Synthesis and pharmacological evaluation of novel substituted 9-deazaxanthines as A2B receptor antagonists

Article abstract of DOI:10.1016/j.ejmech.2010.03.011

A new series of 9-deazaxanthine derivatives with various substituents at the heterocyclic system were synthesized and evaluated for their binding affinities for the four human recombinant adenosine receptors, A ₁A₃ subtypes. A number

Full text of DOI:10.1016/j.ejmech.2010.03.011

European Journal of Medicinal Chemistry 45 (2010) 2884e2892
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and pharmacological evaluation of novel substituted 9-deazaxanthines
as A2B receptor antagonists
,
,c,
María Isabel Nieto d, María Carmen Balo a, José Brea b c, Olga Caamaño a
**
,
*
Franco Fernández a
, Xerardo García-Mera c, Carmen López a c, María Isabel Loza b
,
,
c
,
a,
,
,c
José Enrique Rodríguez-Borges e, Bernat Vidal f
a Departamento de Química Orgánica, Facultade de Farmacia, Universidade de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela, Spain
b Departamento de Farmacología, Facultade de Farmacia, Universidade de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela, Spain
c Instituto de Farmacia Industrial, Facultade de Farmacia, Universidade de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela, Spain
d Departamento de Química Fundamental, Facultade de Química, Universidade de A Coruña, Campus da Zapateira, E-15071, A Coruña, Spain
e CIQ-Departamento de Química, Facultade de Ciencias, Universidade de Porto, Rua do Campo Alegre, 687, 4169-007, Porto, Portugal
f Medicinal Chemistry Department, Laboratorios Almirall, S.A., E-08960 St. Just Desvern, Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series of 9-deazaxanthine derivatives with various substituents at the heterocyclic system were
synthesized and evaluated for their binding affinities for the four human recombinant adenosine
receptors, A1eA3 subtypes. A number of the 9-deazaxanthines derivatives 3aem showed moderate-to-
high affinity for hA2B receptors, with compound 3f showing a 32-fold selectivity for A2B over A1 and
Received 18 December 2009
Received in revised form
5 March 2010
Accepted 9 March 2010
Available online 12 March 2010
a 2750-fold selectivity for A2B over A2A
.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Dedicated to Professor Antonio García-
Martínez on the occasion of his 70th
birthday.
Keywords:
Substituted-9-deazaxanthines
Synthesis
Adenosine receptor antagonist
A1, A2A, A2B, and A3 binding affinities
1. Introduction
Along with purine nucleosides analogues and condensed
tricyclic nitrogen heterocyclic derivatives [2e10], xanthines
derivatives constitute one of the most widely exploited classes of
AR (adenosine receptor) ligands [11e15]. Selective A2B receptor
antagonists can therefore play a role in important pathologies
such as neurological (e.g., AD and dementia) and hypersensitive
(e.g., asthma) disorders, and diabetes [16]. Our main interest in
this challenging area has been the development of selective A2B
antagonists as potential anti-asthmatic agents [17e20]. After the
pioneering work of Müller et al. [21] showed evidence of the
existence of compounds carrying a 9-deazaxanthine (9-dAX)
scaffold endowed of AdoR antagonistic activity, suitably
substituted 9-dAXs that are highly potent hA2B antagonist have
been unveiled [19e25].
Adenosine is an endogenous purine nucleoside that is normally
increased under conditions of hypoxia or high metabolism that
typically occur in pathological or stressful situations. Four diverse
G-protein-coupled adenosine receptor (AdoR) subtypes (A1, A2A
A2B, A3) have been identified and characterized at biological,
,
pharmacological and physiological levels [1].
* Corresponding author at: Departamento de Química Orgánica, Facultade de
Farmacia, Universidade de Santiago de Compostela, Campus Sur, E-15782 Santiago
de Compostela, Spain. Tel.: þ34 981563100 15047; fax: þ34 981594912.
** Corresponding author at: Departamento de Química Orgánica, Facultade de
Farmacia, Universidade de Santiago de Compostela, Campus Sur, E-15782 Santiago
de Compostela, Spain. Tel.: þ34 981563100 14942; fax: þ34 981594912.
E-mail addresses: molga.caamano@usc.es (O. Caamaño), franco.fernandez@usc.
es (F. Fernández).
In particular, some 1,3-dialkyl-8-[4-(N-arylcarbamoylme-
thoxy)phenyl]-9-dAXs [22e24], e.g., 1, and 1,3-dialkyl-8-[4-(N-
arylcarbamoyloxymethyl)phenyl]-9-dAXs [20], e.g., 2, represent
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.03.011

M.I. Nieto et al. / European Journal of Medicinal Chemistry 45 (2010) 2884e2892
2885
a novel class of AR ligands endowed with nanomolar affinities at
2. Chemistry
the hA2B, hA1 and hA2A AR subtypes. However, none of these
ligands exhibited an acceptably high selectivity versus the
hA2BAR.
The synthesis of the target compounds 3aem was performed
according to published procedures [20,22,26,27], as outlined in
O
H
O
H
N
N
N
N
O
O
O
O
O
N
O
N
S
HN
HN
1
2
As a continuation of our ongoing research in the field we
designed, synthesized and evaluated at AdoRs a new series of
9-dAXs (3), some of which differ from previously reported ligands
in the combination of R1, R2 and/or R4 radicals.
Scheme 1. The key intermediates for the synthesis of compounds
3aei were 9-dAX carboxylic acid derivatives 7a, 7c and 7e, and
these were prepared by the condensation of appropriate uracil
derivatives 4 with the corresponding para-substituted benzalde-
O
R4
R5
R1
O
N
N
O
O
N
N
R
=
R
,
N
Br
O
NR3R3'
R2
3
O
O
CHO
O
R4
R1
R1
O
NO2
R4
NO2
N
N
i)
O
+
CO2R3
O
N
N
R2
R2
CO2R3
4a
5a: R3= R4 = H
5b: R3= Et, R4 = H
5c
6a
: R1= H, R2 = Pr, R3 = R4 = H
6b: R1= Pr, R2 = H, R3 = Et, R4 = H
6c: R1= R2 = Me, R3 = Et, R4 = OCH3
: R1= H, R2 = Pr
4b: R1=Pr, R2 = H
4c: R1= R2 = Me
: R3= Et, R4 = OCH3
ii)
O
R4
H
7a: R1= H, R2 = Pr, R3 = R4 = H
7b: R1=Pr, R2 = H, R3 = Et, R4 = H
7c: R1=Pr, R2 = R3 = R4 = H
R1
O
N
N
iii)
iii)
O
7d
: R1 = R2 = Me, R3 = Et, R4 = OMe
CO2R3
N
7e: R1 = R2 = Me, R3 = H, R4 = OMe
R2
iv)
O
R4
H
R1
O
N
N
O
R
N
R2
3a-3i
Scheme 1. Reagents, conditions and yields: i) Dioxane, piperidine, DMAP, reflux, 5e96 h, 6a (64%), 6b (55%), 6c (88%). ii) HCO2H, Na2S2O4, reflux, 18 h, 7a (89%), 7b (75%), 7d (72%).
iii) NaOH, EtOH, reflux, 1 h, 7c (82%), 7e (77%). iv) Appropriate amine, EDC, HOBt, TEA, DMF, rt, 5e8 days.

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M.I. Nieto et al. / European Journal of Medicinal Chemistry 45 (2010) 2884e2892
hydes 5 to afford the 6-styryluracils 6, followed by cyclization to the
9-dAXs 7 and, where necessary, saponification to the free carbox-
ylic acid. The amidation procedure for the synthesis of the 9-dAX
3aei involved condensation of 9-dAX carboxylic acids 7 and the
appropriate amines in a polar aprotic solvent (DMF) in the presence
of an organic base (triethylamine), 1-[3-dimethylaminopropyl]-3-
ethylcarbodiimide hydrochloride (EDC) and 1-hydroxybenzo-
triazole (HOBt).
