Morpholine, Piperazine, and Piperidine Derivatives as Antidiabetic Agents.

Diabetes mellitus is a severe endocrine disease that affects more and more people every year. Modern medical chemistry sets itself the task of finding effective and safe drugs against diabetes. This review provides an overview of potential antidiabetic drugs based on three heterocyclic compounds, namely morpholine, piperazine, and piperidine. Studies have shown that compounds containing their moieties can be quite effective in vitro and in vivo for the treatment of diabetes and its consequences.

Ligand Gaussian Accelerated Molecular Dynamics 3 (LiGaMD3): Improved Calculations of Binding Thermodynamics and Kinetics of Both Small Molecules and Flexible Peptides.

Binding thermodynamics and kinetics play critical roles in drug design. However, it has proven challenging to efficiently predict ligand binding thermodynamics and kinetics of small molecules and flexible peptides using conventional molecular dynamics (cMD), due to limited simulation time scales. Based on our previously developed ligand Gaussian accelerated molecular dynamics (LiGaMD) method, we present a new approach, termed "LiGaMD3″, in which we introduce triple boosts into three individual energy terms that play important roles in small-molecule/peptide dissociation, rebinding, and system conformational changes to improve the sampling efficiency of small-molecule/peptide interactions with target proteins. To validate the performance of LiGaMD3, MDM2 bound by a small molecule (Nutlin 3) and two highly flexible peptides (PMI and P53) were chosen as the model systems. LiGaMD3 could efficiently capture repetitive small-molecule/peptide dissociation and binding events within 2 µs simulations. The predicted binding kinetic constant rates and free energies from LiGaMD3 were in agreement with the available experimental values and previous simulation results. Therefore, LiGaMD3 provides a more general and efficient approach to capture dissociation and binding of both small-molecule ligands and flexible peptides, allowing for accurate prediction of their binding thermodynamics and kinetics.

Novel phenylpiperazine derivatives as potent transient receptor potential vanilloid 1 antagonists.

Transient receptor potential vanilloid 1 (TRPV1) is a non-selective cation channel, which is considered a highly validated target for pain perception. Repeated activation with agonists to desensitize receptors or use the antagonists can both exert analgesic effects. In this work, two series of novel phenylpiperazine derivatives were designed, synthesized, and evaluated for the in vitro receptor inhibitory activity and in vivo analgesic activity. Among them, L-21 containing sulfonylurea group was identified with potent TRPV1 antagonistic activity and analgesic activity in various pain models. At the same time, L-21 exhibited low risk of hyperthermia side effect. These results indicated that L-21 is a promising candidate for further development of novel TRPV1 antagonist to treat pain.

Development of heterocyclic-based frameworks as potential scaffold of 5-HT1A receptor agonist and future perspectives: A review.

As a subtype of the 5-hydroxytryptamine (5-HT) receptor, 5-HT1A receptors are involved in the pathological process of psychiatric disorders and is an important target for antidepressants. The research groups focus on these area have tried to design novel compounds to alleviate depression by targeting 5-HT1A receptor. The heterocyclic structures is an important scaffold to enhance the antidepressant activity of ligands, including piperazine, piperidine, benzothiazole, and pyrrolidone. The current review highlights the function and significance of nitrogen-based heterocyclics 5-HT1AR represented by piperazine, piperidine, benzothiazole, and pyrrolidone in the development of antidepressant.

The medicinal chemistry of piperazines: A review.

The versatile basic structure of piperazine allows for the development and production of newer bioactive molecules that can be used to treat a wide range of diseases. Piperazine derivatives are unique and can easily be modified for the desired pharmacological activity. The two opposing nitrogen atoms in a six-membered piperazine ring offer a large polar surface area, relative structural rigidity, and more acceptors and donors of hydrogen bonds. These properties frequently result in greater water solubility, oral bioavailability, and ADME characteristics, as well as improved target affinity and specificity. Various synthetic protocols have been reported for piperazine and its derivatives. In this review, we focused on recently published synthetic protocols for the synthesis of the piperazine and its derivatives. The structure-activity relationship concerning different biological activities of various piperazine-containing drugs has also been highlighted to provide a good understanding to researchers for future research on piperazines.

Novel aurone-derived piperazine sulfonamides: Development and mechanisms of action as immunostimulants against plant bacterial diseases.

