~
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`Pergamon
`
`Bioorganic & Medicinal Chemistry Letters 8 (1998) 687-690
`
`8IOORGAN1C &
`MEDICINAL CHEMISTRY
`LETTERS
`
`POTENT HIV PROTEASE INHIBITORS INCORPORATING HIGH-AFFINITY
`
`P2-LIGANDS AND (R).(HYDROXYETHYLAMINO)SULFONAMIDE ISOSTERE
`
`a
`.
`. a
`¯
`Arun K. Ghosh,*’ a John F. Kinca~d, Wonhwa Cho,a D. Eric Walters,b K. Kslshnan,
`. a
`a
`a
`.
`c
`¯
`Khaja Azhar Hussaln, Yumee Koo, Hanna Cho, Clare Rudall,a Lores Holland, and Jim Buthodc
`
`Department of Chemistry, University of lllinois at Chicago, 845 West Taylor Street,
`
`Chicago, IL 60607; bDepartrnent of Biological Chemistry, Finch University of Health Sciences/
`
`The Chicago Medical School, North Chicago, IL 60064, U.S.A. and HT Research Institute,
`
`Life Science Department, Chicago, IL 60616, U.S.A.
`
`Received 5 December 1997; accepted 6 February 1998
`
`Abstract: Design and synthesis of a series of very potent nonpeptide HIV protease inhibitors are described. The
`
`inhibitors are derived from novel high affinity P2-1igands and (R)-(hydroxyethylamino)sulfonamide isostere.
`© 1998 Elsevier Science Ltd. All rights reserved.
`
`Recent approval of H1V protease inhibitors in combination with reverse transcriptase inhibitors has marked
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`a new era of AIDS chemotherapy.1 The new therapies have changed the course of HIV management and the
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`progression of AIDS. However, the major new challenges are now to eliminate substantial ’peptide-like’ character
`
`as well as to combat the emergence of resistance to these protease inhibitors.2 In recognition of these problems,
`
`recent research efforts have been devoted to the design and synthesis of nonpeptidal protease inhibitors that are
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`potent against mutant strains resistant to the currently approved protease inhibitors.3 Successful execution of this
`
`approach may substantially delay the emergence of resistant clinical H1V strains and at the same time alleviate the
`
`problems of ’peptide-like’ character.
`
`As part of our continuing efforts, we recently designed a number of nonpeptidal high-affinity ligands for
`
`the H/V protease substrate binding site, based upon various available three-dimensional structures of the protein-
`
`ligand complexes.4 One of the important elements of our ligand design is to incorporate stereochemically defined
`
`and conformationally constrained cyclic ether and cyclic sulfone functionalities that will replace peptide bonds and
`
`mimic the biological mode of action. As we have previously demonstrated, incorporation of these designed
`
`nonpeptidal ligands into Ro 31-8959la based hydroxyethylamine isosteres resulted in HIV protease inhibitors
`
`that are potent, selective and orally bioavailable in laboratory animals.4 As exemplified, a stereochemically
`
`H
`
`H
`
`Oph~
`
`H
`
`0960-894X/981519.00 © 1998 Elsevier Science Ltd. All rights reserved.
`PII: S0960-894X(98)00098-5
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`688
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`A. K. Ghosh et al. / Bioorg. Med. Chem. Lett. 8 (1998)687-690
`
`defined 3(S)-tetrahydrofuran ring can serve as a surrogate (inhibitor 1, Ki = 87 nM) for the asparagine side
`
`chain of Ro 31-8959.4h Incorporation of this 3(S)-tetrahydrofuran ligand by Vertex Laboratories in (R)-
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`(hydroxyethyl)sulfonamide based isostere however, afforded very potent and orally active inhibitor 2 (VX-478)
`
`which is currently in advanced clinical trials.5 Encouraged by this report, we subsequently investigated the
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`potency enhancing effect of other structurally novel high-affinity ligands in the in (R)-(hydroxyethyl)sulfonamide
`
`based isostere.5,6 Herein we report that the incorporation of the novel P~-ligands in sulfonamide isosteres
`provided a series of very potent and nonpeptidal HIV protease inhibitors.
