Minor Cannabinoids as Inhibitors of Skin Inflammation: Chemical Synthesis and Biological Evaluation.

Despite millennia of therapeutic plant use, deliberate exploitation of Cannabis's diverse biomedical potential has only recently gained attention. Bioactivity studies focus mainly on cannabidiol (CBD) and tetrahydrocannabinol (THC) with limited information about the broader cannabinome's "minor phytocannabinoids". In this context, our research targeted the synthesis of minor cannabinoids containing a lateral chain with 3 or 4 carbon atoms, focusing on cannabigerol (CBG) and cannabichromene (CBC) analogues. Using known and innovative strategies, we achieved the synthesis of 11 C3 and C4 analogues, five of which were inhibitors of skin inflammation, with the CBG-C4 ester derivative emerging as the most potent compound.

Maytansinol Functionalization: Towards Useful Probes for Studying Microtubule Dynamics.

Maytansinoids are a successful class of natural and semisynthetic tubulin binders, known for their potent cytotoxic activity. Their wider application as cytotoxins and chemical probes to study tubulin dynamics has been held back by the complexity of natural product chemistry. Here we report the synthesis of long-chain derivatives and maytansinoid conjugates. We confirmed that bulky substituents do not impact their high activity or the scaffold's binding mode. These encouraging results open new avenues for the design of new maytansine-based probes.

Maytansinol Functionalization: Towards Useful Probes for Studying Microtubule Dynamics.

Invited for the cover of this issue are the groups of Professors Passarella and Pieraccini at the University of Milan, in collaboration with some of the members of TubInTrain consortium. The image depicts work with the elements of nature, in particular the destabilising effect of maytansinol (the constellation) on microtubules (the trees). Read the full text of the article at 10.1002/chem.202203431.

Synthesis of SARS-CoV-2 Mpro inhibitors bearing a cinnamic ester warhead with in vitro activity against human coronaviruses.

COVID-19 now ranks among the most devastating global pandemics in history. The causative virus, SARS-CoV-2, is a new human coronavirus (hCoV) that spreads among humans and animals. Great efforts have been made to develop therapeutic agents to treat COVID-19, and among the available viral molecular targets, the cysteine protease SARS-CoV-2 Mpro is considered the most appealing one due to its essential role in viral replication. However, the inhibition of Mpro activity is an interesting challenge and several small molecules and peptidomimetics have been synthesized for this purpose. In this work, the Michael acceptor cinnamic ester was employed as an electrophilic warhead for the covalent inhibition of Mpro by endowing some peptidomimetic derivatives with such a functionality. Among the synthesized compounds, the indole-based inhibitors 17 and 18 efficiently impaired the in vitro replication of beta hCoV-OC-43 in the low micromolar range (EC50 = 9.14 µM and 10.1 µM, respectively). Moreover, the carbamate derivative 12 showed an antiviral activity of note (EC50 = 5.27 µM) against another hCoV, namely hCoV-229E, thus suggesting the potential applicability of such cinnamic pseudopeptides also against human alpha CoVs. Taken together, these results support the feasibility of considering the cinnamic framework for the development of new Mpro inhibitors endowed with antiviral activity against human coronaviruses.

Dual targeted 2-Benzylideneindanone pendant hydroxamic acid group exhibits selective HDAC6 inhibition along with tubulin stabilization effect.

Abnormal epigenetics has been recognised as an early event in tumour progression and aberrant acetylation of lysine in particular has been understood in tumorigenesis. Therefore, it has become an attractive target for anticancer drug development. However, HDAC inhibitors have limited success due to toxicity and drug resistance concerns. Present study deals with design and synthesis of bivalent indanone based HDAC6 and antitubulin ligands as anticancer agents. Two of the analogues 9 and 21 exhibited potent antiproliferative activities (IC50, 0.36-3.27 µM) and high potency against HDAC 6 enzyme. Compound 21 showed high selectivity against HDAC 6 while 9 exhibited low selectivity. Both the compounds also showed microtubule stabilization effects and moderate anti-inflammatory effect. Dual targeted anticancer agents with concomitant anti-inflammatory effects will be more attractive clinical candidates in future.

