Palladium-Catalyzed Arylation of Endocyclic 1-Azaallyl Anions: Concise Synthesis of Unprotected Enantioenriched cis-2,3-Diarylpiperidines

Unprotected cis-2,3-diarylpiperidines are synthesized through an unprecedented palladium-catalyzed cross-coupling reaction between aryl halides and elusive endocyclic 1-azaallyl anions. These intermediates are generated in situ by the deprotonation of 2-aryl-1-piperideines, precursors that are readily prepared in two operations from simple piperidines. An asymmetric version of this reaction with (2R, 3R)-iPr-BI-DIME as the ligand provides products in moderate to good yields and enantioselectivities. This study significantly expands the synthetic utility of endocyclic 1-azaallyl anions.

Gene regulation by morpholines and piperidines in the cardiac embryonic stem cell test

The cardiac embryonic stem cell test (ESTc) is an in vitro embryotoxicity screen which uses cardiomyocyte formation as the main differentiation route. Studies are ongoing into whether an improved specification of the biological domain can broaden the applicability of the test, e.g. to discriminate between structurally similar chemicals by measuring expression of dedicated gene transcript biomarkers. We explored this with two chemical classes: morpholines (tridemorph; fenpropimorph) and piperidines (fenpropidin; spiroxamine). These compounds cause embryotoxicity in rat such as cleft palate. This malformation can be linked to interference with retinoic acid balance, neural crest (NC) cell migration, or cholesterol biosynthesis. Also neural differentiation within the ESTc was explored in relation to these compounds. Gene transcript expression of related biomarkers were measured at low and high concentrations on differentiation day 4 (DD4) and DD10. All compounds showed stimulating effects on the cholesterol biosynthesis related marker Msmo1 after 24 h exposure and tridemorph showed inhibition of Cyp26a1 which codes for one of the enzymes that metabolises retinoic acid. A longer exposure duration enhanced expression levels for differentiation markers for cardiomyocytes (Nkx2-5; Myh6) and neural cells (Tubb3) on DD10. This readout gave additional mechanistic insight which enabled previously unavailable in vitro discrimination between the compounds, showing the practical utility of specifying the biological domain of the ESTc.

Characterization of Queen Supergene Pheromone in the Red Imported Fire Ant Using Worker Discrimination Assays

Ants use chemical signals to communicate for various purposes related to colony function. Social organization in the red imported fire ant, Solenopsis invicta, is determined by the Sb supergene, with colonies of the monogyne (single-queen) form lacking the element and colonies of the polygyne (multiple-queen) form possessing it. Polygyne workers accept new reproductive queens in their nest, but only those carrying Sb; young winged queens lacking this genetic element are executed as they mature sexually in their natal nest or as they attempt to enter a foreign nest to initiate reproduction after mating and shedding their wings. It has been suggested that queen supergene genotype status is signaled to workers by unsaturated cuticular hydrocarbons, while queen reproductive status is signaled by piperidines (venom alkaloids). We used high-throughput behavioral assays to study worker acceptance of paper dummies dosed with fractions of extracts of polygyne queens, or blends of synthetic counterparts of queen cuticular compounds. We show that the queen supergene pheromone comprises a blend of monoene and diene unsaturated hydrocarbons. Our assays also reveal that unsaturated hydrocarbons elicit discrimination by polygyne workers only when associated with additional compounds that signal queen fertility. This synergistic effect was obtained with a polar fraction of queen extracts, but not by the piperidine alkaloids, suggesting that the chemical(s) indicating queen reproductive status are compounds more polar than cuticular hydrocarbons but are not the piperidine alkaloids. Our results advance understanding of the role of chemical signaling that is central to the regulation of social organization in an important invasive pest and model ant species.

Efficacy of different dose of dexmedetomidine combined with remifentanil in colonoscopy: a randomized controlled trial

Background

Dexmedetomidine has advantages during colonoscopy as it allows the patient to cooperate during the procedure. Few studies examined the dexmedetomidine-remifentanil combination. This study was to evaluate the effects of different doses of the dexmedetomidine-remifentanil combination in colonoscopy.

Methods

This was a prospective trial carried out at the Fourth Hospital of Hebei Medical University between 02/2018 and 10/2018. The patients were randomized: group I (dexmedetomidine 0.2 μg·kg^− 1), group II (dexmedetomidine 0.3 μg·kg^− 1), and group III (dexmedetomidine 0.4 μg·kg^− 1), all combined with remifentanil. The primary outcomes were the patient’s body movements during the procedure and adverse events.

Results

Compared with at admission (T₀), the SBP, HR, and RR at immediately after giving DEX (T₁), at the beginning of the examination (T₂), 5 min after the beginning of the examination (T₃), 10 min after the beginning of the examination (T₄), and at the end of the examination (T₅) in the three groups were all reduced (all P < 0.05), but all were within the clinically normal range. SpO₂ remained > 98% in all patients during the examination. Compared with T₀, the BIS values of the three groups were decreased at T₁ and T₂ (all P < 0.05). There were no significant differences in BIS among the three groups (all P > 0.05). The minimum BIS value in group III was lower than in groups I and II (P < 0.05). The degree of satisfaction with the anesthesia effect was higher in groups II and III that in group I (P < 0.05). No hypotension occurred, seven patients had bradycardia, and four patients had nausea/vomiting.

Conclusions

Dexmedetomidine 0.3 μg·kg^− 1 combined with remifentanil was effective for colonoscopy and had few adverse reactions.

Chinese Clinical Trial Registry: ChiCTR2000029105, Registered 13 January 2020 - Retrospectively registered.

Synthesis and biological evaluation of novel quinoline-piperidine scaffolds as antiplasmodium agents

The parasitic disease malaria places almost half of the world's population at risk of infection and is responsible for more than 400,000 deaths each year. The first-line treatment, artemisinin combination therapies (ACT) regimen, is under threat due to emerging resistance of Plasmodium falciparum strains in e.g. the Mekong delta. Therefore, the development of new antimalarial agents is crucial in order to circumvent the growing resistance. Chloroquine, the long-established antimalarial drug, still serves as model compound for the design of new quinoline analogues, resulting in numerous new active derivatives against chloroquine-resistant P. falciparum strains over the past twenty years. In this work, a set of functionalized quinoline analogues, decorated with a modified piperidine-containing side chain, was synthesized. Both amino- and (aminomethyl)quinolines were prepared, resulting in a total of 18 novel quinoline-piperidine conjugates representing four different chemical series. Evaluation of their in vitro antiplasmodium activity against a CQ-sensitive (NF54) and a CQ-resistant (K1) strain of P. falciparum unveiled highly potent activities in the nanomolar range against both strains for five 4-aminoquinoline derivatives. Moreover, no cytotoxicity was observed for all active compounds at the maximum concentration tested. These five new aminoquinoline hit structures are therefore of considerable value for antimalarial research and have the potency to be transformed into novel antimalarial agents upon further hit-to-lead optimization studies.

Structurally simple synthetic 1, 4-disubstituted piperidines with high selectivity for resistant Plasmodium falciparum

Background

Emergence of resistance to artemisinins and some of their combinations in chemotherapy of clinical malaria has intensified the search for novel safe efficacious antimalarial molecules. Fourteen synthetic 1, 4-disubstituted piperidines with simple molecular structures were evaluated in this study.

Methods

Antiplasmodial activity were determined against cultured chloroquine-sensitive 3D7 and resistant Dd2 strains of P. falciparum by in vitro parasite growth inhibition. A primary screen was done to identify active compounds by fluorescence microscopy followed by a secondary screen to determine IC₅₀ and IC₉₀ values of active compounds by the parasite lactate dehydrogenase assay. Cytotoxicity of active compounds was assessed using the MTT/formazan assay and selectivity indices (SIs) determined. Optical densities were analysed to obtain experimental results.

