Cell division cycle 7 kinase inhibitors: 1H-pyrrolo[2,3-b]pyridines, synthesis and structure-activity relationships

Article abstract of DOI:10.1021/jm900248g

Cdc7 kinase has recently emerged as an attractive target for cancer therapy and low-molecular-weight inhibitors of Cdc7 kinase have been found to be effective in the inhibition of tumor growth in animal models. In this paper, we describe synthesis and structure-activity relationships of new 1H-pyrrolo[2, 3-b]pyridine derivatives identified as inhibitors of Cdc7 kinase. Progress from (Z)-2-phenyl-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-3,5-dihydro-4H-imidazol- 4-one (1) to [(Z)-2-(benzylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-1, 3-thiazol-4(5H)-one] (42), a potent ATP mimetic inhibitor of Cdc7 kinase with IC₅₀ value of 7 nM, is also reported.

Full text of DOI:10.1021/jm900248g

4380 J. Med. Chem. 2009, 52, 4380–4390
DOI: 10.1021/jm900248g
Cell Division Cycle 7 Kinase Inhibitors: 1H-Pyrrolo[2,3-b]pyridines, Synthesis and Structure-Activity
Relationships
Antonella Ermoli, Alberto Bargiotti, Maria Gabriella Brasca, Antonella Ciavolella, Nicoletta Colombo, Gabriele Fachin,
Antonella Isacchi, Maria Menichincheri, Antonio Molinari, Alessia Montagnoli, Antonio Pillan, Sonia Rainoldi,
Federico Riccardi Sirtori, Francesco Sola, Sandrine Thieffine, Marcellino Tibolla, Barbara Valsasina, Daniele Volpi,
Corrado Santocanale,† and Ermes Vanotti*
Nerviano Medical Sciences, Srl viale Pasteur 10, 20014 Nerviano, Milano, Italy. †Current address: National Centre for Biomedical Engineering
and Science, National University of Ireland, Galway, Ireland
Received February 27, 2009
Cdc7 kinase has recently emerged as an attractive target for cancer therapy and low-molecular-weight
inhibitors of Cdc7 kinase have been found to be effective in the inhibition of tumor growth in animal
models. In this paper, we describe synthesis and structure-activity relationships of new 1H-pyrrolo[2,
3-b]pyridine derivatives identified as inhibitors of Cdc7 kinase. Progress from (Z)-2-phenyl-5-(1H-
pyrrolo[2,3-b]pyridin-3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one (1) to [(Z)-2-(benzylamino)-5-
(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-1,3-thiazol-4(5H)-one] (42), a potent ATP mimetic inhibitor
of Cdc7 kinase with IC50 value of 7 nM, is also reported.
Introduction
Cdc7 kinase by siRNA blocks DNA synthesis, leading to a
p53 independent cell death in several cancer cell lines.7
Furthermore, Cdc7 kinase inhibition abolishes the phos-
phorylation of a relevant cellular substrate, Mcm2 protein, at
specific phosphorylation sites.8,9 Inhibition of Cdc7 kinase by
small interfering RNAs6 blocks DNA synthesis in human cell
lines.7 As a consequence, tumor cells are funneled into the
apoptotic pathway in a p53 independent manner; whereas,
normal cells are arrested in their progression through the cell
cycle and are capable of surviving Cdc7 kinase inhibition for
long periods of time.7 These findings support the notion that
the pharmacological inhibition of Cdc7 kinase can be an
effective novel strategy for the development of oncologic
therapeutics as exemplified by a few small-molecule inhibitors
of Cdc7 kinase shown to be effective in animal models.
We have recently published the discovery of pyrrolopyr-
idinones as the first class of potent Cdc7 kinase inhibitors.10
These compounds supported the principle that pharmacolo-
gical inhibition of Cdc7 kinase delays tumor growth in pre-
clinical cancer models.11,12 Although there is currently a small
number of known Cdc7 kinase inhibitors,13-16 their number
will likely increase in the near future.
In addition to pyrrolopyridinones, we explored other che-
mical classes employing molecular modeling and medicinal
chemistry techniques with the aim to obtain molecules having
biological activity, selectivity profile, and pharmaceutical
properties suitable for development. We herein report on a
new class of novel azaindolylidene-imidazolones and azain-
dolylidene-thiazolones.17 The screening of a number of Cdk
family inhibitors, available in-house, led to the discovery of
(Z)-2-phenyl-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-3,5-
dihydro-4H-imidazol-4-one (1 Figure 1), as a potent ATP
competitive inhibitor of Cdc7 kinase with an IC50 of 30 nM
in a Cdc7 kinase assay (using a complex Cdc7FL/Dbf4FL)3
and greater than 10-fold selectivity versus Cdk2/A kinase.
DNA replication is a fundamental process for cell prolif-
eration. Mechanisms that control entry in the S-phase and
proper execution of DNA synthesis are often altered in
malignant cells and at the same time are attractive targets
forthedevelopment of antitumor agents. DNAreplicationisa
two-step process: first, during the initiation reaction, proteins
bound to origin DNA are activated by phosphorylation in
order to assemble replication forks, and second, during
elongation, DNA polymerases with accessory factors synthe-
size new DNA strands. Cdc7a kinase, a key cell cycle regu-
lator, is an evolutionary conserved serine-threonine kinase
that plays a pivotal role in linking cell cycle regulation to
genome duplication. In the S-phase, Cdc7 kinase promotes
initiation of DNA replication by phosphorylating proteins
previously recruited at the origin sequences during the G1-
phase. Cdc7-dependent phosphorylation is therefore essential
for converting a dormant prereplicative complex into two
active replication forks.1
The Cdc7 kinase, in the same way as cyclin-dependent
kinases, is activated by the binding of alternative regulatory
subunits, Dbf4 and Drf1.2,3 Cdc7, Dbf4, and Drf1 mRNA are
overexpressed in several tumor cell lines.2-5
Cdc7 kinase is therefore a good inhibitory target for the
development of anticancer drugs. Cdc7 kinase function is in
fact essential for DNA replication and cell proliferation of
human cells: microinjection of specific anti-Cdc7 antibodies
prevents DNA replication,6 and genetic down-regulation of
*To whom correspondence should be addressed. Phone: þ39-0331-
581521. Fax: þ39-0331-581347. E-mail: ermes.vanotti@nervianoms.
com.
a Cdc7, cell division cycle 7 kinase; Cdk, cyclin-dependent kinase;
GSK, glycogen synthase kinase; PKA, cAMP-dependent kinase;
VEGFR, vascular endothelial growth factor receptor; CK, casein
kinase.
r
pubs.acs.org/jmc
Published on Web 06/25/2009
2009 American Chemical Society

Article
SAR studies, designed to identify modifications and/or
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14 4381
medium. The benzylsulfanyl group of compound 41 can be
also replaced by amines. For instance, derivative 17 was
obtained upon heating with (S)-(-)-1-phenylethylamine.
3. The synthesis of derivatives carrying nitrogen at posi-
tion 5 is presented in Scheme 3. Stereoisomers 36 and 37 are
obtained by chromatographic separation of the (E,Z) mix-
ture 35 (Scheme 3), in turn obtained from 3-formyl-5-nitro-
7-azaindole via the standard protocol previously shown.
Formylation of 5-nitro-7-azaindole to 3-formyl-5-nitro-7-
azaindole is obtained with the Duff reaction by refluxing
with hexamethylenetetramine in acetic acid. Reduction of
the nitro group of derivative 35 by catalytic hydrogenation,
followed by chromatographic separation of the (E,Z) mix-
ture 38, yields 5-amino-7-azaindole 39. Access to acetamide
40 is obtained from 5-acetylamino-7-azaindole through the
sequence of reactions already used for compound 35.
substituents that might increase the potency against Cdc7
kinase, were carried out on a series of analogues of 1, which
were predominantly modified at position 2. Their synthesis
and biological activity are herein reported. The inhibitory
activity of putative Cdc7 kinase inhibitors was determined
by a 33P-γ-ATP transphosphorylation assay previously de-
scribed.10 Selectivity toward other protein kinases was eval-
uated against a panel of about 35 Tyr and Ser-Thr kinases.18
The Cdk2 and GSK3β kinases, consistent with their similarity
intheir ATP binding pockets,19,20 exhibited greater inhibition,
while PKAR, VEGFR3, and CK2 kinases were generally
inhibited to a lesser extent.
Some of these compounds demonstrate some inhibitory
effect also against Cdk9 (Table 3), a kinase involved
in transcriptional regulation.21,22 The combined inhibition
of cell cycle progression and transcription could potentially
increase the cytotoxic effect of the compound against tumoral
cells as has been previously demonstrated for Cdks inhibi-
tors.23
Results and Discussion
First, we undertook the screening of our internal collection
of Cdk inhibitors, a choice driven by the close sequence
similarity of the two kinases and by well-established in-house
protocols for screening Cdk inhibitors. This strategy led to the
prompt discovery of (Z)-2-phenyl-5-(1H-pyrrolo[2,3-b]pyri-
din-3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one (1), a po-
tent Cdc7 kinase inhibitor and a promising starting scaffold for
SAR. As a result, a synthetic chemistry program was initiated.
