Methylene amine substituted arylindenopyrimidines as potent adenosine A2A/A1 antagonists

Article abstract of DOI:10.1016/j.bmcl.2010.03.042

A novel series of arylindenopyrimidines were identified as A_2A and A₁ receptor antagonists. The series was optimized for in vitro activity by substituting the 8- and 9-positions with methylene amine substituents. The compounds show excellent activity in mouse models of Parkinson's disease when dosed orally.

Full text of DOI:10.1016/j.bmcl.2010.03.042

Bioorganic & Medicinal Chemistry Letters 20 (2010) 2864–2867
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Methylene amine substituted arylindenopyrimidines as potent adenosine
A2A/A1 antagonists
*
Brian C. Shook , Stefanie Rassnick, Daniel Hall, Kenneth C. Rupert, Geoffrey R. Heintzelman, Kristen Hansen,
Devraj Chakravarty, James L. Bullington, Robert H. Scannevin, Brian Magliaro, Lori Westover, Karen Carroll,
Lisa Lampron, Ronald Russell, Shawn Branum, Kenneth Wells, Sandra Damon, Scott Youells, Xun Li,
Mel Osbourne, Keith Demarest, Yuting Tang, Kenneth Rhodes, Paul F. Jackson
Johnson & Johnson Pharmaceutical Research and Development, L.L.C., Welsh and McKean Roads, PO Box 776, Spring House, PA 19477, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of arylindenopyrimidines were identified as A2A and A1 receptor antagonists. The series
was optimized for in vitro activity by substituting the 8- and 9-positions with methylene amine substit-
uents. The compounds show excellent activity in mouse models of Parkinson’s disease when dosed orally.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 20 January 2010
Revised 2 March 2010
Accepted 8 March 2010
Available online 11 March 2010
Keywords:
A2A antagonists
A1 antagonists
Adenosine antagonists
Parkinson’s disease
Catalepsy
Dopamine
Parkinson’s disease (PD) is a chronic, progressive neurological
disease that affects ꢀ1% of the population over the age of 65.1 It
is characterized by loss of dopamine neurons in areas of the brain
that are important for motor function, mood, and cognition.
Although the primary symptom of PD is motor dysfunction, the
disease also has comorbidities associated with it including anxiety,
depression, and cognitive impairment.
Adenosine is a neuromodulator that coordinates responses to
dopamine and other neurotransmitters in areas of the brain that
are responsible for motor function, learning and memory.2 Adeno-
brain, particularly striatum, while A2B and A3 receptors are not.4
Literature reports have shown that A2A antagonists may be useful
in the treatment of PD.5 In fact, several selective A2A antagonists
have advanced into clinical development.6
There have been several reports published suggesting that aden-
osine A1 antagonists may improve learning and memory.2c,d This
wouldsuggest that a dual A2A/A1 antagonist may offer improvedben-
efit to PD patients as it is known that cognitive deficiencies increase
as the disease progresses. Unfortunately, it is unknown what balance
ofA1 versusA2A antagonismwouldbe idealforPDpatient benefit. We
wouldliketoreportherein a novelseriesofarylindenopyrimidines as
dual A2A/A1 antagonists for the potential treatment of PD.7
sine is comprised of four distinct sub-types designated A1, A2A, A2B
,
and A3.3 Both A2A and A1 receptors are highly expressed in the
O
O
O
O
O
HCl, EtOH,
ArCHO
80-90%
guanidine-HCl
NaOMe, MeOH
15-20%
Ar
Ar
N
N
1
2
3
NH2
Scheme 1. Synthesis of arylindenopyrimidines.
* Corresponding author.
