Palladium-catalyzed synthesis and anti-AD biological activity evaluation of N-aryl-debenzeyldonepezil analogues

A series of novel N-aryl-debenzeyldonepezil derivatives (1-26) were designed and synthesized as cholinesterase inhibitors by the modification of anti-Alzheimer's disease drug donepezil, using Palladium catalyzed Buchwald-Hartwig cross-coupling reaction as a key chemical synthesis strategy. In vitro cholinesterase inhibition studies demonstrated that the majority of synthesized compounds exhibited high selective inhibition of AChE. Among them, analogue 13 possessing a quinoline functional group showed the most potent AChE inhibition effect and significant neuroprotective effect against H2O2-induced injury in SH-SY5Y cells. Furthermore, Compound 13 did not show significant cytotoxicity on SH-SY5Y. These results suggest that 13 is a potential multifunctional active molecule for treating Alzheimer's disease.

Targeting autophagy with small-molecule activators for potential therapeutic purposes

Autophagy is well-known to be a lysosome-mediated catabolic process for maintaining cellular and organismal homeostasis, which has been established with many links to a variety of human diseases. Compared with the therapeutic strategy for inhibiting autophagy, activating autophagy seems to be another promising therapeutic strategy in several contexts. Hitherto, mounting efforts have been made to discover potent and selective small-molecule activators of autophagy to potentially treat human diseases. Thus, in this perspective, we focus on summarizing the complicated relationships between defective autophagy and human diseases, and further discuss the updated progress of a series of small-molecule activators targeting autophagy in human diseases. Taken together, these inspiring findings would provide a clue on discovering more small-molecule activators of autophagy as targeted candidate drugs for potential therapeutic purposes.

Palladium-catalyzed synthesis and acetylcholinesterase inhibitory activity evaluation of 1-arylhuperzine A derivatives

A series of arylated huperzine A (HPA) derivatives (1-24) were efficiently synthesized in good yields (45-88% yields) through the late-stage modification of structurally complex natural anti-Alzheimer's disease (AD) drug huperzine A (HPA), using the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction. The acetylcholinesterase (AChE) inhibitory activity of all synthesized compounds was evaluated to screen the potential anti-AD bioactive molecules. The results showed that introducing the aryl groups to C-1 position of HPA resulted in the unsatisfactory AChE inhibitory activity. The present study demonstrably verifies pyridone carbonyl group could be the necessary and unchangeable pharmacophore for maintaining HPA's anti-AChE potency, and provides the helpful information on the further research for developing anti-AD HPA analogues.

Palladium-Catalyzed Synthesis, Acetylcholinesterase Inhibition, and Neuroprotective Activities of N-Aryl Galantamine Analogues

A series of new N-aryl galantamine analogues (5a-5x) were designed and synthesized by modification of galantamine, using Pd-catalyzed Buchwald-Hartwig cross-coupling reaction in good to excellent yields. The cholinesterase inhibitory and neuroprotective activities of N-aryl derivatives of galantamine were evaluated. Among the synthesized compounds, the 4-methoxylpyridine-galantamine derivative (5q) (IC₅₀ = 0.19 μM) exhibited excellent acetylcholinesterase inhibition activity, as well as significant neuroprotective effect against H₂O₂-induced injury in SH-SY5Y cells. Molecular docking, staining, and Western blotting analyses were performed to demonstrate the mechanism of action of 5q. Derivative 5q would be a promising multifunctional lead compound for the treatment of Alzheimer's disease.

Organocatalytic Asymmetric Morita-Baylis-Hillman Reaction of Isatins with Vinyl Sulfones

The organocatalytic asymmetric Morita-Baylis-Hillman (MBH) reaction of isatin derivatives with various vinyl sulfones is disclosed. Chiral sulfone-containing 3-hydroxyoxindoles were produced in good to high yields and with good to high ee's. This report displays an unprecedented example to apply activated alkenes with sulfone moiety other than carbonyl groups in asymmetric MBH reactions and provides an efficient strategy to incorporate the sulfone functional group for the synthesis of chiral 3-hydroxyoxindoles.

