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Natural products (NPs) often act as sources of CNS-active agents and provide inspiration for the development of synthetic molecules that incorporate their best features. Vindeburnol (VIND; (±)-(3α,14β)-20,21-dinoreburnamenin-14-ol; developmental codes RU24722 or BC19), based on the core structure of eburnamine-vincamine alkaloids, has been extensively investigated for its biological activities. This molecule has demonstrated potential therapeutic properties in various in vivo models of CNS disorders such as multiple sclerosis, Alzheimer's disease, and depressive-like behavior. Although few clinical trials were conducted, further development of vindeburnol was abandoned. This review presents synthetic approaches to vindeburnol synthesis as well as the most complete discussion of its pharmacological effects. Studies involving vindeburnol in animal models of CNS disorders and a few human trials have been presented in separate sections. Special attention is placed on derivatives and analogs based on the vindeburnol scaffold. The interesting pharmacological profile of vindeburnol suggests that this NP-inspired compound may serve as a useful tool or structural basis for next-generation molecules in CNS drug design and discovery., 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 Elsevier Masson SAS. All rights reserved.)

Treating methicillin-resistant Staphylococcus aureus (MRSA) infection remains one of the most difficult challenges in clinical practice, primarily due to the resistance of MRSA to multiple antibiotics. Therefore, there is an urgent need to develop novel antibiotics with high efficacy and low cross-resistance rates. In this study, a series of novel pleuromutilin derivatives with coumarin structures were synthesized and subsequently assessed for their biological activities. Most of these derivatives showed potent antimicrobial activity against drug-resistant Gram-positive bacterial strains. Compound 14b displayed particularly rapid bactericidal effects, slow resistance development, and low cytotoxicity. Moreover, it decreased bacterial loads in the lung, liver, kidney, spleen, and heart and exhibited better antibacterial efficacy (ED 50 = 11.16 mg/kg) than tiamulin (ED 50 = 28.93 mg/kg) in a mouse model of systemic MRSA infection. Both in vitro and in vivo analyses suggest that compound 14b is a promising agent for the treatment of MRSA infections.

Idiopathic pulmonary fibrosis (IPF) is a progressive respiratory disease with no known cause. It is characterized by widespread inflammation and structural abnormalities in the alveoli of the lungs, ultimately leading to the development of pulmonary fibrosis. Triptolide (TP), an epoxy-diterpene lactone compound known for its potent anti-inflammatory and antifibrotic effects, was limited clinical use due to poor water solubility and side effects. Two soluble TP prodrugs (PG490-88 and Minnelide) have entered clinical research. However, their activities are based on enzyme metabolism, which is influenced by species-specific differences. In this study, we present water-soluble TP derivatives synthesized by introducing ethylenediamine carbamate groups (TP-DEAs) at the 14-hydroxy position. The introduced groups were found to spontaneously convert into the parent drug through enzyme-independent metabolic conversion. The water solubility and stability of the compounds were examined in vitro. Notably, TP-DEA2 exhibited high water solubility (30.8 mg/mL), exceeding TP solubility by more than 1181-fold. In vitro, TP-DEA2 converted to TP autonomously without the involvement of enzymes. In addition, TP-DEA2 can inhibit the expression of a disintegrin and metalloproteinase 10 (ADAM 10) induced by TGF-β1 and reduce the secretion of a-SMA in fibroblasts. In vivo, TP-DEA2 transformed into TP, effectively inhibiting fibrosis in the bleomycin group without observed toxicity. Importantly, positive outcomes when administering TP-DEA2 at a later stage post-bleomycin exposure suggest its potential role in treating IPF., 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 Elsevier Masson SAS. All rights reserved.)

In this study, four franchetine-type diterpenoid alkaloids (1-4) were isolated from Aconitum sinoaxillare, and fourteen diverse franchetine analogs (5-18) were synthesized. Compounds 1, 2, 7 and 16 exhibited stronger inhibitory effects on NO production when compared to celecoxib. Among them, compound 1 had the best inhibitory effect on iNOS and COX-2 inflammatory proteins. The in vitro studies displayed that the anti-inflammatory effect of the most active compound 1 was ascribed to the inhibition of the TLR4-MyD88/NF-κB/MAPKs signalling pathway. Consequently, this led to a inhibition in the expression of inflammatory factors or mediators including NO, ROS, TNF-α, IL-6, IL-1β, iNOS, and COX-2. Additionally, compound 1 had low toxicity (LD 50  > 20 mg/kg) in mice, and it had notable analgesic effects on acetic acid-induced visceral pain (ED 50  = 2.15 ± 0.07 mg/kg). Moreover, compound 1 exhibited a distinct reduction in the Na V 1.7 and Na V 1.8 channel currents during both resting and half-inactivated states at 50 μM. The present study enriches the pharmacological activities of franchetine derivatives and provides valuable insights for the development of novel anti-inflammatory and analgesic 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 Inc.)

Tumor proliferation and metastasis are intricately linked to blood vessel formation, with vascular endothelial growth factor (VEGF) playing a pivotal role in orchestrating angiogenesis throughout tumor progression. Pseudolaric acid B (PAB) has emerged as a potent inhibitor of tumor cell proliferation, migration, and angiogenesis. In efforts to enhance its efficacy, 37 derivatives of PAB were synthesized and assessed for their capacity to suppress VEGF secretion in SiHa cells under hypoxic conditions. Notably, majority of these derivatives exhibited significant inhibition of VEGF protein secretion without inducing cytotoxicity. Among them, compound M2 displayed the most potent inhibitory activity, with an IC 50 value of 0.68 μM, outperforming the lead compound PAB (IC 50  = 5.44 μM). Compound M2 not only curbed the migration and angiogenesis of HUVECs under hypoxic conditions but also hindered the invasion of SiHa cells. Mechanistic investigations unveiled that compound M2 may impede the accumulation and nuclear translocation of hypoxia-inducible factor 1α (HIF-1α) in SiHa cells, thereby downregulating VEGF expression. This inhibitory effect on HIF-1α was corroborated by experiments utilizing the protease inhibitor MG-132 and protein synthesis inhibitor CHX, indicating that compound M2 diminishes HIF-1α levels by reducing its synthesis. Furthermore, compound M2 was observed to modulate the PI3K/AKT/mTOR and MAPK signaling pathways in tumor cells, thereby regulating HIF-1α translation and synthesis. In vivo studies demonstrated that compound M2 exhibited low toxicity and effectively curbed tumor growth. Immunohistochemistry analyses validated that compound M2 effectively suppressed the expression of HIF-1α and VEGF in tumor tissues, underscoring its potential as a promising therapeutic agent for targeting tumor angiogenesis., 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 Elsevier Masson SAS. All rights reserved.)

