Structural analogues of some highly active non-competitive AMPA antagonists

Article abstract of DOI:10.1016/S0960-894X(00)00117-7

Some 5-methyl analogues (14a-e) of the non-competitive AMPA antagonists 3-acylated 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-4,5-dihydro-3H-2,3-be nzodiazepines (2,3) have been synthesized. Generally they show diminished or low biological activity but

Full text of DOI:10.1016/S0960-894X(00)00117-7

Bioorganic & Medicinal Chemistry Letters 10 (2000) 899±902
Structural Analogues of Some Highly Active Non-Competitive
AMPA Antagonists
Tamas Hamori, a Sandor Solyom, a,* Pal Berzsenyi, a
Ferenc Andrasi a and Istvan Tarnawa b
aInstitute for Drug Research, Ltd, Berlini-u. 47-49, H-1045 Budapest, Hungary
bGedeon Richter Ltd, Gyomroi-u. 19-21, H-1103 Budapest, Hungary
È
È
Received 24 September 1999; accepted 15 February 2000
AbstractÐSome 5-methyl analogues (14a±e) of the non-competitive AMPA antagonists 3-acylated 1-(4-aminophenyl)-4-methyl-7,8-
methylenedioxy-4,5-dihydro-3H-2,3-benzodiazepines (2,3) have been synthesized. Generally they show diminished or low biological
activity but two derivatives (14a,b) reveal e€ects comparable to those of GYKI 52466 (1), the prototype non competitive AMPA
antagonist. # 2000 Elsevier Science Ltd. All rights reserved.
The discovery of GYKI 52466 (1, Fig. 1) as the proto-
type of the non-competitive AMPA antagonists (also
called negative allosteric modulators of the AMPA
receptor) induced wide-ranging research activities
around the 2,3-benzodiazepines.1 We have found highly
active analogues (2,3) among the 3-acylated 1-(4-amino-
phenyl)-7,8-methylenedioxy-4,5-dihydro-3H-2,3-benzo-
diazepines.2 An enantioselective synthesis3 elaborated by
us rendered access to the pure isomers and the enantio-
mer ( )2 (GYKI 53773) with an 4R con®guration was
chosen as drug candidate, which is now in clinical
investigation as LY 300164.4
During our structure±activity studies we have investi-
gated some compounds where the 4-methyl group of 2
has been moved to the 5-position. Herein we report the
chemistry and biological activity of these compounds.
Chemistry
A known transformation of 1-aryl-1-propenes to 2-aryl-
propionaldehydes by treatment with iodine in the pre-
sence of silver(I)oxide in aqueous solution9 was applied
to isosafrol 6, providing 7 in 80% yield (Scheme 1).
Reduction of the latter with sodium borohydride in
ethanol gave phenylethanol derivative 8. Reaction of 8
with 4-nitrobenzaldehyde in benzene at rt using concd
HCl gave a nearly 7:3 cis/trans mixture of isochromane
9 (60%), which was converted to hemiacetal 10 (93%)
as a 1:1 mixture of stereoisomers by air oxidation in the
presence of 50% NaOH in a mixture of DMF and
DMSO (4:1). Reactions of 10 with di€erent acylhy-
drazides were performed in isopropanol in the presence
of catalyst amount of concd HCl, providing hydrazones
11a±d,f in good yields (84±93%) as mixtures of Z/E
isomers. In the case of 11e (86%), slightly more than 1
equiv of HCl was used. Mesilations of 11a±f in di-
chloromethane gave 12a±f generally as solid foams,
which were in turn further reacted in methanol with a
50% solution of NaOH in water to give 13a±e with
variable yields (33±76%). Under these reaction condi-
tions the isonicotinoyl group of 12f was hydrolyzed to
give 13g (47%) as the main product and only trace
amount of 13f was isolated (7%). 13a±e and 13g were
A thorough investigation by us revealed several struc-
tural features which are important for the non-compe-
titive AMPA antagonist activity of the original
molecules 1±3.5 Additionally, it has been found that the
3-acyl functionality of 2 and 3 can be substituted by a 2-
pyridyl moiety, obviously through the similarity of the
two substituents concerning the H-bond acceptor capa-
bilities of the carbonyl oxygen and the ring nitrogen
atom of similar orientation.6 Several substituted 4H-2,3-
benzodiazepin-4-ones also have been found to be novel
non competitive AMPA antagonists.7 Some 1,2-dihy-
drophthalazines such as 4 and 5 have been found to
have activity similar to that of GYKI 52466 (1).8 Com-
pound 4 can be seen as derivative of 3 by deleting the
methylene group from 3.
*Corresponding author. Fax: +36-1-399-3356; e-mail: h13759sol@
ella.hu
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00117-7

