J.Med. Chem. 1992,35, 3691-3698
3691
Novel 1,2,4-Oxadiazeles and 1,2,4-Thiadiazoles as Dual 5-Lipoxygenase and Cyclooxygenase Inhibitors’ Paul C. Unangst,*lt Gary P. Shrum,t David T. Connor,+Richard D. Dyer,t and Denis J. Schriert Departments of Chemistry and Immunopathology, Parke-Davis Pharmaceutical Research Division, Warner-Lambert Company, 2800 Plymouth Road, Ann Arbor, Michigan 48105 Received March 2, 1992
A series of 1,2,4-oxadiazolesand 1,2,4-thiadiazoles containing a 2,6-di-tert-butylphenol substituent were prepared and evaluated as dual inhibitors of 5-lipoxygenaseand cyclooxygenasein rat basophilic leukemia (RBL-1) cells. Several of these compounds show oral efficacy in the rat carageenan footpad edema (CFE) and mycobacterium footpad edema (MFE) antiinflammatory models, without concomitant gastric ulceration. Structure-activity relationships are discussed. The best compounds (ID40values in MFE of 3-8 mg/kg PO) contain guanidine-derived substituents on the heterocyclic ring. Many currently marketed nonsteroidal antiinflammatory drugs (NSAIDs) are inhibitors of the cyclooxygenase enzyme associated with metabolism of cellular arachidonic acide2 This mechanism is thought to be primarily responsible for the analgesic and antiinflammatory properties of NSAIDs, through the inhibition of prostaglandin biosynthesis.3 However,cyclooxygenaseinhibition has also been associated with the nephrotoxicity and gasotrintestinal side effects characteristic of NSAIDsS4 Recent evidence suggests that increased production of leukotriene products through the 5-lipoxygenaseenzyme pathway can also contribute to NSAID-induced side effect^.^ In addition, certain 5-lipoxygenase products exhibit proinflammatory and chemotactic properties.6 Thus, a novel dual inhibitor of the cyclooxygenase (CO)/B-lipoxygenase (5-LO) enzyme pathways holds promise as an antiinflammatory agent with an improved efficacy and safety profile. One type of dual C0/5-L0 inhibitor that has been extensively studied includes derivatives of 2,6-di-tertbutylphenol. These phenolic compounds frequently contain a heterocyclic ring linked by a carbon or heteroatom chain to the 4-position of the phenol ring.7 In some cases: a heterocyclic ring is directly attached to the phenol 4-position. We previously reportedg the antiinflammatory activity of C1-986 (l),a dual inhibitor comprised of the di-tertbutylphenol moiety linked to a 1,3,4-thiadiazolering. We + Department of Chemistry.
t Department of Immunopathology. (1)Presented in part at the 13th International Congressof Heterocyclic
Chemistry, August, 1991, Corvallis, OR. (2) Lombardino, J. G. Nonsteroidal Antiinflammatory Drugs;WileyInterscience, John Wiley & Sons: New York, 1985. (3) Vane, J. R. Inhibition of Prostaglandin Synthesis as a Mechanism of Action for Aspirin-like Drugs. Nature (New Biol.) 1971,231,232-235. (4) (a) Robert, A. Antisecretory, Antiulcer, Cytoprotective and Diarrheogenic Properties of Prostaglandins. Adv. Prostaglandin Thromboxane Res. 1976,2, 507-520. (b) Peskar, B. M. On the Synthesis of Prostaglandins by Human Gastric Mucosa and ita Modification by Drugs. Biochem. Biophys. Acta. 1977,487, 307-314. (5) (a) Rainsford, K. D. Structural Damage and Changes in Eicosanoid Metabolites in the Gastric Mucosa of Rats and Pigs Induced by Antiinflammatory Drugs of Varying Ulcerogenicity. Int. J. Tissue React. 1986, 8, 1-14. (b) Peskar, B. M.; Klein, A.; Pyras, F.; Muller, M. K. Gastrointestinal Toxicity. Role of Prostaglandins and Leukotrienes. Med. Toxicol. 1986 1 (Suppl. l), 39-43. (c) Guslandi, M. Gastric Effects of Leukotrienes. Prostaglandins, Leukotrienes Med. 1987,26, 203-208. (6) (a) Samuelsson, B.; Borgeat, P.; Hammarstrom, S.; Murphy, R. C. Leukotrienes: A New Group of Biologically Active Compounds. Ado. Prostaglandin Thromboxane Res. 1980, 6, 1-18. (b) Samuelsson, B. Leukotrienes and other Lipoxygenase Products. Prog. Lipid Res. 1986, 25, 13-18.
