J . Med. Chem. 1990,33,2437-2451 were sacrificed in groups of five animals. The brain of each animal was immediately excised, and the striatum and cerebellum were dissected over an ice-cold plate.@ A blood sample was obtained via cardiac puncture immediately preceeding decapitation. The femur was also dissected from each test animal following sacrifice. The tissue samples were weighed, and the radioactivity content assayed by counting in a NaI(Tl) well-type y scintillation counter. The results were calculated in terms of percent injected dose per (68) Glowinsky, J.; Iverson, L. L. J. Neurochem. 1966, 13, 655. (69) Henne, A. L.; Stewart, J. J. J . Am. Chem. SOC.1955, 77,1901.
2437
gram of tissue by comparison of the data to that of a standard sample of the injectate.
Acknowledgment. The authors are grateful to C. J. Mathias and D. Robbins for assistance with the animal biodistribution experiments. We also thank Astra Lakemedel AB, Sodertajle, Sweden for the gift of raclopride. This work was supported by NIH FIRST Award NS-26788, NIH Grant HL-13851, and by the Animal Resources Program, University of Washington Regional Primate Center Grant RR00166.
A Novel Series of Selective Leukotriene Antagonists: Exploration and Optimization of the Acidic Region in 1,6-Disubstituted Indoles and Indazoles’ Ying K. Yee,* Peter R. Bernstein,*i* Edward J. Adams, Frederick J. Brown, Laura A. Cronk, Kevin C. Hebbel, Edward P. Vacek, Robert D. Krell,’ and David W. Snyder’*# Departments of Medicinal Chemistry and Pharmacology, ICI Pharmaceuticals Group, A Business Unit of ICI Americas Incorporated, Wilmington, Delaware 19897. Received October 16, 1989 A systematic structure-activity exploration of the carboxylic acid region in a series of indole- or indazole-derived leukotriene antagonists 1 led to several discoveries. Use of the 3-methoxy-p-tolyl fragment (illustrated in acid 1) for connecting the indole and the acidic site provides the most potent carboxylic acids 1, tetrazoles 20, and aryl sulfonimides 21 (Figure 1). The aryl sulfonimides are 5-500 times more potent (in vitro and/or in vivo) than the corresponding carboxylic acids 1. The o-tolyl sulfonimides such as 114 (Table VII) show greater oral potency than the phenyl sulfonimides a t a given level of in vitro activity. Acidic keto sulfone derivatives 10 (Nu = CH(C02CH3)S02Ph)mimic the activity of the sulfonimides.
The peptidoleukotrienes (LTC,, LTD,, and LTEJ have been the focus of intense research efforts for the past 10 years,2following the discovery by Samuel~son,~ that the leukotrienes were the active components of the “slow reacting substance of anaphylaxis” (SRS-A). SRS-A is believed to be an important biological mediator in several disorders, especially human allergic diseases. A major pharmaceutical goal has been the discovery and development of novel, selective antagonists of the leukotrienes as potential therapeutic agents for the treatment of asthma. An earlier paper from these laboratories described the discovery of a novel series of indole and indazole carboxylic acids 1 which are leukotriene antagonists., Herein we describe the detailed exploration of the carboxylic acid region in this series of antagonists. These efforts led to novel aryl sulfonimides 21 which show increased potency both in vitro (pKBup to 10.9 against LTE, on guinea pig t r a ~ h e aand ) ~ in vivo (oral ED,, < 1 mg/kg against LTD, induced labored abdominal breathing in the guinea pig) (Figure l).5 Chemistry General Routes and Syntheses of the Aryl Acids 8. The general synthetic routes to the indole/indazole carboxylic acids 8, sulfonimides 10 (Nu = -NHSO,R”) and many of the acid mimics 36 listed in Tables I, 11, and I11 are presented in Schemes I and 11. Our first route (La, Scheme I) began with 6-aminoindazole 2a or with catalytic hydrogenation of 6-nitroindole 32b to afford 6-aminoindole 2b. The amines 2 were acylated by treatment either with a carboxylic acid or water soluble carbodiimide (WSCDI, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimidehydrochloride) and with an acid chloride and triethylamine.’ These reactions provided amides and urethanes 3 which Department of Pharmacology. * T owhom reprint requests should be addressed. *Present address: Eli Lilly and Co., Indianapolis, IN.
retained a reactive hydrogen at position N-1’ in the indole/indazole fragment. Therefore, compounds 3 were convenient intermediates for series of acids 8 in which only the acidic region was to be varied (e.g. Tables I and 11). Alkylation of the acylated intermediates 3 to afford esters 4 was achieved by sequential treatment with sodium hydride and halo-ester 7 in dimethylformamide! The halo esters 7 were prepared by bromination of toluate esters?JO Portions of this work have been previously presented: (a) Matassa, V. G.; Bernstein, P. R.; Brown, F. J.; Hesp, B.; Yee, Y. K.; Krell, R. D.; Giles, R. E.; Snyder, D. W. Abstracts of Papers, 193rd National Meeting of the American Chemical Society, Division of Medicinal Chemistry, Denver, CO, April, 1987; American Chemical Society: Washington, DC, 1987; Abstract 87. (b) Yee, Y. K.; Bernstein, P. R.; Brown, F. J.; Matassa, V. G . Ibid. Abstract 88. Chakrin, L. W., Bailey, D. M., Eds. The Leukotrienes, Chemistry and Biology; Academic: Orlando, FL, 1984. Hammarstrom, S.;Murphy, R. C.; Clark, D. A.; Mioskowski, C.; Corey, E. J. Biochem. Biophys. Res. Commun. 1979, 91, 1266. Brown, F. J.; Yee, Y. K.; Cronk, L. A.; Hebbel, K. C.; Snyder, D. W.; Krell, R. D. J . Med. Chem. 1990, 33, 1771. The biological tests are described in the Experimental Section of the text and have been discussed in refs 4 and 10. These synthetic sequences, where the halo ester 7 was methyl 4-(bromomethyl)-3-methoxybenzoate, have been described in ref 4. As exemplified in the Experimental Section in the preparation of tetrazole 80 by the conversion of 5-nitroindole (32b) to 6aminoindole (2b) and its subsequent acylation to 6-hexanamidoindole (3b, R = pentyl). As exemplified in the Experimental Section under acid 42 by conversion of 6-hexanmidoindole (3b, R = pentyl) to ester 4b (R = pentyl, C and D = hydrogen, C02R1is at position C-1 and R1 = methyl). The syntheses of all the benzylic bromides utilized in this paper are described (a) Bernstein, P. R.; Willard, A. K. U S . Patent 4,499,299,1985. (b) Brown, F. J.; Bemstein, P. R.; Yee, Y. K. European Patent Application, Publication Number 0179 619 A l , published April 30, 1986. (c) Reference 10.
0022-2623/90/1833-2437$02.50/00 1990 American Chemical Society
2438 Journal of Medicinal Chemistry, 1990, Vol. 33, No. 9
Yee et ul.
Scheme I
,Ye
4
Tc0ZCH3
a) H2, PdIC, EtOAc: b) RCOzH, DMAP, W S C D I T ~ F - C H Z C Ior ~ RCOCI, Et3N/CH2CI2; c) I. NaH/DMF, li. 0; d) LIOHlmethanol-water; e) for i. NaOH, il. ArCH2Br (1)/ solvent: for KzCO3, ArCH2Br 0 l a c e t o n e .
