Synthesis and pharmacological activity of a series of dihydro-1H-pyrrolo[1,2-a]imidazole-2,5(3H,6H)-diones, a novel class of potent cognition enhancers

Photoinduced Radical Annulations of Tetrahydroisoquinoline Derivatives with 2-Benzothiazolimines: Highly Diastereoselective Synthesis of Fused Hexahydroimidazo[2,1-a]isoquinolines

We report herein a photoinduced radical 1,3-dipolar cycloaddition between the 2-benzothiazolimines and tetrahydroisoquinoline derivatives with an organo-photocatalyst. A variety of benzothiazole-based hexahydroimidazo[2,1-a]isoquinoline architectures with great synthetic value were conveniently and efficiently constructed in moderate to good yields and excellent diastereoselectivities with highly tolerant functional groups. Moreover, the practicality and utility of this protocol were demonstrated by scale-up synthesis and facile elaboration. Preliminary mechanistic investigations indicated that the reaction proceeded via a visible-light-induced radical 1,3-dipolar cycloaddition pathway. This finding is expected to stimulate a more extensive exploration of the green and concise synthesis of structurally diverse heterocyclic molecules in the synthetic community.

Multicomponent Domino Cyclization of Ethyl Trifluoropyruvate with Methyl Ketones and Amino Alcohols as A New Way to γ-Lactam Annulated Oxazacycles

A new route to bicyclic γ-lactams was found, which was proposed as a three-component cyclization of ethyl trifluoropyruvate with methyl ketones and 1,2-, 1,3-amino alcohols. As a result, a series of trifluoromethyl-substituted tetrahydropyrrolo [2,1-b]oxazol-5-ones and tetrahydropyrrolo[2,1-b][1,3]oxazine-6-ones was synthesized, in which the substituent at the nodal carbon atom was varied. The introduction of a twofold excess of ethyl trifluoropyruvate in reactions with amino alcohols and acetone made it possible to obtain the same bicycles, but functionalized with a hydroxyester fragment, which are formed due to four-component interactions of the reagents. Transformations with 2-butanone and aminoethanol lead predominantly to similar bicycles, while an analogous reaction with aminopropanol gives N-hydroxypropyl-2,3-dihydropyrrol-5-one. Almost all bicycles are formed as two diastereomers, the structure of which was determined using ¹H, ¹⁹F, ¹³C NMR spectroscopy, including two-dimensional experiments and XRD analysis. A domino mechanism for the formation of tetrahydropyrrolo[2,1-b]oxazacycles was proposed, which was confirmed by their stepwise synthesis through the preliminary preparation of the aldol and bis-aldol from ethyl trifluoropyruvate and methyl ketones.

Di-, tetra-, and perhydropyrrolo[1,2-a]imidazoles: The Methods of Synthesis and Some Aspects of Application

The review summarizes and systematizes the literature data on the synthesis and some aspects of application of pyrrolo[1,2-a]imidazoles. Synthetic approaches are grouped according to the degree of saturation of the product pyrroloimidazole ring. The bibliography of the review includes 110 sources over the last 15 years.

Pharmacological Profile of MP-101, a Novel Non-racemic Mixture of R- and S-dimiracetam with Increased Potency in Rat Models of Cognition, Depression and Neuropathic Pain

The racemic mixture dimiracetam negatively modulates NMDA-induced glutamate release in rat spinal cord synaptosomal preparations and is orally effective in models of neuropathic pain. In this study, we compared the effects of dimiracetam, its R- or S-enantiomers, and the R:S 3:1 non-racemic mixture (MP-101). In vitro, dimiracetam was more potent than its R- or S-enantiomers in reducing the NMDA-induced [³H]D-aspartate release in rat spinal cord synaptosomes. Similarly, acute oral administration of dimiracetam was more effective than a single enantiomer in the sodium monoiodoacetate (MIA) paradigm of painful osteoarthritis. Then, we compared the in vitro effects of a broad range of non-racemic enantiomeric mixtures on the NMDA-induced [³H]D-aspartate release. Dimiracetam was a more potent blocker than each isolated enantiomer but the R:S 3:1 non-racemic mixture (MP-101) was even more potent than dimiracetam, with an IC₅₀ in the picomolar range. In the chronic oxaliplatin-induced neuropathic pain model, MP-101 showed a significantly improved anti-neuropathic profile, and its effect continued one week after treatment suspension. MP-101 also performed better than dimiracetam in animal models of cognition and depression. Based on the benign safety and tolerability profile previously observed with racemic dimiracetam, MP-101 appears to be a novel, promising clinical candidate for the prevention and treatment of several neuropathic and neurological disorders.

