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Neuroinflammation mediated by microglia is widely recognized as a key pathophysiological mechanism in neurodegenerative diseases. Lappaconitine (LA) is a natural C 18 -diterpenoid alkaloid isolated from Aconitum sinomontanum Nakai, and previous study showed that LA and its derivatives inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 cells. However, the anti-neuroinflammatory effects of LA and its derivatives on microglia are still not clear. Here, LA analogues were designed and synthesized, and the anti-neuroinflammatory activity of the synthesized compounds was screened using LPS-induced overexpression of NO in BV-2 microglia. The screening results showed that compound 10 displayed the highest ability to inhibit NO production (IC 50  = 9.98 ± 1.6 µM). Mechanistic investigations revealed that compound 10 attenuated LPS-activated neuroinflammation through suppression of TLR4/MyD88/NF-κB pathway in BV-2 microglia. Acute toxicity assays showed that compound 10 (LD 50  = 508.1 mg/kg) was safer relative to LA (LD 50  = 30.6 mg/kg). Collectively, our findings show that compound 10 could have potential as anti-neuroinflammatory agents., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Alleviating pain is crucial for patients with various diseases. This study aimed to enhance the analgesic properties of lappaconitine, a natural drug, through structural modifications. Specifically, carbamate analgesic active fragments were innovatively introduced at multiple sites on the benzene ring of lappaconitine. A total of 53 lappaconitine analogs were synthesized and evaluated. Compounds 5a, 5c, 5e, 6, and 15j addressed the narrow therapeutic window of lappaconitine, enhancing drug safety. Notably, carbamate analogs exhibited significantly enhanced analgesic activity, with compounds 5a and 5c having ED 50 values of 1.2 and 1.6 mg/kg, respectively, indicating higher potency than lappaconitine (3.5 mg/kg). A metabolic analysis of compound 5e was conducted in mice, revealing its primary metabolic processes and metabolites, and providing preliminary exploration for the druggability. Given the multiple analgesic targets of lappaconitine, its analgesic mechanism remains inconclusive. This study, for the first time, analyzed the pharmacological activity characteristics of the lappaconitine analogs using a pharmacophore model and established a three-dimensional quantitative structure-activity relationship (3D-QSAR) to elucidate the quantitative relationship between the structures of the synthesized compounds and their analgesic activities. These findings provide valuable guidance for future structural modification and optimization of analgesic drugs., (© 2024 Deutsche Pharmazeutische Gesellschaft.)

Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, have long interested scientists due to their medicinal uses and infamous toxicity which has limited the clinical application of the native compound. Alkaloid lappaconitine extracted from various Aconitum and Delphinium species has displayed extensive bioactivities and active ongoing research to reduce its adverse effects. A convenient route to construct hybrid molecules containing diterpenoid alkaloid lappaconitine and 3 H -1,5-benzodiazepine fragments was proposed. The key stage involved the formation of 5'-alkynone-lappaconitines in situ by acyl Sonogashira coupling of 5'-ethynyllappaconitine, followed by cyclocondensation with o -phenylenediamine. New hybrid compounds showed low toxicity and outstanding analgesic activity in experimental pain models, which depended on the nature of the substituent in the benzodiazepine nucleus. An analogous dependence was also shown for the antiarrhythmic activity in the epinephrine arrhythmia test in vivo. Studies on the isolated atrium have shown that the mechanism of action of the new compounds is included the blockade of beta-adrenergic receptors and potassium channels. Molecular docking analysis was conducted to determine the binding potential of target molecules with the voltage-gated sodium channel NaV1.5. All obtained results provide a basis for future rational modifications of lappaconitine, reducing side effects, while retaining its therapeutic effects.

