Bioorganic & Medicinal Chemistry Letters xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl
Design and synthesis of highly potent HIV-1 protease inhibitors with novel isosorbide-derived P2 ligands Xin Qiu , Guo-Dong Zhao , Long-Qiang Tang, Zhao-Peng Liu ⇑ Institute of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, Shandong Province, PR China
a r t i c l e
i n f o
Article history: Received 11 February 2014 Revised 3 April 2014 Accepted 5 April 2014 Available online xxxx Keywords: HIV-1 protease inhibitors Isosorbides P2 ligand Drug-resistant Design Synthesis
a b s t r a c t The design, synthesis, and biological evaluation of a series of six HIV-1 protease inhibitors incorporating isosorbide moiety as novel P2 ligands are described. All the compounds are very potent HIV-1 protease inhibitors with IC50 values in the nanomolar or picomolar ranges (0.05–0.43 nM). Molecular docking studies revealed the formation of an extensive hydrogen-bonding network between the inhibitor and the active site. Particularly, the isosorbide-derived P2 ligand is involved in strong hydrogen bonding interactions with the backbone atoms. Ó 2014 Elsevier Ltd. All rights reserved.
HIV/AIDS a chronic, potentially life-threatening disease that interferes with the immune system, and approximately 1.8 million people died of AIDS-related illnesses in 2010.1 Although there is no effective vaccine available,2 therapies involving more than two drugs from reverse transcriptase inhibitors, protease inhibitors, and a fusion inhibitor, called HAART (highly active antiretroviral therapy), form an effective options to reduce plasma HIV mRNA to undetectable level and thus improve the lives of AIDS patients.2,3 HIV-1 protease (PR) is critical for viral particle maturation because it cleaves the viral precursor polypeptides Gag and Gag-Pol into the mature structural and enzymatic proteins.4,5 Therefore, PR is an effective target for antiviral drugs, and in fact, the FDA has approved 10 different protease inhibitors (PIs) since 1995.6 However, clinically used HIV-1 PIs have been associated with the emergence of drug resistant viruses, unfavorable side effects, poor ADMET properties, and long-term high dose requirements.7–9 Consequently, the development of structurally new and highly potent HIV protease inhibitors with different resistance profiles is still of interest.10 HIV-1 PR is a C2 symmetrical homodimer with 99 residues per monomer. Structural regions critical for PR activity and stability are the dimer interface including the catalytic Asp25 from each subunit and the flexible flaps comprising residues 45–55.11 ⇑ Corresponding author. Tel.: +86 531 88382006; fax: +86 531 88382548.
E-mail address: [email protected] (Z.-P. Liu). These authors contributed equally to this project.
Analysis of the structural and biochemical properties of PR mutants suggests that resistant mutations act by multiple mechanisms, including mutations in the binding site that directly lower inhibitor affinity, mutations at the dimer interface that destabilize the catalytically active dimer, and flap mutations that alter the conformational flexibility.12 Drug resistant PR mutants exhibit decreased binding affinity for inhibitors while maintaining the critical PR function in viral replication.13–15 Two HIV-1 PIs drugs, Tipranavir16 and Darunavir,17,18 have recently been approved by the FDA for use in salvage therapies against the emergence of HIV mutants that are resistant to available drugs. X-ray structural studies of Darunavir-bound HIV-1 protease revealed the formation of an extensive hydrogen-bonding network between the inhibitor and the active site.19–21 Particularly, the bis-THF P2 ligand is involved in strong hydrogen bonding interactions with the backbone amides of conserved residues Asp 29 and Asp 30 in the S2 subsite. Such tight interactions are consistently observed with mutant proteases and responsible for the unusually high resistance profile of Darunavir. Thus, the concept of targeting the protein backbone in current structure-based drug design offers a reliable strategy for combating drug resistance.22 In the design of novel PIs with nonpeptidal bis-tetrahydrofuran P2 ligands based upon sorbitol, Ghosh’s group concluded that the position of ring oxygens, ring size, and stereochemistry are all crucial to potency.23 In our efforts to utilize naturally derived P2 ligands, we replaced the P2 bis-THF moiety in Darunavir with a stereochemically defined trans-4-hydroxy-L-prolinamides and discovered two
http://dx.doi.org/10.1016/j.bmcl.2014.04.008 0960-894X/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Qiu, X.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.04.008
2
X. Qiu et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
H O H
H N
O H O
O
R
OH N
S O2
Ph
O
O
H O O
H
1 R = NH2 (Darunavir) 2 R = OMe (TMC-126)
H N
2
RO
R1
OH N Ph
S O2
3a− −f
Figure 1. Darunavir 1, TMC-126 2 and novel HIV-1 PIs 3a–f.