In response to the escalating threat of microbial resistance, a series of novel pleuromutilin derivatives, conjugated with phenyl-sulfide and boron-containing moieties, were designed and synthesized. Most derivatives, especially 14b and 16b, demonstrated significant efficacy against Gram-positive bacteria, including multidrug-resistant strains, as well as pleuromutilin-resistant strains. Compound 16b showed high stability in the liver microsomes of rats and humans, along with acceptable tolerance in vitro and in vivo. Additionally, compound 16b exhibited promising efficacy in MRSA-infected mouse models. Our data highlight the potential of conjugated pleuromutilin derivatives as valuable agents against drug-resistant bacteria., 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 Masson SAS.)

By utilizing the conformational selectivity of biosynthesis and the flexibility of chemical synthesis, researchers have formulated metabolic engineering-based semi-synthetic approaches that initiate with the final product's structure and identify key biosynthesis intermediates. Nonetheless, these tailored semi-synthetic routes focused on end-products, neglecting the possibility of biobased intermediates as a platform for derivatization. To address this challenge, this studyproposed a novel strategy resembling chemosynthesis-style divergent exploration to amplify the significance of biobased intermediates, in the case of geranylgeraniol (GGOH). Using the novel bifunctional terpene synthase PTTC066 and systematic metabolic engineering modifications, the engineered yeast straindemonstrated high GGOH production levels (3.32 g/L, 0.039 g/L/h). This platformenabled the semi-synthesis of various pharmaceuticals, including the anti-ulcer drug teprenone, the osteoporosis treatment drug menaquinone-4, and introduced a novel route for synthesizingα-tocotrienol. This study offers a fresh outlook on semi-synthetic approaches, opening avenues for improvements, substitutions, and innovations in industrial production processes., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Tiangang, Liu reports financial support was provided by Wuhan Hesheng Technology Co., Ltd. Wuhan University and Wuhan Hesheng Technology Co., Ltd have applied for several patents based on this work. If there are other authors, they 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 Elsevier Ltd. All rights reserved.)

Pseudolaric Acid B (PAB), a natural product with remarkable anti-tumor activity, is a starting point for new anticancer therapeutics. We designed and synthesized 27 PAB derivatives and evaluated their anti-proliferative activities against four cancer cell lines: MCF-7, HCT-116, HepG2, and A549. Compared with unmodified PAB, the PAB derivatives showed stronger anti-proliferative activity. The ability of compound D3 (IC 50  = 0.21 μM) to inhibit HCT-116 cells was approximately 5.3 times that of PAB (IC 50  = 1.11 μM) and the antiproliferative action was unrelated to cytotoxicity (SI=20.38), indicating its superior safety profile (PAB; SI=0.95). Compound D3 effectively suppressed the EdU-positive rate and reduced colony formation, arrested HCT-116 cells in the S and G2/M phases and induced apoptosis. In vivo experiments further demonstrated low toxicity of compound D3 while suppressing tumor growth in mice. In summary, given its strong anti-proliferative effect and relative safety, further development of compound D3 is warranted., 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 Elsevier Inc. All rights reserved.)

Methicillin-resistant Staphylococcus aureus (MRSA) remains a significant global health threat, necessitating the development of new therapeutic agents. Pleuromutilin derivatives offer a promising solution due to their potent antibacterial activity, particularly against Gram-positive bacteria such as MRSA. In this study, we synthesized a series of pleuromutilin derivatives with phenol linker containing C14 side chains and evaluated in vitro and in vivo antibacterial activities. Several compounds showed potent activity against MRSA and Staphylococcus aureus with minimal inhibitory concentrations (MICs) as low as 0.03125 μg/mL. In particular, compounds a4 and b4 showed rapid bactericidal activity, significantly reducing MRSA loads in time-kill kinetics and exhibiting slower resistance development compared to tiamulin. In vivo, compound a4 showed superior efficacy in reducing MRSA-induced lung damage in a mouse model at a lower effective dose (ED50 = 6.48 mg/kg) compared to tiamulin (ED50 = 11.38 mg/kg). Molecular docking and molecular dynamics studies also showed that compound a4 binds strongly to the ribosomal peptidyl transferase center (PTC), a key target for pleuromutilin derivatives. These results suggest that compound a4, with its enhanced antibacterial activity and low resistance potential, is a promising candidate for further development as an effective treatment for MRSA infections., 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 Elsevier Masson SAS. All rights reserved.)

Geranylgeraniol (GGOH) is a crucial component in fragrances and essential oils, and a valuable precursor of vitamin E. It is primarily extracted from the oleoresin of Bixa orellana , but is challenged by long plant growth cycles, severe environmental pollution, and low extraction efficiency. Chemically synthesized GGOH typically comprises a mix of isomers, making the separation process both challenging and costly. Advancements in synthetic biology have enabled the construction of microbial cell factories for GGOH production. In this study, Yarrowia lipolytica was engineered to efficiently synthesize GGOH by expressing heterologous phosphatase genes, enhancing precursor supplies of farnesyl diphosphate, geranylgeranyl pyrophosphate, and acetyl-CoA, and downregulating the squalene synthesis pathway by promoter engineering. Additionally, optimizing fermentation conditions and reducing reactive oxygen species significantly increased the GGOH titer to 3346.47 mg/L in a shake flask. To the best of our knowledge, this is the highest reported GGOH titer in shaking flasks to date, setting a new benchmark for terpenoid production.

A novel class of pleuromutilin derivatives possessing 1,2,3-triazole as the linker connected to phenyl analogues were designed. The antibacterial properties of the prepared compounds were assessed in vitro against five strains (E. coli, S. aureus, S. epidermidis, and E. faecalis). Most of the tested compounds displayed potent antibacterial activities against gram-positive bacteria and 14-O-[2-(4-((2,4-dinitrophenoxy)-methyl-1H-1,2,3-triazol-1-yl) acetamide)-2-methylpropan-2-yl) thioacetyl]mutilin (7c) exerted antibacterial activities against S. aureus, MRSA and S. epidermidis with MIC values 0.0625 μg/mL, representing 64-fold, 4-fold and 8-fold higher than tiamulin respectively. Compound 6e, 7c and 8c were chosen to carry out killing kinetics, which exhibited concentration-dependent effect. Subsequently, molecular modeling was conducted to further explore the binding of compound 6e, 7a, 7c, 8c and tiamulin with 50S ribosomal subunit from deinococcus radiodurans. The investigation revealed that the main interactions between compound 7c and the ribosomal residues were three hydrogen bonds, π-π, and p-π conjugate effects. Additionally, the free binding energy and docking score of 7c with the ribosome demonstrated the lowest values of -11.90 kcal/mol and -7.97 kcal/mol, respectively, consistent with its superior antibacterial activities., 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 Elsevier Ltd. All rights reserved.)