Analogues of methyllycaconitine (MLA) based on a (3-ethyl-9-methylidene-3-azabicyclo[3.3.1]nonan-1-yl)methanol template have been designed and synthesised that incorporate the modified ester sidechains distinct from that present in the natural product. Electrophysiology experiments using Xenopus oocytes expressing nicotinic acetylcholine receptors (nAChRs) revealed selected analogues served as non-competitive inhibitors that showed selectivity for the α4β2 over α7 nAChR subtypes, and selectivity for the (α4) 3 (β2) 2 over (α4) 2 (β2) 3 stoichiometry. This study more clearly defines the biological effects of MLA analogues and identifies strategies for the development of MLA analogues as selective ligands for the α4β2 nAChR subtype., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The molecular chaperone heat shock protein 90 (Hsp90) is a promising target for cancer therapy. Natural product aconitine is a potential Hsp90 inhibitor reported in our previous work. In this study, we designed and synthesized a series of 2-((1-phenyl-1H-1,2,3-triazol-4-yl)methyl)-2-azabicyclo[3.2.1]octan-3-one derivatives as potent Hsp90 inhibitors by simplifying and modifying aconitine scaffold. Among these compounds, 14t exhibited an excellent antiproliferative activity against LoVo cells with an IC 50 value of 0.02 μM and a significant Hsp90α inhibitory activity with an IC 50 value of 0.71 nM. Molecular docking studies provided a rational binding model of 14t in complex with Hsp90α. The following cell cycle and apoptosis assays revealed that compound 14t could arrest cell cycle at G1/S phase and induce cell apoptosis via up-regulation of bax and cleaved-caspase 3 protein expressions while inhibiting the expressions of bcl-2. Moreover, 14t could inhibit cell migration in LoVo and SW620 cell lines. Consistent with in vitro results, 14t significantly repressed tumor growth in the SW620 xenograft mouse model., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Talatisamine (1) is a member of the C 19 -diterpenoid alkaloid family, and exhibits K + channel inhibitory and antiarrhythmic activities. The formidable synthetic challenge that 1 presents is due to its highly oxidized and intricately fused hexacyclic 6/7/5/6/6/5-membered-ring structure (ABCDEF-ring) with 12 contiguous stereocenters. Here we report an efficient synthetic route to 1 by the assembly of two structurally simple fragments, chiral 6/6-membered AE-ring 7 and aromatic 6-membered D-ring 6. AE-ring 7 was constructed from 2-cyclohexenone (8) through fusing an N-ethylpiperidine ring by a double Mannich reaction. After coupling 6 with 7, an oxidative dearomatization/Diels-Alder reaction sequence generated fused pentacycle 4 b. The newly formed 6/6-membered ring system was then stereospecifically reorganized into the 7/5-membered BC-ring of 3 via a Wagner-Meerwein rearrangement. Finally, Hg(OAc) 2 induced an oxidative aza-Prins cyclization of 2, thereby forging the remaining 5-membered F-ring. The total synthesis of 1 was thus accomplished by optimizing and orchestrating 33 transformations from 8., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A copper-mediated conjugate addition of electron-rich aryl groups into a complex vinyl nitrile using arylmagnesium bromides is reported. The conjugate addition adducts were advanced toward the synthesis of designed aconitine-type analogues. The variation in oxygenation patterns on the arene coupling partner, introduced through the current conjugate addition approach, may ultimately provide insight into structure-activity relationships of the diterpenoid alkaloids.

General strategies for the chemical synthesis of organic compounds, especially of architecturally complex natural products, are not easily identified. Here we present a method to establish a strategy for such syntheses, which uses network analysis. This approach has led to the identification of a versatile synthetic intermediate that facilitated syntheses of the diterpenoid alkaloids weisaconitine D and liljestrandinine, and the core of gomandonine. We also developed a web-based graphing program that allows network analysis to be easily performed on molecules with complex frameworks. The diterpenoid alkaloids comprise some of the most architecturally complex and functional-group-dense secondary metabolites isolated. Consequently, they present a substantial challenge for chemical synthesis. The synthesis approach described here is a notable departure from other single-target-focused strategies adopted for the syntheses of related structures. Specifically, it affords not only the targeted natural products, but also intermediates and derivatives in the three families of diterpenoid alkaloids (C-18, C-19 and C-20), and so provides a unified synthetic strategy for these natural products. This work validates the utility of network analysis as a starting point for identifying strategies for the syntheses of architecturally complex secondary metabolites.

