Radiosynthesis of [11C]Vandetanib and [11C]chloro- Vandetanib as new potential PET agents for imaging of VEGFR in cancer

Article abstract of DOI:10.1016/j.bmcl.2011.04.049

Vandetanib (ZD6474) and its chlorine analogue chloro-Vandetanib are potent and selective vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors with low nanomolar IC₅₀ values. [ ¹¹C]Vandetanib and [¹¹C]chloro-Vandetanib, new potential PET agents for imaging of VEGFR in cancer, were first designed, synthesized and labeled at nitrogen and oxygen positions from their corresponding N- and O-des-methylated precursors, in 40-50% decay corrected radiochemical yield and 370-555 GBq/μmol specific activity at end of bombardment (EOB).

Full text of DOI:10.1016/j.bmcl.2011.04.049

Bioorganic & Medicinal Chemistry Letters 21 (2011) 3222–3226
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Radiosynthesis of [11C]Vandetanib and [11C]chloro-Vandetanib as new
potential PET agents for imaging of VEGFR in cancer
Mingzhang Gao a, Christian M. Lola a, Min Wang a, Kathy D. Miller b, George W. Sledge b, Qi-Huang Zheng a,
⇑
a Department of Radiology and Imaging Sciences, Indiana University School of Medicine, 1345 West 16th Street, Room 202, Indianapolis, IN 46202, USA
b Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Vandetanib (ZD6474) and its chlorine analogue chloro-Vandetanib are potent and selective vascular
endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors with low nanomolar IC50 values.
[
were first designed, synthesized and labeled at nitrogen and oxygen positions from their corresponding
N- and O-des-methylated precursors, in 40–50% decay corrected radiochemical yield and 370–555
Received 8 March 2011
Revised 8 April 2011
Accepted 12 April 2011
Available online 20 April 2011
11C]Vandetanib and [11C]chloro-Vandetanib, new potential PET agents for imaging of VEGFR in cancer,
GBq/lmol specific activity at end of bombardment (EOB).
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
[
[
11C]Vandetanib
11C]Chloro-Vandetanib
Vascular endothelial growth factor
receptors (VEGFR)
Radiosynthesis
Positron emission tomography (PET)
Cancer
Vascular endothelial growth factors (VEGF) are the most
common cancer causing angiogenic factors, and their receptors
(VEGFR) are overexpressed in tumor-associated endothelial cells.1
Angiogenesis contributes in particular to tumor growth.2 Vandeta-
nib [N-(4-bromo-2-fluorophenyl)-6-methoxy-7-((1-methylpiperi-
din-4-yl)methoxy)quinazolin-4-amine] (ZD6474), is an orally
bioavailable antitumor drug developed by AstraZeneca. It acts as
an antagonist for both VEGFR and epidermal growth factor receptor
(EGFR), and also inhibits tyrosine kinase (tk) activity.3 Vandetanib
selectively inhibits the tyrosine kinase activity of VEGFR-2 and
VEGFR-3, thereby blocking VEGF-stimulated endothelial cell prolif-
eration and migration, thus reducing tumor vessel permeability.
This agent also blocks the activity of EGFR, a receptor tyrosine kinase
that mediates tumor cell proliferation and migration and angiogen-
esis.4 IC50 valuesofVEGFR-2, VEGFR-3, andEGFRweredeterminedto
be 40, 110, and 500 nM, respectively.5 A chlorine analogue of
Vandetanib [chloro-Vandetanib, N-(4-chloro-2-fluorophenyl)-6-
methoxy-7-((1-methylpiperidin-4-yl)methoxy)quinazolin-4-amine]
displays similar or superior biological activities over Vandetanib.3
Carbon-11-labeled Vandetanib and its chlorine analogue may serve
as new probes for monitoring and imaging VEGFR in cancer by bio-
medical imaging technique positron emission tomography (PET).6
In our previous work, we developed a PET agent [11C]Gefitinib
([11C]Iressa) for imaging EGFR-tk, as indicated in Figure 1.7 The goal
of this study is to radiolabel therapeutic agents as diagnostic probes
to image VEGFR and monitoring its therapeutic efficacy as VEGFR-tk
inhibitors, we have first radiosynthesized [11C]Vandetanib [N-(4-
bromo-2-fluorophenyl)-6-methoxy-7-((1-[11C]methylpiperidin-4-
yl)methoxy)quinazolin-4-amine, or N-(4-bromo-2-fluorophenyl)-
6-[11C]methoxy-7-((1-methylpiperidin-4-yl)methoxy)quinazolin-
4-amine] and [11C]chloro-Vandetanib [N-(4-chloro-2-fluorophe-
nyl)-6-methoxy-7-((1-[11C]methylpiperidin-4-yl)methoxy)quinaz-
olin-4-amine, or N-(4-chloro-2-fluorophenyl)-6-[11C]methoxy-7-
((1-methylpiperidin-4-yl)methoxy)quinazolin-4-amine] as new
potential PET agents.
