Investigation of a novel molecular descriptor for the lead optimization of 4-aminoquinazolines as vascular endothelial growth factor receptor-2 inhibitors: Application for quantitative structure-activity relationship analysis in lead optimization

Article abstract of DOI:10.1016/j.bmcl.2011.01.037

We investigated the use of infrared vibrational frequency of ligands as a potential novel molecular descriptor in three different molecular target and chemical series. The vibrational energy of a ligand was approximated from the sum of infrared (IR) absor

Full text of DOI:10.1016/j.bmcl.2011.01.037

Bioorganic & Medicinal Chemistry Letters 21 (2011) 1371–1375
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Investigation of a novel molecular descriptor for the lead optimization
of 4-aminoquinazolines as vascular endothelial growth factor
receptor-2 inhibitors: Application for quantitative structure–activity
relationship analysis in lead optimization
Joel K. Kawakami a, , Yannica Martinez a, Brandi Sasaki a, Melissa Harris a, Wendy E. Kurata b, Alan F. Lau b
⇑
a Chaminade University of Honolulu, Department of Natural Sciences and Mathematics, Honolulu, HI 96816, USA
b Cancer Research Center, University of Hawai0i at Manoa, Honolulu, HI 96813, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
We investigated the use of infrared vibrational frequency of ligands as a potential novel molecular
descriptor in three different molecular target and chemical series. The vibrational energy of a ligand
was approximated from the sum of infrared (IR) absorptions of each functional group within a molecule
and normalized by its molecular weight (MDIR). Calculations were performed on a set of 4-aminoquinaz-
olines with similar docking scores for the VEGFR2/KDR receptor. 4-Aminoquinazolines with MDIR values
ranging 192–196 provided compounds with KDR inhibitory activity. The correlation of KDR inhibitory
activity was similarly observed in a separate chemical series, the pyrazolo[1,5-a]pyrimidines. Initial
exploration of this molecular descriptor supports a tool for rapid lead optimization in the 4-aminoquinaz-
oline chemical series and a potential method for scaffold hopping in pursuit of new inhibitors.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 28 October 2010
Revised 8 January 2011
Accepted 11 January 2011
Available online 14 January 2011
Keywords:
4-Anilinoquinazoline
KDR
VEGFR-2
Molecular descriptor
Infrared
The lead optimization of a compound for improved binding and/
or inhibitory potency remains a time consuming and challenging
stage in drug discovery research. Computational chemistry pro-
vides a potential solution for rapid quantitative structure to activ-
ity relationship (QSAR) analysis to allow the efficient design of next
generation analogs with improved biological activity. Molecular
descriptors play a pivotal role in computational chemistry for the
computational lead optimization of a chemical series. Infrared
(IR) vibrations of molecules have received little attention as a
molecular descriptor for QSAR analysis. Previous report utilized
quantum mechanical IR values for QSAR providing predictive capa-
bility comparable to CoMFA.1 We investigated the vibrational en-
ergy of a ligand as a potential intermolecular force contributing
to the binding interaction with biomolecules.
The initial QSAR study employed known classical cannabinoids
with highly potent and reproducible binding affinities at the can-
nabinoid receptor 1 (CB1).2a A small subset of the compounds
within the set was chosen based on uniform distribution of binding
affinity. The average IR bond frequencies for each functional group
within a molecule were summed and normalized by dividing with
correlation was observed between the negative log of binding
affinities (pKi) and the sum of all average IR bond frequencies
divided by the molecular weight of the compound (MDIR). The plot
of this molecular descriptor, MDIR, against pKi is shown in Figure 1.
The binding affinity maximizes with MDIR value of 224 for
compound 4. None of the other IR normalized set of values showed
an observable correlation other than molecular weight.