Bis(Benzofuran-1,3-N,N-heterocycle)s as Symmetric and Synthetic Drug Leads against Yellow Fever Virus

The yellow fever virus (YFV) is an emerging RNA virus and has caused large outbreaks in Africa and Central and South America. The virus is often transmitted through infected mosquitoes and spreads from area to area because of international travel. Being an acute viral hemorrhagic disease, yellow fever can be prevented by an effective, safe, and reliable vaccine, but not be eliminated. Currently, there is no antiviral drug available for its cure. Thus, two series of novel bis(benzofuran−1,3-imidazolidin-4-one)s and bis(benzofuran−1,3-benzimidazole)s were designed and synthesized for the development of anti-YFV lead candidates. Among 23 new bis-conjugated compounds, 4 of them inhibited YFV strain 17D (Stamaril) on Huh-7 cells in the cytopathic effect reduction assays. These conjugates exhibited the most compelling efficacy and selectivity with an EC50 of <3.54 μM and SI of >15.3. The results are valuable for the development of novel antiviral drug leads against emerging diseases.

Structure-Activity Design, Synthesis and Biological Activity of Newer Imidazole- Triazine Clubbed Derivatives as Antimicrobial and Antitubercular Agents

Background:

Imidazole and triazine derivatives act as antimicrobial and antitubercular agents. 2D-QSAR determination estimates the pharmacological activity based on the thermodynamic properties of the structure.

Objective:

The structural arrangements and thermodynamic properties of the imidazole derivatives are necessary for the enhancement of pharmacological activity. So,imidazole-triazine clubbed derivatives were designed based on molecular modeling 2D-QSAR study on antitubercular activity.

Methods:

PLSR method is applied for 2D-QSAR determination of the (Z)-5-ethylidene-3-(4- methoxy-6-methyl-1,3,5-triazin-2-yl)-2-phenyl-3,5-dihydro-4H-imidazol-4-one (B1-B10). The designed compounds were synthesized and spectrally evicted by IR, 1H NMR, 13C NMR, and mass spectra data as well as biologically screened against the different antitubercular and antimicrobial species.

Result:

Compounds B4, B6, and B7 were found potent against the different antimicrobial species. Compound B3 was more effective against the M. tuberculosis H37Rv. Statistically significant QSAR model generated by PLSR methods showed external r2=0.9775 and internal q2=0.2798 predictive abilities. Furthermore, the model also incorporated three parameters, Polar Surface Area Excluding Pand S, Mom Inertia Y, and SsCH3 count, with their corresponding values for each molecule.

Conclusion:

The 2D-QSAR study revealed that antitubercular activity was directly proportional to the total surface area of the polar atoms having molecules and the moment of inertia on the Y-axis. At the same time, antitubercular activity was inversely proportional to the methyl group joined with a single bond. The present study afforded favorable results, which were further used to generate lead target molecules.

Furoxans (Oxadiazole-4 N-oxides) with Attenuated Reactivity are Neuroprotective, Cross the Blood Brain Barrier, and Improve Passive Avoidance Memory

Nitric oxide (NO) mimetics and other agents capable of enhancing NO/cGMP signaling have demonstrated efficacy as potential therapies for Alzheimer's disease. A group of thiol-dependent NO mimetics known as furoxans may be designed to exhibit attenuated reactivity to provide slow onset NO effects. The present study describes the design, synthesis, and evaluation of a furoxan library resulting in the identification of a prototype furoxan, 5a, which was profiled for use in the central nervous system. Furoxan 5a demonstrated negligible reactivity toward generic cellular thiols under physiological conditions. Nonetheless, cGMP-dependent neuroprotection was observed, and 5a (20 mg/kg) reversed cholinergic memory deficits in a mouse model of passive avoidance fear memory. Importantly, 5a can be prepared as a pharmaceutically acceptable salt and is observed in the brain 12 h after oral administration, suggesting potential for daily dosing and excellent metabolic stability. Continued investigation into furoxans as attenuated NO mimetics for the CNS is warranted.