Sphaerococcenol A is a cytotoxic bromoditerpene biosynthesized by the red alga Sphaerococcus coronopifolius . A series of its analogues ( 1 - 6 ) was designed and semi-synthesized using thiol-Michael additions and enone reduction, and the structures of these analogues were characterized by spectroscopic methods. Cytotoxic analyses (1-100 µM; 24 h) were accomplished on A549, DU-145, and MCF-7 cells. The six novel sphaerococcenol A analogues displayed an IC 50 range between 14.31 and 70.11 µM on A549, DU-145, and MCF-7 malignant cells. Compound 1 , resulting from the chemical addition of 4-methoxybenzenethiol, exhibited the smallest IC 50 values on the A549 (18.70 µM) and DU-145 (15.82 µM) cell lines, and compound 3 , resulting from the chemical addition of propanethiol, exhibited the smallest IC 50 value (14.31 µM) on MCF-7 cells. The highest IC 50 values were exhibited by compound 4 , suggesting that the chemical addition of benzylthiol led to a loss of cytotoxic activity. The remaining chemical modifications were not able to potentiate the cytotoxicity of the original compounds. Regarding A549 cell viability, analogue 1 exhibited a marked effect on mitochondrial function, which was accompanied by an increase in ROS levels, Caspase-3 activation, and DNA fragmentation and condensation. This study opens new avenues for research by exploring sphaerococcenol A as a scaffold for the synthesis of novel bioactive molecules.

In search for new molecules of diterpene origin with promising anticancer activity, two amino-derivatives (methyl maleopimarate aminoimide and methyl 1β,13-epoxydihydroquinopimarate C4-hydrazone) were involved in the 4-component Ugi reaction (Ugi-4CR) and pseudo-7-component azido-Ugi condensation (azido-Ugi-7CR) to afford a series of adducts holding α-aminoacylamide and bis-1,5-disubstituted tetrazole substituents. The NCI-60 cancer cell panel screening revealed diterpene-type Ugi adducts 2, 5, and 6 with strong antiproliferative potency with GI 50 in range of 1.2-15.4 μM. The high positive correlations with standard anticancer drugs suggest microtubules or progesterone and androgen receptors as possible targets of the synthesized compounds., (© 2024 John Wiley & Sons Ltd.)

Lathyrane-based diterpenoid is one of the critical bioactive elements of Euphorbia lathyris L., a widely used traditional Chinese medicine for the treatment of inflammation and infection. In this study, we introduced and evaluated seven synthetic or natural lathyrane-based diterpenoids with the same core structure but notable structural variations at specific positions, for their anti-inflammatory and gout-alleviating properties. There was no significant cytotoxicity below 10 μM among the initial test of the cell counting kit 8 of the seven candidate derivatives (compounds 13 to 19) in this work. Furthermore, maintaining the acyloxy group at 15-C position and the strongly hydrophobic aryl structure at 3-C and 5-C positions, compounds 15 (Euphorbia factor L3, EFL3) and 17 strikingly inhibited the production of IL-1β related to the actuation of the inflammasome in our study. The ELISA assay indicated that the anti-inflammatory effects of EFL3 were better associated with MSU stimulation than other second-line pathways triggered by inflammasome. Further examinations on the acute paw gout model in C57BL/6 mice showed that EFL3 had a significantly inflammatory retarding effect by intraperitoneal injection. It decreased swelling volume as well as the cleavage and activation of local IL-1β and casepas-1 in the paw. To conclude, our findings reveal several potential key structure-activity relationships that govern the anti-inflammatory effects of lathyrane-type diterpenoids, the dispensable acyl group at the 15-C position, the importance of maintaining the spatial structure of the B-ring, and the potential importance of hydrophobic substituents at the 3-C position. These insights may provide guidance for the structural design of lathyrane-type agents in the future; furthermore, we found that the lathyrane-based diterpenoid EFL3 is a potential agent for gout that is expected to provide a novel therapeutic strategy for inflammation intervention., 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 Inc.)

Fusicoccane diterpenoids display intriguing biological activities, including the ability to act as modulators of 14-3-3 protein-protein interactions. However, their innate structural complexity and diverse oxygenation patterns present enormous synthetic challenges. Here we develop a modular chemoenzymatic approach that combines de novo skeletal construction and late-stage hybrid C-H oxidations to achieve the synthesis of ten complex fusicoccanes in 8-13 steps each. A convergent fragment coupling strategy allowed rapid access to a key tricyclic intermediate, which was subjected to chemical and enzymatic C-H oxidations to modularly prepare five oxidized family members. We also conceived a complementary biomimetic skeletal remodelling strategy to synthetically access five rearranged fusicoccanes with unusual bridgehead double bonds. This work may facilitate future investigation into the biological activities of the fusicoccanes and also inspire the implementation of similar hybrid strategies to provide family-level synthetic solutions to other natural product scaffolds., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

The enmein-type diterpenoids are a class of anticancer ent -Kaurane diterpnoids that have received much attention in recent years. Herein, a novel 1,14-epoxy enmein-type diterpenoid 4 , was reported in this project for the first time. A series of novel enmein-type diterpenoid derivatives were also synthesized and tested for anticancer activities. Among all the derivatives, compound 7h exhibited the most significant inhibitory effect against A549 cells (IC 50 = 2.16 µM), being 11.03-folds better than its parental compound 4 . Additionally, 7h exhibited relatively weak anti-proliferative activity (IC 50 > 100 µM) against human normal L-02 cells, suggesting that it had excellent anti-proliferative selectivity for cancer cells. Mechanism studies suggested that 7h induced G0/G1 arrest and apoptosis in A549 cells by inhibiting the PI3K/AKT/mTOR pathway. This process was associated with elevated intracellular ROS levels and collapsed MMP. In summary, these data identified 7h as a promising lead compound that warrants further investigation of its anticancer properties.

