Occurrence of Morpholine in Central Nervous System Drug Discovery

Chronic dimethomorph exposure induced behaviors abnormalities and cognitive performance alterations in adult zebrafish (Danio rerio)

Dimethomorph is a systematic fungicide that inhibits sterol synthesis in fungi and unfortunately, there was only scarce data regarding its toxicity. Therefore, considering its extensive application in agriculture and its presence in food residues and the environment, its toxicities in non-target organisms, including aquatic animals, are required to be evaluated since they are sensitive indicators of ecological change. In this study, we evaluated the toxicities of dimethomorph after chronic exposure to adult zebrafish (Danio rerio) by conducting various behavioral assays, a passive avoidance test, and biochemical assays by ELISA. From the results, ∼ 2 weeks exposure to dimethomorph caused lower locomotion, aggressiveness, and conspecific social interaction, and more robust predator avoidance behaviors. Furthermore, alterations in color preferences and short-term memory loss were also observed in the treated fish. In helping to elucidate the mechanism, the expression level of several important neurotransmitters in the brain tissue was measured. Interestingly, increment in several biomarkers, including serotonin, kisspeptin, epinephrine, norepinephrine, and dopamine was observed in the treated group along with a slight increase in other tested neurotransmitters, which were catalase, acetylcholine, and melatonin, which might play a role in the observed behavior alterations. Nevertheless, the results from the current study suggested possible alterations in the central nervous system by dimethomorph, and thus, consideration is required prior to the usage of this fungicide in the agricultural fields surrounding natural freshwater reservoirs.

Photocatalytic Synthesis of Substituted 2-Aryl Morpholines via Diastereoselective Annulation

Morpholines are prevalent in medicinal chemistry due to their favorable pharmacokinetic properties and widespread presence in FDA-approved drugs. Existing methods for morpholine synthesis often require prefunctionalized or protected reagents, limiting their versatility and efficiency. Here, we present a photocatalytic, diastereoselective annulation strategy for the synthesis of morpholines directly from readily available starting materials. This method employs a visible-light-activated photocatalyst, Lewis acid, and Brønsted acid to achieve high yields and stereoselectivity. It also provides access to diverse substitution patterns, including challenging tri- and tetra-substituted morpholines. Mechanistic studies reveal that the reaction proceeds through the formation of a radical cation intermediate, with triflic acid playing critical roles in protonating the substrate, preserving the photocatalyst, and preventing product oxidation. Beyond morpholines, this strategy is extended to piperidines, pyrrolidines, and other privileged nitrogen heterocycles. Our findings provide a modular approach for constructing complex, medicinally valuable scaffolds, advancing both synthetic and medicinal chemistry.

Development of Off-On Near-Infrared Fluorescent Probes for Sensitive In Vivo Imaging of Amyloid-β Species with Enhanced Pharmacokinetics

The fluorescent imaging of pathologically accumulated β-amyloid (Aβ) proteins is of significant importance to the diagnosis of Alzheimer's disease (AD). In the paper, we prepare two new NIR probes, NIR-1 and NIR-2, through hydrophilic modification of introducing water-soluble bioactive groups such as polyethylene glycol (PEG) and morpholine to tune in vivo pharmacokinetics for specific detection of soluble and insoluble Aβ species. The in vitro assessments confirm that both NIR-1 and NIR-2 display strong near-infrared (NIR) fluorescence (FL) enhancement upon interaction with Aβ42 monomers, oligomers or aggregates (λem>670 nm) and show highly sensitive, rapid and selective response towards Aβ42 species. After i. v. injection, each probe showed fast blood-brain barrier (BBB) penetration and immediately produced intense FL signals in the brain of APP/PS1 AD model mice at 10 min. Moreover, compared with NIR-2, NIR-1 bearing a hydrophilic PEG chain displayed not only more rapid clearance but also lower background signal to efficiently distinguish APP/PS1 mice and wild-type mice with higher signal-to-background ratio, which was further validated by ex vivo histological staining of brain tissues. Therefore, due to its excellent pharmacokinetics, NIR-1 shows great promise as an effective NIR probe for specific detection of Aβ species.

Microwave-Assisted Synthesis of Morpholine-Based Chalcones as Reversible MAO-A Inhibitors in the Management of Mental Depression

Background: Depression is one of the most serious and common health problems among the youth population and is responsible for the initiation of many diseases. As per the World Health Organization, 3.8% of the population suffers from mental depression, globally. The monoamine oxidase-A (MAO-A) enzyme is responsible for the degradation of neurotransmitters leading to lower levels of neurotransmitters. Methods: Chalcones (C1-C15) were synthesized by reacting substituted acetophenone with various benzaldehydes in a basic ethanolic solvent at 80 °C under microwave irradiation conditions. To compare the reaction time and product yield, a conventional method of synthesis of chalcones was also performed. The synthesized chalcones (C1-C15) were spectroscopically characterized and screened initially for inhibitory activities against MAO-A and MAO-B. The best active compounds were undertaken for IC50 determination against MAO-A enzyme followed by the reversibility of inhibition analysis and the antioxidant assay. Moreover, in silico molecular docking and ADME pharmacokinetic investigations were accomplished. Results: Most of the compounds inhibited MAO-A, specifically, compounds C14 and C6 exhibited the highest inhibition at IC50 values of 7.91 ± 0.08 μM and 8.45 ± 0.19 μM, respectively. Both these compounds exhibited a reversible MAO-A inhibition displaying up to 60% recovery of enzymatic activity when diluted with substrate (Tyramine). The results of the in silico study indicated docking scores of -9.56 Kcal/mol (C14) and -9.45 Kcal/mol (C6) and exhibited a π-π stacking interaction with the crucial amino acid Trp-397. The compounds were determined to cross the blood-brain barrier (BBB) and displayed favorable gastrointestinal (GI) absorption. Further, the antioxidant assay results demonstrated that the synthesized compounds possess modest free radical scavenging potential. Conclusions: This study displayed the MAO-A inhibitory potential of morpholine-substituted chalcones as a promising pharmacophore for the development of novel antidepressant lead compounds.