The first total synthesis of the C18-norditerpenoid aconitine alkaloid neofinaconitine and relay syntheses of neofinaconitine and 9-deoxylappaconitine from condelphine are reported. A modular, convergent synthetic approach involves initial Diels-Alder cycloaddition between two unstable components, cyclopropene 10 and cyclopentadiene 11. A second Diels-Alder reaction features the first use of an azepinone dienophile (8), with high diastereofacial selectivity achieved via rational design of siloxydiene component 36 with a sterically demanding bromine substituent. Subsequent Mannich-type N-acyliminium and radical cyclizations provide complete hexacyclic skeleton 33 of the aconitine alkaloids. Key endgame transformations include the installation of the C8-hydroxyl group via conjugate addition of water to a putative strained bridghead enone intermediate 45 and one-carbon oxidative truncation of the C4 side chain to afford racemic neofinaconitine. Complete structural confirmation was provided by a concise relay synthesis of (+)-neofinaconitine and (+)-9-deoxylappaconitine from condelphine, with X-ray crystallographic analysis of the former clarifying the NMR spectral discrepancy between neofinaconitine and delphicrispuline, which were previously assigned identical structures.

The first conversional synthesis of heteratisine has been accomplished in 14 steps and 3.2% overall yield from deltaline, mainly including deoxygenation at C-10, removal of the dioxymethylene moiety, O-demethylation, as well as Baeyer-Villiger oxidation.

A series of mono- and bifunctional acyl compounds, build from the 8-O-azeloyl-14-benzoylaconine scaffold and differing by the length of the alkyl linker chain, were synthesised and evaluated against a panel of human tumour cell lines, A-549 (lung cancer), MCF-7 (breast cancer) and HCT-15 (colon cancer). None of the mono-[O-(14-benzoylaconine-8-yl)]esters displayed in vitro activity against tumour cells (IC(50) > 60 μM). However, three bis-[O-(14-benzoylaconine-8-yl)]esters presented a noticeable in vitro cytotoxic activity, those bearing 7, 8 and 9 carbon atoms between the two aconitine moieties, with IC(50)s ranging between 4 and 28 μM. The most active, bis[O-(14-benzoylaconine-8-yl)]suberate, was then evaluated in vivo in immunodeficient mice bearing human tumour xenografts originating from MCF-7 and HCT-15 cells. For MCF-7 cells, administration of five doses every 4 days, and weekly administration of 4 doses resulted in T/C percent values of 36% (p = 0.001) and 56% (p = 0.02) on day 45, respectively. For HCT-15 cells, administration of five doses every 3 days resulted in 49% tumour regression on the 25th day (p = 0.00001)., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

The first biomimetic conversion from the aconitine-type C(19)-diterpenoid alkaloids to the corresponding alkaloids of lactone-type C(19)-diterpenoid alkaloid has been achieved. Chasmanine was used as starting material with Baeyer-Villiger oxidation as a key reaction. It was also observed that the oxygenated group at C-16 did not change the relative migration tendencies of C-13 and C-9 during the oxidation. Meantime, a novel D-ring fragmented compound was obtained during the course of the present investigation. The plausible mechanism of the formation of this compound was also proposed.

Novel 3,5-disubstituted ring E analogs of methyllycaconitine were prepared and evaluated in nicotinic acetylcholine receptor binding assays. The desired analogs were prepared through the Suzuki-Miyaura cross-coupling reaction of methyl 5-bromo-nicotinate. The Suzuki-Miyaura cross-coupling reactions of pyridines with electron withdrawing substituents have not been extensively described previously.