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T. Hamori et al. / Bioorg. Med. Chem. Lett. 10 (2000) 899±902
900
Figure 1.
Scheme 1. (a) I2, Ag2O; (b) NaBH4; (c) p-NO2-C6H4-CHO, HCl, benzene; (d) O2, OH ; (e) R-NHNH2, cat. HCl; (f) MsCl, Et3N; (g) OH ; (h)
RaNi, H2NNH2.

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T. Hamori et al. / Bioorg. Med. Chem. Lett. 10 (2000) 899±902
901
reduced in a mixture of methanol and dichloromethane
by the RaNi/hydrazine methodology10 to give ®nal
products 14a±e (yields vary between 52±81%) and 14g
(68%) respectively.11
Biological evaluation and results
The structure±activity relationships of the new com-
pounds were investigated in vivo and in vitro. The
compounds were examined in vitro for inhibition of
kainate (5 mM) and/or AMPA (5 mM) evoked spreading
depression in isolated retina prepared from young
chicken.12 Selected compounds (14a and 14b) were also
investigated for inhibition of AMPA (5 mM) induced
whole-cell currents in freshly isolated cerebellar Pur-
kinje cells.13 Table 1 shows that 14a and 14b had com-
parable potencies to 1 (GYKI 52466). Compound 14b
(20 mM) was further tested for inhibition of whole cell
currents induced by 1, 10 and 20 mM AMPA and no
di€erence was seen in its inhibitory potency compared
with that of 5 mM AMPA, indicating a non competitive
mode of action (data not shown).
Figure 2. Neuroprotective e€ect of 14b against MCAO in rats. 14b
was administered 6 times in every 30 min after occlusion in a dose of 2
mg/kg iv *p<0.01, signi®cance was calculated by unpaired Student's
test.
those of 1. This compound was selected for testing in a
transient middle cerebral artery occlusion (MCAO)
model in rats.19,20 The middle cerebral artery was
occluded for 60 min by use of an intraluminal suture
technique, with reperfusion for 24 h following removal
of the occluding ®lament. Neuronal damage was deter-
mined by measurement of the area of necrotic tissue
following 2,3,5-triphenyl-tetrazolium chloride (TTC)
staining of sections taken from the ischemic region.
Figure 2 shows that 14b provided signi®cant neuropro-
tection in the MCAO model in rats. In independent
experiments, compounds 1 and ( )2 also had protective
e€ect in the dose of 1 and 2 mg/kg iv, respectively.
The molecules were tested for anticonvulsant activity
using the maximal electroshock seizure (MES) model14
and the maximal metrazole seizure model (MMS)15 and
for muscle relaxant activity, using the inclined screen
test in mice.16 The gross behavioural changes were
evaluated in mice according to Irwin.17
The drugs were administered orally in the seizure mod-
els 60 min before testing the electric shock or metrazole,
and intraperitonally (ip) 30 min before testing in the
muscle relaxation model. For the Irwin test they were
administered in doses of 100 and 200 mg/kg ip and po,
respectively. The ED50 values were determined by the
Licht®eld±Wilcoxon method.18 As shown in Table 1,
the ecacies of 14b in all in vivo assays were similar to
The pharmacological results revealed that 3-acylated 1-
(4-aminophenyl)-5-methyl-7,8-methylenedioxy-4,5-dihy-
dro-3H-2,3-benzodiazepines had a somewhat lower
biological activity than the corresponding 4-methyl
analogues,2 but some of these compounds retained
reasonable in vitro and in vivo AMPA antagonistic
potencies. 14a Inhibited kainate response at lower con-
centration than AMPA response in the retinal spreading
Table 1. Screening results with (‹)-5-methyl-7,8-methylenedioxy-4,5-dihydro-3H-2,3-benzodiazepinesa
Compd no.
Behav. changes
(100 mg/kg ip;
200 mg/kg po)
Retinal spreading
depr. test
Whole-cell
current
inhibition
5 mM AMPA
MES
test
MMS
test
Incl. screen
test
ED50, mg/kg, po ED50, mg/kg, po ED50, mg/kg ip
IC50 (mM)b
1
Loss of righting re¯ex
Loss of righting re¯ex
Adynamia
A: 6.3b
K: 9.5
A: 1.7
K: 2.6
A: ꢀ20
K: 3.4
A: 15.6
K: ꢀ20
A:>20
A:>20
A:>20
NTd
IC50=9.9 mM
IC50=2.5 (mM)
5 mM: 54.0 (%)
5 mM: 52.7 (%)
37.4
(29.2±47.5)
8.6
(7.0±10.6)
69.3
(49.3±97.4)
48.8
(41.0±57.9)
>100
>100
119.8
(108.5±132.3)
16.8
(10.2±27.6)
135.3
(105.3±173.8)
67.6
(55.6±82.2)
NT
NT
47.1
(44.2±50.2)
13.4
(11.2±16.0)
95.3
(76.2±119.1)
55.9
(46.9±66.7)
>200
>200
(
)2
14a
14b
Loss of righting re¯ex
14c
14d
14e
14g
é
é
NT
NT
NT
NT
c
SMA# , ataxy, mild muscle relaxation
>100
47.1
(40.5±54.7)
NT
NT
>200
100±200
SMA", ataxy, stereotypia,
licking, muscle rigidity
aThe 14g derivative, without acyl group in position 3, caused behavioural excitation, therefore it was not examined in retinal spreading depression
test. This feature resembled that of another subclass of 2,3-benzodiazepines, such as GYKI 52895,21 which had DA uptake inhibitory property but
had no AMPAantagonistic potency (IC50>200 mM).
bA, AMPA K, kainate.
cSMA#: decrease of spontaneous motor activity; SMA", increase of spontaneous motor activity.
dNT, not tested.