Short Scalable Route to Bis-morpholine Spiroacetals and Oxazepane Analogues: Useful 3D-Scaffolds for Compound Library Assembly

sp3-Rich molecular scaffolds incorporating nitrogen heterocycles represent important starting points for assembling compound screening libraries and drug discovery. Herein, we report a four-step synthesis of a conformationally well-defined sp3-rich scaffold incorporating two morpholine rings embedded within a spiroacetal framework. The synthesis involves the intermediacy of a 2-chloromethyl-substituted morpholine, accessed from epichlorohydrin and readily available β-aminoalcohols. Base-mediated dehydrochlorination affords an exocyclic enol ether, from which the second morpholine ring is constructed in two steps. Scaffold synthesis is high-yielding and can be performed on a large scale. The methodology allows ready substitution of one-or both- of the morpholine rings for 1,4-oxazepanes and the generation of 6,7- and 7,7-spiroacetal analogues, which are virtually unexplored in drug discovery. Substituted 6,6-systems can be prepared and, in some instances, undergo acid-mediated anomerization to deliver the scaffolds in high diastereoselectivity. The two amine functionalities embedded in the 6,6- and 6,7-spiroacetal scaffolds were sequentially functionalized to provide a diverse physical compound library. These library compounds occupy a similar chemical space to small-molecule drugs that have been approved for clinical application by the Food and Drug Administration yet are structurally dissimilar and may therefore act upon novel targets, representing attractive starting materials for drug discovery.

One-Pot Aminomethylation of Heteroarenes by Rongalite as In Situ C1 Source

Rongalite-mediated one-pot aminomethylation of heteroarenes using secondary amines/anilines has been developed. This transition-metal-free and mild reaction offers an efficient way to synthesize aminomethylated heteroaromatic compounds with high yields and broad functional group tolerance. Here, Rongalite plays a key role in generating the C1 unit source in situ, which triggers the aminomethylation process. This approach provides a library of aminomethylated imidazo[1,2-a]pyridines and imidazo[2,1-b]thiazoles.

Transparent Machine Learning Model to Understand Drug Permeability through the Blood-Brain Barrier

The blood-brain barrier (BBB) selectively regulates the passage of chemical compounds into and out of the central nervous system (CNS). As such, understanding the permeability of drug molecules through the BBB is key to treating neurological diseases and evaluating the response of the CNS to medical treatments. Within the last two decades, a diverse portfolio of machine learning (ML) models have been regularly utilized as a tool to predict, and, to a much lesser extent, understand, several functional properties of medicinal drugs, including their propensity to pass through the BBB. However, the most numerically accurate models to date lack in transparency, as they typically rely on complex blends of different descriptors (or features or fingerprints), many of which are not necessarily interpretable in a straightforward fashion. In fact, the "black-box" nature of these models has prevented us from pinpointing any specific design rule to craft the next generation of pharmaceuticals that need to pass (or not) through the BBB. In this work, we have developed a ML model that leverages an uncomplicated, transparent set of descriptors to predict the permeability of drug molecules through the BBB. In addition to its simplicity, our model achieves comparable results in terms of accuracy compared to state-of-the-art models. Moreover, we use a naive Bayes model as an analytical tool to provide further insights into the structure-function relation that underpins the capacity of a given drug molecule to pass through the BBB. Although our results are computational rather than experimental, we have identified several molecular fragments and functional groups that may significantly impact a drug's likelihood of permeating the BBB. This work provides a unique angle to the BBB problem and lays the foundations for future work aimed at leveraging additional transparent descriptors, potentially obtained via bespoke molecular dynamics simulations.

Exploring the Potential of Nasal Drug Delivery for Brain Targeted Therapy: A Detailed Analysis

The brain is a sensitive organ with numerous essential functions and complex mechanisms. It is secluded and safeguarded from the external environment as part of the central nervous system (CNS), serving as a sanctuary. By regulating their selective and specific absorption, efflux, and metabolism in the brain, the CNS controls brain homeostasis and the transit of endogenous and foreign substances. The mechanism which protects the brain from environmental chemicals, also prevent the entry of therapeutic chemicals to it. The delivery of molecules to the brain is hindered by several major barriers, such as the blood-brain barrier (BBB), blood-cerebrospinal fluid barrier (BCSFB), and blood-tumor barrier. BBB is formed by the combination of cerebral endothelial cells, astrocytes, neurons, pericytes and microglia. It is a tight junction of capillary endothelial cells, preventing the diffusion of solute into the brain. BCSFB is the second barrier, located at the choroid plexus, separating the blood from cerebrospinal fluid (CSF). It is comparatively more permeable than BBB. An uneven distribution of microvasculature across the tumor interstitial compromises drug delivery to neoplastic cells of a solid tumor, resulting in spatially inconsistent drug administration. Nasal drug delivery to the brain is a method of drug delivery that tries to deliver therapeutic substances directly from the nasal cavity to the central nervous system including the brain. In this review, besides the role of barriers we have discussed in detail about approaches adapted to deliver drugs to the brain along with mechanisms through nasal route. Further, different commercial formulations, clinical trials and patents have been thoroughly elaborated to date. The findings suggest that the nose-to-brain drug delivery method holds promise as an evolving approach, potentially contributing to the specific and targeted delivery of drugs into the brain.