A series of methyllycaconitine (1a, MLA) analogs was synthesized where the (S)-2-methylsuccinimidobenzoyl group in MLA was replaced with a (R)-2-methyl, 2,2-dimethyl-, 2,3-dimethyl, 2-phenyl-, and 2-cyclohexylsuccinimidobenzoyl (1b-f) group. The analogs 1b-f were evaluated for their inhibition of [(125)I]iodo-MLA binding at rat brain alpha7 nicotinic acetylcholine receptors (nAChR). In order to determine selectivity, MLA and the analogs 1b-f were evaluated for inhibition of binding to rat brain alpha,beta nAChR using [(3)H]epibatidine. At the alpha7 nAChR, MLA showed a K(i) value of 0.87 nM, analogs 1b-e possessed K(i) values of 1.67-2.16 nM, and 1f showed a K(i) value of 26.8 nM. Surprisingly, the analog 1e containing the large phenyl substituent (K(i)=1.67 nM) possessed the highest affinity. None of the compounds possessed appreciable affinity for alpha,beta nAChRs. MLA antagonized nicotine-induced seizures with an AD(50)=2 mg/kg. None of the MLA analogs were as potent as MLA in this assay. MLA and all of the MLA analogs, with the exception of 1b, antagonized nicotine's antinociceptive effects in the tail-flick assay. Compound 1c (K(i)=1.78 nM at alpha7 nAChR) with an AD(50) value of 1.8 mg/kg was 6.7 times more potent than MLA (AD(50)=12 mg/kg) in antagonizing nicotine's antinociceptive effects but was 5-fold less potent than MLA in blocking nicotine-induced seizures. Since MLA has been reported to show neuroprotection against beta-amyloid(1-42), these new analogs which have high alpha7 nAChR affinity and good selectivity relative to alpha,beta nAChRs will be useful biological tools for studying the effects of alpha7 nAChR antagonist and neuroprotection.

[reaction: see text] A model study leading to the preparation of the AEF rings of N-deacetyllappaconitine is described. The conjugate addition to the alpha-alkyl cyclohexenone 10 proceeded with high diastereocontrol. The Mannich cyclization of 16 to 4 was accomplished by heating with Rexyn-300 and Na(2)SO(4).

The development of novel agents for the differentiation of neuronal nicotinic acetylcholine receptors (nAChRs) is important for the treatment of a variety of pathological conditions. We have prepared and evaluated a number of simpler analogues of the norditerpeniod alkaloid methyllycaconitine (MLA) in an effort to understand molecular determinants of nAChR*small molecule interactions. We have previously reported the synthesis and evaluation of a series of ring E analogues of MLA. We report here the optimization of the alpha3beta4* functional activity of this series of compounds through modification of the ester.

The synthesis of several ABE tricyclic analogues of the alkaloid methyllycaconitine 1 is reported. The analogues contain two key pharmacophores: a homocholine motif formed from a tertiary N-ethyl amine in a 3-azabicyclo[3.3.1]nonane ring system and a 2-(3-methyl-2,5-dioxopyrrolidin-1-ly)benzoate ester 4. The synthesis of the ABE tricyclic analogues of MLA 1 began with selective allylation at C-3 of 3 to produce allyl beta-keto ester 4. Double Mannich reaction of 4 with ethylamine and formaldehyde produced bicyclic amine 5 The C-9 ketone of bicyclic amine 5 was selectively reduced to form bicyclic alcohols 6 and 7 which were subsequently allylated to form dienes 8 and 9. Ring closing metathesis of dienes 8 and 9 afforded tricyclic ethers 11 and 12, respectively, the C-8 ester of which was reduced to a hydroxymethyl group to form ABE tricyclic analogues 13 and 14. Addition of allylmagnesium bromide to the C-9 ketone of 20 afforded dienes 21 and 22, which underwent ring closing metathesis to form tricyclic esters 23 and 24, respectively. Reduction of the C-8 ethyl ester of 23 and 24 to a hydroxymethyl group afforded diols 25 and 26 respectively. The 2-(3-methyl-2,5-dioxopyrrolin-1-ly)benzoate ester was introduced by conversion of alcohols 13, 14, 25 and 26, to the anthranilate esters 16, 17, 27 and 28 using N-(trifluoroacetyl)anthranilic acid 15 followed by fusion with methylsuccinic anhydride to afford the substituted anthranilates 18, 19, 29 and 30 containing the key 2-(3-methyl-2,5-dioxopyrrolidin-1-ly)benzoate ester pharmacophore.