As illustrated in Scheme 1, Vandetanib (6b) and chloro-
Vandetanib (6a) as well as their corresponding N-des-methylated
precursors 5b and 5a were synthesized following the published
synthetic protocols.3,8,9 7-Benzyloxy-4-chloro-6-methoxyquinazo-
line (1) was reacted with anilines under acid catalysis in a protic
solvent i-propanol to give corresponding C-7-benzyloxyanilinoqui-
nazolines 2a, 2b in 94% and 93% yield, respectively. Deprotection of
the C-7-benzyl moiety was subsequently achieved using trifluoro-
acetyl acid (TFA) and led to the key intermediate 7-hydroxy-4-
anilinoquinazolines 3a, 3b in 91% and 93% yield, respectively.
Coupling reaction of 3a, 3b with tert-butyl 4-({[(4-methyl-
phenyl)sulfonyl]oxy}methyl)piperidine-1-carbonate under alkyl-
ation conditions (K2CO3/DMF) provided compounds 4a, 4b in 70%
and 68% yield, respectively. The tert-BOC protecting group of 4a,
⇑
Corresponding author. Tel.: +1 317 278 4671.
E-mail address: qzheng@iupui.edu (Q.-H. Zheng).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.04.049

M. Gao et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3222–3226
3223
F
F
O
HN
N
Cl
O
HN
N
Cl
N
O
O
N
O
O
N
N
H311C
Gefitinib (Iressa)
[
11C]Gefinitib ([11C]Iressa)
F
Br
F
Br
F
Br
HN
HN
HN
O
O
H311C
O
N
N
N
O
N
O
N
O
N
N
N
N
H311C
N-[11C]Vandetanib
O-[11C]Vandetanib
H3C
Vandetanib
H3C
Figure 1. Chemical structure of [11C]Gefitinib and [11C]Vandetanib.
F
R
F
R
Cl
HN
HN
O
O
i
N
ii
O
O
O
N
N
Ph
N
Ph
N
HO
N
1
3a, R = Cl, 91%
2a, R = Cl, 94%
2b, R = Br, 93%
3b, R = Br, 93%
F
R
F
R
HN
N
HN
O
O
BOC
N
O
iv
N
OTs
N
iii
O
N
N
4a, R = Cl, 70%
4b, R = Br, 68%
5a, R = Cl, 81%
5b, R = Br, 78%
HN
BOC
F
R
F
R
HN
HN
O
N
HO
N
v
vi
O
N
O
N
N
H3C
7a, R = Cl, 18%
7b, R = Br, 17%
N
H3C
6a (chloro-Vandetanib), R = Cl, 85%
6b (Vandetanib), R = Br, 86%
Scheme 1. Synthesis of Vandetanib, chloro-Vandetanib and their corresponding N- and O-des-methylated precursors. Reagents and conditions: (i) R-Ar-NH2/i-PrOH/HCl/
reflux; (ii) TFA/reflux; (iii) K2CO3/DMF/100 °C; (iv) TFA/CH2Cl2/rt; (v) HCHO/CH3COOH/NaBH(OAc)3/CH2Cl2/MeOH/rt; (vi) PyꢀHCl, 190 °C.
4b was subsequently removed by treating TFA to release the basic
piperidine nitrogen yielding N-des-methylated precursors 5a, 5b in
81% and 78% yield, respectively. N-Methylation of the piperidine
nitrogen of 5a, 5b using formaldehyde under reducing condition
with sodium triacetoxyborohydride (NaBH(OAc)3) gave the target
compounds chloro-Vandetanib and Vandetanib 6a, 6b in 85% and
86% yield, respectively. O-Desmethylation of 6a, 6b to produce
O-des-methylated precursors 7a, 7b proved to be difficult. A vari-
ety of protocols were screened for this purpose including Lewis
acids (LiCl, LiBr), base (EtSNa), protic acid (HBr) and organic salt
(pyridine hydrochloride).10 Pyridine hydrochloride was identified
as a suitable O-desmethylation agent to produce 7a, 7b in 18%
and 17% yield, respectively.
Radiosynthesis of the target radiotracer [
11C]Vandetanib
([11C]6b) and [11C]chloro-Vandetanib ([11C]6a) is indicated in
Scheme 2. N-des-Methylated precursor 5a or 5b was labeled by
[
11C]methyl triflate ([11C]CH3OTf) prepared from [11C]CO2,11,12 in
the presence of 2 N NaOH in acetonitrile through the N-[11C]meth-
ylation13,14 to provide N-[11C]-methylated product N-[11C]6a or
N-[11C]6b. Likewise, O-des-methylated precursor 7a or 7b was la-
beled by [11C]CH3OTf in the presence of 2 N NaOH in acetonitrile
through the O-[11C]methylation15,16 to provide O-[11C]-methylated
product O-[11C]6a or O-[11C]6b. The target tracer was purified by
semi-preparative high performance liquid chromatography (HPLC).
The synthesis was performed in an automated multi-purpose
[
11C]-radiosynthesis module, allowing measurement of specific

3224
M. Gao et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3222–3226
F
R
F
R
HN
O
O
HN
N
i
O
O
N
N
N
H311C
N
5a, R = Cl
5b, R = Br
HN
N-[11C]6a (N-[11C]chloro-Vandetanib), R = Cl
N-[11C]6b (N-[11C]Vandetanib), R = Br
40-50%
F
R
F
R
HN
O
O
H311C
N
HN
i
HO
O
N
N
N
H3C
N
O-[11C]6a (O-[11C]chloro-Vandetanib), R = Cl
O-[11C]6b (O-[11C]Vandetanib), R = Br
40-50%
N
7a, R = Cl
7b, R = Br
H3C
Scheme 2. Radiosynthesis of [11C]Vandetanib and [11C]chloro-Vandetanib. Reagents and conditions: (i) [11C]CH3OTf, CH3CN, 2 N NaOH, 80 °C.
activity during synthesis.17,18 The radiochemical yield for the tar-
get tracer was 40–50%, decay corrected to end of bombardment
(EOB), based on [11C]CO2. The specific activity of [11C]6a, [11C]6b
1H NMR spectra were recorded on a Bruker Avance II 500 MHz
NMR spectrometer in the Department of Chemistry and Chemical
Biology at Indiana University Purdue University Indianapolis
(IUPUI), which is supported by a NSF-MRI grant CHE-0619254.
was in a range of 370–555 GBq/lmol at EOB measured by the
on-the-fly technique using semi-preparative HPLC during synthe-
sis18 and 185–278 GBq/
lmol at the end of synthesis (EOS) deter-
mined by analytical HPLC.19 Chemical purity and radiochemical
purity were determined by analytical HPLC.19 The chemical purity
of the precursors 5a, 5b, 7a, 7b and reference standard 6a, 6b was
>95%. The radiochemical purity of the target tracer [11C]6a, [11C]6b
References and notes
1. Wheeler, W. J.; Clodfelter, D. K. J. Labelled Compd. Radiopharm. 2008, 51, 175.
2. Dempke, W. C.; Zippel, R. Anticancer Res. 2010, 30, 4477.
3. Hennequin, L. F.; Stokes, E. S.; Thomas, A. P.; Johnstone, C.; Plé, P. A.; Ogilvie, D.
J.; Dukes, M.; Wedge, S. R.; Kendrew, J.; Curwen, J. O. J. Med. Chem. 2002, 45,
1300.
was >99% determined by radio-HPLC through
flow detector, and the chemical purity of the target tracers
11C]6a, [11C]6b was >93% determined by reversed-phase HPLC
c-ray (PIN diode)
4. NCI
Drug
Dictionary,
2011.
<http://cme.nci.nih.gov/drugdictionary/
?CdrID=269177>.
[
5. Morabito, A.; Piccirillo, M. C.; Falasconi, F.; De Feo, G.; Del Giudice, A.; Bryce, J.;
Di Maio, M.; De Maio, E.; Normanno, N.; Perrone, F. Oncologist 2009, 14, 378.
6. Samén, E.; Thorell, J. O.; Lu, L.; Tegnebratt, T.; Holmgren, L.; Stone-Elander, S.
Eur. J. Nucl. Med. Mol. Imaging 2009, 36, 1283.
7. Wang, J.-Q.; Gao, M.; Miller, K. D.; Sledge, G. W.; Zheng, Q.-H. Bioorg. Med. Chem.
Lett. 2006, 16, 4102.
8. Hennequin, L. F.; Thomas, A. P.; Johnstone, C.; Stokes, E. S.; Plé, P. A.; Lohmann,
J. J.; Ogilvie, D. J.; Dukes, M.; Wedge, S. R.; Curwen, J. O.; Kendrew, J.; Lambert-
van der Brempt, C. J. Med. Chem. 1999, 42, 5369.
9. Gangjee, A.; Zaware, N.; Raghavan, S.; Ihnat, M.; Shenoy, S.; Kisliuk, R. L. J. Med.
Chem. 2010, 53, 1563.
through UV flow detector.
The experimental details and characterization data for com-
pounds 2a,b–7a,b and for the tracers [11C]6a,b are given.20
In summary, [11C]Vandetanib and [11C]chloro-Vandetanib were
first designed and synthesized as new potential PET agents for
imaging of VEGFR in cancer. An automated self-designed multi-
purpose
[
[
11C]-radiosynthesis module for the synthesis of
11C]Vandetanib and [11C]chloro-Vandetanib has been built, featur-
ing the measurement of specific activity by the on-the-fly tech-
nique. The radiosynthesis employed either N-[11C]methylation or
O-[11C]methylation radiolabeling on nitrogen or oxygen position
of the precursor. Radiolabeling procedures incorporated efficiently
10. Wang, M.; Gao, M.; Miller, K. D.; Sledge, G. W.; Hutchins, G. D.; Zheng, Q.-H. J.
Labelled Compd. Radiopharm. 2008, 51, 6.
11. Jewett, D. M. Int. J. Radiat. Appl. Instrum. A 1992, 43, 1383.
12. Mock, B. H.; Mulholland, G. K.; Vavrek, M. J. Nucl. Med. Biol. 1999, 26, 467.
13. Zheng, Q.-H.; Mulholland, G. K. Nucl. Med. Biol. 1996, 23, 981.
14. Gao, M.; Mock, B. H.; Hutchins, G. D.; Zheng, Q.-H. Nucl. Med. Biol. 2005, 32, 543.
15. Gao, M.; Wang, M.; Hutchins, G. D.; Zheng, Q.-H. Appl. Radiat. Isot. 2008, 66,
1891.
16. Yoder, K. K.; Hutchins, G. D.; Mock, B. H.; Fei, X.; Winkle, W. L.; Gitter, B. D.;
Territo, P. R.; Zheng, Q.-H. Nucl. Med. Biol. 2009, 36, 11.
17. Mock, B. H.; Zheng, Q.-H.; DeGrado, T. R. J. Labelled Compd. Radiopharm. 2005,
48, S225.
with the most commonly used
[
11C]methylating agent,
[
11C]CH3OTf, produced by gas-phase production of [11C]methyl
bromide ([11C]CH3Br) from our laboratory. The target tracers were
isolated and purified by a semi-preparative HPLC procedure in high
radiochemical yields, short overall synthesis time, and high specific
activity. These results facilitate the potential preclinical and clini-
cal PET studies of [11C]Vandetanib and [11C]chloro-Vandetanib in
animals and humans.
18. Mock, B. H.; Glick-Wilson, B. E.; Zheng, Q.-H.; DeGrado, T. R. J. Labelled Compd.
Radiopharm. 2005, 48, S224.
19. Zheng, Q.-H.; Mock, B. H. Biomed. Chromatogr. 2005, 19, 671.
20. (a) General: All commercial reagents and solvents were purchased from Sigma-
Aldrich and Fisher Scientific, and they were used without further purification.
Acknowledgments
[
11C]CH3OTf was prepared according to a literature procedure.12 Melting points
were determined on
a MEL-TEMP II capillary tube apparatus and were
uncorrected. 1H NMR spectra were recorded on Bruker Avance II 500 MHz
NMR spectrometers using tetramethylsilane (TMS) as an internal standard.
Chemical shift data for the proton resonances were reported in parts per
million (ppm, d scale) relative to internal standard TMS (d 0.0), and coupling
constants (J) were reported in hertz (Hz). Liquid chromatography-mass spectra
(LC–MS) analysis was performed on an Agilent system, consisting of an 1100
This work was partially supported by the Breast Cancer
Research Foundation and Indiana Genomics Initiative (INGEN) of
Indiana University, which is supported in part by Lilly Endowment
Inc. The authors would like to thank Dr. Bruce H. Mock and Barbara
E. Glick-Wilson for their assistance in production of [11C]CH3OTf.

M. Gao et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3222–3226
3225
series HPLC connected to
spectrometer configured
a
diode array detector and
a
1946D mass
electrospray
chromatography with eluent (20–50% MeOH/CH2Cl2) on silica gel to afford
for positive-ion/negative-ion
5a (0.67 g, 81%) as a white solid: Rf = 0.15 (50:50:1 MeOH/CH2Cl2/NH3ꢀH2O);
ionization. The high resolution mass spectra (HRMS) were obtained using a
Waters/Micromass LCT Classic spectrometer. Chromatographic solvent
proportions are indicated as volume: volume ratio. Thin-layer
chromatography (TLC) was run using Analtech silica gel GF uniplates
(5 ꢁ 10 cm2). Plates were visualized under UV light. Preparative TLC was run
using Analtech silica gel UV 254 plates (20 ꢁ 20 cm2). Normal phase flash
column chromatography was carried out on EM Science silica gel 60 (230–
mp 220–222 °C.; 1H NMR (CDCl3)
d 1.30 (ddd, J = 4.0, 12.5, 25.0 Hz, 2H,
piperidine-H), 1.87 (d, J = 12.5 Hz, 2H, piperidine-H), 2.09–2.12 (m, 1H,
piperidine-H), 2.65 (dt, J = 2.5, 12.0 Hz, 2H, piperidine-H), 3.13 (d, J = 12.0 Hz,
2H, piperidine-H), 4.00 (d, J = 6.5 Hz, 2H, CH2O), 4.02 (s, 3H, CH3O), 7.01 (s, 1H,
Ar–H), 7.20 (s, 1H, Ar–H), 7.22 (s, 1H, Ar–H), 7.24 (s, 1H, Ar–H), 7.28 (s, 1H, Ar–
H), 8.52 (t, J = 8.5 Hz, 1H, Ar–H), 8.67 (s, 1H, Ar-NH); MS (ESI, m/z): 417
([M+H]+, 100%).
400 mesh) with
a
forced flow of the indicated solvent system in the
(i) N-(4-Bromo-2-fluorophenyl)-6-methoxy-7-(piperidin-4-ylmethoxy)quina
zolin-4-amine (5b). A similar procedure for 5a was used to prepare 5b (78%)
as a white solid: Rf = 0.15 (50:50:1 MeOH/CH2Cl2/NH3ꢀH2O); mp 221–223 °C;
1H NMR (CDCl3) d 1.30 (ddd, J = 4.0, 12.0, 25.0 Hz, 2H, piperidine-H), 1.86 (d,
J = 12.5 Hz, 2H, piperidine-H), 2.08–2.11 (m, 1H, piperidine-H), 2.66 (dt, J = 2.5,
12.0 Hz, 2H, piperidine-H), 3.13 (d, J = 12.0 Hz, 2H, piperidine-H), 3.98 (d,
J = 6.5 Hz, 2H, CH2O), 4.00 (s, 3H, CH3O), 7.01 (s, 1H, Ar–H), 7.23 (s, 1H, Ar–H),
7.33 (s, 1H, Ar–H), 7.35 (s, 1H, Ar–H), 7.36 (s, 1H, Ar–H), 8.46 (t, J = 8.5 Hz, 1H,
Ar–H), 8.67 (s, 1H, Ar-NH); MS (ESI, m/z): 463 ([M+H]+, 100%).
(j) N-(4-Chloro-2-fluorophenyl)-6-methoxy-7-((1-methylpiperidin-4-yl)
methoxy)quinazolin-4-amine (6a, chloro-Vandetanib). 37% aqueous solution
of formaldehyde (40 mg, 0.52 mmol) followed by NaBH(OAc)3 (120 mg,
0.56 mmol) were added in portions to the solution of 5a (167 mg, 0.4 mmol)
and acetic acid (28 mg, 0.48 mmol) in CH2Cl2 (10 mL) and methanol (20 mL).
After the reaction mixture was stirred at rt for 2 h, and the solvents were
removed under vacuum. The resulting residue was added aqueous NaHCO3, the
precipitate was filtered, washed with water and brine, and dried to obtain
white solid; the aqueous layer was extracted with CH2Cl2, dried over MgSO4,
filtered and evaporated to provide a residue, which was washed with Et2O to
obtain white solid. The combined white solid gave 6a (146 mg, 85%): Rf = 0.36
(50:50:1 MeOH/CH2Cl2/NH3ꢀH2O); mp 226–228 °C; 1H NMR (CDCl3) d 1.45
(ddd, J = 4.0, 12.5, 25.0 Hz, 2H, piperidine-H), 1.88 (d, J = 12.5 Hz, 2H,
piperidine-H), 1.94–1.96 (m, 3H, piperidine-H), 2.29 (s, 3H, NCH3), 2.90 (d,
J = 12.0 Hz, 2H, piperidine-H), 4.02 (s, 3H, CH3O), 4.03 (d, J = 5.5 Hz, 2H, CH2O),
7.00 (s, 1H, Ar–H), 7.20 (s, 1H, Ar–H), 7.22 (s, 1H, Ar–H), 7.23 (s, 1H, Ar–H), 7.24
(s, 1H, Ar–H), 8.53 (t, J = 8.5 Hz, 1H, Ar–H), 8.68 (s, 1H, Ar-NH); MS (ESI, m/z):
431 ([M+H]+, 100%).
proportions described below. All moisture- and air-sensitive reactions were
performed under a positive pressure of nitrogen maintained by a direct line
from
(Phenomenex) 5
MeOH/20 mm, pH 6.7 phosphate (buffer solution); flow rate 1.5 mL/min; and
a nitrogen source. Analytical HPLC was performed using a Prodigy
lm C-18 column, 4.6 ꢁ 250 mm; mobile phase 3:1:1 CH3CN/
UV (254 nM) and
performed using
c
a
-ray (PIN diode) flow detectors. Semi-preparative HPLC was
YMC-Pack ODS-A, S-5
m, 12 nM, 10 ꢁ 250 mm C-18
l
column; 3:1:1 CH3CN/MeOH/20 mm, pH 6.7 phosphate (buffer solution)
mobile phase; 5.0 mL/min flow rate; UV (254 nM) and -ray (PIN diode) flow
detectors. Sterile Millex-GS 0.22 m vented filter unit was obtained from
Millipore Corporation, Bedford, MA.
(b) 7-(Benzyloxy)-N-(4-chloro-2-fluorophenyl)-6-methoxyquinazolin-4-amine
hydrochloride (2a). Hydrogen chloride (6.5 M, 2.54 mL) was added to a mixture
c
l
of compound
1 (4.51 g, 15.0 mmol) and 4-chloro-2-fluoroaniline (2.40 g,
16.5 mmol) in 2-propanol (160 mL), then the mixture was heated at reflux
for 2 h. The mixture was cooled and solid was filtered. The solid was then
washed with 2-propanol, followed by Et2O, and dried under vacuum overnight
to give 2a (7.9 g, 94%) as a white solid: mp 243–245 °C; 1H NMR (DMSO-d6) d
4.00 (s, 3H, CH3O), 5.35 (s, 2H, CH2O), 7.39–7.55 (m, 7H, Ar–H), 7.60 (t,
J = 8.5 Hz, Ar–H), 7.67 (dd, J = 2.0, 10.0 Hz, 1H, Ar–H), 8.37 (s, 1H, H5), 8.80 (s,
1H, H2), 11.71 (s, 1H); MS (ESI, m/z): 410 ([M+H]+, 100%).
(c) 7-(Benzyloxy)-N-(4-bromo-2-fluorophenyl)-6-methoxyquinazolin-4-amine
hydrochloride (2b). A similar procedure for 2a was used to prepare 2b (93%) as
a white solid: mp 244–246 °C. 1H NMR (DMSO-d6) d 4.01 (s, 3H, CH3O), 5.35 (s,
2H, CH2O), 7.43–7.58 (m, 8H, Ar–H), 7.78 (dd, J = 2.0, 10.0 Hz, 1H, Ar–H), 8.35
(s, 1H, H5), 8.80 (s, 1H, H2), 11.66 (s, 1H); MS (ESI, m/z): 456 ([M+H]+, 100%).
(d) 4-((4-Chloro-2-fluorophenyl)amino)-6-methoxyquinazolin-7-ol (3a).
A
(k) N-(4-Bromo-2-fluorophenyl)-6-methoxy-7-((1-methylpiperidin-4-yl)
methoxy)quinazolin-4-amine (6b, Vandetanib). A similar procedure for 6a
was used to prepare 6b (86%) as a white solid: Rf = 0.36 (50:50:1 MeOH/
CH2Cl2/NH3ꢀH2O); mp 227–229 °C; 1H NMR (CDCl3) d 1.45 (ddd, J = 4.0, 12.5,
25.0 Hz, 2H, piperidine-H), 1.88 (d, J = 12.5 Hz, 2H, piperidine-H), 1.94–2.00 (m,
3H, piperidine-H), 2.29 (s, 3H, NCH3), 2.90 (d, J = 12.0 Hz, 2H, piperidine-H),
4.02 (s, 3H, CH3O), 4.03 (d, J = 5.5 Hz, 2H, CH2O), 6.99 (s, 1H, Ar–H), 7.24 (s, 1H,
Ar–H), 7.25 (s, 1H, Ar–H), 7.34 (d, J = 1.0 Hz, 1H, Ar–H), 7.36 (d, J = 1.0 Hz, 1H,
Ar–H), 8.51 (t, J = 8.5 Hz, 1H, Ar–H), 8.68 (s, 1H, Ar-NH); MS (ESI, m/z): 475
([M+H]+, 100%).
solution of 2a (4.46 g, 10.0 mmol) in TFA (30 mL) was refluxed for 1 h. After
the reaction mixture was evaporated, the mixture was added cold aqueous
NaHCO3 and concentrated NH3.H2O, and pH of solution was then adjusted to
10. The resulted precipitate was filtered, washed with water and Et2O, and
dried under vacuum to give 3a (2.91 g, 91%) as a white solid: Rf = 0.20 (1:1
EtOAc/hexanes); mp 267–269 °C; 1H NMR (DMSO-d6) d 3.93 (s, 3H, CH3O), 7.05
(s, 1H, H8), 7.32 (dd, J = 2.0, 8.5 Hz, 1H, H60), 7.52 (dd, J = 2.0, 10.0 Hz, 1H, H50),
7.58 (t, J = 8.5 Hz, 1H, H30), 7.74 (s, 1H, H5), 8.26 (s, 1H, H2), 9.30 (s, 1H, OH);
MS (ESI, m/z): 320 ([M+H]+, 100%).
(e) 4-((4-Bromo-2-fluorophenyl)amino)-6-methoxyquinazolin-7-ol (3b).
A
(l) 4-((4-Chloro-2-fluorophenyl)amino)-7-((1-methylpiperidin-4-yl) methoxy)
quinazolin-6-ol (7a). A mixture of compound 6a (151 mg, 0.35 mmol) and
pyridine hydrochloride (3.2 g, 30 mmol) was heated at 190–200 °C for 80 min
and then cooled to rt. Aqueous NaHCO3 was added to reaction mixture to
adjust pH of solution to 9, and the solution was extracted with EtOAc
(80 mL ꢁ 3). The organic layers were washed with water and brine, dried over
Na2SO4, and evaporated. The residue was purified by column chromatography
with eluent (20–50% MeOH/CH2Cl2) on silica gel to give 7a (26 mg, 18%) as a
white solid: Rf = 0.30 (50:50:1 MeOH/CH2Cl2/NH3ꢀH2O); mp 219–221 °C; 1H
similar procedure for 3a was used to prepare 3b (93%) as a white solid:
Rf = 0.20 (1:1 EtOAc/hexanes); mp 268–270 °C; 1H NMR (DMSO-d6) d 3.93 (s,
3H, CH3O), 7.02 (s, 1H, H8), 7.44 (dd, J = 2.0, 8.5 Hz, 1H, H60), 7.52 (t, J = 8.5 Hz,
1H, H30),7.63 (dd, J = 2.0, 10.0 Hz, 1H, H50), 7.75 (s, 1H, H5), 8.26 (s, 1H, H2),
9.30 (s, 1H, OH); MS (ESI, m/z): 366 ([M+H]+, 100%).
(f) tert-Butyl 4-(((4-((4-chloro-2-fluorophenyl)amino)-6-methoxyquinazolin-
7-yl)oxy)methyl)piperidine-1-carboxylate (4a). K2CO3 (1.38 g, 10.0 mmol) was
added to a suspension of compound 3a (1.60 g, 5.0 mmol) and tert-butyl 4-
({[(4-methylphenyl)sulfonyl]oxy}methyl)piperidine-1-carbonate
(2.07 g,
NMR (MeOH-d4) d 1.49–1.53 (m, 2H, piperidine-H), 1.96–1.99 (m, 3H,
5.6 mmol) in DMF (45 mL), and stirred at room temperature (rt) for 1 h and
heated at 90 °C for 3 h. After the mixture was cooled, it was poured into cold
water, and extracted with EtOAc (150 mL ꢁ 3). The organic layers were washed
brine, dried over Na2SO4, filtered, and evaporated to give a residue, which was
purified by column chromatography with eluent (2% MeOH/CH2Cl2) on silica
gel to afford 4a (1.80 g, 70%) as a white solid: Rf = 0.50 (5% MeOH/CH2Cl2); mp
222–224 °C; 1H NMR (DMSO-d6) d 1.20–1.22 (m, 2H, piperidine-H), 1.40 (s, 9H,
CH3) 1.77 (d, J = 11.0 Hz, 2H, piperidine-H), 1.98–2.07 (m, 1H, piperidine-H),
2.70–2.85 (m, 2H, piperidine-H), 3.94 (s, 3H, CH3O), 3.98 (br s, 2H, piperidine-
H), 4.02 (d, J = 6.5 Hz, 2H, OCH2), 7.18 (s, 1H, H8), 7.33 (ddd, J = 1.0, 2.0, 8.5 Hz,
1H, H60), 7.54 (dd, J = 2.0, 10.0 Hz, 1H, H50), 7.58 (t, J = 8.5 Hz, 1H, H30), 7.79 (s,
1H, H5), 8.35 (s, 1H, H2), 9.54 (s, 1H, NH); MS (ESI, m/z): 517 ([M+H]+, 100%).
(g) tert-Butyl 4-(((4-((4-bromo-2-fluorophenyl)amino)-6-methoxyquinazolin-
7-yl)oxy)methyl)piperidine-1-carboxylate (4b). A similar procedure for 4a was
used to prepare 4b (68%) as a white solid: Rf = 0.50 (5% MeOH/CH2Cl2); mp
223–225 °C. 1H NMR (DMSO-d6) d 1.20–1.30 (m, 2H, piperidine-H), 1.40 (s, 9H,
CH3) 1.77 (d, J = 11.0 Hz, 2H, piperidine-H), 1.98–2.07 (m, 1H, piperidine-H),
2.70–2.85 (m, 2H, piperidine-H), 3.94 (s, 3H, CH3O), 3.98–4.01 (m, 2H,
piperidine-H), 4.02 (d, J = 6.5 Hz, 2H, OCH2), 7.18 (s, 1H, H8), 7.45 (dd, J = 2.0,
8.5 Hz, 1H, H60), 7.53 (t, J = 8.5 Hz, 1H, H30), 7.64 (dd, J = 2.0, 10.0 Hz, 1H, H50),
7.79 (s, 1H, H5), 8.35 (s, 1H, H2), 9.53 (s, 1H, NH); MS (ESI, m/z): 563 ([M+H]+,
100%).
piperidine-H), 2.12 (t, J = 11.5 Hz, 2H, piperidine-H), 2.31 (s, 3H, NCH3), 2.95
(d, J = 11.0 Hz, 2H, piperidine-H), 4.04 (d, J = 5.5 Hz, 2H, CH2O), 7.12 (s, 1H, Ar–
H), 7.25 (d, J = 8.0 Hz, 1H, Ar–H), 7.30 (dd, J = 2.0, 10.0 Hz, 1H, Ar–H), 7.50 (s,
1H, Ar–H), 7.66 (t, J = 8.0 Hz, 1H, Ar–H), 8.26 (s, 1H, Ar–H); MS (ESI, m/z): 417
([M+H]+, 100%); HRMS (ESI, m/z): Calcd for C21H23N4O2FCl 417.1494 ([M+H]+),
found 417.1477.
(m) 4-((4-Bromo-2-fluorophenyl)amino)-7-((1-methylpiperidin-4-yl) methoxy)
quinazolin-6-ol (7b). A similar procedure for 7a was used to prepare 7b
(17%) as a white solid: Rf = 0.30 (50:50:1 MeOH/CH2Cl2/NH3ꢀH2O); mp 223–
225 °C; 1H NMR (MeOH-d4) d 1.50–1.54 (m, 2H, piperidine-H), 1.96–1.99 (m,
3H, piperidine-H), 2.13 (t, J = 11.0 Hz, 2H, piperidine-H), 2.32 (s, 3H, NCH3),
2.95 (d, J = 11.0 Hz, 2H, piperidine-H), 4.05 (d, J = 5.5 Hz, 2H, CH2O), 7.13 (s, 1H,
Ar–H), 7.40 (d, J = 8.5 Hz, 1H, Ar–H), 7.44 (dd, J = 2.0, 10.0 Hz, 1H, Ar–H), 7.53 (s,
1H, Ar–H), 7.62 (t, J = 8.0 Hz, 1H, Ar–H), 8.26 (s, 1H, Ar–H); MS (ESI, m/z): 461
([M+H]+, 100%); HRMS (ESI, m/z): Calcd for C21H23N4O2FBr 461.0988 ([M+H]+),
found 461.0980; and 463.0971 ([M+H]+), found 463.0956.
(n) N-(4-Chloro-2-fluorophenyl)-6-methoxy-7-((1-[11C]methylpiperidin-4-yl)
methoxy)quinazolin-4-amine (N-[11C]chloro-Vandetanib, N-[11C]6a), N-(4-
bromo-2-fluorophenyl)-6-methoxy-7-((1-[11C]methylpiperidin-4-yl)methoxy)
quinazolin-4-amine
fluorophenyl)-6-[11C]methoxy-7-((1-methylpiperidin-4-yl)methoxy)quinazolin-
4-amine and N-(4-bromo-2-
(O-[11C]chloro-Vandetanib, O-[11C]6a),
fluorophenyl)-6-[11C]methoxy-7-((1-methylpiperidin-4-yl)methoxy)quinazolin-
4-amine (O-[11C]Vandetanib, O-[11C]6b). 11C]CO2 was produced by the
14N(p, 11C nuclear reaction on ultra high purity nitrogen (+1% O2) in the
small volume (9.5 cm3) aluminum gas target of the Siemens Eclipse RDS-111
cyclotron. Precursor 5a, 5b, 7a, or 7b (0.1 mg) was dissolved in CH3CN (500 L)
and added to the 5 mL reaction vial of the methylation module, along with
NaOH (2 N, 2
L). Carrier-free (high specific activity) [11C]CH3OTf produced by
the gas-phase production method12 from 11C]CO2 through 11C]CH4 and
(N-[11C]Vandetanib,
N-[11C]6b),
N-(4-chloro-2-
(h) N-(4-Chloro-2-fluorophenyl)-6-methoxy-7-(piperidin-4-ylmethoxy)quina
zolin-4-amine (5a). TFA (5 mL) was added to a suspension of compound 4a
(1.03 g, 2.0 mmol) in CH2Cl2 (20 mL), and stirred at rt for 2 h, and the volatiles
were removed under vacuum. The reaction mixture was quenched with water
and extracted with Et2O. The organic layer was separated, and the aqueous
layer was adjusted to pH 10 with 3 N NaOH, and then extracted with CH2Cl2.
The combined organic layers were dried over MgSO4, and the solvent was
removed under vacuum. The crude product was purified by column
[
a
)
l
l
[
[

3226
M. Gao et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3222–3226
[
11C]CH3Br with silver triflate (AgOTf) column was passed into the reaction vial
tracer dose dispensing. Retention times in the semi-preparative HPLC system
were: tR 5a = 6.12 min, tR 6a = 8.92 min, tR N-[11C]6a = 8.92 min; tR
5b = 6.67 min, tR 6b = 9.13 min, tR N-[11C]6b = 9.13 min; tR 7a = 6.35 min, tR
6a = 8.92 min, tR O-[11C]6a = 8.92 min; tR 7b = 6.56 min, tR 6b = 9.13 min, tR O-
at rt until radioactivity reached a maximum, and then the reaction vial was
isolated and heated at 80 °C for 3 min. The reaction mixture was cooled to
ꢂ50 °C, diluted with NaHCO3 (0.1 M, 1 mL) and injected onto the semi-
preparative HPLC column through a 3 mL injection loop for purification. The
product fraction was collected, the solvent was removed by rotatory
evaporation under vacuum, and the final product N-[11C]6a, N-[11C]6b, O-
[
11C]6b = 9.13 min. Retention times in the analytical HPLC system were: tR
5a = 2.76 min, tR 6a = 4.72 min, tR N-[11C]6a = 4.72 min; tR 5b = 2.73 min, tR
6b = 4.98 min, tR N-[11C]6b = 4.98 min; tR 7a = 2.63 min, tR 6a = 4.72 min, tR O-
[
11C]6a, or O-[11C]6b was formulated in saline, sterile-filtered through a sterile
[
11C]6a = 4.72 min; tR 7b = 2.75 min, tR 6b = 4.98 min, tR O-[11C]6b = 4.98 min.
vented Millex-GS 0.22
sterile vial. Total radioactivity was assayed and total volume was noted for
l
m cellulose acetate membrane, and collected into a
The radiochemical yields were 40–50% decay corrected to EOB, based on
[
11C]CO2.