General Synthesis of N-CF3 Heteroaryl Amides via Successive Fluorination and Acylation of Sterically Hindered Isothiocyanates.

We report the one-pot synthesis of N-CF3 heteroaryl amides (NTFMHA) from heteroaryl carboxylic acids and sterically hindered isothiocyanates, including various amino acid analogues, in the presence of AgF. The key to this reaction is the utilization of free heteroaryl acyl chlorides, rather than their corresponding hydrochloride salts. This method represents a complementary method of our previous work and enables modification to a variety of previously inaccessible structures, including α-tertiary amines and N-CF3-modified pharmaceuticals.

New Indole Diketopiperazine Alkaloids from Soft Coral-Associated Epiphytic Fungus Aspergillus versicolor CGF 9-1-2.

Two new indole diketopiperazine alkaloids (IDAs), (+)19-epi-sclerotiamide (1) and (-)19-epi-sclerotiamide (2), along with 13 known analogs (3-15), were isolated from a soft coral-associated epiphytic fungus Aspergillus versicolor CGF 9-1-2. The structures of two new compounds were established based on the combination of HR-ESI-MS, 1D and 2D NMR spectroscopy, optical rotation measurements and quantum chemical 13 C-NMR, the absolute configurations were determined by experimental and electronic circular dichroism (ECD) calculations. The results of molecular docking showed that all the compounds had a good binding with TDP1, TDP2, TOP1, TOP2, Ache, NLRP3, EGFR, EGFR L858R, EGFR T790M and EGFR T790/L858. Biological evaluation of compounds 3, 6, 8, 11 showed that 3 exerted a strong inhibitory effect on TDP2 with a rate of 81.72 %.

Synthesis and Biological Activities of 11- and 12-Substituted Benzophenanthridinone Derivatives as DNA Topoisomerase IB and Tyrosyl-DNA Phosphodiesterase 1 Inhibitors.

Herein, a series of 11- or 12-substituted benzophenanthridinone derivatives was designed and synthesized for the discovery of dual topoisomerase IB (TOP1) and tyrosyl-DNA phosphodiesterase 1 (TDP1) inhibitors. Enzyme-based assays indicated that two compounds 12 and 38 showed high TOP1 inhibitory potency (+++), and four compounds 35, 37, 39 and 43 showed good TDP1 inhibition with IC50 values ranging from 10 to 18 µM. 38 could induce cellular TOP1cc formation, resulting in the highest cytotoxicity against HCT-116 cells (0.25 µM). The most potent TDP1 inhibitor 43 (10 µM) could induce cellular TDP1cc formation and enhance topotecan-induced DNA damage and showed strong synergistic cytotoxicity with topotecan in both MCF-7 and MCF-7/TDP1 cells.

Discovery, enantioselective synthesis of myrtucommulone E analogues as tyrosyl-DNA phosphodiesterase 2 inhibitors and their biological activities.

As a recently discovered DNA repair enzyme, tyrosyl-DNA phosphodiesterase 2 (TDP2) can specifically repair topoisomerase 2 (TOP2)-mediated DNA damage, resulting in cancer cell resistance to TOP2 inhibitors. Its inhibitors can enhance the anticancer efficacy of TOP2 inhibitors. In this work, we report the discovery of natural product myrtucommulone E as selective TDP2 inhibitor and its first enantioselective total synthesis through a pivotal CPA-catalyzed Michael addition reaction. A series of myrtucommulone E analogues were asymmetrically synthesized and evaluated for TDP2 and TDP1 inhibitions, and cytotoxicity. Analogue (+)-29 shows good TDP2 inhibition potency (5.4 ± 0.25 µM), but no TDP1 inhibition at 100 µM concentration, and can significantly enhance the cytotoxicity of TOP2 inhibitor etoposide in both DU145 (CI = 0.26) and DT40 hTDP2 cells (CI = 0.48).

Synthesis of 11-aminoalkoxy substituted benzophenanthridine derivatives as tyrosyl-DNA phosphodiesterase 1 inhibitors and their anticancer activity.

Tyrosyl-DNA phosphodiesterase 1 (TDP1) is an enzyme that repairs DNA lesions caused by the trapping of DNA topoisomerase IB (TOP1)-DNA break-associated crosslinks. TDP1 inhibitors have synergistic effect with TOP1 inhibitors in cancer cells and can overcome cancer cell resistance to TOP1 inhibitors. Here, we report the synthesis of 11-aminoalkoxy substituted benzophenanthridine derivatives as selective TDP1 inhibitors and show that six compounds 14, 16, 18, 20, 25 and 27 exhibit high TDP1 inhibition potency. The most potent TDP1 inhibitor 14 (IC50 = 1.7 ±â€¯0.24 µM) induces cellular TDP1cc formation and shows synergistic effect with topotecan in four human cancer cell lines MCF-7, A549, H460 and HepG2.