HO
H
3 O
O 6
H
O
O2N
O
O
a
H
O
ONO2
ISMN
Table 1 Inhibitory activities of compounds 3a–f against wild-type HIV-1 protease
O
H
4
ONO2
ref. 24 TBSO O
H
H 5
R1
R2
IC50a
Compds
R1
R2
IC50a
3a 3b 3c Indinavir
OMe OMe OMe
NO2 H Me
0.11 nM 0.10 nM 0.05 nM 98.5, by HPLC). The enzyme inhibitory potencies of the synthetic compounds 3af were measured against wild-type HIV-1 protease using fluorometric assays with the commercial drug Indinavir as a control,24,29,30 and the results are given in Table 1. All the six compounds with the isosorbide-derived P2 ligands are very potent
R1
OH H2N
A mean value of three parallel experiments with a deviation within 10%. 96.9% inhibition at 10 nM.
b
O
O2N O
Compds
N
a S O2
7 R1 = OMe 8 R1 = NH2 9 R1 = NO2
O H R2O
O H O O
H N
R1
OH N Ph
S O2
3a R1 = OMe, R2 = NO2 3b R1 = OMe, R2 = H 3c R1 = OMe, R2 = Me 3d R1 = NH2, R2 = NO2 3e R1 = NH2, R2 = Me 10 R1 = NO2, R2 = NO2 3f R1 = NH2, R2 = H
b
b
Scheme 2. Reagents and conditions: (a) 4 or 6, Et3N, CH2Cl2, (b) H2, Pd/C, MeOH.
Please cite this article in press as: Qiu, X.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.04.008
X. Qiu et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
3
Figure 2. The binding mode of 3c (red) and Darunavir (green) with the wild HIV-1 protease (PDB code: 4HLA).
Figure 3. The binding mode of 3e (orange) and 3f (green) with the wild HIV-1 protease (PDB code: 4HLA).
HIV-1 PIs, displaying nanomolar or subnanomolar inhibitory potency against the enzyme. The most potent compound 3c had an IC50 of 50 pM. In general, the protease inhibitors 3b and 3c with 4-methoxybenzenesulfonamide at P20 exhibited a significant increase in potency compared to the corresponding 4-amino analogues 3f and 3e. To gain molecular insight into the ligand-binding site interactions responsible for their potent inhibitory activity against the HIV-1 protease, we made the docking study of compound 3c with the wild HIV-1 enzyme (PDB code: 4HLA) by utilizing software Sybyl-x1.3. As shown in Figure 2, compound 3c can interact with the HIV-1 protease in a similar way as the drug Darunavir does.22
It is bound in the active-site cavity through a series of hydrogenbond interactions with the main-chain atoms of the HIV-1 protease. The inhibitor hydroxyl group interacts with the two carboxylate oxygen atoms of the catalytic Asp25 and Asp250 . A tetracoordinated water mediates hydrogen bonds with both NH atoms of the flap residues Ile50/500 as well as the inhibitor’s urethane carbonyl and one of the sulfonamide (SO2) oxygens. The oxygen atom (OMe) of sulfonamide isostere in the P20 position forms a hydrogen bond with the amide NH of Asp300 . A hydrogen bond between the inhibitor urethane amide and the carbonyl oxygen atom of Gly27 is also observed. Moreover, one of the isosorbide ring oxygen in inhibitor 3c is involved in hydrogen bondings with both the
Please cite this article in press as: Qiu, X.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.04.008
4
X. Qiu et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
backbone amide NHs of Asp29 and Asp30 in the S2 subsite, and the other oxygen in the isosorbide ring forms additional hydrogen bonding with the backbone amide NH of Gly48. In contrast, the sulfonyl (SO2) oxygens in 3e and 3f did not form hydrogen bonds with the catalytic water molecule, and there were no hydrogen bondings between the backbone amide NH of Gly48 and one of the oxygen in the isosorbide ring (Fig. 3). This may partially account for the less potency of compounds 3e and 3f in comparison with their counterparts 3c and 3b. In summary, six novel HIV-1 protease inhibitors with the hydroxyethylamine core incorporating isosorbide-derived P2 ligands were designed and synthesized. All the compounds showed excellent enzyme inhibitory activity with IC50 values in the nanomolar or picomolar ranges (0.05–0.43 nM). The computationaldocking results indicated that the most potent compound 3c could make extensive interactions in the HIV-1 protease active site, and the isosorbide-derived P2 ligand was involved in strong hydrogen bondings with the backbone amides of conserved residues Asp 29 and Asp 30 in the S2 subsite. Based on our preliminary finding, more PIs incorporating isosorbide-derived P2 ligands will be synthesized and evaluated for their enzyme inhibitory potencies against wild-type HIV-1 protease and drug-resistant variants in the future. Acknowledgments Thanks for the National Center for Drug Screening of China for the enzyme inhibitory assay. Supplementary data Supplementary data (experimental details and spectroscopic data for compounds 3, 4, 6, 7, 8a–i, 2a–i, procedures for enzyme inhibitory assays) associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.bmcl.2014.04.008. References and notes 1. 2. 3. 4.
UNAIDS Report on the Global AIDS Epidemic; UNAIDS: Geneva, 2010. Brenner, B. G.; Turner, D.; Wainberg, M. A. Expert Opin. Biol. Ther. 2002, 2, 751. Spivak, A. M.; Siliciano, R. F. AIDS 2010, 24, 1603. Darke, P. L.; Nutt, R. F.; Brady, S. F.; Garsky, V. M.; Ciccarone, T. M.; Leu, C. T.; Lumma, P. K.; Freidinger, R. M.; Veber, D. F.; Sigal, I. S. Biochem. Biophys. Res. Commun. 1988, 156, 297. 5. Oroszlan, S.; Luftig, R. B. Curr. Top. Microbiol. Immunol. 1990, 157, 153. 6. De Clercq, E. Int. J. Antimicrob. Agents 2009, 33, 307.