Bacterial diseases pose a significant threat to the sustainable production of crops. Given the unsatisfactory performance and poor eco-compatibility of conventional bactericides, here we present a series of newly structured bactericides that are inspiringly designed by aurone found in plants of the Asteraceae family. These aurone-derived compounds contain piperazine sulfonamide motifs and have shown promising in vitro performance against Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicola and Xanthomonas axonopodis pv. citri, in particular, compound II23 achieved minimum half-maximal effective concentrations of 1.06, 0.89, and 1.78 µg/mL, respectively. In vivo experiments conducted in a greenhouse environment further revealed that II23 offers substantial protective and curative effects ranging between 68.93 and 70.29% for rice bacterial leaf streak and 53.17-64.43% for citrus bacterial canker, which stands in activity compared with lead compound aurone and commercial thiodiazole copper. Additional physiological and biochemical analyses, coupled with transcriptomics, have verified that II23 enhances defense enzyme activities and chlorophyll levels in rice. Significantly, it also stimulates the accumulation of abscisic acid (ABA) and upregulates the expression of key genes OsPYL/RCAR5, OsBIPP2C1, and OsABF1, thereby activating the ABA signaling pathway in rice plants under biological stress from bacterial infections.

Discovery of an Azabicyclo[2.1.1]hexane Piperazinium Salt and Its Application in Medicinal Chemistry via a Rearrangement.

Herein we report the discovery of an azabicyclo[2.1.1]hexane piperazinium methanesulfonate salt from an unexpected rearrangement reaction in the preparation of ligand-directed degraders (LDDs). This bench-stable compound was found to be a versatile electrophile in a ring-opening reaction with various types of nucleophiles. Its utility as a versatile medicinal chemistry building block is further demonstrated in the synthesis of an LDD compound targeting degradation of the androgen receptor.

Synthesis, design, and optimization of a potent and selective series of pyridylpiperazines as promising antimalarial agents.

An optimization of the pyridylpiperazine series against Plasmodium falciparum has been performed, exploring a structure-activity relationship carried out on the toluyl fragment of hit 1, a compound with low micromolar activity against Plasmodium falciparum discovered by high-throughput screening. After confirming the crucial role played by this aryl fragment in the antiplasmodial activity, the replacement of the ortho-methyl substituent of 1 by halogenated ones led to an improvement for four analogs, either in terms of potency, expected pharmacokinetics profile, or both. Further introduction of endocyclic nitrogens in this fragment identified two more optimized compounds, 20 and 23, which are expected to be much more metabolically stable than 1. Additional assessment of the cytotoxicity, Ligand Lipophilic Efficiency, potency against the chloroquine-resistant Dd2 strain and in silico ADMET predictions revealed a satisfactory profile for most compounds, ultimately identifying the four optimized compounds 7, 9, 20 and 23 as promising compounds for further lead optimization of this series against Plasmodium falciparum.

Systemic delivery of bictegravir and tenofovir alafenamide using dissolving microneedles for HIV preexposure prophylaxis.

Human immunodeficiency virus (HIV) continues to pose a serious threat to global health. Oral preexposure prophylaxis (PrEP), considered highly effective for HIV prevention, is the utilisation of antiretroviral (ARV) drugs before HIV exposure in high-risk uninfected individuals. However, ARV drugs are associated with poor patient compliance and pill fatigue due to their daily oral dosing. Therefore, an alternative strategy for drug delivery is required. In this work, two dissolving microneedle patches (MNs) containing either bictegravir (BIC) or tenofovir alafenamide (TAF) solid drug nanoparticles (SDNs) were developed for systemic delivery of a novel ARV regimen for potential HIV prevention. According to ex vivo skin deposition studies, approximately 11% and 50% of BIC and TAF was delivered using dissolving MNs, respectively. Pharmacokinetic studies in Sprague Dawley rats demonstrated that BIC MNs achieved a long-acting release profile, maintaining the relative plasma concentration above the 95% inhibitory concentration (IC95) for 3 weeks. For TAF MNs, a rapid release of drug and metabolism of TAF into TFV were obtained from the plasma samples. This work has shown that the proposed transdermal drug delivery platform could be potentially used as an alternative method to systemically deliver ARV drugs for HIV PrEP.

Synthesis and biological evaluation of multimodal monoaminergic arylpiperazine derivatives with potential antidepressant profile.

