Author's personal copy Bioorganic Medicinal Chemistry Letters 23(2013)4528-4531 Contents lists available at SciVerse Science Direct Bioorganic Medicinal Chemistry Letters LSEVIER journalhomepagewww.elsevier.com/locate/bmcl Tetrazole and triazole as bioisosteres of carboxylic acid: Discovery CrossMark of diketo tetrazoles and diketo triazoles as anti-HCV agents Wu-Hui Song Ming-Ming Liu C, Dong-Wei Zhong, Ye-lin Zhu, Mike Bosscher Lu Zhou De-Yong Ye, Zheng-Hong Yuan".* School of pharmacy, Fudan University, 826 Zhang-Heng road, Shanghai 201203, PR China Key Laboratory of Medical Molecular Virology y. 138 Yi-Xue-Yuan Road, Shanghai 200032, PR China a Dept of Chemistry, Trinity Christian College, 6601 W. College Dr. Palos Heights, IL 60463, Ug.270 Dong-An Road, Shanghai 200032, PR China Shanghai Cancer Center E Department of oncology, Shar ledical College, Fudan University, ARTICLE INFO ABSTRACT of diketo tetrazoles brary 2013 diketo acid, the active site inhibitor of HCV (Hepatitis C virus)polymerase NS5B. Among the synthesize 15June2013 compounds, 4-(4-fluorobenzyloxy ) phenyl diketo triazole(30)exhibited anti-HCV activity with an EC50 Available online 26 June 2013 value of 3. 9 HM and an SI value more than 128. The reduction of viral protein and mRNA levels were also validated, supporting the anti-HCV activity of compound 30. These results provide convincing evidence that the diketo tetrazoles and diketo triazoles can be developed as bioisosteres of a, y-diketo acid to exhi- bit potent inhibitory activity against HCV. e 2013 Elsevier Ltd. All rights reserved. Diketo triazoles Bioisosteres The world health organization estimates that 150 million peo- monoethyl ester of meconic acid(3, Fig. 2), dihydroxypyrimidine ple worldwide are chronically infected with Hepatitis c virus carboxylic acid (4, Fig. 2), 10 multihydroxyl flay (HCV) and 350,000 people each year die of HCv related diseases. Unfortunately, most of these compounds were Protective vaccination is not yet available and pegylated-interferon based antiviral assay because of the poor cellular permeability combined with ribavirin, the current standard therapy is often dif- Since the active site of NS5B is high conserved across all HCv geno- ficult for patients to tolerate and results in a sustained viral re- types'and the mutations at the active site(eg, S sponse (SvR)in only 50% of patients infected with the cantly reduce replication capacity the active site inhibitors predominant genotype 1.Although two new drugs boceprevir have the potential advantage to be active against all genotypes of and telaprevir as Ns3 protease inhibitors were approved by fDa the virus and the drug-resistant variants. 5 for the treatment of genotype 1 chronic hepatitis C recently, due To develop DKAs analogues with higher potential of active site to the potential of drug resistant strains and widespread infection, inhibitors of NS5B and better cellular permeability, we replaced the development of novel anti-HCV agents is still urgent. the free carboxylic acid of DKAs with their bioisosteres triazoles Aryl o, y-diketo acids(DKAs, 1, Fig. 1)were identified as specific, or tetrazoles and used the cell-based HCV replication system and reversible inhibitors of NS5B polymerase, a promising and val- test if a series of diketone triazoles and diketone tetrazoles could idated target for HCV therapies, in the low micromolar range. overcome the physiochemical and pharmacokinetic problems of Mechanistic studies showed that, as pyrophosphate(PPi, 2. DKAs Although a similar replacement of carboxylic acid with tria ig. 1)mimetic inhibitors, DKAs act as product-like analogues zole or tetrazole was successful in the research of integrase(IN) and chelate the two divalent cations(Mg ions)at the active site of NS5B. Due to the chemical and biological instability and poor membrane permeability of diketo acid group, several drug-like scaffolds were designed as analogues or mimics, such as the HO O-OH HO-P. du.cn(D -Y. Ye). 