Antagonists of the human A2A adenosine receptor. 4. Design, synthesis, and preclinical evaluation of 7-aryltriazolo[4,5-d]pyrimidines

Article abstract of DOI:10.1021/jm800961g

Antagonism of the human A_2A receptor has been implicated as a point of therapeutic intervention in the alleviation of the symptoms associated with Parkinson's disease. This is thought to occur, at least in part, by increasing the sensitivity of the dopaminergic neurons to the residual, depleted levels of striatal dopamine. We herein describe a novel series of functionalized triazolo[4,5-d]pyrimidine derivatives that display functional antagonism of the A_2A receptor. Optimization of these compounds has resulted in improvements in potency, selectivity, and the pharmacokinetic properties of key derivatives. These efforts have led to the discovery of 60 (V2006/BIIB014), which demonstrates strong oral activity in commonly used models of Parkinson's disease. Furthermore, this derivative has shown excellent preclinical pharmacokinetics and has successfully completed phase I clinical studies. This compound is presently undergoing further clinical evaluation in collaboration with Biogen Idec.

Full text of DOI:10.1021/jm800961g

J. Med. Chem. 2009, 52, 33–47
33
Antagonists of the Human A2A Adenosine Receptor. 4. Design, Synthesis, and Preclinical
Evaluation of 7-Aryltriazolo[4,5-d]pyrimidines
Roger J. Gillespie,† Samantha J. Bamford,† Ruth Botting,† Mike Comer,† Sarah Denny,† Suneel Gaur,† Michael Griffin,†
Allan M. Jordan,*,‡ Anthony R. Knight,† Joanne Lerpiniere,† Stefania Leonardi,† Sean Lightowler,† Steven McAteer,†
Angela Merrett,† Anil Misra,† Antony Padfield,† Mark Reece,† Mona Saadi,† Daniel L. Selwood,† Gemma C. Stratton,†
Dominic Surry,† Richard Todd,† Xin Tong,† Vicki Ruston,† Rebecca Upton,† and Scott M. Weiss†
Vernalis (R&D) Ltd., Oakdene House, 613 Reading Road, Winnersh, Wokingham RG41 5UA, U.K., and Vernalis (R&D) Ltd., Granta Park,
Cambridge CB21 6GB, U.K.
ReceiVed July 30, 2008
Antagonism of the human A2A receptor has been implicated as a point of therapeutic intervention in the
alleviation of the symptoms associated with Parkinson’s disease. This is thought to occur, at least in part,
by increasing the sensitivity of the dopaminergic neurons to the residual, depleted levels of striatal dopamine.
We herein describe a novel series of functionalized triazolo[4,5-d]pyrimidine derivatives that display functional
antagonism of the A2A receptor. Optimization of these compounds has resulted in improvements in potency,
selectivity, and the pharmacokinetic properties of key derivatives. These efforts have led to the discovery
of 60 (V2006/BIIB014), which demonstrates strong oral activity in commonly used models of Parkinson’s
disease. Furthermore, this derivative has shown excellent preclinical pharmacokinetics and has successfully
completed phase I clinical studies. This compound is presently undergoing further clinical evaluation in
collaboration with Biogen Idec.
Introduction
treatment can induce involuntary muscle movements (dyskine-
sias) or, in extreme circumstances, dystonia, a painful, invol-
untary spasm of muscles in various parts of the body that can
be more debilitating than the underlying disease state. Dyski-
nesias occur in 68% of all Parkinson’s disease patients after 5
years of levodopa treatment and have a considerable effect upon
quality of life.6 Furthermore, because of feedback inhibition,
administration of increasing levels of exogenous levodopa results
in a reduction in the endogenous formation of the compound
(and thus endogenous dopamine). Administration of the therapy
therefore eventually becomes counterproductive, requiring
steadily increasing doses in order to retain efficacy.
These issues clearly highlight the urgent medical need for
an alternative point of therapeutic intervention that can alleviate
the symptoms of the disease while additionally offering predict-
able pharmacokinetics and a reduced incidence of side effects.
One such point of intervention appears to be antagonism of
the adenosine A2A receptor.7 One of a family of four receptors
(delineated A1, A2A, A2B, and A3), the A2A receptor, is expressed
in restricted locations within the CNS and exists primarily in
the nucleus accumbens, olfactory tubercle, and the striatum,
where it is often colocalized with the dopamine D2 receptor.8
Preclinical studies have demonstrated that administration of
selective A2A receptor antagonists can offset the effects of
dopamine D2 receptor antagonists in models of Parkinson’s
disease,9 and coadministration experiments have demonstrated
that such antagonists not only potentiate the therapeutic benefit
of levodopa but also can reduce the incidence of induced
dyskinesias compared to equivalent doses of levodopa alone.10
Furthermore, recent studies suggest that monotherapy with A2A
antagonists alleviates motor disability symptoms in clinically
relevant Parkinson’s disease models in a manner that does not
induce treatment-related dyskinesias.11
Parkinson’s disease is a neurodegenerative disorder that is
characterized by symptoms affecting smooth and well controlled
muscle movement. These symptoms often include postural
changes, rigidity, a resting tremor, and a slowing of voluntary
physical movement known as bradykinesia. Other symptoms
often include sleep disturbance, depression, and an overall
decline in cognition.1,2 The disease results from degeneration
of dopaminergic neurons in the substantia nigra, and the resultant
decrease in interstitial dopamine levels leads to alterations in
the activity of neural circuits within the basal ganglia that
regulate movement.3 Around 80% of these neurons need to be
degraded before the clinical disease symptoms become apparent,
making the condition more likely to manifest itself in the older
population. The disease has an overall incidence of around 1 in
1000 in the general populous, but this incidence increases to
around 1 in 100 in the over 60s.
Symptomatic treatment of the disorder centers around replace-
ment of the depleted dopamine in the brain, generally by admin-
istration of the dopamine precursor levodopa (3,4-dihydroxy-L-phe-
nylalanine).4,5Levodopa is decarboxylated in the brain to liberate
dopamine and is generally coadministered with a non-brain-
penetrant inhibitor of aromatic L-amino acid decarboxylase
(commonly referred to as dopa decarboxylase) to reduce the
incidence of peripheral side effects due to systemic production
of dopamine. However, this treatment is far from ideal, as the
drug suffers from erratic pharmacokinetics, leading to consider-
able problems related to the predictability of dosing. If too little
drug is absorbed into the brain, insufficient levels of dopamine
are achieved, and this leads to a premature re-emergence of
symptoms, known as an “off episode”. Alternatively, if too high
a dose is administered to counteract poor brain permeation, the
The exact role of the A2A receptor in this context is presently
unclear, but it is speculated that the A2A and dopamine D2
receptors form a heterodimeric receptor complex and antagonism
of the A2A receptor modulates the sensitivity of the D2 receptor
* To whom correspondence should be addressed. Phone: 44 (0)1223
895315. Fax: 44 (0)1223 895556. E-mail: a.jordan@vernalis.com.
†
Vernalis (R&D) Ltd., Wokingham.
‡
Vernalis (R&D) Ltd., Cambridge.
10.1021/jm800961g CCC: $40.75
2009 American Chemical Society
Published on Web 12/10/2008

34 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1
Gillespie et al.
Scheme 1. Synthesis of the A2A Receptor Antagonist 5a
to what little dopamine remains in the striatum, perhaps by
increasing the affinity of the D2 receptor for dopamine.12-16
More recent evidence has suggested that adenosine antago-
nists may not provide purely symptomatic relief for patients
with Parkinson’s disease (in a manner akin to transmitter
replacement therapies such as levodopa) but may also confer
some neuroprotective effects, potentially slowing disease pro-
gression. Compelling experimental evidence suggests that
blockade of the A2A receptor in mice can confer protection
against Parkinson’s disease-like lesions caused by the admin-
istration of the potent neurotoxin MPTP.17,18
a Reagents and conditions: (a) 2-(tributylstannyl)furan, PdCl2(PPh3)2,
NMP, 80 °C, 5 h, 65%; (b) NaH, 2-fluorobenzylbromide, DMF, room temp,
1 h, 22%.
Given these findings, there has been considerable interest in
developing well tolerated, orally bioavailable antagonists of this
receptor. The most advanced of these studies appears to be KW-
6002 1,19 a xanthine derived antagonist that recently completed
clinical trials for the alleviation of symptoms associated with
Parkinson’s disease.20,21 However, this compound failed to meet
its primary end-point in two out of three pivotal efficacy trials
and approval was declined by the FDA in 2008.22 Additional
reports have highlighted further issues that may have implica-
tions for the clinical utility of this compound, including
metabolic issues and poor photostability in both solid form and
solution.23,24
Scheme 2. Synthesis of 7-Aryltriazolopyrimidine Analoguesa
a Reagents and conditions: (a) arylboronic acid, NaHCO3, THF, H2O,
Pd(PPh3)4, reflux, o/n, 42-72%; (b) H2(g), 10% Pd/C, MeOH, 40 °C, 4 h,
∼quant; (c) isoamyl nitrite, dioxane, 80 °C, 3.5 h, 48-77%; (d) NaH,
2-fluorobenzylbromide, DMF, room temp, 1 h, 47-51%. (e) For 12, HCl,
MeOH, room temp, 1 h, quant.
We have recently revealed that the antimalarial compound
mefloquine 2 is a potent and reasonably selective antagonist of
the A2A receptor. Additionally, we have described our efforts
to optimize this compound, and a number of related series, in
an effort to find a candidate compound with a suitable profile
for clinical development.25-27
Scheme 3. Synthesis of 7-Aryltriazolopyrimidine Analoguesa
Though we could prepare derivatives that were potent or
selective or displayed good oral bioavailability and promising
pharmacokinetics, we had hitherto found that the parallel
optimization of these properties was a considerable challenge.
Herein, we describe our continued efforts in this area and,
ultimately, the discovery of 60, a small molecule with a profile
appropriate for clinical evaluation.28
a Reagents and conditions. (a) For 14-17: (i) heterocycle, n-BuLi, THF,
-78 °C, then ZnCl2; (ii) 13, Pd(PPh3)4, reflux, 2-4 h, 2-35%. For 18: 13,
thiophene-2-boronic acid, NaHCO3, THF, H2O, Pd(PPh3)4, reflux, 1 h, 51%.
For 19: (i) tributyl-1-(2-SEM)-1H-triazolyl-5-stannane, 13, PdCl2(PPh3)2,
DMF, 80 °C, 17 h; (ii) HCl, MeOH, room temp, 17 h, 10% over two steps.
For 20: tributylstannyl-5-thiazole, 13, PdCl2(PPh3)2, DMF, 80 °C, 1 h, 56%.
Chemistry
The synthetic routes used to prepare the derivatives used in
this study are described in Schemes 1-13. The initial starting
point for our work was the furyltriazolopyrimidine derivative
4, which was prepared by palladium-mediated coupling of the
known chlorotriazolopyrimidine 329 and 2-tributylstannylfuran.
This was further derivatized to give the 2′-fluorobenzyl deriva-
tive 5 by treatment with the corresponding benzyl bromide.
Alternative heterocyclic motifs were appended to the core
scaffold using the methods described in Schemes 2 and 3 below.
Palladium-mediated Suzuki coupling of 5-methylfuran-2-boronic
acid and 2,6-diamino-4-chloro-5-nitropyrimidine 630,31 gave the
required bicyclic core, which was reduced to give the triamino
derivative 7. Cyclization to the triazolopyrimidine was effected
with isoamyl nitrite, giving 9. Treatment with 2-fluorobenzyl
bromide yielded the desired target compound 11 (Scheme 2).
Similarly, following deprotection, the 3-pyrazolyl derivative 12
could be accessed in a similar manner.
2-Thiazole derivatives were prepared from the functionalized
core 1332 via a Negishi coupling with the appropriate arylzinc
reagents to yield 14-16 (Scheme 3). A similar method allowed
introduction of oxazole functionality, yielding 17. Palladium-

Triazolo[4,5-d]pyrimidine A2A Antagonists
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1 35
Scheme 4. Synthesis of Functionalized 7-Aryltriazolopyrimidine
Aromatic amino functionality on the pendent aromatic group
was revealed by tin(II) chloride-mediated reduction of the
corresponding nitro derivatives 35-37 to yield 52-54 (Scheme
8).
A2A Receptor Antagonistsa
The homologated variant of 54, 55, was prepared as described
in Scheme 9. Raney nickel catalyzed hydrogenation of 4-hy-
droxymethylbenzonitrile was followed by Boc protection of the
resultant amine to give 56. Bromination with carbon tetrabro-
mide and triphenylphosphine proceeded smoothly to yield the
benzyl bromide 57, which could be coupled with the triazol-
opyrimidine scaffold 4 using the above methodology. Depro-
tection with hydrochloric acid in 1,4-dioxane afforded the
desired compound.
a Reagents and conditions: (a) NaH, 2-fluorobenzylbromide, DMF, room
temp, 1 h, 4-40%.
Scheme 5. Synthesis of Phenoxy-7-aryltriazolopyrimidine A2A
Receptor Antagonist 39a
Substituted 4-aminobenzylamine derivatives 58-60 were
prepared via alkylation of the scaffold 4 with commercially
available nitrobenzyl bromides, followed by reduction with
tin(II) chloride. Where appropriate starting materials were not
commercially available, such as for examples 61-64, the
prerequisite benzyl bromides prepared as detailed in the
Experimental Section and outlined in Schemes 10-12. Conju-
gate Grignard addition to 4-nitrobenzyl bromide 65 followed
by oxidative workup gave the substituted derivatives typified
by 66, in accordance with literature precedence for correspond-
ing keto-functionalized nitrobenzene derivatives.35 Standard
alkylation of 4 with these derivatives was followed by reduction
with tin(II) chloride, giving 61 and 62. Synthesis of the
3-hydroxy-4-amino derivative 63 commenced from the com-
mercially available 3-hydroxy-4-nitrobenzoic acid 69, as detailed
in Scheme 11. Boc protection of the alcohol to give 70 followed
by transient esterification of the acid with isobutyl chloroformate
and reduction with sodium borohydride gave the hydroxymethyl
intermediate 71, which was readily brominated with carbon
tetrabromide and triphenylphosphine to yield 72. After alkylation
of the triazolopyrimidine scaffold under our standard conditions,
reduction of the nitro moiety with tin(II) chloride proceeded
with concomitant unmasking of the hydroxyl functionality to
yield the desired derivative 63. The N-methylated derivative
64 could also be accessed in an analogous manner, as detailed
in Scheme 12.
a Reagents and conditions: (a) BBr3, DCM, 0 °C, 72 h, 100%.
mediated coupling of thiophene-2-boronic acid allowed access
to the 2-thienyl derivative 18, and similarly, the corresponding
triazole derivative 19 could be accessed via a Stille coupling,
employing the appropriately protected heterocycle. The 5-thia-
zolyl variant was prepared by an analogous method, whereby
the heterocycle was coupled to the functionalized chlorotriaz-
olopyrimidine 13 using thiazolyl-5-tributylstannane, to give 20
(Scheme 3).
Benzyl derivatives were prepared by the methods detailed in
Schemes 4-6. Treatment of the 2-furyltriazolopyrimidine
scaffold 4 with the appropriate benzyl bromide gave the desired
derivatives 21-38 in moderate yields. Though the alkylation
protocol tended to generate a mixture of both the N-2 and N-3
functionalized regioisomers, in all cases the predominant N-3
functionalized derivative could be readily isolated.33 Phenolic
functionality was unmasked by treating the corresponding
methoxy derivative 32 with small aliquots of boron tribromide
in dichloromethane over 3 days to cleanly yield 39 (Scheme
5). The ester functionality present in 38 was hydrolyzed to reveal
the acid 40 using sodium hydroxide and further derivatized to
the amides 41-43 using carbonyldiimidazole in dimethylfor-
mamide (Scheme 6).
The N-acetyl derivative 77 was prepared from the com-
mercially available p-acetamidobenzyl bromide in a manner
analogous to that described in Scheme 4.
Pendent biaryl functionality was introduced via alkylation
with the corresponding alkyl bromides, prepared by halogenation
of the known, appropriately protected 5-methyl heterocycles36
with N-bromosuccinimide, as described in Scheme 13.
Results and Discussion
Alkylation with pyridylmethyl bromides failed to give the
desired products in an acceptable manner, and for these
problematic derivatives, an alternative route was devised. The
starting aminopyrimidinone 4434 was treated with tosyl chloride
to yield 45 and the tosylate moiety displaced in good yield with
2- and 3-pyridylmethylamine to incorporate the heterocyclic
functionality. Hydrogenation of the nitro group and concomitant
cyclization to the triazolopyrimidine with isoamyl nitrite yielded
the desired pyridyl-functionalized derivatives 46 and 47 (Scheme
7).
We have previously reported our efforts to optimize biaryl
scaffolds as antagonists of the human A2A receptor and, in
particular, derivatives based upon pyrazolopyrimidine, pyrrol-
opyrimidine and purine cores.27 To complement this work, we
also wished to explore the triazolopyrimidine scaffold and
therefore prepared the 7-furyltriazolopyrimidine core 4. A
comparison of the affinities of these related core structures is
detailed in Table 1.37 On first inspection, the triazolopyrimidine
core did not appear particularly promising, with a marked
reduction in binding affinity at the A2A receptor compared to
the pyrazolopyrimidine core 81. However, activity and selectiv-
ity against the other subtypes of the human adenosine receptor
were comparable with those of the purine and pyrrolopyrimidine
cores 82 and 83, respectively. Further investigations revealed
that compound 4 was moderately active in the haloperidol-
induced hypolocomotion assay (HaloLMA), a relatively simple
Though the pyridyl derivatives required an alternative syn-
thetic strategy as described above, the incorporation of other
heteroaryl derivatives was more facile and the desired derivatives
were readily prepared using the alkylation protocol detailed in
Scheme 4, to give compounds 48-51 as described in Table 4.