Oxidative Remote Aryl Rearrangement of N-Cinnamyl-N-alkoxybenzyl Sulfonamides Using Hypervalent Iodine(III)

An oxidative remote aryl rearrangement of N-cinnamyl-N-alkoxybenzyl sulfonamides with a hypervalent iodine(III) compound was developed to furnish 5,6-disubstituted 1,3-oxazinanes in high yields. This reaction proceeded through the dearomatization of the alkoxybenzene ring on the benzyl group, which acts as a good aryl donor, inducing the regioselective installation of the aryl group and the oxygen atom via cascade transformation. An enantioselective oxidative remote aryl rearrangement using C2-symmetrical chiral iodoarene gave enantioenriched products with high enantioselectivity.

Substitution Effects on Subcellular Organelle Localization in Live-cell Imaging

A series of D-π-A indole-containing fluorescent probes were developed, followed by an investigation of their photophysical properties and compounds' suitability for subcellular imaging in living cells. We demonstrate that the preference for mitochondrial localization was lost when morpholine was substituted, resulting in the accumulation of the molecule in the lysosomes. However, interestingly, the presence of a nitro group led to their localization within the lipid droplets despite the presence of the morpholine pendant. We also showcase the probes' sensitivity to pH, the influence of added chloroquine, and the temperature response on the changes in fluorescence intensity within lysosomes. The design of the probes with strong intramolecular charge transfer and substantial Stokes shift could facilitate extensive application in various cellular lysosomal models and contribute to a better understanding of the mechanisms involved in stimuli-responsive diseases.

Integrating 3,4-Dihydro-2H-1,4-oxazine into Peptides as a Modification: Silver Triflate-Catalyzed Cyclization of N-Propargyl N-Sulfonyl Amino Alcohols for SPPS Applications

We present a methodology yielding 3,4-dihydro-2H-1,4-oxazine by cyclization of N-propargyl N-sulfonyl amino alcohols using silver triflate as a catalyst at ambient temperature. Additionally, we showcase the applicability of this methodology in solid phase peptide synthesis (SPPS) to introduce the oxazine heterocyclic ring into short peptides containing serine and threonine. Notably, Rink amide resin supported the on-resin formation of 3,4-dihydro-2H-1,4-oxazine, while 2-CTC resin facilitated the oxazine formation in a one-pot process involving peptide cleavage, deprotection, and subsequent C-O ring formation, thus offering a versatile method for the late-stage modification of peptides.

Synthesis and Characterization of Copper(II) and Nickel(II) Complexes with 3-(Morpholin-4-yl)propane-2,3-dione 4-Allylthiosemicarbazone Exploring the Antibacterial, Antifungal and Antiradical Properties

The eleven new copper(II) and nickel(II) coordination compounds [Cu(L)Br]2 (1), [Cu(L)Cl] (2), [Cu(L)NO3] (3), [Ni(L)Cl] (4), [Ni(HL)2](NO3)2 (5), and [Cu(A)(L)]NO3, where A is 1,10-phenanthroline (6), 2,2'-bipyridine (7), 3,4-dimethylpyridine (8), 3-methylpyridine (9), pyridine (10) and imidazole (11) were synthesized with 3-(morpholin-4-yl)propane-2,3-dione 4-allylthiosemicarbazone (HL). The new thiosemicarbazone was characterized by NMR and FTIR spectroscopy. All the coordination compounds were characterized by elemental analysis and FTIR spectroscopy. Also, the crystal structures of HL and complexes 1, 6, 7, and 11 were determined using single-crystal X-ray diffraction analysis. Complex 1 has a dimeric molecular structure with two bromide bridging ligands, while 6, 7, and 11 are ionic compounds and comprise monomeric complex cations. The studied complexes manifest antibacterial and antifungal activities and also have an antiradical activity that, in many cases, surpasses the activity of trolox, which is used as a standard antioxidant in medicine. Copper complexes 1-3 have very weak antiradical properties (IC50 > 100 µM), but nickel complexes 4-5 are strong antiradicals with IC50 values lower than that of trolox. The mixed ligand copper complexes with additional ligand of N-heteroaromatic base are superior to complexes without these additional ligands. They are 1.4-5 times more active than trolox.