Pyranodipyran Derivatives with Tyrosyl DNA Phosphodiesterase 1 Inhibitory Activities and Fluorescent Properties from Aspergillus sp. EGF 15-0-3.

Four new benzodipyran racemates, namely (±)-aspergiletals A-D (3-6), representing a rare pyrano[4,3-h]chromene scaffold were isolated together with eurotiumide G (1) and eurotiumide F (2) from the soft-coral-derived fungus Aspergillus sp. EGF 15-0-3. All the corresponding optically pure enantiomers were successfully separated by a chiral HPLC column. The structures and configurations of all the compounds were elucidated based on the combination of NMR and HRESIMS data, chiral separation, single-crystal X-ray diffraction, quantum chemical 13C NMR, and electronic circular dichroism calculations. Meanwhile, the structure of eurotiumide G was also revised. The TDP1 inhibitor activities and photophysical properties of the obtained compounds were evaluated. In the TDP1 inhibition assay, as a result of synergy between (+)-6 and (-)-6, (±)-6 displayed strong inhibitory activity to TDP1 with IC50 values of 6.50 ± 0.73 µM. All compounds had a large Stokes shift and could be utilized for elucidating the mode of bioactivities by fluorescence imaging.

Robustadial A and B from Eucalyptus globulus Labill. and their anticancer activity as selective tyrosyl-DNA phosphodiesterase 2 inhibitors.

Tyrosyl-DNA phosphodiesterase 2 (TDP2) is a recently discovered DNA repair enzyme that can repair topoisomerase 2-mediated DNA damage, resulting in cancer cell resistance. In this study, two compounds, robustadial A and B, were isolated from a fraction of the ethyl acetate extract of Eucalyptus globulus Labill. fruits based on TDP2 inhibition screening. The biological experiments indicated that robustadial A and B have TDP2 inhibitory activity with EC50 values of 17 and 42 µM, respectively, but no tyrosyl-DNA phosphodiesterase 1 inhibition at 100 µM. Robustadial A showed significant synergistic effects with the anticancer drug etoposide in four human cancer cell lines, non-small cell lung cancer cell line (A549), prostate cancer cell line (DU145), breast cancer cell line (MCF-7), colorectal adenocarcinoma cell line (HCT-116), and chicken lymphoma cell line (DT40), and chicken lymphoma cell line complementation with human TDP2 (DT40 hTDP2) with combination index values ranging from 0.21 to 0.74. This work will facilitate future efforts for the development of robustadial A-based TDP2 selective inhibitors.

Synthesis of Methoxy-, Methylenedioxy-, Hydroxy-, and Halo-Substituted Benzophenanthridinone Derivatives as DNA Topoisomerase IB (TOP1) and Tyrosyl-DNA Phosphodiesterase 1 (TDP1) Inhibitors and Their Biological Activity for Drug-Resistant Cancer.

As a recently discovered DNA repair enzyme, tyrosyl-DNA phosphodiesterase 1 (TDP1) removes topoisomerase IB (TOP1)-mediated DNA protein cross-links. Inhibiting TDP1 can potentiate the cytotoxicity of TOP1 inhibitors and overcome cancer cell resistance to TOP1 inhibitors. On the basis of our previous study, herein we report the synthesis of benzophenanthridinone derivatives as TOP1 and TDP1 inhibitors. Seven compounds (C2, C4, C5, C7, C8, C12, and C14) showed a robust TOP1 inhibitory activity (+++ or ++++), and four compounds (A13, C12, C13, and C26) showed a TDP1 inhibition (half-maximal inhibitory concentration values of 15 or 19 µM). We also show that the dual TOP1 and TDP1 inhibitor C12 induces both cellular TOP1cc, TDP1cc formation and DNA damage, resulting in cancer cell apoptosis at a sub-micromolar concentration. In addition, C12 showed an enhanced activity in drug-resistant MCF-7/TDP1 cancer cells and was synergistic with topotecan in both MCF-7 and MCF-7/TDP1 cells.

The synthesis of furoquinolinedione and isoxazoloquinolinedione derivatives as selective Tyrosyl-DNA phosphodiesterase 2 (TDP2) inhibitors.