The synthesis of 3j (Scheme 2) was carried out by methylation
of 2-[4-(1-methyl-2,4-dioxo-3-propyl-2,3,4,5-tetrahydro-1H-pyr-
rolo[3,2-d]pyrimidin-6-yl)phenyloxy]acetic acid (8) [22] with
CH3I and Na2CO3 in dry DMF at 65 ꢀC for 24 h. The 1H NMR
spectrum of the isolated product shows three singlets (at 3.89,
3.68 and 3.36 ppm, each integrating for three protons) that are
assigned to the methyl groups in positions 7 and 3 (3.68 and
3.36 ppm), respectively, and to a CH3O group of an ester
(3.89 ppm), which is consistent with that, in addition to methyl-
ation at position 7, esterification of the carboxylic acid group of 8
has taken place to give 9a. This crude product was then saponified
under the conditions indicated in Scheme 2, which gave the
desired acid 9b. Reaction of this compound with 4-fluoroaniline
under the previously described amidation conditions gave
compound 3j.
having a substituent at position 1 for the improvement of this
property, best results being obtained when R1 is a propyl group.
Thus, compound 3g showed maximum affinity for A1 receptor, with
a 2-fold A1/A2B selectivity.
Interestingly, affinities for the A2B receptor subtype were found
to be generally higher than those observed for the A2A receptor. The
best affinity for the A2B receptor is obtained when R1 is a propyl
radical, and R3 is 4-halophenylaminocarbonyl group [see
compounds 3feh, which bear a propyl radical in position 1 and
showed moderate-to-high affinity at human A2B receptor (Ki in the
2.34e31.6 nM range)], with the most interesting compound 3f
showing both high affinity for human A2B receptor and a 32-fold
A2B/A1 selectivity and a 2750-fold A2B/A2A selectivity. Though not
determined, selectivity over A3 receptor is estimated to be even
higher.
In contrast, affinity for the A2B receptor decreased for the
compounds 3a, 3b and 3d, which contain a propyl group in position
3, (Ki in the 21.9e115 nM range), while their selectivity over A1 and
A2 receptors increased. All these compounds had a very low affinity
for human A3 receptors, in line with previously reported findings
on related structures [11,28,29].
The 7-methyl-9-dAX derivatives (compounds 3jem) were
found to have a notably decreased affinity for human A2B receptor
with regard to their corresponding 7-demethyl counterparts (all of
them with Ki in the 2.40e5.62 nM range [17,20]), as maximum
affinity at this subset was found for compound 3l, with
a Ki ¼ 97.7 nM.
Finally, 7-methyl-9-dAX derivatives 3kem were prepared from
the corresponding 9-dAX 10aec, [22] by treatment with CH3I in
DMF in the presence of K2CO3 (Scheme 3).
The physicochemical characteristics of the synthesized
compounds are presented in Table 1.
Analysis of the structureeactivity relationships (SAR) shows
that N-1 substituted 9-deazaxanthines derivatives present higher
affinity and selectivity at A2B receptor compared to their N-3
counterparts (3aee) and to their corresponding 1,3-disubstituted
analogues (3iem). This appears to be a general trend previously put
in evidence on xanthine derivatives [11,28,29].
3. Results and discussion
Chemical structures and human AR binding affinities of the
novel 1,3,8-substituted-9-deazaxanthine derivatives 3aem are
reported in Table 2. The affinity (pKi or displacement percentage)
values were determined at cloned human adenosine receptors
expressed in HeLa cells (hA2A and hA3), HEK-293 cells (hA2B) and
CHO-A1 cells (hA1). The radioligand [3H]DPCPX was used for
competition binding assays on A1 and A2B receptors whereas [3H]
ZM241385 was used for A2A and [3H]NECA for A3 receptors
[17,18,20]. The affinity values of compounds that did not fully
4. Conclusion
The results reported here show that 1-alkyl-8-(4-halo-
phenylaminocarbonylmethoxyphenyl)-9-deazaxanthines can be
considered as appropriate compounds to develop potent and hope-
fully ligands for the ARs, especially at the A2B receptor subtype.
Interestingly, affinities at the A2B receptor subtype were found to be
generally higher than thoseobservedat theA2A receptor, especially 3-
unsubstituted 9-deazaxanthine derivatives bearing a propyl group at
the 1-position and a 4-halophenylaminocarbonylmethoxyphenyl
residueatthe8-position,withthemostselectivecompound 3fhaving
a Ki(A1)/Ki(A2B) ratio over 32 and a Ki(A2A)/Ki(A2B) ratio over 2750.
displace specific radioligand binding at 1
mM are given only in
terms of displacement percentage. The biological methods
employed are fully described into the Experimental part.
All of the compounds displayed in this Table showed low affinity
for human A3 receptor. On the other hand, affinity values of our
compounds for the A1 receptor subtype point to the convenience of
O
H
O
N
N
N
N
i)
O
O
CO2H
CO2R
O
N
O
N
9a: R = Me
ii)
9b
8
: R = H
iii)
O
N
N
N
O
O
O
HN
F
3j
Scheme 2. Reagents and conditions: i) CH3I, K2CO3, DMF, 65 ꢀC, 24 h. ii) EtOH, 3 N NaOH, 80 ꢀC, 1 h. iii) 4-fluorophenylaniline, EDC, TEA, HOBt, DMF, rt, 48 h.

M.I. Nieto et al. / European Journal of Medicinal Chemistry 45 (2010) 2884e2892
2887
O
N
O
H
N
N
N
N
O
O
R
O
O
R
O
O
N
3k
3l
3m
10a
(50%)
(63%)
: R = 4-phenylpiperazinyl
10b
: R = 3,4-dihydroisoquinolin-2(1H)-yl
10c
(61%)
: R = 4-fluorophenylamino
Scheme 3. Reagents and conditions: a) CH3I, K2CO3, DMF, 65 ꢀC, 5e7 h.
5. Experimental
5.1.1. General procedure for the condensation between 6-methyl-
5-nitrouracils 4 and benzaldehydes 5. Preparation of 1,3-dialkyl-
6-styryluracil derivatives 6aec
5.1. Chemistry
A solution of the corresponding 1,3-dialkyl-6-methyl-5-nitro-
pyrimidine-2,4(1H,3H)-dione 4aec (8 mmol), the appropriate
benzaldehyde 5 (8 mmol), piperidine (12 mmol) and 3 Å molecular
sieves in dry dioxane (50 mL) was heated under reflux for the
appropriate time under argon and then allowed to cool down to
room temperature.
General information. All chemicals used were of reagent grade
and were obtained from Aldrich Chemical Co. and used without
further purification. Where necessary, solvents were dried by
standard techniques and distilled. All air-sensitive reactions were
carried out under argon. Flash chromatography was performed on
silica gel (Merck 60, 230e240 mesh) and analytical TLC was carried
out on pre-coated silica gel plates (Merck 60 F254, 0.25 mm).
Melting points (uncorrected) were measured in a glass capillary
tube on a Stuart Scientific electro thermal SMP3 apparatus. Infrared
spectra were recorded on a Perkin-Elmer 1640 FTIR spectropho-
tometer. 1H NMR spectra were recorded on a Bruker AMX 300
spectrometer at 300 MHz using TMS as internal standard (chemical
5.1.1.1. 2-{4-[(E)-2-(5-Nitro-2,4-dioxo-3-propyl-1,2,3,6-tetrahy-
dropyrimidin-4-yl)ethenyl]phenyloxy}acetic acid [6a]. Reaction time
48 h. 6 N HCl was added to the solution and the resulting precipi-
tate was collected by filtration and washed with water. Yield 64%.
1H NMR (DMSO-d6): 12.25 (br s, 1H, D2O exchange, CO2H), 7.58
(d, J ¼ 8.2 Hz, 2H, C6H4O), 7.05e6.88 (m, 4H, 2H C6H4O þ 2H,
HC]CH), 4.73 (s, 2H, CH2O), 3.89e3.73 (m, 2H, CH2N), 3.40 (br s,
1H, D2O exchange, NH), 1.62e1.53 (m, 2H, CH2CH3), 0.81
(t, J ¼ 7.3 Hz, CH3).
shifts in
d values, J in Hertz). Mass spectra were recorded on
a Hewlett-Packard HP5988A, a Micromass Autospec spectrometers
or an Electrospray interface Ion Trap Mass spectrometer. (1100
series LC/MSD Trap System Agilent, Palo Alto, Ca). Microanalyses
were performed on a FISONS EA 1108 Elemental Analyser at the
University of Santiago Microanalysis Service; all results shown are
within 0.4% of the theoretical values.
The uracil derivatives 4 needed for the preparation of target
compounds 3 were either commercially available or recently
obtained by standard methods [19,30,31].
5.1.1.2. Ethyl 2-{4-[(E)-2-(5-nitro-2,4-dioxo-1-propyl-1,2,3,6-tet-
rahydropyrimidin-4-yl)ethenyl]phenyloxy}acetate [6b]. Reaction
time 96 h. 6 N HCl was added to the solution and the resulting
precipitate was collected by filtration and washed with ether. Yield
55%. 1H NMR (DMSO-d6): 11.62 (s, 1H, D2O exchange, NH), 7.74
(d, J ¼ 16.1 Hz, 1H, CH]CH), 7.58 (d, J ¼ 8.6 Hz, 2H, 2-H and 6-H,
Table 1
Physicochemical characteristics of synthesized 1,3,8-substituted-9-deazaxanthines 3aem.
O
R4
R5
R1
O
N
N
O
R
N
R2
Compd.
R1
R2
R
R4
R5
Molecular formula
Mol. wt
Mp (ꢀC)
Yield (%)
3a
3b
3c
3d
3e
3f
3g
3h
3i
H
H
H
H
Pr
Pr
Pr
Pr
Pr
H
4-bromophenylaminocarbonyl
4-fluorophenylaminocarbonyl
phenylaminocarbonyl
4-phenylpiperazinylcarbonyl
3,4-dihydroisoquinolin-2(1H)-ylcarbonyl
4-fluorophenylaminocarbonyl
H
H
H
H
H
H
H
H
OMe
H
H
H
H
H
H
H
H
H
H
H
H
C
23H21BrN4O4
497.34
436.44
418.16
487.22
458.20
436.44
497.34
522.35
538.35
464.49
543.66
514.26
492.54
276e278
306e308
277e280
280e282
246e248
>370
>305
>300
>350
195e196
172e174
121e123
169e171
25
56
37
20
28
75
20
32
27
39
33
63
61
C23H21FN4O4
C23H22N4O4
C27H29N5O4
C26H26N4O4
C23H21FN4O4
H
Pr
Pr
Pr
Me
Pr
Pr
Pr
Pr
H
H
4-bromophenylaminocarbonyl
C23H21BrN4O4
3-(4-bromophenyl)-1,2,4-oxadiazol-5-yl)
3-(4-bromophenyl)-1,2,4-oxadiazol-5-yl)
4-fluorophenylaminocarbonyl
4-phenylpiperazinylcarbonyl
3,4-dihydroisoquinolin-2(1H)-ylcarbonyl
4-fluorophenylaminocarbonyl
C24H20BrN5O4
C24H20BrN5O5
C25H25FN4O4
C31H37N5O4
C30H34N4O4
C27H29FN4O4
Me
Me
Pr
Pr
Pr
H
3j
3k
3l
Me
Me
Me
Me
3m

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M.I. Nieto et al. / European Journal of Medicinal Chemistry 45 (2010) 2884e2892
Table 2
Chemical structures and binding affinitiesa at human A2B, A2A, A1 and A3 AdoRs of 1,3,8-substituted-9-deazaxanthines.
O
R4
R5
R1
O
N
N
O
R
N
R2
Compd.
R1
R2
R
R4
R5
hA2B
7.66
7.0
5.98
6.94
7.10
8.63
8.45
7.50
7.39
7.51
hA2A
hA1
hA3
A2B/A2A ratiob
A2B/A1 ratiob
3a
3b
3c
3d
3e
3f
3g
3h
3i
H
H
H
H
Pr
Pr
Pr
Pr
Pr
H
4-bromophenylaminocarbonyl
4-fluorophenylaminocarbonyl
phenylaminocarbonyl
4-phenylpiperazinylcarbonyl
3,4-dihydroisoquinolin-2(1H)-ylcarbonyl
4-fluorophenylaminocarbonyl
H
H
H
H
H
H
H
H
OMe
H
H
H
H
H
H
H
H
H
H
H
H
22%
36%
17%
33%
12%
5.19
43%
11%
41%
2%
0.5%
23%
9%
7.12
8.76
21%
36%
6.74
22%
19%
9%
28%
3%
1%
15%
1%
2%
14%
2%
3%
6%
2%
e
e
e
e
e
e
e
e
H
e
e
Pr
Pr
Pr
Me
Pr
Pr
Pr
Pr
2754.23
e
32.36
0.49
e
H
H
4-bromophenylaminocarbonyl
3-(4-bromophenyl)-1,2,4-oxadiazol-5-yl)
3-(4-bromophenyl)-1,2,4-oxadiazol-5-yl)
4-fluorophenylaminocarbonyl
4-phenylpiperazinecarbonyl
3,4-dihydroisoquinolin-2(1H)-ylcarbonyl
4-fluorophenylaminocarbonyl
e
Me
Me
Pr
Pr
Pr
H
6.15
17.38
e
e
3j
3k
3l
Me
Me
Me
Me
11%
22%
29%
15%
5.89
e
36%
7.01
20%
e
9%
1%
e
e
3m
e
e
a
Binding affinity is expressed as pKi or displacement percentage at 1
Affinity ratios were calculated on the basis of Ki values.
mM where indicated. pKi and displacement percentage values had an SEM < 10%.
b
C6H4O), 6.99 (d, J ¼ 8.5 Hz, 2H, 3-H and 5-H, C6H4O), 6.82
(d, J ¼ 16.1 Hz, 1H, CH]CH), 4.84 (s, 2H, CH2O), 4.15 (q, J ¼ 7.0 Hz,
2H, 2-H and 6-H, C6H4O), 6.65 (d, J ¼ 9.0 Hz, 2H, 3-H and 5-H,
C6H4O), 6.17 (d, J ¼ 2.3 Hz, 1H, 7-H), 4.52 (s, 2H, CH2O), 3.79e3.74
(m, 2H, CH2N), 1.59e1.50 (m, 2H, CH2CH3), 0.88e0.82 (m, 3H,
CH3).
2H, OCH2CH3), (3.74 (t,
J
¼
7.4 Hz, 2H, CH2N), 1.56e1.51
(m, 2H, CH2CH3), 1.20 (t, J ¼ 7.1 Hz, 2H, OCH2CH3), 0.86 (t, J ¼ 7.6 Hz,
3H, CH3).