36 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1
Gillespie et al.
Scheme 6. Synthesis of Amido-7-aryltriazolopyrimidine A2A Receptor Antagonists 41-43a
a Reagents and conditions: (a) NaOH, MeOH, reflux, 10 min, 98%; (b) CDI, DMF, room temp, 1 h, then amine, room temp, 16 h, 23-66%.
Scheme 7. Alternative Synthesis of Pyridyl-7-aryltriazolo-
pyrimidine A2A Receptor Antagonists 46 and 47a
this group appears to be a privileged moiety in compounds
binding to the A2A receptor,42 we first sought to investigate
whether alternative groups could be combined successfully with
the triazolopyrimidine core without substantial reductions in
receptor binding affinity.
As detailed in Table 2, it was apparent that a variety of small
heteroaromatic groups could indeed be tolerated in this position.
Most small aromatic heterocycles appeared to be tolerated except
for those displaying an available N-H such as the 3-pyrazole
(12) and the 4-triazole (19). Though the 3-pyrazolyl derivative
12 showed a marked reduction in binding affinity, it still retained
activity in the HaloLMA assay after oral dosing at 30 mg kg-1
,
the same in vivo efficacy demonstrated by the considerably more
potent 2-thiazolyl derivative 14. We speculated that this
increased activity might be attributable to improved brain
penetration, though further pharmacokinetic studies would be
required to validate this hypothesis. However, given the obvious
disconnect between receptor binding affinity activity in our
efficacy model, we reasoned that the balance of physiochemical
properties displayed by these compounds would be critical to
attaining the ideal balance of in vitro potency, selectivity, oral
bioavailability, and in vivo efficacy.
a Reagents and conditions: (a) p-TsCl, NEt3, DCM, room temp, 1 h, 24%;
(b) pyridylmethylamine, NEt3, 1,2-dimethoxyethane, room temp, 16 h,
69-82%; (c) 1% Pd/C, H2 (g), EtOH EtOAc, room temp, 1 h, quant; (d)
isoamyl nitrite, 1,4-dioxane, 100 °C, 16 h, 46-50%.
Of more immediate interest was the 2-methylfuran derivative
11. Though this derivative was roughly equipotent with the furan
derivative 5, the compound displayed a substantial increase in
oral activity in the HaloLMA assay, with a minimum effective
dose of 3 mg kg-1. Once again, it appeared that a small change
in the structure of the compound had altered the physiochemical
profile sufficiently to have a marked effect upon activity in the
disease model. However, the substantial decrease in selectivity
against both the A1 and A2B receptor subtypes precluded further
optimization of this subseries at this time, and efforts focused
upon the inherently more selective scaffold typified by 5.
Scheme 8. Synthesis of Amino-7-aryltriazolopyrimidine A2A
Receptor Antagonists 52-54a
a Reagents and conditions: (a) SnCl2, EtOH, HCl, 50 °C, 2 h, 45-92%.
Given the dramatic increases in potency observed upon
incorporation of the 2-fluorobenzyl substituent, attention was
turned to the optimization of this position. Receptor binding
data for a representative selection of analogues are presented
in Table 3.
Removal of the 2-fluoro substituent yielded a slight improve-
ment in potency (compound 21), with little effect upon
selectivity. Interestingly, complete removal of aromaticity in
this position and incorporation of a cyclohexyl moiety gave only
a moderate decrease in activity while maintaining a similar
selectivity profile, perhaps indicating the group in this position
is fulfilling an interaction that is predominantly hydrophobic in
nature rather than partaking in a π-π interaction with the
receptor binding cavity.
yet robust model of the symptoms of Parkinson’s disease.38,39
Unlike the majority of the templates we had investigated in the
course of our studies in this area, this derivative not only was
active when dosed intraperitoneally but also demonstrated
limited activity after oral administration. We therefore sought
to optimize 4 in order to exploit this promising early sign of
oral bioavailability.
Previous studies on the purines, pyrrolopyrimidines and
pyrazolopyrimidines had demonstrated that incorporation of a
benzyl substituent gave a considerable increase in activity while
generally maintaining selectivity against the human A1 receptor.
This prior experience quickly led us to 5. As with previous
series, incorporation of the 2-fluorobenzyl moiety gave a
substantial (70-fold) increase in binding affinity for the A2A
receptor and a useful doubling of selectivity against the A1
receptor.
Difluorinated substituents appeared to be beneficial in terms
of both binding affinity and overall selectivity profile, with 24
meeting our predefined selectivity criteria (g50-fold selectivity
against all three receptor subtypes) for the first time. This profile
was also attained by the 2-methyl derivative 28. In general terms,
Aware that the furan displayed in our core scaffold was a
potential site of oxidative metabolism40,41 but also aware that

Triazolo[4,5-d]pyrimidine A2A Antagonists
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1 37
Scheme 9. Synthesis of the Homologated 7-Aryltriazolopyrimidine A2A Receptor Antagonist 55a
a Reagents and conditions: (a) Raney Ni, H2(g), EtOH, NEt3, room temp, 16 h, 80%; (b) NEt3, THF, room temp, 10 min, then di-tert-butyl dicarbonate,
room temp, 90 min, 89%; (c) PPh3, CBr4, 0 °C, 1 h, 65%; (d) 4, NaH, THF, 16 h, room temp, then HCl, 1,4-dioxane, MeOH, room temp, 16 h, 12%.
Scheme 10. Synthesis of Derivatized 7-Aryltriazolopyrimidine A2A Receptor Antagonists 61 and 62a
a Reagents and conditions: (a) alkylmagnesium chloride, THF, -70 °C, 1 h, then DDQ, room temp, 16 h, 16-40%; (b) 4, NaH, THF, 16 h, room temp,
19-28%; (c) SnCl2, EtOH, HCl, 50 °C, 2 h, 36-37%.
Scheme 11. Synthesis of Derivatized 7-Aryltriazolopyrimidine A2A Receptor Antagonist 63a
a Reagents and conditions: (a) di-tert-butyl dicarbonate, NEt3, THF, room temp, 16 h, 83%; (b) isobutyl chloroformate, N-methyl morpholine, THF, 0 °C,
1 h, then NaBH4, MeOH, -78 °C, 1 h, 86%; (c) PPh3, CBr4, 0 °C, 1 h, 86%; (d) 4, NaH, THF, 16 h, room temp, 78%.
though a variety of substituents were tolerated in this series,
meta-substituents tended to offer a better balance of potency
and selectivity whereas para-substituents, such as those displayed
in 34 and 37, appeared to be less well tolerated. Additionally,
though ester and amide functionality appeared to be tolerated
(compounds 38 and 41), the parent acid was some 80-fold less
potent. This result suggested a preference for nonacidic func-
tionality at this position, particularly given the tolerance for the
isoelectronic nitro functionality (compound 36). Though steric
constraints may be an issue at the para-position and may
contribute to the observed lack of tolerability discussed above,
it would appear that this is much less of an issue at the meta-
position, where even bulky amides such as 42 and, to a lesser
extent, 43, are well tolerated.
pyrazolopyrimidines and pyrrolopyrimidine series,27 we had
observed that similar benzylated derivatives were susceptible
to rapid metabolism by rodent liver microsomes, with turnover
values after 30 min in the region of 95-99%. The corresponding
functionalized triazolopyrimidines described above showed
increased stability in this in vitro assay, demonstrating much
more moderate turnover after 30 min. For example, compounds
such as the ester 38 demonstrated a markedly reduced 35%
turnover during this period under identical conditions. Unfor-
tunately, in most cases, these derivatives failed to demonstrate
any oral activity in the HaloLMA model when dosed at 30 mg
kg-1. We attributed this finding to the relatively low measured
solubility of the compounds, which were in the 30-40 µM
range,43 and we therefore moved to address this issue by
incorporation of heteroatoms in the pendent benzylic functional-
ity, as detailed in Table 4.
We were pleased to observe that, in general, metabolic
stability of these derivatives appeared to be improved over our
previously reported series. During our studies on the purine,

38 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1
Gillespie et al.
Scheme 12. Synthesis of Derivatized 7-Aryltriazolopyrimidine A2A Receptor Antagonist 64a
a Reagents and conditions: (a) di-tert-butyl dicarbonate, NEt3, THF, reflux, 48 h, 69%; (b) (i) isobutyl chloroformate, N-methylmorpholine, THF, 0 °C,
1 h; (ii) NaBH4, MeOH, -78 °C, then room temp, 2 h, 22%; (c) PPh3, CBr4, 0 °C, then room temp, 2 h, 43%; (d) 4, NaH, THF, room temp, 16 h, then HCl,
1,4-dioxane, room temp, 2 h, 23%.
Table 2. Binding Affinities of 7-Aryl Variants at the Four Human
Scheme 13. Synthesis of 7-Aryltriazolopyrimidine A2A Receptor
Antagonists 78-80a
Adenosine Receptor Subtypesa 37
,
Ki (nM)
compd
Ar
A2A
2.7
2.1
239
8.5
2.2
8.5
41
8.2
400
31
A1
A2B
A3
a Reagents and conditions: (a) NBS, benzoyl peroxide, CCl4, reflux, 16 h,
46-74%; (b) 4, NaH, THF, room temp, 16 h, 14-27%. (c) For 78: NaOMe,
MeOH, reflux, 5 h, 74%. For 79: HCl, 1,4-dioxane, methanol, room temp,
2 h, quant. For 80: dimethylamine, methanol, reflux, 25 min, 30%.
5
2-furyl
105
19
1665
553
203
86
599
154
2965
894
109
6
1778
271
53
199
836
248
1294
423
440
260
1291
2204
1256
338
2108
871
2806
1779
11
12
14
15
16
17
18
19
20
2-methylfuryl
3-pyrazolyl
2-thiazolyl
4-methyl-2-thiazolyl
5-methyl-2-thiazolyl
2-oxazolyl
2-thienyl
4-triazolyl
5-thiazolyl
Table 1. Comparison of Scaffold Binding Affinities at the Human
Adenosine A1 and A2A Receptor Subtypesa 37
,
a All values are the mean of at least two separate assay determinations,
and standard deviations for these values were generally within 20% of the
mean value.
interaction with the receptor, but increased affinity was most
dramatically observed in the para-regioisomer 45, where binding
affinity increased almost 20-fold compared to 37 while main-
taining selectivity against the other receptor subtypes. Once
again, this result suggests the existence of a sterically constrained
region of the receptor in the vicinity of the para-substituent,
where the less demanding amine functionality is more easily
accommodated in the binding site and perhaps displays optimal
geometry of interaction with the local receptor functionality.
This view was further supported by data for the homologated
aminomethyl derivative 55, which was over 150-fold less potent
at the A2A receptor than the parent aniline 54.
Ki (nM)
compd
X
Y
Z
A2A
A1
81
82
83
4
CH
N
CH
N
N
N
N
N
N
48
261
242
194
647
4951
2765
3624
CH
CH
N
a All values are the mean of at least two separate assay determinations,
and standard deviations for these values were generally within 20% of the
mean value.
We were disappointed to find that the pyridyl-functionalized
derivatives 46 and 47 failed to possess oral activity in the disease
model, despite demonstrating a considerable increase in solubil-
ity (>250 µM) and a 2-fold increase in permeability in the
Caco-2 model, compared to their nonheterocyclic counterparts.
Interestingly, although the methylfuryl derivative 49 was inactive
in this model, the corresponding 2-thienyl derivative 50 regained
Though the thiophene-2-yl derivative 50 showed only limited
activity after oral dosing, we were pleased to observe that the
ortho-substituted aniline 52 displayed the anticipated increase
in oral bioavailability. This was demonstrated by activity in the
disease model, with a minimum effective dose of 10 mg kg-1,
despite similar receptor binding affinity. This finding is perhaps
partly attributable to a moderate (3-fold) increase in perme-
ability, given the comparable soubilities of these derivatives.
However, the largely equipotent regioisomers 53 and 54
displayed a further increase in disease-relevant activity, dem-
onstrating reversal of haloperidol-induced hypolocomotion in
oral activity with a minimum effective dose of 30 mg kg-1
though the slightly more potent regioisomer 51 did not.
Reduction of the nitrobenzyl functionality displayed in 35-37
gave the corresponding anilines 52-54, which displayed a
moderate 2-fold increase in solubility over their nitro precursors.
The ortho- and meta-regioisomers showed a slight increase in
potency, perhaps indicating the formation of an additional
,
mice when dosed orally at just 1 mg kg-1
.