The correlation of MDIR to binding affinities employing alkyl
homologation was investigated in a reported SAR of pyrazol-
o[3,4-d]pyrimidines as adenosine deaminase (ADA) inhibitors.2b
The expected trend of increasing activity upon homologation and
maximizing as seen for compounds 8e and 8f when n = 7 and 8,
respectively (Fig. 2), is observed. Based on the homologation SAR,
ideal binding affinities are obtained for MDIR values above 250
and lower than 266. Two other compounds (9a and 9b) with addi-
tional structural modifications and containing MDIR values in the
ideal range were identified and correlated to be active. The corre-
lation of all MDIR values for compounds in Figure 2 to ADA binding
affinities resemble a parabolic type relationship. However, the
abrupt loss of binding affinity in going from MDIR = 261.4–265.6
(compounds 8f and 8g, respectively) is surprising. The reported
study correlated binding modes via docking studies which showed
8g lacking the ideal binding mode in their docking model. Thus, the
use of docking methods coupled with MDIR may prove to be a
useful modality for QSAR studies.
a
known molecular descriptor (i.e., rotatable bonds, H-bond
donors, molecular weight, and heavy atoms). A quadratic type of
⇑
Corresponding author.
E-mail address: jkawakam@chaminade.edu (J.K. Kawakami).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.01.037

1372
J. K. Kawakami et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1371–1375
OH
OH
OH
O
O
O
Br
Br
I
1
2
4
OH
Br
O
3
5
Compound
Ki(uM)
MDIR
pKi
OH
OH
1
2
3
4
5
6
7
0.328
0.024
0.008
0.0004
0.0013
0.025
0.103
200
212
216
224
230
232
258
0.484
1.620
2.097
3.398
2.886
1.602
0.987
F
F
O
O
Br
6
F
F
OH
O
7
Figure 1. MDIR as a molecular descriptor for QSAR of classical cannabinoids.
NH2
N
N
Compound
n__
MDIR
Ki (nM)
N
n
N
8a - g, n = 3 - 9
8a
8b
8c
8d
8e
8f
8g
9a
9b
3
4
5
6
7
8
9
na
na
239.1
244.7
249.5
253.9
257.8
261.4
265.6
254.9
251.0
> 1,000
818
530
NH2
OH
8
N
N
N
0.13
0.47
> 1,000
0.28
53
N
N
NH2
9a
N
N
N
HO
9b
Figure 2. MDIR and binding affinities of adenosine deaminase inhibitors.
We next applied this molecular descriptor within the 4-anilino-
quinazoline chemical series, a series known for its inhibitory
potency at the vascular endothelial growth factor receptor 2
(VEGFR2/KDR) tyrosine kinase receptor.3 In order to isolate the
contribution of MDIR in QSAR, several 4-anilinoquinazoline
compounds were virtually designed and docked at the human
KDR receptor. A subset of these compounds was further selected
based on similar Flexible Grid Docking score relative to the original
ligand present in the Apo crystal structure, 3-(2-aminoquinazolin-
6-yl)-4-methyl-1-[3-(trifluoromethyl) phenyl]pyridine-2(1H)-one.
MDIR values were then calculated and a final subset of compounds
chosen for synthesis and biological evaluation.
The docking score utilized the flexible docking method allowing
flexibility to both the ligand and receptor. The docking score pre-
sented is an approximation of the binding energies based on van
der Waal’s interactions and coulombic electrostatic energies. The
Apo structure of human KDR receptor was obtained from the Pro-
tein Data Bank (PDB No. 3CPC)5 with an X-ray diffraction resolu-
0
tion of 2.40 ÅA. The receptor and ligand were separately prepared
for docking. Branch A of the dimeric receptor was isolated and
prepared for docking by the addition of hydrogens and partial
charges using Chimera. Structure of designed ligands were drawn
with ChemDraw 3D and minimized using Chimera and the dot
molecular surface (DMS) write tools. The ligand was saved as a
Mol2 format after adding hydrogens and formal charges. The
molecular surface and Spheres were generated using DMS and
The docking was performed with the open source DOCK 6
suite of programs4 by University of California, San Francisco.