5.1.2.3. Ethyl 2-[4-(1,3-dimethyl-2,4-dioxo-2,3,4,5-tetrahydro-1H-pyr-
rolo[3,2-d]pyrimidin-6-yl)-3-methoxyphenyloxy]acetate [7d]. Yield
72%. 1H NMR (DMSO-d6): 8.67 (br s, 1H, D2O exchange, NH), 7.72
(d, J ¼ 8.5 Hz, 1H, 6-H C6H3), 6.71 (s, 1H, 7-H), 6.60 (d, 1H, J ¼ 8.5 Hz,
5-H C6H3), 6.53 (s, 1H, H-6 C6H3), 4.87 (s, 2H, CH2O), 4.20 (q, 2H,
J ¼ 7.0 Hz, CH2CH3), 3.88 (s, 3H, CH3O), 3.41 (s, 3H, CH3N), 3.26
(s, 3H, CH3N), 1.24 (t, 3H, J ¼ 7.0 Hz, CH2CH3).
5.1.1.3. Ethyl 2-{4-[(E)-2-(1,3-dimethyl-5-nitro-2,4-dioxo-1,2,3,6-tet-
rahydropyrimidin-4-yl)ethenyl]-3-methoxyphenyloxy}acetate [6c].
Reaction time 48 h. The resulting solution was concentrated under
vacuum and the black residue was washed with EtOH/ether to give
a yellow solid. Yield 88%. 1H NMR (DMSO-d6): 7.61 (d, J ¼ 8.5 Hz,1H,
6-H C6H3), 7.13 (d, 1H, J ¼ 16.5 Hz, HC]CH), 6.99 (d, 1H, J ¼ 16.5 Hz,
HC]CH), 6.64 (s, 1H, 3-H C6H3), 6.60 (d, 1H, J ¼ 8.5 Hz, 5-H C6H3,),
4.86 (s, 2H, OCH2), 4.17 (q, 2H, J ¼ 7.07 Hz, CH2N), 3.82 (s, 3H, CH3O),
3.35 (s, 3H, CH3N), 3.22 (s, 3H, CH3N), 1.21 (t, 3H, J ¼ 7.07 Hz,
CH2CH3).
5.1.3. General procedure for the hydrolysis of 7b and 7d
To a suspension of the corresponding ethyl ester 7b or 7d
(1.60 mmol) in EtOH (12 mL) was added 2.5 N NaOH (12 mL) and
the mixture was heated under reflux for 1 h. The resulting yellow
solution was cooled to room temperature and was evaporated
under reduced pressure to remove the EtOH. 3 N HCl was added to
the resulting suspension and the precipitate was collected by
filtration, washed with water and dried.
5.1.2. General procedure for the reductive ring closure of 5-nitro-
6-styryluracils 6aeb to 7a, 7b or 7d
To a solution of the appropriate 5-nitro-6-styryluracil derivative
6aec (5 mmol) in formic acid (44 mL) was slowly added sodium
dithionite (25 mmol) and the mixture was heated under reflux for
18 h overnight. The resulting suspension was cooled to room
temperature and poured into water. The precipitate was collected
by filtration, washed with water and dried under vacuum to yield
the expected compounds 7aeb or 7d.
5.1.3.1. 2-[4-(2,4-Dioxo-3-propyl-2,3,4,5-tetrahydro-1H-pyrrolo[3,2-d]
pyrimidin-6-yl)phenyloxy]acetic acid [7c]. Yield 82%. 1H NMR
(DMSO-d6): 10.77 (s, 1H, D2O exchange, CO2H), 8.12 (s, 1H, D2O
exchange, NH), 7.91 (s, 1H, D2O exchange, NH), 7.10 (d, J ¼ 8.6 Hz,
2H, 2-H and 6-H, C6H4O), 6.65 (d, J ¼ 9.0 Hz, 2H, 3-H and 5-H,
C6H4O), 6.17 (d, J ¼ 2.3 Hz, 1H, 7-H), 4.52 (s, 2H, CH2O), 3.79e3.74
(m, 2H, CH2N), 1.59e1.50 (m, 2H, CH2CH3), 0.88e0.82 (m, 3H,
CH3).
5.1.2.1. 2-[4-(2,4-Dioxo-1-propyl-2,3,4,5-tetrahydro-1H-pyrrolo[3,2-d]
pyrimidin-6-yl)phenyloxy]aceticacid [7a]. Yield 89%. 1H NMR (DMSO-
d6): 13.15 (br s, 1H, CO2H), 12.23 (br s, 1H, D2O exchange, NH), 10.82
(br s, 1H, D2O exchange, NH), 7.82 (d, 2H, J ¼ 5Hz, C6H4O), 6.99e6.93
(m, 2H, C6H4O), 6.60 (s, 1H, 7-H), 4.71 (s, 2H, CH2O), 3.81e3.77 (m,
2H, CH2N), 1.68e1.63 (m, 2H, NCH2CH2), 0.94 (t, 3H, J ¼ 7.5 Hz, CH3).
5.1.3.2. 2-[4-(1,3-Dimethyl-2,4-dioxo-2,3,4,5-tetrahydro-1H-pyrrolo
[3,2-d]pyrimidin-6-yl)-3-methoxyphenyloxy]acetic acid [7e]. Yield
77%. 1H NMR (DMSO-d6): 11.93 (br s, 1H, CO2H), 8.14 (br s, 1H,
NH), 7.68 (d, J ¼ 8.2 Hz, 1H, 6-H C6H3O), 6.68 (s, 1H, 3-H, C6H3O),
6.55 (d, 1H, J ¼ 8.2 Hz, 5-H C6H3O), 6.50 (s, 1H, 7-H), 4.87
(s, 2H, CH2O), 3.86 (s, 3H, CH3O), 3.77 (s, 3H, CH3N), 3.71 (s, 3H,
CH3N).
5.1.2.2. Ethyl 2-[4-(2,4-dioxo-3-propyl-2,3,4,5-tetrahydro-1H-pyrrolo
[3,2-d]pyrimidin-6-yl)phenyloxy]acetate [7b]. Yield 75%. 1H NMR
(DMSO-d6): 10.77 (s, 1H, D2O exchange, CO2H), 8.12 (s, 1H, D2O
exchange, NH), 7.91 (s, 1H, D2O exchange, NH), 7.10 (d, J ¼ 8.6 Hz,

M.I. Nieto et al. / European Journal of Medicinal Chemistry 45 (2010) 2884e2892
2889
5.1.4. General procedures for the preparation of amides 3aej
from the appropriate carboxylic acid xanthine derivatives 7a, 7b,
7d or 9b
(CH), 124.46 (C), 124.11 (CH), 120.08 (CH), 115.38 (CH), 111.26 (C),
92.98 (CH), 67.53 (CH2), 43.65 (CH2), 21.01 (CH2), 11.37 (CH3). MS (EI)
m/z (%): 419 (M þ 1, 1), 418 (12), 396 (7), 147 (27), 121 (25), 107 (64),
95 (63), 91 (52), 81 (69), 69 (80), 57 (82), 55 (100). Anal. Calcd for
C23H22N4O4 (418.16): C, 66.02; H, 5.30; N, 13.39. Found: C, 66.53; H,
5.67; N, 13.13.
To
a mixture of the carboxylic acid 7 (see Scheme 1)
(1.24 mmol), N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide
hydrochloride (0.28 g, 1.49 mmol), 1-hydroxybenzotriazole (0.20 g,
1.49 mmol), triethylamine (0.35 mL, 2.48 mmol) and anhydrous
CH2Cl2 (20 mL) was added the appropriate amine (1.61 mmol) and
the mixture was stirred at room temperature for 5e8 days under an
argon atmosphere. The resulting solution was evaporated under
reduced pressure and the residue was dissolved in DCM and
washed with a saturated aqueous sodium bicarbonate. The organic
phase was separated, washed with water and brine, dried (Na2SO4)
and evaporated under reduced pressure. The resulting crude
material was purified by flash column chromatography on silica gel
or crystallized from H2O/MeOH.
5.1.4.4. 6-[4-(4-Phenylpiperazin-1-yl)carbonylmethoxyphenyl]-1-prop-
yl-1,5-dihydro-3H-pirrolo[3,2-d]pyrimidine-2,4-dione [3d]. Yield 20%,
mp 280e282 ꢀC. IR (KBr) (cmꢁ1): 3431, 3183, 3034, 1684, 1553, 1490,
n
1466, 1230, 1183, 1025, 694. 1H NMR (DMSO-d6): 12.18 (s, 1H, D2O
exchange, NH), 10.08 (s, 1H, D2O exchange, NH), 7.82 (d, J ¼ 8.6 Hz, 2H,
2-H and 6-H, C6H4O), 7.21 (t, J ¼ 7.7 Hz, 2H, 3-H and 5-H, C6H5),
7.00e6.94 (m, 2H, 3-H and 5-H, C6H4O), 6.82e6.78 (m, 3H, 3-H, 4-H
and 5-H, C6H5), 6.61 (s, 1H, 7-H), 4.92 (s, 2H, CH2O), 3.78 (t, J ¼ 7.0 Hz,
2H, CH2N), 3.65e3.58 (m, 4H, C4H8N2), 3.19e3.11 (m, 4H, C4H8N2),
1.65 (sext, J ¼ 7.1 Hz, 2H, CH2CH3), 0.90 (t, J ¼ 7.3 Hz, 3H, CH3). 13
C
5.1.4.1. 2-[4-(2,4-Dioxo-1-propyl-2,3,4,5-tetrahydro-1H-pyrrolo[3,2-d]
NMR and DEPT (DMSO-d6): 166.05 (C), 158.43 (C), 155.16 (C), 151.17
(C), 151.06 (C), 139.77 (C), 137.62 (C), 129.30 (CH), 127.09 (CH), 124.06
(C), 119.67 (CH), 116.18 (CH), 115.25 (CH), 111.12 (C), 92.61 (CH), 66.16
(CH2O), 48.57 (2CH2), 45.56 (CH2), 43.87 (CH2), 40.63 (CH2), 20.99
(CH2), 11.28 (CH3). MS (EI) m/z (%): 488 (M þ 1, 8), 487 (33), 281 (16),
207 (20), 161 (55), 160 (21), 132 (100), 105 (20), 104 (14), 73 (10), 56
(22). Anal. Calcd for C27H29N5O4 (487.22): C, 66.55; H, 6.00; N, 14.36.
Found: C, 66.83; H, 5.84; N, 14.11.
pyrimidin-6-yl)phenyloxy]-N-(4-bromophenyl)acetamide [3a]. Yield
25%, mp 276e278 ꢀC. IR (KBr) (cmꢁ1): 3178, 3034, 2964, 1682,1550,
n
1489, 1437, 1182, 1119, 1009, 831, 777. 1H NMR (DMSO-d6): 12.00 (s,
1H, D2O exchange, NH), 10.53 (s, 1H, D2O exchange, NHCO), 10.16 (s,
1H, D2O exchange, NH), 7.67 (d, J ¼ 8.6 Hz, 2H, 2-H and 6-H, C6H4Br),
7.46 (d, J ¼ 8.6 Hz, 2H, 3-H and 5-H, C6H4Br), 7.34 (d, J ¼ 8.6 Hz, 2H, 2-
H and 6-H, C6H4O), 6.88 (d, J ¼ 8.5 Hz, 2H, 3-H and 5-H, C6H4O), 6.41
(s, 1H, 7-H), 4.58 (s, 2H, CH2O), 3.94e3.47 (m, 2H, CH2N), 1.50e1.05
(m, 2H, CH2eCH3), 0.73 (t, J ¼ 7.0 Hz, 3H, CH3). 13C NMR and DEPT
(DMSO-d6): 167.30 (C), 158.49 (C), 155.56 (C), 151.55 (C), 140.04 (C),
138.46 (C), 137.97 (C), 132.24 (CH), 127.60 (CH), 124.84 (C), 122.31
(CH), 116.05 (C), 115.70 (C), 111.60 (C), 93.07 (CH), 79.86 (CH), 67.80
(CH2), 45.94 (CH2), 21.37 (CH2), 11.69 (CH3). MS (EI) m/z (%): 498 (5),
496 (M, 4), 285 (100), 284 (44), 243 (64), 213 (78), 207 (17). Anal.
Calcd for C23H21BrN4O4 (497.34): C, 55.54; H, 4.26; Br, 16.07; N, 11.27.
Found: C, 55.59; H, 4.35; Br, 15.88; N, 10.97.
5.1.4.5. 6-[4-(1,2,3,4-Tetrahydroisoquinolin-2-yl)carbonylmethoxyphe-
nyl]-1-propyl-1,5-dihydro-3H-pyrrolo[3,2-d]pyrimidine-2,4-dione[3e].
Yield 28%, mp 246e248 ꢀC. IR (KBr) (cmꢁ1): 3173, 3040, 2967, 1673,
n
1551, 1485, 1369, 1284, 1225, 1180, 1084, 819, 768. 1H NMR (DMSO-
d6): 12.32 (s, 1H, D2O exchange, NH), 10.11 (s, 1H, D2O exchange, NH),
7.81 (d, J ¼ 8.4 Hz, 2H, 2-H and 6-H, C6H4O), 7.18 (virtual s, 4H, C6H4),
7.00 (d, J ¼ 8.1 Hz, 2H, 3-H and 5-H, C6H4O), 6.60 (s, 1H, 7-H), 4.96 (s,
2H, CH2O), 4.72e4.68 (m, 1H, 2-HH C9H10N), 4.66e4.61 (m, 1H, 2-HH
C9H10N), 3.78e3.76 2H, 6-H2 C4H6N2), 3.70e3.68 (m, 2H, CH2N),
2.94e2.91 (m, 2H, 5-H2 C4H6N2), 1.65 (sext, J ¼ 7.0 Hz, 2H, CH2CH3),
0.90 (t, J ¼ 7.3 Hz, 3H, CH3). 13C NMR and DEPT (DMSO-d6): 166.58
(C), 158.54 (C), 155.21 (C), 151.23 (C), 139.85 (C), 137.69 (C), 133.03 (C),
128.75 (C), 127.15 (CH), 126.83 (CH), 126.57 (CH), 124.07 (C), 115.28
(CH), 111.16 (C), 92.66 (CH), 66.36 (CH2), 45.60 (CH2), 44.01 (CH2),
42.13 (CH2), 28.96 (CH2), 21.04 (CH2), 11.33 (CH3). MS (EI) m/z (%):
459 (M þ 1, 27), 458 (88), 284 (22), 174 (86), 146 (39), 132 (100), 130
(26), 117 (32), 115 (20), 105 (16), 104 (16), 58 (34). Anal. Calcd for
C26H26N4O4 (458.20): C, 68.11; H, 5.72; N, 12.22. Found: C, 68.39; H,
5.94; N, 12.48.