Two main sets of imidazolones with different substitutions
at position 2 were prepared: one with a cyclic moiety directly
linked to imidazolone and another with substituents tethered
through an amino group. Most of the SAR evaluations were
done on the latter derivatives based on their synthetic flex-
ibility and potential for structural elaboration. The two sets
were first evaluated by molecular modeling. A homology
model of Cdc7 kinase10 was utilized for exploring the possible
binding mode in the ATP active site of 1 (taken as reference of
the first set) and 10, as representative of the second set. Under
this model, the nitrogen atoms of the 7-azaindole ring in
compound 1 are bound with two hydrogen bonds to the hinge
region of the Cdc7 kinase. The carbonyl of imidazol-4-one
forms a hydrogen bond with the conserved lysine residue,
while the NH of the same ring is connected with the conserved
aspartate via electrostatic interaction (Figure 2). The docking
in the Cdc7 kinase model of compound 10 is less straightfor-
ward, owing to different binding mode possibilities for the
benzylaminogroup. Thebest hypothesisproposesthatthere is
a difference in the interaction of the phenyl group of com-
pound 10 with the highly flexible glycine loop (Figure 3) in
contrast to compound 1.
Chemistry. The preparation of the reported compounds is
based on the described protocols and the largely predomi-
nant (>85% by NMR) stereochemistry of the exocyclic
double bond is (Z), unless otherwise stated.
1. The condensation between 7-azaindole-3-carboxalde-
hyde and hyppuric acid derivatives A provides azlactones B24
that are transformed into the imidazolones 1, 3-5 upon
treatment with aqueous ammonia and sodium carbonate in
refluxing methanol (Scheme 1).25
2. The condensation between 7-azaindole-3-carboxalde-
hyde and thiohydantoin or rhodanine, obtained by refluxing
in acetic acid and sodium acetate, yields imidazolidinone C
and thiazolidinone D, respectively (Scheme 2). Alternatively,
imidazolidinone C1 was obtained from the condensation
between thiohydantoin and 3-acetyl-7-azaindole in the pre-
sence of boron trifluoride etherate at room temperature.
Intermediates C, C1, and D are in turn transformed into
the corresponding methylsulfanyl derivatives E, E1, and F by
alkylation with methyl iodide in basic medium, and these are
subsequently converted into compounds 6-34 and 42-45,
respectively, by nucleophilic substitution of the methylsulfa-
nyl group with amines.26
Alternatively, 2-thioxo imidazolidinone C produces imi-
dazolone 41 by alkylation with benzyl bromide in basic
The SAR analyses examine the 7-azaindole ring, the exo-
cyclic double bond, the central five-membered ring and the
substituents linked to it. First, we investigated if the 7-
azaindole ring could be conveniently replaced by the indole
Figure 1. Structure of azaindole 1.
Scheme 1. Synthesis of Arylimidazolonesa
a Conditions: (a) Ac2O, NaOAc, 100 °C, 2 h; (b) 30% aq NH3, Na2CO3, MeOH, reflux, 8 h.

4382 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14
Ermoli et al.
Scheme 2. Synthesis of Aminoimidazolones, Sulfanylimidazolones, and Aminothiazolonesa
a Conditions: (a) thiohydantoin, NaOAc, AcOH, reflux, 5 h; (b) rhodanine, NaOAc, AcOH, reflux, 5 h; (c) thiohydantoin, BF3 Et2O, THF, TEA, rt,
3
5 days; (d) aq NaOH, MeOH, MeI, rt, 4 h; (e) R’NH2 or R’R00NH, EtOH, reflux, 24 h or (f) when R = methyl, R’NH2, EtOH, 110 °C (sealed tube), 18 h;
(g) benzyl bromide, NaOH, MeOH, rt, 18 h; (h) (S)-(-)-1-phenylethylamine, EtOH, sealed tube, 110 °C, 24 h.
Scheme 3. Synthesis of 5-Aminoazaindole derivativesa
a Conditions: (a) hexamethylenetetramine, AcOH, H2O, reflux, 3 h; (b) thiohydantoin, NaOAc, AcOH, reflux, 5 h; (c) aq NaOH, MeOH, MeI, rt, 4 h;
(d) benzylamine, EtOH, reflux, 24 h; (e) chromatography; (f) 5% Pd-C/H2, 40 psi, EtOAc, rt, 24 h; (g) AcOH, TBTU, HOBT, DIEA, DMF, rt, 18 h.
nucleus and whether additional functions on the 7-azaindole
ring system would provide an increase of potency (region A,
Table 1). As shown in the table, indole cannot replace 7-
azaindole without complete loss of activity; therefore, the aza-
nitrogen is a critical feature and participates in the binding in
the hinge region. Simple substituents on the 7-azaindole ring,
for example, 50-nitro, 50-amino, and 50-acetamido, decrease
activity.
The double bond, the key junction between the two ring
systems, was then considered (region B, Table 2). Its role on

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14 4383
Table 1. SAR: Structural Modifications at Part A (IC50, μM)a
compd
A
Cdc7
compd
X
Cdc7
1
2
N
CH
0.050 ( 0.036
>10
10
36
39
40
H
NO2
0.020 ( 0.008
0.130 ( 0.098
0.238 ( 0.007
0.116 ( 0.017
NH2
NHAc
Figure 2. Possible binding mode of azaindole 1 in the homology
model of Cdc7 kinase.
a IC50 values are reported as the mean ( standard deviation (n g 2).
comparable activity in the bioassay but different cellular
activity, as the compounds with aromatic R groups show
on the A2780 cell line IC50 values around 1 μM compared to
8 μM of the other subset.
In Table 5, substituted secondary amines are considered.
They are somewhat more active than the previous com-
pounds, with IC50 values often below 50 nM.
Substitutions at the phenyl ring are detrimental, especially
at the para position and less so at the meta (12 and 11, 14 and
13, 16 and 15). These data are in agreement with the binding
mode hypothesis, where an interaction between the phenyl
ring and the glycine loop is proposed. Cycloalkanes and
alkanes are well accepted as long as they are not too bulky
(24, 27, 33). Heterocyclic rings can be substituted for
the phenyl (18, 19, 25). The flexible phenethyl chain is
comparable in activity to benzyl (20 vs 10). Notwithstanding
the remarkable activity expressed in the bioassay, the cellular
activity of imidazolones on the A2780 cell line is only med-
iocre. Of these molecules, more than half are active on Cdc7
kinase with IC50<50 nM but their cellular activity is seldom
below the low micromolar range. These relatively high IC50
values in the cell-based assays can be explained by the high
affinity that Cdc7 kinase has for ATP (Km of 0.7 μM) and the
high levels of intracellular ATP.28 The high efflux ratios (BA/
AB) measured for these compounds in the Caco-2 cells test
affirm this result.
Figure 3. Proposed binding mode of azaindole 10 in the homology
model of Cdc7 kinase (the glycine loop is in white).
activityis important: absence of substituents (see10 compared
to 34) and proper stereochemistry (36 vs 37) are requisite for
activity.
The presence of a substituent Y, disrupting the planarity of
the system, seems to prevent efficacious binding, while only
the (Z) stereochemistry ensures the correct orientation of the
carbonyl and the amidic amino group toward lysine and
aspartate residues, respectively. Considering the central five-
membered ring (region C, Table 3), we found that the
influence of atom W, connecting the central heterocycle to
the side arm, on activity is small but significant versus Cdc7
kinase but huge versus Cdk9 (see 10 vs 41).
Nitrogen is moderately preferred to sulfur although sulfur
confers remarkable selectivity versus Cdk9 kinase.27 More
difficult to interpret is the role of atom X on the enzyme
inhibition and to understand how the loss of contribution of
the electrostatic interaction between the amidic NH and
aspartate can be more than compensated by sulfur (com-
pound 42 vs 10, Table 3). One explanation might be the
formation of a particularly good lipophilic interaction of the
sulfur atom with a leucine present in the Cdc7 kinase model.
More importantly, sulfur imparts a substantial improvement
to cellular activity even if at expense of selectivity. In fact,
compound 42 shows an IC50 value of 0.32 μM on the A2780
cell line, 4 times greater than analogues 10 and 41, but in
contrast to them, inhibits 2 out of 38 kinases (Cdk2/A and
PKAR) at IC50<50 nM.
In conclusion, the value of this class is impaired by its
generally low cellular activity. Only when imidazolone was
replaced with the thiazolone ring, cellular activity showed
such remarkable improvement as to make 42 a good lead
worthy of optimization.
For this reason, a few more thiazolones were prepared and
compared with their homologous imidazolones (Table 6).
The most remarkable outcome from this comparison is the
invariably higher cellular activity of thiazolones regardless of
the substantial equi-activity on the enzyme. Of the most
representative compounds (10, 17, 42 and 45), analogues
10, 17, 45 show medium/high apparent permeability from
PAMPA29,30 test data and at Caco-2 test only 42 and 45
display low efflux ratios (BA/AB). Overall, compound 45 is
unique in having a high PAMPA apparent permeability, low
efflux ratio, and high permeability as measured at Caco-2.31
This might account for the far superior cellular activity of
45 on the A2780 cell line.
After establishing the efficacy of the 7-azaindole nucleus,
the need of (Z) stereochemistry of the double bond, and the
substantially equivalent activity of nitrogen and sulfur on the
enzyme in the central part of the molecule, the influence of
substituents at position 2 of the imidazolone ring was then
evaluated. In Table 4, data relative to derivatives carrying
a cyclic moiety R are reported, where R is represented
by aromatic rings and cyclic amines. These subsets show
Conclusions
In this paper we present a series of 7-azaindole derivatives,
inhibitors of Cdc7 kinase.