Photoredox Approach to N-Acyl-N'-aryl-N,N'-aminals Using Enamides and Their Conversion to γ-Lactams

A photoredox catalytic approach to synthetically valuable N-acyl-N'-aryl-N,N'-aminals is described. This method uses the addition of a radical precursor to enamides, with subsequent interception of the cationic iminium intermediate with an arylamine. The reaction has been shown to be compatible with electron-rich and electron-deficient arylamines, and moderate to good levels of diastereoselectivity can be attained using a chiral enamide. Furthermore, the N-acyl-N'-aryl-N,N'-aminal reaction products can be readily cyclized, providing a novel synthetic route to valuable γ-lactams.

Biologically active γ-lactams: synthesis and natural sources

The γ-lactam moiety is present in a large number of natural and non-natural biologically active compounds. The range of biological activities covered by these compounds is very broad. Functionalized γ-lactams are thus of high interest and have great potential in medicinal chemistry. This review provides a description of the title compounds by focusing on their synthesis, natural sources and biological activities.

Synthesis of Polycyclic Imidazolidinones via Amine Redox-Annulation

α-Ketoamides undergo redox-annulations with cyclic secondary amines, such as 1,2,3,4-tetrahydroisoquinoline, pyrrolidine, piperidine, and morpholine. Catalytic amounts of benzoic acid significantly accelerate these transformations. This approach provides polycyclic imidazolidinone derivatives in typically good yields.

Synthesis, characterization and pharmacological screening of some novel 5-imidazopyrazole incorporated polyhydroquinoline derivatives

A new category of polyhydroquinoline derivatives 8a-t were synthesized in moderate to good yield (64-85%) by one-pot three-component cyclocondensation reaction of 5-(1H-imidazol-1-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde 3 with various enaminones 6a-h and different active methylene compounds (malononitrile 7a, ethylcaynoacetate 7b and caynoacetamide 7c) in absolute ethanol. The newly synthesized compounds were evaluated for their in vitro antimalarial activity against Plasmodium falciparum, in vitro antibacterial activity against a panel of pathogenic strains of bacteria and fungi and also for their antitubercular activity against Mycobacterium tuberculosis H37Rv strain. Two of them (8n, 8t) exhibited excellent antimalarial activity. Some of them exhibited excellent antibacterial activity and moderate antituberculosis activity compared with the first line drugs.

Broad spectrum and prolonged efficacy of dimiracetam in models of neuropathic pain

Dimiracetam, a bicyclic 2-pyrrolidinone derivative originally developed as cognition enhancer, is a member of the nootropic family for which anecdotal efficacy in models of neuropathic pain has been reported. Its antineuropathic activity was evaluated in established models of neuropathic pain induced by nerve injury, chemotherapy or MIA-induced osteoarthritis. Acutely, dimiracetam was very effective in models of antiretroviral drug induced painful neuropathy, oxaliplatin-induced hyperalgesia and in the MIA-osteoarthritis. Chronic dimiracetam dosing in the MIA and ART- induced models completely reverted hyperalgesia back to the level of healthy controls. Once reached, the maximal effect was maintained despite dose diminution and increased inter-dose interval. The effect of the last dose outlasted dimiracetam half-life longer than 12 times. In synaptosomal preparations, dimiracetam counteracted the NMDA-induced release of glutamate with highest potency in the spinal cord, possibly via NMDA receptor isoforms containing pH-sensitive GluN1 and GluN2A subunits. Dimiracetam appears to be a promising and safe treatment for neuropathic pain conditions for which there are very limited therapeutic options.

Study on action mechanism of 1-(4-methoxy-2-methylphenyl)piperazine (MMPP) in acquisition, formation, and consolidation of memory in mice

In the present study, the mechanism of action of MMPP (1-(4-methoxy-2-methylphenyl) piperazine) in the acquisition (pretraining administration), formation (posttraining administration), and consolidation (pretest administration) of memory was assessed in the passive avoidance test using a short- and long-term memory protocol in mice. MMPP modified avoidance in the acquisition and formation of memory protocols but not in the consolidation protocol. Scopolamine (0.1 mg/kg i.p.), dizocilpine (0.003 mg/kg i.p.), and buspirone (0.1 mg/kg i.p.) completely inhibited MMPP-induced effects on memory acquisition and partially inhibited memory formation in the short-term but not long-term paradigm. This suggested that cholinergic, N-methyl-D-aspartate (NMDA) and 5-hydroxytryptamine-1A (5-HT1A ) receptors were implicated in the MMPP-induced improvements in memory. The sedative, anxiolytic, motor impairment, myorelaxant, and anticonvulsive (pentylenetetrazole-induced seizures) properties of MMPP were also assessed with the compound only showing a nondose-dependent myorelaxation. These results suggest that MMPP can enhance acquisition and formation, but not consolidation, of memory in short-term and long-term protocol via cholinergic, NMDA-glutamatergic, and 5-HT1A receptors.