Triazolo[4,5-d]pyrimidine A2A Antagonists
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1 39
Table 3. Binding Affinities of N-3 Substituents at the Four Human
Table 5. Binding Affinities of Optimized N-3 Substituents with
Adenosine Receptor Subtypesa 37
Enhanced Solubility at the Four Human Adenosine Receptor
,
Subtypesa 37
,
Ki (nM)
Ki (nM)
compd
R
A2A
2.7
A1
A2B
A3
compd
R1
R2
A2A
1.5
A1
A2B
A3
5
2-F
H
105
83
230
110
118
98
109
122
634
79
226
128
24
160
282
254
259
741
643
630
885
383
646
440
907
10
440
285
1138
619
1181
450
203
269
341
360
736
340
563
693
1048
168
54
58
59
60
61
62
63
64
77
H
2-F
3-F
3-Me
3-Et
3-iPr
3-OH
H
H
H
H
H
H
H
H
Me
Ac
190
190
120
68
46
23
43
752
685
1071
1005
221
251
1359
636
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
1.9
8.5
2.3
2.0
2.2
1.9
2.3
3.0
3.0
2.2
5.4
1.8
3.9
73
6.6
3.7
28.0
4.1
4.0
3.5
0.7
1.3
1.0
1.5
1.6
1.6
cyclohexyl
2,3-diF
2,4-diF
2,5-diF
2,6-diF
3-Cl
63
26
50
249
40
2531
118
397
84
181
443
42
76
2-Me
3-Me
3-CF3
183
45
100
319
77
H
116
2380
a All values are the mean of at least two separate assay determinations,
and standard deviations for these values were generally within 20% of the
mean value.
2-OMe
3-OMe
3-CN
132
738
400
231
769
105
314
4143
700
733
1133
4-CN
2-NO2
3-NO2
4-NO2
position, given that this had already yielded interesting results
as discussed above. Particularly, we reasoned that a slight
increase in the log D of the chosen compound may facilitate an
improvement in brain penetration and give rise to increased
potency in the disease model. Results from these investigations
are detailed in Table 5.
844
1233
1174
491
3809
2576
530
3-CO2Me
3-OH
3-CO2H
3-CONH2
3-CONHiPr
3-CON(Me)iPr
832
2110
132
593
937
11.1
10.8
22
Incorporation of fluorine initially appeared to be beneficial,
with compound 50 displaying increased potency and adequate
selectivity against other receptor subtypes. However, in the
2467
a All values are the mean of at least two separate assay determinations,
and standard deviations for these values were generally within 20% of the
mean value.
HaloLMA model, activity was only observed at 30 mg kg-1
.
Small alkyl substituents were tolerated, and in all cases, binding
affinity for the A2A receptor was maintained or improved, albeit
with a slight loss of subtype selectivity for the 3-ethyl and
3-isopropyl derivatives 61 and 62. The phenolic derivative
showed good receptor potency but failed to show activity in in
vivo disease models, further confirming our hypothesis that small
increases in log D, rather than a decrease, may be beneficial
for brain penetration. As we had observed a large decline in
activity upon incorporation of bulkier groups at the para-position
in previous derivatives, we were somewhat surprised that
N-methylation appeared to be well tolerated and compound 64
retained oral activity when dosed at 1 mg kg-1, consistent with
the parent compound 54. In line with our expectations, the
bulkier N-acetylated derivative 77 showed a marked decline in
activity, suffering an 80-fold reduction in receptor affinity.
Of most interest from this exploration was the 3-methyl
derivative 60. Not only did this derivative show both a slight
improvement in potency and enhanced selectivity against the
A2B receptor over the parent 54, but when tested in the mouse
and rat haloperidol-induced hypolocomotion model, this com-
pound demonstrated a minimal effective dose of just 0.1 and 1
mg kg-1, respectively (Figure 1). By comparison, in our hands,
KW-6002 1 demonstrated activity at 0.3 mg kg-1 in the mouse
HaloLMA model (Figure 2) and 1 mg kg-1 in the corresponding
rat model.
Table 4. Binding Affinities of N-3 Substituents with Enhanced
Solubility at the Four Human Adenosine Receptor Subtypesa 37
,
Ki (nM)
compd
R
A2A
A1
A2B
A3
46
47
48
49
50
51
52
53
54
55
2-pyridyl
3-pyridyl
12.0
14.5
122
8.8
2.3
1.9
2.0
2.5
1.5
241
1117
931
1166
77
117
78
258
225
1136
192
88
164
123
270
46
1075
1019
2224
240
123
136
302
792
752
2-pyrazinyl
2-furan-2-yl
thiophene-2-yl
thiophene-3-yl
2-anilino
3-anilino
4-anilino
4-aminomethyl
63
131
190
4909
916
>10000
a All values are the mean of at least two separate assay determinations,
and standard deviations for these values were generally within 20% of the
mean value.
In light of this oral efficacy, improved receptor binding
affinity, and the better selectivity over the A1 receptor, com-
pound 54 was selected for further optimization. Given the effects
we had noted previously, where increases in bioactivity had been
associated with minor changes to the pharmacological profile
of our compounds, we postulated that the overall profile of 54
could be improved by exploitation of functionality in the meta-
As we had observed that hydrophobic interactions between
functionality at the N-3 position of the triazolopyrimidine core
and the A2A receptor appeared to be important, such as those
described for 20, we reasoned that cyclization of the pendent
functionality displayed by 60, while retaining a basic center in
this region, may give rise to additional potency and further tailor

40 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1
Gillespie et al.
Figure 1. Reversal of haloperidol-induced hypolocomotion by compound 60 in mouse and rat (0.01-10 mg/kg po): (/) p < 0.05 versus vehicle
(+haloperidol alone) control. Shown are reversal of locomotor motor deficits in mice treated with the D2 receptor antagonist haloperidol (0.2 mg/kg
ip) by the A2A receptor antagonist KW-6002. All doses are expressed as mg/kg ip. Behavioral scores represent time(s) spent active during a 60 min
test session: (/) p < 0.05 versus vehicle treatment group.
Table 7. Functional Activity of 60 at the Four Human Adenosine
Receptor Subtypesa 44
,
A2A
A1
A2B
A3
5.8
1500
mean pA2
KA (nM)
9.2
0.58
7.0
95
7.5
31
a All values are the mean of at least three separate determinations.
model when dosed at 30 mg kg-1. Given these results, further
studies on similar biaryl substituents were suspended.
As 60 achieved our predetermined targets for potency,
selectivity and oral bioactivity, further profiling of this derivative
was undertaken. Assessment of the functional activity of the
compound using a calcium mobilization-based FLIPR assay44
demonstrated that 60 acted as a functional antagonist of the A2A
receptor and displayed potency and selectivity values against
all the adenosine receptor subtypes, in good agreement with
our radioligand binding assay (Table 7). This study also
demonstrated that 60 was devoid of any intrinsic agonist activity
at this receptor.
Figure 2. Reversal of haloperidol-induced hypolocomotion by com-
pound 1 in mouse (0.3-10 mg/kg po): (/) p < 0.05 versus vehicle
(+haloperidol alone) control.
Table 6. Binding Affinities of Biaryl N-3 Substituents at the Four
Human Adenosine Receptor Subtypesa 37
,
Though the compound was only moderately soluble at neutral
pH, preparation of the dihydrochloride and dimesylate salts was
straightforward, and these were found to display increased
solubility, with measured solubilities of 18 and 36 mg mL-1
respectively.
,
In vitro metabolic profiling demonstrated that 60 did not
inhibit any of the major cytochrome P450 isoforms, reducing
the risk of drug-drug interactions, and the compound itself was
metabolized by multiple CYP450 isoforms. Permeability in the
Caco-2 transwell system45 was found to be good, at 11 × 10-6
cm s-1, and 60 was not found to be a substrate for the PGP
drug efflux transporter, unlike KW-6002 1, which displayed
some PGP affinity in our hands. Plasma protein binding was
found to be moderate, with an estimated 74-86% of the total
plasma content bound.
Rat pharmacokinetics demonstrated an estimated half-life of
2-6 h and an oral bioavailability of ∼35%. A measured brain
uptake of 57%46 indicates good penetration of the compound
from plasma into the brain, and when coupled with the Tmax of
0.5 h, these properties undoubtedly contribute to the potent
activity observed in the HaloLMA model.
To examine possible off-target effects, the compound was
assessed in the CEREP wide binding screen47 against 75 other
targets. Other than the anticipated effects upon the A2A and A1
receptors, selectivities of greater than 500-fold were observed
for all other targets investigated. Patch-clamp experiments at
doses up to 30 µM (the maximal test concentration obtained in
the assay protocol) demonstrated no activity greater than vehicle
alone on the hERG potassium channel. Further safety pharma-
cology studies indicated that the compound was nonmutagenic,
Ki (nM)
compd
heterocycle
A2A
A1
A2B
A3
78
79
80
5-indole
5-indazole
5-benzotriazole
1.1
8.6
11.9
27
190
291
59
206
134
606
2433
3013
a All values are the mean of at least two separate assay determinations,
and standard deviations for these values were generally within 20% of the
mean value.
the physiochemical properties of our derivatives in order to
improve bioactivity. Indeed, cyclization of 60 to the corre-
sponding indole derivative 78 provided a small increase in
potency and generally retained biological activity in the
HaloLMA model, showing efficacy when dosed orally at 1 mg
kg-1. However, this modification was clearly detrimental to
subtype selectivity, giving a 2-fold decrease in selectivity against
the A1 receptor (Table 6).
Furthermore, incorporation of the corresponding indazole and
benzotriazole moieties (compounds 79 and 80, respectively)
failed to restore selectivity against the A1 receptor, and
selectivities against the other two receptor subtypes were also
diminished. Of more concern was the finding that neither of
these two derivatives displayed oral activity in the HaloLMA

Triazolo[4,5-d]pyrimidine A2A Antagonists
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1 41
NaHCO3 (75 mL), 5-methylfuran-2-boronic acid (7.33 g, 0.058
mol), and Pd(PPh3)4 (1 g, 0.865 mmol) and refluxed with vigorous
stirring under argon overnight. The mixture was cooled to room
temperature, diluted with EtOAc (400 mL) and water (300 mL),
and filtered to remove insoluble material, and the filtrate was
extracted with EtOAc (2 × 100 mL). The combined organic phase
was dried (MgSO4) and concentrated in vacuo and the resulting
solid triturated with dichloromethane and filtered to give the title
compound (6 g, 72%) as a yellow solid: mp 196.3-196.9 °C; IR
showing activity in neither the Ames assay (three strains, (S9)
nor the mouse lymphoma assay in L5178Y cells. As the
compound was known to be CNS-penetrant, potential behavioral
effects were also investigated using the Irwin screen.48 Despite
dosing for 4 days at 100 mg kg-1, a dose some 300-fold higher
than the minimal effective dose in the HaloLMA assay, no overt
signs of toxicity or behavioral changes were noted other than a
slight, and expected, increase in locomotor activity.
In summary, these data demonstrate that 60 (V2006/BIIB014)
displays an encouraging pharmacological, pharmacokinetic, and
safety profile and the compound is presently undergoing phase
II clinical trials as a potential treatment for the symptoms
associated with Parkinson’s disease, in collaboration with Biogen
Idec. Further details of the preclinical and clinical development
of this compound will be reported in due course.
ν
max (Nujol)/cm-1 3442, 3169, 2930, 1629, 1463, 1377, 1027, and
790; NMR δH (400 MHz, DMSO) 7.40 (2H, br s), 7.09 (2H, br s),
6.87 (1H, dd, J 0.5, 3.2 Hz), 6.26 (2H, dd, J 1.0, 3.3 Hz), and 2.28
(3H, s).
A suspension of this material (6.6 g, 29.6 mmol) and 10% Pd/C
(0.66 g) in MeOH (100 mL) was heated at 40 °C under an
atmosphere of H2 for 3 h, cooled to room temperature, filtered
through Celite, and concentrated in vacuo to give the title compound
(5.8 g, 99%) as an off-white solid. IR νmax (DR)/cm-1 3333, 2237,
1634, 1458, 1237, 1025, 963, and 828; NMR δH (400 MHz, DMSO)
6.77 (1H, dd, J 0.5, 3.2 Hz), 6.21-6.17 (3H, m), 5.14 (2H, s),
4.21 (2H, s), and 2.35 (3H, s).
6-((1-(2-(Trimethylsilyl)ethoxymethyl)-1H-pyrazolyl-3-yl)pyri-
midine-2,4,5-triamine 8. 8 was prepared as for compound 7, using
(1-(2-(trimethylsilyl)ethoxymethyl)-1H-pyrazolyl-3-boronic acid (2.32
g, 9.6 mmol), to give the nitrodiamine as a yellow solid (0.72 g,
42%). This material was hydrogenated as described above to give
the title compound (0.32 g, 50%) which was carried forward
immediately without further purification.
7-(5-Methyl-2-furyl)-1H-[1,2,3]triazolo[4,5-d]pyrimidine-5-
amine 9. A solution of 6-(5-methyl-2-furyl)pyrimidine-2,4,5-
triamine 7 (5.8 g, 30.1 mmol) in dioxane (116 mL) was treated
with isoamyl nitrite (4.1 mL, 30.5 mmol), heated at 80 °C for 3.5 h,
and cooled to room temperature and the resulting precipitate was
filtered, washed with dioxane (10 mL) and heptane (2 × 15 mL),
then triturated with heptane and filtered to give the title compound
(4.7 g, 77%) as a sandy solid: mp 291.8-292.0 °C; IR νmax (DR)/
cm-1 3436, 3178, 1651, 1615, 1398, 1226, 1029 and 977; NMR
δH (400 MHz, DMSO) 15.5-15.3 (1H, br s), 7.84 (1H, d, J 3.5
Hz), 7.07 (2H, br s), 6.48 (1H, dd, J 3.5, J 1.0 Hz), 2.44 (3H, s).
7-(1-(2-(Trimethylsilyl)ethoxymethyl)-1H-pyrazolyl-3-yl)-1H-
[1,2,3]triazolo[4,5-d]pyrimidine-5-amine 10. 10 was prepared as for
compound 9 above, using crude 6-(1-(2-(trimethylsilyl)ethoxym-
ethyl)-1H-pyrazolyl-3-yl)-pyrimidine-2,4,5-triamine 8 (0.64 g, 2
mmol) and other reagents scaled accordingly. Column chromatog-
raphy (EtOAc/isohexane, 1:1) gave the title compound as a green
solid (0.32 g, 48%) which was used immediately.
3-(2-Fluorobenzyl)-7-(5-methyl-2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 11. 11 was prepared as for compound 5
above, using 7-(5-methyl-2-furyl)-1H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 9 (0.09 g, 0.41 mmol) and other reagents scaled
accordingly to give the title compound as a yellow solid (62 mg,
47%): mp 213.5-213.7 °C; IR νmax (DR)/cm-1 3300, 3218, 3098,
2957, 2927, 2744, 2368, 1645, 1602, 1570, 1537, 1508, 1490, 1438,
1328, and 1233; NMR δH (400 MHz, DMSO) 7.86 (1H, d, J 3.0
Hz), 7.43-736 (1H, m), 7.31 (2H, br s), 7.28-7.15 (3H, m), 6.50
(1H, dd, J 1.0, J 3.5 Hz), 5.68 (2H, s), and 2.45 (3H, s); m/z ) 325
[M + H]+.
3-(2-Fluorobenzyl)-7-(1H-pyrazol-3-yl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 12. 12 was prepared as for compound 9
above, using 7-(1-(2-(trimethylsilyl)ethoxymethyl)-1H-pyrazolyl-
3-yl)-1H-[1,2,3]triazolo[4,5-d]pyrimidine-5-amine 10. Following
alkylation, the resultant bicyclic derivative was dissolved in
methanol (2 mL), and hydrochloric acid (4 M solution in 1,4-
dioxane, 1 mL) was added. Stirring at room temperature overnight
resulted in the precipitation of a cream solid which was filtered
and washed with cold diethyl ether to give the title compound (173
mg, 51%). IR νmax (DR)/cm-1 3282, 2852, 1630, 1368, 1120, 871,
and 618; NMR δH (400 MHz, DMSO) 7.94 (1H, d, J 2.5 Hz),
7.45-7.36 (2H, m), 7.29-7.22 (2H, m), 7.21-7.16 (1H, m), and
5.71 (2H, s); m/z ) 311 [M + H]+.
Experimental Section
Flash chromatography was performed using prepacked silica gel
cartridges (Strata Si-1, 61 Å from Phenomenex, Cheshire U.K., or
IST Flash II, 54 Å from Biotage, Hertford, U.K.). Thin layer
chromatography was conducted with 5 × 10 cm plates coated with
Merck type 60 F254 silica gel to a thickness of 0.25 mm. Proton
NMR spectra were recorded on a 400 MHz Bruker spectrometer.
Solutions were typically prepared in either deuterochloroform
(CDCl3) or deuterated dimethyl sulfoxide (DMSO-d6) with chemical
shifts referenced to tetramethylsilane (TMS) as an internal standard.
Deuterated solvents were obtained from the Sigma-Aldrich Chemi-
cal Co. or Fluorochem. Microanalyses were performed by Medac
Ltd., Egham, U.K. All reagents obtained from commercial sources
were used without further purification. Anhydrous solvents were
obtained from the Sigma-Aldrich Chemical Co. Ltd. and used
without further drying. All final compounds were >95% purity as
determined by examination of both the LC chromatograms (wave-
length 235 nm) and the 1H NMR spectra, unless otherwise indicated.
Where Cl or Br was present, expected isotopic distribution patterns
were observed.
HPLC analysis conditions are described in detail in the Sup-
porting Information, along with retention times and estimated
purities of key derivatives.
7-(2-Furyl)-1H-[1,2,3]triazolo[4,5-d]pyrimidine-5-amine 4. A
solution of 7-chloro-1H-[1,2,3]triazolo[4,5-d]pyrimidine-5-amine 329
(570 mg, 3.34 mmol) in N-methyl-2-pyrrolidinone (4 mL) was
treated with PdCl2(PPh3)2 (117 mg, 0.17 mmol) and 2-(tributylstan-
nyl)furan (1.05 mL, 1 mmol), stirred at 80 °C for 5 h, diluted with
EtOAc, filtered through a silica pad, and concentrated in vacuo. The
residue was triturated with diethyl ether and the title compound
isolated as a yellow solid (438 mg, 65%). IR νmax (Nujol)/cm-1
3403, 3329, 3134, 2925, 1656, 1634, 1582, 1565, 1463 and 1377;
NMR δH (400 MHz, DMSO) 6.83-6.87 (1H, m), 7.12 (2H, s), 7.89
(1H, d, J 3.1 Hz), 8.09-8.10 (1H, m), 15.52 (1H, s); m/z ) 203 [M
+ H]+.
3-(2-Fluorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-
5-amine 5. A solution of 7-(2-furyl)-1H-[1,2,3]triazolo[4,5-d]py-
rimidine-5-amine 4 (101 mg, 0.5 mmol) in DMF (2 mL), at 0 °C,
was treated with NaH (20 mg, 60%, 0.5 mmol), stirred for 20 min,
then treated with 2-fluorobenzyl bromide (60 µL, 0.5 mmol). The
reaction mixture was allowed to warm to room temperature, stirred
for 1 h, quenched with water, extracted with EtOAc, dried (MgSO4),
and concentrated in vacuo. The crude product was purified by
chromatography (EtOAc/heptane, 1:4, to EtOAc/heptane, 2:1) to
give the title compound (34 mg, 22%) as a yellow solid. IR νmax
(Nujol)/cm-1 3480, 3312, 3195, 3118, 2925, 2854, 1652, 1609,
1581, 1487, 1456, 1436, 1027, and 759; NMR δH (400 MHz,
DMSO) 5.60 (2H, s), 6.84-6.86 (1H, m), 7.15-7.29 (3H, m),
7.32-7.43 (3H, m), 7.89 (1H, d, J 2.9 Hz), 8.12 (1H, s); m/z )
311 [M + H]+.
6-(5-Methyl-2-furyl)pyrimidine-2,4,5-triamine 7. A solution of
6-chloro-5-nitropyrimidine-2,4-diamine30 (10 g, 60% pure, 32
mmol) in THF (300 mL) was treated with saturated aqueous