5.1.4.2. 2-[4-(2,4-Dioxo-1-propyl-2,3,4,5-tetrahydro-1H-pyrrolo[3,2-d]
pyrimidin-6-yl)-phenyloxy]-N-(4-fluorophenyl)]acetamide [3b]. Yield
56%, mp 306e308 ꢀC. IR (KBr) (cmꢁ1): 3156, 3033, 2968,1685,1550,
n
1437,1369,1220,1069, 835, 777. 1H NMR (DMSO-d6): 12.20 (s,1H, D2O
exchange, NH), 10.78 (s, 1H, D2O exchange, NHCO), 10.16 (s, 1H, D2O
exchange, NH), 7.85 (d, J ¼ 8.7 Hz, 2H, 2-H and 6-H, C6H4F), 7.65 (d,
J ¼ 9.0 Hz, 2H, 2-H and 6-H, C6H4O) 7.16 (t, J ¼ 8.9 Hz, 2H, 3-H and 5-
H, C6H4F), 7.05 (d, J ¼ 8.8 Hz, 2H, 3-H and 5-H, C6H4O), 6.62 (s, 1H, 7-
H), 4.74 (s, 2H, CH2O), 3.78 (t, J ¼ 7.3 Hz, 2H, CH2N), 1.65 (sext,
J ¼ 7.3 Hz, 2H, CH2CH3), 0.90 (t, J ¼ 7.3 Hz, 3H, CH3). 13C NMR and
DEPT (DMSO-d6): 166.67 (C), 158.23 (C), 156.32 (C), 139.65 (C), 135.28
(C), 134.22 (C), 133.12 (C), 129.02 (C), 127.21 (CH), 124.82 (C), 121.96
(CH), 121.85 (CH) 115.78 (CH), 115.49 (CH), 115.33 (CH), 112.08 (C),
92.78 (CH), 67.32 (CH2), 46.12 (CH2), 20.99 (CH2), 11.29 (CH3). MS (EI)
m/z (%): 437 (M þ 1, 11), 436 (100), 364 (3), 285 (79), 284 (37), 243
(29), 213 (5), 207 (1). Anal. Calcd for C23H21FN4O4 (436.44): C, 63.30;
H, 4.85; F, 4.35; N, 12.84. Found: C, 63.59; H, 4.55; F, 4.65; N, 13.17.
5.1.4.6. 2-[4-(2,4-Dioxo-3-propyl-2,3,4,5-tetrahydro-1H-pyrrolo[3,2-d]
pyrimidin-6-yl)phenyloxy]-N-(4-fluorophenyl)]acetamide [3f]. Yield
75%, mp > 370 ꢀC. IR (KBr)
n
(cmꢁ1): 2963, 2359, 1715, 1627, 1540,
1508, 1465, 1409, 1232, 1185, 1061, 829, 777. 1H NMR (DMSO-d6):
10.18 (s, 1H, D2O exchange, NHCO), 7.68e7.63 (m, 2H, 2-H and 6-H,
C6H4F), 7.51 (d, J ¼ 8.7 Hz, 2H, 2-H and 6-H, C6H4O), 7.18e7.11 (m, 4H,
3-H and 5-H, C6H4F and 3-H and 5-H, C6H4O), 6.20 (s, 1H, 7-H), 4.73
(s, 2H, CH2O), 3.86 (s, 3H, CH3N), 3.81 (t, J ¼ 7.4 Hz, 2H, CH2N), 1.56
(sext, J ¼ 7.3 Hz, 2H, CH2CH3), 0.86 (t, J ¼ 7.3 Hz, 3H, CH3). 13C NMR
and DEPT (DMSO-d6): 166.81 (CO), 158.15 (C4 C6H4O), 155.28 (C4
C6H4F), 151.42 (C4 and C2), 139.80 (C6), 135.05 (C4a), 134.16 (C1
C6H4F), 127.31 (C2 and C6 C6H4O), 124.46 (C1 C6H4O), 121.95 (C7a),
121.85 (C2 and C6 C6H4F),115.50 (C3 and C5 C6H4F),110.85 (C3 and C5
C6H4O), 94.75 (C7), 67.39 (OCH2), 42.08 (NCH2), 33.56 (NCH3), 31.79
(NCH3), 21.22 (CH2CH3), 11.51 (CH3). MS (EI) m/z (%): 436 (M, 100),
398 (85), 394 (49), 370 (86), 328 (28), 285 (69), 283 (51), 243 (92),111
(42) 86 (64), 72 (86), 58 (51), 43 (52). Anal. Calcd for C23H21FN4O4
(436.44): C, 63.30; H, 4.85; F, 4.35; N, 12.84. Found: C, 63.63; H, 4.49;
F, 4.64; N, 13.07.
5.1.4.3. 2-[4-(2,4-Dioxo-1-propyl-2,3,4,5-tetrahydro-1H-pyrrolo[3,2-d]
pyrimidin-6-yl)phenyloxy]-N-phenyl]acetamide [3c]. Yield 37%, mp
277e280 ꢀC. IR (KBr)
n
(cmꢁ1): 3181, 3034, 2966, 1684, 1548, 1490,
1439, 1381, 1184, 1118, 991, 766. 1H NMR (DMSO-d6): 12.19 (s, 1H,
D2O exchange, NH), 10.78 (s, 1H, D2O exchange, NHCO), 10.08 (s, 1H,
D2O exchange, NH), 7.82 (d, J ¼ 8.6 Hz, 2H, 2-H and 6-H, C6H5), 7.22
(t, J ¼ 7.7 Hz, 2H, 2-H and 6-H, C6H4O), 7.00e6.94 (m, 4H, 3-H and 5-
H, C6H4O and 3-H and 5-H, C6H5), 6.80 (t, J ¼ 7.1 Hz, 1H, 4-H, C6H5),
6.60 (d, J ¼ 1.2 Hz, 1H, CH), 4.92 (s, 2H, CH2O), 3.78 (t, J ¼ 7.0 Hz, 2H,
CH2N), 1.66 (sext, J ¼ 7.2 Hz, 2H, CH2CH3), 0.91 (t, J ¼ 7.3 Hz, 3H,
CH3). 13C NMR and DEPT (DMSO-d6): 166.76 (C), 158.26 (C), 151.24
(C), 151.17 (C), 139.73 (C), 138.73 (C), 129.13 (CH), 127.28 (CH), 127.21

2890
M.I. Nieto et al. / European Journal of Medicinal Chemistry 45 (2010) 2884e2892
5.1.4.7. 2-[4-(2,4-Dioxo-3-propyl-2,3,4,5-tetrahydro-1H-pyrrolo[3,2-d]
mixture was heated at 65 ꢀC for the time indicated. The reaction
mixture was allowed to cool down to room temperature and H2O
(15 mL) was added. The resulting precipitate was filtered off,
washed with H2O and dried under vacuum.
pyrimidin-6-yl)phenyloxy]-N-(4-bromophenyl)]acetamide [3g]. Yield
20%, mp > 305 ꢀC. IR (KBr)
n
(cmꢁ1): 3114 2962, 1720, 1627, 1531,
1489, 1465, 1397, 1234, 1186, 830, 750, 712. 1H NMR (DMSO-d6):
12.04 (s, 1H, D2O exchange, NH), 11.09 (s, 1H, D2O exchange,
NHCO), 10.23 (s, 1H, D2O exchange, NH), 7.81 (d, J ¼ 8.9 Hz, 2H, 3-H
and 5-H, C6H4Br), 7.61 (d, J ¼ 8.6 Hz, 2H, 2-H and 6-H, C6H4O), 7.50
(d, J ¼ 8.5 Hz, 2H, 2-H and 6-H, C6H4Br), 7.02 (d, J ¼ 8.5 Hz, 2H, 3-H
and 5-H, C6H4O), 6.19 (s, 1H, 7-H), 4.74 (s, 2H, CH2O), 3.80
(t, J ¼ 7.3 Hz, 2H, CH2N), 1.55 (sext, J ¼ 7.1 Hz, 2H, CH2CH3), 0.86
(t, J ¼ 7.3 Hz, 3H, CH3). 13C NMR and DEPT (DMSO-d6): 166.67 (C),
157.84 (C), 154.98 (C), 151.12 (C), 138.49 (C), 137.77 (C), 133.84 (C),
131.86 (CH), 127.06 (CH), 124.18 (C), 121.66 (CH), 115.40 (C), 115.04
(CH), 110.56 (C), 91.65 (CH), 67.13 (CH2), 41.07 (CH2), 21.05 (CH2),
11.22 (CH3). MS (EI) m/z (%): 498 (92), 497 (28), 496 (M, 92), 454
(42), 285 (72), 284 (47), 243 (100), 227 (47), 105 (23), 91 (20), 65
(13), 43 (16), 41 (15). Anal. Calcd for C23H21BrN4O4 (497.34): C,
55.54; H, 4.26; Br, 16.07; N, 11.27. Found: C, 55.63; H, 4.59; Br,
16.46; N, 11.48.