a
#a X = N, #P. X = CH; R alkyl, alkoxy: C, D = hydrogen, alkyl, alkoxy, halogen; l-(3-dlmethylamlnopropyl)-3~athylcarbodllmide hydrochloride WSCDI Route 1.a Route 1.b
32->2->3->4->0 32->5->6->4->8
Scheme I1
lPab U , k (-Nu
6
=-NHS02Ar)
11 0
8 )WSCDI,
DMAP, NuH/ CHzCIi-THF; b) N,N-dlphsnylcarbamoyl pyridinlum chloride, Et3N/methanol: c) NuH or Nu'/ solvent as In text
#a X=N, #P. X = CH;
R= Alkyl, Alkoxy
Route 2.a p+LQ Route 2.b 1->2->l.Q
Leukotriene
R'SH
glutathione cystelnylgylcine cysteine
c4 04
E4
la,PA=CO&l
'
U , h A = CONHS02Ar R I alkyl, alkoxy, alkylamlno a , u X = N , 1p,aX=CH
Since most of these compounds have a carbonyl group at position 1 we used the illustrated numbering sequence for purposes of discussion
the salt of 6-nitroindazole was made with sodium hydroxide according to the protocol of Granger." This salt was then allowed to react with halo ester 7 in acetone.12 The indazole ester 5a produced in this alkylation was accompanied by the N-2' alkylated analogue and purification usually required chromatography. In contrast, 6nitroindole 32b was cleanly N-alkylated to afford esters 5b by treatment with potassium carbonate and the appropriate halo ester 7 in refluxing acetone.12 Catalytic reduction of the nitro group in esters 5 with hydrogen and palladium on carbon afforded amino esters 6.12 The amino esters 6 were convenient intermediates for series of acids
Figure 1.
In the case of the N-1' alkylated indazole esters 4a it was usually necessary to remove a minor amount of the N-2' alkylated esters via chromatography. An alternate route (1.b) to esters 4 is also shown in Scheme I. In this approach, the first step was alkylation of 6-nitroindazole 32a or 6-nitroindole 32b with halo ester 7 to afford nitro ester 5. In particular, for the indazoles, ~~~
~
(10) Brown, F. J.; Bernstein, P. R.; Cronk, L. A.; Dosset, D. L.; Hebbel, K. C.; Maduskuie, T. P.; Shapiro, H. S.; Vacek, E. P.; Yee, Y. K.; Willard, A. K.; Krell, R. D.; Snyder, D. W. J . Med. Chem. 1989, 32, 807.
(11) Granger, R.; Koeberle, J.; Hao-Dong, L.; Boucard, M.; Ciroux, J. J.; Mizoule, J.; Yavordis, D. Chim. Ther. 1970, 5, 24. (Al-
though this paper reported the use of "dilute sodium hydroxide", we found that formation of the sodium salt of 6-n1troindazole required 6 N NaOH.) (12) This general reaction has not been exemplified in the Experimental Section. It is very similar to the corresponding sequence that uses halo nitrile 19 instead of halo ester 7 and which is included in the Experimental Section in the preparations of tetrazoles 80 and 81. Furthermore this general sequence has been reported in full detail, along with the structure proof for the N-1' versus N-2' products, in ref 4 for sequences in which halo ester 7 is methyl 4-(bromomethyl)-3methoxybenzoate.
Journal of Medicinal Chemistry, 1990, Vol. 33, No. 9 2439
Indole and Indazole Acid Leukotriene Antagonists
Scheme 111
a
n s o z c '
BCH2 c
a) NBSICCI,:
Y=OH
fi
Y = NHz Y I NHCOPh
cu
11
I
12
a
(R=l-ethylpentyl), NaH
*L5 3k
(R=l-ethylpentyl), Nan
b) Ethanol-water: c) NHJ/ solvent: d) benzoyl chloride
*Lz
1
Route 3.a 11->12->75 Route 3.b 11->13->14-,77
8 in which we wanted to vary the amide/urethane group (Rin 36, Table 111). Acylation of amino esters 6, as previously described for amines 2, produced the esters 4. Hydrolysis of the esters 4 with aqueous lithium hydroxide provided the corresponding carboxylic acids 8.13 Preparation of tetrazole carboxylic acid 55 required an additional step. It was synthesized from cyano acid 53 by reaction with sodium azide and triethylamine hydrochloride in DMF.'