Results

The compounds produced 56 to 93% inhibition of parasite growth at 40 μg/mL. Eight compounds (2 ketone, 5 alcohol and one amine analogues) showed high activity (IC₅₀s between 1 and 5 μg/mL). Nine compounds were highly selective for the parasite (SIs = 15 to 182). Three promising (alcohol) analogues were identified: [1-(4-fluorobenzyl) piperidin-4-yl] [4-fluorophenyl] methanol, (7), [1-(3, 4-dichlorobenzyl) piperidin-4-yl] [4- fluorophenyl] methanol (8) and [1-(4-bromobenzyl) piperidin-4-yl] [4- fluorophenyl] methanol (11) which were more active on the resistant strain (IC₅₀ values between 1.03 to 2.52 μg/mL), than the sensitive strain (IC₅₀ values between 2.51 to 4.43 μg/mL).

Conclusions

The alcohol analogues were the most active and most selective for the parasite with three promising hit molecules identified among them, suggesting the hydroxyl group at C-7’ in these alcohol analogues is contributing greatly to their antiplasmodial activity. Further exploration of the core structure using chemistry approaches and biological screening including in vivo studies in an animal model of malaria may yield important antimalarial leads.

[Clinical significance of σ1 receptor over-expression in cervical cancer and the effect of its synthetic ligands on the growth of cervical cancer cells]

Objective: To explore the role of σ1 receptor (σ1R) in the clinical prognosis of cervical cancer,and provide a theoretical basis for σ1R targeted molecular therapy through observing the inhibition of synthetic σ1R-specific ligand compounds on the growth of cervical cancer cells. Methods: (1) Immunohistochemical or immunocytochemistry staining were respectively used to detect the expression and localization of σ1R protein. (2) The Cancer Genome Atlas (TCGA) data set was used to validate our results. (3) Two series of 4 novel σ1R ligand compounds were synthesized by altering the N-terminal substituents on the piperidine ring of the prezamicol analogue, named as 14a, 14e, 15c and 15f. Methyl thiazolyl-tetrazolium (MTT) assay was detect the anti-proliferative effect of the four compounds on HeLa and SiHa cells. Compound 14a with potent inhibitory activity and the highest specificity of σ1R was selected for further experiments. Scratch test was observed the migration effect of compound 14a on HeLa and SiHa cells. Flow cytometry was determined cell cycles and apoptosis. Results: (1) Immunostaining of σ1R protein was located in the cytoplasm and nucleus of cervical epithelium. The expression of cervical squamous cell carcinoma (SCC) was significantly higher than those of high-grade squamous intraepithelial lesion (HSIL) or normal cervical tissues. There was no significant difference in the expression of σ1R between HSIL and normal cervical tissues. σ1R expression in cervical adenocarcinoma (AC) was higher than that in SCC (P=0.020). The nuclear expression rate of σ1R in AC (10/18) was higher than that of SCC (27.1%, 19/70; P=0.024). The median overall survival (MOS) of σ1R-positive SCC patients was lower than that of σ1R-negative patients [(45.8±3.1) vs (51.7±2.9) months, P=0.045]. MOS of the patients with σ1R nuclear positive SCC was lower than that of non-nuclear staining [(38.9±3.8) vs (48.7±2.1) months, P=0.022]. MOS of the patients with σ1R nuclear positive AC was lower than that of non-nuclear staining [(35.0±6.3) vs (44.2±4.2) months, P=0.034]. (2) Analysis of TCGA data showed that σ1R expression of in SCC was correlated with age (P=0.005). σ1R expression in AC was significantly associated with advanced stage, lymphnode metastasis and vascular invasion (all P<0.05). MOS of AC patients with σ1R overexpression was significantly lower than that of the patients with low expression (P=0.034). There was no significant difference in the MOS of different expression of σ1R mRNA in SCC patients(P=0.930). (3) MTT assay showed that these four compounds could suppressed the growth of HeLa and SiHa cells in time- and dose-dependent manner. The growth inhibition rates of HeLa and SiHa cells at 48 hours treated by combination of different concentrations of nedaplatin (NDP) with compound 14a (6 μmol/L) were significantly higher than those treated by NDP alone. Compound 14a (30 μmol/L) significantly inhibited the migration (both P<0.01) and induced the apoptosis of HeLa or SiHa cells (both P<0.01). Conclusions: σ1R is over-expressed in cervical cancer and HSIL. σ1R nuclear expression is an important marker of AC. σ1R over-expression, especially σ1R nuclear expression is associated with the poor prognosis of cervical cancer. Our study is mostly consistent with cervical cancer data of TCGA. These results suggest that the novel synthetic prezamicol analogues 14a for σ1R could inhibit the growth of cervical cancer cells and cell migration through inducing apoptosis and arresting cell cycle in G(0)/G(1) period, enhance NDP-induced cytotoxicity.