Visible-Light-Promoted Tandem Thiol-Ene Click Reaction/Transannular Cyclization and Regioselective Cyclopropane Ring-Opening to Construct Sulfur-Containing Euphorbia Diterpenes

The biorelevant sulfur-containing Euphorbia diterpenes with scarce 5/7/6/3 premyrsinane- and 5/7/6 myrsinane-type backbones were easily constructed from naturally abundant lathyrane-type Euphorbia factor L₃ by visible-light-triggered tandem thiol-ene click reaction/transannular cyclization and regioselective cyclopropane ring-opening. The selenide diterpene was also successfully obtained to verify the system universality. This concise synthesis route gives an efficient strategy for obtaining structurally diverse Euphorbia diterpenes under very mild conditions and provides a promising anti-HIV bioactive premyrsinane diterpene 3h.

Catalytic asymmetric total synthesis of diazabicyclooctane β-lactamase inhibitors avibactam and relebactam

Catalytic asymmetric total synthesis of avibactam and relebactam, two marketed diazabicyclooctane (DBO) β-lactamase inhibitors (BLIs), has been accomplished. An important feature of this study is the creation of a stereogenic...

Pd-Catalyzed Direct Modification of an Anti-Alzheimer's Disease Drug: Synthesis and Biological Evaluation of α-Aryl Donepezil Analogues

Palladium/BuAd₂P efficiently catalyzed the direct α-arylation of ketone in the anti-Alzheimer's disease drug donepezil, leading to 15 aryldonepezil analogues exhibiting high selective inhibition of acetylcholinesterase (AChE). The cell-based assays revealed that the 3-methylpridinyl analogue (12) shows significantly lower toxicity compared to donepezil and remarkable neuroprotective activity against H₂O₂-induced damage in SH-SY5Y cells. Docking results of compound 12 also interpreted the possible mechanism of the selective inhibition between AChE and butyrylcholinesterase (BuChE).

Pd-Catalyzed Direct Diversification of Natural Anti-Alzheimer's Disease Drug: Synthesis and Biological Evaluation of N-Aryl Huperzine A Analogues

The first systematic direct diversification of a complex natural product by metal-catalyzed N-H functionalization was carried out. A new series of N-(hetero)aryl analogues (1-32) of the natural anti-Alzheimer's disease drug huperzine A (HPA) was prepared via palladium-catalyzed Buchwald-Hartwig cross-coupling reactions of HPA with various aryl bromides in good yields. Most of the N-aryl-huperzine A (N-aryl-HPA) analogues showed good acetylcholinesterase (AChE) inhibitory activity in in vitro experiments. Three arylated huperzine A analogues (14, 19, and 30) exhibited stronger anti-AChE activity than HPA. The 5-methoxy-2-pyridyl analogue (30) displayed the most potent AChE inhibition activity, with an IC₅₀ value of 1.5 μM, which was 7.6-fold more active than HPA. Compound 30 also exhibited better neuroprotective activity for H₂O₂-induced damage in SH-SY5Y cells than HPA. Structure-activity relationship analysis suggested that the electron density of the installed aromatic ring or heteroaromatic ring played a significant role in inducing the AChE inhibition activity. Overall, compound 30 showed the advantages of easy synthesis, high potency and selectivity, and improved neuroprotection, making it a potential huperzine-type lead compound for Alzheimer's disease drug development.

Iron-Catalyzed Skeletal Conversion of Lathyrane to Premyrsinane Euphorbia Diterpenes and Their Cytotoxic Activities

Two new premyrsinane-type diterpenes (2 and 3) as diastereomers were synthesized from lathyrane-type diterpene euphorbia factor L₃ (1) for the first time via an efficient Fe(acac)₃-catalyzed skeleton conversion process. This conversion features a biogenetically inspired strategy that relies on a concise reductive olefin coupling involving intramolecular Michael addition with free radicals. The structures of 2 and 3 were elucidated by a combination of the interpretation of their spectroscopic data and single-crystal X-ray diffraction analysis. The premyrsinane diterpenes 2 and 3 exhibited cytotoxic activity against the 4T1 breast cancer cell line, while the parent compound euphorbia factor L₃ (1) was inactive. The current results not only confirmed the biogenetic relationship between lathyranes and premyrsinanes for the first time but also suggested a novel method for the preparation of naturally rare premyrsinane diterpenes with high bioactivity from the more abundant natural lathyrane diterpenes.