42 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1
Gillespie et al.
3-(2-Fluorobenzyl)-7-(2-thiazolyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 14. A stirred solution of thiazole (0.10 mL, 1.43
mmol) in dry THF (5 mL) at -78 °C under argon was treated with
n-BuLi (0.9 mL, 1.6 M in hexanes, 1.43 mmol), stirred for 30 min,
treated with a solution of ZnCl2 (1.8 mL, 1 M in Et2O, 1.80 mmol),
and allowed to warm gradually to room temperature. The mixture
was treated with 7-chloro-3-(2-fluorobenzyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 1332 (200 mg, 0.714 mmol) and Pd(PPh3)4
(50 mg), refluxed for 2 h, and partitioned between saturated NH4Cl
(20 mL) and EtOAc (20 mL). The organic phase was dried
(MgSO4), concentrated in vacuo, and purified by chromatography
[SiO2, isohexane/EtOAc (1:1)] to give the title compound (70 mg,
30%) as a cream solid: mp 225-230 °C; IR νmax (DR)/cm-1 3520,
3344, 1734, 1611, 1438, 1240, 996, 833, and 761; NMR δH (400
MHz, DMSO) 8.26 (1H, d, J 3.0 Hz), 8.15 (1H, d, J 3.0 Hz),
7.50-7.44 (2H, br s), 7.42-7.36 (1H, m), 7.29-7.21 (1H. m),
7.21-7.15 (1H, m), and 5.73 (2H, s); m/z ) 328 [M + H]+.
3-(2-Fluorobenzyl)-7-(4-methyl-2-thiazolyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 15. 15 was prepared as described for
compound 14, using 4-methylthiazole (0.27 mL, 3 mmol, 3 equiv)
to give the compound as a pale-yellow solid after trituration from
dichloromethane (94 mg, 29%): mp 265.7-26.2 °C; IR νmax (DR)/
cm-1 3491, 3370, 3120, 1614, 1232, 972, 753, and 514; NMR δH
(400 MHz, DMSO) 7.72 (1H, s), 7.51-7.43 (2H, s), 7.42-7.35
(1H, m), 7.30-7.14 (3H, m), 5.73 (2H, s), and 2.55 (3H, s); m/z )
342 [M + H]+.
3-(2-Fluorobenzyl)-7-(5-methyl-2-thiazolyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 16. 16 was prepared as described for
compound 14, using 5-methylthiazole (0.20 mL, 3 mmol, 3 equiv)
to give the compound as a pale-yellow solid after purification by
column chromatography [SiO2, isohexane/EtOAc (1:1)] (85 mg,
35%): mp 242.0-242.1 °C; IR νmax (DR)/cm-1 3513, 3294, 1570,
1234, 999, and 755; NMR δH (400 MHz, DMSO) 7.96 (1H, s),
7.46-7.34 (3H, m), 7.30-7.13 (3H, m), 5.72 (2H, s), and 2.60
(3H, s); m/z ) 342 [M + H]+.
3-(2-Fluorobenzyl)-7-(2-oxazolyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 17. 17 was prepared as described for compound
14, using oxazole (0.14 g, 2 mmol, 2 equiv) to give the compound
as a beige solid after purification by column chromatography [SiO2,
isohexane/EtOAc (1:1), then ethyl acetate] (6 mg, 2%). NMR δH
(400 MHz, DMSO) 8.53 (1H, s), 7.69 (1H, s), 7.58 (2H, br s),
7.45-7.36 (1H, m), 7.29-7.22 (2H, m), 7.21-7.15 (1H, m), and
5.73 (2H, s); m/z ) 312 [M + H]+.
3-(2-Fluorobenzyl)-7-(2-thienyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 18. A stirred solution of 7-chloro-3H-[1,2,3]tria-
zolo[4,5-d]pyrimidine-5-amine 1332 (0.2 g, 0.71 mmol), 2-thiophene
boronic acid (0.27 g, 2.14 mmol), and Pd(PPh3)4 (0.1 g, 0.086
mmol) in THF (20 mL) and saturated aqueous sodium bicarbonate
solution (10 mL) was heated at reflux for 1 h, during which time
the solution darkened to almost black. The mixture was cooled and
partitioned between ethyl acetate and water and the organic phase
separated, dried, and concentrated in vacuo. The resultant pale-
yellow solid was triturated from isohexane/ethyl acetate, filtered,
and dried to give the title compound as a yellow solid (0.12 g,
51%): mp 174.0-174.2 °C; IR νmax (DR)/cm-1 3473, 3317, 3188,
2740, 1736, 1648, 1243, 1004, and 752; NMR δH (400 MHz,
DMSO) 8.68 (1H, dd, J 4.0, 1.5 Hz), 7.99 (1H, dd, J 5.0, 1.0 Hz),
7.43-7.35 (2H, m), 7.31-7.16 (5H, m), and 5.71 (2H, s); m/z )
327 [M + H]+.
3-(2-Fluorobenzyl)-7-(5-triazolyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 19. To a stirred solution of (1-(2-(trimethylsi-
lyl)ethoxymethyl)-1H-triazole (0.50 g, 2.50 mmol) in dry THF (10
mL) at -78 °C was slowly added n-butyllithium (1.7 mL, 1.6 M
solution in hexanes, 2.7 mmol) and, after 30 min, tributyltin chloride
(0.69 mL, 3.16 mmol). The mixture was allowed to warm slowly
to room temperature and stirred for a further 1 h. After partitioning
between ethyl acetate and water, the organic phase was dried
(magnesium sulfate) and concentrated in vacuo. Column chroma-
tography [SiO2, isohexane/EtOAc (5:1)] gave the stannyltriazole
as a clear oil. This oil (366 mg, 0.75 mmol) was redissolved in
DMF and the chlorotriazolopyrimidine 13 (145 mg, 0.5 mmol)
added. PdCl2(PPh3)2 (35 mg) was added to this solution and the
mixture shaken at 80 °C overnight. After cooling, the mixture was
applied directly to a silica gel column and purified [eluting with
isohexane/EtOAc (2:1)]. The resultant clear oil was redissolved in
methanol (1 mL) and hydrochloric acid (4 M solution in 1,4-
dioxane, 0.5 mL). After being stirred at room temperature overnight,
the mixture was concentrated in vacuo and the residue triturated
from diethyl ether to give the compound as an off-white solid (16
mg, 10%). NMR δH (400 MHz, DMSO) 8.84 (1H, br s), 7.46-7.35
(2H, m), 7.32-7.14 (4H, m), and 5.72 (2H, s); m/z ) 312 [M +
H]+.
3-(2-Fluorobenzyl)-7-(5-thiazolyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 20. 20 was prepared as described for compound
4, using 5-(tributlystannyl)thiazole (0.56 g, 1.5 mmol) and the
chlorotriazolopyrimidine 13 with other reagents scaled accordingly
and shaking for 1 h. This procedure gave the title compound as a
yellow solid after trituration from diethyl ether (183 mg, 56%). IR
νmax (DR)/cm-1 3479, 3289, 3169, 1597, 1502, 1226, 1119, 999,
880, and 757; NMR δH (400 MHz, DMSO) 9.43 (1H, s), 9.25 (1H,
s), 7.48-7.34 (3H, m) 7.30-7.22 (2H, m), 7.21-7.15 (1H, m),
and 5.72 (2H, s); m/z ) 328 [M + H]+.
General Alkylation Procedure. A solution of 7-(2-furyl)-1H-
[1,2,3]triazolo[4,5-d]pyrimidine-5-amine 4 (101 mg, 0.5 mmol) in
DMF (2 mL), at 0 °C, was treated with NaH (20 mg, 60%, 0.5
mmol), stirred for 20 min, then treated with the appropriate benzyl
bromide (0.5 mmol). The reaction mixture was allowed to warm
to room temperature, stirred for 1 h, then quenched with water,
extracted with EtOAc, dried (MgSO4), and concentrated in vacuo.
The crude product was purified by chromatography (EtOAc/heptane,
1:4, to EtOAc/heptane, 2:1)
The following derivatives were prepared using the above
methodology.
3-Benzyl-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-5-
amine 21. Yield ) 39%; IR νmax (Nujol)/cm-1 3499, 3316, 3193,
2946, 1651, and 1509; NMR δH (400 MHz, DMSO) 8.13-8.10
(1H, m), 7.90 (1H, d, J 3.5 Hz), 7.39-7.26 (7H, m), 6.87-6.84
(1H, m), and 5.67 (2H, s); m/z ) 293 [M + H]+. Anal. (C15H12N6O)
C, Η, Ν.
3-Cyclohexylmethyl-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 22. Yield ) 4%; IR νmax (Nujol)/cm-1 3316, 3193,
2926, 2851, 1637, 1508, and 1437; NMR δH (400 MHz, DMSO)
8.11-8.09 (1H, m), 7.89 (1H, dd, J 3.5, 1.0 Hz), 7.27 (2H, s),
6.86-6.83 (1H, m), 4.26 (2H, d, J 7.5 Hz), 2.04-1.90 (1H, m),
1.72-1.50 (5H, m), and 1.25-0.95 (5H, m); m/z ) 299 [M + H]+.
3-(2,3-Difluorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 23. Yield ) 20%; mp 188.8-188.9 °C; IR νmax
(Nujol)/cm-1 3492, 3302, 3189, 2951, 1635, and 1505; NMR δH
(400 MHz, DMSO) 8.14-8.10 (1H, m), 7.90 (1H, d, J 3.0 Hz),
7.47-7.32 (3H, m), 7.20 (1H, q, J 7.0 Hz), 7.05 (1H, t, J 7.0 Hz),
6.88-6.83 (1H, m), and 5.75 (2H, s); m/z ) 329 [M + H]+.
3-(2,4-Difluorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 24. Yield ) 15%; mp 207.0-207.4 °C; IR νmax
(Nujol)/cm-1 3496, 3229, 3201, 3057, 2965, 2743, 1785, and 1615;
NMR δH (400 MHz, DMSO) 8.13-8.10 (1H, m), 7.89 (1H, d, J
3.5 Hz), 7.40-7.27 (4H, m), 7.08 (1H, dt, J 8.5, 3.0 Hz), 6.87-6.84
(1H, m), and 5.66 (2H, s); m/z ) 329 [M + H]+.
3-(2,5-Difluorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 25. Yield ) 25%; mp 208.1-208.2 °C; IR νmax
(Nujol)/cm-1 3347, 3199, 2981, 2932, 2764, 2719, 1660, and 1612;
NMR δH (400 MHz, DMSO) 8.14-8.11 (1H, m), 7.90 (1H, d, J
3.5 Hz), 7.41-7.22 (4H, m), 7.15-7.09 (1H, m), 6.87-6.83 (1H,
m), and 5.69 (2H, s); m/z ) 329 [M + H]+. Anal. (C15H10F2N6O)
C, H, N.
3-(2,6-Difluorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 26. Yield ) 32%; mp 213.8 -213.9 °C; IR νmax
(DR)/cm-1 3996, 3654, 3507, 3320, 2930, 2562, 2621, 1944, 1837,
1676, 1428, 1230, 1095, 1026, and 797; NMR δH (400 MHz,
DMSO) 5.65 (2H, s), 6.81-6.86 (1H, m), 7.16 (2H, t, J 8.5 Hz),
7.31 (2H, s), 7.44-7.56 (1H, m), 7.86 (1H, dd, J 3.5, 1.0 Hz),
8.07-8.13 (1H, m); m/z ) 329 [M + H]+. Anal. (C15H10N6OF2)
C, H, N.