Based on our previous study on the development of the furoquinolinedione and isoxazoloquinolinedione TDP2 inhibitors, the further structure-activity relationship (SAR) was studied in this work. A series of furoquinolinedione and isoxazoloquinolinedione derivatives were synthesized and tested for enzyme inhibitions. Enzyme-based assays indicated that isoxazoloquinolinedione derivatives selectively showed high TDP2 inhibitory activity at sub-micromolar range, as well as furoquinolinedione derivatives at low micromolar range. The most potent 3-(3,4-dimethoxyphenyl)isoxazolo[4,5-g]quinoline-4,9-dione (70) showed TDP2 inhibitory activity with IC50 of 0.46 ± 0.15 µM. This work will facilitate future efforts for the discovery of isoxazoloquinolinedione TDP2 selective inhibitors.

Synthesis and Biological Evaluation of Oleanolic Acid Derivatives as Selective Vascular Endothelial Growth Factor Promoter i-Motif Ligands.

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor and plays a key role in tumor progression. The C-rich DNA sequence of VEGF promoter can form i-motif structure, which is a potential target for the development of novel anticancer agents. However, there is a limited number of chemotypes as the selective ligands of VEGF promoter i-motif, which leaves much room for development. Herein, we report the discovery of the natural oleanolic acid scaffold as a novel chemotype for the development of selective ligands of VEGF i-motif. A series of oleanolic acid derivatives as VEGF promoter i-motif ligands were synthesized. Subsequent evaluations showed that 3c could selectively bind to and stabilize VEGF promoter i-motif without significant binding to G-quadruplex, duplex DNA, and other oncogene i-motifs. Cell-based assays indicated that 3c could effectively downregulate VEGF gene transcription and expression in MCF-7 cells, inhibit tumor cells proliferation and migration, and induce cancer cells apoptosis. This work provides evidence of VEGF promoter i-motif as an anticancer target and will facilitate future efforts for the discovery of oleanolic acid-based selective ligands of VEGF promoter i-motif.

Syntheses and Evaluation of New Bisacridine Derivatives for Dual Binding of G-Quadruplex and i-Motif in Regulating Oncogene c-myc Expression.

The c-myc oncogene is an important regulator for cell growth and differentiation, and its aberrant overexpression is closely related to the occurrence and development of various cancers. Thus, the suppression of c-myc transcription and expression has been investigated for cancer treatment. In this study, various new bisacridine derivatives were synthesized and evaluated for their binding with c-myc promoter G-quadruplex and i-motif. We found that a9 could bind to and stabilize both G-quadruplex and i-motif, resulting in the downregulation of c-myc gene transcription. a9 could inhibit cancer cell proliferation and induce SiHa cell apoptosis and cycle arrest. a9 exhibited tumor growth inhibition activity in a SiHa xenograft tumor model, which might be related to its binding with c-myc promoter G-quadruplex and i-motif. Our results suggested that a9 as a dual G-quadruplex/i-motif binder could be effective in both oncogene replication and transcription and become a promising lead compound for further development with improved potency and selectivity.

Spiroconyone A, a new phytosterol with a spiro [5,6] ring system from Conyza japonica.

Spiroconyone A (1), the first rearranged phytosterol featuring an unusual spiro [5,6] ring system, and nine known compounds (2-10) were isolated from the aerial parts of Conyza japonica. The structure of 1 was elucidated through spectroscopic methods, and its absolute configuration was determined by single-crystal X-ray diffraction analysis. Enzyme-based assay revealed that spiroconyone A showed weak TDP1 inhibition and compounds 7 and 10 showed TDP1 inhibition with IC50 values of 36 µM and 16 µM, respectively. MTT assay indicated that 7 and 10 showed a strong synergistic effect with the clinical TOP1 inhibitor topotecan in MCF-7 cells. Compound 5 displayed the most potent cytotoxicity against MCF-7 cells with a GI50 value of 3.3 µM. Furthermore, a hypothetical biosynthetic pathway for 1 was proposed. This work provides valuable information that the secondary metabolites from Conyza japonica could be developed as anticancer agents.

Secondary metabolites from Isodon ternifolius (D. Don) Kudo and their anticancer activity as DNA topoisomerase IB and Tyrosyl-DNA phosphodiesterase 1 inhibitors.