* Aryl Acid Mimics, Excluding Tetrazoles (Compounds in Tables 11and 111). The sulfonimides21 were formed (see Scheme 11) from the appropriate sulfonamide and carboxylic acid 1. This conversion could be accomplished directly by using WSCDI as the coupling agent (method 2.a),15 or it also be done via the intermediacy of a mixed carbamic anhydride 9 (method 2.b).16 Carbamic anhydride 9 was formed by reaction of carboxylic acid 1 and (N,N-diphenylcarbamoy1)pyridiniumchloride" in methanolic base.l8 To prevent formation of the corresponding methyl ester 4 it was necessary to isolate anhydride 9 after a short reaction period, either by filtration or by extractive work up. The carbamic anhydride 9 was also useful as a precursor for several other acid mimics (listed in Table 11). In particular, reaction of anhydride 9b (R = 1-ethylpentyl) and the following nucleophiles (in the indicated solvent), afforded the indicated acid mimic (designated by their compound number): lithiomethyl(phenylsulfony1)acetate (THF), 59; lithio(phenylsulfony1)acetonitrile (THF), 60; sodium 2-aminobenzoate (DMF), 61; sodium glycinate (DMSO), 62; 5-aminotetrazole (DMF), 63; hydroxylamine (methanol-DMF), 64; benzenesulfinamide (DMF), 65; and lithiomethyl phenyl sulfone (THF), 72.19 The sulfonic acid 75 and the transposed sulfonimide 77 analogues were both prepared from p-toluenesulfonyl chloride as outlined in Scheme 111. Reaction of p As exemplified in the Experimental Section by the preparation of carboxylic acid 42 from ester 4b (R = I-ethylpentyl, C and D = hydrogen, C02R, is at position C-1 and R, = methyl). Finnegan, W. G.; Henry, R. A.; Lofquist, R. J. J. Am. Chem. SOC. 1958,80,3908. Aa exemplified in the Experimental Section by the preparation of sulfonimide 92 by the coupling of o-toluenesulfonamide with carboxylic acid l a (R = cyclopentyloxy). As exemplified in the Experimental Section in the preparation of sulfonimide 58 by the conversion of carboxylic acid l b (R = 1-ethylpentyl)to anhydride 9b (R = 1-ethylpentyl)and its subsequent coupling with benzenesulfonamide. Shephard, K. L.; Halczenko, W. J. Heterocycl. Chem. 1979,16, 321. As exemplified in the Experimental Section by the preparation of sulfonimide 58 by the conversion of carboxylic acid lb (R = 1-ethylpentyl) to anhydride 9b (R = I-ethylpentyl). As exemplified in the Experimental Section by the preparation of acid mimics 59, 60,65,and 72.
Scheme IV
toluenesulfonyl chloride with N-bromosuccinimide followed by solvolysis in aqueous ethanol according to the protocol of BlangeyZ0afforded 4-(bromomethy1)benzenesulfonic acid (12). Treatment of the intermediate 4(bromomethy1)benzenesulfonylchloride (1I) with ammonia afforded bromo sulfonamide 13 which was further converted to sulfonimide 14 by acylation with benzoyl chloride. Alkylation of indole 3b (R = 1-ethylpentyl) by sequential treatment with sodium hydride and either bromide 14 (route 3.b) or bromide 12 (route 3.a) afforded 77 (37%) and the sodium salt of sulfonic acid 75 (20%),respectively. It was necessary to isolate 75 as the sodium salt because the sulfonic acid rapidly decomposed after isolation.21 The preparation of sulfonamide 73 from nitrile 15aZ2is illustrated in Scheme IV. Reduction of nitrile 15a with borane-tetrahydrofuran and acidic workup afforded amine hydrochloride 29 which was converted to sulfonamide 30 by treatment with benzenesulfonyl chloride and 2,6lutidine in DMF. Catalytic reduction of nitro sulfonamide 30 with hydrogen and platinum black gave amine sulfonamide 31 which upon treatment with cyclopentyl chloroformate gave 73. Aryl Tetrazoles. The general syntheses of the aryl tetrazoles 20 (R = alkyl or alkoxy) is given in Scheme V. The tetrazole amides 20 (R = alkyl) were made via route 5.a. This route began with alkylation of indoles/indazoles 3, by treatment with sodium hydride and 4-(bromomethyl)-3-methoxybenzonitrilelggbin dimethylformamide, to afford nitriles 17F3 These nitriles were then converted Blangey, L.; Fierz-David, H. E.; Stamm, G. Helv. Chim. Acta 1942,25, 1162. The decomposition presumably occurs since indoles are unstable to exposure to strong acids, see page 7 in: Sundberg, R. J. The Chemistry of Indoles; Academic Press: New York, NY, 1970. For preparation of nitrile Ea, see Scheme V and the discussion on the preparation of aryl tetrazoles. As exemplified in the Experimental Section in the preparation of tetrazole 80, part d, by the conversion of 6-hexanamidoindole 3b (R = pentyl) to nitrile 17b (R = pentyl).