Depression is a common psychiatric disorder with an estimated global prevalence of 4.4 %. Here, we designed a series of new multimodal monoaminergic arylpiperazine derivatives using a pharmacophore hybrid approach and synthesized them for the treatment of depression. Molecular docking was employed to elucidate the differences in activity and selectivity of the corresponding compounds on SERT, NET, and DAT. In vitro experiments demonstrated that compound A3 has a relatively balanced multi-target activity profile with SERT reuptake inhibition (IC50 = 12 nM), NET reuptake inhibition (IC50 = 78 nM), DAT reuptake inhibition (IC50 = 135 nM), and 5-HT1AR agonism (EC50 = 34 nM). Pharmacokinetic experiments revealed that A3 exhibited excellent bioavailability and low clearance in mice. Subsequent behavioral experiments further confirmed its significant antidepressant effects. These results further highlight the rationality of our design strategy.

Fluorescent octahydrophenazines as novel inhibitors against herpes simplex viruses.

A new series of racemic fluorescent octahydrophenazines (rac-PZ1-11) have been designed and synthesized via the efficient nucleophilic aromatic substitution (SNAr) of tetrafluorobenzenedinitriles (1a-c) and racemic cyclohexane-1,2-diamines (rac-2a and b). The bioactivities of these racemic rac-PZs (20 µM) against herpes simplex virus type-1 (HSV-1) were evaluated by the relative cell viability of Vero cells infected with HSV-1. It was found that rac-PZ3 shows much higher anti-HSV-1 activity than others, with EC50 = 9.2 ± 1.4 µM. Further investigation into the anti-HSV activities of rac-PZ3 and its enantiomers RR- and SS-PZ3 indicates that rac-PZ3 can also efficiently inhibit HSV-2 and even ACV-resistant HSV-2 (EC50 = 11.0 ± 2.3 and 14.9 ± 2.8 µM, respectively), SS-PZ3 has better activities against HSV-1, HSV-2 and ACV-resistant HSV-2 (EC50 = 4.1 ± 1.1, 5.8 ± 1.0 and 7.9 ± 1.2 µM, respectively), but RR-PZ3 has almost no antiviral activities. The primary mechanism study indicates that rac-PZ3 efficiently reverses the HSV-1/2-induced cytopathic effect and suppresses the expression of viral mRNA and proteins. In addition, rac-, RR- and SS-PZ3 possess excellent fluorescence properties with almost the same emission wavelength and high fluorescence quantum yields (ΦF = 90.3-92.3 % in cyclohexane solutions and 54.4-57.3 % in solids) and can target endoplasmic reticulum and cell membrane. The efficient anti-HSV bioactivities and excellent fluorescence of PZ3 prove its potential applications in antiviral therapy and biological imaging.

UPLC-Q-TOF-MS/MS-Based Targeted Discovery of Chetomin Analogues from Chaetomium cochliodes.

Chetocochliodin M (5) containing a rare cage-ring and chetocochliodin N (6) featuring an unusual piperazine-2,3-dione ring system together with known analogues chetomin (1), chetoseminudin C (2), chetocochliodin I (3), and oidioperazine E (4) were targeted for purification from the fungus Chaetomium cochliodes using a UPLC-Q-TOF-MS/MS approach. The structures of the new compounds were elucidated using HR-ESI-MS, NMR, and ECD spectra. Compounds 1, 3, and 6 exhibited strong cytotoxic activities against A549 and HeLa cancer cell lines.

A new chemical derivatization reagent sulfonyl piperazinyl for the quantification of fatty acids using LC-MS/MS.

In our previous study, a chemical derivatization reagent named 5-(dimethylamino) naphthalene-1-sulfonyl piperazine (Dns-PP) was developed to enhance the chromatographic retention and the mass spectrometric response of free fatty acids (FFAs) in reversed-phase liquid chromatography coupled with electrospray ionization-mass spectrometry (RPLC-ESI-MS). However, Dns-PP exhibited strong preferences for long-chain FFAs, with limited improvement for short- or medium-chain FFAs. In this study, a new series of labeling reagents targeting FFAs were designed, synthesized, and evaluated. Among these reagents, Tmt-PP (N2, N2, N4, N4-tetramethyl-6-(4-(piperazin-1-ylsulfonyl) phenyl)-1,3,5-triazine-2,4-diamine) exhibited the best MS response and was selected for further evaluations. We compared Tmt-PP with Dns-PP and four commonly used carboxyl labeling reagents from existing studies, demonstrating the advantages of Tmt-PP. Further comparisons between Tmt-PP and Dns-PP in measuring FFAs from biological samples revealed that Tmt-PP labeling enhanced the MS response for about 80 % (30/38) of the measured FFAs, particularly for short- and medium-chain FFAs. Moreover, Tmt-PP labeling significantly improved the chromatographic retention of short-chain FFAs. To ensure accurate quantification, we developed a stable isotope-labeled Tmt-PP (i.e., d12-Tmt-PP) to react with chemical standards and serve as one-to-one internal standards (IS). The method was validated for accuracy, precision, sensitivity, linearity, stability, extraction efficiency, as well as matrix effect. Overall, this study introduced a new chemical derivatization reagent Tmt-PP (d12-Tmt-PP), providing a sensitive and accurate option for quantifying FFAs in biological samples.