7. Johnson, V. A.; Brun-Vézinet, F.; Clotet, B.; Gunthard, H. F.; Kuritzkes, D. R.; Pillay, D.; Schapiro, J. M.; Richman, D. D. Top. HIV Med. 2007, 15, 119. 8. Armbruster, C. Anti-Infect. Agents Med. Chem. 2008, 7, 201. 9. Anderson, J.; Schiffer, C.; Lee, S.-K.; Swanstrom, R. V. Handb. Exp. Pharmacol. 2009, 189, 85. 10. Qiu, X.; Liu, Z.-P. Curr. Med. Chem. 2011, 18, 4513. 11. Tsantrizos, Y. S. Acc. Chem. Res. 2008, 41, 1252. 12. Weber, I. T.; Agniswamy, J. Viruses 2009, 1, 1110. 13. Wensing, A. M. J.; van Maarseveen, N. M.; Nijhuis, M. Antiviral Res. 2010, 85, 59. 14. Ali, A.; Bandaranayake, R. M.; Cai, Y.; King, N. M.; Kolli, M.; Mittal, S.; Murzycki, J. F.; Nalam, M. N. L.; Nalivaika, E. A.; Özen, A.; Prabu-Jeyabalan, M. M.; Thayer, K.; Schiffer, C. A. Viruses 2010, 2, 2509. 15. Johnson, V. A.; Calvez, V.; Gunthard, H. F.; Paredes, R.; Pillay, D.; Shafer, R.; Wensing, A. M.; Richman, D. D. Top. Antiviral Med. 2011, 19, 156. 16. Thaisrivongs, S.; Strohbach, J. W. Biopolymers 1999, 51, 51. 17. Ghosh, A. K.; Kincaid, J. F.; Cho, W.; Walters, D. E.; Krishnan, K.; Hussain, K. A.; Koo, Y.; Cho, H.; Rudall, C.; Holland, L.; Buthod, J. Bioorg. Med. Chem. Lett. 1998, 8, 687. 18. Surleraux, D. L. N. G.; Tahri, A.; Verschueren, W. G.; Pille, G. M. E.; de Kock, H. A.; Jonckers, T. H. M.; Peeters, A.; De Meyer, S.; Azijn, H.; Pauwels, R.; de Bethune, M.-P.; King, N. M.; Prabu-Jeyabalan, M.; Schiffer, C. A.; Wigerinck, P. B. T. P. J. Med. Chem. 2005, 48, 1813. 19. Tie, Y.; Boross, P. I.; Wang, Y.-F.; Gaddis, L.; Hussain, A. K.; Leshchenko, S.; Ghosh, A. K.; Louis, J. M.; Harrison, R. W.; Weber, I. T. H. J. Mol. Biol. 2004, 338, 341. 20. King, N. M.; Prabu-Jeyabalan, M.; Nalivaika, E. A.; Wigerinck, P.; de Bethune, M.-P.; Schiffer, C. A. J. Virol. 2004, 78, 12012. 21. Kovalevsky, A. Y.; Liu, F.; Leshchenko, S.; Ghosh, A. K.; Louis, J. M.; Harrison, R. W.; Weber, I. T. J. Mol. Biol. 2006, 363, 161. 