Structure-activity exploration of a small-molecule allosteric inhibitor of T790M/L858R double mutant EGFR.

EGFR is a protein kinase whose aberrant activity is frequently involved in the development of non-small lung cancer (NSCLC) drug resistant forms. The allosteric inhibition of this enzyme is currently one among the most attractive approaches to design and develop anticancer drugs. In a previous study, we reported the identification of a hit compound acting as type III allosteric inhibitor of the L858R/T790M double mutant EGFR. Herein, we report the design, synthesis and in vitro testing of a series of analogues of the previously identified hit with the aim of exploring the structure-activity relationships (SAR) around this scaffold. The performed analyses allowed us to identify two compounds 15 and 18 showing improved inhibition of double mutant EGFR with respect to the original hit, as well as interesting antiproliferative activity against H1975 NSCLC cancer cells expressing double mutant EGFR. The newly discovered compounds represent promising starting points for further hit-to-lead optimisation.

Targeting Ovarian Cancer with Chalcone Derivatives: Cytotoxicity and Apoptosis Induction in HGSOC Cells.

Ovarian cancer ranks as the eighth most prevalent form of cancer in women across the globe and stands as the third most frequent gynecological cancer, following cervical and endometrial cancers. Given its resistance to standard chemotherapy and high recurrence rates, there is an urgent imperative to discover novel compounds with potential as chemotherapeutic agents for treating ovarian cancer. Chalcones exhibit a wide array of biological properties, with a particular focus on their anti-cancer activities. In this research, we documented the synthesis and in vitro study of a small library of chalcone derivatives designed for use against high-grade serous ovarian cancer (HGSOC) cell lines, specifically OVCAR-3, OVSAHO, and KURAMOCHI. Our findings revealed that three of these compounds exhibited cytotoxic and anti-proliferative effects against all the tested HGSOC cell lines, achieving IC50 concentrations lower than 25 µM. Further investigations disclosed that these chalcones prompted an increase in the subG1 phase cell cycle and induced apoptosis in OVCAR-3 cells. In summary, our study underscores the potential of chalcones as promising agents for the treatment of ovarian cancer.

Discovery of a Novel Trifluoromethyl Diazirine Inhibitor of SARS-CoV-2 Mpro.

SARS-CoV-2 Mpro is a chymotrypsin-like cysteine protease playing a relevant role during the replication and infectivity of SARS-CoV-2, the coronavirus responsible for COVID-19. The binding site of Mpro is characterized by the presence of a catalytic Cys145 which carries out the hydrolytic activity of the enzyme. As a consequence, several Mpro inhibitors have been proposed to date in order to fight the COVID-19 pandemic. In our work, we designed, synthesized and biologically evaluated MPD112, a novel inhibitor of SARS-CoV-2 Mpro bearing a trifluoromethyl diazirine moiety. MPD112 displayed in vitro inhibition activity against SARS-CoV-2 Mpro at a low micromolar level (IC50 = 4.1 µM) in a FRET-based assay. Moreover, an inhibition assay against PLpro revealed lack of inhibition, assuring the selectivity of the compound for the Mpro. Furthermore, the target compound MPD112 was docked within the binding site of the enzyme to predict the established intermolecular interactions in silico. MPD112 was subsequently tested on the HCT-8 cell line to evaluate its effect on human cells' viability, displaying good tolerability, demonstrating the promising biological compatibility and activity of a trifluoromethyl diazirine moiety in the design and development of SARS-CoV-2 Mpro binders.

Maytansinol Derivatives: Side Reactions as a Chance for New Tubulin Binders.