Isolation, Structure Elucidation, Semi-Synthesis, and Structural Modification of C19-Diterpenoid Alkaloids from Aconitum apetalum and Their Neuroprotective Activities

Five new aconitine-type C₁₉-diterpenoid alkaloids, apetalrines A-E (1-5), were isolated from Aconitum apetalum. Their structures were determined by analysis of 1D and 2D NMR, IR, and HRESIMS data. Semisynthesis of apetalrine B (2) from its parent compound aconorine was achieved to confirm the structure proposed. Twenty derivatives of 2 (11a-11l, 12a, 12b, 12d, 12e, 12j, 12k, 12m, 12n) were synthesized via a unified approach relying on simple coupling reactions. The evaluation of neuroprotective effects of compounds (1-5, 11b, 11c, 11f-11i, 12a, 12b, 12d, 12e, 12k, 12m, 12n) with low cytotoxicity revealed compound 2 to exhibit good neuroprotective effects in H₂O₂-treated SH-SY5Y cells at a concentration of 50 μM. A series of studies using flow cytometry, staining, and Western blotting on 2 indicated that its neuroprotective effects may arise from inhibiting cell apoptosis.

Late-Stage Modification of Medicine: Pd-Catalyzed Direct Synthesis and Biological Evaluation of N-Aryltacrine Derivatives

A new series of N-aryltacrine derivatives were designed and synthesized as cholinesterase inhibitors by the late-stage modification of tacrine, using the palladium-catalyzed Buchwald-Hartwig cross-coupling reaction. In vitro inhibition assay against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) demonstrated that most of the synthesized compounds had potent AChE inhibitory activity with negative inhibition of BuChE. Among them, N-(4-(trifluoromethyl)phenyl)-tacrine (3g) and N-(4-methoxypyridin-2-yl)-tacrine (3o) showed the most potent activity against AChE (IC₅₀ values of 1.77 and 1.48 μM, respectively). The anti-AChE activity of 3g and 3o was 3.5 times more than that of tacrine (IC₅₀ value of 5.16 μM). Compound 3o also displayed anti-BuChE activity with an IC₅₀ value of 19.00 μM. Cell-based assays against HepG2 and SH-SY5Y cell lines revealed that 3o had significantly lower hepatotoxicity compared to tacrine, with additional neuroprotective activity against H₂O₂-induced damage in SH-SY5Y cells. The advantages including synthetic accessibility, high potency, low toxicity, and adjunctive neuroprotective activity make compound 3o a new promising multifunctional candidate for the treatment of Alzheimer's disease.

[Experimental observation of hyperbaric oxygen combined with radioactive seed implantation in the treatment of nude mice bearing esophageal squamous cell carcinoma]

Objective: To investigate the effect and mechanism of hyperbaric oxygen combined with radioactive seed implantation in the treatment of esophageal squamous cell carcinoma. Methods: Subcutaneous tumor model of esophageal squamous cell carcinoma using TE-8 cells was established. Tumor bearing Balb/c(nu/nu) mice (60 mice) were divided into four groups, Cont group that treated with normal oxygen level, HBO group that treated with hyperbaric oxygen, RSI group that treated with radioactive seed implantation, and HBO+ RSI group that treated with hyperbaric oxygen combined with radioactive seed implantation. Tumor volume ratio and mean survival time of tumor bearing mice were observed. Pathological changes of tumor tissue after treatment were observed by hematoxylin eosin (HE) staining. Enzyme linked immunosorbent assay kit was used to detect oxidative stress. Apoptosis related proteins were detected by Western blot. Results: After treatment, the tumor volume ratio of HBO+ RSI group was 3.51±0.80 and was significantly lower than that of Cont group, HBO group, and RSI group (P<0.05). The mean survival time of HBO+ RSI group tumor bearing mice was 62 d and was significantly longer than that in Cont group, HBO group, and RSI group (P<0.05). HE staining showed that the pathological changes of tumor tissues were most obvious in HBO+ RSI group. After treatment, the MDA and Bax levels in nude mice of HBO+ RSI group were significantly higher than those in Cont group, HBO group and RSI group, but the levels of GSH, SOD and Bcl-2 were significantly lower than those of Cont group, HBO group and RSI group (P<0.05). Conclusion: Hyperbaric oxygen combined with radioactive seed implantation could slow tumor growth and increase survival time of tumor bearing mice. The possible mechanism is that hyperbaric oxygen combined with radioactive seed implantation can improve the oxidative stress response and the expression of apoptosis protein in tumor bearing nude mice.