J. K. Kawakami et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1371–1375
1373
Table 1
Briefly, the (4-methoxyphenyl)-acetonitrile is condensed with
dimethylforamidedimethylacetal (DMFDMA) to afford the Aldol
adduct followed by Michael addition/cyclization with hydrazine
hydrochloride. The 3-amino-4-arylpyrazole formed is then
condensed/dehydrated with the corresponding 1,3-dialdehyde to
afford compound 21.12–24
Grid docking score and MDIR correlation to KDR inhibitory activity of 4-aminoqui-
nazolines
R
MeO
N
The KDR ELISA assay was performed using the HTScanÒVEGF
Receptor 2 Kinase Assay Kit from Cell Signaling Technology
but the human N-terminal His6-tagged recombinant enzyme
(aa790-end) was purchased from US Biological for a better dy-
N
MeO
Compound
R
Dock
MDIRb KDR inhibitionc
(%)
scorea
10
11
12
40-Chloro-anilino
30,40-Difluoro-anilino
30-Chloro-40-methyl-
anilino
40-Fluoro-anilino
30-Fluoro-40-methyl-
anilino
ꢀ27.8 172
ꢀ24.9 178
ꢀ25.0 180
4
5
9
namic range in the assay. DELPHIA 200 lL Streptavidin clear
coated 96-well plates were purchased from Fisher Scientific Inc.
The assay was found to tolerate up to 1% dimethyl sulfoxide
(DMSO) to aid solubility of ligands in the kinase buffer. Final con-
13
14
ꢀ24.8 184
ꢀ27.3 192
6
66
centrations used in the assay were 20
lM ATP, 100 ng human VEG-
FR2 kinase and 1.5 M substrate peptide. The absorbance of the
l
15
16
17
18
19
Anilino
Ethoxyl
Isopropoxyl
ꢀ25.1 194
ꢀ25.7 200
ꢀ25.5 207
ꢀ26.3 215
ꢀ26.0 234
19
0
2
13
17
wells was read at 450 nm on the xMark™ microplate spectropho-
tometer by BIO-RAD. Each assay contained a blank, control, DMSO
control, and standard (Ki 8751). The average percent inhibitions are
calculated from n of 3 data (unless specified otherwise) and as-
sayed on separate days.
The KDR assay from Cell Signaling (HTSscan Kit) provided a
highly reproducible assay. It also provided an enzymatic in vitro
assay with potency similarity to typical cellular potency, where
increase ATP concentration in cells often provides much lower po-
tency or high IC50 values. The assay was calibrated to an internal
standard, a known KDR inhibitor (Ki 8751)7 with a reported IC50 va-
Isopropyl amine
Cyclohexyl amine
a
b
c
Grid scoring from Flexible docking (kcal/mol).
amu/cm.
Percent inhibition (average taken from n of 3 performed on separate days) KDR
ELISA assay (20
l
M ATP) at 10
l
M final compound concentration.
0
SPHGEN, respectively. A distance of 10 ÅA was specified from the
location of the original co-crystallized ligand as the binding site.
0
lue of 0.9 nM (final ATP concentration was 2 lM) and stauro-
The Grid Box was then generated adding an extra 5 ÅA around the
sphere. Docking was performed within the Grid Box with the
bump filter on and set to 0.75. A flexible docking method was
used for both the ligands and receptor and Grid Docking score6
calculated in kcal/mol.
sporine. The reported KDR IC50 value for Staurosporine using the
HTSscan kit from Cell Signalling is 250 nM. The IC50 values ob-
tained in our assay for Ki 8751 and staurosporine were measured
to be 0.8 lM and 250 nM, respectively.
The final subset of compounds was chosen based on a set of
MDIR values that uniformly ranged from 170 to 235 and similar
grid docking scores (Table 1). These ten compounds were synthe-
sized and evaluated in the KDR ELISA assay as described above.
Compounds 10–19 were synthesized via the chloride displace-
ment of 4-chloro-6,7-dimethoxyquinazolines with the appropriate
amine or alcohol. Compound 21 was synthesized from the corre-
sponding (4-methoxyphenyl)-acetonitrile in a three step fashion.
Table 2
Grid Docking score and MDIR correlation to KDR inhibitory activity
Compound
Dock scorea
MDIRb
172
Reported KDR inhibition10
IC50 = 800 nM
Measuredc KDR inhibition
MeO
HN
N
Cl
MeO
ꢀ27.8
4% @ 10 lM (n = 2)
10
14
N
N
MeO
MeO
HN
N
Me
ꢀ27.3
192
NR
66% @ 10
lM (n = 2)
F
F
HN
ꢀ33.9
ꢀ29.6
192
199
IC50 = 2 nM
37% @ 20
46% @ 25
l
M (n = 2)
O
N
OH
Ph
20
N
N
N
MeO
IC50 = 19 nM
l
M (n = 2)
N
21
S
a
b
c
Grid scoring from Flexible Docking (kcal/mol).
amu/cm.
Percent inhibition KDR ELISA assay (20 lM ATP) with HTSscan.

1374
J. K. Kawakami et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1371–1375
11. Matter, H. J. Peptide Res. 1998, 52, 305.
12. Calculation of MDIR for compound 2 as a representative example:
The most potent of these compounds contain an MDIR value of
192 (compound 14) while other compounds were either inactive
(KDR percent inhibition less than 15%) or marginally active. The
IC50 evaluation of compound 14 was difficult due to solubility
problems at higher concentrations. A five point inhibition curve
Compound 2
Qty
IR
Sub total
Functional group
provided an IC50 = 2.5 lM for compound 14.
–C–H
@C–C–
–C@C–
–C@N–
@N–H
–C@N–
@C–H
–C–C–
23
8
4
0
0
0
3
9
1
1
0
0
2
0
0
0
0
0
1
1480
1680
1680
1810
1600
1810
1000
1680
1150
3600
1820
1600
1300
1360
800
34,040
13,440
6720
0
0
0
3000
15,120
1150
3600
0
0
2600
0
0
0
0
0
600
80,270
211.6099
Additional compounds with reported KDR inhibitory activity,
similar Flexible grid dock scores, and MDIR values in close prox-
imity to 192 were identified and evaluated (Table 2). Of these four
compounds, all are known inhibitors of KDR except for compound
14. In spite of good docking scores, compound 10 with a non-ideal
MDIR value (172) is a known KDR inhibitor but with weak activ-
ity8 and relatively inactive in our assays. Compound 208 represent
a fairly large structural modification towards enhanced water sol-
ubility relative to the 4-aminoquinazolines studied herein. In spite
of these major structural modifications, the ideal dock score (ꢀ27
to ꢀ34 kcal/mol) and MDIR value (192) correlated with a potent
KDR inhibition. Within the pyrazolo[1,5-a]pyrimidine series, we
identified one compound with a dock score and MDIR value with-
in our desired range. Compound 219 was active in our KDR assay
and also a reported potent KDR inhibitor. The latter example illus-
trates MDIR as a potential molecular descriptor tool for scaffold
hopping (design of a different chemotype). Ki 8751 was not in-
cluded in our exploration of MDIR as related to KDR inhibitory
activity due to its failure to dock within our designated binding
pocket.
C–O–alcohol
–O–H
–C@O
–N–H
–C–O–ether
–C–N–alkyl
c-Cl
C–F
–CN
@C–N–
–C–Br
Sum of IR absorptions
Molecular weight
1400
2260
1360
600
379.33
MDIR
In summary, the preliminary study of MDIR as a molecular
descriptor in QSAR is supportive. Thus, further studies are war-
ranted for the validation of MDIR as a molecular descriptor using
the method employed by Matter.11 The utility of MDIR coupled
with docking methods seems to be amenable for scaffold hopping.
Further examples of scaffold hopping to afford novel and active
chemical series as KDR inhibitors will be required for validation
studies.
13. (4-Chloro-phenyl)-(6,7-dimethoxy-quinazolin-4-yl)-amine
(10):
4-
Aminoquinazolines were prepared according to literature methods10 with a
slight procedural modification. A typical procedure utilized is demonstrated for
compound 10 as a representative example. In a 25 mL seal-tube reaction vessel
equipped with a magnetic stirrer, 100.0 mg (0.445 mmol) of 4-chloro-6,7-
dimethoxy-quinazoline was added followed by 2.0 mL of acetonitrile and
62.5 mg (0.490 mmol) of 4-chloroaniline. The vessel was sealed and heated to
100 °C. After stirring at said temperature for a period of one day, the reaction
was cooled, solvent evaporated via speed-vac, and tritiated three times with
cold acetonitrile. Any remaining solvent was evaporated in vacuo to afford
140 mg (quantitative yield) of 10 as a white crystalline solid. LC–MS: m/
z = 316.0 (M+1, 100% intensity) and 318.0 (M+1, 33% intensity). 1H NMR
(300 MHz, DMSO-d6): d 11.4 (1H, br s), 8.83 (1H, s), 8.33 (1H, s), 7.77 (2H, br d,
J = 9.3 Hz), 7.55 (2H, br d, J = 9.0 Hz), 7.35 (1H, s), 4.02 (3H, s), 4.00 (3H, s).
14. (3,4-Difluoro-phenyl)-(6,7-dimethoxy-quinazolin-4-yl)-amine (11): Following
a similar reaction procedure to 10, 81 mg (57% yield) of 11 was isolated as a
white crystalline solid. LC–MS: m/z = 318.0 (M+1, 100% intensity). 1H NMR
(300 MHz, DMSO-d6): d 11.3 (1H, br s), 8.85 (1H, s), 8.25 (1H, s), 7.96–7.89 (1H,
m), 7.60–7.55 (2H, m), 7.32 (1H, s), 4.01 (3H, s), 4.00 (3H, s).
Acknowledgments
This work was supported by a grant from the Hawai’i Commu-
nity Foundation, Tai Up Yang Fund (Grant ID No. 20080493) and in-
debted to Hawai’i Pacific University for the use of their nuclear
magnetic spectrometer.
15. (3-Chloro-4-methyl-phenyl)-(6,7-dimethoxy-quinazolin-4-yl)-amine(12):
Following a similar reaction procedure to 10, 125 mg (85% yield) of 12 was
isolated as a white crystalline solid. LC–MS: m/z = 330.1 (M+1, 100% intensity)
and 332.1 (M+1, 37% intensity). 1H NMR (300 MHz, DMSO-d6): d 11.3 (1H, br s),
8.85 (1H, s), 8.28 (1H, s), 7.86 (1H, d, J = 1.8 Hz), 7.61 (1H, dd, J = 8.1, 2.4 Hz),
7.46 (1H, d, J = 8.7 Hz), 7.33 (1H, s), 4.02 (3H, s), 4.00 (3H, s), 2.37 (3H, s).
References and notes
1. Turner, D. B.; Willett, P. Eur. J. Med. Chem. 2000, 35, 367.
2. (a) Nikas, S. P.; Grzybowska, J.; Papahatjis, D. P.; Charalambous, A.; Banijamali,
A. R.; Chari, R.; Fan, P.; Kourouli, T.; Lin, S.; Nitowski, A. J.; Marciniak, G.; Guo,
Y.; Li, X.; Wang, C. J.; Makriyannis, A. AAPS J. 2004, 6. article 30; (b) Settimo, F.
D.; Primofiore, G.; Motta, C. L.; Taliani, S.; Simorini, F.; Marini, A. M.; Mugnaini,
L.; Lavecchia, A.; Novellino, E.; Tuscano, D.; Martini, C. J. Med. Chem. 2005, 48,
5162.
3. Plé, P. A.; Green, T. P.; Hennequin, L. F.; Curwen, J.; Fennell, M.; Allen, J.;
Lambert-van der Brempt, C.; Costello, G. J. Med. Chem. 2004, 47, 871.
