New insight into adenosine receptors selectivity derived from a novel series of [5-substituted-4-phenyl-1,3-thiazol-2-yl] benzamides and furamides

Article abstract of DOI:10.1016/j.ejmech.2013.03.020

A series of [5-substituted-4-phenyl-1,3-thiazol-2-yl] benzamide and furamide analogues were investigated in radioligand binding studies at adenosine receptor subtypes with an aim to obtain potent and selective adenosine receptor ligands. Benzamide and furamide linked to thiazole was found to be crucial for high adenosine receptor affinity. The most potent compound indentified in this study was 5d with low nanomolar affinity for all four adenosine receptor subtypes. Compounds 5a and 5g showed moderate selectivity for A_2A adenosine receptors. Molecular docking versus all four human adenosine receptors combined with membrane molecular dynamics studies were performed to rationalise the peculiar selectivity profile of 5d antagonist.

Full text of DOI:10.1016/j.ejmech.2013.03.020

European Journal of Medicinal Chemistry 63 (2013) 924e934
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
New insight into adenosine receptors selectivity derived from a novel
series of [5-substituted-4-phenyl-1,3-thiazol-2-yl] benzamides and
furamidesq
Gajanan S. Inamdar a, Amit N. Pandya a, Hardik M. Thakar a, Vasudevan Sudarsanam a,
,
Sonja Kachler b, Davide Sabbadin c, Stefano Moro c, Karl-Norbert Klotz b, Kamala K. Vasu a
*
a Department of Medicinal Chemistry, B.V. Patel Pharmaceutical Education and Research Development, Ahmedabad 380 054, Gujarat, India
b Institut für Pharmakologie und Toxikologie, Julius-Maximilians-Universität Würzburg, Versbacher Str. 9, D-97078 Würzburg, Germany
c Molecular Modeling Section (MMS), Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via Marzolo, 5, 35131 Padova,
Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of [5-substituted-4-phenyl-1,3-thiazol-2-yl] benzamide and furamide analogues were investi-
gated in radioligand binding studies at adenosine receptor subtypes with an aim to obtain potent and
selective adenosine receptor ligands. Benzamide and furamide linked to thiazole was found to be crucial
for high adenosine receptor affinity. The most potent compound indentified in this study was 5d with
low nanomolar affinity for all four adenosine receptor subtypes. Compounds 5a and 5g showed moderate
selectivity for A2A adenosine receptors. Molecular docking versus all four human adenosine receptors
combined with membrane molecular dynamics studies were performed to rationalise the peculiar
selectivity profile of 5d antagonist.
Received 22 June 2012
Received in revised form
21 February 2013
Accepted 9 March 2013
Available online 22 March 2013
Keywords:
2-Aminothiazole
Adenosine receptors
Selectivity profile
Ó 2013 Elsevier Masson SAS. All rights reserved.
Structure activity relationship
Receptor models
Molecular docking
Membrane molecular dynamics
1. Introduction
Ca2þ-signaling and the mitogen-activated protein kinases (MAPK)
pathway [1].
Over the past few decades, much attention has been focused on
the development of ligands for adenosine receptors subtypes, since
there is significant potential to address dysfunction in range of
diseases and to design, drug like candidates in wide range of
therapeutic areas. However, there is a need for the specificity or
significant selectivity towards individual receptor subtypes. The
ubiquitous tissue distribution of adenosine receptors is largely
responsible for the broad variety of effects produced by adenosine
throughout several organ systems. Adenosine receptors are classi-
fied into three types, namely A1, A2 and A3; the A2 receptors are in
turn sub-classified into two subtypes, A2A and A2B. Adenosine re-
ceptor signalling is diverse and occurs through inhibition or stim-
ulation of adenylyl cyclase, activation of phospholipase C (PLC),
Activation of the A1AR mediates an inhibition of adenylyl cyclase
through activation of pertussis toxin-sensitive Gi/o proteins [2,3]
and results in increased activity of PLC [4,5]. High and intermedi-
ate levels of A1 Adenosine receptor expression were found in the
brain, heart, adipose tissue, stomach, vas deferens, testis, spleen,
kidney, aorta, liver, eye and bladder [6]. A1 agonists may find
application in various diseases and disorders such as stroke, epi-
lepsy, migraine, pain, cardiac ischemia, arrhythmias, while antag-
onists may be useful in conditions such as cognitive disorders and
oedema [7].
Activation of the A2A AR increases adenylyl cyclase activity
mediated by Gs as the major G-protein associated with A2A. The A2A
AR is also known to act through Golf [8] in the striatum and was
shown to activate the PLC pathway in rat artery [9].
The A2A adenosine receptors are highly expressed in the stria-
tum, nucleus accumbens, and olfactory tubercle [6]. High and in-
termediate expression levels were also found in immune cells,
heart, lung and blood vessels. The therapeutic implications of A2A
q
Communication no. PERD-040512.
* Corresponding author. Tel.: þ91 79 27439375; fax: þ91 79 27450449.
E-mail addresses: kamkva@gmail.com, perd@perdcentre.com (K.K. Vasu).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.03.020

G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
925
Adenosine receptor agonists result from cardiovascular effects such
as vasodilation, tachycardia (central effects), hypotension (periph-
eral effects), and platelet aggregation. Additional therapeutic in-
dications for agonists may be respiratory disorders, rheumatoid
arthritis, inflammation, wound healing, and sepsis, while antago-
nists are discussed as treatment in Parkinson’s disease, neuronal
protection in ischemia, Huntington’s disease and migraine [7].
The A2B adenosine receptor is positively coupled to both ade-
nylyl cyclase and PLC [10e13]. Inhibition of A2B ARs may be useful in
diarrhoea, diabetes and asthma.
The A3 ARs are coupled to the classical second-messenger path-
ways such as inhibition of adenylyl cyclase [14], stimulation of PLC
[15] and calcium mobilization [16e19]. A protective effect on cardiac
cells was shown to be mediated through the activation of KATP
channels [20]. A3 adenosine receptor activation may find applica-
tions in stroke, lung injury (asthma and COPD), cardiac ischemia,
rheumatoid arthritis and cancer [21]. The blockade of A3 adenosine
receptor is useful in glaucoma, asthma and renal failure [7].
One of the hottest topics in targeting GPCRs is to define the
selectivity profile of both agonists and antagonists against the
different receptor subtypes. The understanding at the molecular
level of the receptor-ligand requirements to improve the selectivity
profiles can be achieved integrating structure activity relationship
with computational studies. In fact, we have previously shown that
the decoration of 2-aminothiazole scaffold, with an aroylamino
moiety at the 2 position and an aroyl moiety at the 5 position
respectively, shifts the selectivity profile versus the human A1 re-
ceptor [22]. With the aim to obtain better rationalize for the
observed this selectivity profile shift, we designed a novel series of
[5-substituted-4-phenyl-1,3-thiazol-2-yl] benzamide and furamide
derivatives. Interestingly, we have identified compound 5d with
lower nanomolar antagonist against all four adenosine receptor
subtypes. Compound 5d represents a very special chemical entities
among all known adenosine receptor antagonists, because it hed-
ges in its structure the most critical chemical features essential for
the recognition of all four adenosine receptor subtypes. Molecular
docking versus all four human adenosine receptors combined with
membrane molecular dynamics studies have been performed to
rationalise the peculiar selectivity profile of this novel antagonist.
of diethyl amine. These isothiocyanates were utilized further for the
synthesis of various amidinothioureas (3aed, Scheme 1) by treat-
ing with N,N-diethyl benzamidine in a suitable solvent at condi-
tions (10e25 ꢀC). These amidinothioureas (3aed) were then
reacted with substituted halomethylene compounds to get the
desired 2-aminothiazole derivatives (Scheme 1).