2440 Journal of Medicinal Chemistry, 1990, Vol. 33, No. 9
Yee et al.
Scheme V
C
a) i. NaH, DMF, ii. 4-bromomethyl-3-methoxybenzonitrile u9); b) NaN3-Et3NHCI/NMP; c) for 3&, i. NaOH, ii. (19); f o r m , c) == a); d) PdlC, Hz; e) RCOZH, WSCDI, DMAP/ THF or RCOCI, Et3N/CH2CI,.
#aX = N, #p X = CH; Route 5.a Route 5.b
R = alkyl, alkoxy
&>=->a
~ - > ~ - > f i - > ~ - > ~
to tetrazole amides 20 (R = alkyl) by reaction with sodium azide and triethylamine hydrochloride in N-methylpyrrolidone at 150 0C.24*25The analogous cyanourethanes (17, R = alkoxy) decomposed under either the standard14 or the alternatez4tetrazole forming conditions. Because of this problem, the tetrazole urethanes 20 (R = alkoxy) were prepared via route 5.b. In this route 6-nitroindole 32b or 6-nitroindazole 32a was alkylated with nitrile 19.26 The conditions utilized were identical with that described above in route l.b, in the section General Routes and Syntheses of the Aryl Acids 8, for alkylation of 32 with halo ester 7. The product nitronitriles 15 were converted to nitrotetrazoles 16 by reaction with sodium azide and triethylamine hydrochloride in N-methylpyrrolidone a t 150 0C.z4,z7 Catalytic reduction of nitrotetrazoles 16 with hydrogen and palladium on carbon, as a solution in methanolic base, produced the amines 18.2s These amines were directly acylated with the appropriate alkyl chloroformates to afford the urethane tetrazoles 20 ( R = alk-
Results and Discussion During the initial exploration of this series of leukotriene antagonists only three variants in the benzoic acid region (24) Bernstein, P. R.; Vacek, E. P. Synthesis 1987,1133. (25) As exemplified in the Experimental Section by the preparation of ktrazole 80 by the conversion of nitrile 17b (R = pentyl) to tetrazole 80. (26) As exemplified in the Experimental Section in the preparation of tetrazole 81,part a, by the alkylation of 6-nitroindole 32b to afford nitrile 15b. (27) As exemplified in the Experimental Section in the preparation of tetrazole 81,part b, by the conversion of nitrile 15b to nitrotetrazole 16b. (28) As exemplified in the Experimental Section in the preparation of tetrazole 81,part c, by the conversion of nitrotetrazole 16b to aminotetrazole 18b. (29) As exemplified in the Experimental Section by the preparation of tetrazole 81 by the acylation of aminotetrazole 18b with butyl chloroformate.
I
W 6C O , "