2 ontributed equally to this Letter. Figure 1. Structures of aryl a, y-diketo acids(DKAs, 1)and pyrophosphate(2).Author's personal copy Tetrazole and triazole as bioisosteres of carboxylic acid: Discovery of diketo tetrazoles and diketo triazoles as anti-HCV agents Wu-Hui Song b, , Ming-Ming Liu a,c, , Dong-Wei Zhong a , Ye-lin Zhu a , Mike Bosscher d , Lu Zhou a,⇑ , De-Yong Ye a,⇑ , Zheng-Hong Yuan b,⇑ a Key Laboratory of Smart Drug Delivery , Ministry of Education, School of Pharmacy, Fudan University, 826 Zhang-Heng Road, Shanghai 201203, PR China b Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, 138 Yi-Xue-Yuan Road, Shanghai 200032, PR China c Shanghai Cancer Center & Department of Oncology, Shanghai Medical College, Fudan University, 270 Dong-An Road, Shanghai 200032, PR China dDept. of Chemistry, Trinity Christian College, 6601 W. College Dr., Palos Heights, IL 60463, USA article info Article history: Received 5 February 2013 Revised 12 June 2013 Accepted 15 June 2013 Available online 26 June 2013 Keywords: Anti-HCV activity Diketo tetrazoles Diketo triazoles Bioisosteres abstract A series of diketo tetrazoles and diketo triazoles were designed and synthesized as bioisosteres of a,c￾diketo acid, the active site inhibitor of HCV (Hepatitis C virus) polymerase NS5B. Among the synthesized compounds, 4-(4-fluorobenzyloxy)phenyl diketo triazole (30) exhibited anti-HCV activity with an EC50 value of 3.9 lM and an SI value more than 128. The reduction of viral protein and mRNA levels were also validated, supporting the anti-HCV activity of compound 30. These results provide convincing evidence that the diketo tetrazoles and diketo triazoles can be developed as bioisosteres of a,c-diketo acid to exhi￾bit potent inhibitory activity against HCV. 2013 Elsevier Ltd. All rights reserved. The world health organization estimates that 150 million peo￾ple worldwide are chronically infected with Hepatitis C virus (HCV) and 350,000 people each year die of HCV related diseases.1 Protective vaccination is not yet available and pegylated-interferon combined with ribavirin, the current standard therapy, is often dif- ficult for patients to tolerate and results in a sustained viral re￾sponse (SVR) in only 50% of patients infected with the predominant genotype 1.2,3 Although two new drugs boceprevir and telaprevir as NS3 protease inhibitors were approved by FDA for the treatment of genotype 1 chronic hepatitis C recently, due to the potential of drug resistant strains4 and widespread infection, the development of novel anti-HCV agents is still urgent.5 Aryl a,c-diketo acids (DKAs, 1, Fig. 1) were identified as specific, and reversible inhibitors of NS5B polymerase, a promising and val￾idated target for HCV therapies, in the low micromolar range.6 Mechanistic studies showed that, as pyrophosphate (PPi, 2, Fig. 1) mimetic inhibitors, DKAs act as product-like analogues and chelate the two divalent cations (Mg2+ ions) at the active site of NS5B.6,7 Due to the chemical and biological instability and poor membrane permeability of diketo acid group, several drug-like scaffolds were designed as analogues or mimics, such as the monoethyl ester of meconic acid (3, Fig. 2),8 dihydroxypyrimidine carboxylic acid (4, Fig. 2),9,10 multihydroxyl flavonoids,11,12 etc. Unfortunately, most of these compounds were inactive in cell￾based antiviral assay because of the poor cellular permeability. Since the active site of NS5B is high conserved across all HCV geno￾types13 and the mutations at the active site (e.g., S282T) signifi- cantly reduce replication capacity,14 the active site inhibitors have the potential advantage to be active against all genotypes of the virus and the drug-resistant variants.15 To develop DKAs analogues with higher potential of active site inhibitors of NS5B and better cellular permeability, we replaced the free carboxylic acid of DKAs with their bioisosteres triazoles or tetrazoles and used the cell-based HCV replication system to test if a series of diketone triazoles and diketone tetrazoles could overcome the physiochemical and pharmacokinetic problems of DKAs. Although a similar replacement of carboxylic acid with tria￾zole or tetrazole was successful in the research of integrase (IN) 0960-894X/$ - see front matter 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.bmcl.2013.06.045 ⇑ Corresponding authors. Tel./fax: +86 21 51980125 (L.Z.). E-mail addresses: zhoulu@fudan.edu.cn (L. Zhou), dyye@shmu.edu.cn (D.-Y. Ye), zhyuan@shmu.edu.cn (Z.-H. Yuan). These authors contributed equally to this Letter. Ar O O P O O P O HO OH HO OH OH O 1 2 Figure 1. Structures of aryl a,c-diketo acids (DKAs, 1) and pyrophosphate(2). Bioorganic & Medicinal Chemistry Letters 23 (2013) 4528–4531 Contents lists available at SciVerse ScienceDirect Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl