Structure-based design of 2-arylamino-4-cyclohexylmethoxy-5-nitroso-6- aminopyrimidine inhibitors of cyclin-dependent kinase 2

Article abstract of DOI:10.1039/b703241b

An efficient synthesis of 2-substituted O⁴-cyclohexylmethyl-5- nitroso-6-aminopyrimidines from 6-amino-2-mercaptopyrimidin-4-ol has been developed and used to prepare a range of derivatives for evaluation as inhibitors of cyclin-dependent kinas

Full text of DOI:10.1039/b703241b

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Structure-based design of 2-arylamino-4-cyclohexylmethoxy-5-nitroso-
6-aminopyrimidine inhibitors of cyclin-dependent kinase 2
Francesco Marchetti,a Kerry L. Sayle,a Johanne Bentley,b William Clegg,c Nicola J. Curtin,b Jane A. Endicott,d
Bernard T. Golding,c Roger J. Griffin,a Karen Haggerty,a Ross W. Harrington,c Veronique Mesguiche,a David R.
Newell,b Martin E. M. Noble,d Rachel J. Parsons,a David J. Pratt,d Lan Z. Wangb and Ian R. Hardcastle*a
Received 5th March 2007, Accepted 30th March 2007
First published as an Advance Article on the web 23rd April 2007
DOI: 10.1039/b703241b
An efficient synthesis of 2-substituted O4-cyclohexylmethyl-5-nitroso-6-aminopyrimidines from
6-amino-2-mercaptopyrimidin-4-ol has been developed and used to prepare a range of derivatives for
evaluation as inhibitors of cyclin-dependent kinase 2 (CDK2). The structure–activity relationships
(SARs) are similar to those observed for the corresponding O6-cyclohexylmethoxypurine series with the
2-arylsulfonamide and 2-arylcarboxamide derivatives showing excellent potency. Two compounds, 4-(6-
amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-N-(2-hydroxyethyl)benzenesulfonamide
(7q) and 4-(6-amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-N-(2,3-dihydroxypropyl)-
benzenesulfonamide (7s), were the most potent with IC50 values of 0.7 0.1 and 0.8 0.0 nM against
CDK2, respectively. The SARs determined in this study are discussed with reference to the crystal
structure of 4-(6-amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-N-(2,3-dihydroxy-
propyl)benzenesulfonamide (7j) bound to phosphorylated CDK2/cyclin A.
been reported based on a structurally diverse range of scaffolds.
Introduction
These include derivatives of the monoheterocycles—pyrimidine,8
[1,2,4]triazole,9 pyrazole,10 pyridine;11 biheterocycles—purine,12–15
The progression of cells through the cell-cycle is a highly ordered
process, which is strictly controlled by the cyclin-dependent kinase
(CDK) family of enzymes and their cyclin partners. Regulation of
the serine-threonine kinase activity of specific CDKs, necessary to
allow the cells to pass through cell-cycle checkpoints, is achieved by
the binding of the cyclin partner and phosphorylation to produce
the fully activated protein kinase complex.1 In cancer, the presence
of oncogenic signalling pathways, or the absence of control
resulting from the loss or mutation of tumour suppressor genes,
inevitably results in abnormal cell-cycle control and increased
CDK/cyclin activity.2,3 For this reason, the development of
potent and selective CDK inhibitors has become an important
therapeutic goal.4–6
The development of potent and selective small-molecule ATP-
competitive kinase inhibitors has been successful for a number
of therapeutic targets. New drugs have entered clinical use,
notably imatinib that inhibits Bcr-Abl kinase and c-Kit kinase,
gefitinib and erlotinib which target the EGFR tyrosine kinase,
and lapatinib, a dual EGFR, Her2 tyrosine kinase inhibitor.7
A large number of small-molecule inhibitors of CDK2 have
[1,3,5]triazine-pyridine,16
1,4,5,6-tetrahydropyrrolo[3,4-c]pyra-
zole,17 pyrazolo[3,4-c]pyridazine,18 triazolo[1,5-a]pyrimidine,19
pyrazolo[1,5a]pyrimidine;20 triheterocycles—benzodipyrazole,21
aminoimidazo[1,2a]pyridine.22 All the inhibitors are competitive
with ATP, and vary in their potency and selectivity among the
other members of the CDK family and also other unrelated
kinases.
The biological effects of inhibition of CDK2 have been studied
using molecular genetic approaches in cell lines and knockout
animals. Experiments in cell lines have produced conflicting
results, suggesting that CDK2 is not essential for proliferation in
all situations.23,24 Additionally, CDK2-knockout mice have been
generated which are viable and apparently normal, other than
being infertile.25,26 These results cast doubt over the inhibition of
CDK2 as a valuable therapeutic target. However, it should be
noted that the absence or attenuation of a protein through genetic
knockdown or knockout does not exactly mirror the situation
where a protein is present at its usual cellular concentration, but
is inactivated through a small-molecule inhibitor. Furthermore,
a number of studies to date have demonstrated anti-tumour
activity in tumour models with CDK2 inhibitors that have
significant activity against other CDKs, including CDK4, CDK7
and CDK9,27–29 and the first generation of CDK inhibitors has
entered clinical trials as anti-tumour agents.30
aNorthern Institute for Cancer Research, School of Natural Sciences—
Chemistry, Bedson Building, Newcastle University, Newcastle Upon Tyne,
UK NE1 7RU. E-mail: I.R.Hardcastle@ncl.ac.uk; Tel: +44 (0)191 222
6645
bNorthern Institute for Cancer Research, Paul O’Gorman Building, Medical
School, Framlington Place, Newcastle University, Newcastle Upon Tyne,
UK NE2 4HH
We have previously reported the purine NU6102 (1) as a
highly potent and selective ATP-competitive inhibitor of CDK2
(Ki = 6 nM), developed from the lead compound O6-cyclohexyl-
methoxyguanine NU2058 (CDK2 Ki = 12 lM).31,32 The X-ray
crystal structure of 1 bound to CDK2 shows the purine core
cSchool of Natural Sciences—Chemistry, Bedson Building, Newcastle Uni-
versity, Newcastle Upon Tyne, UK NE1 7RU
dLaboratory of Molecular Biophysics and Department of Biochemistry,
University of Oxford, Oxford, UK OX1 3QU
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making a triplet of hydrogen bonds within the ATP binding
site and two hydrogen bonds between the sulfonamide group
and Asp86 of CDK2. We have also demonstrated previously
that a series of nitrosopyrimidines are CDK2 inhibitors, e.g.
NU6027 (2; CDK2 Ki = 1.3 lM). The nitroso group induces
a ‘purine-mimetic’ conformation by hydrogen bonding to the
adjacent NH2 group. The X-ray structure of 2 in complex with
CDK2 shows the pyrimidine binding in a similar orientation
to NU2058 and 1.12 A limited series of analogues of 2 that
explored similar structural modifications to those leading to the
development of 1 has been communicated.8 In this paper we
report the synthesis of an expanded range of 2-arylamino-4-
cyclohexylmethyl-5-nitroso-6-aminopyrimidines, based on 2. The
structure–activity relationships for the inhibition of CDK2 are
discussed with reference to an X-ray crystal structure of a key
inhibitor bound to the CDK2/cyclinA protein complex.
to unambiguously assign the structure of 4a (Fig. 1). The final sub-
stitution was carried out using sodium cyclohexylmethoxide in cy-
clohexylmethanol, giving the trisubstituted pyrimidine 5. Removal
of the p-methoxybenzyl protecting groups with TFA, followed
by nitrosation, gave 6-amino-2-anilino-4-cyclohexylmethoxy-5-
nitrosopyrimidine (7a). An attempt to follow the same reaction
scheme using 4-amino-N,N-dimethylbenzenesulfonamide, how-
ever, met with failure. The lack of regioselectivity in the initial
substitution, and the formation of unwanted substitution products
in the second step of Scheme 1, rendered this route unsuitable for
the synthesis of a series of analogues.
We considered that a more efficient synthesis could be achieved
from 6-amino-2-mercaptopyrimidin-4-ol, which would allow the
introduction of the anilino and cyclohexylmethoxy substituents
and avoid the complications of regioselectivity seen in Scheme 1.
The mercaptopyrimidine was alkylated to give the n-butyl sulfide
(8) in excellent yield (Scheme 2), and then the cyclohexylmethoxy
group was introduced under Mitsonubu conditions to give 9 in
good yield. Direct displacement of the butylsulfide group from
9 with anilines proved unsuccessful, so the leaving group ability
was improved by oxidation to the sulfone (10) using mCPBA,
prior to displacement with the appropriate anilines to give the
2-arylaminopyrimidines 6b–s. The optimum conditions for the
sulfone displacement were found to be with trifluoroethanol as
solvent and five equivalents of TFA as catalyst, as described
previously.33 Under these conditions, the displacements with
various anilines proceeded in moderate to good yields. For the
final step, nitrosation under standard conditions gave the desired
5-nitrosopyrimidines (7b–s).12
Results and discussion
Chemical synthesis
The initial route to the target 2,4-disubstituted pyrimidines used
2,4,6-trichloropyrimidine as the starting material. Substitution
with bis-p-methoxybenzylamine in refluxing ethanol, gave both
the 2- and 4-substituted pyrimidines (3a and 3b), which were
separable by chromatography (Scheme 1). Unambiguous structure
SAR Discussion
A series of 2-arylamino-5-nitrosopyrimidines was prepared and
evaluated for CDK2 inhibitory activity and the results are shown
in Table 1. Compounds lacking the 5-nitroso group (6b, 6e, 6g, 6h,
and 6j) are at least 1 × 103 times less potent as CDK2 inhibitors
compared with their 5-nitroso counterparts (7b, 7e, 7g, 7h, and 7j).
These results are consistent with previous findings which showed
that the 5-nitroso group forms an intramolecular hydrogen bond
with the 6-amino group and orientates one of the amino NH
bonds correctly to interact with the backbone carbonyl of Glu 81
of CDK2.12,34
As predicted from the results in the comparable purine series,32
the nature and position of the substituent on the N2-aryl moiety
has a profound effect on the CDK inhibitory activity. Small-
lipophilic substituents at the 3-position (7b, 7d, 7e) produced
modest improvements in activity compared with the parent
1
determination for 3a and 3b was not possible from their H and
13C NMR spectra, so an X-ray crystal structure was obtained
for 3a that confirmed it as the desired isomer (Fig. 1). A
second substitution of the 2-substituted pyrimidine 3a with p-
methoxyaniline was achieved under more forcing conditions, in
refluxing n-butanol with triethylamine as base, giving the 2,4-
disubstituted pyrimidine 4a, accompanied by the 2,6-disubstituted
product 4b, in a 2 : 3 ratio. Again, X-ray crystallography was used
compound (2, IC50 = 2.2
0.6 lM for CDK2), whereas polar
substituents attached by a methylene group (7g and 7i) resulted
in up to 60-fold improvements in potency. In line with the
purine series, the introduction of polar substituents at the 4-
aryl position proved favourable. Compounds bearing 4-hydroxy
or 4-carboxamido substituents (7c and 7j) showed a 100-fold
improvement in activity, whereas the 4-sulfonamido substituent
7m gave a 2000-fold improvement in activity over the parent 2.
We have previously reported the X-ray crystal structure of
carboxamide 7j bound to the CDK2/cyclin A phosphorylated
on Thr160 (T160pCDK2/cyclin A) (Fig. 2, PDB accession code
1OGU).8 Compounds 7j and 2 bind in a similar orientation within
Fig. 1 Molecular structures of A: 3a; B: 4a from X-ray crystallography.
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Scheme 1 Reagents and conditions: (a) bis-(4-methoxybenzyl)amine, Et3N, n-BuOH, 75 ◦C; (b) p-anisidine, Et3N, n-BuOH, DMSO, 95 ◦C; (c)
cyclohexylmethanol, Na, 170 ◦C; (d) TFA, 60 ◦C; (e) AcOH, H2O, NaNO2.
Scheme 2 Reagents and conditions: (a) EtOH, NaOH, n-BuBr; (b) cyclohexylmethanol, PPh3, DEAD, THF, 0 ◦C; (c) mCPBA, DCM; (d) appropriate
aniline, TFE, TFA, D; (e) AcOH, H2O, NaNO2.
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Table 1 Inhibition of CDK2 by 4-cyclohexylmethoxypyrimidines
CDK2 IC50 values (nM)
or % inhibition at stated concentration
Compound
R
X
2a
—
4-OMe
3-Br
3-Br
4-OH
3-OMe
3-SMe
3-SMe
NO
NO
H
NO
NO
NO
H
NO
NO
H
NO
H
NO
NO
H
NO
H
NO
H
NO
H
2.2 0.6
215 50
26 000 6000
500 200
7ab
6b
7bb
7c
16
3
7d
6e
340 70
60 000 5000
400 100
7e
7fb
6g
7g
6h
7h
7i
4-SMe
120 30
3-CH2CN
3-CH2CN
4-CH2CN
4-CH2CN
3-CH2OH
4-CONH2
4-CONH2
4-CON(CH3)2
4-CON(CH3)2
4-CON(C2H5)2
4-CON(C2H5)2
4-SO2NH2
4-SO2NH2
4-SO2N(C2H5)2
4-SO2N(C2H5)2
41 4% (10 lM)
33
24 000 6000
64
3
3
45 21
59 000 31 000
6jb
7jb
6k
7k
6l
34
8
49% (100 lM)
80 10
29 9% (10 lM)
200 100
2930 400
1.0 0.3
7l
6mb
7mb
6n
7n
7o
NO
H
NO
NO
33 9% (10 lM)
86
8
8.1 0.25
7p
NO
19
1
7q
7r
NO
NO
0.7 0.1
1.3 0.2
7s
NO
0.8 0.0
a Ref. 12. b Ref. 8.
the CDK2 ATP binding site. Compound 7j forms three hydrogen
bonds with the hinge region of the enzyme, namely N6 to the
peptide carbonyl of Glu81, and N1 and N2 to the backbone
amide and carbonyl groups of Leu83, respectively. The 5-nitroso
group forms the anticipated intramolecular hydrogen bond to
N6, locking the molecule into a purine-like conformation. The
N2 aryl ring stacks against the peptide backbone between His84
and Gln85. The orientation of the carboxamide substituent could
not be determined unambiguously. However, the formation of an
additional hydrogen bond from a carboxamide NH to the side
chain of Asp86 is a reasonable interpretation of the data and is
consistent both with the SARs and the observed structure of the
sulfonamide 2. The interaction of at least one carboxamide or
sulfonamide NH with CDK2 can be inferred from the loss of
activity observed for the dialkylcarboxamides (7k and 7l) and the
diethylsulfonamide (7n), consistent with the structural data for 7j.
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CDK7/cyclinH, and CDK9/cyclinT (Table 2). Both inhibitors
showed excellent selectivity for CDK2, with around 100-fold
selectivity observed against CDK1/cyclinB, and around 1000-fold
selectivity against the other CDK/cyclin complexes.
Conclusions
Synthesis of 2-substituted O4-cyclohexylmethyl-5-nitroso-6-
aminopyrimidines from 2,4,6-trichloropyrimidine required
the separation of mixtures of regioisomers at the first two
steps and was not amenable to the introduction of a range of
substituents. The improved route, from 6-amino-2-mercaptopyri-
midin-4-ol,8 has allowed the preparation of a range of derivatives
for evaluation as inhibitors of CDK2. The structure activity
relationships observed follow similar trends to those for the
corresponding O6-cyclohexylmethoxypurine series, with the
2-arylsulfonamide and 2-arylcarboxamide derivatives showing
excellent potency. Two compounds, 4-(6-amino-4-cyclohexyl-
methoxy-5-nitrosopyrimidin-2-ylamino)-N-(2-hydroxyethyl)ben-
zenesulfonamide (7q) and 4-(6-amino-4-cyclohexylmethoxy-
5-nitrosopyrimidin-2-ylamino)-N-(2,3-dihydroxypropyl)benzene-
sulfonamide (7s), showed excellent potency against CDK2, with
IC50 values of 0.7 0.1 and 0.8 0.0 nM, respectively. Excellent
selectivity within the CDK family was found for 7m and 7q. These
compounds are among the most potent and selective CDK2
inhibitors reported to date.
Fig. 2 A: Crystal structure of 7j bound to Thr160pCDK2/cyclin A,
overall fold. CDK2 and cyclin A are rendered in green and gold ribbons,
respectively. Compound 7j occupies the ATP binding site and is drawn in
ball and stick mode with carbon, nitrogen, and oxygen atoms coloured
green, red, and blue, respectively. B: Compound 7j bound to the CDK2
active site. The side chains of selected residues that line the CDK2 active
site are included. Hydrogen bonds between 7j and CDK2 are drawn as
dashed lines.
The X-ray crystal structure of the T160pCDK2/cyclin
A/purine 2 complex shows that only one of the sulfonamide
protons makes a hydrogen bond to Asp68, suggesting that substi-
tution of the other position may be favourable.32 It was anticipated
that the pyrimidines would behave similarly. The monoalkylsulfon-
amides (7o–s) retained potent activity, in particular against CDK2.
The 2-hydroxyethyl- and 2,3-dihydroxypropylsulfonamides (7q
and 7s) displayed a modest improvement in activity compared
with the parent 7m, and are amongst the most potent CDK2
inhibitors reported to date. The improvement in activity suggests
that additional interactions may be formed between the additional
hydroxyl group(s) and the enzyme. The formation of additional
favourable hydrogen bonding interactions, in the region accessed
by the sulfonamide substituents, has been observed in the purine
series. For example, the X-ray structure of sulfoxide 8 bound to
CDK2 shows the amine and hydroxyl groups bound to the side
chain carboxyl group of Asp86.35
Experimental
Reagents were purchased from fine chemical vendors, and used as
received unless otherwise stated. Solvents were purified and stored
according to standard procedures. Petrol refers to that fraction in
the boiling range 40–60 ◦C. Melting points were obtained on a
Stuart Scientific SMP3 apparatus and are uncorrected. Thin layer
chromatography was performed using silica gel plates (Kieselgel
60F254; 0.2 mm), and visualized with UV light or potassium
permanganate. Chromatography was conducted under medium
pressure on silica (BDH silica gel 40–63 lm). Proton (1H) and
carbon (13C) nuclear magnetic resonance (NMR) spectra were
recorded on a Bruker Avance 300 spectrometer at 300 MHz or
75 MHz, repectively, employing TMS or the solvent as internal
standard. NH signals appeared as broad singlets (br s) exchange-
able with D2O. Mass spectra were determined on a Micromass
Autospec M spectrometer in electron impact (EI) mode. Liquid
Chromatography-Mass Spectrometry (LCMS) was carried out
on a Micromass Platform instrument operating in positive and
negative ion electrospray mode, employing a 50 × 4.6 mm C18
column (Supelco Discovery or Waters Symmetry) and a 15 min
gradient elution of 0.05% formic acid and methanol (10–90%).
IR spectra were recorded on a Bio-Rad FTS 3000MX diamond
ATR. Elemental analyses were performed by Butterworth
The CDK selectivity of two of the most potent CDK2 inhibitors,
the sulfonamide 7m and the hydroxyethylsulfonamide 7q, was
evaluated using a panel of CDK1/cyclinB, CDK4/cyclinD,
Table 2 Selectivity of inhibition of CDKs by 7m and 7q
IC50 values (nM)
CDK4/D
Compound
CDK1/B
CDK2/A
CDK7/H
CDK9/T
7m
7q
100 10
56 20
1
0.3
1500 500
1300 500
2800 1300
4800 2600
740 100
2630 200
0.7 0.1
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6-(Cyclohexylmethoxy)-N4,N4-bis(4-methoxybenzyl)-N2-(4-
Laboratories, Middlesex, UK. High-resolution mass spectra were
recorded at the EPSRC Mass Spectrometry Service, Swansea, UK.
methoxyphenyl)pyrimidine-2,4-diamine (5)
Sodium (0.036 g◦, 1.55 mmol) was heated in cyclohexylmethanol
(1.5 mL) at 120 C under N2 for 1 h. 4 (0.38 g, 0.77 mmol) was
added and the mixture heated at 160 ◦C for 3 h, then allowed to
cool, diluted with petrol (60 mL), and washed with water (3 ×
30 mL). The organic layer was dried (Na2SO4) and concentrated
in vacuo. Chromatography (silica; 10% ethyl acetate, petrol) gave 5
as a pale yellow oil containing residual cyclohexylmethanol, which
was used without further purification. (0.88 g). dH (300 MHz, d6-
DMSO) 0.84–1.38 (m, C6H11), 1.68–1.77 (m, C6H11), 3.71 (3H, s,
OCH3), 3.76 (6H, s, 2 × OCH3), 4.03 (2H, d, J = 6.7 Hz, OCH2),
4.66 (4H, br s, 2 × NCH2), 5.34 (1H, s, H5), 6.77 (2H, d, J =
9.0 Hz, ArH), 6.92 (4H, d, J = 8.5 Hz, ArH), 7.19 (4H, d, J =
8.0 Hz, ArH), 7.58 (2H, d, J = 9.0 Hz, ArH), 8.86 (1H, s, D2O ex,
NH). m/z (ESI+) = 569 [M + H]+.
2,6-Dichloro-N,N-bis(4-methoxybenzyl)pyrimidin-4-amine (3a)
A mixture of 2,4,6-trichloropyrimidine (2.2 mL, 19 mmol) and
bis-(4-methoxybenzyl)amine (4.8 g, 19 mmol) and triethylamine
(3.2 mL, 22.7 mmol) in n-butanol (20 mL) was heated to
75 ◦C for 3 h, then allowed to cool and concentrated in vacuo.
Chromatography (silica; 10% ethyl acetate, petrol) gave 3a as a
white solid (2.5 g, 33%) mp 129–131 ◦C; mmax/cm−1 3000, 2838
1610, 1568, 1487, 1127. dH (300 MHz, d6-DMSO) 3.77 (3H, s,
OCH3), 4.64 (2H, br s, NCH2), 4.82 (2H, br s, NCH2), 6.89 (1H, s,
H5), 6.94 (4H, d, J = 8.5 Hz, ArH), 6.94 (4H, d, ArH), 7.17 (2H,
br s, ArH), 7.26 (2H, br s, ArH); dC (125 MHz, d6-DMSO; DEPT)
50.58 (sp2), 55.82 (sp3), 101.59 (sp), 114.78 (sp), 128.87 (sp), 129.94
(sp), 159.18 (q), 159.42 (q), 159.74 (q), 164.28 (q). m/z (ESI+) =
404 [M + H]+. HRMS (EI) m/z Calcd for C20H19Cl2N3O2: 404.0927
[M + H]+. Found 404.0932 [M + H]+. C20H19Cl2N3O2 requires C,
59.42; H, 4.74; N, 10.39; found C, 59.41; H, 4.73 N, 10.33%.
6-(Cyclohexylmethoxy)-N2-(4-methoxyphenyl)pyrimidine-2,4-
diamine (6a)
A solution of 5 (0.44 g, corrected to 0.2 mmol) in trifluoroacetic
acid (5 mL) was heated to 60 ◦C for 5 h, then allowed to
cool, concentrated in vacuo, then diluted with water (20 mL)
and extracted with ethyl acetate (3 × 20 mL). The combined
organic layers were dried (Na2SO4) and concentrated in vacuo.
Chromatography (silica; 30% ethyl acetate, petrol) gave 6a as a
pale brown solid (0.06 g, 91%) mp 102–105 ◦C. UV kmax (EtOH):
276, 205 nm. tmax/cm−1: 3341, 3221, 3070, 2966, 2823, 1520, 1496,
1219. dH (300 MHz, CDCl3): 0.96–1.19 (5H, m, C6H11), 1.57–1.68
(6H, m, C6H11), 3.66 (3H, s, OCH3), 3.93 (2 H, d, J = 6.3 Hz),
4.84 (2H, br, NH2), 5.19 (1H, s, CH), 6.72 (2H, d, J = 9.3 Hz),
7.38 (2H, d, J = 9.3 Hz) ppm. dC (75 MHz, CDCl3): 26.1, 26.8,
30.1, 37.8, 55.8, 71.6, 79.2, 114.3, 121.7, 133.7, 155.6, 159.9, 165.3,
171.7 ppm. m/z (ESI+) 329.28 [M + H]+. HRMS (EI) m/z calcd
for C18H24N4O2: 329.1972 [M + H]+; found 329.1973 [M + H]+.
6-Chloro-N4,N4-bis(4-methoxybenzyl)-N2-(4-
methoxyphenyl)pyrimidine-2,4-diamine (4)
A mixture of 3a (1.2 g, 2.9 mmol), p-anisidine (0.44 g, 3.6 mmol),
anhydrous triethylamine (0.50 mL, 3.6 mmol), n-butanol (8 mL)
and anhydrous DMSO (2 mL) was heated to 95 ◦C for 3 d, then
allowed to cool and concentrated in vacuo. Water (50 mL) was
added and the mixture was extracted with ethyl acetate (3 ×
50 mL). The combined organic extracts were dried (NaSO4) and
concentrated in vacuo. Chromatography (silica; 30% ethyl acetate,
petrol) gave 4 as a red solid (0.43 g, 30%) mp 142–145 ◦C.
tmax/cm−1: 3263, 3110, 2954-2930, 2831, 1605, 1553, 1500, 1224.
kmax (EtOH): 274, 227 nm. dH (300 MHz, CDCl3): 3.66 (6H, s,
2 × OCH3), 3.69 (3H, s, OCH3), 4.52 (4H, br, 2 × N–CH2–), 5.89
(1H, s, CH), 6.66 (2H, d, J = 8.9 Hz), 6. 76 (4H, d, J = 8.6
Hz), 7.01 (4H, d, J = 8.6 Hz), 7.28 (2H, d, J = 8.9 Hz) ppm.
dC (75 MHz, CDCl3): 50.9 (N–CH2), 55.6 (OCH3), 55.8(OCH3),
93.2, 114.5, 114.7, 122.4, 128.8, 129.3, 133.1, 156.0, 159.6, 159.8,
6-(Cyclohexylmethoxy)-N2-(4-methoxyphenyl)-5-
nitrosopyrimidine-2,4-diamine (7a)
160.5, 164.4 ppm. m/z (ESI+) 491.24 [M + H]+ HRMS (EI) m/z
.
To a solution of 6a (0.05 g, 0.15 mmol) in 30% acetic acid and water
(5 mL) at 80 ◦C was added sodium nitrite (0.014 g, 0.2 mmol) in
water (0.2 mL) giving a brown precipitate. Heating was continued
for 2 h then the mixture was allowed to cool to room temperature,
and concentrated in vacuo. The residues were dissolved in ethyl
acetate (40 mL) and washed with Na2CO3 solution (3 × 20 mL)
and water (2 × 20 mL). The combined organic layers were dried
(Na2SO4) and concentrated in vacuo. Chromatography (silica; 5%
methanol, ethyl acetate) followed by HPLC (C18, acetonitrile,
water) gave 7a as a dark green solid (0.044 g, 26%) mp 168–
171 ◦C. tmax/cm−1: 3288, 3070, 2923, 2851, 1557, 1496, 1446, 1240.
kmax (EtOH): 368, 292, 244 nm. dH (300 MHz, d6-acetone) 0.74–
1.79 (11H, m, C6H11), 3.67 (3H, s, OCH3), 4.24 (2H, s, OCH2),
6.76 (2H, br s, ArH), 7.32 (1H, br s, D2O ex, NH), 7.66(2H, br s,
ArH), 9.07 (1H, s, D2O ex, NH), 10.33 (1H, s, D2O ex, NH). m/z
(ESI+) = 358 [M + H]+. dC (75 MHz, DMSO): 25.4, 26.3, 29.5,
37.2, 55.7, 72.3, 114.2, 123.5, 131.9, 140.4, 150.3, 156.5, 160.2,
171.6 ppm. m/z (ESI+) 358.26 [M + H]+. HRMS (ESI+) m/z calcd
for C18H23N5O3: 358.1874 [M + H]+; found 358.1878 [M + H]+.
Calcd for C27H17ClN4O3: 491.1844 [M + H]+. Found 491.1841 [M
+ H]+. C27H27ClN4O3 requires C, 66.05; H, 5.54; N, 11.41; found
C, 65.83; H, 5.57; N, 11.34%.
N4,N4-bis(4-methoxybenzyl)-N2,N6-bis(4-
methoxyphenyl)pyrimidine-2,4,6-triamine
◦
(0.64 g, 45%) mp 130–133 C. tmax/cm−1: 3330 (NH), 3132, 2992
=
=
(CH arom), 2897 (CH2), 2835 (OCH), 1579, 1537 (C C, C N),
1502 (NR3), 1230 (CH30). kmax (EtOH): 275, 227 nm. dH (300 MHz,
CDCl3): 3.60 (3H, s, OCH3), 3.63(3H, s, OCH3), 3.65 (6H, s, 2 ×
OCH3), 4.46 (4H, br, 2 × N–CH2–), 5.13 (1H, s, CH), 6.60–6.66
(4H, dd, J = 9.1. Hz), 6. 71 (4H, d, J = 8.6 Hz), 6,85 (2H, d, J =
8.9), 6.98 (4H, d, J = 8.6 Hz), 7.28 (2H, d, J = 9.0 Hz) ppm. dC
(75 MHz, CDCl3): 50.7 (N–CH2), 55.7, 55.8, 55.9 (OCH3), 75.9,
114.4, 114.5, 114.9, 121.8, 124.9, 128.9, 130.7, 132.9, 134.3, 155.3,
156.9, 159.3, 159.9, 162.8, 164.3 ppm. m/z (ESI+) 578.34 [M +
H]+.
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C18H23N5O3 requires C, 60.49; H, 6.49; N, 19.59; found C, 60.87;
H, 6.49, N, 18.95%
t, J = 7 Hz, CH3), 1.15–1.18 (5H, m, C6H11), 1.41 (2H, q, J = 7,
15 Hz, CH3CH2CH2), 1.66–1.79 (8H, m, C6H11 + CH3CH2CH2),
3.32–3.38 (2H, m, SO2CH2), 4.05 (2H, d, J = 6 Hz, OCH2),
5.48 (2H, br s, NH2, exchangeable with D2O), 5.75 (1H, s, H5)
ppm; dC (75 MHz, CDCl3) 14.0 (CH3), 22.2 (CH3CH2), 24.5
(CH3CH2CH2), 26.7 (C6H11), 27.0 (C6H11), 30.1 (C6H11), 37.7
(C6H11), 51.1 (CH2SO2), 73.0 (OCH2), 89.1 (C5), 164.7 (C2), 165.5
(C6), 171.2 (C4). m/z (ESI+) = 328 [M + H]+. C15H25N3O3S
requires C, 55.02; H, 7.70; N, 12.83; found C, 54.88; H, 7.71;
N, 12.63%.
6-Amino-2-n-butylsulfanyl-H3-pyrimidin-4-one (8)
6-Amino-2-mercaptopyrimidin-4-ol monohydrate (5.0 g,
31 mmol) was slurried in EtOH (30 mL) at 50 ◦C, and treated
with NaOH (3.25 M, 10 mL, 32.1 mmol) and the mixture stirred
for 30 min. 1-Bromobutane (3.45 mL, 32.1 mmol) was added
dropwise to the slurry and stirring continued for 18 h. Water
(10 mL) was added and the mixture stirred for 30 min. After
cooling to room temperature, the mixture was concentrated in
General Procedure A
vacuo giving 8 as an off-white solid (5.70 g, 92%): mp 183–186 ◦C,
◦
lit. 175 C36; mmax/cm−1 1570, (C N), 1601 (C C), 2858–2928
(CH3, CH2), 3271, 3464 (OH, NH2). dH (300 MHz, d6-DMSO)
0.89 (3H, t, J = 7 Hz, CH3), 1.31–1.43 (2H, m, CH3CH2),
1.53–1.63 (2H, m, CH3CH2CH2), 3.06 (2H, t, J = 7 Hz, SCH2),
4.87 (1H, s, H5), 6.43 (2H, br s, NH2, exchangeable with D2O);
dC (125 MHz, d6-DMSO) 13.5 (CH3), 21.3 (CH3CH2), 29.0
(CH3CH2CH2CH2S), 31.0 (CH3CH2CH2CH2S), 81.1 (C5), 163.5
(C6). m/z (ESI+) = 200 [M + H]+.
To a solution of 10 (0.20 g, 0.61 mmol) and the appropriate aniline
(2 mol. eq.) in TFE (4 mL) was added TFA (0.24 mL, 3.05 mmol).
The mixture was stirred for 10 min at room temperature, then
heated under reflux for a further 2 h, and concentrated in
vacuo yielding a white solid. The solid was extracted into ethyl
acetate (2 × 20 mL). The combined extracts were washed with
copious amounts of water (100 mL), then dried (Na2SO4), and
concentrated in vacuo.
=
=
4-(6-Amino-4-cyclohexylmethoxypyrimidin-2-ylamino)-
benzenesulfonamide (6m)
2-n-Butylsulfanyl-4-cyclohexylmethoxypyrimidin-6-ylamine (9)
To a mixture of 8 (1.50 g, 7.53 mmol), cyclohexylmethanol
(1.39 mL, 11.30 mmol), and PPh3 (2.96 g, 11.30 mmol) in
THF (50 mL) was added DEAD (1.78 mL, 11.30) dropwise
over 20 min at 0 ◦C, and stirring continued for 24 h. The
mixture was concentrated in vacuo yielding a yellow oil which
General Procedure A: 10 (0.30 g, 0.92 mmol), 4-aminobenzene-
sulfonamide (0.32 g, 1.84 mmol), TFE (3 mL), TFA (0.38 mL,
4.60 mmol). HPLC (C18; methanol, water) gave 6m as a white solid
(0.24 g, 69%): mp 177–179 ◦C; mmax/cm−1 1564 (C C, C N str.),
=
=
=
◦
1620 (SO2NH2, NH2 def.), 2853–2925 (CH2), 3104–3216 ( C–H
was stirred in diethyl ether at 0 C, forming a white precipitate,
str.), 3346 (asym + sym N–H str.), 3471 (NH2); kmax = 210 and
296 nm. dH (300 MHz d6-DMSO) 0.98–1.26 (5H, m, C6H11), 1.68–
1.78 (6H, m, C6H11), 4.01 (2H, d, J = 6 Hz, CH2O), 5.29 (1H, s,
H5), 6.43 (2H, s, NH2 exchangeable with D2O), 7.13 (2H, s, NH2
exchangeable with D2O), 7.63 (2H, d, J = 9 Hz, ArH), 7.93 (2H,
d, J = 9 Hz, ArH), 9.34 (NH, exchangeable with D2O) ppm. m/z
(ESI+) = 378 [M + H]+. C17H23N5O3S·0.33CH3OH requires: C,
53.54; H, 6.32; N, 18.04; found: C, 53.50; H, 6.20; N, 18.04%.
which was removed by filtration. The filtrate was collected and
concentrated in vacuo. Chromatography (silica; 20% ethyl acetate,
petrol) followed by recrystallisation (MeOH) gave 9 as a white solid
◦
(1.60 g, 72%): mp 79–82 C; mmax/cm−1 1547, 1583 (C N), 1631
=
=
(C C), 2850–3156 (CH3, CH2), 3294–3425 (NH2). dH (200 MHz,
d6-DMSO) 1.08 (3H, t, J = 7 Hz, CH3), 1.22–1.62 (9H, m, C6H11
+
CH3CH2CH2), (6H, m, C6H11), 3.12 (2H, t, J = 7 Hz, SCH2), 4.18
(2H, d, J = 6 Hz, OCH2), 5.57 (1H, s, H5), 6.80 (2H, br s, NH2,
exchangeable with D2O) ppm; dC (50 MHz, d6-DMSO) 13.5 (CH3),
21.5 (CH3CH2), 25.5 (C6H11), 26.3 (C6H11), 29.3 (C6H11), 31.6
(C6H11), 32.1 (CH3CH2CH2CH2S), 36.89 (CH3CH2CH2CH2S),
66.6, 70.3 (OCH2), 81.57 (C5), 165.14 (C2), 168.79 (C6), 169.17
(C4) ppm. m/z (ESI+) = 296 [M + H]+. C15H25N3OS requires: C,
60.98; H, 8.53; N, 14.22; S, 10.85%; found: C, 61.01; H, 8.52; N,
13.85; S, 10.42%.
4-(6-Amino-4-cyclohexylmethoxypyrimidin-2-ylamino)-N-(2-
hydroxyethyl)benzenesulfonamide (6q)
General Procedure A: 9 (0.11 g, 0.33 mmol), amino-N-(2-
hydroxyethyl)benzenesulfonamide (0.14 g, 0.65 mmol) TFE
(3 mL), TFA (0.13 mL, 1.63 mmol). HPLC (C18; methanol, water)
gave 6q as a white solid (0.09 g, 0.22 mmol, 66%). m/z (ESI+) =
422 [M + H]+.
2-(n-Butane-1-sulfonyl)-4-cyclohexylmethoxypyrimidin-6-ylamine
(10)
General Procedure B: Nitrosation
The appropriate pyrimidine was dissolved in aqueous acetic acid
(30%; 3 mL) and the solution was heated to 80 C, then sodium
nitrite (0.02 g, 0.35 mmol) in water (0.2 mL) was added dropwise.
The mixture was stirred for a further 2 h, then extracted into ethyl
acetate (30 mL). The extract was washed with water (30 mL), dried
(Na2SO4) and concentrated in vacuo.
To a stirred solution of 9 (1.0 g, 3.38 mmol) in DCM (20 mL)
was added mCPBA (2.34 g, 13.5 mmol) and stirring continued
for 17 h. The mixture was concentrated in vacuo giving a yellow
solid which was extracted into ethyl acetate (2 × 20 mL). The
combined extracts were washed with saturated sodium sulfite
solution (30 mL) and aqueous NaHCO3 solution (30 mL), then
dried (Na2SO4) and concentrated in vacuo yielding 10 as an off-
white solid (0.99 g, 89%). Recrystallisation (ethyl acetate, petrol)
gave a white solid: mp 141–143 ◦C; mmax/cm−1 1130 (SO2 sym.
◦
4-(6-Amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-
benzenesulfonamide (7m)
=
=
str.), 1300 (SO2 asym. str.) 1595 (C N), 1635 (C C), 2852–3212
(CH3, CH2), 3323, 3424 (NH2). dH (300 MHz, CDCl3) 0.89 (3H,
General Procedure B: 6m (0.08 g, 0.20 mmol). HPLC (C18;
methanol, water) gave 7m as a green solid (0.02 g, 25%): mp
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◦
159–162 C; mmax/cm−1 1528 (N O str.), 1633 (NH2 def.), 2846–
3040 (–CH2–), 3280 (asym + sym N–H str.), 3364 (NH2); kmax
D.J.P.), and the MRC for financial support, and the EPSRC and
CCLRC for funding of the National Crystallography Service and
access to SRS diffraction facilities. We also acknowledge the use of
the EPSRC Mass Spectrometry Service at the University of Wales
(Swansea).
=
=
362 nm. dH (300 MHz d6-DMSO) 1.00–1.23 (5H, m, C6H11), 1.71–
1.88 (6H, m, C6H11), 4.43 (2H, d, J = 6 Hz, CH2O), 7.29 (2H, s,
NH2 exchangeable with D2O), 7.73 (2H, d, J = 8 Hz, ArH), 8.00
(2H, s br, ArH), 8.60 (NH, exchangeable with D2O), 10.25 (1H, s,
NH, exchangeable with D2O), 10.60 (NH, exchangeable with D2O)
ppm. m/z (ESI+) = 407 [M + H]+. C17H22N6O4S·0.5CH3CO2H
requires C, 49.53; H, 5.54; N, 19.25; found: C, 49.44; H, 5.37; N,
19.53%.
References
1 D. O. Morgan, Annu. Rev. Cell Dev. Biol., 1997, 13, 261–291.
2 G. DelSal, M. Loda and M. Pagano, Crit. Rev. Oncog., 1996, 7, 127–
142.
3 C. J. Sherr, Science, 1996, 274, 1672–1677.
4-(6-Amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-
N-(2-hydroxyethyl)benzenesulfonamide (7q)
4 T. M. Sielecki, J. F. Boylan, P. A. Benfield and G. L. Trainor, J. Med.
Chem., 2000, 43, 1–18.
5 G. I. Shapiro, J. Clin. Oncol., 2006, 24, 1770–1783.
6 G. K. Schwartz and M. A. Shah, J. Clin. Oncol., 2005, 23, 9408–9421.
7 J. Dancey and E. A. Sausville, Nat. Rev. Drug Discovery, 2003, 2, 296–
313.
8 K. L. Sayle, J. Bentley, F. T. Boyle, A. H. Calvert, Y. Z. Cheng, N. J.
Curtin, J. A. Endicott, B. T. Golding, I. R. Hardcastle, P. Jewsbury, V.
Mesguiche, D. R. Newell, M. E. M. Noble, R. J. Parsons, D. J. Pratt,
L. Z. Wang and R. J. Griffin, Bioorg. Med. Chem. Lett., 2003, 13,
3079–3082.
9 R. H. Lin, P. J. Connolly, S. L. Huang, S. K. Wetter, Y. H. Lu, W. V.
Murray, S. L. Emanuel, R. H. Gruninger, A. R. Fuentes-Pesquera,
C. A. Rugg, S. A. Middleton and L. K. Jolliffe, J. Med. Chem., 2005,
48, 4208–4211.
10 P. Pevarello, M. G. Brasca, P. Orsini, G. Traquandi, A. Longo, M. Nesi,
F. Orzi, C. Piutti, P. Sansonna, M. Varasi, A. Cameron, A. Vulpetti, F.
Roletto, R. Alzani, M. Ciomei, C. Albanese, W. Pastori, A. Marsiglio,
E. Pesenti, F. Fiorentini, J. R. Bischoff and C. Mercurio, J. Med. Chem.,
2005, 48, 2944–2956.
11 R. H. Lin, Y. H. Lu, S. K. Wetter, P. J. Connolly, I. J. Turchi, W. V.
Murray, S. L. Emanuel, R. H. Gruninger, A. R. Fuentes-Pesquera,
M. Adams, N. Pandey, S. Moreno-Mazza, S. A. Middleton and L. K.
Jolliffe, Bioorg. Med. Chem. Lett., 2005, 15, 2221–2224.
12 C. E. Arris, F. T. Boyle, A. H. Calvert, N. J. Curtin, J. A. Endicott,
E. F. Garman, A. E. Gibson, B. T. Golding, S. Grant, R. J. Griffin,
P. Jewsbury, L. N. Johnson, A. M. Lawrie, D. R. Newell, M. E. M.
Noble, E. A. Sausville, R. Schultz and W. Yu, J. Med. Chem., 2000, 43,
2797–2804.
General Procedure B: 6q (0.09 g, 0.22 mmol). Recrystallisation
(MeOH) gave 7q as a green solid: mp 193–195 ◦C; mmax/cm−1
=
=
=
1522 (N O str.), 1576 (C N, C C), 2852–2926 (–CH2–), 3100–
3267 (NH2, OH); kmax = 362, 263, 239 and 208 nm. dH (300 MHz
d6-DMSO) 1.05–1.30 (5H, m, C6H11), 1.50–1.88 (6H, m, C6H11),
2.78 (2H, q, J = 6 Hz, NHCH2), 3.36 (2H, t, CH2OH), 4.39
(2H, d, J = 6 Hz, CH2O), 4.68 (1H, t, OH exchangeable with
D2O), 7.40 (1H, t, NHCH2 exchangeable with D2O), 7.71 (2H,
d, J = 8 Hz, ArH), 7.97 (2H, d, J = 8 Hz, ArH) 8.50 (1H, s,
NH exchangeable with D2O) ppm. m/z (ESI+) = 451 [M + H]+.
C19H26N6O5S·0.5CH3CO2H requires C, 49.99; H, 5.87; N, 17.49;
found: C, 49.67; H, 5.26; N, 17.60%.
Biological Evaluation
Compounds were assayed for the inhibition of human cyclin-
dependent kinases 1 and 2, as described previously.12 The final
ATP concentration within the assay was 12.5 lM.
X-Ray Crystallography†
13 Y. T. Chang, N. S. Gray, G. R. Rosania, D. P. Sutherlin, S. Kwon, T. C.
Norman, R. Sarohia, M. Leost, L. Meijer and P. G. Schultz, Chem.
Biol., 1999, 6, 361–375.
14 P. Imbach, H. G. Capraro, P. Furet, H. Mett, T. Meyer and J.
Zimmermann, Bioorg. Med. Chem. Lett., 2000, 10, 1001–1001.
15 M. Legraverend, P. Tunnah, M. Noble, P. Ducrot, O. Ludwig, D. S.
Grierson, M. Leost, L. Meijer and J. Endicott, J. Med. Chem., 2000,
43, 1282–1292.
16 G. H. Kuo, A. DeAngelis, S. Emanuel, A. H. Wang, Y. Zhang, P. J.
Connolly, X. Chen, R. H. Gruninger, C. Rugg, A. Fuentes-Pesquera,
S. A. Middleton, L. Jolliffe and W. V. Murray, J. Med. Chem., 2005, 48,
4535–4546.
17 P. Pevarello, D. Fancelli, A. Vulpetti, R. Amici, M. Villa, V. Pittala,
P. Vianello, A. Cameron, M. Ciomei, C. Mercurio, J. R. Bischoff, F.
Roletto, M. Varasi and M. G. Brasca, Bioorg. Med. Chem. Lett., 2006,
16, 1084–1090.
18 M. F. Brana, M. Cacho, M. L. Garcia, E. P. Mayoral, B. Lopez, B. de
Pascual-Teresa, A. Ramos, N. Acero, F. Llinares, D. Munoz-Mingarro,
O. Lozach and L. Meijer, J. Med. Chem., 2005, 48, 6843–6854.
19 C. M. Richardson, D. S. Williamson, M. J. Parratt, J. Borgognoni,
A. D. Cansfield, P. Dokurno, G. L. Francis, R. Howes, J. D. Moore,
J. B. Murray, A. Robertson, A. E. Surgenor and C. J. Torrance, Bioorg.
Med. Chem. Lett., 2006, 16, 1353–1357.
Crystals of 3a and 4a were small and weakly diffracting, and
data were collected at 120 K with synchrotron radiation (k =
˚
0.8462 A) at station 16.2SMX of the Synchrotron Radiation
Source at Daresbury Laboratory, through the EPSRC National
Crystallography Service. Crystal data for 3a: C20H19Cl2N3O2, Mr =
404.3, monoclinic, space group P21/c, a = 21.9143(10), b =
◦
˚
10.1032(5), c = 8.7088(4) A, b = 98.099(1) , U = 1908.94(16)
3
−1
˚
A , T = 120(2) K, Z = 4, l = 0.36 mm , 13 035 data measured,
3886 unique (Rint = 0.029), 246 refined parameters, R (F, F2
>
2r) = 0.038, Rw (F2, all data) = 0.098, S = 1.03, final difference
−3
˚
map within
0.29 e A . Crystal data for 4a: C27H27ClN4O3,
Mr = 491.0, monoclinic, space group C2/c, a = 16.9620(14), b =
◦
3
˚
˚
10.7877(9), c = 27.228(2) A, b = 98.375(1) , U = 4929.0(7) A ,
T = 120(2) K, Z = 8, l = 0.19 mm−1, 15 124 data measured, 5026
unique (Rint = 0.042), 323 refined parameters, R (F, F2 > 2r) =
0.045, Rw (F2, all data) = 0.117, S = 1.06, final difference map
−3
˚
within 0.31 e A .
20 D. S. Williamson, M. J. Parratt, J. F. Bower, J. D. Moore, C. M.
Richardson, P. Dokurno, A. D. Cansfield, G. L. Francis, R. J. Hebdon,
R. Howes, P. S. Jackson, A. M. Lockie, J. B. Murray, C. L. Nunns, J.
Powles, A. Robertson, A. E. Surgenor and C. J. Torrance, Bioorg. Med.
Chem. Lett., 2005, 15, 863–867.
Acknowledgements
The authors thank Cancer Research UK, AstraZeneca, the
EPSRC (Studentship to K.L.S.), the BBSRC (Studentship to
21 R. D’Alessio, A. Bargiotti, S. Metz, M. G. Brasca, A. Cameron, A.
Ermoli, A. Marsiglio, P. Polucci, F. Roletto, M. Tibolla, M. L. Vazquez,
A. Vulpetti and P. Pevarello, Bioorg. Med. Chem. Lett., 2005, 15, 1315–
1319.
† CCDC reference numbers 639379 and 639380. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/b703241b
1584 | Org. Biomol. Chem., 2007, 5, 1577–1585
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View Article Online
22 C. Hamdouchi, B. Zhong, J. Mendoza, E. Collins, C. Jaramillo, J. E.
De Diego, D. Robertson, C. D. Spencer, B. D. Anderson, S. A. Watkins,
F. M. Zhang and H. B. Brooks, Bioorg. Med. Chem. Lett., 2005, 15,
1943–1947.
23 O. Tetsu and F. McCormick, Cancer Cell, 2003, 3, 233–245.
24 J. Du, H. R. Widlund, M. A. Horstmann, S. Ramaswamy, K. Ross,
W. E. Huber, E. K. Nishimura, T. R. Golub and D. E. Fisher, Cancer
Cell, 2004, 6, 565–576.
30 P. M. Fischer and A. Gianella-Borradori, Expert Opin. Invest. Drugs,
2003, 12, 955–970.
31 T. G. Davies, J. Bentley, C. E. Arris, F. T. Boyle, N. J. Curtin, J. A.
Endicott, A. E. Gibson, B. T. Golding, R. J. Griffin, I. R. Hardcastle, P.
Jewsbury, L. N. Johnson, V. Mesguiche, D. R. Newell, M. E. M. Noble,
J. A. Tucker, L. Wang and H. J. Whitfield, Nat. Struct. Biol., 2002, 9,
745–749.
32 I. R. Hardcastle, C. E. Arris, J. Bentley, F. T. Boyle, Y. H. Chen, N. J.
Curtin, J. A. Endicott, A. E. Gibson, B. T. Golding, R. J. Griffin, P.
Jewsbury, J. Menyerol, V. Mesguiche, D. R. Newell, M. E. M. Noble,
D. J. Pratt, L. Z. Wang and H. J. Whitfield, J. Med. Chem., 2004, 47,
3710–3722.
33 H. J. Whitfield, R. J. Griffin, I. R. Hardcastle, A. Henderson, J.
Meneyrol, V. Mesguiche, K. L. Sayle and B. T. Golding, Chem.
Commun., 2003, 2802–2803.
34 V. Mesguiche, R. J. Parsons, C. E. Arris, J. Bentley, F. T. Boyle, N. J.
Curtin, T. G. Davies, J. A. Endicott, A. E. Gibson, B. T. Golding, R. J.
Griffin, P. Jewsbury, L. N. Johnson, D. R. Newell, M. E. M. Noble,
L. Z. Wang and I. R. Hardcastle, Bioorg. Med. Chem. Lett., 2003, 13,
217–222.
35 R. J. Griffin, A. Henderson, N. J. Curtin, A. Echalier, J. A. Endicott,
I. R. Hardcastle, D. R. Newell, M. E. M. Noble, L. Z. Wang and B.T.
Golding, J. Am. Chem. Soc., 2006, 128, 6012–6013.
25 C. Berthet, E. Aleem, V. Coppola, L. Tessarollo and P. Kaldis, Curr.
Biol., 2003, 13, 1775–1785.
26 S. Ortega, I. Prieto, J. Odajima, A. Mart´ın, P. Dubus, R. Sotillo, J. L.
Barbero, M. Malumbres and M. Barbacid, Nat. Genet., 2003, 35, 25–31.
27 S. J. McClue, D. Blake, R. Clarke, A. Cowan, L. Cummings, P. M.
Fischer, M. MacKenzie, J. Melville, K. Stewart, S. D. Wang, N. Zhelev,
D. Zheleva and D. P. Lane, Int. J. Cancer, 2002, 102, 463–468.
28 R. N. Misra, H. Y. Xiao, K. S. Kim, S. F. Lu, W. C. Han, S. A. Barbosa,
J. T. Hunt, D. B. Rawlins, W. F. Shan, S. Z. Ahmed, L. G. Qian, B. C.
Chen, R. L. Zhao, M. S. Bednarz, K. A. Kellar, J. G. Mulheron, R.
Batorsky, U. Roongta, A. Kamath, P. Marathe, S. A. Ranadive, J. S.
Sack, J. S. Tokarski, N. P. Pavletich, F. Y. F. Lee, K. R. Webster and
S. D. Kimball, J. Med. Chem., 2004, 47, 1719–1728.
29 X. J. Chu, W. DePinto, D. Bartkovitz, S. S. So, B. T. Vu, K. Packman,
C. Lukacs, Q. J. Ding, N. Jiang, K. Wang, P. Goelzer, X. F. Yin, M. A.
Smith, B. X. Higgins, Y. S. Chen, Q. Xiang, J. Moliterni, G. Kaplan, B.
Graves, A. Lovey and N. Fotouhi, J. Med. Chem., 2006, 49, 6549–6560.
36 G. Biagi, A. Costantini, L. Costantino, I. Giorgi, O. Livi, P. Pecorari,
M. Rinaldi and V. Scartoni, J. Med. Chem., 1996, 39, 2529–2535.
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