now report the synthesis and pharmacological properties of a series of 1,2,4-oxadiazolesand 1,2,4-thiadiazoles 2. Many of these compounds are potent inhibitors of both 5-LO and CO activity as measured in rat basophilic leukemia (RBL-1)cells. Severalcompounds are also orally active in animal models of inflammation.
x -1
CI-986
-2
X-N.0 Y
-
N,O,S
Chemistry A series of 3-aryl-1,2,4-oxadiazoleswere prepared from nitrile 31° (Scheme I), after conversion to a phenolprotected amidoxime 5. Acylation of 5 and cyclization of the resulting intermediates yielded analogs 6-8. Oxadiazolone 8 was converted to thione 9 through the imino (7) (a) Moore, G. G. I.; Swingle, K. F. 2,6-Di-tert-butyl-4-(2’-thenoyl)phenol (R-830): A Novel Nonsteroidal Anti-inflammatory Agent With Antioxidant Properties. Agents Actions 1982,12,674-683. (b) E-5110. Drugs Future 1989,14,307-310. (c) Lazer, E. S.; Wong, H.-C.; Possanza, G. J.; Graham, A. G.; Farina, P. R. Antiinflammatory 2,6-Di-tert-butyl4-(2-arylethenyl)phenols.J.Med. Chem. 1989,32,100-104. (d)Hidaka, T.; Hosoe, K.; Ariki, Y.;Takeo, K.; Yamashita, T.; Kataumi, I.; Kondo, H.; Yamashita, K.; Watanabe, K. Pharmacological Properties of a New Anti-hilammatory Compound,a-(3,5Di-tert-butyl-ene)y-butyrolactone (KME-4), and ita Inhibitory Effects on Prostaglandin Synthetase and 5-Lipoxygenase. Jpn. J.Pharmacol. 1984,36,77-85. (e) Panetta, J. A. 5-[3,5-Bis(l,l-dimethylethyl)-4-hydrox~henyl]methyl4-thiazolidinones for Treatment of Inflammation and Ischemia. Eur. Patent Appl. EP 211670,1987. (f)Flynn, D. L.; Belliotti, T. R.; Boctor, A. M.; Connor, D. T.; Kostlan, C. R.; Nies, D. E.; Ortwine, D. F.; Schrier, D. J.;Sircar, J. C. Styrylpyrazoles,Styryliixazoles,and Styryliaothiazoles. Novel 5-Lipoxygenase and Cyclooxygenase Inhibitors. J. Med. Chem. 1991,34,51&525. (g) Kataumi, I.; Kondo, H.; Fuse, Y.; Yamaehita, K.; Hidaka, T.; Hosoe, K.; Takeo, K.; Yamashita, T.; Watanabe, K. Studies on Styrene Derivatives. 11. Synthesis and Antiinflammatory Activity of 3,5Di-tert-buty1-4-hydroxyatyrenes. Chem.Pharm. Bull. 1986,34,161+ 1627. (8)(a) Bartlett, R. R.; Gebert, U.; Kerekjarto, B.; Schleyerbach, R.; Thorwart, W.; Weithmann, K. U. Substituted 3-Phenyl-7H-Thiazolo(3,2-b)(1,2,4)triazin-7-ones as Antiinflammatory Agenta With Immune modulating Properties. Drugs Ezp. Clin. Res. 1989, 15, 521-526. (b) Isomura, Y.;Sakamoto, S.;Ito,N.; Homma, H.; Abe,T.; Kubo, K. Synthesis and Anti-inflammatory Activity of 2,6-Di-tert-butylphenolswith a Heterocyclic Group at the 4-Position. 111. Chem. Pharm. Bull. 1984,32, Kazuyuki, K.; Michio, 152-165 (plus Parta I and 11). (c) Takanori, 0.; T.; Tomonori, I.; Yukihiro, Y. Preparation of (Hydroxypheny1)pyrazolo[3,4-blpyridines as Drugs. Eur. Patent Appl. EP 254241, 1988.
0 1992 American Chemical Society
3692 Journal of Medicinal Chemistry, 1992, Vol. 35, No. 20
Scheme I a
Unangst et al.
Scheme I1 a
%
% %
I
R1 -CH
=NOH
19
la
4
R Ri = H
O
g
a Reagents: (a) NCS; (b) guanidine; (c) (1)dicyanodiamide; (2) MeS03H.
Scheme I11 a EM.
w - 0 4
a Reagents (a) MEMCl, Et3N; (b) HzNOH; (c) (1)AcC1, Et3N; (2) xylene, 125 "C; (3) ZnBrz; (d) (1)ClCHZCOCl, Et3N; (2)MeZNH; (3) HCI; (e) (1)ClCOZEt, Et3N; (2) toluene, 110 OC; (3) ZnBrz; (0 (1) POC13, pyridine; (2) thiourea.
Ri-C *NH
A
NH R1-C: NHCN
b
chloride. Additional 3-aryl derivatives were also prepared from oxime 10'0 (Scheme 11). Chlorination of 10 formed imidoylchloride 11,and cyclization11J2of 11 withguanidine and dicyanodiamide yielded oxadiazoles 12 and 13, respectively. Several 5-aryloxadiazoles were prepared from imidate 14loJ3(Scheme 111) after conversion to anN-cyanoamidine 15.14 Cyclization of 15 with hydroxylamine yielded aminooxadiazole 16, and elaboration of the 3-amino function of 16 provided analogs 17-20. Additional 5-aryloxadiazoles 22-26 were obtained (Scheme IV) by condensation of amidoximes with acid 21,followed by thermal cyclization and reaction a t the oxadiazole 3-position substituent. (9) (a) Schrier, D. J.; Baragi, V. M.; Connor, D. T.; Dyer, R. D.; Jordan, J. H.; Leach, M. E.; Mullican, M. D.; Okonkwo, G. C. N.; Conroy, M. C. The Antiinflammatory Effects of C1-986,5-[3,5-bis(l,l-dimethylethyl)4-hydroxyphenyll-1,3,4-thiadiazole-2(3H)-thione choline salt, a Novel Inhibitor of Arachidonic Acid Metabolism. J.Cell Biochem. 1991,Suppl. 15 (Part E), 175. (b) Dyer, R. D.; Kennedy, J.; Bornemeier, D.; Egloff, A. M.; Adamchak, M.; Chung, F.4.; Mullican, M.; Connor, D.; Schrier, D. J. Biochemical Pharmacology of C1-986, a Novel Inhibitor of Arachidonic Acid Metabolism. J. Cell Biochem. 1991, Suppl. 15 (Part E), 171. (10) Cohen, L. A. Electronic Control of Steric Hindrance in Hindered Phenols. J. Org. Chem. 1967,22, 1333-1335. (11)Eloy, F.; Lenaers, R. Synthdse d'Aminooxadiazoles-1,2,4.Helu. Chim.Acta 1966,49, 1430-1432. (12) Lenaers, R.; Eloy, F. Etude de Quelquea Rdactions des Chlorues d' Acides Hydroxyamiques. Prdparation dOxediazoles-1,2,4 Disubstitut& Helv. Chim.Acta 1963,46, 1067-1073. (13) Mtiller, E.; Rieker, A.; Mayer, R.; Scheffler, K. Dehydrierung Sterisch Behinderter Phenole Unter Bildung 'Einfacher" Dissoziabler Chinoliither. Justus Liebigs Ann. Chem. 1961,645,36-52. (14) Huffman, K. R.; Schaefer, F. C. Preparation and Reactions of N-Cyanoamidines. J. Org. Chem. 1963,28, 1812-1816.