Exploring Structural Requirements for Sigma-1 Receptor Linear Ligands: Experimental and Computational Approaches.

Sigma-1 receptor (S1R) is involved in a large array of biological functions due to its ability to interact with various proteins and ion channels. Crystal structures of human S1R revealed the trimeric organization for which each protomer comprises the ligand binding pocket. This study applied a multistep computational procedure to develop a pharmacophore model obtained from molecular dynamics simulations of available cocrystal structures of well-known S1R ligands. Apart from the well-established positive ionizable and hydrophobic features, the obtained model included an additional specific hydrophobic feature and different excluded volumes, thus increasing the selectivity of the model as well as a more detailed determination of the distance between two essential features. The obtained pharmacophore model passed the validation test by receiver operating characteristic (ROC) curve analysis of active and inactive S1R ligands. Finally, the pharmacophoric performance was experimentally investigated through the synthesis and binding assay of new 4-phenylpiperazine-based compounds. The most active new ligand 2-(3-methyl-1-piperidyl)-1-(4-phenylpiperazin-1-yl)ethanone (3) showed an S1R affinity close to the reference compound haloperidol (Ki values of 4.8 and 2.6 nM, respectively). The proposed pharmacophore model can represent a useful tool to design and discover new potent S1R ligands.

Discovery of novel 1,8-naphthalimide piperazinamide based benzenesulfonamides derivatives as potent carbonic anhydrase IX inhibitors and ferroptosis inducers for the treatment of triple-negative breast cancer.

A novel series of 1,8-naphthalimide piperazinamide based benzenesulfonamides derivatives were designed and synthesized as carbonic anhydrase IX (CA IX) inhibitors and ferroptosis inducers for the treatment of triple-negative breast cancer (TNBC). The representative compound 9o exhibited more potent inhibitory activity and selective against CA IX over off-target CA II, compared with positive control SLC-0111. Molecular docking study was also performed to gain insights into the binding interactions of 9o in the binding pocket of CAIX. Moreover, compound 9o exhibited superior antitumor activities against breast cancer cells under hypoxia than that of normoxia conditions. Mechanism studies revealed that compound 9o could act as DNA intercalator and effectively suppressed cell migration, arrested the cell cycle at G1/S phase and induced apoptosis in MDA-MB-231 cells, while inducing ferroptosis accompanied by the dissipation of MMP and the elevation intracellular levels of ROS. Notably, in vivo studies demonstrated that 9o effectively inhibited tumor growth and metastasis in a highly metastatic murine breast cancer 4 T1 xenograft model. Taken together, this study suggests that compound 9o represents a potent and selective CA IX inhibitor and ferroptosis inducer for the treatment of TNBC.

Exploring the structural activity relationship of the Osimertinib: A covalent inhibitor of double mutant EGFRL858R/T790M tyrosine kinase for the treatment of Non-Small Cell Lung Cancer (NSCLC).

The USFDA granted regular approval to Osimertinib (AZD9291) on March 2017, for treating individuals with metastatic Non-Small Cell Lung Cancer having EGFR T790M mutation. Clinically, Osimertinib stands at the forefront for the treatment of patients with Non-Small Cell Lung Cancer. Osimertinib forms a covalent bond with the Cys797 residue and predominantly spares binding to WT-EGFR, thereby reducing toxicity and enabling the administration of doses that effectively inhibit T790M. However, a high percentage of patients treated with Osimertinib (AZD9291) developed a tertiary cysteine797 to serine797 (C797S) mutation in the EGFR kinase domain, rendering resistance to it. This comprehensive review sheds light on the chemistry, computational aspects, structural features, and expansive spectrum of biological activities of Osimertinib and its analogues. The in-depth exploration of these facets serves as a valuable resource for medicinal chemists, empowering them to design better Osimertinib analogues. This exhaustive study not only provides insights into improving potency but also emphasizes considerations for mutant selectivity and optimizing pharmacokinetic properties. This review acts as a guiding beacon for the strategic design and development of next-generation Osimertinib analogues.