Several halomethyl compounds were synthesized for the pur-
pose of diverse substitutions at 5 position on the 2-aminothiazole
core ring. The compound (A, Fig. 1) had selectivity towards A3
adenosine receptor. This compound 1 incorporates a 4-pyridyl
which has a hydrogen bond acceptor feature at the 5-position of
the 2-aminothiazole scaffold. The importance of this feature was
reinforced by the benzoyl (B, Fig. 1) in our own work [22]. The lone
pair of electrons on the carbonyl oxygen simulates the nitrogen pair
of the pyridyl candidates. The bioisosteric equivalence of pyridyl
with the benzoyl is well established [25].
In order to evaluate whether additional hydrogen bond acceptor
feature at the 5-position would have beneficial effect on biological
activity profile, The pyridyl in the compound (A, Fig.1) was replaced
with 4-amino-6-dimethylamino-2-chloromethyl[1,3,5]triazine, 2-
chloromethyl-5,6-dimethyl-thieno[2,3-d]pyrimidin-4-ylamine and
the 2-chloromethyl-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyr-
imidin-4-yl amine fragments. Further, to retain the fragments of
carbonyl and pyridyl nitrogen as hydrogen bond acceptors
respectively in single molecule at 5-position, various analogues
were synthesized with 2-pyridoyl, 3-pyridoyl and 4-pyridoyl at the
5-position of the 2-aminothiazole scaffold.
The triazine ring was constructed using an anti-diabetic drug
metformin hydrochloride as the starting material where metformin
hydrochloride was treated with chloroethyl acetate in dry meth-
anol under basic conditions [26] to furnish chloromethyl-2,4-
disubstituted triazine (Scheme 2).
The thieno[2,3-d]pyrimidines were synthesised using the
method reported by Dave et al. [27]; where the 2-amino-5,6-
dimethyl-thiophen-3-carbonitrile was obtained using ethyl-
methylketone, malononitrile, sulphur and morpholine as base us-
ing Gewald synthesis and later was cyclised to thienopyrimidines
using strong acidic conditions with chloroacetonitrile to yield
compound 13 (Scheme 3).
Similarly, synthesis of 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-
d]pyrimidin-4-yl amine was carried out using Gewald reaction with
cyclohexanone, malononitrile and sulphur followed by cyclization
with chloroacetonitrile in presence of acid resulted in compound 16
(Scheme 4).
2. Results and discussion
The synthesis of the 2-aminothiazole derivatives was performed
according to procedures by Rajappa et al. [23]. Initially, various
benzoyl and 2-furanoyl isothiocyanates were synthesised using the
method reported by Preston Reeves W. et al. [24] where in a
mixture of benzoyl or 2-furanoyl chloride, benzene and tetra butyl
ammonium bromide was stirred at room temperature, followed
by addition of 33% potassium thiocyanate solution drop-wise.
N,N-diethyl benzamidine was prepared by treating benzonitrile at
0e30 ꢀC with anhydrous aluminium chloride followed by addition
3. Structure activity relationships
3.1. Benzamide derivatives
The activity profiles of 2-aminothiazole analogues are outlined
in Table 1. Comparison of the activity profile at the receptor
Scheme 1. Synthesis of 2-aminothiazole derivatives (4ae4k, 5ae5i).

926
G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
at the 2-position produced ligands with slightly higher affinity for
the adenosine receptor subtypes. The 2-pyridoyl substitution in 5
position leads to ligand 5a with good affinity at the A2A adenosine
receptor (Ki ¼ 74.7 nM) and with some selectivity towards A1 and
A3 (5 and 13 fold, respectively) (Table 2). The 3-pyridoyl at 5 po-
sition binds generally with lower affinity as the 2-pyridoyl. Com-
pound 5d with a 4-pyridyl is striking as it shows sub-nanomolar
affinity for the A1 adenosine receptor with an about 11 and 16 fold
selectivity versus the A2A and A3 receptor, respectively. In addition,
it also shows very high A2B affinity (Ki ¼ 2.8 nM) which distin-
guishes it as one of the most potent non-xanthine antagonists at
this receptor subtype. The respective 2-pyridyl 5c exhibits much
lower affinity at all receptor subtypes (30 fold at A2A to 480 fold at
the A1). The 5-substitution with a thieno[2,3-d]pyrimidine pro-
duced compound 5e with low affinity at A3 receptors (Ki ¼ 746 nM)
and some selectivity over A1 (16 fold), A2A (8 fold) and A2B (>13
fold) receptors. Some A2A selectivity was observed for the com-
pound bearing a diamino triazine in 5 position 5g with an A2A Ki of
179 nM it is 3 fold, 20 fold and 5 fold selective compared to the A1,
A2A and A3 adenosine receptor, respectively. The 5 position sub-
stitution with a thieno[2,3-d]pyrimidin-4-one 5h and quinazolin-
4-one 5i resulted in compounds with marginal affinity.
Molecular modelling studies were carried out to rationalize the
unique potency and selectivity profiles provided by derivative 5d,
suggesting us that the incorporation of the 4-pyridyl moiety in
the furamido-thiazole scaffold guarantees the presence of all crit-
ical chemical features essential for the recognition of the four
adenosine receptor subtypes. As detailed into the Supplementary
information section, starting from the crystallographic structure
of the human A2A adenosine receptor co-crystallized with the
6-(2,6-dimethylpyridin-4-yl)-5-phenyl-1,2,4-triazin-3-amine (PDB
ID: 3UZA) [30], we have constructed using homology modeling
technique the homologous A1, A2B and A3 receptors. We decided to
select this specific crystallographic structure as a template because
we found an interesting chemical similarity between the 6-(2,6-
dimethylpyridin-4-yl)-5-phenyl-1,2,4-triazin-3-amine and our 5d
antagonist (furan-2-carboxylic acid (4-phenyl-5-pyridin-4-yl-thia-
zol-2-yl)-amide).
Molecular docking studies have been performed using a very
well consolidated protocol, previously reported [31], and deeply
described in the Supplementary information section. Interestingly,
we found energetically favourable poses of 5din all four adenosine
receptor subtypes with a very conserved binding motif. In order
to provide a direct comparison between selected compounds and
all the human adenosine receptors interaction patterns, key resi-
dues involved in binding with the considered ligands along with a
quantitative estimate of the occurring ligandeprotein interactions
have been reported as “Interaction Energy Fingerprints” (hereby
indicated as IEFs), and are graphically displayed either as histo-
grams or as 3D colour maps.
The individual electrostatic and hydrophobic contributions to
the interaction energy of each receptor residue with 5d ligand have
been calculated and the corresponding results were collected in
Fig. 2, whereas the IEFs of hA2A AR with 5a, 5b, 5c and 5d have been
reported in Fig. S1 (Supporting information) Consistently with
their structural similarity, 5d shares the same binging orientation
observed for the 6-(2,6-dimethylpyridin-4-yl)-5-phenyl-1,2,4-
triazin-3-amine antagonist co-crystallized with the human
A2A receptor [30]. In particular, the furamido moiety of the
5-substituted-4-phenyl-1,3-thiazol-2-yl derivatives is directed to-
wards the extracellular side of all human adenosine receptors as
shown for compound 5d in Fig. 2. The phenyl ring in 4 position is
directed towards the conserved His6.52 and Trp6.48, interacting
with the hydrophobic side-chains of Leu3.33 and Val3.32 (Val87,
Val84 and Val85 in A1, A2A and A2B ARs, respectively) or Leu3.32
Fig. 1. Some potent and selective adenosine receptor ligands with 2-aminothiazole
scaffold.
subtypes seem to indicate that hetero-aryl/aroyl substitution lead
to better active and selective compounds compared to aroyl sub-
stitutions (2, Fig. 1). Here benzoyl substituent was replaced by 2-
pyridoyl and 3-pyridoyl substituents (4ae4b). The 2-pyridoyl had
moderate affinity, while the 3-pyridoyl analogue showed no
binding in concentrations up to 10
mM. The 2-pyridoyl and
3-pyridoyl analogues showed limited A2A selectivity (5.7 and 4 fold
over A1 and 3.4 and 2 fold over A3, respectively), further no
measurable affinity for A2B receptors was observed. This implies
that a 2-pyridoyl or 4-pyridoyl substituent is well tolerated by the
all receptor subtypes and found more selective towards A2A re-
ceptor subtypes. Replacing the pyridoyl ring with amino-triazine
4ce4e produced ligands with good activity but with loss of
selectivity for the receptor subtypes. However, the triazine-
substituted thiazoles can be used as lead compounds for further
structural modification. The dimethylthieno-pyrimidin-2-yl-4-
amine substitution at 5 position of the thiazole gave encouraging
activity as these analogues 4fe4h showed medium to strong af-
finity and selectivity towards the adenosine A3 receptors. However,
tetrahydro-benzo[4,5]thieno[2,3-d]pyrimidin-2-yl-4-amine ana-
logues 4ie4k showed low affinity. The low binding affinity in the
case of the tetrahydro-benzo[4,5]thieno[2,3-d]pyrimidin-2-yl-4-
amine could possibly be due to an unfavourable steric bulk
(Table 1).