4384 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14
Table 2. SAR: Structural Modifications at Part B (IC50, μM)a
Ermoli et al.
compd
Y
Cdc7
compd
stereochemistry of double bond
Cdc7
10
34
H
CH3
0.020 ( 0.008
>10
36
37
Z
E
0.130 ( 0.098
>10
a IC50 values are reported as the mean ( standard deviation (n g 2).
Table 3. SAR: Structural Modifications at Part C (IC50, μM)a
Table 4. SAR: Variations of Substituent R in Imidazolones (IC50, μM)a
compd
X
W
U
Cdc7
Cdk9/T
10
41
42
N
N
S
NH
S
NH
NH
N
0.020 ( 0.008
0.049 ( 0.005
0.009 ( 0.003
0.095 ( 0.013
6.1 ( 3.9
0.015 ( 0.006
NH
a IC50 values are reported as the mean ( standard deviation (n g 2).
Starting from precursor 1, the SARs associated with the
molecule were explored. Several novel azaindolylidene-imida-
zolones were prepared that show excellent enzyme inhibition,
good selectivity, but inadequate cellular activity. When the
imidazolone moiety was replaced with the thiazolone group,
a significative increase of cellular activity was observed and
a good lead, (Z)-2-(benzylamino)-5-(1H-pyrrolo[2,3-b]pyri-
din-3-ylmethylene)-1,3-thiazol-4(5H)-one (42), was obtained.
Starting from 42, further work is being produced with the goal
to design analogues having optimized overall features for the
purpose of cancer drug development.
a IC50 values are reported as the mean ( standard deviation (n g 2).
acquired in full scan mode from 100 to 800 m/z. Masses are
given as m/z ratio. When necessary, compounds have been
purified by preparative HPLC on a Waters Symmetry C18
(19 mm ꢀ 50 mm, 5 μm) column using a Waters preparative HPLC
600 equipped with a 996 Waters PDA detector and a Micromass
model ZMD single quadrupole mass spectrometer, electrospray
ionization, positive mode. Mobile phase A was water 0.01%
trifluoroacetic acid, and mobile phase B was acetonitrile. Gra-
dient from 10 to 90% B in 8 min, hold 90% B 2 min. Flow rate
20 mL/min. Column chromatography was conducted either under
medium pressure on silica (Merck silica gel 40-63 μm) or on
prepacked silica gel cartridges (Biotage) or on a Horizon system.
1H NMR spectra were routinely recorded at a constant tempera-
ture of 28 °C on a Varian INOVA 400 spectrometer operating at
400.45 MHz and equipped with a 5 mm indirect detection PFG
Probe (1H{15N-31P}). Where reported, a Varian INOVA 500
spectrometer, operating at 499.7 MHz and equipped with a 5 mm
triple resonance indirect detection PFG probe cold probe (1H-
{1C, 15N}) was used. Chemical shifts were referenced with respect
to theresidual solvent signals (DMSO-d6: 2.50ppmfor1H). Data
are reported as follows: chemical shift, multiplicity (s = singlet,
d=doublet, t=triplet, q= quartet, br s=broad singlet, td=triplet
of doublet, ddd= doublet of doublet of doublet, m=multiplet),
coupling constants (Hz), and number of protons. Low-resolu-
tion mass spectral (MS) data were determined on a Finnigan
MAT LCQ ion trap instrument, equipped with ESI. ESI(þ)
high-resolution mass spectra (HRMS) were obtained on a
Waters Q-Tof Ultima directly connected with micro HPLC
1100 Agilent as previously described.32
Experimental Section
1. Chemistry. Unless otherwise noted, solvents and reagents
were obtained from commercial suppliers and used without
further purification. All reactions involving air- or moisture-
sensitive reagents were performed under an argon atmosphere.
Unless otherwise specified, all final compounds were purified to
g95% purity, as determined by high-performance liquid chro-
matography (HPLC), using a Waters 2790 HPLC system com-
bined with a 996 Waters PDA detector and Micromass model
ZQ single quadrupole mass spectrometer, equipped with an
electrospray ion source (ESI). HPLC-UV/MS analysis were
carried out at room temperature and a flow rate of 1 mL/min,
using an RP C18 Waters XTerra column (4.6 mm ꢀ 50 mm;
3.5 μm). Mobile phase A was ammonium acetate 5 mM buffer
(pH 5.5 with acetic acid):acetonitrile 95:5, and mobile phase B
was ammonium acetate 5 mM buffer (pH 5.5 with acetic acid):
acetonitrile 5:95; the gradient wasfrom10 to 90%B in 8 min then
hold 90% B for 2 min before re-equilibration. The injection
volume was 10 μL. UV Detection was performed between 215
and 400 nm. The mass spectrometer was operated in positive and
in negative ion mode, capillary voltage was set up at 2.5 KV;
source temperature 120 °C; cone 10 V. Mass spectra were

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14 4385
Table 5. SAR: Variations of Substituent R0 in Imidazolones (IC50, μM)a
a IC50 values are reported as the mean ( standard deviation (n g 2).
Thin-layer chromatography was performed on Merck silica
dissolved in dichloromethane, the organic solution was washed
with water, dried over anhydrous sodium sulfate, and concen-
trated under reduced pressure to yield 4-[(1-acetyl-1H-pyrrolo-
[2,3-b]pyridin-3-yl)methylene]-2-phenyl-1,3-oxazol-5(4H)-one as
a yellow-orange solid (0.510 g, 45% yield). This intermediate
was suspended in 30% aqueous ammonia (40 mL), and solid
sodium carbonate (0.220 g, 2.1 mmol) and methanol (40 mL)
were added and the mixture was refluxed for 8 h. Half of the
solvent was removed by distillation, and the precipitate was
filtered and washed with water. The title compound, as the free
base, was obtained as a yellow solid (0.290 g, 68%). 1H NMR
(DMSO-d6), δ ppm 7.31 (dd, J=7.9, 4.7 Hz, 1 H) 7.37 (s, 1 H)
7.56-7.64 (m, 3 H) 8.18 (s, 2 H) 8.36 (dd, J=4.7, 1.6 Hz, 1 H)
8.54 (d, J=1.9 Hz, 1 H) 9.04 (d, J=7.8 Hz, 1 H) 11.92 (bs, 1 H)
12.59 (bs, 1 H) 12.79 (bs, 1 H). The compound was suspended in
gel 60 plates coated with 250 μM layer with fluorescent indica-
tor. Components were visualized by UV light (λ=254 and
366 nm) and iodine vapors. In (Z) compounds, the stereochem-
istry of the exocyclic double bond is predominantly (>85%) or
exclusively (Z).
Compound 2 (1,5-dihydro-5-(1H-indol-3-ylmethylene)-2-
phenyl-4H-imidazol-4-one) is commercially available.
(Z)-2-Phenyl-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-3,5-
dihydro-4H-imidazol-4-one (1). A mixture of 7-azaindole-3-car-
boxaldehyde (0.380 g, 2.6 mmol), hyppuric acid (0.470 g, 2.6 mmol),
and sodium acetate trihydrate (0.360 g, 2.6 mmol) in acetic
anhydride (2.5 mL) was heated at 100 °C under stirring for
2 h. After cooling to room temperature, the precipitate was
filtered and washed with 95% ethanol. The solid was then

4386 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14
Table 6. SAR: Imidazolones vs Thiazolones (IC50, μM)a
Ermoli et al.
hydro-4H-imidazol-4-one E as a yellow solid (8.15 g, 31.6 mmol,
96%). 1H NMR (DMSO-d6), δ ppm 2.71 (s, 3 H) 7.09 (s, 1 H) 7.21
(dd, J=7.9, 4.6 Hz, 1 H) 8.31 (dd, J=4.6, 1.6 Hz, 1 H) 8.38 (d, J=
3.0 Hz, 1 H) 8.84 (d, J=7.5 Hz, 1 H) 11.60 (s, 1 H) 12.36 (bs, 1 H).
To assign the configuration of the exocyclic double bond, we
run on E the NMR experiment gselJXH by exciting with shaped
pulse the 13C signal of the carbonyl function and observing the
relative 1H spectrum.33
This shows the antiphase doublet of the methylidene protons
that exhibit a cis long-range constant (4.5 Hz), enabling us to
assign the Z configuration.34
To a suspension of E (0.200 g, 0.77 mmol) in absolute ethanol
(5 mL), piperidine (0.96 mL, 9.7 mmol) was added and the
mixture was refluxed overnight. After cooling to room tempera-
ture, the precipitate was filtered and suspended in methanol
(2 mL). To the suspension, 4 M hydrochloric acid in dioxane
(0.5 mL) was added and the mixture was stirred at room
temperature for 30 min. The yellow precipitate was purified by
flash chromatography, eluting with dichloromethane/methanol
10:1. The product was suspended in methanol (2 mL), 4 M
hydrochloric acid in dioxane (0.5 mL) was added, and the
mixture was stirred at room temperature for 30 min. The
precipitate was filtered and washed with methanol and diethyl
ether. The title compound was obtained as a yellow solid (0.160
g, 0.54 mmol, 70%). 1H NMR (DMSO-d6), δ ppm 1.70 (s, 6 H)
3.73 (bs, 4 H) 7.16 (s, 1 H) 7.25 (dd, J=7.9, 4.7 Hz, 1 H) 8.36 (dd,
J=4.7, 1.6 Hz, 1 H) 8.38-8.41 (m, 2 H) 12.60 (bs, 1 H). HRMS
(M þ H)þ calcd 296.1506, found 296.1497.
a IC50 values are reported as the mean ( standard deviation (n g 2).
methanol, excess 4 M hydrochloric acid in dioxane was added,
and the mixture was stirred at room temperature for 30 min. The
precipitate was filtered and washed with a little methanol and
then with diethyl ether to yield the hydrochloride. HRMS (M þ
H)þ calcd 289.1084, found 289.1084.
