6-Amino quinazolinedione sulfonamides as orally active competitive AMPA receptor antagonists

Article abstract of DOI:10.1016/j.bmcl.2011.12.009

A new set of quinazolinedione sulfonamide derivatives as competitive AMPA receptor antagonist with improved properties compared to 1 is disclosed. By modulating physico-chemical properties, compound 29 was identified with a low ED₅₀ of 5.5 mg/kg in an animal model of anticonvulsant activity after oral dosage.

Full text of DOI:10.1016/j.bmcl.2011.12.009

Bioorganic & Medicinal Chemistry Letters 22 (2012) 996–999
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
6-Amino quinazolinedione sulfonamides as orally active competitive AMPA
receptor antagonists
David Orain a, , Silvio Ofner a, Manuel Koller a, David A. Carcache a, Wolfgang Froestl a, Hans Allgeier a,
⇑
Vittorio Rasetti a, Joachim Nozulak a, Henri Mattes a, Nicolas Soldermann a, Philipp Floersheim a,
Sandrine Desrayaud a, Joerg Kallen b, Kurt Lingenhoehl c, Stephan Urwyler d,
a Novartis Institute for Biomedical Research, Global Discovery Chemistry, Basel CH-4002, Switzerland
b Novartis Institute for Biomedical Research, Center for Proteomic Chemistry, Basel CH-4002, Switzerland
c Novartis Institute for Biomedical Research, Science Operations, Basel CH-4002, Switzerland
d Department of Chemistry and Biochemistry, University of Berne, Berne CH-3000, Switzerland
a r t i c l e i n f o
a b s t r a c t
Article history:
A new set of quinazolinedione sulfonamide derivatives as competitive AMPA receptor antagonist with
improved properties compared to 1 is disclosed. By modulating physico-chemical properties, compound
29 was identified with a low ED50 of 5.5 mg/kg in an animal model of anticonvulsant activity after oral
dosage.
Received 21 October 2011
Revised 30 November 2011
Accepted 1 December 2011
Available online 8 December 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
AMPA receptor antagonist
Quinazoline-2,4-dione sulfonamide
Glutamate receptors
Anticonvulsant
Orally active
Glutamate is the principal excitatory neurotransmitter of the
central nervous system where it acts at both ionotropic and metab-
otropic receptors. Metabotropic glutamate receptors (mGluRs) are
G-protein coupled receptors and, to date, eight subtypes, subdi-
vided in three groups, have been described. Ionotropic glutamate
receptors are classified according to their agonist selectivity into
lamotrigine and topiramate inhibit glutamatergic neurotransmis-
sion, an effect which may contribute to their anticonvulsant activ-
ity.6,7 However, up to now, no AEDs in clinical use exert their
therapeutic effects by selectively interfering with glutamatergic
neurotransmission. There is evidence from various sources that
this mechanism of action is likely to be of therapeutic utility in epi-
lepsy8 and several AMPA receptor antagonists are currently in clin-
ical development as AEDs.9
Recently, we published a new class of competitive AMPA recep-
tor antagonists based on a quinazolinedione heterocycle.10 Aspects
of an X-ray structure of the extracellular domain of an AMPA
receptor construct co-crystallized with 1 were also shown (Fig. 1).
Compound 1 was used as a starting point to develop new com-
petitive AMPA receptor antagonists bearing a N-linked substituent
in position 6 on the core ring. Herein, we present the synthesis and
pharmacological evaluation of this series together with in vivo
data.
N-methyl-D-aspartate (NMDA), kainic acid and a-amino-3-hydro-
xy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors. For
each class of ionotropic glutamate receptors several subunits exist:
GluN1, GluN2A–D, GluN3A–B for NMDA receptors, GluK1–5 for
1
kainate receptors and GluA1–4 for AMPA receptors. Activated
AMPA receptors mediate fast synaptic transmission by producing
a rapidly rising but brief neuronal depolarization caused by influx
of Na+ and depending on their subunit composition Ca2+ ions.2,3
AMPA receptors have been associated to a variety of neurode-
generative and psychiatric diseases such as ischemic brain damage,
amyotrophic lateral sclerosis, schizophrenia and epilepsy.4 Exces-
sive stimulation of the glutamatergic system often plays a role in
triggering seizures associated with epilepsy.5 There is evidence
that, among other mechanisms, the antiepileptic drugs (AEDs)
N
O
H
N
6
N
SO2Me
N
O2N
N
H
O
⇑
7
Corresponding author. Tel.: + 41 61 6961564.