C3-Alkylation of Imidazo[1,2-a]pyridines via Three-Component Aza-Friedel-Crafts Reaction Catalyzed by Y(OTf)3

As an important class of nitrogen-containing fused heterocyclic compounds, imidazo[1,2-a]pyridines often exhibit significant biological activities, such as analgesic, anticancer, antiosteoporosis, anxiolytic, etc. Using Y(OTf)3 as a Lewis acid catalyst, a simple and efficient method has been developed for the synthesis of C3-alkylated imidazo[1,2-a]pyridines through the three-component aza-Friedel-Crafts reaction of imidazo[1,2-a]pyridines, aldehydes, and amines in the normal air atmosphere without the protection of inert gas and special requirements for anhydrous and anaerobic conditions. A series of imidazo[1,2-a]pyridine derivatives were obtained with moderate to good yields, and their structures were confirmed by 1H NMR, 13C NMR, and HRMS. Furthermore, this conversion has the advantages of simple operation, excellent functional group tolerance, high atomic economy, broad substrate scope, and can achieve gram-level reactions. Notably, this methodology may be conveniently applied to the further design and rapid synthesis of potential biologically active imidazo[1,2-a]pyridines with multifunctional groups.

Organocatalytic Desymmetric Double Aza-Michael Addition Cascade: Enantioselective Synthesis of Fused Morpholines

Double aza-Michael addition (DAM) has become an emerging strategy for the construction of two carbon-nitrogen bonds in a single step, which can significantly simplify the synthesis of N-heterocycles. Hitherto, their asymmetric catalytic genre remains unattempted. Herein, we describe the judicious design of an organocatalytic enantioselective desymmetric double aza-Michael addition cascade to access a series of functionalized fused morpholines with excellent yields and diastereo- and enantioselectivities. A one-pot telescopic synthesis was demonstrated for a bridged triheterocyclic compound. In addition, scale-up synthesis and various attractive postsynthetic modifications of the title products amplify the significance of the current methodology.

Palladium-Catalyzed Allylation of Endocyclic 1-Azaallyl Anions

Endocyclic 1-azaallyl anions engage allyl acetates in a palladium-catalyzed allylation followed by reduction to give unprotected 2-(hetero)aryl-3-allylpiperidines and 2-allyl-3-arylmorpholines, products not easily accessible by other means. The allyl group is then readily transformed into a variety of functional groups. Preliminary studies on the asymmetric variant of the reaction using an enantiomerically pure BI-DIME-type ligand provide the product with moderate enantioselectivity. Computational studies suggest that energy barriers of inner-sphere reductive elimination and outer-sphere nucleophilic substitution are almost the same, which makes both of them possible reaction pathways. In addition, the inner-sphere mechanism displays an enantiodiscriminating C-C bond forming step, while the outer-sphere mechanism is much less selective, which combined to give the asymmetric variant of the reaction moderate enantioselectivity.

Morpholine-modified Ru-based agents with multiple antibacterial mechanisms as metalloantibiotic candidates against Staphylococcus aureus infection

Multidrug-resistant bacteria resulting from the abuse and overuse of antibiotics have become a huge crisis in global public health security. Therefore, it is urgently needed to develop new antibacterial drugs with unique mechanisms of action. As a versatile moiety, morpholine has been widely employed to enhance the potency of numerous bioactive molecules. In this study, a series of ruthenium-based antibacterial agents modified with the morpholine moiety were designed and characterized, aiming to obtain a promising metalloantibiotic with a multitarget mechanism. Antibacterial activity screening demonstrated that the most active complex Ru(ii)-3 exhibited the strongest potency against Staphylococcus aureus (S. aureus) with an MIC value of only 0.78 μg mL-1, which is better than most clinically used antibiotics. Notably, Ru(ii)-3 not only possessed excellent bactericidal efficacy, but could also overcome bacterial resistance. Importantly, Ru(ii)-3 very efficiently removed biofilms produced by bacteria, inhibited the secretion of bacterial exotoxins, and enhanced the activity of many existing antibiotics. The results of mechanism studies confirmed that Ru(ii)-3 could destroy the bacterial membrane and induce ROS production in bacteria. Furthermore, animal infection models confirmed that Ru(ii)-3 showed significant anti-infective activity in vivo. Overall, this work demonstrated that a morpholine-modified ruthenium-based agent is a promising antibiotic candidate in tackling the crisis of drug-resistant bacteria.

Expanding Complex Morpholines Using Systematic Chemical Diversity

The morpholine heterocycle is a structural unit found in many bioactive compounds and FDA-approved drugs, but the generation of more complex C-functionalized morpholine derivatives remains considerably underexplored. Using systematic chemical diversity (SCD), a concept that guides the expansion of saturated drug-like scaffolds through regiochemical and stereochemical variation, we describe the synthesis of a collection of methyl-substituted morpholine acetic acid esters starting from enantiomerically pure amino acids and amino alcohols. In total, 24 diverse substituted morpholines were produced that vary systematically in regiochemistry and stereochemistry (relative and absolute). These diverse C-substituted morpholines can be directly applied in fragment screening or incorporated as building blocks in medicinal chemistry and library synthesis.

Identification of BACE-1 inhibitors through directed C(sp3)-H activation on 5-oxo-pyrrolidine-3-carboxylic acid derivatives

Convenient synthesis of stereochemically dense 5-oxo-pyrrolidines was obtained from succinic anyhdride and imines by combining the Castagnoli-Cushman reaction with directed Pd-catalyzed C(sp3)-H functionalization, taking advantage of the developing carboxylic group properly derivatized with 8-aminoquinoline as a directing group. These fully substituted 5-oxopyrrolidines were found to be able to inhibit BACE-1 enzyme with sub-micromolar activity, thanks to the interaction of the key aryl appendage introduced by C(sp3)-H activation within BACE-1 S2' subsite.