`The synthesis of various inhibitors with the novel P2-1igands is outlined in Scheme 1. The previously
`
`described4f azido epoxide 3 was reacted with isobutylamine in 2-propanol at 80 °C for 12 h to afford azidoalcohol
`
`5. Treatment of 5 with p-methoxybenzenesulfonyl chloride and p-nitrobenzenesulfonyl chloride in the presence
`of aqueous NaHCO3 provided the corresponding azides. The resulting azides were hydrogenated over 10% Pd-C
`in ethyl acetate to afford the amine 6a, lle, and diamines lib, respectively (75-78% overall from 3). Above
`
`amines were transformed into the various target inhibitors 7 listed in Table 1 by an alkoxycarbonylation of the
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`respective known4 optically pure alcohol with the mixed carbonates in methylene chloride in the presence of 3
`
`equiv of triethylamine at 23 °C for 12 h (80-85%).7
`
`Scheme 1
`
`iPrOH
`
`80 °C, 12 h
`
`~ ~ NH2
`Ns
`+
`
`P~/~
`
`3
`
`4
`
`N 3~-M,,.../N. H
`
`1. x---~X--SO~CI, Py
`2. H2, 10% Pd-C
`
`As shown in Table 1, incorporation of urethane of 3(S)-hydroxytetrahydrothiophene as the P2-1igands
`provided the inhibitor 8 with enzyme inhibitory potency (K) of 2.5 nM in enzyme inhibitory assay as developed
`
`by Toth and Marshall.8 Inhibitor 8 has prevented the spread of HIV-1 in MT4 human T-lymphoid cells infected
`
`with fflB isolate at a concentration of 47 nM (ID50).9, 10 Consistent with our earlier observation, oxidation of
`
`the ring sulfur to the sulfolane derivative 9 resulted in enhancement of both enzyme inhibitory as well as antiviral
`
`potencies.4d Incorporation of 2(R),3(R)-isopropylsulfolane has also resulted in potent protease inhibitors.
`Unlike Ro 31-8959 derived hydroxyethylamine series, incorporation of the cis-isopropyl substituent did not
`provide significant potency enhancement. Interestingly however, the 4-methoxybenzenesulfonamide derivative
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`A. K. Ghosh et al. /Bioorg. Med. Chem. Lett. 8 (1998) 687-690 689
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`Table 1. Structure and Inhibitory Potencies of Various Protease inhibitorsa
`
`Compd R
`
`X
`
`Ki(nM) IDs0(nM) Compd R X
`
`Ki(nM) IDs0 (nM)
`
`II
`
`~
`
`0~’ 0
`
`OMe
`
`2.5
`
`47
`
`2
`
`NH2
`
`1.6
`
`15
`
`O~
`
`OMe
`
`1.2
`
`19
`
`4.5
`13 ~’-- I~ ,X~L~.,H
`2.1
`NH2
`
`10
`
`~o,..
`~ _.[
`O~of~"~
`
`OMe
`
`1./, _+ 0.2
`(n = 3)
`
`18
`
`14
`
`6.~
`
`OMe
`
`1.1 -!:0.4
`1.4___0.25
`(n = 4) (n = 5)
`
`NH2
`
`1.5
`
`40
`
`15
`
`H
`
`CH3
`
`1.2
`
`3.5
`
`OMe
`
`1.5
`
`12
`
`OMe
`
`2.2
`
`4.5
`
`a Inhibitor 17 (Ro-31-8959)lc displayed, Ki = 1.4 + 0.2 nM (n = 3) and IDs0 = 18 nM (n -- 2) in this assay.
`
`10 (IDs0 = 18 nM) has shown enhanced antiviral activity compared to inhibitor 11 (IDs0 = 40 nM) which
`
`contains 4-aminobenzenesulfonamide similar to VX-478 sulfonamide isostere.5 Consistent with this observation,
`4-methoxysulfonamide derivative 12 exhibited enhanced antiviral potency compared to 2 (VX-478). Introduction
`of a stereochernically defined 3(R),3a(S),6a(R)-bis-tetrahydrofuranyl urethane (bis-THF) in the sulfonamide
`isostere afforded extremely potent inhibitor 14 with Ki= 1.1 + 0.4 nM (n = 4) and IDso= 1.4 + 0.25 nM (n =
`
`5).11 Again, 4-methoxybenzenesulfonamide is more potent than the 4-aminobenzenesulfonamide 13 or the
`
`toluenesulfonamide 15. inhibitor 16 with 3(S),3a(S),7a(S)-hexahydrofuropyranyl urethane has also exhibited
`remarkable in vitro properties. In an effort to gain insight into the ligand binding site interactions, modeled
`
`energy-minimized structures of the inhibitors 13 and 14 were created in the VX-478 inhibited HIV- 1 active site.5
`
`It appeared that both oxygen atoms of the bis-THF ligands of 13 and 14 are within hydrogen bonding distance to
`ASP 29 and Asp 30 NH and the 4-methoxyl oxygen of inhibitor 14 is within hydrogen-bonding distance to ASP
`29’ and Asp 30’ NH and this may account for the potency enhancing effect of the 4-methoxy derivative.