E-mail address: david.orain@novartis.com (D. Orain).
1
Present address.
Figure 1. Structure of 1.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.12.009

D. Orain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 996–999
997
Cl
b
a
F
a
F
b,c
Cl
F3C
NHAc
F3C
NH2
7
F3C
NO2
O
6
F3C
NO2
2
3
CO2H
NHAc
O2N
F3C
O2N
F3C
d,e
O
c
F
F
d
OH
NO2
O
NHAc
9
8
F3C
F3C
NO2
4
5
O
O
H
Scheme 1. Synthesis of intermediate 5. Reagents and conditions: (a) CHCl3, KOtBu,
THF, ꢀ78 °C to 25 °C, 4 h (52%); (b) AgOCOCF3, CH3CN, 75 °C, 7 days (66%); (c)
NaIO4, RuCl3 ꢁ H2O, CCl4/CH3CN/H2O (10:10:15), 60 °C, 3 h (85%); (d) MeOH, H2SO4
concd, 65 °C, 4 days (93%).
N
O2N
F3C
O2N
F3C
f,g,h
N
SO2Me
O
O
N
H
NH2
11
10
As reported, compound 1 was orally inactive and moderately
active after intra-peritoneal injection in assays testing for anticon-
vulsant activity. In addition, previous data showed that replacing
the NO2 group by a trifluoromethyl group had only a marginal ef-
fect on potency, but advantageously reduced the polar surface area
(PSA). Therefore, we speculated that such a modification may have
positive impact on physico-chemical properties and oral absorp-
tion. Furthermore, we studied diverse amino substituents in posi-
tion 6 of the scaffold.
O
H
N
H2N
F3C
i
N
SO2Me
O
N
H
12
Scheme 2. Synthesis of intermediate 12. Reagents and conditions: (a) Ac2O,
toluene, 80 °C 2.5 h then 25 °C, 18 h; (b) KNO3, H2SO4, 25 °C, 5 h (53% over two
steps); (c) KMnO4, MgSO4 ꢁ H2O, 90–100 °C, 3 h (43%); (d) H2SO4, MeOH/H2O,
reflux, 2 h; (e) H2SO4, MeOH, reflux, 16 h (90% over two steps); (f) COCl2, toluene,
140 °C, 1 h, 20 bar; (g) MeSO2NHNH2, THF, 25 °C, 17 h (75% over two steps); (h)
NaOH 1 N, THF, 25 °C, 4 h (86%); (i) H2, Pd/C, AcOH, 25 °C (99%).
In order to allow the introduction of a variety of substituents in
this position, we synthesized intermediates 5 (Scheme 1) and 12
(Scheme 2).
Dichloromethylation of 2 by vicarious nucleophilic substitution
afforded 3.11 The dichloromethyl group was transformed into the
methyl ester by reaction of 3 with silver trifluoroacetate, followed
by oxidation of the intermediate carboxaldehyde to the carboxylic
acid and finally by esterification (Scheme 1).
N
O
a
H
N
N
12
N
N
SO2Me
SO2Me
O
F3C
N
H
13
14
Compound 12, a more advanced intermediate, was prepared in
nine steps and in an overall yield of 13% from the commercially
available aniline 6 (Scheme 2). Acetylation of 6 followed by nitra-
tion delivered 8 which was oxidized with potassium permanganate
to the carboxylic acid 9. After esterification, the isocyanate was
formed by heating ester 10 in toluene under an atmosphere of
phosgene in an autoclave. Addition of methyl sulfonylhydrazide
to the crude isocyanate and subsequent basification of the reaction
mixture gave the quinazolinedione 11. Finally, quantitative
hydrogenolysis of the nitro group afforded amino derivative 12.