3.2. Furamide derivatives
Furan is a structural fragment which can be considered as a
bioisostere of the corresponding benzamido compounds. The furan
group is present in block buster drugs like ranitidine, furosemide or
cefuroxime and is also widely used as a building block for adeno-
sine receptor antagonists like CGS 15943, SCH 58261 or MRE
3008F20 [28]. Furthermore, the furan heterocycles with the
2-amino substituent is found to be an important pharmacophore
for selective A2A receptor antagonists [29]. Based on this report, we
replaced the benzoyl substitution at 2 position of 2-aminothiazole
(Table 2) to 2-furanoyl and assessed the effect of different sub-
stituents at the 5 position of the 2-aminothiazole.
The results for the furamido compounds are summarised in
Table 2. In general, the replacement of the benzamido substituent
Scheme 2. Synthesis of halomethylene triazine derivatives.

G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
927
Scheme 3. Synthesis of thieno[2,3-d]pyrimidine derivatives.
(Leu90 in A3 AR). The substituted aminothiazole ring makes
favourable hydrophobic interactions also with Leu6.51 (Leu250,
Leu249 and Leu246 in A1, A2A and A3 ARs respectively) or Val6.51
within the residues that constitutes the binding pocket of ARs
models (Fig. S1), is directed towards a cleft formed by Val3.32,
Ile2.64 and Ala2.61 in A1, A2A and A2B ARs, or by Leu3.32, Val2.64
and Ala2.61 in A3 AR.
(Val250 in A2B AR). An additional
pep stacking interaction occurs
between the conserved Phe168 side chain (A2A AR), located in the
second extracellular loop of adenosine receptors, and the amino-
thiazole scaffold.
Additionally, the time-dependent stability of the receptore
ligand interaction network has been addressed using membrane
molecular dynamics simulations. Dynamic “Interaction Energy
Fingerprints” between compound 5d and all adenosine receptor
subtypes are graphically displayed as 3D colour maps in Fig. 3. The
best docking poses of compound 5d in all adenosine receptor
subtypes (Fig. 2) were used as starting point for the simulations.
Moreover, as detailed into the Supplementary information, the
individual electrostatic and hydrophobic contributions to the
interaction energy of each receptor residue with 5d ligand have
been calculated over the nanoseconds time scale trajectories, every
100 ps after the equilibration period of each built system has been
reached, as shown in Fig. 3 per each receptor. Globally, the high-
affinity compound 5d showed to have a modest fluctuation from
Focusing our attention on the “non selective” profile of com-
pound 5d, the 4-pyridyl ring attached in 4 position of the 2-
aminothiazole scaffold is directed towards the very conserved
His7.43. The endocyclic nitrogen atom of pyridine can accept a
hydrogen bond from the previously cited residue side chain. Addi-
tional important hydrogen bonding interactions are present be-
tween the nitrogen atoms of the substituted 2-aminothiazole core
and the conserved Asn6.55.
The low nanomolar affinity of compound 5d for all four human
adenosine receptor subtypes can be rationalized observing the
peculiar hydrophobic and electrostatic interaction pattern between
the selected furamide and the receptor subtypes reported in Fig. 2.
The conserved Asn6.55 and His7.43 are responsible of providing
most of the electrostatic interactions with the cited ligand. A dra-
matic loss in potency is shown when the hydrogen bonding inter-
action with His7.43 is abolished. Docking results showed that 2-
pyridyl derivatives at 4 position of the 2-aminothiazole ring are
able to establish a strong hydrogen bonding interaction with the
conserved Asn6.55 side chain in all human adenosine receptor
subtypes, but are unable to adopt the correct geometrical confor-
mation to create an additional hydrogen bond with the conserved
His7.43. As proof of concept, the 2-pyridyl at 5 position (compound
5c) consistently reduces the binding affinities against all adenosine
receptors subtypes (Table 2). In fact, the analysis of the IEF, asso-
ciated to the predicted binding mode of compound 5c with A2A AR
and reported in Fig. S1, shows that His7.43 does not play a signifi-
cantly role in ligand binding.
Moreover, the molecular docking studies of compound 5a and
5b emphasize the importance of how a critical molecular engi-
neering, of the aminothiazole scaffold, is a key point to obtain
potent and non-selective ARs antagonists. The analysis of the pre-
dicted binding conformations of compound 5a and 5b highlighted
that both nitrogen atoms, which are part of the 2-aminothiazole
aromatic ring, make hydrogen bonding interactions with the
conserved Asn6.55 side chain. Beside maintaining the same scaffold
orientation and a similar pattern of ligand-receptor hydrophobic
contacts, as shown in Fig. S1 for A2A AR, the carbonyl spacer, that
connects the pyridine ring and the 2-aminothiazole core, prevent
the cited-above compounds to adopt the correct geometrical
orientation in order to create an additional hydrogen bond with the
conserved His278. In fact, the pyridoyl moiety of compound 5a and
5b, which is not involved in any hydrogen bonding interaction
ꢀ
the original starting position (r.m.s.d. < 2.5 A). The deep analysis of
Fig. 3 shows a persistent and strong electrostatic contribution of
Asp253 and His278 to the 5d binding energetics in all human
adenosine receptors. Additionally, in A1, A2A and A2B receptors the
recruitment of the polar Glu169 through
a water-mediated
hydrogen-bonding interaction to the amide moiety of 5d in-
creases its stability of interaction with the orthosteric binding
pockets. In addition to the electrostatic contribution, a cooperative
and stable network of hydrophobic interactions contributes to the
stabilization of 5d into all adenosine receptor subtypes, as shown in
Figs. 2 and 3. It is worth to underline the interaction between 5d
and the conserved Phe, located in the second extracellular loop of
adenosine receptor subtypes (Phe171, Phe168. Phe173 and Phe168
in A1, A2A, A2B and A3, respectively), with Leu6.51 (Leu250, Leu249
and Leu246 in A1, A2A and A3, and mutated in valine in A2B) and
Ile7.39 (Ile274, Phe274. Phe276 and Phe268 in A1, A2A, A2B and A3,
respectively). An intense hydrophobic contribution of Val169 in A3
AR, clearly visible in Fig. 3. Moreover, favourable hydrophobic in-
teractions are found to be persistent with an additional contribu-
tion is due to the favourable contact between the conserved F168
side chains (A2A AR), located Adenosine Receptors, and the ami-
nothiazole ring. Compound 5b interacts with the hydrophobic side-
chains of the conserved Leu3.33 and Val3.32 (Val87, Val84 and
Val85 in A1, A2A and A2B ARs respectively) or Leu3.32 (Leu90 in A3
AR) and with His6.52 and Trp6.48.
4. Conclusion
A series of 24 [5-substituted-4-phenyl-1,3-thiazol-2-yl] benza-
mides and furamides derivatives was synthesized and pharmaco-
logically evaluated at the adenosine receptors subtypes A1, A2A, A2B
Scheme 4. Synthesis of 5,6,7,8-tetrahydrobenzothieno[2,3-d]pyrimidine derivatives.

928
G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
Table 1
Benzamide compounds with biological activities (4ae4k).
Compound
R1
R2
Ki (nM) (95% confidence limits)
a
hA1
hA2A
hA2B
hA3
4a
4b
4-OMeeC6H4
4-OMeeC6H4
2-Pyridoyl
3-Pyridoyl
688 (614e769)
>10,000
128 (87.9e186)
>10,000
>10,000
>10,000
201 (166e243)
>10,000
4c
4-OMeeC6H4
10,400 (7310e14,800)
2010 (1730e2340)
>10,000
2640 (1.970e3530)
4d
4e
4-MeeC6H4
C6H5
3630 (2890e4570)
801 (695e923)
562 (469e673)
327 (264e405)
>30,000
>10,000
816 (517e1290)
567 (452e712)
4f
4-OMeeC6H4
>100,000
>30,000
>10,000
2470 (2090e2910)
4g
4h
4-MeeC6H4
C6H5
>30,000
7240 (6380e8220)
>30,000
4870 (4050e5860)
>10,000
>10,000
1380 (798e2400)
676 (599e762)
4i
4-OMeeC6H4
>10,000
>10,000
>10,000
>10,000
4j
4k
4-MeeC6H4
C6H5
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
Data are expressed as geometric means, with 95% confidence limits in parentheses.
a
Inhibition of NECA-stimulated adenylyl cyclase activity. N.T., not tested.
and A3. Notably, we have identified compound 5d as a low nano-
molar antagonist versus all four adenosine receptor subtypes. The
added value of this novel potent and non-selective antagonist is to
incorporate in its structure all common chemical features for the
recognition of all four adenosine receptor binding sites. Moreover,
5d could represent a special building block to design novel potent
and selective antagonists, in particular human against the A2B re-
ceptors. Molecular docking against all four human adenosine re-
ceptors combined with membrane molecular dynamics studies
have been performed to rationalise the peculiar selectivity profile
of this novel antagonist.
(q, 2H, eNeCH2eCH3); 7.2e7.4 (m, 10H, C6H5, COeC6H5), 9 (s,
1H, NH).
5.2.2. 1-[1-Diethylamino-1-phenyl-meth-(E)-ylidene]-3-(4-methyl-
benzoyl)-thiourea[3b]
The titled compound was synthesised by adding to a stirred
solution of p-methyl benzoyl isothiocyanate (0.0282 mol) in 5 ml
toluene, with N,N-diethyl-benzamidine (0.0282 mol) at ꢁ5 to 0 ꢀC.
The solution was stirred for 3 h at ambient temperature and the
separated solid was filtered and washed with hexane and dried to
yield adducts 3b as pale yellow crystals %Yield: 56, LCMS: (M þ 1) at
354, Molecular Formula e C20H23N3OS, m.p. ¼ 118e119 ꢀC. Rf: 0.44
(Toluene:EtOAc::8:2).
5. Experimental section
5.1. General methods
5.2.3. 1-[1-Diethylamino-1-phenyl-meth-(E)-ylidene]-3-(4-methoxy-
benzoyl)-thiourea [3c]
Melting points are uncorrected. 1H NMR (400 MHz) and 13C
NMR (75 MHz) spectra were measured in CDCl3, CD3OD or DMSO-
d6, and chemical shifts are reported in parts per million (
field from tetramethylsilane as internal standard.
The titled compound was synthesised by adding to a stirred
solution of p-methoxy benzoyl isothiocyanate (0.0282 mol) in 5 ml
toluene, N,N-diethyl benzamidine (0.0282 mol) at ꢁ5 to 0 ꢀC. The
solution was stirred for 3 h at ambient temperature and the sepa-
rated solid was filtered and washed with hexane and dried to yield
adduct 3c as light yellow crystals. %Yield: 58, LCMS: (M þ 1): 371,
Molecular Formula e C20H23N3O2S. m.p. ¼ 123 ꢀC. 1H NMR
d) down-
5.2. Synthesis
5.2.1. 1-Benzoyl-3-[1-diethylamino-1-phenyl-meth-(E)-ylidene]-
thiourea [3a]
(400 MHz, CDCl3)
d
ppm ¼ 1.1e1.3 (t, 3H, eNeCH2eCH3); 1.4e1.6 (t,
3H, eNeCH2eCH3); 3.2e3.4 (q, 2H, eNeCH2eCH3); 3.6e3.8 (q, 2H,
eNeCH2eCH3); 3.9 (s, 3H, eOCH3), 6.90e7.0 (d, 2H, Ar); 7.3e7.5 (m,
5H, eC6H5); 7.7e7.8 (d, 2H, Ar); 9 (s, 1H, NH).
The titled compound was synthesised by adding to a stirred
solution of benzoyl isothiocyanate (0.0282 mol) in 5 ml toluene,
N,N-diethyl-benzamidine (0.0282 mol) at ꢁ5 to 0 ꢀC. The solution
was stirred for 3 h at ambient temperature and the separated solid
was filtered and washed with hexane and dried to yield 3a as
yellow crystals, %Yield: 56, LCMS: (M þ 1): 340, Molecular Formula
eC19H21N3OS, m.p. ¼ 110e112 ꢀC. Rf: 0.35 (Dichloromethane). 1H
5.2.4. 1-[1-Diethylamino-1-phenyl-meth-(Z)-ylidine]-3-(furan-2-
carbonyl)-thiourea [3d]
To a solution of Furoyl isothiocyanate (0.0654 mol) in 5% ethyl ac-
etate in Petroleum ether (60e80 ꢀC), cooled to ꢁ5 to 0 ꢀC, neat N,N-
diethyl benzamidine (0.0654 mol) was added drop wise such that the
temperature does not go beyond 5 ꢀC. The solution was stirred
NMR (400 MHz, CDCl3)
1.6 (t, 3H, eNeCH2eCH3); 3.2e3.4 (q, 2H, eNeCH2eCH3); 3.6e3.8
d
ppm ¼ 1.1e1.3 (t, 3H, eNeCH2eCH3); 1.4e

G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
929
Table 2
Furamide compounds with biological activities (5ae5i).
Compound
R2
Ki (nM) (95% confidence limits)
a
hA1
hA2A
hA2B
hA3
5a
5b
5c
5d
2-Pyridoyl
3-Pyridoyl
2-Pyridyl
4-Pyridyl
406 (356e462)
177 (141e223)
276 (227e337)
0.58 (0.47e0.71)
74.7 (62.6e89.1)
552 (358e852)
193 (168e222)
6.65 (4.69e9.43)
9110 (7800e10,700)
>10,000
841 (792e893)
2.78 (2.40e3.23)
951 (754e1200)
1870 (1700e2070)
2040 (1690e2450)
9.36 (8.90e9.85)
5e
5f
12,000 (9650e14,900)
>10,000
5950 (3390e10,400)
14,400 (9550e21,700)
179 (156e205)
>10,000
746 (516e1080)
>10,000
36,600 (24,000e56,000)
918 (803e1050)
5g
536 (451e638)
8000 (6710e9540)
5h
5i
>10,000
>10,000
>100,000
>10,000
>10,000
>10,000
8780 (4500e17,200)
3930 (2460e6280)
Data are expressed as geometric means, with 95% confidence limits in parentheses.
a
Inhibition of NECA-stimulated adenylyl cyclase activity.
vigorously for 3 h. The bright yellow precipitate was filtered off under
suction and washed with 10 ml hexane. The solid was air-dried. Yield
obtained is 56%. (LC-MS): (M þ 1) at 330 and (M þ 23) at 352, Mo-
lecular Formula e C17H19N3O2S, m.p. ¼ 109 ꢀC. Rf: 0.31 (Toluene:E-
The reaction then was slowly poured in 3% sodium bicarbonate
solution under constant swirling condition. The product was
filtered under suction, washed with water and air-dried. The
compounds were purified by column chromatography.
tOAc::8:2). 1H NMR (300 MHz, CDCl3)
d
ppm ¼ 1.19e1.25 (t, 3H, e
NCH2CH3),1.38e1.42 (t, 3H, eNCH2CH3), 3.33e3.40 (q, H, eNCH2CH3),
3.63e3.70 (q, H, eNCH2CH3), 6.53e6.55 (q, 1H, Furoyl), 7.24e7.27 (t,
1H, AreH), 7.39e7.49 (m, 6H, C6H5e, Furoyl), 9.19 (s, 1H, eNH).