22. Ghosh, A. K.; Chapsal, B. D.; Weber, I. T.; Mitsuya, H. Acc. Chem. Res. 2008, 41, 78. 23. Ghosh, A. K.; Kincaid, J. F.; Walters, D. E.; Chen, Y.; Chaudhuri, N. C.; Thompson, W. J.; Culberson, C.; Fitzgerald, P. M. D.; Lee, H. Y.; McKee, S. P.; Munson, P. M.; Duong, T. T.; Darke, P. L.; Zugay, J. A.; Schleif, W. A.; Axel, M. G.; Lin, J.; Huff, J. R. J. Med. Chem. 1996, 39, 3278. 24. Gao, B.-L.; Zhang, C.-M.; Yin, Y.-Z.; Tang, L.-Q.; Liu, Z.-P. Bioorg. Med. Chem. Lett. 2011, 21, 3730. 25. Carolan, C. G.; Dillon, G. P.; Gaynor, J. M.; Reidy, S.; Ryder, S. A.; Khan, D.; Marquez, J. F.; Gilmer, J. F. J. Med. Chem. 2008, 51, 6400. 26. Ghosh, A. K.; Gemma, S.; Baldridge, A.; Wang, Y. F.; Kovalevsky, A. Y.; Koh, Y.; Weber, I. T.; Mitsuya, H. J. Med. Chem. 2008, 51, 6021. 27. Tamaki, M.; Han, G. X.; Hruby, J. V. J. Org. Chem. 2001, 66, 3593. 28. Ghosh, A. K.; Leshchenko, S.; Noetzel, M. J. Org. Chem. 2004, 69, 7822. 29. Ali, A.; Reddy, G. S. K. K.; Cao, H.; Anjum, S. G.; Nalam, M. N. L.; Schiffer, C. A.; Rana, T. M. J. Med. Chem. 2006, 49, 7342. 30. The HIV-1 protease was cloned and heterologously expressed in Escherichia coli and purified. All inhibitors were dissolved in DMSO and diluted to appropriate concentrations, and the incubations were performed at 30 °C in 0.1 M sodium acetate-1 M NaCl-1 mM dithiothreitol (DTT)-1 mM EDTA-3% DMSO at pH 5.0 with 5 lM fluorogenic substrate [Arg-Glu(EDANS)-Ser-Gin-Asn-Tyr-Ile-ValGin-Lys(dabcyl)-Arg); Invitrogen Corporation]. Measurements were performed in 96-well plates with a fluorescence microplate reader (FLUO star Galaxy). Excitation and emission wavelengths were 355 and 500 nm, respectively. Assay variability was checked by inclusion of a known inhibitor (Indinavir, GSK). Data were analyzed by nonlinear regression by using SIMFIT and an equation for tightly binding inhibitors.