Based on DNA topoisomerase IB (TOP1) and tyrosyl-DNA phosphodiesterase 1 (TDP1) inhibition of the ethanol extract of the roots of Isodon ternifolius (D. Don) Kudo (Labiatae), its secondary metabolites has been studied. Two new compounds, an ent-abietane diterpenoid isodopene A (1) and a 2,3-seco-triterpene isodopene B (13), along with 25 known compounds were isolated. Their structures were elucidated by spectroscopic analysis and theoretical calculations. The enzyme-based assays indicated that 1 and 13 showed strong (+++) and moderate (++) TOP1 inhibition, respectively. Two chalcone derivatives 11 and 12 were firstly found as dual TDP1 and TOP1 natural inhibitors, and showed synergistic effect with the clinical TOP1 inhibitors topotecan in MCF-7 cells. Compounds 8, 16, and 22 acted as TOP1 catalytic inhibitors with equipotent TOP1 inhibition to camptothecin (++++). Compounds 7 and 8 exhibited significant cytotoxicity against MCF-7, A549, and HCT116 cells with GI50 values in the range of 2.2-4.8 µM. This work would provide valuable information that secondary metabolites from I. ternifolius could be developed as anticancer agents.

Polyphyllosides A-F, six new spirostanol saponins from the stems and leaves of Paris polyphylla var. chinensis.

The first phytochemical investigation on the steroidal saponins from the stems and leaves of Paris polyohylla var. chinensis led to the discovery and characterization of six new spirostanol saponins, named polyphyllosides A-F (1-6), along with four known analogues (7-10). Their structures were unambiguously established via extensive spectroscopic data and chemical methods. Both polyphyllosides A and B had a rare aglycone with a C-4/C-5 double bond and a C-6 hydroxy group moiety, whereas polyphylloside C represents the first saponin with a unique aglycone sharing a C-6/C-7 double bond and a C-5 hydroxy group unit. All these saponins were evaluated for their cytotoxic activities against five selected human cancer cell lines. Among these, the known saponins 7 and 10 exhibited significant cytotoxic effects on HeLa cells with IC50 values of 4.16 and 4.45 µM, respectively. The structure-activity relationships (SAR) of these isolates were also discussed. Flow cytometric analysis indicated that 7 could induce MDA-MB-231 cell death in a concentration-dependent manner. Saponin 7 was proved to affect the cell cycle distribution and induced G2/M phase arrest in MDA-MB-231 cells.

Sesquiterpenoids from the aerial parts of Conyza japonica and their inhibitory activity against nitric oxide production.

Four new sesquiterpenoids, conyterpenols A - D (1-4), along with nineteen known analogues (5-23) were isolated from the aerial parts of Conyza japonica. The structures of 1-4 were determined through spectroscopic analysis, while their absolute configurations were determined by comparison of calculated and experimental electronic circular dichroism (ECD) spectra. Conyterpenol D (4) was a new type of sesquiterpenoid with a seven-membered lactone ring. Compounds 1-23 were evaluated for their inhibitory activity against LPS-induced nitric oxide production in RAW264.7 macrophages and cytotoxicity against human hepatoma cell line (HepG2) and human breast adenocarcinoma cell line (MCF-7). Compounds 3, 4, and 12 displayed moderate inhibition against NO production with IC50 values in the range of 26.4-33.6 µM. And all compounds showed no obvious cytotoxicity against these two cancer cell lines at 100 µM.

Spirostanol and sesquiterpenoid glycosides from the rhizomes of Trillium tschonoskii.

Three new spirostanol glycosides, trilliumosides K-M (1-3), one new sesquiterpenoid glycoside, tritschsesuquiside A (4), along with three known analogues (5-7) were obtained from the rhizomes of Trillium tschonoskii. The structures of new glycosides were elucidated by spectroscopic analyses (HRMS and NMR) and chemical methods. Glycosides 5-7 displayed cytotoxicities against five human cancer cell lines with IC50 values ranging from 10.5 ±â€¯1.0 to 1.0 ±â€¯0.2 µM, with 7 being the most cytotoxic compound with IC50 values of 1.0 ±â€¯0.2, 2.2 ±â€¯1.2, and 3.4 ±â€¯0.4 µM against Huh7, CCRF-CEM, and HeLa cell lines, respectively. The flow cytometric results revealed that both 5 and 6 could induce apoptosis of HCT116 and Huh7 cells.

ZTW-41, a Potent Indolizinoquinoline-5,12-Dione Derivative Against Drug-Resistant Staphylococci and Enterococci Bacteria.