Iodide-umpolung catalytic system for non-traditional amide coupling from nitroalkanes and amines

An N-iodosuccinimide (NIS) catalyst was developed for use in the non-traditional synthesis of amide derivatives from nitroalkanes and amines. In contrast to traditional oxidative catalysis, this catalytic system involves reversing the polarities of two catalytic components (umpolung) by means of a hypervalent iodine reagent. A variety of functional groups were tolerated in the reaction, suggesting that they have the potential for use in other types of oxidative catalytic reactions.

Exploring new quinazolin-4(3H)-one derivatives as CDK2 inhibitors: Design, synthesis, and anticancer evaluation

In the present work, five series of new 2,3-disubstituted quinazolin-4(3H)-ones 4a-c, 5a-d, 6a-g, 7a,b, and 9a-c were designed, synthesized, and screened in vitro for their cytotoxic activity against 60 cancer cell lines by the National Cancer Institute, USA. Five candidates 4c, 6a, 6b, 6d, and 6g revealed promising cytotoxicity with significant percentage growth inhibition in the range of 81.98%-96.45% against the central nervous system (CNS) (SNB-19), melanoma (MDA-MB-435), and non-small cell lung cancer (HOP-62) cell lines. The in vitro cytotoxic half maximal inhibitory concentration (IC50 ) values for the most active compounds 4c, 6a, 6b, 6d, and 6g against the most sensitive cell lines were evaluated. Additionally, screening their cyclin-dependent kinase 2 (CDK2) inhibitory activity was performed. Ortho-chloro-benzylideneamino derivative 6b emerged as the most potent compound with IC50  = 0.67 µM compared to Roscovitine (IC50  = 0.64 µM). The most active candidates arrested the cell cycle at G1, S phases, or both, leading to cell death and inducing apoptosis against CNS (SNB-19), melanoma (MDA-MB-435), and non-small cell lung cancer (HOP-62) cell lines. The molecular docking study verified the resulting outcomes for the most active candidates in the CDK2-binding pocket. Finally, physicochemical, and pharmacokinetic properties deduced that compounds 4c, 6a, 6b, 6d, and 6g displayed significant drug-likeness properties. According to the obtained results, the newly targeted compounds are regarded as promising scaffolds for the continued development of novel CDK2 inhibitors.

Design, synthesis and characterization of ethyl 3-benzoyl-7-morpholinoindolizine-1-carboxylate as anti-tubercular agents: In silico screening for possible target identification

A thorough search for the development of innovative drugs to treat tuberculosis, especially considering the urgent need to address developing drug resistance, we report here a synthetic series of ethyl 3-benzoyl-7-morpholinoindolizine-1-carboxylate analogues (5a-o) as potent anti-tubercular agents. These morpholino-indolizines were synthesized by reacting 4-morpholino pyridinium salts, with various electron-deficient acetylenes to afford the ethyl 3-benzoyl-7-morpholinoindolizine-1-carboxylate analogues (5a-o). All synthesized intermediate and final compounds are characterized by spectroscopic methods such as 1H NMR, 13C NMR and HRMS and further examined for their anti-tubercular activity against the M. tuberculosis H37Rv strain (ATCC 27294-American type cell culture). All the compounds screened for anti-tubercular activity in the range of 6.25-50 μM against the H37Rv strain of Mycobacterium tuberculosis. Compound 5g showed prominent activity with MIC99 2.55 μg/mL whereas compounds 5d and 5j showed activity with MIC99 18.91 μg/mL and 25.07 μg/mL, respectively. In silico analysis of these compounds revealed drug-likeness. Additionally, the molecular target identification for Malate synthase (PDB 5CBB) is attained by computational approach. The compound 5g with a MIC99 value of 2.55 μg/mL against M. tuberculosis H37Rv emerged as the most promising anti-TB drug and in silico investigations suggest Malate synthase (5CBB) might be the compound's possible target.

Cannabidiol-Based Prodrugs: Synthesis and Bioevaluation

Cannabidiol (CBD 1) is a nonpsychotic cannabinoid-based drug approved by the U.S. FDA for treating refractory epilepsy, namely, Lennox-Gastaut and Dravet syndrome. However, its low aqueous solubility and oral bioavailability are compensated by administering high doses, and there is an increased demand for conjugates with improved properties. In this direction, the present work is focused on synthesizing CBD-based prodrugs to address the issue of poor solubility and oral bioavailability. Several CBD-based prodrugs were synthesized and studied in a battery of assays: viz, release kinetic (ex vivo), solubility (in vitro), chemical stability (in vitro), plasma stability (ex vivo), pharmacokinetics (in vivo), and efficacy studies (in vivo). Among the synthesized prodrugs, the morpholinyl CBD-based prodrugs 3a and 3aa showed good release behavior, stability, better solubility, and a plasma profile. Moreover, prodrug candidate 3aa showed better therapeutic efficacy. The present study identifies CBD-based prodrugs with improved physiochemical properties and oral exposure.