In a first round, only 6-N-substituted cyclo-heteroaromatic
groups were examined. For direct comparison with 1, analogue
13 bearing a 7-CF3 substituent was readily prepared from 12 by
classical heterocyclic synthesis. (Scheme 3) In addition, the 6-N-
pyrrole derivative 14 (Scheme 3) and 6-N-1,2,4-triazole derivative
19 (Scheme 4) were also synthesized.
Triazole derivative 19 was built from intermediate 10. Acetyla-
tion of the amino function and reduction of the nitro group gave
the corresponding aniline 16. Condensation with 1,2-diformylhy-
drazine followed by a similar sequence as described in Scheme 2
for the formation of quinazolinedione ring system, finally led to
19 (Scheme 4).
Based on analysis of the X-ray structure obtained for 1, 4-
substituted-imidazoles and triazoles were selected in order to
potentially reach an additional interaction with Glu402. So, inter-
mediate 5 was engaged in nucleophilic aromatic substitution with
various 4-substituted imidazoles and 4-substitued-1,3,5-triazoles
to give, after cyclization, compounds 21–24 (Scheme 5).
All compounds were tested in a binding assay for the orthoster-
ic ligand binding site of AMPA receptor using rat brain homoge-
nates and the radioligand [3H]-CNQX.12 Results are shown in
Tables 1 and 2.
O
b
H
N
N
12
O
O
O
O
F3C
N
H
Scheme 3. Synthesis of imidazole derivative 13 and pyrrole derivative 14. Reagents
and conditions: (a) formaldehyde 37% in H2O, glyoxal 40% in H2O, NH4OAc, AcOH,
70 °C, 28 h (27%); (b) AcOH, reflux (10–90%).
Compared to 1, the CF3 derivative 13 proved to be almost equi-
potent (81 nM vs 44 nM) whereas the free aniline intermediate 12
exhibited a weak receptor affinity of 1200 nM. Pyrrole derivative
14 displayed reduced receptor affinity compared to the imidazole
analogue. The substitution pattern of the imidazole proved to be
critical as only 4-substituted imidazole showed good receptor
affinity. Monomethylamide 21 turned out to be the best compound
of the series in terms of receptor affinity with an IC50 value of
14 nM. The corresponding dimethylamide 22 showed a 30-fold re-
duced binding affinity compared to 21 demonstrating the impor-
tance of the N–H amide (key interaction with Glu402) or a
receptor spatial constraint. In order to confirm the hypothesis, an
X-ray structure (Fig. 2) was obtained for 21 13 co-crystallized with
a construct of the human receptor hGluA and was in accordance
with its predicted binding mode. As observed for 1, the central
scaffold of 21 formed a favorable p–p stacking with Tyr450, as well
as a hydrogen bond network with residues Pro478, Thr480 and
Arg485. As predicted, hydrogen-bond with Thr686 was conserved
and an additional one was identified with Glu402 (N–H amide)
contributing to the higher binding affinity. The 1,3,4-triazole deriv-
ative 19 also showed high receptor affinity. The 4-substituted ana-

998
D. Orain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 996–999
O
Table 2
O
b
O2N
F3C
Receptor affinity and in vivo efficacy in DBA/2 mice of N-alkyl derivatives 25–29
a
H2N
F3C
O
O
10
Compound
[3H]CNQX (nM)
Audiogenic seizure
ED50 (mg/kg)a
PK
NHAc
NHAc
F (%)
Clb
15
16
25
26
27
28
29
1000 200
550 10
250 100
500 80
360 90
53% at 30
20% at 10
7.9
58
5.5
n.m.
n.m.
100
100
100
n.m.
n.m.
49
135
10.2
N
N
O
N
N
O
d, e
c
N
N
OH
O
F3C
NHAc
n.m. = not measured.
F3C
NH2
a
17
Oral dosage, 1 h post-dose. ED50 measured on the percentage of protection from
tonic seizures.
18
b
In vivo clearance measured in mL/min/kg.