Triazolo[4,5-d]pyrimidine A2A Antagonists
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1 43
3-(3-Chlorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 27. Yield ) 19%; mp 209.9-210.1 °C; IR νmax (DR)/
cm-1 3504, 3312, 3201, 2948, 1611, 1503, 1435, 1279, 1220, 1025,
and 755; NMR δH (400 MHz, DMSO) 5.69 (2H, s), 6.82-6.87
(1H, m), 7.19-7.25 (1H, m), 7.33 (2H, s), 7.37-7.40 (3H, m),
7.90 (1H, d, J 3.5 Hz), 8.10-8.13 (1H, m); m/z ) 328 [M + H]+.
Anal. (C15H11N6OCl) C, H, N.
7-(2-Furyl)-3-(2-methylbenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 28. Yield ) 9%; mp 218.0-218.1 °C; IR νmax (DR)/
cm-1 3999, 3376, 3209, 2916, 2747, 2326, 1957, 1782, 1610, 1515,
1278, 1023, and 763; NMR δH (400 MHz, DMSO) 2.42 (3H, s),
5.64 (2H, s), 6.86 (1H, s), 6.91 (1H, d, J 7.5 Hz), 7.13 (1H, t, J 7.0
Hz), 7.17-7.26 (2H, m), 7.32 (2H, s), 7.90 (1H, d, J 3.5 Hz), 8.12
(1H, s); m/z ) 307 [M + H]+.
7-(2-Furyl)-3-(3-methylbenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 29. Yield ) 20%; mp 187.3-187.7 °C; IR νmax (DR)/
cm-1 3993, 3489, 3319, 3197, 2951, 2725, 2353, 1954, 1719, 1633,
1604, 1503, 1420, 1232, 1032, and 740; NMR δH (400 MHz,
DMSO) 2.27 (3H, s) 5.62 (2H, s), 6.82-6.88 (1H, m), 7.02-7.16
(3H, m), 7.24 (1H, t, J 7.5 Hz), 7.33 (2H, s), 7.90 (1H, d, J 3.5
Hz), 8.12 (1H, s); m/z ) 307 [M + H]+.
7-(2-Furyl)-3-(3-trifluoromethylbenzyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 30. Yield ) 7%; IR νmax (Nujol)/cm-1 3379,
3336, 3208, 1655, 1604, 1513, 1456, 1325, 11687, 1124, 1025,
and 755; NMR δH (400 MHz, DMSO) 5.79 (2H, s), 6.83-6.88
(1H, m), 7.36 (2H, s), 7.53 (1H, d, J 7.5 Hz), 7.60 (1H, t, J 7.5
Hz), 7.67-7.76 (2H, m), 7.91 (1H, d, J 3.5 Hz), 8.13 (1H, s); m/z
) 361 [M + H]+. Anal. (C16H11F3N6O) C, H, N.
7-(2-Furyl)-3-(2-methoxybenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 31. 31 was prepared using Cs2CO3 (1 equiv) in place
of sodium hydride. Yield ) 25%; mp 212.1-214.3 °C; IR νmax
(DR)/cm-1 4007, 3474, 3323, 3199, 2934, 2747, 2105, 1647, 1603,
1492, 1245, 1028, and 754; NMR δH (400 MHz, DMSO) 3.82 (3H,
s), 5.60 (2H, s), 6.78-6.93 (3H, m), 7.05 (1H, d, J 8.5 Hz),
7.24-7.38 (3H, m), 7.90 (1H, d, J 3.0 Hz), 8.12 (1H, s); m/z )
323 [M + H]+.
7-(2-Furyl)-3-(3-methoxybenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 32. Yield ) 40%; IR νmax (Nujol)/cm-1 3327, 3207,
2924, 2854, 1650, 1602, 1583, 1566, 1513, and 1487; NMR δH
(400 MHz, DMSO) 3.72 (3H, s), 5.63 (2H, s), 6.80 (1H, d, J 7.5
Hz), 6.85-6.89 (3H, m), 7.26 (1H, t, J 7.5 Hz), 7.33 (2H, s), 7.90
(1H, d, J 3.5 Hz), 8.11 (1H, s); m/z ) 323 [M + H]+; Anal.
(C16H14N6O2) C, H, N.
3-(3-Cyanobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-
5-amine 33. Yield ) 15%; IR νmax (Nujol)/cm-1 3490, 3307, 3189,
2230, 1959, 1728, 1642, 1611, 1583, 1565, 1463, 1377, 1283, 1234,
1030, and 761; NMR δH (400 MHz, DMSO) 5.75 (2H, s),
6.82-6.89 (1H, m), 7.35 (2H, s), 7.57-7.59 (2H, m), 7.79-7.81
(2H, m), 7.91 (1H, d, J 3.5 Hz), 8.12 (1H, s); m/z ) 318 [M +
H]+. Anal. (C16H11N7O) C, H, N.
3-(4-Cyanobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-
5-amine 34. Yield ) 13%; mp 292.3-292.4 °C; IR νmax (DR)/
cm-1 3324, 3207, 2098, 1602, 1527, 1352, 1024, and 813; NMR
δH (400 MHz, CDCl3) 8.10 (1H, d, J 3.0 Hz), 7.79 (1H, d, J 1.5
Hz), 7.64 (2H, d, J 8.5 Hz), 7.49 (2H, d, J 8.5 Hz), 6.71 (1H, dd,
J 3.5, 1.5 Hz), 5.71 (2H, s), and 5.38 (2H, br s); m/z ) 318 [M +
H]+.
7-(2-Furyl)-3-(4-nitrobenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-
5-amine 37. Yield ) 14%; mp 240.9-241.1 °C. IR νmax (DR)/
cm-1 4010, 3629, 3499, 3313, 3196, 2946, 2733, 2447, 1943, 1638,
1528, 1420, 1351, 1222, 1025, and 960. NMR δH (400 MHz,
DMSO) 5.85 (2H, s), 6.84-6.89 (1H, m), 7.36 (2H, s), 7.50 (2H,
dt, J 8.5, 2.0 Hz), 7.92 (1H, dd, J 3.5, 1.0 Hz), 8.12-8.14 (1H, m),
8.22 (2H, dt, J 9.0, 2.0 Hz); m/z ) 338 [M + H]+. Anal.
(C15H11N7O3) C, H, N.
Methyl 3-(5-Amino-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
din-3-yl)methylbenzoate 38. Yield ) 21%; IR νmax (Nujol)/cm-1
3405, 3328, 3211, 3155, 2925, 2854, 1719, 1603, 1577, 1463, 1023,
and 731; NMR δH (400 MHz, DMSO) 3.84 (3H, s), 5.76 (2H, s),
6.85-6.87 (1H, m), 7.33-7.38 (2H, s), 7.50-7.59 (2H, m),
7.89-7.92 (3H, s), 8.12-8.13 (1H, m); m/z ) 351 [M + H]+. Anal.
(C17H14N6O3) C, H, N.
7-(2-Furyl)-3-(3-hydroxybenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 39. A solution of 7-(2-furyl)-3-(3-methoxybenzyl)-
3H-[1,2,3]triazolo[4,5-d]pyrimidine-5-amine 32 (119 mg, 0.37
mmol) in dichloromethane (20 mL) at 0 °C was treated with boron
tribromide (1 M in dichloromethane, 8.8 mL, 8.8 mmol) portionwise
over 3 days, concentrated in vacuo, and isolated by filtration to
give the title compound (114 mg, 100%) as a yellow solid. IR νmax
(Nujol)/cm-1 3451, 3206, 2361, 2261, 1655, 1604, 1459, 1378,
1195, 1028, and 774; NMR δH (400 MHz, DMSO) 5.57 (2H, s),
6.57-6.63 (1H, m), 6.65-6.74 (2H, m), 6.83-6.88 (1H, m), 7.14
(1H, t, J 7.5 Hz), 7.91 (1H, d, J 3.0 Hz), 8.12 (1H, d, J 1.0 Hz);
m/z ) 309 [M + H]+.
3-(5-Amino-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-3-yl-
methyl)benzoic Acid 40. A solution of methyl 3-(5-amino-7-(2-
furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-3-yl)methylbenzoate 38
(771 mg, 2.2 mmol) in MeOH (20 mL) was treated with aqueous
NaOH (2 M, 2 mL, 4 mmol), refluxed for 10 min, cooled, acidified
with aqueous HCl (1M), filtered, and dried to give the title
compound (723 mg, 98%) as a white solid. IR νmax (Nujol)/cm-1
3324, 3206, 1698, 1650, and 1611; NMR δH (400 MHz, DMSO)
13.56-12.46 (1H, s), 8.13-8.11 (1H, s), 7.92-7.84 (3H, m),
7.56-7.31 (3H, m), 6.87-6.85 (1H, m), and 7.74 (2H, s); m/z )
337 [M + H]+.
3-(5-Amino-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-3-yl-
methyl)benzamide 41. A suspension of 3-(5-amino-7-(2-furyl)-3H-
[1,2,3]triazolo[4,5-d]pyrimidin-3-ylmethyl)benzoic acid 40 (168 mg,
0.5 mmol) in DMF (1 mL) was treated with carbonyl diimidazole
(81 mg, 0.5 mmol), stirred at room temperature for 1 h, and treated
with ammonium hydroxide (1 mL) and the mixture stirred at room
temperature for 16 h. The reaction mixture was cooled, diluted with
water (3 mL), and filtered to give the title compound (111 mg,
66%) as a cream solid. IR νmax (Nujol)/cm-1 3324, 1644, 1491,
and 1417; NMR δH (400 MHz, DMSO) 8.12 (1H, s), 7.98-7.93
(1H, s), 7.91 (1H, d, J 3.0 Hz), 7.81 (1H, d, J 6.5 Hz), 7.77 (1H,
s), 7.47-7.29 (5H, m), 6.86 (1H, s), and 5.77-5.68 (2H, m); m/z
) 336 [M + H]+.
The following amides were prepared using the above methodol-
ogy, employing the appropriate amines.
3-(5-Amino-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-3-yl-
methyl)-N-isopropylbenzamide 42. Yield ) 58%; IR νmax (Nujol)/
cm-1 3298, 2972, 1635, and 1418; NMR δH (400 MHz, DMSO)
8.21 (1H, d, J 7.5 Hz), 8.12 (1H, s), 7.91 (1H, d, J 3.0 Hz),
7.82-7.74 (2H, m), 7.48-7.29 (4H, m), 6.86 (1H, s), 5.71 (2H,
s), 4.13-4.01 (1H, m), and 1.13 (6H, d, J 6.5 Hz); m/z ) 378 [M
+ H]+.
3-(5-Amino-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-3-yl-
methyl)-N-isopropyl-N-methylbenzamide 43. Yield ) 23%; IR νmax
(Nujol)/cm-1 3480, 3322, 3202, 283, 1608, and 1506; NMR δH
(400 MHz, DMSO) 8.12 (1H, s), 7.90 (1H, d, J 3.5 Hz), 7.47-7.25
(5H, m), 6.87-6. 84 (1H, m), 5.72 (2H, s), 3.77-3.61 (1H, s),
2.76 (3H, s), 1.10 (3H, s), and 0.99 (3H, s); m/z ) 392 [M + H]+.
(2-Amino-6-(2-furyl)-5-nitropyrimidin-4-yl) 4-Methylbenzene-
sulfonate 45. A suspension of 2-amino-6-(2-furyl)-5-nitropyrimi-
dine-4(1H)-one 4434 (1.00 g, 4.50 mmol) in dichloromethane (50
mL) was treated with triethylamine (0.941 mL, 6.75 mmol) and
p-toluenesulfonyl chloride (944 mg, 4.95 mmol), stirred for 1 h,
7-(2-Furyl)-3-(2-nitrobenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-
5-amine 35. Yield ) 21%; IR νmax (Nujol)/cm-1 3374, 3311, 3202,
1636, 1606, 1586, 1530, 1511, 1465, 1439, 1377, and 1343; NMR
δH (400 MHz, DMSO) 6.03 (2H, s), 6.86-6.89 (1H, m), 6.98 (1H,
d, J 7.5 Hz), 7.36 (2H, s), 7.60-7.73 (2H, m), 7.92 (1H, d, J 3.5
Hz), 8.14 (1H, s), 8.2 (1H, d, J 8.0 Hz); m/z ) 338 [M + H]+.
Anal. (C15H11N7O3) C, H, N.
7-(2-Furyl)-3-(3-nitrobenzyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-
5-amine 36. Yield ) 9%; mp 221.0-221.1 °C; IR νmax (Nujol)/
cm-1 3470, 3310, 3191, 3144, 2924, 2854, 1642, 1610, 1521, 1463,
and 1354; NMR δH (400 MHz, DMSO) 5.85 (2H, s), 6.87 (1H, s),
7.37 (2H, s), 7.63-7.73 (2H, m), 7.91 (1H, d, J 2.8 Hz), 8.13 (1H,
s), 8.18 (1H, s), 8.20 (1H, s); m/z ) 338 [M + H]+. Anal.
(C15H11N7O3) C, H, N.