Please cite this article in press as: Qiu, X.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.04.008
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl
Design and synthesis of highly potent HIV-1 protease inhibitors with novel isosorbide-derived P2 ligands Xin Qiu , Guo-Dong Zhao , Long-Qiang Tang, Zhao-Peng Liu ⇑ Institute of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, Shandong Province, PR China
a r t i c l e
i n f o
Article history: Received 11 February 2014 Revised 3 April 2014 Accepted 5 April 2014 Available online xxxx Keywords: HIV-1 protease inhibitors Isosorbides P2 ligand Drug-resistant Design Synthesis
a b s t r a c t The design, synthesis, and biological evaluation of a series of six HIV-1 protease inhibitors incorporating isosorbide moiety as novel P2 ligands are described. All the compounds are very potent HIV-1 protease inhibitors with IC50 values in the nanomolar or picomolar ranges (0.05–0.43 nM). Molecular docking studies revealed the formation of an extensive hydrogen-bonding network between the inhibitor and the active site. Particularly, the isosorbide-derived P2 ligand is involved in strong hydrogen bonding interactions with the backbone atoms. Ó 2014 Elsevier Ltd. All rights reserved.
HIV/AIDS a chronic, potentially life-threatening disease that interferes with the immune system, and approximately 1.8 million people died of AIDS-related illnesses in 2010.1 Although there is no effective vaccine available,2 therapies involving more than two drugs from reverse transcriptase inhibitors, protease inhibitors, and a fusion inhibitor, called HAART (highly active antiretroviral therapy), form an effective options to reduce plasma HIV mRNA to undetectable level and thus improve the lives of AIDS patients.2,3 HIV-1 protease (PR) is critical for viral particle maturation because it cleaves the viral precursor polypeptides Gag and Gag-Pol into the mature structural and enzymatic proteins.4,5 Therefore, PR is an effective target for antiviral drugs, and in fact, the FDA has approved 10 different protease inhibitors (PIs) since 1995.6 However, clinically used HIV-1 PIs have been associated with the emergence of drug resistant viruses, unfavorable side effects, poor ADMET properties, and long-term high dose requirements.7–9 Consequently, the development of structurally new and highly potent HIV protease inhibitors with different resistance profiles is still of interest.10 HIV-1 PR is a C2 symmetrical homodimer with 99 residues per monomer. Structural regions critical for PR activity and stability are the dimer interface including the catalytic Asp25 from each subunit and the flexible flaps comprising residues 45–55.11 ⇑ Corresponding author. Tel.: +86 531 88382006; fax: +86 531 88382548.
E-mail address: [email protected] (Z.-P. Liu). These authors contributed equally to this project.
