Assessment of Thiosemicarbazone-Containing Compounds as Potential Antileukemia Agents against P-gp Overexpressing Drug Resistant K562/A02 Cells.

P-Glycoprotein (P-gp) overexpression is considered to be the leading cause of multidrug resistance (MDR) and failure of chemotherapy for leukemia. In this study, seventeen thiosemicarbazone-containing compounds were prepared and evaluated as potential antileukemia agents against drug resistant K562/A02 cell overexpressing P-gp. Among them, N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide could significantly inhibit K562/A02 cells proliferation with an IC50 value of 0.96 µM. Interestingly, N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide could dose-dependently increase ROS levels of drug resistant K562/A02 cells, thus displaying a potential collateral sensitivity (CS)-inducing effect and selectively killing K562/A02 cells. Furthermore, N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide possessed potent inhibitory effect on HDAC1 and HDAC6, and could promote K562/A02 cells apoptosis via dose-dependently increasing Bax expression, reducing Bcl-2 protein level, and inducing the cleavage of PARP and caspase3. These present findings suggest that N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide might be a promising lead to discover novel antileukemia agents against P-gp overexpressing leukemic cells.

Synthesis and evaluation of new phenyl acrylamide derivatives as potent non-nucleoside anti-HBV agents.

As a continuation of our previous work, a series of new phenyl acrylamide derivatives (4Aa-g, 4Ba-t, 5 and 6a-c) were designed and synthesized as non-nucleoside anti-HBV agents. Among them, compound 4Bs could potently inhibit HBV DNA replication in wild-type and lamivudine (3TC)/entecavir resistant HBV mutant strains with IC50 values of 0.19 and 0.18 µM, respectively. Notably, the selective index value of 4Bs was above 526, indicating the favorable safety profile. Interestingly, unlike nucleoside analogue 3TC, 4Bs could significantly inhibit 3.5 kb pgRNA expression. Molecular docking study revealed that 4Bs could fit well into the dimer-dimer interface of HBV core protein by hydrophobic, π-π and H-bond interactions. Considering the potent anti-HBV activity, low toxicity and diverse anti-HBV mechanism from that of nucleoside anti-HBV agent 3TC, compound 4Bs might be a promising lead to develop novel non-nucleoside anti-HBV therapeutic agents, and warranted further investigation.

Discovery of thiosemicarbazone-containing compounds with potent anti-proliferation activity against drug-resistant K562/A02 cells.

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) is a major obstacle to successful chemotherapy for leukemia. In this study, a series of thiosemicarbazone-containing compounds (4a-b, 7a-q) were synthesized. Biological evaluation showed that the most active compound 7e displayed potent anti-leukemia activity against P-gp overexpressing drug-resistant K562/A02 cells, with an IC50 value of 0.44 µM. Notably, compound 7e exhibited a selective killing effect on K562/A02 cells by dose-dependently increasing the intracellular levels of reactive oxygen species (ROS), thus exerting a potential collateral sensitivity (CS)-promoting effect in vitro. Moreover, compound 7e could inhibit HDAC1 and HDAC6, and induce the apoptosis of K562/A02 cells by increasing the expression of Bax, decreasing Bcl-2 protein level, and promoting the cleavage of caspase-3 and PARP, respectively. Overall, 7e may be a potential anti-cancer agent against drug-resistant myelogenous leukemia.

Discovery of novel quinazolinone derivatives as potential anti-HBV and anti-HCC agents.

As a continuation of earlier works, a series of novel quinazolinone derivatives (5a-s) were synthesized and evaluated for their in vitro anti-HBV and anti-hepatocellular carcinoma cell (HCC) activities. Among them, compounds 5j and 5k exhibited most potent inhibitory effect on HBV DNA replication in both drug sensitive and resistant (lamivudine and entecavir) HBV strains. Interestingly, besides the anti-HBV effect, compound 5k could significantly inhibit the proliferation of HepG2, HUH7 and SK- cells, with IC50 values of 5.44, 6.42 and 6.75 µM, respectively, indicating its potential anti-HCC activity. Notably, the in vitro anti-HCC activity of 5k were more potent than that of positive control 5-fluorouracil and sorafenib. Further studies revealed that compound 5k could induce HepG2 cells apoptosis by dose-dependently upregulating Bad and Bax expression and decreasing Bcl-2 and Bcl-xl protein level. Considering the potent anti-HBV and anti-HCC effect, compound 5k might be a promising lead to develop novel therapeutic agents towards HBV infection and HBV-induced HCC.

Synthesis and assessment of phenylacrylamide derivatives as potential anti-oxidant and anti-inflammatory agents.