4. Park, M.-S.; Dessal, A. L.; Smrcka, A. V.; Stern, H. A. J. Chem. Inf. Model 2009, 49,
437.
5. Hu, E.; Tasker, A.; White, R. D.; Kunz, R. K.; Human, J.; Chen, N.; Burli, R.;
Hungate, R.; Novak, P.; Itano, A.; Zhang, X.; Yu, V.; Nguyen, Y.; Tudor, Y.; Plant,
M.; Flynn, S.; Xu, Y.; Meagher, K. L.; Whittington, D. A.; Ng, G. Y. J. Med Chem.
2008, 51, 3065.
6. (a) Shoichet, B. K.; Bodian, D. L.; Kuntz, I. D. J. Comput. Chem. 1992, 13, 380; (b)
Meng, E. C.; Shoichet, B. K.; Kuntz, I. D. J. Comput. Chem. 1992, 13, 505.
7. Kubo, K.; Shimizu, T.; Ohyama, S.-i.; Murooka, H.; Iwai, A.; Nakamura, K.;
Hasegawa, K.; Kobayashi, Y.; Takahashi, N.; Takahashi, K.; Kato, S.; Izawa, T.;
Isoe, T. J. Med. Chem. 2005, 48, 1359.
16. (6,7-Dimethoxy-quinazolin-4-yl)-(4-fluoro-phenyl)-amine (13): Following
a
similar reaction procedure to 10, 141 mg (quantitative yield) of 13 was isolated
as a white crystalline solid. LC–MS: m/z = 300.0 (M+1, 100% intensity). 1H NMR
(300 MHz, DMSO-d6): d 11.3 (1H, br s), 8.80 (1H, s), 8.27 (1H, s), 7.71 (2H, br dd,
J = 9.3, 5.4 Hz), 7.34 (2H, br t, J = 8.7 Hz), 7.33 (1H, s), 4.01 (3H, s), 4.00 (3H, s).
17. (6,7-Dimethoxy-quinazolin-4-yl)-(3-fluoro-4-methyl-phenyl)-amine
(14):
Following a similar reaction procedure to 10, 131 mg (94% yield) of 14 was
isolated as a white crystalline solid. LC–MS: m/z = 314.1 (M+1, 100% intensity).
1H NMR (300 MHz, DMSO-d6): d 11.4 (1H, s), 8.85 (1H, s), 8.32 (1H, s), 7.64 (1H,
dd, J = 11.4, 2.1 Hz), 7.47 (1H, dd, J = 8.4, 1.8 Hz), 7.38 (1H, t, J = 8.7 Hz), 7.34
(1H, s), 4.02 (3H, s), 3.99 (3H, s), 2.27 (3H, d, J = 1.8 Hz).
18. (6,7-Dimethoxy-quinazolin-4-yl)-phenyl-amine (15): Following
a similar
reaction procedure to 10, 131 mg (quantitative yield) of 15 was isolated as a
white crystalline solid. LC–MS: m/z = 282.0 (M+1, 100% intensity). 1H NMR
(300 MHz, DMSO-d6): d 11.4 (1H, br s), 8.80 (1H, s), 8.34 (1H, br d, J = 3.9 Hz),
7.69 (2H, br d, J = 7.2 Hz), 7.50 (1H, br d, J = 7.8 Hz), 7.48 (1H, br d, J = 8.4 Hz),
7.36 (1H, br d, J = 4.8 Hz), 7.32 (1H, br t, J = 7.8 Hz), 4.02 (3H, s), 3.99 (3H, s).
19. 4-Ethoxy-6,7-dimethoxy-quinazoline (16): Following
a similar reaction
8. Whittles, C. E.; Pocock, T. M.; Wedge, S. R.; Kendrew, J.; Hennequin, L. F.;
Harper, S. J.; Bates, D. O. Microcirculation 2002, 9, 513.
9. Fraley, M. E.; Hoffman, W. F.; Rubino, R. S.; Hungate, R. W.; Tebben, A. J.;
Rutledge, R. Z.; McFall, R. C.; Huckle, W. R.; Kendall, R. L.; Coll, K. E.; Thomas, K.