44 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1
Gillespie et al.
diluted with dichloromethane (50 mL), washed with 2 M HCl (20
mL), dried (MgSO4), concentrated in vacuo, and purified by
chromatography [SiO2, isohexane/EtOAc (2:1)] to give the title
compound (410 mg, 24%) as a yellow solid. NMR δH (400 MHz,
CDCl3) 7.95 (2H, d, J 8.5 Hz), 7.59-7.57 (1H, m), 7.39 (2H, d, J
8.5 Hz), 7.23-7.21 (1H, m), 6.59-6.51 (1H, m), 5.39 (2H, br s),
2.48 (3H, s).
7-(2-Furyl)-3-(2-pyridylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 46. A solution of (2-amino-6-(2-furyl)-5-nitropyri-
midin-4-yl) 4-methylbenzenesulfonate 45 (478 mg, 1.27 mmol) in
dimethoxyethane (15 mL) was treated with triethylamine (0.531
mL, 3.81 mmol) and 2-pyridinemethylamine (0.393 mL, 3.81
mmol), stirred for 16 h, and poured into water (100 mL), and the
resulting solid was filtered to give 6-(2-furyl)-5-nitro-N4-(2-py-
ridylmethyl)pyrimidine-2,4-diamine (275 mg, 69%) as a yellow
solid. NMR δH (400 MHz, CDCl3) 8.70-8.58 (2H, m), 7.70-7.66
(1H, m), 7.55-7.54 (1H, m), 7.28 (1H, d, J 8.0 Hz), 7.24-7.20
(1H, m), 7.07-7.06 (1H, m), 6.54-6.52 (1H, m), 5.26 (2H, br s),
and 4.83 (2H, d, J 5.0 Hz)
A mixture of this material and 10% Pd/C (92 mg, 0.086 mmol)
in EtOH (30 mL) and EtOAc (10 mL) was stirred under a hydrogen
atmosphere for 1 h, filtered through Celite, and concentrated in
vacuo. The resulting yellow oil was dissolved in 1,4-dioxane (25
mL), treated with isoamyl nitrite (0.109 mL, 0.815 mmol), stirred
at 100 °C for 6 h, cooled to room temperature, filtered through
Celite, concentrated in vacuo, and triturated with Et2O to give the
title compound (110 mg, 46%) as a yellow solid: mp 196.9-197.1
°C; IR νmax (DR)/cm-1 3448, 3321, 3200, 1649, 1616, 1509, 1488;
NMR δH (400 MHz, DMSO) 8.49-8.47 (1H, m), 8.12-8.11 (1H,
m), 7.91 (1H, d, J 3.5 Hz), 7.81-7.77 (1H, m), 7.34-7.30 (1H,
m), 7.27 (2H, br s), 7.24 (1H, d, J 8.0 Hz), 6.86-6.85 (1H, m),
5.77 (2H, s); m/z ) 294 [M + H]+.
7-(2-Furyl)-3-(3-pyridylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 47. 47 was prepared as described for compound 46
from 44 using 3-pyridinemethylamine (0.357 mL, 3.51 mmol) and
other reagents scaled accordingly, to give the compound as a yellow
solid (103 mg, 50%). IR νmax (DR)/cm-1 3326, 3211, 2956, 2856,
1641, 1612, 1507, 1491; NMR δH (400 MHz, CDCl3) 8.77-8.76
(1H, m), 8.58-8.56 (1H, m), 8.08 (1H, d, J 3.5 Hz), 7.78 (1H, m),
7.75-7.72 (1H, m), 7.29-7.25 (1H, m), 6.71-6.69 (1H, m), 5.68
(2H, s), 5.37 (2H, br s); m/z ) 294 [M + H]+. Anal. (C14H11N7O)
C, H, N.
Hz), and 5.66-5.64 (2H, s); m/z ) 299 [M + H]+. Anal.
(C13H10N6OS) C, H, N.
3-(2-Aminobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 52. A solution of 7-(2-furyl)-3-(2-nitrobenzyl)-3H-
[1,2,3]triazolo[4,5-d]pyrimidine-5-amine 35 (472 mg, 1.4 mmol)
in EtOH (10 mL) at 50 °C was treated with a solution of SnCl2
(947 mg, 4.2 mmol) in concentrated HCl (1.6 mL), stirred for 2 h,
cooled, diluted with water, basified to pH 10 (5 M, NaOH), and
filtered to give the title compound (287 mg, 67%) as an off-white
solid. IR νmax (Nujol)/cm-1 3489, 3313, 3191, 1638, 1603, 1505,
1460, and 1378; NMR δH (400 MHz, DMSO) 5.27 (2H, s), 5.47
(2H,s), 6.50 (1H, t, J 7.5 Hz), 6.67-6.78 (2H, m), 6.86 (1H, s),
7.01 (1H, t, J 7.0 Hz), 7.36 (2H, s), 7.90 (1H, d, J 3.0 Hz), 8.12
(1H, s); m/z ) 308 [M + H]+.
Similarly prepared were the following compounds.
3-(3-Aminobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 53. 53 was prepared from compound 36. Yield )
92%; mp 259.8-259.9 °C; IR νmax (Nujol)/cm-1 3452, 3367, 3318,
3185, 3142, 2922, 1651, 1602, 1514, 1463, and 1377; NMR δH
(400 MHz, DMSO) 5.09 (2H, s), 5.49 (2H, s), 6.35 (1H, s), 6.41
(1H, d, J 7.5 Hz), 6.45 (1H, d, J 8.0 Hz), 6.85-6.86 (1H, m), 6.96
(1H, t, J 8.0 Hz), 7.30 (2H, s), 7.90 (1H, d, J 3.5 Hz), 8.11 (1H, s);
m/z ) 308 [M + H]+. Anal. (C15H13N7O) C, H, N.
3-(4-Aminobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 54. 54 was prepared from compound 37. Yield )
45%; mp 240.3-240.4 °C. IR νmax (DR)/cm-1 3320, 3198, 2929,
1610, 1505, 1438, 1280, 1233, 1028, 956, and 759; NMR δH (400
MHz, DMSO) 5.85 (2H, s), 6.84-6.89 (1H, m), 7.36 (2H, s), 7.50
(2H, dt, J 8.5, 2.0 Hz), 7.92 (1H, dd, J 3.5, 1.0 Hz), 8.12-8.14
(1H, m), 8.22 (2H, dt, J 9.0 Hz); m/z ) 308 [M + H]+.
3-(4-Aminomethylbenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]py-
rimidine-5-amine 55. 4-Hydroxymethylbenzonitrile (1.33 g, 10
mmol) and ammonium hydroxide (1 mL) were dissolved in ethanol
(20 mL), and catalytic Raney nickel was added. The reaction vessel
was evacuated, placed under an atmosphere of hydrogen, then
shaken at room temperature overnight. After filtration through Celite
and concentration in vacuo, the resultant off-white solid (1.10 g,
80%) was redissolved in THF and triethylamine (1.12 mL, 8 mmol)
added. After stirring at room temperature for 10 min, di-tert-butyl
dicarbonate (1.84 g, 8 mmol) was added and the reaction stirred
for a further 90 min. The reaction mixture was then partitioned
between saturated aqueous ammonium chloride solution and ethyl
acetate, and the organic phase was separated, dried (magnesium
sulfate), and concentrated to dryness to give the N-protected benzyl
alcohol 56 as a white solid (1.70 g, 89%) which was used without
further purification. NMR δH (400 MHz, DMSO) 7.35 (1H, t, J
6.0 Hz), 7.24 (2H, d, J 8.0 Hz), 7.17 (2H, d, J 8.0 Hz), 5.13 (1H,
t, J 5.7 Hz), 4.46 (2H, d, J 5.7 Hz), 4.08 (2H, d, J 6.0 Hz)
This material (1.65 g, 6.96 mmol) was then mixed with
triphenylphosphine (2.19 g, 10.4 mmol) in dichloromethane (50
mL) at 0 °C and treated portionwise with CBr4 (3.46 g, 10.4 mmol),
stirred for 1 h, concentrated in vacuo, and purified by chromatog-
raphy [SiO2, isohexane/EtOAc (5:1)] to give the corresponding
protected bromide 57 (1.35 g, 65%). NMR δH (400 MHz, DMSO)
7.41 (1H, br t), 7.38 (2H, d, J 8.0 Hz), 7.21 (2H, d, J 8.0 Hz), 4.68
(2H, s), 4.11 (2H, d, J 6.2 Hz), 1.39 (9H, s)
The following derivative was also prepared using the general
alkylation methodology outlined above.
7-(2-Furyl)-3-(2-pyrazinylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 48. Yield ) 16%; mp 129.1-131.0 °C; IR νmax
(DR)/cm-1 3993, 3470, 3310, 3197, 1610, 1508, 1420, 1239, 1002,
and 796; NMR δH (400 MHz, DMSO) 8.74 (1H, d, J 1.5 Hz), 8.61
(1H, d, J 2.5 Hz), 8.57-8.54 (1H, m), 8.13-8.11 (1H, m), 7.91
(1H, d, J 3.5 Hz), 7.31 (2H, br s), 6.86 (1H, dd, J 3.5, 2.0 Hz), and
5.88 (2H, s); m/z ) 295 [M + H]+.
7-(2-Furyl)-3-(2-furylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidine-
5-amine 49. Yield ) 18%; IR νmax (Nujol)/cm-1 3495 and 3304;
NMR δH (400 MHz, DMSO) 8.14-8.12 (1H, m), 7.90-7.88 (1H,
dd, J 1.0, 3.5 Hz), 7.64-7.62 (1H, dd, J 1.0, 2.0 Hz), 7.43-7.37
(2H, s), 6.87-6.84 (1H, dd, J 1.5, 3.5 Hz), 6.51-6.48 (1H, dd, J
1.0, 3.5 Hz), 6.46-6.44 (1H, dd, J 2.0, 3.5 Hz), and 5.67-5.65
(2H, s); m/z ) 283 [M + H]+. Anal. (C13H10N6O2) C, H, N.
7-(2-Furyl)-3-(2-thienylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 50. Yield ) 11%; mp 204.1-204.2 °C; IR νmax (DR)/
cm-1 3490, 3321, 3200, 2923, 2711, 2490, 1749, 1605, 1502, 1376,
1272, 1034, and 761; NMR δH (400 MHz, DMSO) 5.83 (2H, s),
6.83-6.86 (1H, m), 7.01 (1H, dd, J 5.0, 3.5 Hz), 7.16 (1H, dd, J
3.5, 1.0 Hz), 7.34 (2H, s), 7.48 (1H, dd, J 5.0, 1.5 Hz), 7.89 (1H,
d, J 3.5 Hz), 8.09-8.12 (1H, m); m/z ) 299 [M + H]+.
7-(2-Furyl)-3-(3-thienylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 51. Yield ) 11%; mp 215.8-216.9 °C; IR νmax
(Nujol)/cm-1 3482 and 3305; NMR δH (400 MHz, DMSO)
8.13-8.11 (1H, m), 7.91-7.89 (1H, d, J 3.5 Hz), 7.55-7.52 (1H,
dd, J 3.0, 5.0 Hz), 7.42-7.40 (1H, m), 7.39-7.34 (2H, s),
7.11-7.08 (1H, dd, J 1.5, 5.0 Hz), 6.87-6.85 (1H, dd J 1.5, 3.5
Alkylation of the triazolopyrimidine 4 with this material (600
mg, 2 mmol) under our standard procedure described above was
followed by dissolution in methanol (30 mL) and addition of
hydrochloric acid (4 M solution in 1,4-dioxane). After stirring at
room temperature overnight, the resultant mixture was concentrated
to dryness and triturated from diethyl ether to yield the title
compound as a yellow solid (57 mg, 12%): mp >300 °C dec; IR
ν
max (DR)/cm-1 2903, 2030, 1606, 1464, 1033, 779, and 589; NMR
δH (400 MHz, DMSO) 8.30 (2H, br s), 8.14 (1H. s), 7.92 (1H, d,
J 3.5 Hz), 7.46 (2H, d, J 8.0 Hz), 7.32 (2H, d, J 8.0 Hz), 6.92-6.84
(1H, m), 5.69 (2H, s), and 4.04-3.96 (2H, m); m/z ) 322 [M +
H]+.
The following were prepared via alkylation of the furyltriazol-
opyrimidine 4 with commercially available substituted 4-nitrobenzyl