Herein, we report concise total syntheses of diterpene natural products (-)-crinipellins A and B with a tetraquinane skeleton, three adjacent all-carbon quaternary centers, and multiple oxygenated and labile functional groups. Our synthesis features a convergent Kozikowski β-alkylation to unite two readily available building blocks with all the required carbon atoms, an intramolecular photochemical [2 + 2] cycloaddition to install three challenging and adjacent all-carbon quaternary centers and a 5-6-4-5 tetracyclic skeleton, and a controlled Cargill rearrangement to rearrange the 5-6-4-5 tetracyclic skeleton to the desired tetraquinane skeleton. These strategically enabling transformations allowed us to complete total syntheses of (-)-crinipellins A and B in 12 and 13 steps, respectively. The results of quantum chemical computations revealed that the Bronsted acid-catalyzed Cargill rearrangements likely involve stepwise paths to products and the AlR 3 -catalyzed Cargill rearrangements likely involve a concerted path with asynchronous alkyl shifting events to form the desired product.

Herein, we present a highly efficient method for constructing the intricate 5-5-6 fused ring system commonly found in the polycyclic furanobutenolide-derived cembranoid and norcembranoid natural product family with remarkable diastereoselectivity, utilizing an intramolecular Diels-Alder reaction as the cornerstone. Notably, employing a propargyl ether tether as the dienophile yields significant enhancements in the transformation process compared to its propargyl ester counterpart, as demonstrated in our previous total synthesis of havellockate. This advancement holds promising implications for future investigations, offering a streamlined pathway for rapidly assembling the tricyclic core characteristic of this diverse family of natural products.

The carbon skeleton of any organic molecule serves as the foundation for its three-dimensional structure, playing a pivotal role in determining its physical and biological properties 1 . As such, taxane diterpenes are one of the most well-known natural product families, primarily owing to the success of their most prominent compound, paclitaxel, an effective anticancer therapeutic for more than 25 years 2-6 . In contrast to classical taxanes, the bioactivity of cyclotaxanes (also referred to as complex taxanes) remains significantly underexplored. The carbon skeletons of these two groups of taxanes differ significantly, and so would typically their own distinct synthetic approaches. Here we report a versatile synthetic strategy based on the interconversion of complex molecular frameworks, providing general access to the wider taxane diterpene family. A range of classical and cyclotaxane frameworks was prepared including, among others, the total syntheses of taxinine K (2), canataxapropellane (5) and dipropellane C from a single advanced intermediate. The synthetic approach deliberately eschews biomimicry, emphasizing instead the power of stereoelectronic control in orchestrating the interconversion of polycyclic frameworks., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Polyene cyclizations are among the most complex and challenging transformations in biology. In a single reaction step, multiple carbon-carbon bonds, ring systems and stereogenic centres are constituted from simple, acyclic precursors 1-3 . Simultaneously achieving this kind of precise control over product distribution and stereochemistry poses a formidable task for chemists. In particular, the polyene cyclization of (3E,7E)-homofarnesol to the valuable naturally occurring ambergris odorant (-)-ambrox is recognized as a longstanding challenge in chemical synthesis 1,4-7 . Here we report a diastereoselective and enantioselective synthesis of (-)-ambrox and the sesquiterpene lactone natural product (+)-sclareolide by a catalytic asymmetric polyene cyclization by using a highly Brønsted-acidic and confined imidodiphosphorimidate catalyst in the presence of fluorinated alcohols. Several experiments, including deuterium-labelling studies, suggest that the reaction predominantly proceeds through a concerted pathway in line with the Stork-Eschenmoser hypothesis 8-10 . Mechanistic studies show the importance of the enzyme-like microenvironment of the imidodiphosphorimidate catalyst for attaining exceptionally high selectivities, previously thought to be achievable only in enzyme-catalysed polyene cyclizations., (© 2024. The Author(s).)

An efficient synthetic strategy for scabrolide F (7), a norcembranolide diterpene that was isolated from the Taiwanese soft coral Sinularia scabra , has only recently been reported by our group. Herein, we report details of the first total synthesis of 7. The tetrahydrofuran domain of 7 was stereoselectively constructed via the 5- endo-tet cyclization of a hydroxy vinyl epoxide. The reaction of alkyl iodide 30 with dithiane 38, followed by the introduction of an alkene moiety, afforded allylation precursor 41. The coupling of alkyl iodide 42 and allylic stannane 43 was examined as a model experiment of allylation. Because the desired allylated product 44 was not obtained, an alternative synthetic route toward 7 was investigated instead. In the second synthetic approach, fragment-coupling between alkyl iodide 56 and aldehyde 58, macrolactonization, and transannular ring-closing metathesis were used as the key steps to achieve the first total synthesis of 7. We hope that this synthetic strategy provides access to the total synthesis of other macrocyclic norcembranolides. We also evaluated the antifouling activity and toxicity of 7 and its synthetic intermediates toward the cypris larvae of the barnacle Amphibalanus amphitrite . This study is the first to report the antifouling activity of norcembranolides as well as the biological activity of 7.

Synthesis of the A/D/E-ring core compounds of maoecrystal V was achieved. The key Diels-Alder reactions between tricyclic α-methylene lactones and Kitahara-Danishefsky dienes afforded the spirocyclic core compounds in a regioselective and stereoselective manner., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

This review collects the synthetic modifications performed on andrographolide, a natural molecule derived from Andrographis paniculata , for oncology applications. Various pharmacomodulations were carried out, and the products were tested on different cancer cell lines. The impact of these modifications was analyzed with the aim of mapping the positions essential for activity to facilitate future research in this field. However, this study makes it clear that, in addition to structural modifications of the molecule, which can result in varying degrees of effectiveness in targeting interactions, the lipophilic capacity of the structures obtained through hemisynthesis is of significant importance.

In this study, we designed and synthesized a series of pleuromutilin derivatives containing thiazole. The in vitro antimicrobial efficacy of these synthesized compounds was examined by using four strains. Compared with tiamulin (MIC = 0.25 μg/mL), compound 14 exhibited potency in inhibiting MRSA growth (MIC = 0.0625 μg/mL) in these derivatives. Meanwhile, the time-killing kinetics further demonstrated that compound 14 could efficiently inhibit the MRSA growth. After exposure at 4 × MIC, the postantibiotic effect (PAE) of compound 14 was 1.29 h. Additionally, in thigh-infected mice, compound 14 exhibited a more potent antibacterial efficacy (-1.78 ± 0.28 log 10 CFU/g) in reducing MRSA load compared to tiamulin (-1.21 ± 0.23 log 10 CFU/g). Moreover, the MTT assay on RAW 264.7 cells demonstrated that compound 14 (8 μg/mL) had no significant cytotoxicity. Docking studies indicated the strong affinity of compound 14 toward the 50S ribosomal subunit, with a binding free energy of -9.63 kcal/mol. Taken together, it could be deduced that compound 14 was a promising candidate for treating MRSA infections.