The four diastereomers 4a-d of methyllycaconitine (MLA) analogue 3 ( R =(CH(2))(3)Ph, R'=CH(3)) have been synthesized in enantiomerically pure form by coupling both (S)- and (R)-2-(methylsuccinimido)benzoic acid (5a and 5b) with both (S)- and (R)-3-hydroxymethyl-N-(3-phenyl) propylpiperidine (6a and 6b) using TBTU. These compounds were assayed for potency as nicotinic acetylcholine receptor (nAChRs) antagonist. All the four diastereomers showed the same potency at both the alpha3 and alpha7 receptors as racemic compound 3. This indicates that the binding at nicotine acetylcholine receptors (nAchRs) is probably non-stereospecific.

We have prepared ring E analogs of the diterpenoid alkaloid methyllycaconitine. These compounds have been assayed for nicotinic activity and were found to act as functional antagonists on adrenal nicotinic receptors.

A series of bicyclic analogues incorporating the homocholine motif of methyllycaconitine has been prepared to test the hypothesis that this is the essential pharmacophore of this potent, selective nicotinic receptor antagonist. A double Mannich reaction has been employed to construct the 3-azabicyclo[3.3.1]-nonane ring system, containing an N-ethylpiperidine moiety. The neopentyl-like alcohol was then esterified, using isatoic anhydride under basic conditions, to afford the corresponding anthranilate.

Methyllycaconitine (MLA) is a competitive antagonist of nicotinic acetylcholine receptors, with a remarkable preference for neuronal [125I]alpha Bgt binding sites. We have begun to investigate the structural basis of its potency and subtype selectivity. MLA is a substituted norditerpenoid alkaloid linked to a 2-(methylsuccinimido)benzoyl moiety. Hydrolysis of the ester bond in MLA to produce lycoctonine diminished affinity for rat brain [125I]alpha Bgt binding sites 2500-fold and abolished affinity for [3H]nicotine and muscle [125I]alpha Bgt binding sites. The voltage-gated Na+ channel activator aconitine, also a norditerpenoid alkaloid, but with significant structural differences from lycoctonine, displayed comparable weak or absent nicotinic activity. Addition of a 2-(methylsuccinimido)benzoyl sidechain to O-demethylated aconitine, to mimic MLA, abolished Na+ channel activation and conferred nanomolar affinity for brain [125I]alpha Bgt binding sites, comparable to that of MLA. We propose that the ester-linked 2-(methylsuccinimido)benzoyl group is necessary for nicotinic potency, but alpha 7 selectivity resides in the norditerpenoid core of the molecule.

The role of the substituents at C3 and C8 of jesaconitine (1) on jesaconitine-induced analgesia and toxicity was examined. 3-O-Acetyljesaconitine (2), 3-O-anisoyljesaconitine (3), and 3-deoxyjesaconitine (6) showed dose-dependent analgesic action, and the potency of their compound-induced analgesia and toxicity was lower than those of 1. The most remarkable difference was found in the toxicity. The results indicate that the C3 hydroxy function of 1 participate in the induction of toxicity rather than of analgesia. 8-O-Linoleoyl-14-anisoylaconine (5), 8-O-methyl-14-anisoylaconine (7), 8-O-ethyl-14-anisoylaconine (8), 14-anisoylaconine (4) and 8-deoxy-14-anisoylaconine (9) showed lower activities than jesaconitine-induced analgesia and toxicity. The analgesic activity of 7 was almost the same as that of 8, but the toxicity of 7 was lower than that of 8. The analgesic activity of 9 was lower than that of 4, but the toxicities of both derivatives were not apparent. These facts indicate that the C8 function of 1 is important to the induction of analgesia and toxicity, and also that this function participates differently in the induction of the analgesia and toxicity. Subsequently, it was suggested that substituents at C3 and C8 of 1 played important roles of the induction of the analgesia and toxicity, and that the modes of this participation were not the same in analgesia and toxicity.