Pro-fluorescent probe with morpholine moiety and its reactivity towards selected biological oxidants

Biological oxidants participate in many processes in the human body. Their excessive production causes organelle damage, which may result in the accumulation of cytotoxic mediators and cell degradation and may manifest itself in various diseases. Peroxynitrite (ONOO- ), hypochlorous acid (HOCl), hydrogen peroxide (H2 O2 ), and peroxymonocarbonate (HOOCO2 - ) are important oxidants in biology, toxicology, and various pathologies. Derivatives of coumarin, containing an oxidant-sensitive boronate group, have been recently developed for the fluorescent detection of inflammatory oxidants. Here, we report the synthesis and characterization of 4-[2-(morpholin-4-yl)-2-oxoethyl]-2-oxo-2H-chromen-7-yl boronic acid (MpC-BA) as a fluorescent probe for the detection of oxidants, with better solubility in water, high stability and fast response time toward peroxynitrite and hypochlorous acid. The effectiveness of the MpC-BA probe for the detection of peroxynitrite was measured by adding bolus ONOO- or using the co-generating superoxide and nitrogen oxide system. MpC-BA is oxidized by ONOO- to 7-hydroxy-4-[2-(morpholin-4-yl)-2-oxoethyl]-2H-chromen-2-one (MpC-OH). However, peroxynitrite-specific product (MpC-H) is formed in the minor reaction pathway. MpC-OH is also yielded in the reaction of MpC-BA with HOCl, and the subsequent formation of a chlorinated MpC-OH gives a specific product for HOCl (MpC-OHCl). H2 O2 slowly oxidizes MpC-BA. However, the addition of NaHCO3 increased the MpC-OH formation rate. We conclude that MpC-BA is potentially an improved fluorescent probe detecting peroxynitrite and hypochlorite in biological settings. Complementation of the fluorescence measurements by HPLC-based identification of chlorinated and reduced coumarin(s) will help identify the oxidants detected.

Discovery of imidazo[1,2-b]pyridazine-containing TAK1 kinase inhibitors with excellent activities against multiple myeloma

Current treatment options for patients with multiple myeloma (MM) include proteasome inhibitors, anti-CD38 antibodies, and immunomodulatory agents. However, if patients have continued disease progression after administration of these treatments, there are limited options. There is a need for effective targeted therapies of MM. Recent studies have shown that the transforming growth factor-β activated kinase (TAK1) is upregulated and overexpressed in MM. We have discovered that 6-substituted morpholine or piperazine imidazo[1,2-b]pyridazines, with an appropriate aryl substituent at position-3, inhibit TAK1 at nanomolar concentrations. The lead compound, 26, inhibits the enzymatic activity of TAK1 with an IC50 of 55 nM. Under similar conditions, the known TAK1 inhibitor, takinib, inhibits the kinase with an IC50 of 187 nM. Compound 26 and analogs thereof inhibit the growth of multiple myeloma cell lines MPC-11 and H929 with GI50 values as low as 30 nM. These compounds have the potential to be translated into anti-MM therapeutics.

Identification of a Selective FLT3 Inhibitor with Low Activity against VEGFR, FGFR, PDGFR, c-KIT, and RET Anti-Targets

FLT3 is mainly expressed in immune and various cancer cells and is a drug target for acute myeloid leukemia (AML). Recently, FLT3 has also been identified as a potential target for treating chronic pain. Most FLT3 inhibitors (FLT3i) identified to date, including approved drugs such as gilteritinib, midostaurin, ponatinib, quizartinib, and FLT3i in clinical trials, such as quizartinib and crenolanib, also inhibit closely-related kinases that are important for immune (c-KIT), cardiovascular (KDR/VEGFR2, FGFR, PDGFR) or kidney (RET) functions. While the aforementioned FLT3i may increase survival rates in AML, they are neither ideal for AML maintenance therapy nor for non-oncology applications, such as for the treatment of chronic pain, due to their promiscuous inhibition of many kinase anti-targets. Here, we report the identification of new FLT3i compounds that have low activities against kinases that have traditionally been difficult to differentiate from FLT3 inhibition, such as KDR/VEGFR, FGFR, PGFR, c-KIT, and RET. These selective compounds could be valuable chemical probes for studying FLT3 biology in the context of chronic pain and/or may represent good starting points to develop well-tolerated FLT3 therapeutics for non-oncology indications or for maintenance therapy for AML.

Unraveling the Conformational Preference of Morpholine: Insights from Infrared Resonant Vacuum Ultraviolet Photoionization Mass Spectroscopy

The preference for different conformations in morpholine has a notable effect on its behavior and reactivity in organic synthesis. Herein, we explored the intricate conformational properties of morpholines through a combination of advanced mass spectrometric techniques and theoretical calculations. Notably, we employed infrared (IR) resonant vacuum ultraviolet (VUV) mass-analyzed threshold ionization spectroscopy to measure the unique vibrational spectra of the distinct conformers (Chair-Eq and Chair-Ax) in morpholine for the first time. Through precise VUV photon energy adjustments to coincide with the vibrational excitation via IR absorption, we effectively pinpointed the adiabatic ionization thresholds corresponding to the Chair-Eq (65 442 ± 4 cm-1) and Chair-Ax (65 333 ± 4 cm-1) conformers. This allowed us to accurately determine the conformational stability between the two conformers (109 ± 4 cm-1). By shedding light on the conformational properties of morpholine, this study brings far-reaching implications to the fields of organic synthesis and pharmaceutical research.

