of new psychoactive compounds (NPS). The compound was known only from pharmaceutical literature so far. BzODZ-EPyr was identified by means of gas chromatography/mass spectrometry (GC/MS) including high resolution mass spectrometry (GC/HRMS), ultra-high performance liquid chromatography/high resolution tandem mass spectrometry (UHPLC/HRMS(2)), Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR) (1)H and (13)C. The peculiarities of mass-spectral fragmentation in experiments in electronic ionization (EI) and collision-induced dissociation (CID) modes were studied. Herewith we report analytical characteristics of BzODZ-EPyr enabling its (and possible analogues thereof) determination in criminal seizures.

Identification and analytical characteristics of synthetic cannabinoids with an indazole-3-carboxamide structure bearing a N-1-methoxycarbonylalkyl group.

Illicit new psychoactive substances (NPS) are a serious threat to health throughout the world. Such NPS do not usually pass preliminary pharmacological trials. In 2014, we identified a series of five new synthetic cannabinoids with an indazole-3-carboxamide structure bearing an N-1-methoxycarbonylalkyl group. The compounds have very high cannabimimetic activity which has caused mass severe intoxication and deaths. The compounds were identified by means of gas chromatography-mass spectrometry (GC-MS), including high-resolution mass spectrometry (GC-HRMS), ultra-high-performance liquid chromatography-high-resolution tandem mass spectrometry (UHPLC-HRMS(2)), and (1)H and (13)C nuclear magnetic resonance spectroscopy (NMR). The peculiarities of mass-spectral fragmentation of the compounds after electron ionization (EI) ionization and collision-induced dissociation (CID) were studied. The analytical characteristics reported for the compounds will enable their identification in a variety of materials seized from criminals.Graphical Abstract.

Synthetic cannabinoids as designer drugs: new representatives of indol-3-carboxylates series and indazole-3-carboxylates as novel group of cannabinoids. Identification and analytical data.

By means of gas chromatography with mass spectrometry detection (GC-MS), including high resolution mass spectrometry (GC-HRMS) together with ultra-high performance liquid chromatography in combination with high resolution tandem mass spectrometry (UHPLC-HRMS), nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR), structure of new synthetic cannabinoids, representatives of indol- and indazole-3-carboxylates groups, used in smoke mixtures, was determined. Obtained analytical data make reliable identification of these compounds in a course of analysis of criminal seizures possible.

3-Naphthoylindazoles and 2-naphthoylbenzoimidazoles as novel chemical groups of synthetic cannabinoids: chemical structure elucidation, analytical characteristics and identification of the first representatives in smoke mixtures.

By means of gas chromatography with mass spectrometry detection (GC-MS), including high resolution mass spectrometry (GC-HRMS) together with ultra-high performance liquid chromatography in combination with high resolution tandem mass spectrometry (UHPLC-HRMS), nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR), structure of novel synthetic cannabinoids, namely, 1-(5-fluoropentyl)-1H-indazol-3-yl(naphthalen-1-yl)methanone, naphthalen-1-yl(1-pentyl-1H-benzo[d]imidazol-2-yl)methanone and 1-(5-fluoropentyl)-1H-benzo[d]imidazol-2-yl(naphthalen-1-yl)methanone was established. Analytical data obtained in the paper enable reliable identification of these compounds during qualitative analysis of seizures, including smoke mixtures.

Analytical characterization of some synthetic cannabinoids, derivatives of indole-3-carboxylic acid.

By means of gas chromatography with high resolution mass spectrometry (GC-HRMS), ultra-high performance liquid chromatography in combination with high resolution tandem mass spectrometry (UHPLC-HRMS), nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR), structure of a series from a novel synthetic cannabinoids, derivatives of indole-3-carboxylic acid, was established. Methods for determination of the compounds in mixtures, involving chromatographic separation with mass-spectroscopic determination, were elaborated. Analytical data obtained in the paper will make reliable identification of synthetic cannabinoids of the new type during forensic examination possible.

Identification and analytical properties of new synthetic cannabimimetics bearing 2,2,3,3-tetramethylcyclopropanecarbonyl moiety.

By means of gas chromatography with mass spectrometry detector (GC-MS), liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR), structure of a series from a novel class of synthetic cannabimimetics bearing 2,2,3,3-tetramethylcyclopropanecarbonyl moiety was established. It was found that this fragment could undergo thermal ring-opening into isomeric structures. The title compounds under action of hydrochloric acid can transform into new compounds which structure is discussed in the paper. The compounds identified could be referred to a new class of 'designer drugs' and are in illegal turnover in Russia and Belarus since the summer of 2011. Analytical data obtained in the paper will make possible reliable identification of such new 'designer drugs' during forensic examination.

Self condensation of enamines mediated by acetylation. A novel approach to 1-(azol-5-yl)-(1E,3Z)-butadiene-4-N,N-dimethylamines.

Novel self-condensation of 3-(azol-5-yl)-1,1-dimethylenamines has been found to form new C-C bonds leading to 2,4-(1,2,3-triazole-1,2,3-thiadiazole-3-phenylisothiazole)-(1E,3Z)-5-yl-butadiene-1-amines. The discovered reaction represents a new example of C-H functionalization in unsaturated systems and can serve an efficient synthetic approach to rational design of new 2,4-(diazole-5-yl)-dieneamines.

The tert-amino effect in heterocyclic chemistry. Synthesis of spiro heterocycles.

The tert-amino reaction effect was examined. A new method to synthesize spiro heterocycles is presented. It was shown that the "tert-amino effect" could be applied to the formation of spiro-fused heterocycles. The formation of spiro compounds proceeds in most cases in good yields in a one-pot reaction.