Microwave-assisted tandem transformation on an ionic-liquid support: efficient synthesis of pyrrolo/pyridobenzimidazolones and isoindolinone-fused benzimidazoles

A tandem transformation that involves the formation of three bonds and two heterocyclic rings in a one-pot fashion through amino-alkylation of an ionic-liquid-immobilized diamine with keto acids followed by successive double intramolecular cyclizations to afford a tricyclic framework has been explored. This tandem cyclization has been utilized to develop a rapid and efficient method to synthesize various pyrrolo[1,2-a]benzimidazolones and pyrido[1,2-a]benzimidazolones on an ionic-liquid support by using focused microwave irradiation. The application of this tandem cyclization was further extended to the aromatic keto acids to provide isoindolinone-fused benzimidazoles, a structurally heterogeneous library with skeletal diversity. The outcome of the cascade reaction was confirmed by the X-ray crystallographic study of the product directly attached to the ionic-liquid support. Use of the ionic liquid as a soluble support facilitates purification by simple precipitation along with advantages like high loading capacity, homogeneous reaction conditions, and monitoring of the reaction progress by regular conventional spectroscopic methods, whereas application of microwave irradiation greatly accelerates the rate of the reactions.

Synthesis and nootropic activity of some 2,3-dihydro-1H-isoindol-1-one derivatives structurally related with piracetam

Three 2,3-dihydro-1H-isoindol-1-ones structurally related with piracetam (=2-oxopyrrolidine-1-acetamide) have been synthesized and tested for their nootropic effects in the passive avoidance test in mice. Compounds (RS)-2, (R,R)-3, and (R,S)-3 were obtained in good yields in only two steps starting from methyl DL-phthaloylalanine. Compound (RS)-2 exhibited nootropic activity at lower doses than piracetam, used as reference drug, but it showed lower efficacy. Whereas diastereoisomers (R,R)-3 and (R,S)-3 were as potent as piracetam to revert amnesia induced by scopolamine, (R,S)-3 showed lower efficacy than (R,R)-3. Only (R,R)-3 showed myorelaxant effect at doses of 10 and 30 mg/kg; other compounds did not exhibit any anticonvulsant, sedative, myorelaxant, or impaired motor-coordination effect in mice. These synthesized 2,3-dihydro-1H-isoindol-1-one derivatives constitute a new kind of nootropic compounds.

Ion channel blockers for the treatment of neuropathic pain

Neuropathic pain, a severe chronic pain condition characterized by a complex pathophysiology, is a largely unmet medical need. Ion channels, which underlie cell excitability, are heavily implicated in the biological mechanisms that generate and sustain neuropathic pain. This review highlights the biological evidence supporting the involvement of voltage-, proton- and ligand-gated ion channels in the neuropathic pain setting. Ion channel modulators at different research or development stages are reviewed and referenced. Ion channel modulation is one of the main avenues to achieve novel, improved neuropathic pain treatments. Voltage-gated sodium and calcium channel and glutamate receptor modulators are likely to produce new, improved agents in the future. Rationally targeting subtypes of known ion channels, tackling recently discovered ion channel targets or combining drugs with different mechanism of action will be primary sources of new drugs in the longer term.

Unanticipated Stereoselectivity in the Reaction of Primaquine α-Aminoamides with Substituted Benzaldehydes: A Computational and Experimental Study

Imidazolidin-4-ones are commonly employed as skeletal modifications in bioactive oligopeptides, either as proline surrogates or for protection of the N-terminal amino acid against aminopeptidase- and endopeptidase-catalyzed hydrolysis. Imidazolidin-4-one synthesis usually involves the reaction of an alpha-aminoamide moiety with a ketone or an aldehyde to yield an imine, followed by intramolecular cyclization. We have unexpectedly found that imidazolidin-4-one formation is stereoselective when benzaldehydes containing o-carboxyl or o-methoxycarbonyl substituents are reacted with alpha-aminoamide derivatives of the antimalarial drug primaquine. A systematic computational and experimental study on the stereoselectivity of imidazolidin-4-one formation from primaquine alpha-aminoamides and various substituted benzaldehydes has been carried out, and they have allowed us to conclude that intramolecular hydrogen-bonds involving the C=O oxygen of the o-substituent play a crucial role.