E-mail address: bshook@its.jnj.com (B.C. Shook).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.03.042

B. C. Shook et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2864–2867
2865
Table 1
(Scheme 1). These compounds were prepared in two steps starting
from the commercially available indanedione 1. Condensation with
the appropriate aldehyde gave the intermediate benzylidene 28
that was then reacted with guanidine under basic conditions to
give the corresponding amino pyrimidine 3.7
In vitro activity for A2a and A1 functional assays, and in vivo results for mouse
catalepsy at 10 mg/kg, po
Compound HetAr
A2A Ki
(nM)
A1 Ki
(nM)
Mouse catalepsy
10 mg/kg, po
A variety of aryl and heteroaryl aldehydes were incorporated to
explore the scope and generality of the aryl and heteroaryl substit-
uents (Table 1). Although most substitution was tolerated the
2-substituted furan 4 had superior functional in vitro and in vivo
activity. This compound reversed haloperidol induced catalepsy
in mouse9 with an ED50 of 5.0 mg/kg. Further characterization of
this compound revealed that it was Ames10 positive. Ames liabili-
ties are not uncommon for unsubstituted furans and we tried to
exploit this liability to increase solubility of this series. Amine sub-
stitution, compound 6, on the furan did eliminate the Ames liabil-
ity, but also caused decreased in vivo activity. Simple substitution
with chlorine, compound 5, or methyl, not shown, also eliminated
the Ames liability, but both compounds were inactive in vivo.
Active ED50 = 5.0 mg/
kg
4
5
0.1
0.2
0.4
0.5
O
O
Inactive
Cl
N
Active ED50 = 17.1 mg/
kg
6
10.5
40.0
O
N
Active ED50 not
determined
7
8
0.6
0.5
3.2
6.9
S
N
Inactive
S
9
10
11
4.6
0.1
5.5
16.4
1.1
Inactive
N
Active ED50 = 8.0 mg/
kg
Other heterocycles like thiophene
decreased or no in vivo activity.
7 and thiazole 8 showed
11.6
Inactive
Cl
Generally compounds bearing phenyl or substituted phenyl
10–13, had no Ames liability while maintaining good functional
in vitro potency, some also had in vivo activity. Our attention then
turned to other parts of the molecule to optimize for in vivo activ-
ity, PK properties, and solubility. It is worth noting that the NH2 of
the amino pyrimidine must be unsubstituted as a single methyl
substituent completely eliminates any in vitro activity.
12
13
1.6
2.5
Inactive
MeO
32.5
172
Inactive
OMe
The focus was to substitute the ‘A’ ring of the arylindenopyrim-
idine core to explore where and what substituents were tolerated.
The plan was to diversify the compounds later on in the synthesis
Initial screening hits lead to a series of arylindenopyrimidines
that were potent A2A/A1 antagonists generalized by structure 3
Pd(OAc)2
PPh3
CO2Me
DMADC
OAc
toluene/AcOH
CO2Me
toluene
14
15
16
(81%)
DDQ
benzene
(61%)
O
O
CO2Me
NaH, EtOAc
HCl, EtOH
(90%)
CO2Et
ONa
(60%)
CO2Me
O
19
18
17
KF, CS2
MeI, DMF
(75%)
O
N
O
N
O
1. ArMgCl, THF
(63-75%)
2. K2CO3, DMF,
SMe
Ar
N
Ar
N
SMe
O
guanidine; (80-90%)
NH2
3 : 1
NH2
20
21
22
1. AD mix
(72-77%)
2. separate
regioisomers
OH
OH
O
O
O
6
Ar
Ar
N
Ar
N
7
8
1. HIO4, THF; (90-93%)
2. R'RNH, THF,
NaBH(OAc)3 (60-90%)
N
9
N
N
N
OH
R'RN
NH2
NH2
NH2
OH
24
25-36
23
Scheme 2. Synthesis of arylindenopyrimidines substituted in the 9-position.