`In conclusion, incorporation of novel nonpeptidal ligands in the (R)-(hydroxyethyl)sulfonamide isostere
`
`has provided a series of very potent and structurally diverse protease inhibitors. Further optimization as well as
`in-depth biological studies of the selected protease inhibitors are the subject of our ongoing investigation.
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`690
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`A. K. Ghosh et aL / Bioorg. Med. Chem. Lett. 8 (1998) 687-690
`
`Acknowledgment: Financial support of this work by the National Institute of Health (GM 53386) is gratefully
`acknowledged. The authors express their sincere gratitude to Dr. Jordan Tang of Oklahoma Medical Research
`Foundation for expression vector for HIV- 1 protease (pET HIVPR) and GD Searle for substrate for the enzyme
`assay. C. R. is the Jean Dreyfus Boissevain scholar for undergraduate research.
`
`References and Notes:
`
`1.
`
`(a) Kempf, D. J.; Marsh, K. C.; Denissen, J. F.; McDonald, E.; Vasavononda, S.; Flentge, C. A.; Green, B.
`G.; Fino, L.; Park, C. H.; Kong, X.-P.; Wideburg, N. E.; Saldivar, A.; Ruiz, L.; Kati, W. M.; Sham, H. L.;
`Robins, T.; Stewart, K. D.; Hsu, A.; Plattner, J. J.; Leonard, J.; Norbeck, D. Proc. Natl. Acad. Sci. U. S.
`A. 1995, 92, 2484; (b) Vacca, J. P.; Dorsey, B. D.; Schleif, W. A.; Levin, R. B.; McDaniel, S. L.; Darke,
`P. L.; Zugay, J.; Quintero, J. C.; Blahy, O. M.; Roth, E.; Sardana, V. V.; Schlabach, A. J.; Graham, P. I.;
`Condra, J. H.; Gotlib, L.; Holloway, M. K.; Lin, J.; Chen, I-W.; Vastag, K.; Ostovic, D.; Anderson, P. S.;
`Emini, E. A.; Huff, J. R. Proc. Natl. Acad. Sci., U.S.A. 1994, 91, 4096; (c) Roberts, N. A.; Martin, J. A.;
`Kinchington, D.; Broadhurst, A. V.; Craig, J. C.; Duncan, I. B.; Galpin, S. A.; Handa, B. K.; Kay, J.;
`Krohn, A.; Lambert, R. W.; Merrett, J. H.; Mills, J. S.; Parkes, K. E. B.; Redshaw, S.; Ritchie, A. J.;
`Taylor, D. L.; Thomas, G. J.; Machin, P. J. Science 1990, 248, 358 and references cited therein.
`2. (a) Jacobsen, H.; Yasargil, K.; Winslow, D. L.; Craig, J. C.; Krohn, A.; Duncan, I. B.; Mous, J. Virol.
`1995, 206, 527; (b) Condra, J. H.; Schleif, W. A.; Blahy, O. M.; Gabryelski, L. J.; Graham, D. J.;
`Quintero, J. C.; Rhodes, A.; Robbins, H. L.; Roth, E.; Shivapraksh, M.; Titus, D.; Yang, T.; Toppler, H.;
`Squires, K. E.; Deutsch, P. J.; Emini, E. A. Nature 1995, 374, 569; (c) Ho, D. D.; Toyoshima, T.; Mo,
`H.; Kempf, D. J.; Norbeck, D.W.; Chen, C. M.; Wideburg, N. E.; Burt, S. K.; Erickson, J. W.; Singh, M.
`K. J. Virol. 1994, 68, 2016 and references cited therein.
`3. Jadhav, P. K.; Ala, P.; Woerner, F. J.; Chang, C.-H.; Garber, S. S.; Anton, E. D.; Bacheler, L. T. J. Med.
`Chem. 1997, 40, 181 and references cited therein.