Alepterolic acid is a diterpene occurring in the fern Aleuritopteris argentea with potential biological activity that warrants further structural modification. In the present work, sixteen alepterolic acid derivatives were synthesized and evaluated for their anticancer activities. Among them, N-[m-(trifluoromethoxy)phenyl] alepterolamide displayed comparable activity (IC 50 =4.20±0.21 μM) in MCF-7 cells. Moreover, mechanistic investigations indicated this compound was significantly capable of diminishing cell proliferation and viability of MCF-7 cells. After treatment with N-[m-(trifluoromethoxy)phenyl] alepterolamide, a significant increase in cleaved caspase-9, cleaved caspase-3, cleaved poly (ADP-ribose) polymerase (PARP) and Bax/Bcl2 ratio were observed in MCF-7 cells, leading to caspase-dependent apoptotic pathways. Further studies showed this compound promoted cellular apoptosis and inhibited migration in MCF-7 cells via modulation of the Akt/p70 S6K signaling pathway. All these results revealed the potential of N-[m-(trifluoromethoxy)phenyl] alepterolamide as an appealing therapeutic drug candidate for breast cancer., (© 2023 Wiley-VHCA AG, Zurich, Switzerland.)

This paper reports the design, synthesis, and antibacterial activity study of pleuromutilin derivatives with 2-methyl-4-nitroaniline and 2-methoxy-4-nitroaniline side chains at the C22 position. The structures of the new compounds were characterized by 1 H-NMR, 13 C-NMR and HRMS. The inhibitory activity of the compounds against MSSA, pyogeniccoccus, streptococcus, and MRSA strains was determined using the micro broth dilution method. The results showed that the compounds exhibited certain activity against Gram-positive bacteria, among which compounds A8a, A8b, A8c, A8d, and A7 demonstrated superior antibacterial activity against MSSA, MRSA, and pyogeniccoccus compared to tiamulin, although the derivatives showed lower antibacterial activity against streptococcus compared to the control drug. Based on the favorable in vitro activity of A8c, the time-kill kinetics against MRSA were evaluated, revealing that compound A8c could inhibit bacterial proliferation in a concentration-dependent manner., (© 2024 John Wiley & Sons Ltd.)

The first systematic acylated diversification of naturally scarce premyrsinane diterpenes, together with their biosynthetic precursors lathyrane diterpene were carried out. Two new series of premyrsinane derivates (1a-32a) and lathyrane derivates (1-32) were synthesized from the naturally abundant lathyrane diterpene Euphorbia factor L 3 through a bioinspired approach. The cholinesterase inhibitory and neuroprotective activities of these diterpenes were investigated to explore potential anti-Alzheimer's disease (AD) bioactive lead compounds. In general, the lathyrane diterpenes showed the better acetylcholinesterase (AChE) inhibitory activity than that of premyrsinanes. The lathyrane derivative 17 bearing a 3-dimethylaminobenzoyl moiety showed the best AChE inhibition effect with the IC 50 value of 7.1 μM. Molecular docking demonstrated that 17 could bond with AChE well (-8 kal/mol). On the other hand, premyrsinanes showed a better neuroprotection profile against H 2 O 2 -induced injury in SH-SY5Y cells. Among them, the premyrsinane diterpene 16a had significant neuroprotective effect with the cell viability rate of 113.5 % at 12.5 μM (the model group with 51.2 %). The immunofluorescence, western blot and reactive oxygen species (ROS) analysis were conducted to demonstrate the mechanism of 16a. Furthermore, a preliminary SAR analysis of the two categories of diterpenes was performed to provide the insights for anti-AD drug development., 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 Elsevier Inc. All rights reserved.)

Herein, we present a unified chemical synthesis of three subgroups of cephalotaxus diterpenoids. Key to the success lies in adopting a synthetic strategy that is inspired by biosynthesis but is opposite in nature. By employing selective one-carbon introduction and ring expansion operations, we have successfully converted cephalotane-type C 18 dinorditerpenoids (using cephanolide B as a starting material) into troponoid-type C 19 norditerpenoids and intact cephalotane-type C 20 diterpenoids. This synthetic approach has enabled us to synthesize cephinoid H, 13-oxo-cephinoid H, 7-oxo-cephinoid H, fortalpinoid C, 7-epi-fortalpinoid C, cephanolide E, and 13-epi-cephanolide E. Furthermore, through the development of an intermolecular asymmetric Michael reaction between β-oxo esters and β-substituted enones, we have achieved the enantioselective synthesis of advanced intermediates within our synthetic sequence, thus formally realizing the asymmetric total synthesis of the cephalotaxus diterpenoids family., (© 2024 Wiley-VCH GmbH.)

The human phosphatidylinositol 4-phosphate 5-kinase type I α (hPIP5K1α) plays a key role in the development of prostate cancer. In this work, seventeen derivatives of the natural diterpene totarol were prepared by copper(I)-catalysed Huisgen 1,3-dipolar cycloaddition reaction of the correspondingO-propargylated totarol with aryl or alkyl azides and screened for their inhibitory activities toward hPIP5K1α. Five compounds, 3a, 3e, 3f, 3i, and 3r, strongly inhibited the enzyme activity with IC 50 values of 1.44, 0.46, 1.02, 0.79, and 3.65 µM, respectively, with the most potent inhibitor 3e 13-[(1-(3-nitrophenyl)triazol-4yl)methoxy]-totara-8,11,13-triene). These compounds were evaluated on their antiproliferative effects in a panel of prostate cancer cell lines. Compound 3r inhibited the proliferation of LNCaP, PC3 and DU145 cells at 20 µM, strongly, but also has strong cytotoxic effects on all tested cells., 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 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The diterpene 7α-acetoxy-6β-hydroxyroyleanone isolated from Plectranthus grandidentatus demonstrates promising antibacterial, anti-inflammatory and anticancer properties. However, its bioactivity may be enhanced via strategic structural modifications of such natural products through semisynthesis. The anticancer potential of 7α-acetoxy-6β-hydroxyroyleanone and five derivatives was analyzed in silico via the prediction of chemicals absorption, distribution, metabolism, excretion, and toxicity (ADMET), quantum mechanical calculations, molecular docking and molecular dynamic simulation. The protein targets included regulators of apoptosis and cell proliferation. Additionally, network pharmacology was used to identify potential targets and signaling pathways. Derivatives 7α-acetoxy-6β-hydroxy-12- O -(2-fluoryl)royleanone and 7α-acetoxy-6β-(4-fluoro)benzoxy-12- O -(4-fluoro)benzoylroyleanone achieved high predicted binding affinities towards their respective protein panels, with stable molecular dynamics trajectories. Both compounds demonstrated favorable ADMET parameters and toxicity profiles. Their stability and reactivity were confirmed via geometry optimization. Network analysis revealed their involvement in cancer-related pathways. Our findings justify the inclusion of 7α-acetoxy-6β-hydroxy-12- O -(2-fluoryl)royleanone and 7α-acetoxy-6β-(4-fluoro)benzoxy-12- O -(4-fluoro)benzoylroyleanone in in vitro analyses as prospective anticancer agents. Our binding mode analysis and stability simulations indicate their potential as selective inhibitors. The data will guide studies into their structure optimization, enhancing efficacy and drug-likeness.