Investigation into the genotoxic impurity, 1-methyl-4-nitrosopiperazine, in rifampicin.

This study assessed the presence of the genotoxic impurity 1-methyl-4-nitrosopiperazine (MNP) in 27 batches of rifampicin capsules obtained from 11 manufacturers in China. While they were below the temporary limit of 5 ppm set by the US Food and Drug Administration, the observed levels (0.33-2.36 ppm) exceeded the acceptable threshold of 0.16 ppm. Building upon preliminary findings and degradation experiments, we concluded that MNP is a by-product of the oxidative degradation of rifampicin or is introduced via oxidation or nitrosation during the synthesis process involving 1-methyl-4-aminopiperazine. The pathways of MNP formation were confirmed in this study. Furthermore, we observed that the addition of antioxidants, sealed storage, and selection of dominant crystal forms can aid in controlling MNP levels.

Explorations of Agonist Selectivity for the α9* nAChR with Novel Substituted Carbamoyl/Amido/Heteroaryl Dialkylpiperazinium Salts and Their Therapeutic Implications in Pain and Inflammation.

There is an urgent need for nonopioid treatments for chronic and neuropathic pain to provide effective alternatives amid the escalating opioid crisis. This study introduces novel compounds targeting the α9 nicotinic acetylcholine receptor (nAChR) subunit, which is crucial for pain regulation, inflammation, and inner ear functions. Specifically, it identifies novel substituted carbamoyl/amido/heteroaryl dialkylpiperazinium iodides as potent agonists selective for human α9 and α9α10 over α7 nAChRs, particularly compounds 3f, 3h, and 3j. Compound 3h (GAT2711) demonstrated a 230 nM potency as a full agonist at α9 nAChRs, being 340-fold selective over α7. Compound 3c was 10-fold selective for α9α10 over α9 nAChR. Compounds 2, 3f, and 3h inhibited ATP-induced interleukin-1ß release in THP-1 cells. The analgesic activity of 3h was fully retained in α7 knockout mice, suggesting that analgesic effects were potentially mediated through α9* nAChRs. Our findings provide a blueprint for developing α9*-specific therapeutics for pain.

Variable temperature-nuclear magnetic resonance experiment and high-resolution MS/MSn measurement of hydroxycarbodenafil, and its PDE5 inhibitory activity.

Hydroxycarbodenafil, an analogue of carbodenafil, was detected in a dietary supplement in China in 2020. However, previous reports have not identified some carbon signals from the piperazine ring in nuclear magnetic resonance (NMR) experiments. Because the compound contains an amide bond, the reaction was suggested to be characteristic of compounds with rotational isomers. Variable-temperature NMR is used to determine the rotational barrier between different conformations by changing the measurement temperature. Using this technique, we succeeded in obtaining the first distinct data, including the carbon signals of the piperazine ring in the NMR spectrum of hydroxycarbodenafil. We also confirmed that this technique could be applied to other carbodenafil analogues. Multi-stage mass spectrometry (MSn) measurements with a high-resolution mass spectrometer specific to the substructures were performed to develop a protocol for the structural determination of the carbodenafil analogues. In addition, hydroxycarbodenafil was analysed using X-ray crystallography, and its inhibitory activity against phosphodiesterase type 5 (PDE5) was measured. The IC50 value of the inhibitory activity of hydroxycarbodenafil for PDE5A1, a PDE5 isoform, of 2.9 nM was lower than the 4.5 nM for sildenafil, a positive control.

Searching for Synthetic Opioid Rescue Agents: Identification of a Potent Opioid Agonist with Reduced Respiratory Depression.

While in the process of designing more effective synthetic opioid rescue agents, we serendipitously identified a new chemotype of potent synthetic opioid. Here, we report that conformational constraint of a piperazine ring converts a mu opioid receptor (MOR) antagonist into a potent MOR agonist. The prototype of the series, which we have termed atoxifent (2), possesses potent in vitro agonist activity. In mice, atoxifent displayed long-lasting antinociception that was reversible with naltrexone. Repeated dosing of atoxifent produced antinociceptive tolerance and a level of withdrawal like that of fentanyl. In rats, while atoxifent produced complete loss of locomotor activity like fentanyl, it failed to produce deep respiratory depression associated with fentanyl-induced lethality. Assessment of brain biodistribution demonstrated ample distribution of atoxifent into the brain with a Tmax of approximately 0.25 h. These results indicate enhanced safety for atoxifent-like molecules compared to fentanyl.