2866
B. C. Shook et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2864–2867
Table 2
14 which was treated with Pd(OAc)2 to generate the 1,3,5-hexatri-
A2A/A1 antagonists substituted in the 9-position
ene 15 in situ. The triene reacted nicely with dimethylacetylene
dicarboxylate (DMADC) to generate 16, that is, subsequently oxi-
dized to the corresponding phthalic ester 17using DDQ. The phthalic
ester was then reacted under Claisen condensation conditions using
ethyl acetate to give the stable sodium salt 18.11 Finally, decarboxyl-
ation under acidic conditions afforded the vinyl indanedione 19.
The diketone 19 reacted with CS2 under mild conditions and
was subsequently trapped with MeI to afford the dithioketene
acetal 20 (Scheme 2).12 Aryl Grignards reacted smoothly with 20
in a 1,4-fashion followed by reaction with guanidine to give the
corresponding amino pyrimidines 21 and 22 in a 3:1 ratio, respec-
tively.7 At this point the regioisomers were not separable via
column chromatography, so the vinyl substituents were dihydrox-
ylated using AD-mix to give the corresponding diols 23 and 24.13
The diols were very separable via chromatography and each was
carried on individually at this point, the less abundant regioisomer
24 will not be shown. The diol 23 was oxidized with periodic acid14
to give the corresponding aldehyde, not shown, that is, reacted
with a variety of amines under reductive amination15 conditions
to afford target molecules 25–36. Analogous compounds substi-
tuted in the 6-position were not active in the A2A functional
in vitro assay.
Table 2 illustrates a number of compounds that were synthe-
sized having various amino and aryl substituents. Each has good
functional in vitro potency for both A2A and A1, and most have
some in vivo activity in mouse catalepsy, which was the primary
animal model.9 Acyclic amino substituents had good in vitro
potency, but generally lacked in vivo activity as exemplified in
compounds 25 and 26. Cyclic amino groups, however, showed
good in vitro and in vivo activity. The morpholine and pyrrolidine
analogs, 31–33 and 34–36, respectively, represent optimal substi-
tution for in vivo potency, with compound 35 having an
ED50 = 0.8 mg/kg. Most substitution on the aryl group resulted in
decreased activity both in vitro and in vivo, but the 4-fluoro and
3-cyano groups were well tolerated and increased potency
in vivo for compounds 32, 33, and 35.
O
Ar
N
N
R'RN
NH2
Compound NRR0
Ar
A2A Ki
(nM)
A1 Ki
(nM)
Mouse catalepsy
ED50 (mg/kg), po
N
25
Ph
40.1
119
Inactive
N
Et2N
N
26
27
Ph
Ph
18.3
14.3
107
Inactive
5.0
40.8
28
29
Ph
Ph
11.3
7.9
94.2
34.1
7.8
N
N
N
N
O
10.7
N
30
Ph
Ph
8.6
95.2
Inactive
31
32
3.3
3.8
32.9
155
5.6
1.3
O
O
O
N
N
N
4-F-
Ph
3-
CN-
Ph
33
5.4
75.0
1.7
34
35
Ph
2.5
3.6
116
3.8
0.8
N
N
4-F-
Ph
85.0
36
Ph
11.3
140
Inactive
N
In vitro activity for A2a and Ai functional assays, and ED50’s for mouse catalepsy.
to maximize the efficiency, so ideally the core needed to be made
that had a handle on the A-ring to develop the SAR. Unfortunately
there are not many indanediones that are commercially available,
so 19 was synthesized having a vinyl group for manipulation later
on in the synthesis (Scheme 2). The indanedione was prepared
starting from the commercially available 2,4-hexadienyl acetate
At this point the SAR was extensively explored various substitu-
tions at carbons 6 and 9, but the SAR needed to be completed for
analogs substituted at carbons 7 and 8. Analogous chemistry
O
NaHMDS,
1. K CO , DMF,
2 3
SMe
SMe
SMe
N
CS ; MeI
guanidine-HCl
2. Air
(53% for 2 steps)
2
(92%)
N
O
O
37
38
39
NH
2
(Boc) O, DMAP
2
(72%)
DMF
O
N
O
Ar
N
SMe
N
ArB(OH)
2
Pd(dppf)Cl , CuTC,
2
o
N
40
41
dioxane 80
C
N(Boc)
N(Boc)
2
2
NBS, DBP
benzene
(55-73%)
(40-80%)
O
O
Ar
N
Ar
1. TFA (90-98%)
N
N
2. NRR' (77-90%)
N
NRR'
Br
42
43-54
NH
N(Boc)
2
2
Scheme 3. Synthesis of arylindenopyrimidines substituted in the 8-position.