/
J';
Reagents: (a) HzNCN, (b)HzNOH, pyridine; (c) acetic formic anhydride; (d) AczO; (e) HC(0Et)s; (0HCHO, NaBHsCN.
Cyclization of an in situ-generated nitrile sulfide16J6with various dipolarophiles was used to prepare a series of 3-aryl1,2,4-thiadiazoles. An intermediate oxathiazole 2817waa prepared (Scheme V) from amide 27. Thermolysis of 28 and trapping of the generated nitrile sulfide with tosyl (15) Paton, R. M. The Chemistry of Nitrile Sulphides. Chem. SOC. Rev. 1989,18, 33-52. (16) Howe, R. K.; Franz, J. E. Nitrile Sulfides. Synthesis of 1,2,4Thiadiazoles. J. Org. Chem. 1974,39, 962-964. (17) Ravichandran, R. Substituted 1,3,4-0xathiazol-2-oneStabilizers. US.Patent 4724246, 1988.
Dual 5-Liporygenase and Cyclooxygenase Inhibitors
Journal of Medicinal Chemistry, 1992, Vol. 35, No. 20 3693
Scheme IV a
Scheme VI a
.,+;i, 28
0 -N
0 -N
t Rl+?;koH
/
Re
a r
a
E 3
Me
Me
WHCI -(CH2)4-
26 Reagents: (a) (1) acetamidoxime, DCC; (2) xylene, 125 OC; (b) (2) toluene, 110 OC (c)(1) RzRaNH, (1) 2-~hloroacetamidoxime,DCC; (2) HCl. a
Scheme V
28
29
\
/ P N W 3H C N M t W
32
I
h=HO&
NH
e
NHf,NH.L+a NH
33
"p"' NH
\ R i + i k A
39 4Q Reagents: (a) EtOzCCN, dichlorobenzene, 165 OC; (b)NaBH,; (c)(1) phthalimide, DEAD (2) hydrazine;(3) HCI; (d) (1) MeSOZCI; (2) MeZNH; (3) HC1. a
cyanoformate. Ester reduction of 37 provided carbinol 38, which was converted to the primary amine 39 under Mitsunobu'* conditions, or the tertiary amine 40 by mesylate displacement.
a
P
R1"LZ2
s
*Ha
Rj+-J
NHCNMeR6
II
-Rs
NH
35H
3Bb
aReagents: (a) ClCOSCl, toluene, 110 OC; (b) tosyl cyanide, dichlorobenzene,l65 "C; (c) (1) RdH; (2) HCl or choline; (d) (1) HZNC(-NH)SMe; (2) HCI; (e) (1) RsMeNH (2) HC1.