5.2.6. 4-Methoxy-N-[4-phenyl-5-(pyridine-2-carbonyl)-thiazol-2-
yl]-benzamide [4a]
The titled compound was synthesised employing method C by
reacting 3c (0.0027 mol) with 2-bromo-1-(pyridin-2-yl)ethanone
(0.0027 mol) in DMF at room temperature under stirred condition
for 24 h %Yield: 58, LCMS: (M þ H)þ at 416 & (M þ 23) at 438, HRMS
calcd for C23H17N3O3S [M þ H]þ, 416.0985, found 416.0994. 1H NMR
5.2.5. Synthesis of N-[5-substituted-4-phenyl-1,3-thiazol-2-yl]
benzamides (4ael)
5.2.5.1. Method A: synthesis of 5-pyridoylanalogues. The thiourea
adducts (0.0027 mol) were reacted with respective substituted
pyridoyl bromides in equimolar ratio in acetonitrile at 70 ꢀC for 24 h
and the precipitated product was filtered under suction and re-
crystallised from ethyl acetate.
(300 MHz, CDCl3þ d6 DMSO) d ppm: 3.83 (s, 3H, eOCH3), 6.73e8.06
(m, 13H, C6H5, COeC5H4N, pOCH3eH4eCO), 12.42 (s, 1H, eNHCO).
13C NMR (75 MHz, CDCl3þ d6 DMSO)
d
ppm:56.12, 113.14,
118.10, 123.56, 125.86, 128.32, 130.46, 133.81, 134.56, 136.72,
145.62, 148.56, 150.04, 152.65, 156.34 m.p. ¼ 203e5 ꢀC. Rf: 0.66
(Toluene:Acetonitrile::8:2).
5.2.5.2. Method B: synthesis of triazines/thienopyridine analogues.
The thiourea derivatives (0.0027 mol) were dissolved in 5 ml of
methanol, to this chloromethyl compound (Schemes 2 and 3)
(0.0027 mol) dissolved in 5 ml methanol was added, the resulting
solution was stirred at 70 ꢀC temperature for 24 h. The precipitated
compound was filtered, washed with 2 ml methanol was air-dried.
The compounds were purified by column chromatography.
Alternatively the thiourea derivatives (0.0011 mol) were dis-
solved in 5 ml N,N-dimethyl formamide, to this was added chlor-
omethyl compounds (0.0011 mol) dissolved in 5 ml dimethyl
formamide and the reaction stirred for 48 h at room temperature.
5.2.7. 4-Methoxy-N-[4-phenyl-5-(pyridine-3-carbonyl)-thiazol-2-
yl]-benzamide [4b]
The titled compound was synthesised employing method C by
reacting 3c (0.0027 mol) with 2-bromo-1-(pyridin-3-yl)ethanone
(0.0027 mol) in DMF at room temperature under stirred condition
for 24 h %Yield: 60, LCMS: (M þ 1) at 416 & (M þ 23) at 438, HRMS
calcd for C23H17N3O3S [M þ H]þ, calcd 416.0985, found 416.1780. 1H
NMR (300 MHz, CDCl3þ d6 DMSO)
d ppm: 3.80 (s, 3H, eOCH3),
6.73e8.06 (m, 13H, C6H5, COeC5H4N, 4-OCH3eC6H4eCO), 12.57 (s,

Fig. 2. Panel A: Predicted binding mode of compound 5d (white sticks) in comparison with a 1,2,4-triazin-3-amine derivative (orange sticks) co-crystallized into the binding pocket of the human A2A adenosine receptor (PDB ID: 3UZA).
The view of TM7 is partially omitted. Side chains of the amino acids in contact with compound 5d are highlighted (gray sticks). Hydrogen atoms are not displayed. Panel B: Electrostatic interaction energy (kcal/mol) and hydrophobic
interaction scores (arbitrary hydrophobic units) between each amino acid located into the binding pocket of all human adenosine receptors and the selected docked pose of compound 5d. Electrostatic interaction energy values and
hydrophobic interaction scores are plotted in blue bars and yellow bars, respectively. Ballesterose-Weinstein residue numbers are reported. (For interpretation of the references to colour in this figure legend, the reader is referred to the
web version of this article.)

G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
931
Fig. 3. Panel A: Per residue dynamic electrostatic interaction energy map and per residue dynamic hydrophobic interaction score map. The individual electrostatic and hydrophobic
contributions to the interaction energy of each receptor residue with compound 5d have been calculated analysing molecular dynamics simulations trajectories. Residue numbering
and simulation time (ns) are plotted in the X and Y axes, respectively. Electrostatic energy values are expressed in kcal/mol, while hydrophobic scores are expressed in arbitrary
hydrophobic units. Panel B: The predicted binding mode of compound 5d into the binding pocket of all human adenosine receptors. The side chains of some amino acids in contact
with compound 5d are highlighted (gray sticks). Hydrogen atoms are not displayed.
1H, eNHCO), 13C NMR (75 MHz, CDCl3þ d6 DMSO)
113.00, 118.03, 123.46, 125.78, 128.32, 129.37, 130.34, 133.79, 134.28,
136.70, 145.57, 148.48, 149.97, 152.61, 156.26, 156.90, 161.37, 188.24.
m.p. ¼ 294e6 ꢀC. Rf: 0.50 (Toluene:Acetonitrile::8:2).
d
ppm: 56.05,
methanol, to this 11 (0.0027 mol) dissolved in 5 ml methanol
was added, the resulting solution was stirred at 70 ꢀC tem-
perature for 24 h %Yield: 37, LCMS: (M þ 1) at 448, HRMS calcd
for
C
22H21N7O2S [M
þ
H]þ, 448.1477, found 448.1483. 1H
NMR (300 MHz, CDCl3)
3.85 (s, 3H, eOCH3), 6.81 (s, 2H, NH2 broad), 7.07e8.15 (m,
d
ppm: 2.64, 2.96 (s, 6H, 2ꢂ CH3),
5.2.8. N-(5-(4-Amino-6-(dimethylamino)-1,3,5-triazin-2-yl)-4-
phenylthiazol-2-yl)-4-methoxybenzamide [4c]
9H, AreH), 12.69 (s, 1H, eNHCO). 13C NMR (75 MHz,
The titled compound was synthesised using method B, the
thiourea derivative 3c (0.0027 mol) was dissolved in 5 ml of
CDCl3)
d ppm: 35.52, 56.04, 125.24, 127.57, 128.41, 128.86,
129.25, 130.46, 132.29, 133.27, 135.29, 136.56, 159.24, 165.20,

932
G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
166.02, 166.59, 166.96. m.p.
(Toluene:Acetonitrile::8:2).
¼
268e70 ꢀC. Rf: 0.44
temperature under stirred condition for 48 h %Yield: 54, LCMS:
(M þ 1) at 458, m.p. ¼ 257e9 ꢀC. Rf: 0.59 (Toluene:Acetoni-
trile::8:2). HRMS calcd for C24H19N5OS2 [M þ H]þ458.1025, found
5.2.9. N-(5-(4-Amino-6-(dimethylamino)-1,3,5-triazin-2-yl)-4-
phenylthiazol-2-yl)-4-methylbenzamide [4d]
458.1030. 1H NMR (300 MHz, CDCl3)
d ppm: 1.93 (s, 3H, eCH3), 2.11
(s, 3H, eCH3), 6.63 (s, 1H, eNH2 broad), 6.75e7.46 (m, 5H, AreH),
The titled compound was synthesised using method B, the
thiourea derivative 3b (0.0027 mol) was dissolved in 5 ml of
methanol, to this 11 (0.0027 mol) dissolved in 5 ml methanol was
added, the resulting solution was stirred at 70 ꢀC temperature for
24 h %Yield: 39, LCMS: (M þ 1) at 432 & (M þ 23) at 454, HRMS
calcd for C22H21N7OS [M þ H]þ, 432.1528, found 448.1538. 1H NMR
7.56e8.45 (m, 5H, AreH), 12.55 (s, 1H, eNHCO), 13C NMR (75 MHz,
CDCl3)
d ppm: 12.96, 13.93, 112.56, 113.98, 117.56, 124.07, 125.65,
126.86, 127.92, 128.83, 130.04, 130.32, 136.58, 145.09, 146.15, 148.56,
152.45, 156.73, 158.83, 168.93.
5.2.14. N-[5-(4-Amino-5,6,7,8-tetrahydro-benzo[4,5]-thieno[2,3-d]
pyrimidin-2-yl)-4-phenyl-thiazol-2-yl]-4-methoxy-benzamide [4i]
The titled compound was synthesised employing method C by
reacting 3c (0.0027 mol) with 18 (0.0027 mol) in DMF at room
temperature under stirred condition for 48 h %Yield: 56, LCMS:
(M þ 2) at 515 & (M þ 23) at 537, m.p. ꢃ 310 ꢀC. Rf: 0.71 (Tolue-
ne:Acetonitrile::7:3). HRMS calcd for C27H23N5O2S2 [M þ H]þ
(300 MHz, CDCl3)
d ppm: 2.39 (s, 3H, eCH3), 2.64, 2.96 (s, 6H, e
N(CH3)2), 6.82 (s, 1H, eNH2 broad), 7.37e8.05 (m, 9H, Ar), 12.74 (s,
1H, eNHCO), 13C NMR (75 MHz, CDCl3)
d
ppm : 22.4, 35.96, 125.39,
127.76,128.56, 128.96, 129.46, 130.35,132.03, 133.56, 135.34, 136.76,
159.35, 165.29, 166.07, 166.61, 167.01. m.p. ¼ 258e60 ꢀC. Rf: 0.41
(Toluene:Acetonitrile::8:2).
513.1287, found 513.1293. 1H NMR (300 MHz, CDCl3)
d ppm: 12.87
5.2.10. N-[5-(4-Amino-6-dimethylamino-[1,3,5]triazin-2-yl)-4-
phenyl-thiazol-2-yl]-benzamide [4e]
(s, 1H, eNHCO), 6.87e8.16 (m, 9H, AreH), 6.87 (s, 2H, NH2 broad),
3.86 (s, 3H, eCH3), 2.88 (t, 2H, eCH2), 2.75 (t, 2H, eCH2), 1.79 (s, 4H,
d ppm: 22.22, 22.92, 25.02,
25.76, 56.05, 114.47, 118.24, 123.95, 128.92, 129.10, 130.93, 131.42,
132.26, 133.35, 134.40, 147.87, 150.00, 158.93, 159.32, 163.46, 165.40.
The titled compound was synthesised using method B, the
thiourea derivative 3a (0.0027 mol) was dissolved in 5 ml of
methanol, to this 11 (0.0027 mol) dissolved in 5 ml methanol was
added, the resulting solution was stirred at 70 ꢀC temperature for
24 h. %Yield: 39, LCMS: (M þ 1) at 418 & (M þ 23) at 440, Molecular
Formula e C21H19N7OS, m.p. ¼ 160 ꢀC. Rf: 0.38 (Toluene:Acetoni-
trile::8:2). HRMS calcd for C22H19N7OS [M þ H]þ, 418.1366, found
2ꢂ eCH2). 13C NMR (75 MHz, CDCl3)
5.2.15. N-[5-(4-Amino-5,6,7,8-tetrahydro-benzo[4,5]-thieno[2,3-d]
pyrimidin-2-yl)-4-phenyl-thiazol-2-yl]-4-methyl-benzamide [4j]
The titled compound was synthesised employing method C by
reacting 3b (0.0027 mol) with 18 (0.0027 mol) in DMF at room
temperature under stirred condition for 48 h. %Yield: 51, LCMS:
(M þ 2) at 499, m.p. ꢃ 310 ꢀC. Rf: 0.73 (Toluene:Acetonitrile::7:3).
HRMS calcd for C27H23N5O2S2 [M þ H]þ 497.1338, found 497.1344.
418.1359. 1H NMR (300 MHz, DMSO-d6)
d
ppm ¼ 2.6 and 2.93 (2s,
6H, Ne[CH3]2); 6.75 (s, 1H, eNH, 7.31e8.13 (m, 10H, eAreH, e
C6H5eCO)). 13C NMR (75 MHz, CDCl3)
ppm: 35.83, 125.86, 127.71,
d
128.27, 128.73, 129.07, 130.34, 132.28, 133.22, 136.46, 159.19, 165.16,
165.92, 166.57, 166.76.
1H NMR (300 MHz, CDCl3)
d
ppm: 1.80 (s, 4H, e2ꢂ CH2), 2.39 (s, 3H,
eCH3), 2.72 (s, 2H, eCH2), 2.91 (s, 2H, eCH2), 6.68 (s, 2H, eNH2
5.2.11. N-[5-(4-Amino-5,6-dimethyl-thieno[2,3-d]pyrimidin-2-yl)-
4-phenyl-thiazol-2-yl]-4-methoxy-benzamide [4f]
broad), 7.36e8.07 (m, 9H, AreH), 12.65 (s, 1H, eNHCO), 13C NMR
(75 MHz, CDCl3)
d ppm: 22.01, 22.97, 25.46, 25.76, 114.56, 118.65,
The titled compound was synthesised employing method C by
reacting 3c (0.0027 mol) with 15 (0.0027 mol) in DMF at room
temperature under stirred condition for 48 h. %Yield: 58, LCMS:
(M þ 1) at 488, and (M þ 18) at 510, Molecular Formula e
124.15, 129.07, 129.46, 131.06, 131.96, 132.46, 133.53, 134.52, 148.07,
150.24, 158.68, 158.85, 159.36, 163.52, 165.57.
5.2.16. N-[5-(4-Amino-5,6,7,8-tetrahydro-benzo[4,5]-thieno[2,3-d]
pyrimidin-2-yl)-4-phenyl-thiazol-2-yl]-benzamide [4k]
C
25H21N5O2S2, m.p. ¼ 283e5 ꢀC. Rf: 0.53 (Toluene:EtOAc::8:2). HRMS
calcd for C25H21N5O2S2 [M þ H]þ, 488.1131, found 488.1340. 1H NMR
The titled compound was synthesised employing method C by
reacting 3a (0.0027 mol) with 18 (0.0027 mol) in DMF at room
temperature under stirred condition for 48 h. %Yield: 53, LCMS:
(M þ 2) at 485 & (M þ 23) at 507, Molecular Formula e
(300 MHz, CDCl3) d ppm: 2.23 (s, 3H, eCH3), 2.42 (s, 3H, eCH3), 3.8 (s,
3H, eOCH3), 6.55 (s,1H, eNH2 broad), 6.73e7.89 (m, 9H, Ar),12.19 (s,
1H, eNHCO), 13C NMR (300 MHz, CDCl3)
d
ppm: 13.49, 14.25, 56.05,
112.87, 114.83, 117.15, 124.02, 125.32, 126.56, 127.78, 128.56, 130.16,
130.25, 136.31, 145.72, 147.91, 148.14, 152.26, 156.54, 158.27, 168.03.