`4. (a) Ghosh, A. K.; Kincaid, J. F.; Waiters, 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; (b) Ghosh,
`A. K.; Thompson, W. J.; Munson, P. M.; Liu, W.; Huff, J. R. Bioorg. Med. Chem. Lett. 1995, 5, 83; (c)
`Ghosh, A. K.; Thompson, W. J.; Fitzgerald, P. M.D.; Culberson, C. J.; Axel, M. G.; McKee, S. P.; Huff,
`J. R.; Anderson, P. S. J. Med. Chem. 1994, 37, 2506; (d) Ghosh, A. K.; Lee, H. Y.; Thompson, W. J.;
`Culberson, C; Holloway, M. K.; McKee, S. P.; Munson, P. M.; Duong, T. T.; Smith, A. M.; Darke, P. L.;
`Zugay, J. A.; Emini, E. A.; Schleif, W. A.; Huff, J. R.; Anderson, P. S. J. Med. Chem. 1994, 37, 1177;
`(e) Thompson, W. J.; Ghosh, A. K.; Holloway, M. K.; Lee, H. Y.; Munson, P. M.; Schwering, J. E.; Wai,
`J. M.; Darke, P. L.; Zugay, J. A.; Emini, E. A.; Schleif, W. A.; Huff, J. R.; Anderson, P. S. J. Am. Chem.
`Soc. 1993, 115, 801; (f) Ghosh, A. K.; Thompson, W. J.; Holloway, M. K.; Mckee, S. P.; Duong, T.
`T.; Lee, H. Y.; Munson, P. M.; Smith, A. M.; Wai, J. M.; Darke, P. L.; Zugay, J. A.; Emini, E. A.;
`Schleif, W. A.; Huff, J. R.; Anderson, P. S. J. Med. Chem. 1993, 36, 2300 ; (g) Ghosh, A. K.;
`Thompson, W. J.; Lee, H. Y.; McKee, S. P.; Munson, P. M.; Duong, T. T.; Darke, P. L.; Zugay, J. A.;
`Emini, E. A.; Schleif, W.A.; Huff, J. R.; Anderson, P. S. J. Med. Chem. 1993, 36, 924; (h) Ghosh, A.
`K.; Thompson, W. J.; McKee, S. P.; Duong, T. T.; Lyle, T.A.; Chen, J. C.; Darke, P. L.; Zugay, J. A.;
`Emini, E. A.; Schleif, W. A.; Huff, J. R.; Anderson, P. S. J. Med. Chem. 1993, 36, 292.
`5. Kim, E. E.; Baker, C. T.; Dwyer, M. D.; Murcko, M. A.; Rao, B. G.; Tung, R. D.; Navia, M. A. J. Am.
`Chem. Soc. 1995, 117, 1181.
`6. Vazquez, M. L.; Bryant, M. L.; Clare, M.; DeCrescenzo, G. A.; Doherty, E. M.; Freskos, J. N.; Getman,
`D. P.; Houseman, K. A.; Julien, J. A.; Kocan, G. P.; Mueller, R. A.; Shieh, Huey-Sheng.; Stallings, W. C.;
`Stegeman, R. A.; Talley, J. J. J. Med. Chem. 1995, 38, 581.
`7. Ghosh, A. K.; Duong, T. T.; McKee, S. P. Tetrahedron Lett. 1991, 32, 4251; (b) Ghosh, A. K.; Duong, T.
`T.; McKee, S. P.; Thompson, W. J. Tetrahedron Lett. 1992, 33, 2781.
`8. Toth, M. V.; Marshall, G. R.; lnt. J. Pep. Prot. Res. 1990, 36, 544.
`9.
`In-house prepared 17 (Ro 31-8959) and 2 (VX-478) exhibited IDs0 value of 18 nM and 15 nM. For Ro 31
`8959, Craig and coworkers have reported IC90 values of 6-30 nM in cell culture assay. 11 However, the
`assay protocol differs widely in that syneytia formation rather than p24 production was monitored as endpoint,
`and cell types other than MT4 were employed.
`10. Craig, J. C.; Duncan, I. B.; Hockley, D.; Grief, C.; Roberts, N. A.; Mills, J. S.; Antiviral Res. 1991, 16,
`295 and references cited therein.
`11. Inhibitor 14 has exhibited enzymatic K~ = 0.016 nM and antiviral cell RNA-IC90 = 0.71 nM in the assay
`protocol developed at the Dupont Merck Company; personal communication: Dr. Susan Erickson-Viitanen.
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`Lupin Ex. 1002 (Page 4 of 4)