N
N
O
f,g, h
H
N
N
N
SO2Me
O
F3C
N
H
19
Ser654
Thr686
Scheme 4. Synthesis of triazole 19. Reagents and conditions: (a) Ac2O, reflux, 4 h
(77%); (b) H2, Pd/C, MeOH, 25 °C (100%); (c) 1,2-diformylhydrazine, TMSCl,
triethylamine, pyridine, 100 °C, 42 h (76%); (d) trimethylsilyldiazomethane 2 M in
hexanes, MeOH, 25 °C, 2 h (34%); (e) H2SO4, MeOH/H2O, reflux, 30 min (71%); (f)
triphosgene, triethylamine, THF, 25 °C, 3 h; (g) MeSO2NHNH2, THF, 25 °C, 1 h; (h)
NaOH 1 N, THF, 25 °C, 2 h (56% over three steps).
Glu705
Arg485
Glu402
Tyr450
Pro478
CO2Me
NO2
F
a
CO2Me
NO2
Thr480
R
F3C
F3C
5
Leu479
20a-i
Figure 2. X-ray structure at 1.9 Å resolution of the ligand binding domain of a
GluA2 construct (extracellular domain) bound to 21—selected interactions are
shown in orange.
O
H
N
b-e
R
N
SO2Me
O
F3C
N
H
logues followed the same SAR as the imidazole with higher affinity
for the monomethylamide (23, 110 nM) than the dimethylamide
(24, 1020 nM), albeit with lower binding potency than their
respective imidazole counterparts.
21-29
N
R =
X
N
25 R = NHEt
26 R = NHCH2CH2OH
27 R = N(Me)CH2CH2OH
28 R = morpholine
29 R = homomorpholine
Several compounds (1, 13, 19 and 21) were tested for inhibition
of audiogenic seizures in DBA/2 mice.14 The compounds were
examined at 30 mg/kg ip and po 1 h after administration. At this
dose, all compounds gave full protection after ip but not after po
application. The lowest intraperitoneal ED50-value was obtained
with 19 (0.94 mg/kg), a compound with only marginal oral activity.
It was found that the polar substituents required for high bind-
ing affinity had a negative impact on PK parameters and more par-
ticularly on absorption properties. For instance, 19 and 21 showed
an oral absorption of only 10%. In order to overcome this issue, we
prepared derivatives with less polar 6-N-alkyl, acyl or (het-
ero)cycloalkyl substituents. This was achieved via aromatic nucle-
ophilic substitution and subsequent chemical modifications as
required (Scheme 5).
21 X = CONHMe
22 X = CONMe2
N
R =
X
N
N
23 X = CONHMe
24 X = CONMe2
Scheme 5. Synthesis of imidazole derivatives 21, 22, triazole derivatives 23, 24 and
N-alkyl derivatives 25–29. Reagents and conditions: (a) aromatic nucleophilic
substitution with imidazole, triazole and alkylamine; (b) H2, Pd/C; (c) triphosgene,
triethylamine, THF, 25 °C, 3 h; (d) MeSO2NHNH2, THF, 25 °C, 1 h; (e) NaOH 1 N, THF,
25 °C, 2 h.
Various N-monoalkyl, N-acyl and N,N0-dialkyl substituted deriv-
atives were prepared but had only micromolar affinity with mar-
ginal or no improvement compared to the naked aniline
derivative 12 (only data for the N-ethyl derivative shown). Potency
was regained with the introduction of more polar substituents as
in 26, 27 and 28. All three compounds achieved significant submi-
cromolar affinity (Table 2).
In contrast to the previous derivatives, the N-alkylated com-
pounds displayed significant anticonvulsant activity in the audio-
genic seizure model in DBA/2 mice 1 h after oral administration
(Table 2).
Table 1
[3H]-CNQX binding affinitya for 1, 12–14, 19, 21–24
Compound
IC50 (nM)
Compound
IC50 (nM)
14
420 100
110 20
1
12
13
14
19
81
21
22
23
24
2
1200 100
44 10
165
46
5
1
1020 180
a
Values are single determinations performed in triplicate or means SEM of 2–4
independent determinations performed in triplicate.