By employing the above-described procedure the following
compounds were also prepared:
(Z)-2-Pyridin-3-yl-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
lene)-3,5-dihydro-4H-imidazol-4-one (3). 1H NMR (DMSO-d6),
δ ppm 7.34 (dd, J=7.9, 4.7 Hz, 1 H) 7.48 (s, 1 H) 7.74-7.83 (m,
1 H) 8.38 (dd, J=4.7, 1.6 Hz, 1 H) 8.62 (s, 1 H) 8.66 (d, J = 8.0
Hz, 1 H) 8.85 (d, J = 5.1 Hz, 1 H) 9.05 (d, J = 8.2 Hz, 1 H) 9.39
(d, J=1.3 Hz, 1 H) 12.12 (bs, 1 H) 12.70 (bs, 1 H). HRMS (M þ
H)þ calcd 290.1036, found 290.1041.
(Z)-2-(4-Methylphenyl)-5-(1H-pyrrolo[2,3-b]pyridin-3-yl-
methylene)-3,5-dihydro-4H-imidazol-4-one (4). 1H NMR (DMSO-
d6), δ ppm 2.43 (s, 3 H) 7.32 (m, 1H) 7.35 (s, 1 H) 7.42 (d, J=7.9 Hz,
2 H) 8.08 (m, 2 H) 8.37 (m, 1 H) 8.55 (d, J=1.4 Hz, 1 H) 9.03 (d,
J=8.0 Hz, 1 H) 11.87 (bs, 1 H) 12.58 (bs, 1 H). HRMS (M þ H)þ
calcd 303.1241, found 303.1229. Percent of purity 92%.
(Z)-2-(3-Methylphenyl)-5-(1H-pyrrolo[2,3-b]pyridin-3-yl-
methylene)-3,5-dihydro-4H-imidazol-4-one (5). 1H NMR (DMSO-
d6), δ ppm 2.45 (s, 3 H) 7.30-7.35 (m, 1 H) 7.38 (s, 1 H) 7.43 (m,
1 H) 7.50 (m, 1 H) 7.98 (d, J=7.8 Hz, 1 H) 8.02 (s, 1 H) 8.37 (d,
J=4.6 Hz, 1 H) 8.57 (d, J=1.7 Hz, 1 H) 9.03 (d, J=7.6 Hz, 1 H)
11.89 (bs, 1 H) 12.59 (bs, 1 H). HRMS (M þ H)þ calcd 303.1241,
found 303.1239.
By employing the above-described procedure the following
compounds were also prepared:
(Z)-2-Morpholin-4-yl-5-[1-(1H-pyrrolo[2,3-b]pyridin-3-yl)-
methylidene]-3,5-dihydro-imidazol-4-one Dihydrochloride (7). 1H
NMR (DMSO-d6), δ ppm 3.71-3.81 (m, 8 H) 7.10 (bs, 1 H) 7.25
(dd, J=7.6, 4.7 Hz, 1 H) 8.35 (d, J=4.7 Hz, 1 H) 8.39 (d, J=1.3
Hz, 1 H) 8.46 (d, J=7.6 Hz, 1 H) 12.53 (bs, 1 H). HRMS (M þ
H)þ calcd 298.1299, found 298.1299. Percent of purity 93%.
(Z)-2-(4-Methyl-piperidin-1-yl)-5-[1-(1H-pyrrolo[2,3-b]pyri-
din-3-yl)-methylidene]-3,5-dihydro-imidazol-4-one Dihydrochlor-
ide (8). 1H NMR (DMSO-d6), δ ppm 0.97 (d, J=6.3 Hz, 3 H)
1.23-1.39 (m, 2 H) 1.71-1.77 (m, 1 H) 1.77-1.83 (m, 2 H)
3.23-3.34 (m, 2 H) 4.19 (bs, 2 H) 7.16 (s, 1 H) 7.25 (dd, J=7.9,
4.7 Hz, 1 H) 8.36 (dd, J=4.7, 1.4 Hz, 1 H) 8.38-8.42 (m, 1 H)
8.41 (bs, 1 H) 12.46-12.81 (m, 1 H) 12.61 (bs, 1 H). HRMS (M þ
H)þ calcd 310.1662, found 310.1654. Percent of purity 91%.
(Z)-2-(2-Methyl-morpholin-4-yl)-5-[1-(1H-pyrrolo[2,3-b]pyri-
din-3-yl)-methylidene]-3,5-dihydro-imidazol-4-one Dihydrochlor-
ide (9). 1H NMR (DMSO-d6), δ ppm 1.18 (d, J = 6.2 Hz,
3 H) 2.89 - 3.11 (m, 2 H) 3.99 (dd, J=11.7, 3.0 Hz, 3 H) 4.14
(bs, 2 H) 7.13 (bs, 1 H) 7.25 (dd, J = 7.9, 4.7 Hz, 1 H) 8.35 (dd,
J = 4.7, 1.5 Hz, 1 H) 8.41 - 8.49 (m, 2 H) 12.57 (bs, 1 H).
HRMS (M þ H)þ calcd 312.1455, found 312.1457. Percent of
purity 92%.
(Z)-2-(Benzylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
lene)-3,5-dihydro-4H-imidazol-4-one Hydrochloride (10). To a
suspension of 2-(methylthio)-5-(1H-pyrrolo[2,3-b]pyridin-3-yl-
methylene)-3,5-dihydro-4H-imidazol-4-one (0.200 g, 0.77
mmol) in absolute ethanol (5 mL) benzylamine (1.1 mL, 9.7
mmol) was added and the mixture was refluxed for 24 h. After
cooling to room temperature, the precipitate was filtered and
purified by flash chromatography, eluting with dichloro-
methane/methanol 10:1. The product was suspended in metha-
nol (2 mL), 4 M hydrochloric acid in dioxane (0.5 mL) was
added, and the mixture was stirred at room temperature for 30
min. The title compound was obtained as a yellow solid (0.230 g,
0.66 mmol, 86%). 1H NMR (DMSO-d6), δ ppm 4.73 (bs, 2 H)
7.19 (bs, 1 H) 7.21-7.26 (m, 1 H) 7.32-7.46 (m, 5 H) 8.31-8.44
(m, 3 H) 9.62 (bs, 1 H) 12.62 (bs, 1 H). HRMS (M þ H)þ calcd
318.1349, found 318.1350.
(Z)-2-Piperidin-1-yl-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
lene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (6).
A
mixture of 7-azaindole-3-carboxaldehyde (5.98 g, 41 mmol),
thiohydantoin (4.75 g, 41 mmol), and sodium acetate (11.30 g,
138 mmol) in glacial acetic acid (60 mL) was refluxed under
stirring for 5 h. After cooling in ice bath, the precipitate
was filtered and washed with 95% ethanol. After drying, (Z)-
5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-2-thioxoimidazoli-
din-4-one C was obtained as a yellow solid (8.90 g, 36.5 mmol,
88%). 1H NMR (DMSO-d6), δ ppm 6.83 (s, 1 H) 7.21 (dd, J=
7.8, 4.6 Hz, 1 H) 8.31 (dd, J=6.7, 1.2 Hz, 1 H) 8.33 (dd, J=4.7,
1.4 Hz, 1 H) 8.57 (d, J=2.6 Hz, 1 H) 11.87 (s, 1 H) 12.21 (s, 1 H)
12.47 (s, 1 H). To a solution of C (8.00 g, 32.8 mmol) in 12.6%
aqueous NaOH (12 mL) and methanol (80 mL), methyl iodide
(2.25 mL, 36 mmol) was added and the reaction mixture was
stirred at room temperature for 4 h. Most of the solvent was
removed by distillation, and the precipitate was filtered and
washed first with water (50 mL) and then with diethyl ether
(50 mL). The washings were concentrated and extracted with
dichloromethane, dried over anhydrous sodium sulfate, and
joined to the first solid crop. The whole crop was suspended
in methanol, stirred for 30 min, filtered, and dried to yield (Z)-2-
(methylthio)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-3,5-di-
By employing the above-described procedure the following
compounds were also prepared:

Article
(Z)-2-[(3-Methylbenzyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-
3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride
(11). 1H NMR (DMSO-d6), δ ppm 2.35 (s, 3 H) 4.68 (bs, 2 H)
7.16-7.20 (m, 2 H) 7.21-7.27 (m, 3 H) 7.29-7.35 (m, 1 H)
8.32-8.45 (m, 3 H) 9.62 (bs, 1 H) 12.64 (bs, 1 H). HRMS (M þ
H)þ calcd 332.1506, found 332.1505.