Heterocyclic Merging of Stereochemically Diverse Chiral Piperazines and Morpholines with Indazoles

We report a heterocyclic merging approach to construct novel indazolo-piperazines and indazolo-morpholines. Starting from chiral diamines and amino alcohols, novel regiochemically (1,3 and 1,4) and stereochemically diverse (relative and absolute) cohorts of indazolo-piperazines and indazolo-morpholines were obtained within six or seven steps. The key transformations involved are a Smiles rearrangement to generate the indazole core structure and a late-stage Michael addition to build the piperazine and morpholine heterocycles. We further explored additional vector diversity by incorporating substitutions on the indazole aromatic ring, generating a total of 20 unique, enantiomerically pure heterocyclic scaffolds.

Syntheses of 2- and 3-Substituted Morpholine Congeners via Ring Opening of 2-Tosyl-1,2-Oxazetidine

Diastereoselective and diastereoconvergent syntheses of 2- and 3-substituted morpholine congeners are reported. Starting from tosyl-oxazatedine 1 and α-formyl carboxylates 2, base catalysis is utilized to yield morpholine hemiaminals. Their further synthetic elaborations allowed the concise constructions of conformationally rigid morpholines. The observed diastereoselectivities and the unusual diastereoconvergence in the photoredox radical processes seem to be the direct consequence of the avoidance of pseudo A^1,3 strain between the C-3 substituent and the N-tosyl group and the anomeric effect of oxygen atoms.

Development of Yin-Yang ligand for cannabinoid receptors

Cannabinoid receptors (CBs), including CB1 and CB2, are the key components of a lipid signaling endocannabinoid system (ECS). Development of synthetic cannabinoids has been attractive to modulate ECS functions. CB1 and CB2 are structurally closely related subtypes but with distinct functions. While most efforts focus on the development of selective ligands for single subtype to circumvent the undesired off-target effect, Yin-Yang ligands with opposite pharmacological activities simultaneously on two subtypes, offer unique therapeutic potential. Herein we report the development of a new Yin-Yang ligand which functions as an antagonist for CB1 and concurrently an agonist for CB2. We found that in the pyrazole-cored scaffold, the arm of N1-phenyl group could be a switch, modification of which yielded various ligands with distinct activities. As such, the ortho-morpholine substitution exerted the desired Yin-Yang bifunctionality which, based on the docking study and molecular dynamic simulation, was proposed to be resulted from the hydrogen bonding with S173 and S285 in CB1 and CB2, respectively. Our results demonstrated the feasibility of structure guided ligand evolution for challenging Yin-Yang ligand.

Rhodium-catalyzed diastereoselective synthesis of highly substituted morpholines from nitrogen-tethered allenols

Rhodium-catalyzed intramolecular cyclization of nitrogen-tethered allenols was investigated for the synthesis of functionalized morpholines. By using this strategy, various N-protected 2,5- and 2,6-disubstituted as well as 2,3,5- and 2,5,6-trisubstituted morpholines were obtained via an atom-economic pathway with high to excellent yields, diastereo- and enantioselectivities (up to 99% yield, up to >99 : 1 dr and up to >99.9 ee). The utilities of the synthesized morpholines in ozonolysis, hydration, metathesis and epoxidation reactions were also investigated.

Gold(i)-catalyzed cycloisomerization of alcohol or amine tethered-vinylidenecyclopropanes providing access to morpholine, piperazine or oxazepane derivatives: a carbene versus non-carbene process

A gold(i)-catalyzed adjustable intramolecular cyclization of alcohol or amine tethered-vinylidenecyclopropanes (VDCPs).

Novel Chromone-Containing Allylmorpholines Induce Anxiolytic-like and Sedative Effects in Adult Zebrafish

Chromone-containing allylmorpholines (CCAMs) are a novel class of compounds that have demonstrated acetyl- and butyryl-cholinesterase-inhibiting and N-methyl-D-aspartate (NMDA) receptor-blocking properties in vitro, but their in vivo pharmacological activity remains underexplored. In this work, we evaluated the psychotropic activity of five different CCAMs (1 (9a), 2 (9j), 3 (9l), 4 (33a), and 5 (33b)) using the novel tank test (NTT) and light/dark box (LDB) test in adult zebrafish. The CCAMs were screened in the NTT at a range of concentrations, and they were found to induce a dose-dependent sedative effect. Compound 4 (33a) was also evaluated using the LDB test, and it was found to have anxiolytic-like properties at low concentrations. To assess the potential contribution of the glutamate and cholinergic mechanisms in the effects of the CCAMs, we conducted experiments with pre-exposure to putative antagonists, NMDA and biperiden. Neither biperiden nor NMDA were able to diminish or cancel the effects of the CCAMs, countering the in vitro data obtained in previous studies. The apparent discrepancy could be related to the specifics of CCAM metabolism or to the interspecies differences between the putative target proteins, possibly due to the relatively low identity percentage of their sequences. Although further research in mammals is required in order to establish their pharmacological properties, novel CCAMs may represent an appealing group of psychoactive drug candidates.