This study explores the synthesis of unique furanocembranoid-type marine diterpenoid, providencin. Providencin features a highly oxidized structure with two furan rings, two oxirane rings, and a bicyclo[12.2.0]hexadecane framework. Its potential as a lead compound for drug development has drawn attention to its total synthesis, particularly focusing on the challenging right-half segment involving a highly substituted cyclobutane ring. We developed a novel synthetic strategy for the fragment using a [2 + 2] cycloaddition reaction of lithium ynolates with α,β-unsaturated lactone, successfully constructing a bicyclic cyclobutene structure. Stereoselective hydrogenation of cyclobutenes was achieved by using Crabtree's catalyst under high pressure H 2 atmosphere. After further transformation, the synthesis of the furan-substituted cyclobutanol fragment having a formyl side chain was accomplished.

The asymmetric total syntheses of cephalotaxus C19 diterpenoids, bearing a unique cycloheptene A ring with a chiral methyl group at C-12, were disclosed based on a universal strategy. Six members, including cephinoid P, cephafortoid A, 14- epi -cephafortoid A and fortalpinoids M-N, P, were accomplished for the first time. The concise approach relies on two crucial steps: (1) a Nicholas/Hosomi-Sakurai cascade reaction was developed to efficiently generate the cycloheptene ring bearing a chiral methyl group; (2) an intramolecular Pauson-Khand reaction was followed to facilitate the construction of the complete skeleton of target molecules. Our studies provide a new strategy for the synthetic analysis of cephalotaxus diterpenoids and structurally related polycyclic natural products.

A series of lathyrane-type Euphorbia diterpene derivatives featured 3R configuration (H-3β) were synthesized from natural rich Euphorbia factor L 3 via modified Mitsunobu reaction based on configuration inversion strategy. The antiproliferation activity and MDR reversal ability of the lathyrane derivatives were evaluated, and the most synthesized compounds showed moderate or strong potencies. Among them, diterpenes 21 (IC 50 values of 2.6, 5.2 and 13.1 μM, respectively) and 25 (IC 50 values of 5.5, 8.6 and 1.3 μM, respectively) presented the strong cytotoxicity against MCF-7, 4 T1 and HepG2 cells. Meanwhile, derivative 25 exhibited excellent MDR reversal ability with the reversal fold of 16.1 higher than that of verapamil. The cellular thermal shift assay and molecular docking proved direct engagement of diterpene 25 to ABCB1, suggesting 25 could be a promising MDR modulator. Furthermore, the preliminary SARs of these diterpenes were also discussed., 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 © 2022 Elsevier Inc. All rights reserved.)

Three new diterpenes, stellejasmins A ( 1 ) and B ( 2 ) and 12- O -benzoylphorbol-13-heptanoate ( 3 ), were isolated from the roots of Stellera chamaejasme L. The structures of 1 - 3 were elucidated by extensive NMR and mass spectroscopic analyses. Compounds 1 and 2 are the first derivatives containing a hydroxy group at C-2 in the family of daphnane and tigliane diterpenes. The presence of a chlorine atom in 1 is unique in the plant metabolite. Compound 3 has an odd-number acyl group, which is biosynthetically notable. Human immunodeficiency virus (HIV) LTR-driven transcription activity was tested with 1 - 3 and 17 known diterpenes isolated from S. chamaejasme L. and Wikstroemia retusa A.Gray. Among these, gnidimacrin ( 4 ), stelleralide A ( 5 ), and wikstroelide A ( 20 ) were highly potent, with EC 50 values of 0.14, 0.33, and 0.39 nM, respectively. The structure-activity relationship (SAR) was investigated using 20 natural and eight synthetic diterpenes. This is the first SAR study on natural daphnane and tigliane diterpenes.

As our ongoing work on lathyrane diterpenoid derivatization, three series of lathyrane diterpenoid derivatives were designed and synthesized based combination principles, including pyrazole, thiazole and furoxan moieties. Biological evaluation indicated that compound 23d exhibited excellently inhibitory activity on LPS-induced NO production in RAW264.7 cells (IC 50  = 0.38 ± 0.18 μM). The preliminary structure-activity relationships (SARs) suggested that phenylsulfonyl substituted furoxan moiety had the strongest ability to improve anti-inflammatory activity of lathyrane diterpenoids. Furthermore, compound 23d significantly reduced the level of ROS. Its molecular mechanism was related to inhibiting the transcriptional activation of Nrf2/HO-1 pathway. Based on these considerations, 23d might be a promising anti-inflammatory agent, which is noteworthy for further exploration., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Covering: 2015 to 2020The ent -kaurane diterpenoids are integral parts of tetracyclic natural products that are widely distributed in terrestrial plants. These compounds have been found to possess interesting bioactivities, ranging from antitumor, antifungal and antibacterial to anti-inflammatory activities. Structurally, the different tetracyclic moieties of ent -kauranes can be seen as the results of intramolecular cyclizations, oxidations, C-C bond cleavages, degradation, or rearrangements, starting from their parent skeleton. During the past decade, great efforts have been made to develop novel strategies for synthesizing these natural products. The purpose of this review is to describe the recent advances in the total synthesis of ent -kaurane diterpenoids covering the period from 2015 to date.

Neurotrophic factors have been shown to potentially be beneficial for the treatment of neurodegenerative diseases such as Alzheimer's disease, because endogenous neurotrophic factors (NGF, BDNF) have been recognized to play critical roles in the promotion of neurogenesis, differentiation, and neuroprotection throughout the development of the central nervous system. However, high-molecular-weight proteins are unable to cross the blood-brain barrier and are easily decomposed under physiological conditions. Thus, small molecules that can mimic the functions of neurotrophic factors are promising alternatives for the treatment of neurodegenerative disease. Since 1990, the author has been involved in searching for natural products with typical neurotrophic properties that can cause neurogenesis, enhance neurite outgrowth, and protect against neuronal death by using three cellular systems (PC12, rat cortical neurons, and MEB5 cells). Through these research activities on neurotrophic natural products, the author has tried to induce a paradigm shift from the discipline of natural products chemistry to science disciplines. This review focuses on our independent synthetic studies of the neurotrophic natural products discovered in the plants. The following synthetic elaborations are described: syntheses of dimeric isocuparane-type sesquiterpenes mastigophorenes A and B, macrocyclic bis-bibenzyls plagiochins A-D and cavicularin through a Pd-catalyzed Stille-Kelly reaction; the formal synthesis of merrilactone A and jiadifenin, which are seco-prezizaane-type sesquiterpenes, through intramolecular Pd-catalyzed Mizoroki-Heck and Tsuji-Trost reactions; and finally the first enantioselective synthesis of neovibsanin B, a vibsane-type diterpene, through a Pd-catalyzed cyclic carbopalladation-carbonyl tandem reaction.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder, one of the main characteristics of which is the abnormal accumulation of amyloid peptide (Aβ) in the brain. Whereas β-secretase supports Aβ formation along the amyloidogenic processing of the β-amyloid precursor protein (βAPP), α-secretase counterbalances this pathway by both preventing Aβ production and triggering the release of the neuroprotective sAPPα metabolite. Therefore, stimulating α-secretase and/or inhibiting β-secretase can be considered a promising anti-AD therapeutic track. In this context, we tested andrographolide, a labdane diterpene derived from the plant Andrographis paniculata , as well as 24 synthesized derivatives, for their ability to induce sAPPα production in cultured SH-SY5Y human neuroblastoma cells. Following several rounds of screening, we identified three hits that were subjected to full characterization. Interestingly, andrographolide (8,17-olefinic) and its close derivative 14α-(5',7'-dichloro-8'-quinolyloxy)-3,19-acetonylidene (compound 9 ) behave as moderate α-secretase activators, while 14α-(2'-methyl-5',7'-dichloro-8'-quinolyloxy)-8,9-olefinic compounds 31 (3,19-acetonylidene) and 37 (3,19-diol), whose two structures are quite similar although distant from that of andrographolide and 9 , stand as β-secretase inhibitors. Importantly, these results were confirmed in human HEK293 cells and these compounds do not trigger toxicity in either cell line. Altogether, these findings may represent an encouraging starting point for the future development of andrographolide-based compounds aimed at both activating α-secretase and inhibiting β-secretase that could prove useful in our quest for the therapeutic treatment of AD.

We report the convergent total synthesis of (±)-hamigeran M, enabled by five C-H functionalization reactions and proceeding in 11 steps in 3.9% overall yield. The C-H functionalizations include a hydroxy-directed C-H borylation, one C-H metalation-1,2-addition, one C-H metalation-Negishi coupling, a late-stage oxazole-directed C-H borylation-oxidation, and one electrophilic bromination. Two of these five C-H functionalizations forged strategic C-C bonds in the seven-membered ring of hamigeran M. The oxazole-directed C-H borylation-oxidation was unprecedented and ensured a late-stage hydroxylation. Other key steps include a tandem Suzuki reaction-lactonization to join the cyclopentane building block with the aromatic moiety and a hydrogen-atom transfer reaction to reduce a challenging tetrasubstituted double bond.

Reported here are substrate-dictated rearrangements of chrysanthenol derivatives prepared from verbenone to access complex bicyclic frameworks. These rearrangements set the stage for a 10-step formal synthesis of the natural product xishacorene B. Key steps include an anionic allenol oxy-Cope rearrangement and a Suárez directed C-H functionalization. The success of this work was guided by extensive computational calculations which provided invaluable insight into the reactivity of the chrysanthenol-derived systems, especially in the key oxy-Cope rearrangement.

Antibiotics resistance is becoming increasingly common, involving almost all antibiotics on the market. Diseases caused by drug resistant bacteria, such as MRSA, have high mortality and negatively affect public health. The development of new drugs would be an effective means of solving this problem. Modifications based on bioactive natural products could greatly shorten drug development time and improve success rate. Pleuromutilin, a natural product from the basidiomycete bacterial species, is a promising antibiotic candidate. In this study, a series of novel pleuromutilin derivatives possessing piperazinyl urea linkage were efficiently synthesised, and their antibacterial activities and bactericidal properties were evaluated via MIC, MBC and Time-kill kinetics assays. The results showed that all compounds exhibited potent activities against tested strains, especially MRSA strains with MIC values as low as 0.125 μg/mL; 8 times lower than that of marketed antibiotic Tiamulin. Docking studies indicate substituted piperazinyl urea derivatives could provide hydrogen bonds and initiate π-π stacking between molecules and surrounding residues.

Novel series of pleuromutilin analogs containing substituted 1,2,3-triazole moieties were designed, synthesised and assessed for their in vitro antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA). Initially, the in vitro antibacterial activities of these derivatives against 4 strains of S. aureus (MRSA ATCC 43300, ATCC 29213, AD3, and 144) were tested by the broth dilution method. Most of the synthesised pleuromutilin analogs displayed potent activities. Among them, compounds 50 , 62 , and 64 (MIC = 0.5∼1 µg/mL) showed the most effective antibacterial activity and their anti-MRSA activity were further studied by the time-killing kinetics approach. Binding mode investigations by surface plasmon resonance (SPR) with 50S ribosome revealed that the selected compounds all showed obvious affinity for 50S ribosome (K D = 2.32 × 10 -8 ∼5.10 × 10 -5 M). Subsequently, the binding of compounds 50 and 64 to the 50S ribosome was further investigated by molecular modelling. Compound 50 had a superior docking mode with 50S ribosome, and the binding free energy of compound 50 was calculated to be -12.0 kcal/mol.

Lipidation of microtubule associated protein 1 light chain 3 (LC3) is the critical step in autophagosome formation, numerous efforts have been made to design and develop small molecules that trigger LC3 lipidation to activate autophagy. In this study, we discovered a series of andrographolide derivatives as potent antagonists of vitamin D receptor (VDR) by luciferase reporter assay. Structure-activity-relationship study revealed that andrographolide derivative ZAV-12 specifically inhibited VDR signaling but not NF-κB or STAT3 activation. Western blot analysis indicates that ZAV-12 markedly triggered lipidation of LC3 in MPP + -induced Parkinsonism in vitro in an mTOR-independent manner. The ZAV-12 triggered lipidation was mediated through SREBP2 activation instead of changing expression levels of lipid synthesis genes. Furthermore, ZAV-12 treatment increased the ratio of LC3-II/LC3-I and oligomerization of A53T α-synuclein (SNCA) in SNCA triggered neurotoxicity. Taken together, these results demonstrate the therapeutic potential of VDR antagonist as novel drug candidate for neurodegenerative diseases., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Plants consistently synthesize and accumulate medically valuable secondary metabolites which can be isolated and clinically tested under in vitro conditions. An advancement with such important phytochemical production has been recognized and utilized as herbal drugs. Bioactive andrographolide (AGL; C 20 H 30 O 5 ) isolated from Andrographis paniculate (AP) (Kalmegh) is a diterpenoid lactones having multifunctional medicinal properties including anti-manic, anti-inflammatory, liver, and lung protective. AGL is known for its immunostimulant activity against a variety of microbial infections thereby, regulating classical and alternative macrophage activation, Ag-specific antibody production during immune disorder therapy. In vitro studies with AGL found it to be effective against multiple tumors, neuronal disorders, diabetes, pneumonia, fibrosis, and other diverse therapeutic misadventures. Generally, virus-based diseases like ZIKA, influenza A virus subtype (H1NI), Ebola (EBOV), Dengue (DENV), and coronavirus (COVID-19) epidemics have greatly increased scientific interest and demands to develop more effective and economical immunomodulating drugs with minimal side effects. Trials and in vitro pharmacological studies with AGL and medicinally beneficial herbs might contribute to benefit the human population without using chemical-based synthetic drugs. In this review, we have discussed the possible role of AGL as a promising herbal-chemo remedy during human diseases, viral infections and as an immunity booster.

In the current study a late-stage diversification of unactivated olefins labd-8(17)-en-15-oic acid (1a) and methyl labd-8(17)-en-15-oate (1b) via Heck-Matsuda arylation is described. The reaction provided straightforward and practical access to a series of novel aryl-labdane-type derivatives (HM adducts 3a-h) in moderate to good yields in a highly regio- and stereoselective manner at room temperature under air atmosphere. The cytotoxic activity of these compounds was investigated in vitro against three different human cell lines (THP-1, K562, MCF-7). Of these, HM adduct 3h showed a selective effect in all cancer cell lines tested and was selected for extended biological investigations in a leukemia cell line (K562), which demonstrated that the cytotoxic/antiproliferative activity observed in this compound might be mediated by induction of cell cycle arrest at the sub-G1 phase and by autophagy-induced cell death. Taken together, these findings indicate that further investigation into the anticancer activity against chronic myeloid leukemia from aryl-labdane-type derivatives may be fruitful., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Based on the higher mitochondrial membrane potential (Δψ m ) of tumor cells than normal cells, a mitochondria-targeting strategy using delocalized lipophilic cations as carriers is a promising way to improve the antitumor effect of small molecules and to reduce toxicity. Triptolide (TP) has a strong antitumor effect but is limited in the clinic due to high systemic toxicity. Mitochondria-targeted TP derivatives were designed and synthesized using triphenylphosphine cations as carriers. The optimal derivative not only maintained the antitumor activity of TP but also showed a tumor cell selectivity trend. Moreover, the optimal derivative increased the release of lactate dehydrogenase and the production of ROS, decreased Δψ m , and arrested HepG2 cells in G0/G1 phase. In a zebrafish HepG2 xenograft tumor model, the inhibitory effect of the optimal derivative was comparable to that of TP, while it had no obvious toxic effect on multiple indicators in zebrafish at the test concentrations. This work provided some evidence to support the mitochondria-targeting strategy., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A modular strategy for meroterpenoid-type marine natural products has been developed from commercially available (+)-sclareolide using a palladium-catalyzed tandem carbene migratory insertion as one of the key steps. Its applicability is showcased by the formal synthesis of (-)-pelorol and 9- epi -pelorol and the concise total synthesis of (+)-yahazunone and (+)-yahazunol. It is worth noting that the formal synthesis of (-)-pelorol and 9- epi -pelorol was achieved by controlling the reaction sequence of hydrogenation and cyclization.

A series of pleuromutilin derivatives with 1,2,4-triazole-3-substituted Schiff base structure were designed and synthesized under mild conditions. The in vitro antibacterial activities of the synthesized derivatives against 4 strains of Staphylococcus aureus (MRSA ATCC 43300, S.aureus ATCC 29213, S.aureus 144 and S.aureus AD3) and 1 strain of E. coli (ATCC 25922) were evaluated by the broth dilution method. Among these derivatives, compound 60 exhibited superior in vitro antibacterial effect against MRSA (MIC = 0.25 μg/mL) than tiamulin (MIC = 0.5 μg/mL), and compound 60 (-2.28 log 10  CFU/mL) also displayed superior in vivo antibacterial efficacy than tiamulin (-1.40 log 10  CFU/mL) in reducing MRSA load in the mouse thigh infection model. The time-kill study and the post-antibiotic effect study indicated that compound 60 showed a faster bactericidal kinetic and longer PAE time (exposure to 2 × MIC and 4 × MIC for 2 h, the PAE was 4.06 and 4.27 h) against MRSA compared with tiamulin (exposure to 2 × MIC and 4 × MIC for 2 h, the PAE was 1.72 and 2.14 h). Meanwhile, most of these compounds had no significant inhibitory effect on RAW 264.7 cells and HepG2 cells at the concentration of 4 μg/mL. Additionally, the development of resistance study showed that MRSA did not easily develop resistance against compound 60 compared with tiamulin after induction for 8 passages., 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 © 2021 Elsevier Masson SAS. All rights reserved.)

Tetracyclic norditerpene dilactones are an important class of terpenoids that have been isolated from both terrestrial and marine sources, typically from Podocarpus plants and from filamentous fungi. This class of molecules shares a common 6/6/6/5 tetracyclic ring skeleton, which possesses a densely oxygenated carbon framework and contiguous stereocenters. What's more challenging for synthetic chemists are the consecutive sp 2 -hybridized carbon centers, which exacerbates the strain/rigidity of the whole molecule. In addition, many of these molecules display promising biological activities, such as antitumor, insecticidal, anti-feedant, allelopathic, and antibiotic activities. The unique structures and interesting biological profiles of norditerpene dilactones have attracted considerable attention from synthetic chemists. Herein we summarize the synthetic efforts with respect to tetranorditerpene dilactones.

We herein describe a new approach for the efficient and asymmetric construction of the tricyclic core of eurifoloid A, which possesses a unique and highly strained bicyclo[4.4.1] ring system. A rhodium-catalyzed intramolecular [3 + 2] dipolar cycloaddition was developed to install synthetically challenging bridged bicyclo[4.3.1] ring systems. The reported chemistry shows the feasibility of constructing the eurifoloid A framework using a diastereoselective intramolecular [3 + 2] cycloaddition and a ring enlargement.