A. Bioorg. Med. Chem. Lett. 2002, 12, 2767.
10. Hennequin, L. F.; Thomas, A. P.; Johnstone, C.; Stokes, E. S. E.; Plé, P. A.;
Lohmann, J-J. M.; Ogilvie, D. J.; Dukes, M.; Wedge, S. R.; Curwen, J. O.; Kendrew,
J.; Lambert-van der Brempt, C. L. J. Med. Chem. 1999, 42, 5369.
procedure to 10, 129 mg (58% yield) of 16 was isolated as a white crystalline
solid. LC–MS: m/z = 235.0 (M+1, 100% intensity). 1H NMR (300 MHz, CDCl3) d
8.85 (1H, s), 7.97 (1H, s), 7.41 (1H, s), 4.83 (2H, q, J = 6.9 Hz), 4.14 (3H, s), 4.07
(3H, s), 1.59 (3H, t, J = 6.9 Hz).
20. 4-Isopropoxy-6,7-dimethoxy-quinazoline (17): Following a similar reaction
procedure to 10, 221 mg (61% yield) of 17 was isolated as a white crystalline
solid. LC–MS: m/z = 249.1 (M+1, 100% intensity). 1H NMR (300 MHz, CDCl3)

J. K. Kawakami et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1371–1375
1375
d 7.98 (1H, s), 7.62 (1H, s), 7.16 (1H, s), 4.07 (1H, heptet, J = 6.9 Hz), 4.02 (3H, s),
4.02 (3H, s), 1.22 (7H, d, J = 6.9 Hz).
3.98 (3H, s), 3.14 (1H, tt, J = 11.0, 3.9 Hz), 2.14–2.10 (2H, m), 1.85–1.81 (2H, m),
1.63–1.25 (5H, m).
21. (6,7-Dimethoxy-quinazolin-4-yl)-isopropyl-amine (18): Following
a
similar
23. Compound 20 (ZM 323881) and Ki 8751 were both purchased from Tocris
Bioscience and used as received.
reaction procedure to 10, 73 mg (66% yield) of 18 was isolated as a white
crystalline solid. LC–MS: m/z = 248.0 (M+1, 100% intensity). 1H NMR (300 MHz,
CDCl3) d 8.88 (1H, s), 8.16 (1H, s), 7.44 (1H, s), 4.76 (1H, heptet, J = 6.9 Hz), 4.17
(3H, s), 4.08 (3H, s), 1.47 (6H, d, J = 6.9 Hz).
24. Compound 21 was prepared following
a three step reaction from the
corresponding (4-methoxyphenyl)-acetonitrile based on a previously reported
method.9 6-(4-Methoxy-phenyl)-3-thiophen-3-yl-pyrazolo[1,5-a]pyrimidine
(21): LC–MS: m/z = 308.0 (M+1, 100% intensity). 1H NMR (300 MHz, CDCl3): d
8.79 (1H, d, J = 2.4 Hz), 8.77 (1H, d, J = 2.4 Hz), 8.37 (1H, s), 7.90 (1H, dd, J = 3.0,
1.2 Hz), 7.70 (1H, dd, J = 5.1, 1.2 Hz), 7.54 (2H, d, J = 9.0 Hz), 7.43 (1H, dd, J = 5.1,
3.0 Hz), 7.06 (2H, d, J = 8.7 Hz), 3.89 (s, 3H).
22. Cyclohexyl-(6,7-dimethoxy-quinazolin-4-yl)-amine (19): Following a similar
reaction procedure to 10, 45 mg (35% yield) of 19 was isolated as a white
crystalline solid. LC–MS: m/z = 288.0 (M+1, 100% intensity). 1H NMR (300 MHz,
CDCl3) d 8.39 (1H, s), 7.44 (1H, s), 7.28 (1H, s), 4.32–4.28 (1H, m), 4.11 (3H, s),