Pergamon
B1OORGANIC & MEDICINAL CHEMISTRY LETTERS
Bioorganic & Medicinal Chemistry Letters 8 (1998) 71-74
5-AMINOMETHYLQUINOXALINE-2,3-DIONES. PART II: N-ARYL DERIVATIVES AS NOVEL NMDA/GLYCINE AND AMPA ANTAGONISTS. Yves P. Auberson', Pierre Acklin, Hans Allgeier, Michel Biollaz, Serge Bischoff, Silvio Ofner, Siem J. Veenstra Novartis Pharma AG, Klybeckstrasse 141, 4002 Basel, Switzerland Received 18 August 1997; accepted 17 November 1997 Abstract: Potent antagonists at the glycine-binding site of NMDA receptors, as well as dual antagonists acting also at AMPA receptors have been identified in a series of 5-arylaminomethylquinoxaline-2,3-diones. A study of the structure-activity relationship of these compounds is reported here. © 1997 Elsevier Science Ltd. All rights reserved.
L-glutamate is the main excitatory neurotransmitter in the brain, acting both at ionotropic and at metabotropic receptors. The overexcitation of several of these receptors has been shown to be involved in the neurodegeneration occuring after cerebral ischemia la, and to play a role in triggering seizures associated with epilepsy lb. Compounds preventing this excessive stimulation are expected to be of therapeutic interest. Quinoxaline-2,3-diones are well-known antagonists at the glycine-binding site of NMDA receptors 2, and as such show considerable potential as neuroprotective agents after stroke 3, traumatic brain injury, or for the treatment of epilepsy4. Most of the in vitro potent antagonists described in the literatureS, 5 are poorly water-soluble and, except for the quinoxaline-2,3-dione ACEA 10216 and possibly GV1505267, not active in preclinical models of stroke. As a result, very few glycine antagonists have proceeded into clinical development s. During a study of quinoxaline-2,3-diones 9, l a was found to be active in vivo as a mixed antagonist at AMPA receptors and at the glycine-binding site of NMDA receptors. The structure-activity relationship of further 5aminomethylquinoxaline-2,3-diones will be described in this article (series 1-3, R = aryl or cyclohexyl). Figure 1:
O ~
ACEA-1021 [3I-1]DCKA: 10 nM
HO.~ N
GV150526 [3H]DCKA: 7 nM
la [3H]DCKA: 280 nM [3H]AM~A" 330 nM
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RHNb
lb-u X = NO 2 2a-c X = Br 3a,b X = CI
72
]I. P. Auberson et al. / Bioorg. Med. Chem. Lett. 8 (1998) 71-74
Chemistry 5-Methylquinoxaline-2,3-dione 410 was chlorinated on the aromatic ring and protected as its dimethoxy derivative 7 by treatment with PCI5 and sodium methanolate. Benzylic bromination with NBS, followed by alkylation of methyl anthranilate and hydrolysis gave the desired compounds (3a,b) with good yields. Further derivatives were obtained in a similar manner from the 7-bromo and 7-nitro analogues of g9. Carboxylic acids were prepared as their methyl or ethyl ester, which were hydrolyzed by treatment with refluxing 4N HCI. When the ester was desired, the quinoxaline-2,3-dione moiety was selectively deprotected with HBr in acetic acid. Aldehyde 10 was obtained by bromination of 4, oxidation to the aldehyde and nitration. 10 was then coupled to 2- and 3-aminopyridine by reduetive amination, and the desired products (1re, n) obtained after deprotection under acidic conditions.
ROOC 0
I~N~ '°'
~ f,b,c
Br
~N¢.