Analysis of the structural and biochemical properties of PR mutants suggests that resistant mutations act by multiple mechanisms, including mutations in the binding site that directly lower inhibitor affinity, mutations at the dimer interface that destabilize the catalytically active dimer, and flap mutations that alter the conformational flexibility.12 Drug resistant PR mutants exhibit decreased binding affinity for inhibitors while maintaining the critical PR function in viral replication.13–15 Two HIV-1 PIs drugs, Tipranavir16 and Darunavir,17,18 have recently been approved by the FDA for use in salvage therapies against the emergence of HIV mutants that are resistant to available drugs. X-ray structural studies of Darunavir-bound HIV-1 protease revealed the formation of an extensive hydrogen-bonding network between the inhibitor and the active site.19–21 Particularly, the bis-THF P2 ligand is involved in strong hydrogen bonding interactions with the backbone amides of conserved residues Asp 29 and Asp 30 in the S2 subsite. Such tight interactions are consistently observed with mutant proteases and responsible for the unusually high resistance profile of Darunavir. Thus, the concept of targeting the protein backbone in current structure-based drug design offers a reliable strategy for combating drug resistance.22 In the design of novel PIs with nonpeptidal bis-tetrahydrofuran P2 ligands based upon sorbitol, Ghosh’s group concluded that the position of ring oxygens, ring size, and stereochemistry are all crucial to potency.23 In our efforts to utilize naturally derived P2 ligands, we replaced the P2 bis-THF moiety in Darunavir with a stereochemically defined trans-4-hydroxy-L-prolinamides and discovered two
http://dx.doi.org/10.1016/j.bmcl.2014.04.008 0960-894X/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Qiu, X.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.04.008
2
X. Qiu et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
H O H
H N
O H O
O
R
OH N
S O2
Ph
O
O
H O O
H
1 R = NH2 (Darunavir) 2 R = OMe (TMC-126)
H N
2
RO
R1
OH N Ph
S O2
3a− −f
Figure 1. Darunavir 1, TMC-126 2 and novel HIV-1 PIs 3a–f.
HO
H
3 O
O 6
H
O
O2N
O
O
a
H
O
ONO2
ISMN
Table 1 Inhibitory activities of compounds 3a–f against wild-type HIV-1 protease
O
H
4
ONO2
ref. 24 TBSO O
H
H 5
R1
R2
IC50a
Compds
R1
R2
IC50a
3a 3b 3c Indinavir
OMe OMe OMe
NO2 H Me
0.11 nM 0.10 nM 0.05 nM 98.5, by HPLC). The enzyme inhibitory potencies of the synthetic compounds 3af were measured against wild-type HIV-1 protease using fluorometric assays with the commercial drug Indinavir as a control,24,29,30 and the results are given in Table 1. All the six compounds with the isosorbide-derived P2 ligands are very potent
R1
OH H2N
A mean value of three parallel experiments with a deviation within 10%. 96.9% inhibition at 10 nM.
b
O
O2N O
Compds
N
a S O2
7 R1 = OMe 8 R1 = NH2 9 R1 = NO2
O H R2O
O H O O
H N
R1
OH N Ph
S O2
3a R1 = OMe, R2 = NO2 3b R1 = OMe, R2 = H 3c R1 = OMe, R2 = Me 3d R1 = NH2, R2 = NO2 3e R1 = NH2, R2 = Me 10 R1 = NO2, R2 = NO2 3f R1 = NH2, R2 = H
b
b
Scheme 2. Reagents and conditions: (a) 4 or 6, Et3N, CH2Cl2, (b) H2, Pd/C, MeOH.
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X. Qiu et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
3
Figure 2. The binding mode of 3c (red) and Darunavir (green) with the wild HIV-1 protease (PDB code: 4HLA).
Figure 3. The binding mode of 3e (orange) and 3f (green) with the wild HIV-1 protease (PDB code: 4HLA).