Maytansinol is a valuable precursor for the preparation of maytansine derivatives (known as maytansinoids). Inspired by the intriguing structure of the macrocycle and the success in targeted cancer therapy of the derivatives, we explored the maytansinol acylation reaction. As a result, we were able to obtain a series of derivatives with novel modifications of the maytansine scaffold. We characterized these molecules by docking studies, by a comprehensive biochemical evaluation, and by determination of their crystal structures in complex with tubulin. The results shed further light on the intriguing chemical behavior of maytansinoids and confirm the relevance of this peculiar scaffold in the scenario of tubulin binders.

Cyrene: A Green Solvent for the Synthesis of Bioactive Molecules and Functional Biomaterials.

In the panorama of sustainable chemistry, the use of green solvents is increasingly emerging for the optimization of more eco-friendly processes which look to a future of biocompatibility and recycling. The green solvent Cyrene, obtained from biomass via a two-step synthesis, is increasingly being introduced as the solvent of choice for the development of green synthetic transformations and for the production of biomaterials, thanks to its interesting biocompatibility, non-toxic and non-mutagenic properties. Our review offers an overview of the most important organic reactions that have been investigated to date in Cyrene as a medium, in particular focusing on those that could potentially lead to the formation of relevant chemical bonds in bioactive molecules. On the other hand, a description of the employment of Cyrene in the production of biomaterials has also been taken into consideration, providing a point-by-point overview of the use of Cyrene to date in the aforementioned fields.

Synthesis and Investigation of the G-Quadruplex Binding Properties of Kynurenic Acid Derivatives with a Dihydroimidazoquinoline-3,5-dione Core.

G-quadruplexes are secondary structures originating from nucleic acid regions rich in guanines, which are well known for their involvement in gene transcription and regulation and DNA damage repair. In recent studies from our group, kynurenic acid (KYNA) derivative 1 was synthesized and found to share the structural features typical of G-quadruplex binders. Herein, structural modifications were conducted on this scaffold in order to assist the binding with a G-quadruplex, by introducing charged hydrophilic groups. The antiproliferative activity of the new analogues was evaluated on an IGROV-1 human ovarian cancer cell line, and the most active compound, compound 9, was analyzed with NMR spectrometry in order to investigate its binding mode with DNA. The results indicated that a weak, non-specific interaction was set with duplex nucleotides; on the other hand, titration in the presence of a G-quadruplex from human telomere d(TTAGGGT)4 showed a stable, although not strong, interaction at the 3'-end of the nucleotidic sequence, efficiently assisted by salt bridges between the quaternary nitrogen and the external phosphate groups. Overall, this work can be considered a platform for the development of a new class of potential G-quadruplex stabilizing molecules, confirming the crucial role of a planar system and the ability of charged nitrogen-containing groups to facilitate the binding to G-quadruplex grooves and loops.

Cannabidiol as Self-Assembly Inducer for Anticancer Drug-Based Nanoparticles.

Cannabidiol (CBD) is a biologically active compound present in the plants of the Cannabis family, used as anticonvulsant, anti-inflammatory, anti-anxiety, and more recently, anticancer drug. In this work, its use as a new self-assembly inducer in the formation of nanoparticles is validated. The target conjugates are characterized by the presence of different anticancer drugs (namely N-desacetyl thiocolchicine, podophyllotoxin, and paclitaxel) connected to CBD through a linker able to improve drug release. These nanoparticles are formed via solvent displacement method, resulting in monodisperse and stable structures having hydrodynamic diameters ranging from 160 to 400 nm. Their biological activity is evaluated on three human tumor cell lines (MSTO-211H, HT-29, and HepG2), obtaining GI50 values in the low micromolar range. Further biological assays were carried out on MSTO-211H cells for the most effective NP 8B, confirming the involvement of paclitaxel in cytotoxicity and cell death mechanism.

Design and Synthesis of New Withaferin A Inspired Hedgehog Pathway Inhibitors.