5.1.5.1. 2-[4-(1,5-Dimethyl-2,4-dioxo3-propyl-2,3,4,5-tetrahydro-1H-
pyrrolo[3,2-d]pyrimidin-6-yl)phenyloxy]-N-(4-fluorophenyl)acetamide
[3j]. Yield 30%, mp 195e196 ꢀC. IR (KBr)
n
(cmꢁ1): 1687, 1640,
1539, 1505, 1444, 1233, 1183, 1062, 829, 767. 1H NMR (DMSO-d6):
10.18 (s, 1H, D2O exchange, NHCO), 7.68e7.63 (m, 2H, 2-H and 6-H,
C6H4F), 7.50 (d, J ¼ 8.7 Hz, 2H, 2-H and 6-H, C6H4O), 7.19e7.11 (m,
4H, 3-H and 5-H, C6H4F and 3-H and 5-H, C6H4O), 6.25 (s, 1H, 7-H),
4.76 (s, 2H, CH2O), 3.86 (s, 3H, CH3N), 3.85e3.80 (m, 2H, CH2N),
3.34 (s, 3H, CH3N), 1.58e1.51 (m, 2H, CH2CH3), 0.85 (t, J ¼ 7.3 Hz,
3H, CH3). 13C NMR and DEPT (DMSO-d6): 166.59 (C), 158.25 (C),
155.28 (C), 150.89 (C), 142.64 (C), 135.72 (C), 135.04 (C), 130.72
(CH), 123.58 (C), 121.91 (CH), 121.81 (CH), 115.78 (CH), 115.50 (CH),
115.29 (CH), 110.40 (C), 94.75 (CH), 67.39 (CH2), 42.08 (CH2), 33.56
(CH3), 31.79 (CH3), 21.22 (CH2), 11.51 (CH3). MS (EI) m/z (%): 465
(M þ 1, 28), 464 (100), 422 (63), 271 (36), 270 (31), 138 (13), 124
(30), 110 (31), 83 (13). Anal. Calcd for C25H25FN4O4 (464.49): C,
64.64; H, 5.42; F, 4.09; N, 12.06. Found: C, 64.23; H, 4.35; F, 3.87;
N, 12.32.
5.1.4.8. 6-{4-[3-(4-Bromophenyl)-[1,2,4]oxadiazol-5-yl]carbonylmetho-
xyphenyl}-3-propyl-1,5-dihydro-3H-pyrrolo[3,2-d]pyrimidine-2,4-dione
[3h]. Yield 32%, mp > 300 ꢀC IR (KBr)
n
(cmꢁ1): 2963, 1698, 1628,
1495, 1468, 1405, 1345, 1275, 1248, 1181, 1065, 1009, 834, 783, 742.
1H NMR (DMSO-d6): 12.12 (s, 1H, D2O exchange, NH), 11.16 (s, 1H,
D2O exchange, NH), 7.95 (d, J ¼ 8.3 Hz, 2H, 3-H and 5-H, C6H4Br),
7.85 (d, J ¼ 8.5 Hz, 2H, 2-H and 6-H C6H4O), 7.79 (d, J ¼ 8.3 Hz, 2H,
2-H and 6-H, C6H4Br), 7.13 (d, J ¼ 8.5 Hz, 2H, 3-H and 5-H, C6H4O),
6.22 (s, 1H, H-7), 5.65 (s, 2H, CH2O), 3.84e3.79 (m, 2H, CH2N),
1.61e152 (m, 2H, CH2CH3), 0.88 (t, J ¼ 7.2 Hz, 3H, CH3). 13C NMR
and DEPT (DMSO-d6): 175.95 (C), 167.03, (C), 157.11 (C), 154.96 (C),
151.06 (C), 139.21 (C), 133.83 (C), 132.41 (CH), 128.99 (CH), 127.02
(CH), 125.36 (C), 124.89 (C), 124.82 (C), 115.05 (CH), 110.68 (C),
91.70 (CH), 60.81 (CH2O), 40.96 (CH2N), 20.98 (CH2CH3), 11.17
(CH3). MS (EI) m/z (%): 534 (4), 523 (15), 522 (4), 521 (15), 325
(34), 300 (24), 285 (28), 284 (62), 243 (78), 242 (99), 225 (29), 183
(95), 181 (87), 102 (100), 76 (22), 75 (40). Anal. Calcd for
C24H20BrN5O4 (522.35): C, 55.18; H, 3.86; Br, 15.30; N, 13.41.
Found: C, 55.36; H, 3.59; Br, 14.86; N, 13.78.
5.1.5.2. 6-[4-(4-Phenylpiperazin-1-yl)carbonylmethoxyphenyl]-5-me-
thyl-1,3-dipropyl-1,5-dihydro-3H-pyrrolo[3,2-d]pyrimidine-2,4-dione
[3k]. Yield 33%, mp 172e174 ꢀC. IR (KBr)
n
(cmꢁ1): 3432, 2963,
2932, 1653, 1581, 1466, 1382, 1181, 1044, 842, 769. 1H NMR (DMSO-
d6): 7.97 (d, J ¼ 8.4 Hz, 2H, 2-H and 6-H, C6H4O), 7.72e7.60 (m, 3H,
3-H, 4-H and 5-H, C6H5), 7.47 (d, J ¼ 8.3 Hz, 2H, 3-H and 5-H,
C6H4O), 7.05 (d, J ¼ 8.4 Hz, 2H, 3-H, 4-H and 5-H, C6H5), 6.27 (s, 1H,
7-H), 5.74 (virtual d, J ¼ 1.0 Hz, 2H, CH2O), 5.08e4.88 (m, 2H,
C4H8N2), 4.46e4.41 (m, 2H, C4H8N2), 4.09e4.01 (m, 4H, 2CH2N),
3.86 (virtual s, 4H, C4H8N2), 3.54 (s, 3H, CH3N), 1.64 (sext,
J ¼ 7.3 Hz, 2H, CH2CH3), 1.56 (sext, J ¼ 7.3 Hz, 2H, CH2CH3), 0.86
(virtual q, J ¼ 7.3 Hz, 6H, 2CH3). 13C NMR and DEPT (DMSO-d6):
165.57 (C), 158.73 (C), 155.34 (C), 150.71 (C), 143.84 (C), 142.85 (C),
135.18 (C), 131.04 (CH), 130.76 (CH), 130.67 (CH), 123.37 (C), 115.30
(CH), 110.74 (C), 94.76 (CH), 65.80 (CH2), 56.47 (CH), 47.03 (CH2),
33.61 (2CH3), 21.28 (CH2), 20.94 (CH2), 11.43 (CH3), 11.32 (CH3). MS
(EI) m/z (%): 543 (M þ 1, 35), 543 (100), 340 (16), 226 (8), 210 (7),
189 (12), 161 (30), 132 (58), 105 (20), 104 (15). Anal. Calcd for
C31H37N5O4 (543.66): C, 68.49; H, 6.86; N, 12.88. Found: C, 66.79;
H, 6.44; N, 12.51.