Oxidative stress and inflammation are major causes of numerous life-threatening human diseases. In the present study, we synthesized a series of phenylacrylamide derivatives as novel anti-oxidant and anti-inflammatory agents. Biological evaluation showed that compound 6a could more potently protect HBZY-1 mesangial cells from H2O2-caused oxidative stress than positive controls resveratrol and sulforaphane by dose- and time-dependently impairing the ROS accumulation. Preliminary anti-oxidant mechanism studies indicated that compound 6a could activate Nrf2 and increase the protein and mRNA expression of downstream anti-oxidant enzymes, ie. NQO-1, HO-1, GCLM and GCLC. Notably, 6a could inhibit the production of NO and the activity of NF-κB in LPS-stimulated HBZY-1 mesangial cells, indicating its potential anti-inflammatory activity. Interestingly, both effects could be significantly attenuated by Nrf2 inhibitor TRG, HO-1 inhibitor ZnPP or GCL inhibitor BSO at non-toxic concentrations, confirming that the anti-oxidant and anti-inflammatory activity of 6a is related to the activation of Nrf2 signaling pathway. These results, together with the relatively safety profile, indicated that compound 6a could be a promising lead to develop novel anti-oxidant and anti-inflammatory agents, thus preventing diseases induced by oxidative stress and inflammation.

Synthesis and biological evaluation of bifendate derivatives bearing acrylamide moiety as novel antioxidant agents.

Oxidative stress plays a significant role in the pathogenesis of various human diseases. In this study, a series of bifendate derivatives bearing acrylamide moiety were synthesized and evaluated as anti-oxidant agents. Biological evaluation indicated that compounds 6a and 6e displayed more potent cytoprotective effect against H2O2-induced HBZY-1 mesangial cells death than lead compound bifendate and positive control resveratrol and sulforaphane. Preliminary anti-oxidant mechanism studies showed that compound 6e could diminish the ROS accumulation by dose- and time-dependently activating Nrf2 and increasing the expression of downstream detoxification enzymes NQO-1, HO-1, GCLM and GCLC at protein and mRNA levels, thus displaying potent anti-oxidant activity. Interestingly, the Nrf2 activating effect of 6e is achieved, at least partly, in Michael acceptor and Keap1-dependent manners. These results, together with the low intrinsic cytotoxicity, suggested that compound 6e might be a promising lead for the development of novel anti-oxidant agents to prevent diseases induced by oxidative stress.

Pd-Catalyzed sequential ß-C(sp(3))-H arylation and intramolecular amination of δ-C(sp(2))-H bonds for synthesis of quinolinones via an N,O-bidentate directing group.

The pharmacological importance of 2-quinolinone derivatives is well known. Herein, we developed an effective protocol for the synthesis of 2-quinolinone derivatives by palladium-catalyzed sequential ß-C(sp(3))-H arylation and selective intramolecular C(sp(2))-H/N-H amination starting with aryl iodides and carboxylic acids. A novel directing group, glycine dimethylamide, was used in the synthesis. We synthesized various quinolinone derivatives, including 5-substituted quinolinones, which are difficult to obtain using the traditional pathway. The directing group could be easily removed and could be readily transformed into other useful functional groups.

Palladium-Catalyzed ortho-Olefination of Phenyl Acetic and Phenyl Propylacetic Esters via C-H Bond Activation.

A highly regioselective palladium-catalyzed ester-directed ortho-olefination of phenyl acetic and propionic esters with olefins via C-H bond activation has been developed. A wide variety of phenyl acetic and propionic esters were tolerated in this transformation, affording the corresponding olefinated aromatic compounds. The ortho-olefination of heterocyclic acetic and propionic esters also took place smoothly giving the products in good yields, thus proving the potential utility of this protocol in synthetic chemistry.

Palladium-Catalyzed Oxalyl Amide Directed Silylation and Germanylation of Amine Derivatives.

Palladium-catalyzed direct ortho-silylation of oxalyl amide-protected phenylmethanamine and phenethylamine with commercially available disilanes is reported. Germanylation products were also produced under the same reaction conditions. This protocol tolerated oxalyl amide-protected aliphatic amines, which gave γ-C-H silylation products.

Palladium-catalyzed oxalyl amide assisted direct ortho-alkynylation of arylalkylamine derivatives at δ and ε positions.

Palladium-catalyzed oxalyl amide directed ortho-alkynylation of arylalkylamine derivatives is reported for the first time. A wide variety of ß-arylethamine and γ-arylpropamine derivatives are compatible with this protocol. This method provides a general means to synthesize substituted alkynylarylalkylamine derivatives, highlighting the ability of oxalyl amide in promoting C-H functionalization at unique δ and ε positions.

Direct ortho-C-H functionalization of aromatic alcohols masked by acetone oxime ether via exo-palladacycle.

A simple and practical exo-oxime ether auxilixary for ortho-C-H functionalization of aromatic alcohols has been developed. Selective olefination of aromatic alcohols were first achieved via a six- or seven-membered exo-acetone oxime ether palladacycle with broad substrate scope. In addition, the crystal of the exo-palladacycle intermediate was obtained for the first time, and the application of this method in total synthesis of 3-deoxyisoochracinic acid was accomplished via a novel retro-synthetic disconnection approach, thus demonstrating the utility of this transformation.

Easily accessible auxiliary for palladium-catalyzed intramolecular amination of C(sp²)-H and C(sp³)-H bonds at δ- and ε-positions.

An easily synthesized and accessible N,O-bidentate auxiliary has been developed for selective C-H activation under palladium catalysis. The novel auxiliary showed its first powerful application in C-H functionalization of remote positions. Both C(sp(2))-H and C(sp(3))-H bonds at δ- and ε-positions were effectively activated, thus giving tetrahydroquinolines, benzomorpholines, pyrrolidines, and indolines in moderate to excellent yields by palladium-catalyzed intramolecular C-H amination.