Withanolides constitute a well-known family of plant-based alkaloids characterised by widespread biological properties, including the ability of interfering with Hedgehog (Hh) signalling pathway. Following our interest in natural products and in anticancer compounds, we report here the synthesis of a new class of Hh signalling pathway inhibitors, inspired by withaferin A, the first isolated member of withanolides. The decoration of our scaffolds was rationally supported by in silico studies, while functional evaluation revealed promising candidates, confirming once again the importance of natural products as inspiration source for the discovery of novel bioactive compounds. A stereoselective approach, based on Brown chemistry, allowed the obtainment and the functional evaluation of the enantiopure hit compounds.

Self-Assembly Nanoparticles of Natural Bioactive Abietane Diterpenes.

Different approaches have been reported to enhance penetration of small drugs through physiological barriers; among them is the self-assembly drug conjugates preparation that shows to be a promising approach to improve activity and penetration, as well as to reduce side effects. In recent years, the use of drug-conjugates, usually obtained by covalent coupling of a drug with biocompatible lipid moieties to form nanoparticles, has gained considerable attention. Natural products isolated from plants have been a successful source of potential drug leads with unique structural diversity. In the present work three molecules derived from natural products were employed as lead molecules for the synthesis of self-assembled nanoparticles. The first molecule is the cytotoxic royleanone 7α-acetoxy-6ß-hydroxyroyleanone (Roy, 1) that has been isolated from hairy coleus (Plectranthus hadiensis (Forssk.) Schweinf). ex Sprenger leaves in a large amount. This royleanone, its hemisynthetic derivative 7α-acetoxy-6ß-hydroxy-12-benzoyloxyroyleanone (12BzRoy, 2) and 6,7-dehydroroyleanone (DHR, 3), isolated from the essential oil of thicket coleus (P. madagascariensis (Pers.) Benth.) were employed in this study. The royleanones were conjugated with squalene (sq), oleic acid (OA), and/or 1-bromododecane (BD) self-assembly inducers. Roy-OA, DHR-sq, and 12BzRoy-sq conjugates were successfully synthesized and characterized. The cytotoxic effect of DHR-sq was previously assessed on three human cell lines: NCI-H460 (IC50 74.0 ± 2.2 µM), NCI-H460/R (IC50 147.3 ± 3.7 µM), and MRC-5 (IC50 127.3 ± 7.3 µM), and in this work Roy-OA NPs was assayed against Vero-E6 cells at different concentrations (0.05, 0.1, and 0.2 mg/mL). The cytotoxicity of DHR-sq NPs was lower when compared with DHR alone in these cell lines: NCI-H460 (IC50 10.3 ± 0.5 µM), NCI-H460/R (IC50 10.6 ± 0.4 µM), and MRC-5 (IC5016.9 ± 0.5 µM). The same results were observed with Roy-OA NPs against Vero-E6 cells as was found to be less cytotoxic than Roy alone in all the concentrations tested. From the obtained DLS results, 12BzRoy-sq assemblies were not in the nano range, although Roy-OA NP assemblies show a promising size (509.33 nm), Pdl (0.249), zeta potential (-46.2 mV), and spherical morphology from SEM. In addition, these NPs had a low release of Roy at physiological pH 7.4 after 24 h. These results suggest the nano assemblies can act as prodrugs for the release of cytotoxic lead molecules.

Convenient Preparation and Spectroscopic Characterization of 7R-Hydroxymatairesinol.

The preparation of 7R-HMR (allo-hydroxymatairesinol) is reported by: (a) NaBH4 kinetic reduction of 7R/7S diastereomeric mixture; and (b) epimerization of the C7 hydroxyl group by Mitsunobu reaction and subsequent ester hydrolysis. The availability of highly pure target compound (7R-HMR) made it possible to confirm the structure of the target compound and to complete the full spectroscopic characterization.

Engineered Ferritin Nanoparticles for the Bioluminescence Tracking of Nanodrug Delivery in Cancer.