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T. Hamori et al. / Bioorg. Med. Chem. Lett. 10 (2000) 899±902
902
depression test, suggesting a preferential action to kai-
nate receptors. However, the compound inhibited
AMPA induced whole cell currents in cerebellar Pur-
kinje cells at 5 mM, thus the clari®cation of the issue of
kainate receptor speci®city needs further experiment.
14a and 14b showed a considerable activity in the in
vitro tests. However, they were relatively less e€ective in
the in vivo tests, compared with ( )2. This discrepancy
may re¯ect the slightly di€erent pharmacokinetic pro®les
of the compounds.
Constanti, A. G. J. Med. Chem. 1997, 40, 1258. (b) De Sarro, A.;
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Acknowledgement
9. Kikuchi, H.; Kogure, K.; Toyoda, M. Chem. Lett. 1984, 341.
10. Furst, A. Chem. Rev. 1965, 65, 51.
11. Target compounds were characterized by IR and NMR as
well as by MS methods. Melting points (ꢁC) are as follows:
14a (201±203), 14b (185±187), 14c (231±233), 14d (176±178),
14e (195±197), 14g (108±110).
The authors wish to express their thanks to the Hungarian
National Committee for Technological Development
(OMFB) for the generous ®nancial support of the project.
12. Sheardown, M. J. Brain Res. 1993, 607, 189. Compounds
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IC50>2 0 mM. Those ones showing 40±60% were designated as
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molecules showing an inhibition bigger than 60%, in 3±5
concentrations (6±6 retinas at each concentration).
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