HIV-1 PIs, displaying nanomolar or subnanomolar inhibitory potency against the enzyme. The most potent compound 3c had an IC50 of 50 pM. In general, the protease inhibitors 3b and 3c with 4-methoxybenzenesulfonamide at P20 exhibited a significant increase in potency compared to the corresponding 4-amino analogues 3f and 3e. To gain molecular insight into the ligand-binding site interactions responsible for their potent inhibitory activity against the HIV-1 protease, we made the docking study of compound 3c with the wild HIV-1 enzyme (PDB code: 4HLA) by utilizing software Sybyl-x1.3. As shown in Figure 2, compound 3c can interact with the HIV-1 protease in a similar way as the drug Darunavir does.22
It is bound in the active-site cavity through a series of hydrogenbond interactions with the main-chain atoms of the HIV-1 protease. The inhibitor hydroxyl group interacts with the two carboxylate oxygen atoms of the catalytic Asp25 and Asp250 . A tetracoordinated water mediates hydrogen bonds with both NH atoms of the flap residues Ile50/500 as well as the inhibitor’s urethane carbonyl and one of the sulfonamide (SO2) oxygens. The oxygen atom (OMe) of sulfonamide isostere in the P20 position forms a hydrogen bond with the amide NH of Asp300 . A hydrogen bond between the inhibitor urethane amide and the carbonyl oxygen atom of Gly27 is also observed. Moreover, one of the isosorbide ring oxygen in inhibitor 3c is involved in hydrogen bondings with both the
Please cite this article in press as: Qiu, X.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.04.008
4
X. Qiu et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
backbone amide NHs of Asp29 and Asp30 in the S2 subsite, and the other oxygen in the isosorbide ring forms additional hydrogen bonding with the backbone amide NH of Gly48. In contrast, the sulfonyl (SO2) oxygens in 3e and 3f did not form hydrogen bonds with the catalytic water molecule, and there were no hydrogen bondings between the backbone amide NH of Gly48 and one of the oxygen in the isosorbide ring (Fig. 3). This may partially account for the less potency of compounds 3e and 3f in comparison with their counterparts 3c and 3b. In summary, six novel HIV-1 protease inhibitors with the hydroxyethylamine core incorporating isosorbide-derived P2 ligands were designed and synthesized. All the compounds showed excellent enzyme inhibitory activity with IC50 values in the nanomolar or picomolar ranges (0.05–0.43 nM). The computationaldocking results indicated that the most potent compound 3c could make extensive interactions in the HIV-1 protease active site, and the isosorbide-derived P2 ligand was involved in strong hydrogen bondings with the backbone amides of conserved residues Asp 29 and Asp 30 in the S2 subsite. Based on our preliminary finding, more PIs incorporating isosorbide-derived P2 ligands will be synthesized and evaluated for their enzyme inhibitory potencies against wild-type HIV-1 protease and drug-resistant variants in the future. Acknowledgments Thanks for the National Center for Drug Screening of China for the enzyme inhibitory assay. Supplementary data Supplementary data (experimental details and spectroscopic data for compounds 3, 4, 6, 7, 8a–i, 2a–i, procedures for enzyme inhibitory assays) associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.bmcl.2014.04.008. References and notes 1. 2. 3. 4.
UNAIDS Report on the Global AIDS Epidemic; UNAIDS: Geneva, 2010. Brenner, B. G.; Turner, D.; Wainberg, M. A. Expert Opin. Biol. Ther. 2002, 2, 751. Spivak, A. M.; Siliciano, R. F. AIDS 2010, 24, 1603. Darke, P. L.; Nutt, R. F.; Brady, S. F.; Garsky, V. M.; Ciccarone, T. M.; Leu, C. T.; Lumma, P. K.; Freidinger, R. M.; Veber, D. F.; Sigal, I. S. Biochem. Biophys. Res. Commun. 1988, 156, 297. 5. Oroszlan, S.; Luftig, R. B. Curr. Top. Microbiol. Immunol. 1990, 157, 153. 6. De Clercq, E. Int. J. Antimicrob. Agents 2009, 33, 307.
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Please cite this article in press as: Qiu, X.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.04.008