Innovative synthesis of 4-carbaldehydepyrrolin-2-ones by zwitterionic rhodium catalyzed chemo- and regioselective tandem cyclohydrocarbonylation/CO insertion of alpha-imino alkynes

The tandem cyclohydrocarbonylative/CO insertion of alpha-imino alkynes employs CO, H(2), and catalytic quantities of zwitterionic rhodium complex (eta(6)-C(6)H(5)BPh(3))(-)Rh(+)(1,5-COD) and triphenyl phosphite affording aldehyde substituted pyrrolinones in 67-82% yields. This unique transformation is readily applied to imino alkynes containing alkyl, alkoxyl, vinyl, and aryl substituents. The ability to prepare highly functionalized pyrrolinones makes this an attractive route to these important and versatile pharmaceuticals.

Design, synthesis, and preliminary pharmacological evaluation of 1, 4-diazabicyclo[4.3.0]nonan-9-ones as a new class of highly potent nootropic agents

Several 4-substituted 1,4-diazabicyclo[4.3.0]nonan-9-ones have been synthesized and tested in vivo on mouse passive avoidance test, to evaluate their nootropic activity. The results show that they represent a new class of nootropic drugs with a pharmacological profile very similar to that of piracetam, showing much higher potency with respect to the reference. Among the compounds studied, 7 (DM 232) shows outstanding potency, being active at the dose of 0. 001 mg kg(-1) sc.

TRH mimetics: differentiation of antiamnesic potency from antidepressant effect

For the purpose of rational modification of the TRH molecule, we were pursuing an approach that consists of two steps: (1) 'obligatory' replacement of histidine with glutamine in TRH and (2) the application of conformational constraints for putative bioactive conformation I stabilized by an intramolecular hydrogen bond between C-terminal carboxamide proton and alpha-carbonyl of histidyl (glutaminyl), and conformation II formed by an intramolecular hydrogen bond between alpha-carbonyl of pyroglutamyl and prolinamide proton. Significant antiamnesic potency was discovered in the passive avoidance test (ECS and Scopolamine induced amnesia) for conformation II mimic (8S,10aS)-8-carbamoyl-1,2,3,6,7,8,9,10a- octahydro-5H,10H-pyrrolo[1,2-a][1,4]diazocin-5,10-dione (2) at doses of 0.1 and 1.0 mg/kg. EEG analysis indicates a mild activating effect of compound 2 on EEG, which is similar to that of piracetam and differs from hard amphetamine activation. Conformation I mimic 3-(2-carbamoylethyl)-2,3,6,7,8,8a-hexahydro-1H,4H-pyrrolo[1,2-a] pyrazin-1,4-dione (1) exhibited an antidepressant effect at a dose of 1 mg/kg. The transition from two putative quasi-cyclic bioactive conformations of TRH and its obligatory similar analogue [Gln2]-TRH to their cyclic mimics led to differentiation of antiamnesic and antidepressant activity of TRH.

Determination of the polar drug dimiracetam in human plasma and serum by column-switching high-performance liquid chromatography

A sensitive and fully automated column-switching HPLC method was developed for the determination of a novel cognition enhancer, dimiracetam, in human plasma and serum. A sample of plasma was ultrafiltered and then directly injected onto a first mu Bondapak C18 column. The sample was eluted with water. The portion of the eluate (heart-cut) from this column containing the drug was selected and loaded on a second mu Bondapak C18 column and eluted with water. During the elution of the second column, the first column was automatically rinsed with water-acetonitrile (50:50, v/v) and then equilibrated for a new injection. The total analysis time for each sample was 35 min. This corresponded to a 30% decrease in analysis time compared with the time that would have been needed with a simple run with two mu Bondapak C18 columns assembled in series. Ultraviolet detection at 200 nm was used to monitor the eluate. The method was fully validated over the quantitation range 27 ng/ml-15 micrograms/ml. The applicability of the method was demonstrated by analysis of serum samples from a study performed in human healthy volunteers.