,O~,
II
,
,
O~ c
,
°"
c,
e~ 3b, 3a,RR=He CHO
,~N
Art-IN,~
Ad-IN.,,,]
O~ 10
N~ 0.~ 1t
'
lm,n
Reagents and conditions: a) PCI5, neat, 160°C, 2h, 60%; b) MeOH, MeONa, reflux, 18h, 98%; c) NBS, AIBN,
CC14, reflux, 24h, 80-87%; d) i: methyl anthranilate, (i-Pr)2NEt, MeCN, reflux, 38%; ii: HBr/AoOH, 16h, 80°C, 99%; e) MeOH, 2N aq. NaOI-I, 80°C, 31%; f) POCI~, reflux, 18h, 96% g) 2-nitropropane, EtONa, 81% h) HNO3, H2SO4, CF3COOH, (CF3CO)20, 0°C, 75%; i) aminopyridine, NaBH3CN, MeOH, 30-37%; j) HBr in AcOH, 50°C, 18h, 73-91%. Results and discussion The parent N-aryi derivative lb showed moderate affinity for the glycine-binding site of NMDA receptors, and was unselective with regard to binding at AMPA receptors. Introduction of a fluorine atom on the aromatic ring had little influence on these affinities (l¢-e). In contrast, functionalization by a carboxylate group in the ortho position of the phenyi ring had a pronounced effect: I f displayed dramatically greater affinities for both binding sites. The meta and para derivatives lg and lh were much weaker. Reduction of the aromatic ring to a cyclohexyl group strongly decreased potency of the ortho (li) but not meta derivatives (lk). Derivatization of the carboxylic acid to an amide (l j) or to an ester (ll) had no beneficial effect.
73
Y. P. Auberson et al. /Bioorg. Med. Chem. Lett. 8 (1998) 71-74
Table 1: In vitro potencies11 of 5-arylaminomethylquinoxaline-2,3-diones and related structures
RNH,~
RNH-,~
RNH.,,~ o
O2N
Br
I;I 2a-¢
RNH
NMDA a (glycine) b
AMPA a
lbc
~,NH
1.4
1.5
10c
1~
~
0.50 + O.17
1.4
lp c
cl
RNH
F
o 3a,b
NMDA a (glycine) b
AMPA a
CNIN~NH
12%
0.38-1-0.1
~ ~N
59%
0.22 + 0.14
ld c
~ " ~
0.72+0.08
1.4
ht c
~
4(P,4
3.1
l ec
F~ ~_
0.75+ 0.24
1.2
lr
s ~v. . xx,~, -"
36%
1.4
If
__[~"Hcoo,
0.05 + 0.02
0.05 + 0.01
lSc
~TN~V~ s
41%
0.19 + 0.03
0%
0.9 _+0.06
Itc
Etooc~..~
0.41 4- 0.3
1.8
1o%
16
lu,
18c
lic
~cc.~
~]~"
25%
0.674- 0.09 2a
250//0
0.65±0.06
0.784-0.22 2c
o.12+o.o20lS±Oo9
[~un
40%
12
COOH
lj c
~NH
2be
EtOOCx.~N~--'T~NH0.344-0.O9
17%
H°°C~N~--.~ NH 0.12± 0.03
1.45
cos~ lk d
.ooc,~,.
21%
11
u,ooc..~,,~
30%
1.3
N~ ~'NH
12%
0.97 4- 0.05
In c
3a
~c:x:x:~M~
25%
0%
a: ICso:1:SEMin p.Mor % inlu'bitionat 1 BM;averageof at leasttwo triplicateexperiments;b) [~I]-(Z)-2-carboxy-4,6dichlomindole-3-(2'ophenyl-2'.carboxy)-ene(MDL-105519)or [~rl]-DCKAbindingassay;c) I-IBrsalt; d) HCI salt. Additional structural variations were obtained by replacement of the phenyl group with heteroaromatic rings. The 2- and 3-aminopyridine (lm,n), 2-aminopyrimidine (1o) and 2-aminopyrazine (lp) derivatives hound to AMPA receptors, but had little or no affinity for the glycine site of NMDA receptors. Compounds possessing a methylene linker between the aromatic ring and the nitrogen atom, as exemplified by lq and lr, were weaker.