B. C. Shook et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2864–2867
2867
Table 3
Compound 41 underwent benzyl bromination to afford the corre-
sponding bromide 42. Removal of the Boc groups with TFA fol-
lowed by alkylation with a variety of amines gave the desired
target compounds 43–54.
A2A/A1 antagonists substituted in the 8-position
O
Ar
N
R'RN
Table 3 illustrates several dual A2A/A1 antagonists having com-
parable activity to those shown in Table 2. One obvious difference
however is the increased in vivo potency of the analogs substituted
in the 8-position over those in the 9-position. For example, the
piperidine analog 46 had an ED50 = 0.3 mg/kg compared to its reg-
ioisomer 29 having an ED50 = 5.0 mg/kg. Another example is seen
in the pyrrolidine analog 53 which had an ED50 = 0.2 mg/kg while
its regioisomer 34 had an ED50 = 3.8 mg/kg. Also, the homopiper-
azine 30 was inactive in the 9-position, but the 8-position regio-
isomer 50 had an ED50 = 0.7 mg/kg. This effect was general for
most of the analogs prepared in both of the positions. Again, acyclic
analogs like 43 lacked in vivo efficacy similarly to compounds 25
and 26. Interestingly, when a heteroaryl group was attached to
the acyclic amine chain the in vivo activity returned as seen for
compounds 44 and 45.
N
NH2
Compound
NRR’
Ar
A2A Ki
(nM)
A1 Ki
(nM)
mouse catalepsy
ED50 (mg/kg), po
N
43
44
45
Ph
Ph
Ph
7.8
20.0
12.5
26.3
Inactive
1.2
N
H
N
5.3
5.4
O
N
H
N
1.6
46
47
48
49
Ph
3.0
9.9
20.4
95.7
86.2
225
0.3
0.6
1.7
3.5
N
N
N
N
4-F-Ph
Ph
9.3
N
In summary, it was shown that methylene amine arylindeno-
pyrimidines substituted at carbons 8 and 9 had potent functional
in vitro activity for both A2A and A1. These analogs also demon-
strated very potent activity in an animal model of PD.
4-F-Ph
29.8
N
50
Ph
12.9
114
0.7
N
51
52
53
54
Ph
5.9
1.0
73.0
1.8
0.3
1.7
0.2
1.6
O
N
N
N
N
References and notes
Ph
O
1. Lozano, A. M.; Lang, A. E.; Hutchison, W. D.; Dostrovsky, J. O. Curr. Opin.
Neurobiol. 1998, 8, 783.
Ph
4.1
17.0
66.2
2. (a) Muller, C. E.; Scior, T. Pharm. Acta Helv. 1993, 68, 77; (b) DeNinno, M. P.
Annu. Rep. Med. Chem. 1998, 33, 111; (c) Pires, V. A.; Pamplona, F. A.; Pandolfon,
P.; Fernandes, D.; Prediger, R. D. S.; Takahashi, R. N. Behav. Pharmacol. 2009, 20,
134; (d) Davidson, D. A.; Weidley, E. Life Sci. 1976, 18, 1279–1284.
3. Fredholm, B. B.; Abbraccio, M. P.; Burnstock, G.; Daly, J. W.; Harden, T. K.;
Jacobson, K. A.; Leff, P.; Williams, M. Pharmacol. Rev. 1994, 46, 143.