C
26H21N5OS2, m.p. ꢃ 310 ꢀC. Rf: 0.71 (Toluene:Acetonitrile::7:3).
HRMS calcd for C26H21N5OS2 [M þ H]þ 483.1188, found 483.1180. 1H
NMR (300 MHz, CDCl3)
d
ppm: 1.78 (s, 4H, e2ꢂ CH2), 2.33 (t, 2H, e
5.2.12. N-[5-(4-Amino-5,6-dimethyl-thieno[2,3-d]pyrimidin-2-yl)-
4-phenyl-thiazol-2-yl]-4-methyl-benzamide [4g]
CH2), 2.71 (t, 2H, eCH2), 6.59 (s, 1H, eNH2 broad), 6.78e7.81 (m,
10H, AreH), 12.60 (s, 1H, eNHCO). 13C NMR (75 MHz, CDCl3)
d
ppm:
The titled compound was synthesised employing method C by
reacting 3b (0.0027 mol) with 15 (0.0027 mol) in DMF at room
temperature under stirred condition for 48 h. %Yield: 56, LCMS:
(M þ 1) at 472, Molecular Formula e C25H21N5OS2, m.p. ¼ 310 ꢀC. Rf:
0.61 (Toluene:Acetonitrile::8:2). HRMS for C25H21N5OS2 [M þ H]þ,
calcd 472.1187, found 472.1179. 1H NMR (300 MHz, CDCl3)
21.96, 23.01, 25.23, 25.56, 114.48, 118.56, 124.01, 129.04, 129.46,
131.04, 131.56, 132.46, 133.43, 134.45, 148.02, 150.15, 158.78, 158.97,
159.36, 163.50, 165.42.
5.2.17. Furan-2-carboxylic-acid [4-phenyl-5-(pyridine-2-carbonyl)-
thiazol-2-yl]-amide [5a]
d
ppm ¼ 2.42e2.52 (3s, 9H, eCH3); 7.33e7.87 (m, 9H, eAreH, pe
To a solution of 1 part of 3d in 15 parts dimethyl formamide was
added 1 part of 2-bromo-1-(pyridin-2-yl)ethanone at room tem-
perature and the solution stirred for 24 h. Reaction mixture was
poured in 50 parts of water with shaking, pure product separated as
a solid was filtered and dried. %Yield: 58, (LC-MS): (M þ 1) at 376
and (M þ 23) at 398, m.p. ¼ 172e4 ꢀC. Rf: 0.71 (Toluene:ACN::7:3).
HRMS calcd for C20H13N3O3S [M þ H]þ 375.0672, found 375.0608.
H3CeC6H4eCO); 9.61 (s,1H, eNH). 13C NMR (75 MHz, CDCl3)
d
ppm:
13.56, 14.24, 21.23, 112.98, 114.52, 117.16, 123.93, 125.56, 126.70,
127.90, 128.98, 129.97, 130.28, 136.52, 144.71, 145.93, 148.05, 152.39,
156.63, 158.24, 168.70.
5.2.13. N-[5-(4-Amino-5,6-dimethyl-thieno[2,3-d]pyrimidin-2-yl)-
4-phenyl-thiazol-2-yl]-benzamide [4h]
The titled compound was synthesised employing method C by
reacting 3a (0.0027 mol) with 15 (0.0027 mol) in DMF at room
1H NMR (300 MHz, CDCl3)
d
ppm: 6.78e7.5 (d & m 3H FuroyleH),
7.6e7.9 (5H, AreH), 8.1e8.8 (m, 5H, C5H4N), 12.79 (s, 1H, eNHCO).
13C NMR (75 MHz, CDCl3)
ppm: 111.51, 115.46, 121.27, 121.02,
d

G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
933
126.27, 127.96, 128.43, 130.17, 132.92, 133.45, 137.42, 144.18, 148.24,
149.56, 153.25, 154.52, 162.71, 164.38, 188.37.
product separated as a solid was filtered and dried. %Yield: 42, (LC-
MS): (M
þ
2) at 475, Molecular Formula e C24H17N5O2S2,
m.p. ꢃ 310 ꢀC. Rf: 0.35 (Toluene:ACN::8:2). HRMS calcd for
5.2.18. Furan-2-carboxylic acid [4-phenyl-5-(pyridine-3-carbonyl)-
thiazol-2-yl]-amide [5b]
C24H19N5O2S2 [M
þ
H]þ473.0974, found 473.0980. 1H NMR
(300 MHz, CDCl3)
d
ppm: 2.07 (m, 4H, 2ꢂ eCH2), 2.55 (t, 2H, eCH2),
To a solution of 1 part of 3d in 15 parts dimethyl formamide was
added 1 part of 2-bromo-1-(pyridin-3-yl)ethanone at room tem-
perature and the solution stirred for 24 h. Reaction mixture was
poured in 50 parts of water with shaking, pure product separated as
a solid was filtered and dried. %Yield: 52, (LC-MS): (M þ 1) at 376
2.73 (t, 2H, eCH2), 6.53 (s, 1H, eNH2 broad), 6.78e7.56 (m, 5H, Are
H), 7.87e8.45 (m, 3H, FuroyleH), 12.5 (s, 1H, eNHCO), 13C NMR
(75 MHz, CDCl3):
d ppm: 23.26, 23.91, 25.18, 111.59, 113.48, 115.47,
118.27, 127.41, 127.95, 128.73, 129.48, 133.29, 137.56, 144.26, 145.82,
148.38, 154.92, 158.73, 162.48, 162.91, 164.72.
and (M
þ
23) at 398, Molecular Formula e C20H13N3O3S,
m.p. ¼ 240e4 ꢀC. Rf: 0.44 (Toluene:ACN::8:2). HRMS calcd for
5.2.23. N-(5-(4-Amino-6-(dimethylamino)-1,3,5-triazin-2-yl)-4-
phenylthiazol-2-yl)furan-2-carboxamide [5g]
C
20H13N3O3S [M
þ
H]þ 375.0672, found 375.0680. 1H NMR
ppm: 6.78e7.5 (d & m 3H FuroyleH), 7.6e7.9
(300 MHz, CDCl3)
d
To a solution of 1 part of 3d in 15 parts methanol was added 1
part of 11 in methanol and reacted at 70 ꢀC for 24 h. The precipi-
tated product obtained was filtered off under suction and air-dried.
%Yield: 54, (LC-MS): (M þ 1) at 408 and (M þ 23) at 430
m.p. ¼ 250e2 ꢀC. Rf: 0.15 (Toluene:EtOAc::8:2). 1H NMR (300 MHz,
DMSO-d6) [ppm] ¼ 2.62 and 2.96 (2s, 6H, eN(CH3)2), 6.75e6.82
(broad s, 2H, eNH2) (m, 8H, FuroyleH, AreH), 12.82 (s, 1H, eNH),
HRMS calcd for C19H17N7O2S [M þ H]þ 408.1158, found 408.1164.
(5H, AreH), 8.1e8.8 (m, 5H, C5H4N), 12.85 (s, 1H, eNHCO), 13C NMR
(75 MHz, CDCl3)
d ppm: 111.42, 115.76, 124.42, 127.66, 128.51,
129.28, 130.37, 132.95, 133.42, 136.63, 144.17, 148.42, 151.82, 155.15,
155.27, 162.71, 164.35, 189.46.
5.2.19. Furan-2-carboxylic acid (4-phenyl-5-pyridin-2-yl-thiazol-2-
yl)-amide [5c]
To a solution of 1 part of 3d in 15 parts isopropyl alcohol was
added 1 part of 2-chloromethyl pyridine at 80 ꢀC for 24 h and the
precipitated product was filtered off under suction and dried. %
Yield: 48, (LC-MS): (M þ 1) at 348, (M þ 23) at 370 m.p. ¼ 233 ꢀC. Rf:
0.42 (Toluene:ACN::8:2). HRMS calcd for C19H13N3O2S [M þ H]þ
13C NMR (75 MHz, CDCl3)
d ppm: 40.27, 80.15, 11.92, 115.7, 117.71,
128.34, 129.18, 129.45, 133.27, 144.29, 148.47, 154.78, 161.49, 162.95,
164.58, 167.2, 170.45.