26 Figure 2. Hydroxyacetophenone-based antagonists.
had been e ~ p l o r e d .These ~ were the 3-methoxy-p-toluic acid derivative 1 (Figure 1) and the less potent o- or ptoluic acid analogues (not illustrated, carboxyl group a t positions 3 and 1,respectively). Acid 1 had been prepared because of a perceived correlation between the original oand p-toluic acids and a series of hydroxyacetophenone (HAP) derived antagonists 26 which were prepared in these laboratories (see Figure 2).4J0 In the HAP series the 3-methoxy group was important for optimal activity.'O It was unknown how well the structure-activity relationships, of the HAP and indole/indazole series would correlate. To determine if the 3-methoxy-p-toluic acid fragment was also optimal in this series we chose to explore the indoles (lb). We initially focused on substituted p and m-toluic acids. Concurrent with these studies, exploration of the amide region (R in acids 1) was resulting in significant increases in p ~ t e n c y .Because ~ of this, most of our early acid-region studies were done on a series in which the original hexanamide group in 1 (R = pentyl) was replaced with the more potent 2-ethylhexanamide group (R = 1-ethylpentyl). As our exploration of the acid-region progressed better amide derivatives were in~orporated.~ The compounds were tested in several in vitro and in vivo assay^.^ We originally used an in vitro assay that measured inhibition of an LTE,-induced contraction in guinea pig tracheal spirals.30 The selectivity of some of
Journal of Medicinal Chemistry, 1990, Vol. 33, No. 9 2441
Indole and Indarole Acid Leukotriene Antagonists Table I. Toluic Acid Variations
6
34
test concn, % antagonism % lo-' M of LTE4' mp, 'C microanalysis yieldb 1 33 100 234-5 Cz5H30N204.0.4Hz0 ref 4 10 59 42 1 100 44 208-10 C24Hp8N203*0.25HpO 46 43 3-Me0 5-Me0 1 10 63 274-5 dec CzaH32N205c 83 44 3-Me 1 100 91 239-40 C25H30NZ03 91 33 21 1 100 44 222-32 dec CuHZ7C1N2O3 45 45 3-C1 46 3-F 1 100 86 2 15-6.5 C24H27FN203 96 1 10 15 189-90 C25H30N204 69 47 2-Me0 48 2 100 31 216-8 C24H,NpO3*0.25H20 98 2 100 28 171-4 C25H30N204 69 49 1-Me0 50 3-Me0 2 100 38 200-1 C26H30N204 64 51 2-Br 1 33 33 186-7 C24H27BrN203 43 1 100 83 197-9 C28H36NZ04 70 52 3-Bu0 33 44 53 3-O(CHZ),CN 1 100 84 175-6 82 C28H33N304 33 33 1 100 18NSd 167-72 C33H38N205 98 54 3-O(CHp)3Ph 1 10 32 187-8 C28H34N604 5d 55 3-O(CHZ),Tete a Percent antagonism of 8 nM of LTE, induced contraction of guinea pig tracheal spirals by antagonists at the indicated test concentration. All tests run on a minimum of four tracheal spirals. Reproducibility was, in general, I20% of the mean. Results are statistically significant ( p < 0.05) from control unless otherwise indicated. bYield on ester hydrolysis. CNitrogen: calcd 6.19; found 5.72. dNS = not significant. e Tet = 1H-tetrazol-5-yl. fExperimenta1 included, yield for tetrazole formation. entry 41
C 3-Me0
D
COpH substitution
these compounds was checked in a similar assay in which the LTE, was replaced with the nonspecific spasmogen BaC1,. For compounds which were of greater interest, KB values were determined,3I also by using LTE, and guinea pig tracheal spirals. More recently a LTD4-bindingassay on isolated guinea pig lung membrane was developed by Dr. D. Aharony, in these laboratorie~.~~ Several of these (30) LTE, was used in this assay instead of LTC, or LTD, for the following reasons: Guinea pig trachea contains multiple receptors for the leukotrienes which have different affinities for LTC,, LTD,, and LTE, as described in: (a) Snyder, D. W.; Krell, R. D. J. Pharmacol. Exp. Ther. 1984, 231, 616. (b) Aharony, D.; Catanese, C. A.; Falcon, R. C. J. Pharmacol. Exp. Ther. 1989, 248, 581. In the absence of metabolic inhibitors there is rapid metabolic conversion of LTC, to LTD4 and of LTD, to LTE, in guinea pig tracheal smooth muscle. Therefore if either LTC, or LTD, is used instead of LTE,, which agonist is being inhibited at which receptor will remain unknown, unless metabolic inhibitors are used as described in ref 30a above. We felt it was important to do testing in the presence of only the minimum number of extra drugs. Isolated human airways do not contain this multiplicity of receptors. Furthermore of the receptors in guinea pig lung, the receptors which appear to have the most similar response characteristics to the human airways receptors are the LTE, subtype as described: (c) Buckner, C. K.; Krell, R. D.; Laravuso, R. B.; Coursin, D. B.; Bernstein, P. R.; Will, J. A. J . Pharmacol. Exp. Ther. 1986,237, 558. (31) To make it easier to compare the activity of these compounds over the wide potency range reported in this paper we have reported pKB values in the tables. As described in the Biological Evaluation Procedures section of the Experimental Section these pKB values are all statistically significant (p