ZTW-41, an indolizinoquinoline-5,12-dione derivative, was investigated for antibacterial activity against Gram-positive bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA). In our study, the MIC90s (minimum inhibitory concentrations) of ZTW-41 against MRSA (MRSA, n = 200), methicillin-sensitive S. aureus (MSSA, n = 100), Enterococcus faecalis (E. faecalis, n = 32), and Enterococcus faecium (E. faecium n = 32) were 0.25, 0.25, 0.125, and 8 µg/mL, respectively, whereas the MBC90s (minimum bactericidal concentrations) were 2, 1, 1, and >32 µg/mL, respectively. ZTW-41 maintained its potency at different pH levels (range 5-9) and in starting inoculum size up to 107 CFU/mL. The presence of human serum (25-75%) increased ZTW-41 MICs by two- to eightfold. Time-kill curves showed that ZTW-41 had bactericidal activity against MRSA, MSSA, and E. faecalis strains within 8 hours, and rebound growth occurred after 8 hours except at higher multiples of the MIC (4 × and 8 × ). In the acute toxicity study, no mortality or signs of toxicity was noted in mice after 14 days of observation at doses <50 mg/kg. ZTW-41 exhibited good selectivity indices (SIs) (SI = IC50/MIC90) ranging from 1.12 to 71.76 against clinical isolates, demonstrating excellent therapeutic selectivity in MRSA, MSSA, and E. faecalis strains. Moreover, the in vivo efficacy (effective dose [ED]50 = 6.59 mg/kg) of ZTW-41 was found comparable with vancomycin. Collectively, our favorable results supported ZTW-41 as a promising investigational candidate for treating drug-resistant bacteria infection.

Synthesis and biological evaluation of 5-aminoethyl benzophenanthridone derivatives as DNA topoisomerase IB inhibitors.

DNA topoisomerase IB (TOP1) regulates DNA topological structure in many cellular metabolic processes and is a validated target for development of antitumor agents. Our previous study revealed that the benzophenanthridone scaffold is a novel chemotype for the discovery of TOP1 inhibitors. In this work, a series of novel 5-aminoethyl substituted benzophenanthridone derivatives have been synthesized and evaluated for TOP1 inhibition and cytotoxicity. Compound 12 exhibits the most potent TOP1 inhibition (+++) and cytotoxicity in human cancer cell lines with GI50 values at nanomolar concentration range. 12 induces the cellular TOP1cc formation and DNA damage, resulting in HCT116 cell apoptosis. The pharmacokinetics, acute toxicity and antitumor efficiency in vivo of 12 were also studied.

The antitumor activity of CYB-L10, a human topoisomerase IB catalytic inhibitor.

DNA topoisomerase IB (TOP1) is a validated target for discovery and development of antitumor agents. Four TOP1 poisons are clinically used for tumor treatment now. In spite of their effectiveness in solid tumors, these camptothecin (CPT) poisons suffer from many shortcomings. Therefore, many investigations have focused on the discoveries of non-CPT poisons and catalytic inhibitors. Herein, we systematically study the antitumor activity of CYB-L10, a novel indolizinoquinolinedione TOP1 catalytic inhibitor discovered in our laboratory. The results indicated that CYB-L10 mainly acts on TOP1 in cancer cells and is not a substrate of the P-glycoprotein. In addition, CYB-L10 can induce apoptosis of HCT116 cells, shows high cytotoxicity against 60 human clinical cancer cell lines (NCI60) with the mean-graph midpoint for growth inhibition of all cancer cell lines of 0.050 µM concentration and obvious antitumor efficiency in vivo in the HCT116 xenograft model.

Syntheses and evaluation of new Quinoline derivatives for inhibition of hnRNP K in regulating oncogene c-myc transcription.

Aberrant overexpression of heterogeneous nuclear ribonucleoprotein K (hnRNP K) is a key feature in oncogenesis and progression of many human cancers. hnRNP K has been found to be a transcriptional activator to up-regulate c-myc gene transcription, a critical proto-oncogene for regulation of cell growth and differentiation. Therefore, down-regulation of c-myc transcription by inhibiting hnRNP K through disrupting its binding to c-myc gene promoter is a potential approach for cancer therapy. In the present study, we synthesized and screened a series of Quinoline derivatives and evaluated their binding affinity for hnRNP K. Among these derivatives, (E)-1-(4-methoxyphenyl)-3-(4-morpholino-6-nitroquinolin-2-yl)prop-2-en-1-one (compound 25) was determined to be the first-reported hnRNP K binding ligand with its KD values of 4.6 and 2.6 µM measured with SPR and MST, respectively. Subsequent evaluation showed that the binding of compound 25 to hnRNP K could disrupt its unfolding of c-myc promoter i-motif, resulting in down-regulation of c-myc transcription. Compound 25 showed a selective anti-proliferative effect on human cancer cell lines with IC50 values ranged from 1.36 to 3.59 µM. Compound 25 exhibited good tumor growth inhibition in a Hela xenograft tumor model, which might be related to its binding with hnRNP K. These findings illustrated that inhibition of DNA-binding protein hnRNP K by compound 25 could be a new and selective strategy of regulating oncogene transcription instead of targeting promoter DNA secondary structures such as G-quadruplexes or i-motifs.