By reducing the polarity on the N-substituent, N-alkylated
derivatives displayed improved bioavailability translating to

D. Orain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 996–999
999
in vivo efficacy of the compounds after oral dosage as demon-
strated with 27, 28 and 29. In addition, in vivo clearance was found
to correlate well with the ED50 value. Indeed, going from morpho-
line derivative 28 to homomorpholine analogue 29, the ED50 value
decreased from 58 to 5.5 mg/Kg (Table 2). Compound 29 was fur-
ther tested in the maximal E-shock model15 in mice. It inhibited
convulsions of the hind legs with an oral ED50-value of 10.5 mg/
kg 2 h after administration, however with a moderate duration of
action (20% effect at 50 mg/kg at 4 h post-dose).
In summary, we developed a novel series of competitive AMPA
antagonists based on the 7-CF3-6-N-alkyl/heterocycle quinazoline-
dione scaffold. Starting from 1, screening of diverse 6-N-heteroar-
omatic fragments led to the identification of a highly potent
compound in vitro (21, IC50 = 14 nM), but with poor in vivo efficacy
after oral dosage. By fine tuning the physico-chemical properties
and reducing the overall polarity with 6-N-nonaromatic fragments,
we identified compounds with good oral activity (e.g., 29, 5.5 mg/
kg ED50-value in the mouse audiogenic seizure test). Additional ef-
forts towards increasing duration of action will be reported in due
course.
Wilfried Gunzenhauser, Aurore Dufayet, Engin Tasdelen, Anne Pi-
card, Alfred Schmidt and Matthias Walther is gratefully
acknowledged.
References and notes
1. Collingridge, G. L.; Olsen, R. W.; Peters, J.; Spedding, M. Neuropharmacology
2009, 56, 2.
2. Madden, D. R. Nat. Rev. Neurosci. 2002, 3, 91.
3. Madden, D. R. Curr. Opin. Drug Discovery Dev. 2002, 5, 741.
4. Lomeli, H.; Mosbacher, J.; Melcher, T.; Hoger, T.; Geiger, J. R. P.; Kuner, T.;
Monyer, H.; Higuchi, M.; Bach, A.; Seeburg, P. H. Science 1994, 266, 1709.
5. Bradford, H. F. Prog. Neurobiol. 1995, 47, 477.
6. Glauser, T. A. Epilepsia 1999, 40, S71.
7. Matsuo, F. Epilepsia 1999, 40, S30.
8. Rogawski, M. A.; Porter, R. J. Pharmacol. Rev. 1990, 42, 223.
9. (a) Auberson, Y. Drugs Fut. 2001, 26, 463; (b) Mattes, H.; Carcache, D.; Kalkman,
H. O.; Koller, M. J. Med. Chem. 2010, 53, 5367.
10. Koller, M.; Lingehoehl, K.; Schmutz, M.; Vranesic, I.-T.; Kallen, J.; Auberson, Y.
P.; Carcache, D. A.; Mattes, H.; Ofner, S.; Orain, D.; Urwyler, S. Bioorg. Med.
Chem. Lett. 2011, 21, 3358.V.
11. Makosza, M.; Owczarczyk, Z. J. Org. Chem. 1989, 54, 5094.
12. Honore, T.; Drejer, T.; Nielsen, E. O.; Nielsen, M. Biochem. Pharmacol. 1989, 38,
3207.
13. Kallen, J. et al. The details of this X-ray structure determination will be
published elsewhere. The coordinates have been deposited with PDB ID code
3UA8.
Acknowledgments
14. DeSarro, G. B.; Meldrum, B. S.; Nistico, G. Br. J. Pharmacol. 1988, 93, 247.
15. Wamil, A. W.; Schmutz, M.; Portet, C. Eur. J. Pharmacol. 1994, 271, 301.
The excellent technical assistance of Martin Gunzenhauser,
Herta Maria Bieler, Ralf Boesch, Martin Kessler, Matthieu Ruffin,