74
Y. P. Auberson et al. / Bioorg. Med. Chem. Lett. 8 (1998) 71-74
In a separate series, the phenyl ring was replaced by a thiazole: Is was more potent at AMPA receptors. A satisfactory affinity at the glycine-binding site of NMDA receptors was achieved by addition of an acetic acid side-chain (lu). The selectivity for the glycine-binding site could be further improved by replacing the 7-nitro substituent on the quinoxaline-2,3-dione nucleus with a bromine atom (2¢), although affinity did not increase. The highest potency was observed with the 7-chloro derivative 3b, which displayed a strong affinity for the glycine binding site of NMDA receptors, while thirty-fold weaker at AMPA receptors. Interestingly, the corresponding ester (3a) was inactive in both assays. In conclusion, the study of the 5-arylaminomethylquinoxaline-2,3-diones reported here reveals the potential of these molecules to bind selectively to the glycine-binding site of NMDA receptors or to AMPA receptors. The best affinities were obtained with anthranilic acid as a side-chain (e.g. 10, and selectivity for the glycine-binding site of NMDA receptors achieved when the 7-nitro group was replaced by a chlorine atom (3b). Aeimowledgment: The authors would like to thank C. B6sch, R. B6sch, A. Koblet, D. Kulm, P. Sch~iublin and P. Schmid for their technical assistance. Thanks also to P. Martin and N. Reymann for running the radiofigand binding assays. Referemces and notes:
I. a) Choi, D.W.; Rothman, S.M. Annual Rev. NeuroL 1990 13 171; b) Bradford, H.F. Progress in Neurobiology 1995 47 477. 2. a) Keana, J.F.W.; Kher, S.M., Cai, S.X.; Dinsmore, C.M.; Glenn, A.G.; Guastella, J.; Huang, J..-C.; Ilyin, V., L(i, Y.; Mouser, P.L; Woodward, R.M., Weber, E. J. M e d Chem. 1995 38 4367; b) Nagata, R.; Tanno, N.; Kodo, T., Ae, N., Yamaguchi, H., Nishimura, T., Antoku, F., Tatsuno, T., Kato, T., Tanaka Y.; Nakamura, M. J.. Med Chem. 1994 37 3956; c) Epperson, J.R.; Hewawasam, P.; Mcanwell, N.A.; Boissard, C.G., Gribkoff, V.K.; Post-Munson, D. Bioorg. a n d M e d Chem. Lett. 1993 3 2801. 3. Lccson, P.D.; Iversen, L.L. 3. M e d Chem. 1994 37 4053. 4. McCulloch, J.; Bullock, R., Teasdale, G.M. In Excitatory Amino Acid Antagonists', Meldrum, B., Ed., Blackwell Scientific Publications: Oxford 1991 287. 5. a) Mignani, S., Aloup, J.-C., Barreau, M.; Birraux, G.; Blanchard, J.-C., B6hme, A., Boireau, A.; Damour, D.; Doble, A.; Jimonet, P.; Malgouris, C.; Mary, V., Randle, J.C.R.; Rataud, J., Stutaanan, J.-M. Drugs o f the Future 1995 20 1133. b) Kulagowsld, J.J.; Baker, R.; Curtis, N.R., Lecson, P.D.; Mawer, I.M.; Moseley, A.M., Ridglll, M.P.; Rowley, M., Stansfield, I.; Foster, A.C.; Cn'imwood, S.; Hill, 1LG.; Kemp, J.A., Marshall, G.1L, Syawell, K.L., Trickelbank, M.D. 3. M e d Chem. 1994 37 1402, and rcf. cited therein. 6. a) Woodward, R.M.; Huettner, J.E., Guastdla, J.; Keana, J.F.W.; Weber, E. Mol. Pharmacol. 1995 47 568. b) Warner, D.S.; Martin, H.; Ludwig, P.; McAllister, A., Keana, J.F.W.; Weber, E. J. Cereb. BloodFlow Metab. 1995 15 188. 7. Di Fabio, R.; Capelli, A., Conti, N.; Cugola, A.; Donati, D., Feriani, A.; Gastaldi, P.; G-aviraghi, G., Hewkin, C.T.; Micheli, F.; Missio, A., Mugnaini, M.; Pecunioso, A.; Quaglia, A.M.; Patti, E., Rossi, L., Tedcsco, G., Trist, DG., Reggiani, A. d. M e d Chem. 1997 40 841. 8. Kulagowski, J.J.; Leeson, P.D. Exp. Opin. Ther. Patents 1995 5 1061. 9. Auherson, Y.P., Bischoff, S., Moretti, R.; Schmutz, M., Veenstra, S.J. Bioorg. a n d M e d Chem. Letters, preceeding article. 10. a) St. Clair, R.L., Thibault, T.D. USPatent # 3992378 1976 (CA 86:89890m). 11. a) Honor6, T.; Lauridsen, J.; Krogsgaard-Larsen, P. 3. Neurochem. 1982 38 173, b) Baron, B.M., Siegel, B.W., Harrison, B.L., Gross, R.S., Hawes, C. and Towers, P. 3. Pharmacol. F,xp. Ther. 1996 279 62-68.