Monoamine oxidase and transaminase screening: biotransformation of 2-methyl-6-alkylpiperidines by Neopestalotiopsis sp. CBMAI 2030

High-throughput screening detected transaminases (TAs) and monoamine oxidases (MAOs) in fungi by applying a fluorogenic probe. Strains F026, F037, F041, F053, and F057 showed the highest enzymatic conversions (31, 60, 30, 40, and 32%, respectively) and where evaluated for their ability to transform piperidines. Strain F053 (Neopestalotiopsis sp. CBMAI 2030) revealed unusual enzymatic activity to deracemize 2-methyl-6-alkylpiperidines. Neopestalotiopsis sp. CBMAI 2030 was capable to convert 2-methyl-6-propylpiperidine, 2-methyl-6-butylpiperidine, and 2-methyl-6-pentylpiperidine in piperideine with 11, 14, and 24% conversion, respectively. The activity was enhanced by cultivating the fungus with 2-methyl-6-pentylpiperidine (38% conversion and 73% ee).

In vitro modulatory effects of functionalized pyrimidines and piperidine derivatives on Aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR) activities

The development of biologically active molecules based on molecular recognition is an attractive and challenging task in medicinal chemistry and the molecules that can activate/deactivate certain receptors are of great medical interest. In this contribution, selected pyrimidine/piperidine derivatives were synthesized and tested for the ability to activate/deactivate Aryl hydrocarbon receptor (AhR) and Glucocorticoid receptor (GR). Tested compounds are shown to activate the receptors but to much lesser extent than positive controls, dioxin and dexamethasone for Ahr and GR, respectively. However, some of them antagonized the positive controls action. Although further in vivo studies are needed to fully characterize the bioactivities of these compounds, the reported in vitro evidences demonstrate that they might be used as the modulators of AhR and GR activities.

4-aroylpiperidines and 4-(α-hydroxyphenyl)piperidines as selective sigma-1 receptor ligands: synthesis, preliminary pharmacological evaluation and computational studies

Background

Sigma (σ) receptors are membrane-bound proteins characterised by an unusual promiscuous ability to bind a wide variety of drugs and their high affinity for typical neuroleptic drugs, such as haloperidol, and their potential as alternative targets for antipsychotic agents. Sigma receptors display diverse biological activities and represent potential fruitful targets for therapeutic development in combating many human diseases. Therefore, they present an interesting avenue for further exploration. It was our goal to evaluate the potential of ring opened spipethiane (1) analogues as functional ligands (agonists) for σ receptors by chemical modification.

Results

Chemical modification of the core structure of the lead compound, (1), by replacement of the sulphur atom with a carbonyl group, hydroxyl group and 3-bromobenzylamine with the simultaneous presence of 4-fluorobenzoyl replacing the spirofusion afforded novel potent sigma-1 receptor ligands 7a–f, 8a–f and 9d–e. The sigma-1 receptor affinities of 7e, 8a and 8f were slightly lower than that of 1 and their selectivities for this receptor two to threefold greater than that of 1.

Conclusions

It was found that these compounds have higher selectivities for sigma-1 receptors compared to 1. Quantitatitive structure–activity relationship studies revealed that sigma-1 binding is driven by hydrophobic interactions.Graphical abstract

Potent P2Y1 urea antagonists bearing various cyclic amine scaffolds

A number of new amine scaffolds with good inhibitory activity in the ADP-induced platelet aggregation assay have been found to be potent antagonists of the P2Y1 receptor. SAR optimization led to the identification of isoindoline 3c and piperidine 4a which showed good in vitro binding and functional activities, as well as improved aqueous solubility. Among them, the piperidine 4a showed the best overall profile with favorable PK parameters.