cyanide yielded 29, a key intermediate with a labile tosyl substituent in the thiadiazole 5-position. Displacement of the tosyl group with various amines provided compounds 30-34. Guanidino derivatives 35 and 36 were obtained by amine displacement of thiourea 34. An additional thiadiazole intermediate 37 was prepared (Scheme VI) by thermolysis of 28 in the presence of ethyl
Results and Discussion Pharmacology and metabolism studies with 1indicated (1) low bioavailability due to rapid metabolism, (2) generally good dual inhibitor activity when the sulfur was replaced with amino substituents, and (3) improved in vivo activity with analogs capable of salt f0rmati0n.l~ Earlier work in a number of related chemical series demonstrated the desirability of maintaining the 4-hydroxy-di-tert-butyl substructure.7c~f120 With this information as a guide, we prepared a series of 1,2,4-oxadiazoles and 1,2,4-thiadiazoleswith emphasison amino Substituents in the 3- or 5-position. Our goal was to find a balanced dual inhibitor with good antiinflammatory activity and a low potential for ulcerogenicity. Compounds were evaluated for dual inhibitor activity by the inhibition of formation of LTB4 or PGFk in rat basophilic leukemia (RBL-1) cells. Those compounds found to be dual inhibitors (IC60 values 110 pM in both assays) were then evaluated in several animal models of inflammation. Compounds that were predominantly cyclooxygenase inhibitors (arbitrarily those with a selectivity of CO vs 5-LO inhibition 115) were not pursued further, since such a profile is characteristic of many NSAIDs. Our initial efficacy model was the carrageenan footpad edema test (CFE).This acute model serves to demonstrate (18) Mitsunobu, 0.The Use of Diethyl Azodicarboxylateand Triphenylphosphine in Synthesis and Transformation of Natural Products. Synthesis 1981, 1-28.
(19) Unpublished results.
(20) Katsumi, I.; Kondo, H.; Yamaahita, K.; Hidaka, T.; Hoeoe, K.; Yamashita, T.;Watanabe,K. StudiesonStyreneDerivatives. I. Syntheaia and AntiinflammatoryActivities of a-Benzylidene-y-butyrolactone Derivatives. Chem. Pharm. Bull. 1986,34, 121-129.
3694 J o u r n a l of Medicinal Chemistry, 1992, Vol. 35, No. 20 Table I. In Vitro Biochemistry of 1,2,4-0xadiazoles and 1,2,4-Thiadiazoles
Unangst e t al. Table 11. Antiinflammatory Activity of 1,2,4-Oxadiazoles and 1,2,4-Thiadiazoles
%
Y
no.
X
6 7 8 9 12 13 16 17 18 19 20 22 23 24 25 26
N O M e N 0 CHZNMez-HCl N 0 O(OH) N 0 S(SH) N O NHz N O NHCNHNHz.MeS03H O N NH, O N NHCHO O N NHCOMe O N NCHOEt O N NMez O N Me O N CHzCl O N CH2NHMe O N CHzNMeyHCI O N
2
CH*N3
29 30 31 32 33 34 35 36 37 39 40 1
N N N N N N N N N N
S S S S S S S S S S
NH2 NHCN-choline NHCNHNHTHCI NHCNHMe-HC1 NHCNHSMe.HC1 NHCNHNHMe-HCI NHCNHNMerHCl COzEt CHzNHyHCl CH2NMezaHCl
KME-4 sodium meclofenamate
CFEa % inhib i SEM a t dose in mg/kg PO
IC501 /JM" 5-LO CO 2.3 7.7 Nb 3.4 2.5 1.7 3.6 N N 1.5 3.3 0.78 N 6.8 N
0.30 0.73 4.7 0.050 3.0 0.67 1.9 N N 7.2 88' 0.46 0.10 78' 0.45 N
N
N
0.33 1.9 0.14 N 1.2 0.37 72' 91' 2.6 N 2.8 2.5 24.0
2.2 0.011 1.6 N 0.17 4.4 N N 0.087 N 0.80 0.15 0.10
N
I C ratio: ~ 5-L0/CO 7.7 10.5 68 0.83 2.5 1.9 0.21 7.2 7.8 15
0.15 173 0.088 7.1 0.084 30 3.5 17 240
Calculated as the concentration of test compound causing 50% inhibition of LTBd (5-LO) or PGFz. (CO) formation. The standard errors average 11% of the values shown for 5-LO and 8% for CO. Inactive (N) is defined as