Triazolo[4,5-d]pyrimidine A2A Antagonists
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1 45
bromides, followed by reduction with tin(II) chloride, as per
compound 53.
(20 mL), washed with saturated NaHCO3 (10 mL) and 10% citric
acid solution (10 mL), dried (MgSO4), and concentrated in vacuo
to give tert-butyl (5-hydroxymethyl-2-nitrophenyl)carbonate 71
(1.36 g, 86%) as a cream solid. This material was then combined
with triphenylphosphine (2.13 g, 8.25 mmol) in dichloromethane
(50 mL) at 0 °C and treated portionwise with CBr4 (3.36 g, 10.11
mmol), stirred for 1 h, concentrated in vacuo, and purified by
chromatography [SiO2, isohexane/EtOAc (3:1)] to give the corre-
sponding protected bromide 72 as a yellow oil (961 mg, 58%).
NMR δH (400 MHz, CDCl3) 8.09 (1H, d, J 8.4 Hz), 7.41 (1H, dd,
J 8.4, 2.0 Hz), 7.34 (1H, d, J 2.0 Hz), 4.47 (2H, s), and 1.58 (9H,
s).
Alkylation of the furyl triazolopyrimidine 4 (899 mg, 4.55 mmol)
with this material (989 mg, 2.52 mmol) gave 415 mg (32%) of a
yellow solid. Tin(II) chloride reduction of this material (226 mg,
0.5 mmol), as described above, gave the title compound as a brown
solid (126 mg, 78%): mp 239.6-239.8 °C; IR νmax (Nujol)/cm-1
3323, 2936, 2733, 1772, 1734, 1609, 1508, and 1282; NMR δH
(400 MHz, DMSO) 9.07 (1H, s), 8.13-8.11 (1H, m), 7.89 (1H, d,
J 3.5 Hz), 7.34 (2H, s), 6.87-6.84 (1H, m), 6.59-6.50 (3H, m),
5.41 (2H, s), and 4.57 (2H, s); m/z ) 324 [M + H]+.
7-(2-Furyl)-3-(4-(N-methylamino)benzyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 64. To a stirred solution of 4-(methylami-
no)benzoic acid 73 (5 g, 33.1 mmol) in THF (30 mL) was added
diisopropylethylamine (14.4 mL, 36.4 mmol) and di-tert-butyl
dicarbonate (8.36 mL, 36.4 mmol) and the mixture stirred at reflux
for 48 h. After cooling, the mixture was diluted with ethyl acetate
and washed sequentially with an aqueous solution of citric acid
(10% w/v), water, and brine, then dried (magnesium sulfate) and
concentrated in vacuo to give the N-protected benzoic acid 74 as
a cream solid (5.87 g, 69%). NMR δH (400 MHz, DMSO) 12.78
(1H, s), 7.89 (2H, d, J 8.6 Hz), 7.41 (2H, 2H, d, J 8.6 Hz), 3.22
(3H, s), 1.41 (9H, s)
This material was redissolved in THF (50 mL) and cooled to 0
°C before N-methylmorpholine (5.06 mL, 46 mmol) and isobutyl
chloroformate (3.02 mL, 23.25 mmol) were added. After the mixture
was stirred at 0 °C for 15 min, a cooled (-78 °C) solution of sodium
borohydride (1.75 g, 46 mmol) in methanol (30 mL) was added
dropwise. The mixture was allowed to warm slowly to room
temperature and was stirred for a further 2 h. The reaction mixture
was diluted with ethyl acetate and washed sequentially with an
aqueous solution of citric acid (10% w/v), saturated aqueous sodium
bicarbonate solution, water, and brine, then dried (magnesium
sulfate) and concentrated in vacuo to give the benzyl alcohol 75 as
a clear, dark-orange oil (1.21 g, 22%). NMR δH (400 MHz, DMSO)
7.27 (2H, d, J 8.5 Hz), 7.21 (2H, d, J 8.5 Hz), 5.16 (1H, t, J 5.7
Hz), 4.46 (2H, d, J 5.7 Hz), 3.15 (3H, s), 1.38 (9H, s)
This material was then mixed with triphenylphosphine (2.01 g,
7.67 mmol) in dichloromethane (10 mL) at 0 °C. The resultant
solution was treated portionwise with CBr4 (2.20 g, 6.64 mmol),
warmed to room temperature, and stirred for 2 h. After concentration
in vacuo, column chromatography [SiO2, heptane/EtOAc (10:1)]
yielded the corresponding protected bromide 76 (669 mg, 43%).
NMR δH (400 MHz, DMSO) 7.40 (2H, d, J 8.5 Hz), 7.25 (2H, d,
J 8.5 Hz), 4.69 (2H, s), 3.17 (3H, s), 1.39 (9H, s)
Alkylation of the furyltriazolopyrimidine 4 (200 mg, 1 mmol)
with this material (654 mg, 2.20 mmol) proceeded as per the
standard methodology described above. A portion of the resultant
material (82 mg, 0.19 mmol) was dissolved in a mixture of 1,4-
dioxane (5 mL) and hydrochloric acid (4 M solution in 1,4-dioxane,
0.07 mL, 0.28 mmol). After being stirred at room temperature
overnight, the reaction mixture was concentrated in vacuo and the
resultant yellow solid washed with cold diethyl ether to yield the
title compound (17 mg, 23%). NMR δH (400 MHz, DMSO)
8.14-8.12 (1H, m), 7.92-7.89 (1H, dd, J 1.0, 3.5 Hz), 7.35-7.31
(2H, d, J 8.5 Hz), 7.28-7.16 (2H, s), 6.88-6.85 (1H, dd, J 1.5,
3.5 Hz), 5.66-5.64 (2H, s), and 2.82-2.80 (3H, s); m/z ) 322 [M
+ H]+.
3-(4-Amino-2-fluorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 58. Yield ) 17%; NMR δH (400 MHz,
DMSO) 8.11-8.09 (1H, m), 7.89-7.86 (1H, dd, J 1.0, 3.5 Hz),
7.32-7.27 (2H, s), 7.22-6.95 (1H, t, J 9.0 Hz), 6.85-6.83 (1H,
dd, J 2.0, 3.5 Hz), 6.35-6.29 (2H, m), 5.48-5.46 (2H, s), and
5.46-5.44 (2H, s); m/z ) 326 [M + H]+.
3-(4-Amino-3-fluorobenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 59. Yield ) 57%; mp >200 °C dec; IR νmax
(DR)/cm-1 2816, 2004, 1660, 1507, 1427, 1277, 1030, 746, and
524; NMR δH (400 MHz, DMSO) 8.15-8.12 (1H, m), 7.91 (1H,
d, J 3.5 Hz), 7.14 (1H, d, J 12.0 Hz), 7.06-6.94 (2H, m), 6.86
(1H, dd, J 3.5, 2.0 Hz), and 5.57 (2H, s); m/z ) 326 [M + H]+.
3-(4-Amino-3-methylbenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 60. Yield ) 63%; mp 245.3-246.1 °C; IR
ν
max (DR)/cm-1 4010, 3406, 3320, 3198, 2929, 2746, 1608, 1507,
1414, 1285, 1022, and 753; NMR δH (400 MHz, DMSO) 2.00 (3H,
s), 4.86 (2H, s), 5.42 (2H, s), 6.54 (1H, d, J 8.0 Hz), 6.82-6.85
(1H, m), 6.90 (1H, dd, J 8.0, 2.0 Hz), 6.92-6.95 (1H, m), 7.29
(2H, s), 7.88 (1H, d, J 3.5 Hz), 8.09-8.12 (1H, m); m/z ) 322 [M
+ H]+. Anal. (C16H15N7O) C, H, N.
3-(4-Amino-3-ethylbenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 61. A solution of 4-nitrobenzyl bromide 65
(2.16 g, 10 mmol) in THF (40 mL) at -70 °C was treated dropwise
with ethylmagnesium chloride (5 mL, 2 M in Et2O, 10 mmol),
stirred for 1 h, treated with DDQ (2.5 g, 11 mmol), and stirred at
room temperature for 16 h. The reaction mixture was poured into
water (10 mL), extracted with EtOAc (2 × 10 mL), dried (MgSO4),
concentrated in vacuo, and filtered. The resulting solid was purified
by chromatography [SiO2, EtOAc/hexane (1:9)] to give the benzyl
bromide (968 mg, 40%) as an orange oil which was used without
further purification. NMR δH (400 MHz, CDCl3) 7.87 (1H, d, J
8.3 Hz), 7.37 (1H, s), 7.35 (1H, d, J 8.3 Hz), 4.47 (2H, s), 2.92
(2H, q, J 7.5 Hz), and 1.30 (3H, t, J 7.5 Hz).
Alkylation and tin(II) chloride reduction using the standard
procedures described above gave the title compound (100 mg, 6%
over two steps) as a cream powder. IR νmax (DR)/cm-1 3427, 3318,
3201, 2966, 1605, 1503, 1415, 1281, 1027, and 762; NMR δH (400
MHz, DMSO) 1.08 (3H, t, J 7.0 Hz), 2.39 (2H, q, J 7.0 Hz), 4.91
(2H, s), 5.44 (2H, s), 6.54 (1H, d, J 8.0 Hz), 6.80-9.62 (2H, m),
6.97 (1H, s), 7.34 (2H, s), 7.89 (1H, s), 8.12 (1H, s); m/z ) 336
[M + H]+. Anal. (C17H17N7O) C, H, N.
3-(4-Amino-3-isopropylbenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 62. 62 was prepared as for 61 using isopro-
pylmagnesium chloride to give the title compound as an orange
oil (505 mg, 10%). IR νmax (DR)/cm-1 3480, 3379, 3199, 2958,
2761, 2104, 1879, 1776, 1659, 1516, 1439, 1334, 1024, 762, and
575; NMR δH (400 MHz, DMSO) 1.10 (6H, d, J 7.0 Hz), 2.92
(1H, sept, J 6.5 Hz), 4.93 (2H, s), 5.44 (2H, s), 6.54 (1H, d, J 8.0
Hz), 6.80-6.88 (2H, m), 7.09 (1H, d, J 2.0 Hz), 7.34 (2H, s), 7.88
(1H, d, J 3.5 Hz), 8.10-8.13 (1H, m); m/z ) 350 [M + H]+. Anal.
(C18H19N7O) C, H, N.
3-(4-Amino-3-hydroxybenzyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 63. A solution of 3-hydroxy-4-nitrobenzoic
acid 69 (1.83 g, 10 mmol) in THF (10 mL) was treated with Et3N
(3.4 mL, 24 mmol) and di-tert-butyl dicarbonate (2.40 mL, 11
mmol) and the mixture stirred at room temperature for 16 h. The
reaction mixture was poured into 10% citric acid solution (20 mL),
extracted with EtOAc (2 × 10 mL), dried (MgSO4), and concen-
trated in vacuo to give the protected benzoic acid 70 (2.36 g, 83%)
as a cream solid. IR νmax (Nujol)/cm-1 2985, 1772, 1717, and 1592;
NMR δH (400 MHz, DMSO) 13.85 (1H, s), 8.26 (1H, d, J 8.5
Hz), 8.04 (1H, dd, J 8.5, 2.0 Hz), 7.98 (1H, d, J 2.0 Hz), and 1.49
(9H, s).
The acid (2.26 g, 8 mmol) and N-methylmorpholine (1.85 mL,
16.8 mmol) in THF (20 mL) at 0 °C were treated with isobutyl
chloroformate (1.09 mL, 8.4 mmol), and the mixture was stirred
for 1 h. The mixture was added to a cooled (-78 °C) solution of
NaBH4 (605 mg, 16 mmol) in MeOH (16 mL) and stirred at room
temperature for 1 h. The reaction mixture was diluted with EtOAc
N-(4-(5-Amino-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-3-
ylmethyl)phenyl)acetamide 77. 77 was prepared via alkylation with
the corresponding commercial benzyl bromide as described above,

46 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1
Gillespie et al.
to give the title compound as a cream powder (42 mg, 6%): mp
253.6-254.0 °C; IR νmax (DR)/cm-1 3320, 1611, 1414, 1315, 1255,
1026, and 767; NMR δH (400 MHz, DMSO) 2.01 (3H, s), 5.59
(2H, s), 6.84-6.88 (1H, m), 7.22 (2H, d, J 8.5 Hz), 7.36 (2H, s),
7.54 (2H, d, J 8.5 Hz), 7.90 (1H, d, J 3.5 Hz), 8.11-8.14 (1H, m),
9.97 (1H, s); m/z ) 350 [M + H]+.
7-(2-Furyl)-3-(5-indolylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyrimi-
dine-5-amine 78. To a stirred solution of N-Boc-5-methylindole
(2.15 g, 9,.15 mmol) in carbon tetrachloride (100 mL) was added
N-bromosuccinimide (1.63 g, 9.15 mmol) and benzoyl peroxide
(75%, 295 mg, 0.9 mmol). The mixture was refluxed for 1 h, then
cooled and concentrated, and the residues were purified by
chromatography [SiO2, isohexane/EtOAc (30:1)] to give the
protected bromomethylindole as a colorless oil (2.10 g, 74%). NMR
δH (400 MHz, CDCl3) 8.10 (1H, br d, J 7.5 Hz), 7.60 (1H, d, J 3.6
Hz), 7.58 (1H, d, J 1.7 Hz), 7.35 (1H, dd, J 1.7 Hz, 8.6 Hz), 6.54
(1H, d, J 3.6 Hz), 4.63 (2H, s), 1.66 (9H, s)
Alkylation of the furyltriazolopyrimidine 4 (404 mg, 2 mmol)
with this material (682 mg, 2.2 mmol) under the conditions
described above gave a yellow solid (121 mg, 14%) which was
dissolved in methanol (5 mL) and treated with sodium methoxide
(39 mg, 0.73 mmol), and the mixture was refluxed for 5 h. After
concentration to half of the original volume and washing with water,
evaporation to dryness gave the title compound as a cream solid
(63 mg, 74%): mp 226.8-227.4 °C; IR νmax (DR)/cm-1 3475, 3320,
2739, 1645, 1506, 1223, 1008, and 778; NMR δH (400 MHz,
DMSO) 11.14 (1H, br s), 8.14-8.10 (1H, m), 7.90 (1H, d, J 3.5
Hz), 7.50 (1H, s), 7.40-7.31 (4H, m), 7.09 (1H, dd, J 8.0, 1.5
Hz), 6.85 (1H, dd, J 3.5, 1.5 Hz), 6.43-6.38 (1H, m), and 5.70
(2H, s); m/z ) 332 [M + H]+.
7-(2-Furyl)-3-(5-indazolylmethyl)-3H-[1,2,3]triazolo[4,5-d]pyri-
midine-5-amine 79. 79 was prepared via alkylation of the furyl-
triazolopyrimidine 4 (404 mg, 2 mmol) with N-THP-5-bromome-
thylindazole36 (740 mg, 2.5 mmol). After alkylation, the resultant
solid (226 mg, 27%) was dissolved in a mixture of MeOH (5 mL)
and hydrochloric acid (4 M solution in 1,4-dioxane, 1 mL, 0.25
mmol) and the reaction mixture was stirred at room temperature
overnight. After concentration in vacuo, the resulting solid was
triturated with ether, filtered, and dried to give the title compound
(196 mg, quant) as a yellow solid: mp >300 °C dec; IR νmax (DR)/
cm-1 3100, 1662, 1465, 1281, 1032, 782, and 592; NMR δH (400
MHz, DMSO) 8.16-8.13 (1H, m), 8.07 (1H, s), 7.92 (1H, d, J 3.5
Hz), 7.68 (1H, s), 7.54 (1H, d, J 8.5 Hz), 7.35 (1H, dd, 8.5, 1.5
Hz), 6.87 (1H, dd, J 3.5, 2.0 Hz), and 5.76 (1H, s); m/z ) 333 [M
+ H]+.
3-(1H-Benzotriazol-5-ylmethyl)-7-(2-furyl)-3H-[1,2,3]triazolo[4,5-
d]pyrimidine-5-amine 80. A mixture of 5-methyl-1H-benzotriazole
(Acros Chemicals) (666 mg, 5 mmol) in THF (20 mL) was treated
with NaH (60% dispersion, 200 mg, 5 mmol), stirred at room
temperature for 10 min, treated with di-tert-butyl dicarbonate (115
mg, 5 mmol), and stirred overnight. The mixture was treated with
saturated NaHCO3 solution (10 mL), extracted with EtOAc (2 ×
10 mL), dried (MgSO4), filtered through a plug of SiO2, and
concentrated in vacuo to give tert-butyl 5-methylbenzotriazole-1-
carboxylate (as a mixture with the 6-methyl regioisomer) (1.08 g,
92%) as a colorless oil. NMR δH (400 MHz, CDCl3) 7.97 (1H, d,
J 8.4 Hz), 7.87 (1H, s), 7.28 (1H, dd, J 7.6 Hz, 1.2 Hz), 2.56 (2H,
s), 1.76 (9 H, s)
A solution of the protected benzotriazole (as a mixture with the
6-methyl regioisomer) (1.08 g, 4.63 mmol), benzoyl peroxide (112
mg, 0.46 mmol), and N-bromosuccinimide (0.76 g, 4.63 mmol) in
CCl4 (25 mL) was refluxed overnight, cooled, filtered, concentrated
in vacuo, and purified by chromatography [SiO2, isohexane/EtOAc
(10:1)] to give the protected bromomethylbenzotriazole (666 mg,
46%) (as a mixture with the 6-bromomethyl regioisomer) as a
colorless oil. NMR δH (400 MHz, DMSO) 8.21 (1H, d, J 8.6 Hz),
8.14 (1H, s), 7.64 (1H, d, J 8.6 Hz), 4.98 (2H, s), 1.71 (9H, s)
A solution of the furyltriazolopyrimidine 4 (404 mg, 2 mmol)
in DMF (4 mL) was treated with NaH (60% dispersion, 80 mg, 2
mmol), stirred at room temperature for 10 min, treated with a
solution of the protected bromomethylbenzotriazole (as a mixture
with the 6-bromomethyl regioisomer) (624 mg, 2 mmol) in DMF
(2 mL), and stirred overnight. The mixture was concentrated in
vacuo and purified by chromatography [SiO2, isohexane/EtOAc (2:
1)] to give the alkylated triazolopyrimidine (135 mg, 24%) (as a
mixture with the 6-substituted regioisomer) as a white solid which
was dissolved in a mixture of MeOH (5 mL) and THF (5 mL).
The solution was treated with 40% aqueous dimethylamine (0.176
mL, 1.56 mmol), refluxed for 25 min, and concentrated in vacuo
and the resulting solid triturated with ether, filtered, triturated with
MeOH, filtered, and dried to give the title compound as a single
regioisomer (31 mg, 30%) as a yellow solid: mp >300 °C dec; IR
ν
max (DR)/cm-1 3212, 1607, 1438, 1212, 1029, and 770; NMR δH
(400 MHz, DMSO) 15.74 (1H, br s), 8.13 (1H, s), 7.91 (1H, d, J
3.5 Hz), 7.80 (2H, br s), 7.54-7.30 (3H, s), 6.86 (1H, dd, J 4.0,
2.0 Hz), and 5.85 (2H, s); m/z ) 334 [M + H]+.
Acknowledgment. We thank Tim Haymes, Heather Sim-
monite, and Loic LeStrat for analytical support. We also thank
Douglas Williamson and Karen Benwell for helpful comments
during the preparation of this manuscript.
Supporting Information Available: Details of biological pro-
tocols, tables of elemental analysis results, and chromatographic
data, including methods. This material is available free of charge
via the Internet at http://pubs.acs.org.
References
(1) Jankovic, J. Parkinson’s disease: clinical features and diagnosis.
J. Neurol., Neurosurg. Psychiatry 2008, 79 (4), 368–376.
(2) Boller, F.; Mizutani, T.; Roessmann, U.; Gambetti, P. Parkinson
disease, dementia, and Alzheimer disease: clinicopathological cor-
relations. Ann. Neurol. 1980, 7 (4), 329–335.
(3) Blandini, F.; Porter, R. H. P.; Greenamyre, J. T. Glutamate and
Parkinson’s disease. Mol. Neurobiol. 1996, 12 (1), 73–94.
(4) Cotzias, G. C.; Papavasiliou, P. S.; Gellene, R. Modification of
Parkinsonismschronic treatment with L-dopa. New Engl. J. Med. 1969,
280 (7), 337–345.
(5) Barbeau, A. L-Dopa therapy in Parkinson’s disease: a critical review
of nine years’ experience. Can. Med. Assoc. J. 1969, 101 (13), 59–
68.
(6) Rinne, U. K. Problems associated with long-term levodopa treatment
of Parkinson’s disease. Acta Neurol. Scand., Suppl. 1983, 95, 19–26.
(7) Schiffmann, S. N.; Halleux, P.; Menu, R.; Vanderhaeghen, J. J.
Adenosine A2A receptor expression in striatal neurons: implications
for basal ganglia pathophysiology. Drug DeV. Res 1993, 28 (3), 381–
385.
(8) Svenningsson, P.; Le Moine, C.; Fisone, G.; Fredholm, B. B.
Distribution, biochemistry and function of striatal adenosine A2A
receptors. Prog. Neurobiol. 1999, 59 (4), 355–396.
(9) Xu, K.; Bastia, E.; Schwarzschild, M. Therapeutic potential of
adenosine A2A receptor antagonists in Parkinson’s disease. Pharmacol.
Ther 2005, 105 (3), 267–310.
(10) Bara-Jimenez, W.; Sherzai, A.; Dimitrova, T.; Favit, A.; Bibbiani, F.;
Gillespie, M.; Morris, M. J.; Mouradian, M. M.; Chase, T. N.
Adenosine A2A receptor antagonist treatment of Parkinson’s disease.
Neurology 2003, 61 (3), 293–296.
(11) Kanda, T.; Jackson, M. J.; Smith, L. A.; Pearce, R. K. B.; Nakamura,
J.; Kase, H.; Kuwana, Y.; Jenner, P. Adenosine A2A antagonist: a novel
antiparkinsonian agent that does not provoke dyskinesia in Parkinso-
nian monkeys. Ann. Neurol. 1998, 43 (4), 507–513.
(12) Ferre, S.; Von Euler, G.; Johansson, B.; Fredholm, B. B.; Fuxe, K.
Stimulation of high-affinity adenosine A2 receptors decreases the
affinity of dopamine D2 receptors in rat striatal membranes. Proc. Natl.
Acad. Sci. U.S.A. 1991, 88 (16), 7238–7241.
(13) Fuxe, K.; Ferre, S.; Dasgupta, S.; O’Connor, W. T.; Snaprud, P.;
Arenas, E.; Persson, H.; Ungerstedt, U.; Fredholm, B. Evidence for
the Existence of Antagonistic Intramembrane Adenosine A2A/Dopam-
ine D2 Receptor Interactions in the Basal Ganglia: Analysis from the
Network to the Molecular Level. In Adenosine and Adenine Nucle-
otides: From Molecular Biology to IntegratiVe Physiology, Proceedings
of the 5th International Symposium on Adenosine and Adenine
Nucleotides, Philadelphia, PA, May 9-13, 1994; Springer: Berlin,
1995; pp 499-507.
(14) Ferre, S.; Fredholm, B. B.; Morelli, M.; Popoli, P.; Fuxe, K.
Adenosine-dopamine receptor-receptor interactions as an integrative
mechanism in the basal ganglia. Trends Neurosci. 1997, 20 (10), 482–
487.

Triazolo[4,5-d]pyrimidine A2A Antagonists
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 1 47
(15) Pinna, A.; Wardas, J.; Simola, N.; Morelli, M. New therapies for the
treatment of Parkinson’s disease: adenosine A2A receptor antagonists.
Life Sci. 2005, 77 (26), 3259–3267.
(16) Schiffmann, S. N.; Fisone, G.; Moresco, R.; Cunha, R. A.; Ferre, S.
Adenosine A2A receptors and basal ganglia physiology. Prog. Neu-
robiol. 2007, 83 (5), 277–292.
(17) Chen, J.-F.; Xu, K.; Petzer, J. P.; Staal, R.; Xu, Y.-H.; Beilstein, M.;
Sonsalla, P. K.; Castagnoli, K.; Castagnoli, N., Jr.; Schwarzschild,
M. A. Neuroprotection by caffeine and A2A adenosine receptor
inactivation in a model of Parkinson’s disease. J. Neurosci. 2001, 21
(10), RC143/1–RC143/6.
(18) Ongini, E.; Adami, Mm.; Ferri, C.; Bertorelli, R. Adenosine A2A
receptors and neuroprotection. Ann. N.Y. Acad. Sci. 1997, 825
(Neuroprotective Agents), 30–48.
diamino-6-chloropyrimidine and a literature correction. J. Med. Chem.
1966, 9 (4), 573–575.
(32) Meier, R. Preparation of 7-Amino-3-benzyl-3H-1,2,3-triazolo[4,5-
d]pyrimidines as Anticonvulsants. Eur. Pat. Appl. EP288431, 1988.
(33) The desired regiochemistry was initially confirmed by comparison of
the 1H and 13C NMR data for both regioisomers of selected compounds
with the known N-3 regioisomer 13 and the analogous derivatives
14-20. Further confirmation was additionally obtained by synthesis
of selected derivatives by the unambiguous route employed for
compounds 46 and 47, as detailed in Scheme 7.
(34) Borroni, E. M.; Huber-Trottmann, G.; Kilpatrick, G. J.; Norcross, R. D.
Preparation of Pyrimidinamines and Pyridinamines as Adenosine
Receptor Modulators for Treatment of CNS Disorders. PCT Int. Appl.
WO2001062233, 2001.
(19) Rabasseda, X.; Sorbera, L. A.; Martin, L.; Leeson, P. A.; Castaner, J.
KW-6002. Drugs Future 2001, 26 (1), 20–24.
(35) Bentley, S. J.; Milner, D. J. Conjugate addition of Grignard reagents
to para-substituted nitrobenzenes. J. Organomet. Chem. 1993, 447 (1),
1–3.
(36) Sun, J.-H.; Teleha, C. A.; Yan, J.-S.; Rodgers, J. D.; Nugiel, D. A.
Efficient synthesis of 5-(bromomethyl)- and 5-(aminomethyl)-1-THP-
indazole. J. Org. Chem. 1997, 62 (16), 5627–5629.
(37) Binding assays were conducted as described in the following: Weiss,
S. M.; Benwell, K.; Cliffe, I. A.; Gillespie, R. J.; Knight, A. R.;
Lerpiniere, J.; Misra, A.; Pratt, R. M.; Revell, D.; Upton, R.; Dourish,
C. T. Neurology 2003, 61 (11, Suppl. 6), S101.
(38) Bezard, E.; Imbert, C.; Gross, C. E. Experimental models of Parkin-
son’s disease: from the static to the dynamic. ReV. Neurosci. 1998, 9
(2), 71–90.
(39) Mandhane, S. N.; Chopde, C. T.; Ghosh, A. K. Adenosine A2 receptors
modulate haloperidol-induced catalepsy in rats. Eur. J. Pharmacol.
1997, 328 (2/3), 135–141.
(40) Broughton, H. B.; Watson, I. A. Selection of heterocycles for drug
design. J. Mol. Graphics Modell. 2004, 23 (1), 51–58.
(41) Dalvie, D. K.; Kalgutkar, A. S.; Khojasteh-Bakht, S. C.; Obach, R. S.;
O Donnell, J. P. Biotransformation reactions of five-membered
aromatic heterocyclic rings. Chem. Res. Toxicol. 2002, 15 (3), 269–
299.
(42) Richardson, C. M.; Gillespie, R. J.; Williamson, D. S.; Jordan, A. M.;
Fink, A.; Knight, A. R.; Sellwood, D. M.; Misra, A. Identification of
non-furan containing A2A antagonists using database mining and
molecular similarity approaches. Bioorg. Med. Chem. Lett. 2006, 16
(23), 599–5997.
(43) Maximal aqueous solubility was determined in a phosphate buffered
saline solution containing 2.5% DMSO solution.
(20) LeWitt, P. A.; Guttman, M.; Tetrud, J. W.; Tuire, P. J.; Mori, A.;
Chaikin, P.; Sussman, N. M. Adenosine A2A receptor antagonist
istradefylline (KW-6002) reduces “off” time in Parkinson’s disease:
a double-blind, randomized, multicenter clinical trial (6002-US-005).
Ann. Neurol. 2008, 63 (3), 295–302.
(21) http://www.kyowa.co.jp/eng/netext/er060307.htm.
(22) http://www.kyowa.co.jp/eng/netext/er080228_01.htm.
(23) Hockemeyer, J.; Burbiel, J. C.; Mueller, C. E. Multigram-scale
syntheses, stability, and photoreactions of A2A adenosine receptor
antagonists with 8-styrylxanthine structure: potential drugs for Par-
kinson’s disease. J. Org. Chem. 2004, 69 (10), 3308–3318.
(24) Knutsen, L. J. S.; Weiss, S. M. KW-6002, Kyowa Hakko Kogyo. Curr.
Opin. InVest. Drugs 2001, 2 (5), 668–673.
(25) Gillespie, R. J.; Adams, D. R.; Bebbington, D.; Benwell, K.; Cliffe,
I. A.; Dawson, C. E.; Dourish, C. T.; Fletcher, A.; Gaur, S.; Giles,
P. R.; Jordan, A. M.; Knight, A. R.; Knutsen, L. J. S.; Lawrence, A.;
Lerpiniere, J.; Misra, A.; Porter, R. H. P.; Pratt, R. M.; Shepherd, R.;
Upton, R.; Ward, S. E.; Weiss, S. M.; Williamson, D. S. Antagonists
of the human adenosine A2A receptor. Part 1: Discovery and synthesis
of thieno[3,2-d]pyrimidine-4-methanone derivatives. Bioorg. Med.
Chem. Lett. 2008, 18 (9), 2916–2919.
(26) Gillespie, R. J.; Cliffe, I. A.; Dawson, C. E.; Dourish, C. T.; Gaur, S.;
Giles, P. R.; Jordan, A. M.; Knight, A. R.; Lawrence, A.; Lerpiniere,
J.; Misra, A.; Pratt, R. M.; Todd, R. S.; Upton, R.; Weiss, S. M.;
Williamson, D. S. Antagonists of the human adenosine A2A receptor.
Part 2: Design and synthesis of 4-arylthieno[3,2-d]pyrimidine deriva-
tives. Bioorg. Med. Chem. Lett. 2008, 18 (9), 2920–2923.
(27) Gillespie, R. J.; Cliffe, I. A.; Dawson, C. E.; Dourish, C. T.; Giles,
P. R.; Jordan, A. M.; Knight, A. R.; Lawrence, A.; Lerpiniere, J.;
Misra, A.; Pratt, R. M.; Todd, R. S.; Upton, R.; Weiss, S. M.;
Williamson, D. S. Antagonists of the human adenosine A2A receptor.
Part 3: Design and synthesis of pyrazolo[3,4-d]pyrimidines, pyr-
rolo[2,3-d]pyrimidines and 6-arylpurines. Bioorg. Med. Chem. Lett.
2008, 18 (9), 2924–2929.
(44) Porter, R. H. P.; Benwell, K. R.; Lamb, H.; Malcolm, C. S.; Allen,
N. H.; Revell, D. F.; Adams, D. R.; Sheardown, M. J. Functional
characterization of agonists at recombinant human 5-HT2A, 5-HT2B
and 5-HT2C receptors in CHO-K1 cells. Br. J. Pharmacol. 1999, 128,
13–20.
(45) Artursson, P.; Karlsson, J. Correlation between oral drug absorption
in humans and apparent drug permeability coefficients in human
intestinal epithelial (Caco-2) cells. Biochem. Biophys. Res. Commun.
1991, 175 (3), 880–885.
(28) Gillespie, R. J.; Lerpiniere, J.; Gaur, S.; Bamford, S. J.; Stratton, G. C.;
Leonardi, S.; Weiss, S. M. Preparation of Triazolo[4,5-d]pyrimidines
as Purinergic Receptor Antagonists. PCT Int. Appl. WO2002055083,
2002.
(29) Fulmer, S. Y.; Clayton, J. D.; Allen O’Dell, C.; Montgomery, J. A.
Triazolo[4,5-d]pyrimidines. II. O-Substituted derivatives of 8-azagua-
nine and 8-azahypoxanthine. J. Org. Chem. 1962, 27, 4518–4523.
(30) O’Brien, D. E.; Baiocchi, F.; Robins, R. K.; Cheng, C. C. Pyrimidines.
XI. J. Med. Chem. 1963, 6 (5), 467–471.
(46) The measured brain uptake was determined in male Sprague-Dawley
rats from the brain/plasma AUClast ratio, following intravenous
administration of 60 at a dose of 2 mg kg-1
.
(47) http://www.cerep.fr/Cerep/Users/pages/Catalog/Profiles/catalog.asp.
(48) Irwin, S. Comprehensive observational assessment: Ia. A systematic,
quantitative procedure for assessing the behavioral and physiologic
state of the mouse. Psychopharmacologia 1968, 13 (3), 222–257.
(31) O’Brien, D. E.; Cheng, C. C.; Pfleiderer, W. Pyrimidines. XVIII. 2,4-
Diamino-5-nitro-6-arylaminopyrimidines. Nitration study of 2,4-
JM800961G