Total Sesquiterpenoids of Loquat Leaves Alleviated High-Fat Diet-Induced Obesity by Targeting Fecal Metabolic Profiling and Gut Microbiota Composition

In the present study, we demonstrated that whether the gut microbiota and related metabolites contribute to the therapeutic effect of total sesquiterpenoids (TSs) from loquat leaves on obesity. A 4-week high fat diet was used to induce obesity which was then treated with TSs for another 4 weeks. TSs remarkedly reduced the weight of body and white adipose and the levels of total cholesterol (TC) and triglyceride (TG) in serum. We also found that TSs restored the diversity and richness of gut microbiota. In addition, TSs administration affected the relative abundance of seven key genera. Meanwhile, TSs were determined to affect the metabolism of the host through detecting the metabolites in feces. By applying KEGG and the correlation analysis with gut microbiota, 10 differential metabolites were identified to be the key. The results in this work proved that TSs inhibited obesity by remodeling gut microbiota and related metabolites.

2-Oxa-5-azabicyclo[2.2.1]heptane as a Platform for Functional Diversity: Synthesis of Backbone-Constrained γ-Amino Acid Analogues

We communicate a versatile synthetic approach to C-3 disubstituted 2-oxa-5-azabicyclo[2.2.1]heptanes as carbon-atom bridged morpholines, starting with 4R-hydroxy-l-proline as a chiron. Attaching an acetic acid moiety on the C-3 carbon of the 2-oxa-5-azabicyclo[2.2.1]heptane core reveals the framework of an embedded γ-amino butyric acid (GABA). Variations in the nature of the substituent on the tertiary C-3 atom with different alkyls or aryls led to backbone-constrained analogues of the U.S. Food and Drug Administration-approved drugs baclofen and pregabalin.

Modular synthesis of 2,4-diaminoanilines as CNS drug-like non-covalent inhibitors of asparagine endopeptidase

Asparagine endopeptidase (AEP), also called legumain, is a pH-dependent endolysosomal cysteine protease that cleaves its substrates after asparagine residues. Recent studies showed that it possesses δ-secretase activity and that it is implicated in numerous neurological diseases such as Alzheimer's disease (AD). Following evidence of aryl-morpholines as useful asparagine endopeptidase inhibitors, a series of morpholinoanilines with diverse substituents at ortho position were synthesized in view of improving the potency and scope of this molecular scaffold, allowing to identify ethyl 2-isonipecotate-4-morpholinoaniline possessing inhibition potency in the nanomolar range. CNS MPO (CNS MultiParameter Optimization) calculations revealed that most of the compounds developed in this work show physicochemical parameters in the desirable range for CNS drug candidates.

Electrochemical Synthesis of Substituted Morpholines via a Decarboxylative Intramolecular Etherification

An efficient method for the synthesis of 2,6-multisubstituted morpholines via an electrochemical intramolecular etherification has been developed. The method, which is operationally simple and easy to scale up, provides various substituted morpholine derivatives in high yields. The utility of this method is showcased by the synthesis of 2,2,6,6-tetrasubstituted morpholines, which are difficult to synthesize efficiently using previously reported strategies.

Synthesis and In Vitro Activity of Novel Melphalan Analogs in Hematological Malignancy Cells

Despite the continuous developments in pharmacology and the high therapeutic effect of new treatment options for patients with hematological malignancies, these diseases remain a major health issue. Our study aimed to synthesize, analyze in silico, and determine the biological properties of new melphalan derivatives. We obtained three methyl esters of melphalan having in their structures amidine moieties substituted with thiomorpholine (EM-T-MEL), indoline (EM-I-MEL), or 4-(4-morpholinyl) piperidine (EM-MORPIP-MEL). These have not yet been described in the literature. The in vitro anticancer properties of the analogs were determined against THP1, HL60, and RPMI8226 cells. Melphalan derivatives were evaluated for cytotoxicity (resazurin viability assay), genotoxicity (alkaline comet assay), and their ability to induce apoptosis (Hoechst33342/propidium iodide double staining method; phosphatidylserine translocation; and caspase 3/7, 8, and 9 activity measurements). Changes in mitochondrial membrane potential were examined using the specific fluorescence probe JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazol carbocyanine). The EM-T-MEL derivative had the highest biological activity, showing higher cytotoxic and genotoxic properties than the parent drug. Moreover, it showed a high ability to induce apoptosis in the tested cancer cells. This compound also had a beneficial effect in peripheral blood mononuclear cells (PBMC). In conclusion, we verified and confirmed the hypothesis that chemical modifications of the melphalan structure improved its anticancer properties. The conducted study allowed the selection of the compound with the highest biological activity and provided a basis for chemical structure-biological activity analyses.

Geminal Diheteroatomic Motifs: Some Applications of Acetals, Ketals, and Their Sulfur and Nitrogen Homologues in Medicinal Chemistry and Drug Design

Acetals and ketals and their nitrogen and sulfur homologues are often considered to be unconventional and potentially problematic scaffolding elements or pharmacophores for the design of orally bioavailable drugs. This opinion is largely a function of the perception that such motifs might be chemically unstable under the acidic conditions of the stomach and upper gastrointestinal tract. However, even simple acetals and ketals, including acyclic molecules, can be sufficiently robust under acidic conditions to be fashioned into orally bioavailable drugs, and these structural elements are embedded in many effective therapeutic agents. The chemical stability of molecules incorporating geminal diheteroatomic motifs can be modulated by physicochemical design principles that include the judicious deployment of proximal electron-withdrawing substituents and conformational restriction. In this Perspective, we exemplify geminal diheteroatomic motifs that have been utilized in the discovery of orally bioavailable drugs or drug candidates against the backdrop of understanding their potential for chemical lability.