5.1.4.9. 6-[4-[3-(4-Bromophenyl)-[1,2,4]oxadiazol-5-yl]-(2-methoxy)
carbonylmethoxyphenyl]-1,3-dimethyl-1,5-dihydro-3H-pyrrolo[3,2-d]
pyrimidine-2,4-dione [3i]. Yield 27%, mp > 350 ꢀC. IR (KBr)
n
(cmꢁ1): 3670, 3644, 1828, 1668, 1622, 1605, 1590, 1573, 1474,
1416, 1284, 1267, 1154, 1084, 985, 920, 752, 702. 1H NMR (DMSO-
d6): 11.82 (s, 1H, D2O exchange, NH), 8.29e7.95 (m, 2H, 3-H and
5-H, C6H4Br), 7.94e7.78 (m, 1H, 6-H, C6H4O), 7.77e7.74 (m, 2H,
2-H and 6-H, C6H4Br), 6.85e6.77 (m, 1H, 5-H, C6H4O), 6.74
(d, J ¼ 2.1 Hz, 1H, 7-H), 6.51 (d, J ¼ 4.4 Hz, 1H, 3-H, C6H4O), 5.67
(s, 2H, CH2O), 3.87 (s, 3H, CH3O), 3.39 (s, 3H, CH3), 3.24 (s, 3H,
CH3). 13C NMR and DEPT (DMSO-d6): 176.64 (C), 167.78 (C),
159.20 (C), 158.24 (C), 155.14 (C), 151.32 (C), 136.23 (C), 133.54 (C),
133.18 (CH), 130.00 (CH), 129.91 (CH), 126.12 (C), 125.52
(C), 106.80 (CH), 100.54 (CH), 95.65 (CH), 79.91 (CH2), 58.32
(CH3), 32.41 (2 CH3). MS (EI) m/z (%): 539 (M þ 1, 23), 538 (4),
537 (22), 358 (14), 301 (24), 300 (100), 257 (24), 209 (15), 207
(11), 183 (14), 181 (12), 102 (7), 58 (6). Anal. Calcd for
C24H20BrN5O5 (538.35): C, 53.54; H, 3.74; Br, 14.84; N, 13.01.
Found: C, 53.66; H, 3.33; Br, 14.56; N, 13.38.
5.1.5.3. 6-[4-(1,2,3,4-Tetrayidroisoquinolin-2-yl)]carbonylmethoxyph-
enyl]-5-methyl-1,3-dipropyl-1,5-dihydro-3H-pyrrolo[3,2-d]pyrimidine-
2,4-dione [3l]. Yield 63%, mp 121e123 ꢀC. IR (KBr)
n
(cmꢁ1): 3461,
2963, 2934, 1691, 1650, 1536, 1473, 1455, 1243, 1051, 1000, 767,
746. 1H NMR (DMSO-d6): 7.48 (d, J ¼ 7.9 Hz, 2H, 2-H and 6-H,
C6H4O), 7.19 (virtual s, 4H, 3-H, 5-H, C6H4O and 5-H, 8-H, C9H10N),
7.13e7.05 (m, 2H, 6-H and 7-H, C9H10N), 6.30 (s, 1H, 7-H), 5.01
(s, 2H, CH2O), 4.62 (s, 2H, 1-H2, C9H10N), 3.97e3.94 (m, 5H, 3-H2,
C9H10N and CH3N), 3.76e3.67 (m, 4H, 2CH2N), 2.98e2.88 (m, 2H,
CH2N), 2.85e2.80 (m, 2H, 4-H2, C9H10N), 1.69e1.49 (m, 4H,
2CH2CH3), 1.00e0.77 (m, 6H, 2CH3). 13C NMR and DEPT (DMSO-
d6): 166.64 (C), 158.85 (C), 155.27 (C), 150.65 (C), 142.85 (C), 135.12
(C), 134.77 (C), 133.452 (C), 133.30 (C), 130.64 (CH), 128.70 (CH),
128.76 (CH), 126.78 (CH), 126.51 (CH), 123.27 (C), 115.18 (CH),
110.48 (C), 94.69 (CH), 66.34 (CH2), 46.33 (CH2), 45.92 (CH2), 43.94
(CH2), 42.12 (CH2), 41.98 (CH2), 33.54 (CH3), 28.92 (CH2), 21.21
(CH2), 20.87 (CH2), 11.54 (CH3), 11.31 (CH3). MS (EI) m/z (%): 515
(M þ 1, 34), 514 (100), 430 (11), 340 (14), 174 (21). Anal. Calcd for
C30H34N4O4 (514.26): C, 70.02; H, 6.66; N, 10.89. Found: C, 70.45;
H, 6.44; N, 10.58.
5.1.5. General procedure for the methylation of compounds 8 and
10aec
CH3I (0.40 mmol) was added to a stirred suspension of the
corresponding 1H-purine-2,6(3H,7H)-dione
8
and 10aec
(0.20 mmol) and K2CO3 (25 mml) in dry DMF (3 mL) and the

M.I. Nieto et al. / European Journal of Medicinal Chemistry 45 (2010) 2884e2892
2891
5.1.5.4. 2-[4-(5-Methyl-2,4-dioxo-1,3-dipropyl-2,3,4,5-tetrahydro-1H-
regression using Prism 2.1 software (GraphPad, San Diego, CA). For
pyrrolo[3,2-d]pyrimidin-6-yl)phenyloxy]-N-(4-fluorophenyl)acetamide
those compounds that showed either little affinity or poor solu-
bility a percentage of inhibition of specific biding at 1 mM is
[3m]. Yield 61%, mp 169e171 ꢀC. IR (KBr)
n
(cmꢁ1): 3347, 2962, 2935,
1696,1650,1531,1507,1477,1455,1409,1239,1227,1065, 834, 770.1H
NMR (DMSO-d6): 10.19 (s, 1H, D2O exchange, NHCO), 7.68e7.63 (m,
2H, 2-H and 6-H, C6H4F), 7.52 (d, J ¼ 8.3 Hz, 2H, 2-H and 6-H, C6H4O),
7.19e7.11 (m, 4H, 3-H, 5-H, C6H4F and 3-H, 5-H, C6H4O), 6.30 (s,1H, 7-
H), 4.77 (s, 2H, CH2O), 3.87 (s, 3H, CH3N), 3.87e3.45 (m, 4H, 2CH2N),
1.65e1.63 (m, 2H, CH2CH3), 1.56e1.54 (m, 2H, CH2CH3), 0.90e0.83
(m, 6H, 2CH3). 13C NMR and DEPT (DMSO-d6): 166.58 (C), 158.50 (C),
155.27 (C), 150.64 (C), 142.71 (C), 135.11 (C), 130.78 (CH), 123.56 (C),
121.91 (CH), 121.80 (CH), 115.77 (CH), 115.48 (CH), 115.24 (CH), 110.52
(C), 94.75 (CH), 67.38 (CH2), 46.33 (CH2), 41.98 (CH2), 33.55 (CH3),
21.21 (CH2), 20.86 (CH2), 11.48 (CH3),11.24 (CH3). MS (EI) m/z (%): 493
(M þ 1, 31), 492 (100), 450 (14), 409 (11), 408 (43), 378 (21), 257 (25),
256 (12), 227 (26), 124 (21), 110 (20), 58 (26). Anal. Calcd for
C27H29FN4O4 (492.54): C, 65.84; H, 5.93; N, 11.38. Found: C, 65.59; H,
5.72; N, 11.17.
reported.
Results are the mean of 2 experiments (n ¼ 2), each performed
with duplicate points.
Selectivity is defined by the ratios Ki(A2A)/Ki(A2B) or Ki(A1)/
Ki(A2B).
Acknowledgments
The authors thank Almirall Prodesfarma S.A. (Barcelona-Spain)
for promoting and financially supporting this work. I. N. thanks the
Xunta de Galicia for financial support under “Programa Isidro Parga
Pondal”. J. B. thanks the Xunta de Galicia for financial support under
“Isabel Barreto Contract”.
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