4. Dunwiddie, T. V.; Masino, S. A. Annu. Rev. Neurosci. 2001, 24, 31.
5. (a) Jacobson, K. A.; van Galen, P. J. M.; Williams, M. J. Med. Chem. 1992, 35, 4007;
(b) Muller, C. E. Drugs Future 2000, 25, 1043.
6. Bara-Himenez, W.; Sherzai, A.; Dimitrova, T.; Favit, A.; Bibbiani, F.; Gillespie,
M.; Morris, M. J.; Mouradian, M. M.; Chase, T. N. Neurology 2003, 61, 293.
7. Heintzelman, G. R.; Bullington, J. L.; Rupert, K. C. WO Patent 2005042500.
8. Bullington, J. L.; Cameron, J. C.; Davis, J. E.; Dodd, J. H.; Harris, C. A.; Henry, J. R.;
Lee Pellegrino-Gensey, J.; Rupert, K. C.; Siekierka, J. J. Bioorg. Med. Chem. Lett.
1998, 8, 2489.
9. (a) Zarrindast, M. R.; Modabber, M.; Sabetkasai, M. Pyschopharamcology 1993,
113, 257; (b) Schwarzschild, M. A.; Agnati, L.; Fuxe, K.; Chen, J. F.; Morelli, M.
Trends Neurosci. 2006, 29, 647.
10. Ames, B.; Lee, F.; Durston, W. Proc. Natl. Acad. Sci. 1973, 70, 782.
11. Buckle, D. R.; Morgan, N. J.; Ross, J. W.; Smith, H.; Spicer, B. A. J. Med. Chem.
1973, 16, 1334.
12. Mashraqui, S. H.; Hariharasubrahmanian, H. J. Chem. Res., Synopses 1999, 492.
13. Hentges, S. G.; Sharpless, K. B. J. Am. Chem. Soc. 1980, 102, 4263.
14. Saha, M.; Das, T. K.; Das, A.; Ghosh, N. R. Synth. Commun. 1990, 20, 137.
15. Abdel-Magid, A. F.; Carson, K. G.; Harris, B. D.; Maryanoff, C. A.; Shah, R. D. J.
Org. Chem. 1996, 61, 3849.
4-F-Ph
12.8
In vitro activity for A2a and Ai functional assays, and ED50’s for mouse catalepsy.
allowed us to make some methylene amine analogs at positions 7
and 8 similar to those in compounds 25–36. We quickly identified
that substitution was tolerated on carbon 8 giving good in vitro po-
tency for A2A and A1 while it decreased activity on carbon 7. It was
decided to design a regioselective synthesis to access the desired
target compounds having substitution at carbon 8 because separa-
tion of 7 and 8 substituted regioisomers was difficult and some-
times not possible (Scheme 3).
The commercially available 6-methyl indanone 37 was reacted
with CS2 under basic conditions to afford the dithioketene acetal
38.16 Compound 38 reacted with guanidine to form an intermedi-
ate amino pyrimidine, not shown, that was then oxidized to the
corresponding ketone by passing air through the solution to give
39.7 The amino pyrimidine was di-Boc protected using excess
(Boc)2O and DMAP to give 40. The aryl substituent was installed
via a modified Suzuki reaction under Liebeskind-type conditions
using the methylthioether as the coupling partner to afford 41.17
16. Kraus, G. A.; Sy, J. O. J. Org. Chem. 1989, 54, 77.
17. (a) Yu, Y.; Liebeskind, L. S. J. Org. Chem. 2004, 69, 3554; (b) Kusturin, C.;
Liebeskind, L. S.; Rahman, H.; Sample, K.; Schweitzer, B.; Srogl, J.; Neumann, W.
L. Org. Lett. 2003, 5, 4349; (c) Liebeskind, L. S.; Srogl, J. Org. Lett. 2002, 4, 979.