Synthesis and Biological Evaluation of Tripartin, a Putative KDM4 Natural Product Inhibitor, and 1-Dichloromethylinden-1-ol Analogues

Targeting N-Methyl-lysine Histone Demethylase KDM4 in Cancer: Natural Products Inhibitors as a Driving Force for Epigenetic Drug Discovery

KDM4A-F enzymes are a subfamily of histone demethylases containing the Jumonji C domain (JmjC) using Fe(II) and 2-oxoglutarate for their catalytic function. Overexpression or deregulation of KDM4 enzymes is associated with various cancers, altering chromatin structure and causing transcriptional dysfunction. As KDM4 enzymes have been associated with malignancy, they may represent novel targets for developing innovative therapeutic tools to treat different solid and blood tumors. KDM4A is the isozyme most frequently associated with aggressive phenotypes of these tumors. To this aim, industrial and academic medicinal chemistry efforts have identified different KDM4 inhibitors. Industrial and academic efforts in medicinal chemistry have identified numerous KDM4 inhibitors, primarily pan-KDM4 inhibitors, though they often lack selectivity against other Jumonji family members. The pharmacophoric features of the inhibitors frequently include a chelating group capable of coordinating the catalytic iron within the active site of the KDM4 enzyme. Nonetheless, non-chelating compounds have also demonstrated promising inhibitory activity, suggesting potential flexibility in the drug design. Several natural products, containing monovalent or bivalent chelators, have been identified as KDM4 inhibitors, albeit with a micromolar inhibition potency. This highlights the potential for leveraging them as templates for the design and synthesis of new derivatives, exploiting nature's chemical diversity to pursue more potent and selective KDM4 inhibitors.

Total Synthesis, structure revision and antifungal activity of palmarumycin B8 and B7

Palmarymycins B8 (1), its regioisomer (2) and B7 (3) were synthesized via 10-, 9-, and 11-steps in 6.5 %, 2.3 % and 0.54 % overall yields from chroman-4-one (4), 4-hydroxyindanone (12), and 2,5-dimethoxybenzaldehyde (20) as the starting materials, using benzyl protection, enol trimethylsilyl ether by TMSOTf, Rubottom oxidation and deprotection with hydrogenation under Pd/C catalyst as the key steps, respectively. Their structures were characterized by 1H, 13C NMR, COSY, HSQC, HMBC and HR-ESI-MS spectral data. The structure of palmarumycin B8 was revised from 1 to 2 based on the total synthesis, 2D NMR analysis and DFT calculation. The antifungal assay results indicated that palmarumycin B8 (1) showed moderate inhibitory activity against Phytophthora capsica. Compounds 15 and 16 exhibited excellent in vitro antifungal activities against P. capsica with EC50 values of 2.17 and 8.50 μg/mL, respectively.

A Diastereoselective Assembly of Tetralone Derivatives via a Tandem Michael Reaction and ipso-Substitution of the Nitro Group

A highly diastereoselective tandem reaction of 2'-nitrochalcones is reported, involving Michael addition and a subsequent ipso-substitution of the nitro group to produce 1-tetralones with two contiguous chiral centers. A related annulation reaction of 2'-nitrochalcones with potassium cyanide affording 1-indanones with a C3-quaternary chiral center is also demonstrated.

Recent Advances with KDM4 Inhibitors and Potential Applications

The histone lysine demethylase 4 (KDM4) family plays an important role in regulating gene transcription, DNA repair, and metabolism. The dysregulation of KDM4 functions is associated with many human disorders, including cancer, obesity, and cardiovascular diseases. Selective and potent KDM4 inhibitors may help not only to understand the role of KDM4 in these disorders but also to provide potential therapeutic opportunities. Here, we provide an overview of the field and discuss current status, challenges, and opportunities lying ahead in the development of KDM4-based anticancer therapeutics.

Transcriptomic and Drug Discovery Analyses Reveal Natural Compounds Targeting the KDM4 Subfamily as Promising Adjuvant Treatments in Cancer

KDM4 proteins are a subfamily of histone demethylases that target the trimethylation of lysines 9 and 36 of histone H3, which are associated with transcriptional repression and elongation respectively. Their deregulation in cancer may lead to chromatin structure alteration and transcriptional defects that could promote malignancy. Despite that KDM4 proteins are promising drug targets in cancer therapy, only a few drugs have been described as inhibitors of these enzymes, while studies on natural compounds as possible inhibitors are still needed. Natural compounds are a major source of biologically active substances and many are known to target epigenetic processes such as DNA methylation and histone deacetylation, making them a rich source for the discovery of new histone demethylase inhibitors. Here, using transcriptomic analyses we determined that the KDM4 family is deregulated and associated with a poor prognosis in multiple neoplastic tissues. Also, by molecular docking and molecular dynamics approaches, we screened the COCONUT database to search for inhibitors of natural origin compared to FDA-approved drugs and DrugBank databases. We found that molecules from natural products presented the best scores in the FRED docking analysis. Molecules with sugars, aromatic rings, and the presence of OH or O- groups favor the interaction with the active site of KDM4 subfamily proteins. Finally, we integrated a protein-protein interaction network to correlate data from transcriptomic analysis and docking screenings to propose FDA-approved drugs that could be used as multitarget therapies or in combination with the potential natural inhibitors of KDM4 enzymes. This study highlights the relevance of the KDM4 family in cancer and proposes natural compounds that could be used as potential therapies.