5.2.24. Furan-2-carboxylic acid [5-(5,6-dimethyl-4-oxo-3,4-dihydro-
thieno[2,3-d]pyrimidin-2-yl)-4-phenyl-thiazol-2-yl]-amide [5h]
To a solution of 1 urea derivative (F1) in 15 parts isopropyl
alcohol was added 1 part of 2-(chloromethyl)-5,6-dimethylthieno
[2,3-d]pyrimidin-4(3H)-one at 80 ꢀC for 24 h and then reaction
mixture was concentrated and to it water was added to get the
precipitate which was filtered off under suction and dried. %Yield:
38, (LC-MS): (M þ 1) at 449 and (M þ 23) at 471, Molecular For-
mula e C22H16N4O3S2, m.p. ꢃ 310 ꢀC. Rf: 0.33 (Toluene:ACN::8:2).
HRMS calcd for C22H16N4O3S2 [M þ H]þ 449.0664, found 449.0658.
347.0722, found 347.0728. 1H NMR (300 MHz, CDCl3)
d ppm: 6.89e
7.5 (d & m 3H, FuroyleH), 7.6e7.9 (5H, AreH), 8.1e8.8 (m, 5H,
C5H4N), 12.75 (s, 1H, eNHCO), 13C NMR (75 MHz, CDCl3)
d
ppm:
110.96, 114.26, 117.96, 124.14, 124.66, 127.43, 128.95, 129.42, 133.28,
137.56, 144.15, 148.37, 149.42, 151.93, 154.92, 162.91, 164.57.
5.2.20. Furan-2-carboxylic acid (4-phenyl-5-pyridin-4-yl-thiazol-
2-yl)-amide [5d]
To a solution of 1 part of 3d in 15 parts isopropyl alcohol was
added 1 part of 4-chloromethyl pyridine at 80 ꢀC for 24 h and the
precipitated product was filtered off under suction and dried. %
1H NMR (300 MHz, CDCl3)
d
ppm: 2.26 (s, 3H, eCH3), 2.43 (s, 3H, e
CH3), 6.78e7.82 (m, FuroyleH 8H, AreH), 12.17 (s, 1H, eNHCO),
12.74 (s, 1H, eNHCO), 13C NMR (75 MHz, CDCl3)
ppm: 10.27, 10.58,
Yield: 45, (LC-MS): (M
þ
1) at 348, Molecular Formula
e
d
C
19H13N3O2S, m.p. ¼ 291e3 ꢀC. Rf: 0.25 (Toluene:ACN::8:2). HRMS
111.56, 115.97, 118.74, 127.57, 129.59, 131.91, 133.15, 134.29, 144.48,
148.59, 154.63, 156.10, 156.78, 161.38, 162.72, 164.27.
calcd for C19H13N3O2S [M þ H]þ 347.0722, found 347.0723. 1H NMR
(300 MHz, CDCl3)
d ppm: 6.9e7.4 (d & m 3H, FuroyleH), 7.6e7.9
(5H, AreH), 8.2e8.8 (m, 5H, C5H4N), 12.81 (s, 1H, eNHCO). 13C NMR
(75 MHz, CDCl3) ppm: 111.56, 115.52, 117.85, 118.72, 127.73, 128.91,
5.2.25. Furan-2-carboxylic acid [5-(4-oxo-3,4-dihydro-quinazolin-
2-yl)-4-phenyl-thiazol-2-yl]-amide [5i]
d
129.48, 133.41, 143.52, 145.91, 148.47, 150.27, 155.29, 162.91, 164.48.
To a solution of urea derivative (F1) in 15 parts isopropyl alcohol
was added 1 part of 2-(chloromethyl)quinazolin-4(3H)-one at 80 ꢀC
for 24 h and the precipitated product was filtered off under suction
and dried. %Yield: 42, (LC-MS): (M þ 1) at 415 and (M þ 23) at 437,
m.p. > 310 ꢀC. Rf: 0.73 (Toluene:ACN::7:3). 1H NMR (300 MHz,
DMSO-d6) [ppm] ¼ 6.76e6.78 (q 1H, FuroyleH), 7.38e7.61 (m, 6H,
C6H5e, FuroyleH), 8.06e8.12 (d, 2H, AreH), 7.69e7.72 (d, 2H, Are
H), 7.76e7.77 (d, 2H, AreH), 7.82e7.87 (q,1H, AreH), 12.17 and 13.08
(2s, 2H, eNH). HRMS calcd for C22H14N4O3S [M þ H]þ 414.0781,
5.2.21. Furan-2-carboxylic acid [5-(4-amino-5,6-dimethyl-thieno
[2,3-d]pyrimidin-2-yl)-4-phenyl-thiazol-2-yl]-amide [5e]
To a solution of 1 part of 3d in 15 parts dimethyl formamide was
added 1 part of 15 at room temperature and the solution stirred for
48 h. Reaction mixture was added in 50 parts of water with shaking,
product separated as a solid was filtered and dried. %Yield: 38, (LC-
MS): (M þ 1) at 448, m.p. ¼ 175e8 ꢀC. Rf: 0.17 (Toluene:EtOAc::8:2).
HRMS calcd for C22H17N5O2S2 [M þ H]þ 448.0818, found 448.0824.
found 408.0787. 13C NMR (75 MHz, CDCl3)
d ppm: 111.72, 115.45,
1H NMR (300 MHz, CDCl3)
d
ppm: 2.36 (s, 3H, eCH3), 2.40 (s, 3H, e
CH3), 6.76e8.05 (m, 8H, FuroyleH, AreH), 12.99 (s, 1H, eNHCO), 13
NMR (75 MHz, CDCl3) ppm: 10.56, 13.17, 110.96, 114.37, 115.76,
120.96, 126.57, 126.88, 127.17, 127.56, 128.95, 129.46, 132.57, 133.00,
133.78, 144.18, 144.95, 148.45, 154.78, 156.27, 161.28, 162.94, 164.58.
C
d
117.86, 127.83, 128.94, 129.47, 131.49, 133.28, 136.17, 144.29, 146.71,
148.59, 154.81, 158.91, 162.47, 163.15, 164.72.
6. Biological methods
Receptor-radioligand binding studies were performed as pre-
viously described by Klotz et al. [32]. The membranes for radio-
ligand binding were prepared from CHO cells stably transfected
with human adenosine receptor subtypes in a two-step procedure.
In a first low-speed step (1000ꢂ g) cell fragments and nuclei were
removed. The crude membrane fraction was sedimented from the
supernatant at 100,000ꢂ g. The membrane pellet was re-
5.2.22. Furan-2-carboxylic acid [5-(4-amino-5,6,7,8-tetrahydro-
benzo[4,5]thieno[2,3-d]pyrim-idin-2-yl)-4-phenyl-thiazol-2-yl]-
amide [5f]
To a solution of 1 part of 3d in 15 parts dimethyl formamide was
added 1 part of 18 at room temperature and the solution stirred for
48 h. Reaction mixture was added in 50 parts of water with shaking,

934
G.S. Inamdar et al. / European Journal of Medicinal Chemistry 63 (2013) 924e934
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Acknowledgements
We thank Prof. H. Padh and Professor C. J. Shisoo, Directors, B.V.
Patel PERD centre, for their constant encouragement and support.
The molecular modelling work was supported by a grant of
the Italian Ministry for University and Research (MIUR, FIRB
RBNE03YA3L project) and by the University of Padova, Italy. S.M. is
also very grateful to Chemical Computing Group, YASARA Bio-
sciences GmbH and Accelera for the scientific and technical part-
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the grants to carry out the research work.
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Supplementary data related to this article can be found at
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