The identification of a highly sensitive method to check the delivery of administered nanodrugs into the tumor cells is a crucial step of preclinical studies aimed to develop new nanoformulated cures, since it allows the real therapeutic potential of these devices to be forecast. In the present work, the ability of an H-ferritin (HFn) nanocage, already investigated as a powerful tool for cancer therapy thanks to its ability to actively interact with the transferrin receptor 1, to act as an efficient probe for the monitoring of nanodrug delivery to tumors is demonstrated. The final formulation is a bioluminescent nanoparticle, where the luciferin probe is conjugated on nanoparticle surface by means of a disulfide containing linker (Luc-linker@HFn) which is subjected to glutathione-induced cyclization in tumor cell cytoplasm. The prolonged imaging of luciferase+ tumor models, demonstrated by an in vitro and an in vivo approach, associated with the prolonged release of luciferin into cancer cells by disulfide bridge reduction, clearly indicates the high efficiency of Luc-linker@HFn for drug delivery to the tumor tissues.

Catalytic C3 aza-alkylation of indoles.

The aza-alkylation reaction at indole's C3 position allows the introduction of a differently substituted aminomethyl group, with the formation of a new stereogenic centre. The reaction involves essentially three different partners: an indole, aldehyde and amine. The formation of the reactive iminium species can be catalyzed by metals, Brønsted acids, Lewis acids or organocatalysts. The stereoselective reaction is feasible with satisfactory outcomes. This review summarizes the recent (2000-2019) meaningful papers in which the in-depth study and exploitation of this reactivity are reported.

Cannabidiol as the Substrate in Acid-Catalyzed Intramolecular Cyclization.

The chemical reactivity of cannabidiol is based on its ability to undergo intramolecular cyclization driven by the addition of a phenolic group to one of its two double bonds. The main products of this cyclization are Δ9-THC (trans-Δ-9-tetrahydrocannabinol) and Δ8-THC (trans-Δ-8-tetrahydrocannabinol). These two cannabinoids are isomers, and the first one is a frequently investigated psychoactive compound and pharmaceutical agent. The isomers Δ8-iso-THC (trans-Δ-8-iso-tetrahydrocannabinol) and Δ4(8)-iso-THC (trans-Δ-4,8-iso-tetrahydrocannabinol) have been identified as additional products of intramolecular cyclization. The use of Lewis and protic acids in different solvents has been studied to investigate the possible modulation of the reactivity of CBD (cannabidiol). The complete NMR spectroscopic characterizations of the four isomers are reported. High-performance liquid chromatography analysis and 1H NMR spectra of the reaction mixture were used to assess the percentage ratio of the compounds formed.

Total Synthesis of (-)-Anaferine: A Further Ramification in a Diversity-Oriented Approach.

The piperidine ring is a widespread motif in several natural bioactive alkaloids of both vegetal and marine origin. In the last years, a diversity-oriented synthetic (DOS) approach, aimed at the generation of a library of piperidine-based derivatives, was developed in our research group, employing commercially available 2-piperidine ethanol as a versatile precursor. Here, we report the exploration of another ramification of our DOS approach, that led us to the stereoselective total synthesis of (-)-anaferine, a bis-piperidine alkaloid present in Withania somnifera extract. This natural product was obtained in 9% overall yield over 13 steps, starting from a key homoallylic alcohol previously synthesised in our laboratory. Therefore, the collection of piperidine-derivatives accessible from 2-piperidine ethanol was enriched with a new, diverse scaffold.

Correction: Self-assembled 4-(1,2-diphenylbut-1-en-1-yl)aniline based nanoparticles: podophyllotoxin and aloin as building blocks.

Correction for 'Self-assembled 4-(1,2-diphenylbut-1-en-1-yl)aniline based nanoparticles: podophyllotoxin and aloin as building blocks' by Gaia Fumagalli, et al., Org. Biomol. Chem., 2017, DOI: 10.1039/c6ob02591a.