(Z)-2-[(4-Methylbenzyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-
3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride
(12). 1H NMR (DMSO-d6), δ ppm 2.33 (s, 3 H) 4.67 (bs, 2 H)
7.19 (bs, 1 H) 7.24 (m, 3 H) 7.34 (d, J=7.5 Hz, 2 H) 8.31-8.46
(m, 4 H) 9.59 (bs, 1 H) 12.63 (bs, 1 H). HRMS (M þ H)þ calcd
332.1506, found 332.1500.
(Z)-2-[(3-Chlorobenzyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-3-
ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (13).
1H NMR (DMSO-d6), δ ppm 4.74 (bs, 2 H) 7.18 (bs, 1 H) 7.24
(dd, J=7.9, 5.0 Hz, 1 H) 7.39-7.48 (m, 4 H) 7.57 (s, 1 H) 8.34-
8.45 (m, 3 H) 9.64 (bs, 1 H) 12.63 (bs, 1 H). HRMS (M þ H)þ
calcd 352.0960, found 352.0970. Percent of purity 92%.
(Z)-2-[(4-Chlorobenzyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-3-
ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (14).
1H NMR (DMSO-d6), δ ppm 4.73 (m, 2 H) 7.18 (bs, 1 H) 7.24
(dd, J=7.8, 4.0 Hz, 1 H) 7.45-7.54 (m, 4 H) 8.33-8.44 (m, 3 H)
9.62 (bs, 1 H) 12.63 (bs, 1 H). HRMS (M þ H)þ calcd 352.0960,
found 352.0965.
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14 4387
(bs, 2 H) 7.17 (bs, 1 H) 7.22-7.30 (m, 2 H) 7.34-7.37 (m, 4 H)
8.34 (bs, 1 H) 8.37 (dd, J=4.6, 1.4 Hz, 1 H) 8.40 (d, J=7.2 Hz, 1
H) 9.19 (bs, 1 H) 11.90 (bs, 1 H) 12.63 (bs, 1 H). HRMS (M þ
H)þ calcd 332.1506, found 332.1497.
(Z)-2-(Cyclohexylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-yl-
methylene)-3,5-dihydro-4H-imidazol-4-one (21). 1H NMR (DMSO-
d6), δppm 1.04-2.02 (m, 10 H) 3.50-3.75 (m, 1 H) 7.18 (s, 1 H) 7.25
(dd, J=7.9, 4.7 Hz, 1 H) 8.34 (s, 1 H) 8.36 (dd, J=4.7, 1.5 Hz, 1 H)
8.40 (d, J=7.9 Hz, 1 H) 9.46 (s, 1 H) 11.79 (s, 1 H) 12.62 (s, 1 H).
HRMS (M þ H)þ calcd 310.1662, found 310.1654.
(Z)-2-(Cyclopropylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-yl-
methylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (22).
1H NMR (DMSO-d6), δ ppm 0.80-0.86 (m, 2 H) 0.88-0.96
(m, 2 H) 2.87 (bs, 1 H) 7.21 (s, 1 H) 7.26 (dd, J=7.9, 4.7 Hz, 1 H)
8.34 (d, J=1.8 Hz, 1 H) 8.36 (dd, J=4.7, 1.4 Hz, 1 H) 8.40 (dd,
J=7.6, 0.85 Hz, 1 H) 9.61 (bs, 1 H) 11.97 (s, 1 H) 12.63 (bs, 1 H).
HRMS (M þ H)þ calcd 268.1193, found 268.1187.
(Z)-2-[(4-Methylcyclohexyl)amino]-5-(1H-pyrrolo[2,3-b]pyr-
idin-3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochlor-
ide (23). 1H NMR (DMSO-d6), δ ppm 0.91 (d, J=6.3 Hz, 3 H)
0.98-1.12 (m, 2 H) 1.41 (td, J = 12.2, 2.7 Hz, 3 H) 1.71-1.82 (m, 2
H) 1.91-2.03 (m, 2 H) 3.57 (bs, 1 H) 7.17 (s, 1 H) 7.25 (dd, J = 7.9,
4.7 Hz, 1 H) 8.33 (bs, 1 H) 8.34-8.46 (m, 2 H) 9.35 (bs, 1 H) 11.77
(bs, 1 H) 12.62 (bs, 1 H). HRMS (M þ H)þ calcd 324.1819, found
324.1809. Percent of purity 94%.
(Z)-2-[(3-Bromobenzyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-3-
ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (15).
1H NMR (DMSO-d6), δ ppm 4.73 (bs, 2 H) 7.19 (bs, 1 H) 7.25
(dd, J=7.7, 4.6 Hz, 1 H) 7.36-7.43 (m, 1 H) 7.44-7.49 (m, 1 H)
7.57 (dt, J=8.2, 1.4 Hz, 1 H) 7.70 (s, 1 H) 8.30-8.45 (m, 3 H) 9.62
(bs, 1 H) 12.63 (bs, 1 H). HRMS (M þ H)þ calcd 396.0455,
found 396.0466.
(Z)-2-[(4-tert-Butylcyclohexyl)amino]-5-(1H-pyrrolo[2,3-b]-
pyridin-3-ylmethylene)-3,5-dihydro-4H-imidazol-4-oneDihydrochlor-
ide (24). 1H NMR (DMSO-d6), δ ppm 0.86 (s, 9 H) 0.96-1.18 (m,
3 H) 1.30-1.47 (m, 2 H) 1.74-1.87 (m, 2 H) 1.98-2.05 (m, 2 H)
3.45-3.60 (m, 1 H) 7.16 (s, 1 H) 7.23 (dd, J = 7.8, 4.7 Hz, 1 H) 8.30
(bs, 1 H) 8.32-8.43 (m, 2 H) 9.34 (d, J = 8.9 Hz, 1 H) 11.71 (bs, 1 H)
12.60 (bs, 1 H). HRMS (M þ H)þ calcd 366.2288, found 366.2293.
(Z)-5-(1H-Pyrrolo[2,3-b]pyridin-3-ylmethylene)-2-[(tetrahy-
drofuran-2-ylmethyl)amino]-3,5-dihydro-4H-imidazol-4-one Hy-
(Z)-2-[(4-Bromobenzyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-3-
ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (16).
1H NMR (DMSO-d6), δ ppm 4.70 (bs, 2 H) 7.19 (bs, 1 H) 7.24
(dd, J=7.7, 4.4 Hz, 1 H) 7.43 (d, J=8.4 Hz, 2 H) 7.62 (d, J=8.4
Hz, 2 H) 8.34-8.44 (m, 3 H) 9.63 (bs, 1 H) 12.62 (bs, 1 H).
HRMS (M þ H)þ calcd 396.0455, found 396.0464.
1
drochloride (25). H NMR (DMSO-d6), δ ppm 16.1 (m, 1 H)
1.78-1.96 (m, 3 H) 1.99 (m, 1 H) 3.58 (m, 1 H) 3.68 (m, 1 H) 3.84
(m, 1 H) 4.05 (bs, 1 H) 7.18 (s, 1 H) 7.24 (dd, J = 7.9, 4.7 Hz, 1 H)
8.30-8.41 (m, 3 H) 9.16 (bs, 1 H) 12.65 (bs, 1 H). HRMS (M þ
H)þ calcd 312.1455, found 312.1450.
(Z)-2-[(cyclohexylmethyl)amino]-5-(1H-pyrrolo[2,3-b]pyr-
idin-3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one dihydrochlor-
ide (26). 1H NMR (DMSO-d6) δ ppm 0.84-1.08 (m, 2 H) 1.12-
1.33 (m, 4 H) 1.55-1.69 (m, 2 H) 1.69-1.81 (m, 4 H) 3.28-3.36 (m,
2H)7.17(s,1H)7.25(dd,J= 7.8, 4.7 Hz, 1 H) 8.34 (d, J=2.4Hz,
1 H) 8.36 (dd, J = 4.7, 1.6 Hz, 1 H) 8.39 (d, J = 7.9 Hz, 1 H) 9.31
(bs, 1 H) 12.64 (bs, 1 H). HRMS (M þ H)þ calcd 324.1819, found
324.1805.
(Z)-2-((S)-1-Phenyl-ethylamino)-5-[1-(1H-pyrrolo[2,3-b]pyri-
din-3-yl)-methylidene]-3,5-dihydro-imidazol-4-one Dihydrochlor-
ide (17). 1H NMR (DMSO-d6), δ ppm 1.62 (d, J=6.7 Hz, 3 H)
5.08 (bs, 1 H) 7.17 (bs, 1 H) 7.24 (dd, J=7.7, 4.4 Hz, 1 H) 7.33-
7.53 (m, 5 H) 8.35 (m, 3 H) 10.01 (bs, 1 H) 12.62 (bs, 1 H). HRMS
(M þ H)þ calcd 332.1506, found 332.1507.
Alternatively the compound was obtained as follows:
A mixture of 0.110 g (0.33 mmol) of (Z)-2-(benzylthio)-5-(1H-
pyrrolo[2,3-b]pyridin-3-ylmethylene)-3,5-dihydro-4H-imidazol-4-
one (41) and 0.7 mL (5.5 mmol) of (S)-(-)-1-phenyl-ethylamine in
1 mL of anhydrous ethanol were stirred at 110 °C overnight in a
sealed tube. After evaporation of the solution in order to eliminate
the excess amine, the residue was washed with diethyl ether and
dried in a vacuum oven. The product was then salified by dissolu-
tion in 3 mL of methanol and addition of 0.3 mL of 4 M
hydrochloric acid in dioxane. After 1 h evaporation, of the solution
gave 0.100 g (80% yield) of the desired product.
(Z)-2-(Adamantylmethylamino)-5-(1H-pyrrolo[2,3-b]pyridin-
3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride
1
(27). H NMR (DMSO-d6), δ ppm 1.54-1.59 (m, 6 H) 1.59-
1.66 (m, 3 H) 1.68-1.75 (m, 3 H) 2.00 (bs, 3 H) 3.17 (d, J = 6.2
Hz, 2 H) 7.19 (s, 1 H) 7.25 (dd, J = 7.9, 4.6 Hz, 1 H) 8.34-8.38
(m, 2 H) 8.41 (d, J = 7.9 Hz, 1 H) 9.40 (bs, 1 H) 11.97 (bs, 1 H)
12.67 (bs, 1 H). HRMS (M þ H)þ calcd 376.2132, found
376.2126.
(Z)-2-[(2-Furylmethyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-
3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride
(18). 1H NMR (DMSO-d6), δ ppm 4.74 (bs, 2 H) 6.50 (dd,
J=3.1, 1.9 Hz, 1 H) 6.54 (d, J=3.1 Hz, 1 H) 7.19 (bs, 1 H) 7.25
(dd, J=7.9, 4.7 Hz, 1 H) 7.72 (dd, J=1.9, 0.8 Hz, 1 H) 8.35-8.39
(m, 2 H) 8.42 (d, J=7.9 Hz, 1 H) 9.61 (bs, 1 H) 12.62 (bs, 1 H).
HRMS (M þ H)þ calcd 308.1142, found 308.1135.
(Z)-2-(Ethylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
lene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (28). 1H
NMR (DMSO-d6), δ ppm 1.21 (t, 3 H) 3.30-3.50 (m, 2H) 7.15
(s, 1 H) 7.23 (dd, J=7.9, 4.76 Hz, 1 H) 8.30-8.41 (m, 3 H) 9.17
(bs, 1 H) 11.90 (bs, 1 H) 12.61 (bs, 1 H). HRMS (M þ H)þ
calcd 256.1193, found 256.1184.
(Z)-5-[1-(1H-Pyrrolo[2,3-b]pyridin-3-yl)-methylidene]-2-
[(thiophen-2-ylmethyl)-amino]-3,5-dihydro-imidazol-4-one Dihy-
drochloride (19). 1H NMR (DMSO-d6), δ ppm 4.91 (bs, 2 H) 7.07
(dd, J=5.0, 3.5 Hz, 1 H) 7.18 (bs, 1 H) 7.22-7.27 (m, 2 H) 7.56
(dd, J=5.0, 0.5 Hz, 1 H) 7.99-8.69 (m, 3 H) 9.63 (bs, 1 H) 12.61
(bs, 2 H). HRMS (M þ H)þ calcd 324.0914, found 324.0917.
(Z)-2-[(2-Phenylethyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-3-
ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride
(Z)-2-(Isopropylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-yl-
methylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride
(29). 1H NMR (DMSO-d6), δ ppm 1.28 (d, J=6.4 Hz, 6 H)
3.94 (bs, 1 H) 7.16 (s, 1 H) 7.23 (dd, J=7.9, 4.7 Hz, 1 H)
8.21-8.49 (m, 3 H) 9.32 (bs, 1 H) 11.78 (bs, 1 H) 12.61 (bs, 1
H). HRMS (M þ H)þ calcd 270.1349, found 270.1339.
(Z)-2-(Pentylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
1
lene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (30). H
NMR (DMSO-d6), δ ppm 0.90 (t, 3 H) 1.27-1.36 (m, 4 H)
1
(20). H NMR (DMSO-d6), δ ppm 2.90-2.98 (m, 2 H) 3.69

4388 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14
Ermoli et al.
1.53-1.68 (m, 2 H) 3.30-3.50 (m, 2 H) 7.16 (s, 1 H) 3.30-3.50
(m, 2H) 7.23 (dd, J=7.9, 4.7 Hz, 1 H) 8.29-8.42 (m, 3 H) 9.23
(bs, 1 H) 11.88 (bs, 1 H) 12.62 (bs, 1 H). HRMS (M þ H)þ calcd
298.1662, found 298.1654.
warmed at 120 °C for 3 h. The reaction mixture was cooled,
water (20 mL) was added, and the precipitate was filtered,
washed with water, and dried. 5-Nitro-1H-pyrrolo[2,3-b]pyr-
idine-3-carbaldehyde as a solid (2.00 g, 10.4 mmol, 85%) was
obtained. 1H NMR (DMSO-d6), δ ppm: 8.77 (d, J = 2.93 Hz,
1 H) 9.12 (d, J = 2.56 Hz, 1 H) 9.25 (d, J = 2.56 Hz, 1 H) 10.04
(s, 1 H) 13.41 (s, 1 H). A stirred mixture of aldehyde (0.570 g,
3 mmol), thiohydantoin (0.350 g, 3 mmol), sodium acetate
(0.740 g, 9 mmol), and glacial AcOH (15 mL) was heated at
120 °C for 3 h. After cooling, water (20 mL) was added and
the precipitate was filtered, washed with water, and dried.
The obtained (E,Z)-5-[(5-nitro-1H-pyrrolo[2,3-b]pyridin-3-yl)-
methylene]-2-thioxoimidazolidin-4-one (0.600 g, 2.08 mmol,
69%) was treated with 12.6% aqueous NaOH (0.73 mL),
methanol (6 mL), and methyl iodide (0.4 mL, 6.4 mmol) under
stirring at room temperature for 4 h. After partial concentra-
tion, water (15 mL) was added and the precipitate was filtered
and dried. Obtained (E,Z)-2-(methylthio)-5-[(5-nitro-1H-pyr-
rolo[2,3-b]pyridin-3-yl)methylene]-3,5-dihydro-4H-imidazol-4-one
G as a solid (0.550 g, 1.8 mmol, 86%). A mixture of G (0.175 g,
0.58 mmol) in ethanol (3 mL) and benzylamine (0.88 mL,
8.2 mmol) was heated at 110 °C in a closed tube for 24 h, yield-
ing the title compound (0.190 g, 0.52 mmol, 90%) as a mixture
of (E) and (Z) isomers that were separated by flash chroma-
tography (silica gel, eluant: dichloromethane/methanol 3:1)
were obtained:
(Z)-2-(Benzylamino)-5-[(5-nitro-1H-pyrrolo[2,3-b]pyridin-3-
yl)methylene]-3,5-dihydro-4H-imidazol-4-one (36). 1H NMR
(DMSO-d6), δ ppm 4.69-4.72 (m, 2 H) 6.77 (s, 1 H) 7.25 (t,
J = 7.2 Hz, 1 H) 7.34 (m, 3 H) 7.38-7.42 (m, 2 H) 8.25 (d, J =
2.2 Hz, 1 H) 9.10 (d, J = 2.5 Hz, 1 H) 10.21 (bs, 1 H) 12.81 (bs,
1 H). HRMS (M þ H)þ calcd 363.1200, found 363.1216.
and:
(E)-2-(Benzylamino)-5-[(5-nitro-1H-pyrrolo[2,3-b]pyridin-3-
yl)methylene]-3,5-dihydro-4H-imidazol-4-one (37). 1H NMR
(DMSO-d6), δ ppm 4.91 (s, 2 H) 7.17 (bs, 1 H) 7.27-7.33 (m,
3 H) 7.34-7.41 (m, 2 H) 8.27 (bs, 1 H) 8.43 (s, 1 H) 9.16 (s, 1 H)
13.01 (bs, 1 H). HRMS (MþH)þ calcd 363.1200, found
363.1210. Percent of purity 93%.
(Z)-2-[(3,3-Dimethylbutyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-3-
ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochloride (31).
1H NMR (DMSO-d6), δ ppm 0.94 (s, 9 H) 1.54 (bs, 2 H) 3.30-3.50
(m, 2 H) 7.15 (s, 1 H) 7.22 (dd, J=7.9, 4.7 Hz, 1 H) 8.31-8.35 (m,
2 H) 8.37 (d, J = 8.2 Hz, 1 H) 9.15 (bs, 1 H) 11.92 (bs, 1 H) 12.61
(bs, 1 H).
HRMS (M þ H)þ calcd 312.1819, found 312.1828.
(Z)-2-[(2-Hydroxyethyl)amino]-5-(1H-pyrrolo[2,3-b]pyridin-
3-ylmethylene)-3,5-dihydro-4H-imidazol-4-one Dihydrochlor-
1
ide (32). H NMR (DMSO-d6), δ ppm 3.62 (bs, 4 H) 7.18 (s,
1 H) 7.24 (dd, J =7.9, 4.7 Hz, 1 H) 8.34-8.37 (m, 2 H) 8.39 (d,
J=7.9 Hz, 1 H) 9.06 (bs, 1 H) 11.94 (bs, 1 H) 12.64 (bs, 1 H).
HRMS (M þ H)þ calcd 272.1142, found 272.1151.