Cu-catalyzed coupling of indanone oxime acetates with thiols to 2,3-difunctionalized indenones

A Cu-catalyzed coupling reaction of indanone oxime acetates with thiols has been developed for the synthesis of 2,3-functionalized 1-indenones. This protocol has several features including easy mild reaction conditions, stabilized enamine products, good tolerance of functional groups, and no external oxidants. This reaction enables direct derivatization on the indanone ring to provide valuable functionalized indenones at room temperature.

Unravelling KDM4 histone demethylase inhibitors for cancer therapy

Epigenetic enzyme-targeted therapy is a promising new development in the field of drug discovery. To date, histone deacetylases and DNA methyltransferases have been investigated as druggable epigenetic enzyme targets in cancer therapeutics. Histone methyltransferases and lysine demethylase inhibitors are the latest groups of epi-drugs being actively studied in clinical trials. KDM4s are JmjC domain-containing histone H3 lysine 9/36 demethylase enzymes, belonging to the 2-OG-dependent oxygenases, which are upregulated in multiple malignancies. In the recent years, these enzymes have captured much attention as a novel target in cancer therapy. Herein, we traverse the discovery path and current challenges in designing potent KDM4 inhibitors as potential anticancer agents. We discuss the considerable efforts and proposed future strategies to develop selective small molecule inhibitors of KDM4s, highlighting scaffold candidates and cyclic skeletons for which activity data, selectivity profiles and structure-activity relationships (SARs) have been studied.

A New Family of Jumonji C Domain-Containing KDM Inhibitors Inspired by Natural Product Purpurogallin

Aberrant epigenetic modifications are involved in cancer development. Jumonji C domain-containing histone lysine demethylases (KDMs) are found mainly up-regulated in breast, prostate, and colon cancer. Currently, growing interest is focusing on the identification and development of new inhibitors able to block the activity of KDMs and thus reduce tumor progression. KDM4A is known to play a role in several cellular physiological processes, and was recently found overexpressed in a number of pathological states, including cancer. In this work, starting from the structure of purpurogallin 9aa, previously identified as a natural KDM4A inhibitor, we synthesized two main sets of compound derivatives in order to improve their inhibitory activity against KDM4A in vitro and in cells, as well as their antitumor action. Based on the hypothetical biogenesis of the 5-oxo-5H-benzo[7]annulene skeleton of the natural product purpurogallin (Salfeld, 1960; Horner et al., 1961; Dürckheimer and Paulus, 1985; Tanaka et al., 2002; Yanase et al., 2005) the pyrogallol and catechol units were first combined with structural modifications at different positions of the aryl ring using enzyme-mediated oxidative conditions, generating a series of benzotropolone analogs. Two of the synthetic analogs of purpurogallin, 9ac and 9bc, showed an efficient inhibition (50 and 80%) of KDM4A in enzymatic assays and in cells by increasing levels of its specific targets, H3K9me3/2 and H3K36me3. However, these two compounds/derivatives did not induce cell death. We then synthesized a further set of analogs of these two compounds with greater structural diversification. The most potent of these analogs, 9bf, displayed the highest KDM4A inhibitory enzymatic activity in vitro (IC₅₀ of 10.1 and 24.37 μM) in colon cancer cells, and the strongest antitumor action in several solid and hematological human cancer cell lines with no toxic effect in normal cells. Our findings suggest that further development of this compound and its derivatives may lead to the identification of new therapeutic antitumor agents acting through inhibition of KDM4A.

The Clinically Used Iron Chelator Deferasirox Is an Inhibitor of Epigenetic JumonjiC Domain-Containing Histone Demethylases

Fe(II)- and 2-oxoglutarate (2OG)-dependent JumonjiC domain-containing histone demethylases (JmjC KDMs) are "epigenetic eraser" enzymes involved in the regulation of gene expression and are emerging drug targets in oncology. We screened a set of clinically used iron chelators and report that they potently inhibit JMJD2A (KDM4A) in vitro. Mode of action investigations revealed that one compound, deferasirox, is a bona fide active site-binding inhibitor as shown by kinetic and spectroscopic studies. Synthesis of derivatives with improved cell permeability resulted in significant upregulation of histone trimethylation and potent cancer cell growth inhibition. Deferasirox was also found to inhibit human 2OG-dependent hypoxia inducible factor prolyl hydroxylase activity. Therapeutic effects of clinically used deferasirox may thus involve transcriptional regulation through 2OG oxygenase inhibition. Deferasirox might provide a useful starting point for the development of novel anticancer drugs targeting 2OG oxygenases and a valuable tool compound for investigations of KDM function.