(Z)-2-(Heptylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
lene)-3,5-dihydro-4H-imidazol-4-one (33). 1H NMR (DMSO-
d6), δ ppm 0.82-0.91 (m, 5 H) 1.20-1.39 (m, 6 H) 1.60 (m, 2 H)
3.30-3.50 (m, 2 H) 7.03 (bs, 1 H) 7.20 (dd, J=7.9, 4.7 Hz, 1 H)
8.21 (bs, 1 H) 8.34 (d, J=1.4 Hz, 1 H) 8.37-8.43 (m, 1 H) 8.92-
9.38 (m, 1 H) 11.51 (s, 1 H) 12.45 (bs, 1 H). HRMS (M þ H)þ
calcd 326.1976, found 326.1985.
(Z)-2-(Benzylamino)-5-[1-(1H-pyrrolo[2,3-b]pyridin-3-yl)-
ethylidene]-3,5-dihydro-4H-imidazol-4-one Hydrochloride
(34). To a solution of 3-acetyl, 7-azaindole (0.320 g, 2 mmol),
thiohydantoin (0.465 g, 3 mmol), and BF3 Et2O (1.52 mL, 12
3
mmol) in dry tetrahydrofuran (14 mL), under argon, triethyla-
mine (0.84 mL, 6 mmol) was added dropwise and the reaction
mixture stirred for 5 days at room temperature. The mixture was
poured in ice and pH made slightly basic by addition of sodium
bicarbonate. The solution was extracted with ethyl acetate,
dried over anhydrous sodium sulfate, and concentrated to give
an oil that crystallized from ethyl acetate (0.260 g, 1 mmol, 50%
yield). The obtained (5Z)-4-5-[1-(1H-pyrrolo[2,3-b]pyridin-3-
yl)ethylidene]-2-thioxo-imidazolidinone C1 was dissolved in
methanol (5 mL) containing aqueous sodium hydroxide solu-
tion (12.6%, 0.4 mL), and methyl iodide (0.4 mL) was added to it
under argon. After stirring at room temperature for 3 h, part of
the solvent was removed by distillation, water was added and the
precipitate was filtered and washed with water. The desired
(5Z)-3,5-dihydro-2-(methylthio)-5-[1-(1H-pyrrolo[2,3-b]pyri-
din-3-yl)ethylidene]-4H-imidazol-4-one E1 (0.220 g, 0.81
mmol, 80% yield) was obtained and used directly in the next
step.
(Z)-5-[(5-Amino-1H-pyrrolo[2,3-b]pyridin-3-yl)methylene]-
2-(benzylamino)-3,5-dihydro-4H-imidazol-4-one (39). A solu-
tion of 35 (1.10 g, 3.04 mmol) in ethyl acetate (250 mL) was
hydrogenated in the presence of 5% Pd-C (0.500 g) at 40 psi
and room temperature for 24 h. After filtration, the crude
mixture (E,Z) 38 was fractionated by flash chromatography,
eluting with dichloromethane/methanol 3:1. The title product
was obtained as a solid (0.300 g, 0.91 mmol, 30%). 1H NMR
(DMSO-d6), δ ppm 4.99 (s, 2 H) 7.20 (bs, 1 H) 7.31-7.44 (m, 5
H) 8.27 (s, 1 H) 8.32 (bs, 1 H) 8.52 (bs, 1 H). HRMS (M þ H)þ
calcd 333.1458, found 333.1474.
1H NMR (DMSO-d6), δ ppm 2.57 (s, 3 H) 2.84 (s, 3 H) 7.16
(dd, J = 8.2, 4.6 Hz, 1 H) 8.27 (dd, J = 4.6, 1.6 Hz, 1 H) 8.45 (dd,
J = 8.05, 0.98 Hz, 1 H) 8.53 (d, J = 3.1 Hz, 1 H) 11.53 (s, 1 H)
12.27 (bs, 1 H). NMR purity 80% as sum of Z/E isomers, LC-
MS purity 95%.
(Z)-N-(3-{[2-(Benzylamino)-5-oxo-1,5-dihydro-4H-imidazol-
4-ylidene]methyl}-1H-pyrrolo[2,3-b]pyridin-5-yl)acetamide Hy-
drochloride (40). Into a solution of 5-amino-7-azaindole (0.600
g, 4.51 mmol) in dry N,N-dimethylformamide (11 mL) N-[(1H-
1,2,3-benzotriazol-1-yloxy)(dimethylamino)methylene]-N-methyl-
methanaminium tetrafluoroborate (2.89 g, 9.0 mmol), 1-hydro-
xybenzotriazole (1.21 g, 9.0 mmol), and glacial AcOH (0.26 mL),
diisopropylethylamine (3.1 mL, 17.8 mmol) was slowly dropped
under stirring. The reaction mixture was stirred at room tem-
perature for 18 h, concentrated, and the residue was purified by
flash chromatography eluting with dichloromethane/methanol
4:1. 1H-pyrrolo[2,3-b]pyridin-5-yl acetamide was obtained in
The crude product (0.200 g, 0.73 mmol) was suspended in
ethanol (5 mL) and benzylamine (2 mL) in a sealed tube and
heated to 110 °C overnight. The solvent was evaporated by
distillation, diethyl ether (5 mL) was added, and the precipitate
was filtered and purified by flash chromatography, eluting with
dichloromethane/methanol 12:1. The obtained product was
dissolved in methanol, a slight excess of 4 N hydrochloric acid
in dioxane was added, and the solution was stirred 30 min.
Diethyl ether was added, and the precipitate was filtered,
washed with diethyl ether, and dried. The title compound was
obtained as a yellow solid (0.160 g, 0.48 mmol, 66%). 1H NMR
(DMSO-d6), δ ppm 2.66 (s, 3 H) 4.52-4.63 (m, 2 H) 7.20 (bs,
1 H) 7.30-7.46 (m, 5 H) 7.97 (s, 1 H) 8.08-8.15 (m, 1 H) 8.30-
8.35 (m, 1 H) 9.19 (bs, 1 H) 10.92 (bs, 1 H) 12.43 (bs, 1 H).
HRMS (M þ H)þ calcd 332.1506, found 332.1518.
1
95% yield (0.750 g, 4.2 mmol). H NMR (DMSO-d6), δ ppm:
2.07 (s, 3 H) 6.41 (m, 1 H) 7.43 (t, J=2.93 Hz, 1 H) 8.22 (d, J=
2.07 Hz, 1 H) 8.26 (d, J=2.32 Hz, 1 H) 9.92 (s, 1 H) 11.51 (s, 1 H).
A mixture of the acetamide (0.790 g, 4.5 mmol) and hexamethy-
lenetetramine (0.950 g, 6.75 mmol) in 30% AcOH (21 mL) was
warmed at 100 °C for 4 h. After cooling, the mixture was diluted
with water (10 mL), the precipitate was filtered, washed with
water, and dried. N-(3-Formyl-1H-pyrrolo[2,3-b]pyridin-5-yl)-
(E,Z)-2-(Benzylamino)-5-[(5-nitro-1H-pyrrolo[2,3-b]pyridin-
3-yl)methylene]-3,5-dihydro-4H-imidazol-4-one (35). A mixture
of 5-nitro-7-azaindole (2.00 g, 12.2 mmol) and hexamethyle-
netetramine (2.58 g, 18.4 mmol) in 30% AcOH (18 mL) was

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14 4389
acetamide (0.700 g, 3.45 mmol, 76%) was obtained . 1H NMR
(DMSO-d6), δ ppm: 2.10 (s, 3 H) 8.43 (d, J = 3.17 Hz, 1 H) 8.50
(d, J=2.44 Hz, 1 H) 8.73 (d, J=2.32 Hz, 1 H) 9.9 (s, 1 H) 10.12 (s,
1 H) 12.60 (s, 1 H). A mixture of N-(3-formyl-1H-pyrrolo[2,3-b]-
pyridin-5-yl)acetamide (0.200 g, 1 mmol), thiohydantoin (0.116
g, 1 mmol), sodium acetate (0.246 g, 3 mmol), and glacial AcOH
(5 mL) was heated at 125 °C for 3 h. After cooling, water (5 mL)
was added, and the precipitate was filtered, washed with water,
and dried. To the so obtained N-{3-[(5-oxo-2-thioxoimidazoli-
din-4-ylidene)methyl]-1H-pyrrolo[2,3-b]pyridin-5-yl}acetamide
(0.240 g, 0.79 mmol), dissolved in 12.6% aqueous NaOH (0.32 mL)
and methanol (4 mL), methyl iodide (0.2 mL, 3.2 mmol) was
added and the mixture was stirred at room temperature for
3 h under argon. After partial concentration, water (5 mL) was
added and the precipitate was filtered and dried. N-(3-{[2-
(Methylthio)-5-oxo-1,5-dihydro-4H-imidazol-4-ylidene]methyl}-
1H-pyrrolo[2,3-b]pyridin-5-yl)acetamide H was obtained as
a solid (0.220 g, 0.7 mmol, 87%). A mixture of H (0.200 g,
0.635 mmol), benzylamine (0.5 mL, 4.58 mmol) and EtOH (3 mL)
were put in a closed tube and heated at 110 °C for 4 h. After
cooling, the precipitate was filtered, washed with ethanol, and
dried to yield the desired compound (0.220 g, 0.59 mmol, 92%).
The compound was dissolved in methanol, treated with 4 N
hydrochloric acid in dioxane, and diluted with ethyl acetate until
precipitation of the hydrochloride salt occurred. Filtration of
the solid afforded the title compound as a white solid. 1H NMR
(DMSO-d6), δ ppm 2.11 (s, 3 H) 4.72 (bs, 2 H) 6.98 (bs, 1 H)
7.30-7.50 (m, 5 H) 8.30 (bs, 1 H) 8.36 (bs, 1 H) 8.61 (bs, 1 H) 9.54
(bs, 1 H) 10.14 (bs, 1 H) 12.45 (bs, 1 H). HRMS (M þ H)þ calcd
375.1564, found 375.1573.
in methanol, stirred 30 min, filtered, and dried to yield (Z)-
2-(methylthio)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-
1,3-thiazol-4(5H)-one F as a yellow solid (8.15 g, 29.5 mmol,
96%). To assign the configuration of the exocyclic double
bond, the NMR experiment gselJXH was run on compound
F as previously described.33 The experiment enabled us to
assign the compound the
Z
configuration.34 1H NMR
(500 MHz, DMSO-d6) δ ppm 2.82 (s, 3 H) 7.26 (dd, J = 7.9,
4.7 Hz, 1 H) 7.97 (d, J = 1.9 Hz, 1 H) 8.11 (s, 1 H) 8.37 (dd,
J = 4.7, 1.5 Hz, 1 H) 8.44 (dd, J = 7.9, 1.5 Hz, 1 H) 12.82
(bs, 1 H).
To a suspension of F (0.200 g, 0.77 mmol) in absolute ethanol
(5 mL), benzylamine (1.05 mL, 9.7 mmol) was added and the
mixture was refluxed overnight. After cooling to room tempera-
ture, the precipitate was filtered, suspended in methanol (2 mL),
4 M hydrochloric acid in dioxane (0.5 mL) was added, and the
mixture was stirred at room temperature for 30 min. The yellow
precipitate was filtered and purified by flash chromatography,
eluting with dichloromethane/methanol 12:1. The product was
suspended in methanol (2 mL), 4 M hydrochloric acid in dioxane
(0.5 mL) was added, and the mixture was stirred at room
temperature for 30 min. The precipitate was filtered and washed
with methanol and diethyl ether. The title compound was
obtained as a yellow solid (0.200 g, 0.59 mmol, 76%). 1H
NMR (DMSO-d6), δ ppm 4.75 (s, 2 H) 7.25 (dd, J = 7.8, 4.8
Hz, 1 H) 7.30-7.43 (m, 5 H) 7.71 (d, J = 2.4 Hz, 1 H) 7.88 (s,
1 H) 8.35-8.40 (m, 2 H) 9.99 (bs, 1 H) 12.48 (bs, 1 H). HRMS
(M þ H)þ calcd 335.0961, found 335.0954.
By employing the above-described procedure the following
compounds were also prepared:
(Z)-2-(Benzylthio)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
lene)-3,5-dihydro-4H-imidazol-4-one (41). To a solution of
(Z)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethylene)-2-thioxoimidazoli-
din4-one (0.500 g, 2.05 mmol) in 12.6% aqueous NaOH (1 mL)
and methanol (5 mL), benzyl bromide (0.430 g, 2.5 mmol) was
added and the reaction mixture was stirred at room temperature
for 18 h. Most of the solvent was removed by distillation, and
the precipitate was filtered and washed with water and diethyl
ether and dried. The crude material was purified by flash chroma-
tography on silica gel (eluant: dichloromethane/methanol 15:1).
The title compound was obtained as a yellow solid (0.700 g,
2 mmol).
(Z)-2-Isopropylamino-5-[1-(1H-pyrrolo[2,3-b]pyridin-3-yl)-
methylidene]-thiazol-4-one Dihydrochloride (43). 1H NMR
(DMSO-d6), δ ppm 1.26 (d, J = 6.6 Hz, 6 H) 4.13-4.29 (m,
1 H) 7.26 (dd, J = 7.9, 4.7 Hz, 1 H) 7.69 (d, J = 2.2 Hz, 1 H)
7.86 (s, 1 H) 8.23-8.48 (m, 2 H) 9.55 (bs, 1 H) 12.49 (bs, 1 H).
HRMS (M þ H)þ calcd 287.0961, found 287.0964. Percent of
purity 92%.
(Z)-2-[(Furan-2-ylmethyl)-amino]-5-[1-(1H-pyrrolo[2,3-b]pyr-
idin-3-yl)-methylidene]-thiazol-4-one Dihydrochloride (44). 1H
NMR (DMSO-d6), δ ppm 4.75 (s, 2 H) 6.43-6.45 (m, 1 H)
6.46-6.48 (m, 1 H) 7.26 (dd, J = 7.9, 4.7 Hz, 1 H) 7.68 (dd, J =
1.8, 0.85 Hz, 1 H) 7.71 (d, J = 2.2 Hz, 1 H) 7.88 (s, 1 H) 8.29-
8.45 (m, 2 H) 9.97 (bs, 1 H) 12.51 (bs, 1 H). HRMS (M þ H)þ
calcd 325.0754, found 325.0755.
(Z)-2-((S)-1-Phenyl-ethylamino)-5-[1-(1H-pyrrolo[2,3-b]pyri-
din-3-yl)-methylidene]-thiazol-4-one Hydrochloride (45). 1H
NMR (DMSO-d6), δ ppm 1.56 (d, J = 6.9 Hz, 3 H) 5.25-
5.37 (m, 1 H) 7.25 (dd, J = 7.9, 4.7 Hz, 1 H) 7.27-7.34 (m, 1 H)
7.38-7.43 (m, 4 H) 7.70 (d, J = 2.3 Hz, 1 H) 7.85 (s, 1 H) 8.37 (s,
2 H) 10.00 (bs, 1 H) 12.49 (bs, 1 H). HRMS (M þ H)þ calcd
349.1118, found 349.1119.
2. Registry Numbers (RN). Hyppuric acid (RN, 495-69-2),
nicotinoylglycine (RN, 583-08-4), 4-methylhippuric acid (RN,
27115-50-0), 3-methylhippuric acid (RN, 27115-49-7), 7-azain-
dole-3-carboxaldehyde (RN, 4649-09-6), 3-acetyl-7-azaindole
(RN, 83393-46-8), 5-nitro-7-azaindole (RN, 101083-92-5), 5-
amino-7-azaindole (RN, 100960-07-4), thiohydantoin (RN,
503-87-7), rhodanine (RN, 141-84-4).
1H NMR (DMSO-d6), δ ppm 4.63 (s, 2 H) 7.12 (s, 1 H) 7.19
(dd, J=7.9, 4.7 Hz, 1 H) 7.27-7.32 (m, 1 H) 7.37 (t, J=7.3 Hz, 2
H) 7.54 (d, J=7.3 Hz, 2 H) 8.32 (dd, J=4.7, 1.3 Hz, 1 H) 8.45 (d,
J= 2.5 Hz, 1 H) 8.80 (dd, J=7.9, 1.3 Hz, 1 H) 11.64 (bs, 1 H)
12.44 (bs, 1 H). HRMS (M þ H)þ calcd 335.0961, found
335.0958.
(Z)-2-(Benzylamino)-5-(1H-pyrrolo[2,3-b]pyridin-3-ylmethy-
lene)-1,3-thiazol-4(5H)-one Hydrochloride (42). A mixture of 7-
azaindole-3-carboxaldehyde (5.98 g, 41 mmol), rhodanine
(4.96 g, 41 mmol), and sodium acetate (11.30 g, 138 mmol) in
glacial acetic acid (60 mL) was refluxed under stirring for 5 h.
After cooling in ice bath, the precipitate was filtered and
washed with 95% ethanol. After drying, (Z)-5-(1H-pyrrolo-
[2,3-b]pyridin-3-ylmethylene)-2-thioxo-1,3-thiazolidin-4-one D
1
was obtained as a yellow solid (9.52 g, 36.5 mmol, 88%). H
NMR (DMSO-d6), δ ppm 7.28 (dd, J = 7.9, 4.6 Hz, 1 H) 7.93 (s,
1 H) 7.96 (d, J=0.6Hz, 1 H) 8.36 (d, J=5.9Hz, 1 H) 8.38 (dd, J =
4.6, 1.6 Hz, 1 H) 8.45 (dd, J = 7.9, 1.5 Hz, 1 H) 12.82 (bs, 1 H)
13.62 (bs, 1 H) 13.63-13.64 (m, 1 H). To a solution of D (7.98 g,
30.6 mmol) in 12.6% aqueous NaOH (12 mL) and methanol
(80 mL), methyl iodide (2.25 mL, 36.1 mmol) was added and the
reaction mixture was stirred at room temperature for 4 h. Most
of the solvent was removed under reduced pressure, and the
precipitate was separated by filtration and washed with water
(50 mL) and with diethyl ether (50 mL). The washings were
combined, concentrated, and extracted with dichloromethane. The
dichloromethane was dried over anhydrous sodium sulfate and
combined to the first solid crop. The whole crop was suspended
3. Molecular Modeling. See ref 10.
4. In Vitro Kinase Assays. See ref 10.
5. Cell Culture. See ref 10.
6. Inhibition of Cell Proliferation. See ref 10.
7. Cell Permeability. See ref 12.
Acknowledgment. We are grateful to the personnel of
Biochemical Screening, to Dario Ballinari and the collea-
gues of Cellular Screening, and to Nilla Avanzi with the
group of Assay Development of Nerviano Medical
Sciences.

4390 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 14
Ermoli et al.
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