Synthesis and preliminary biological evaluation of new carbon-11 labeled tetrahydroisoquinoline derivatives as SERM radioligands for PET imaging of ER expression in breast cancer

Article abstract of DOI:10.1016/j.ejmech.2008.01.001

The estrogen receptors (ERs) are attractive targets in the treatment of breast cancer and the development of receptor-based breast cancer imaging agents for diagnostic use in biomedical imaging technique positron emission tomography (PET). Tetrahydroisoqu

Full text of DOI:10.1016/j.ejmech.2008.01.001

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 43 (2008) 2211e2219
http://www.elsevier.com/locate/ejmech
Original article
Synthesis and preliminary biological evaluation of new carbon-11
labeled tetrahydroisoquinoline derivatives as SERM radioligands for
PET imaging of ER expression in breast cancer
Mingzhang Gao a, Min Wang a, Kathy D. Miller b, George W. Sledge b, Qi-Huang Zheng a,
*
a Department of Radiology, Indiana University School of Medicine, 1345 West 16th Street, L3-208, Indianapolis, IN 46202, USA
b Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
Received 29 November 2007; received in revised form 18 December 2007; accepted 2 January 2008
Available online 11 January 2008
Abstract
The estrogen receptors (ERs) are attractive targets in the treatment of breast cancer and the development of receptor-based breast cancer im-
aging agents for diagnostic use in biomedical imaging technique positron emission tomography (PET). Tetrahydroisoquinoline derivatives are
a class of selective estrogen receptor modulators (SERMs) with high binding affinity and specificity exhibiting up to 50 folds for ERa over
ERb. New carbon-11 labeled tetrahydroisoquinoline derivatives, [11C]methyl 1-(2-(4-(2-(4-fluorophenyl)-6-hydroxy-1-methyl-1,2,3,4-tetrahy-
droisoquinolin-1-yl)phenoxy)ethyl)piperidine-4-carboxylate ([11C]10a) and [11C]methyl 1-(2-(4-(2-(4-chlorophenyl)-6-hydroxy-1-methyl-
1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)piperidine-4-carboxylate ([11C]10b), have been first designed, synthesized and evaluated.
The target tracers were prepared by O-[11C]methylation of their corresponding precursors using [11C]CH3OTf and isolated by solid-phase
extraction (SPE) purification procedure in 40e60% radiochemical yields, which were decay corrected to the end of bombardment (EOB), based
on [11C]CO2. The overall synthesis time was 15e20 min from EOB. The radiochemical purity was >99%, and specific activity was in a range of
74e111 GBq/mmol at the end of synthesis (EOS). Preliminary findings from in vitro biological assay indicate that the synthesized derivatives
displayed similar potencies in the MCF-7 human breast cancer cell line in comparison with 4-hydroxytamoxifen, a well-known potent
SERM. These results encourage further in vivo evaluation of carbon-11 labeled tetrahydroisoquinoline derivatives as new potential SERM radio-
ligands for PET imaging of ER expression in breast cancer.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Carbon-11; Tetrahydroisoquinoline derivatives; Positron emission tomography (PET); Estrogen receptors; Selective estrogen receptor modulators
(SERMs); Cancer imaging
1. Introduction
The estrogen receptors (ERs) are attractive targets in the
treatment of breast cancer and the development of receptor-
based breast cancer imaging agents for diagnostic use in bio-
medical imaging technique positron emission tomography
(PET) [1,2]. The positron labeled steroidal estrogen 16a-[18F]
Abbreviations: SERMs, selective estrogen receptor modulators; PET,
positron emission tomography; ERs, estrogen receptors; SPE, solid-phase
extraction; EOB, end of bombardment; EOS, end of synthesis; PPA, polyphos-
phoric acid; HPLC, high pressure liquid chromatography; rt, room tempera-
ture; ERE, estrogen response element; SAR, structureeactivity relationship;
TMS, tetramethylsilane; LRMS, low resolution mass spectra; HRMS, high res-
olution mass spectra; RDS, radionuclide delivery system; OD, optical density;
INGEN, Indiana Genomics Initiative.
fluoro-17b-estradiol, a 17b-estradiol derivative and a well-
known ER radioligand as indicated in Fig. 1, has been devel-
oped as a PET breast cancer ER imaging agent [3]. A number
of selective estrogen receptor modulators (SERMs) such as
tamoxifen and 4-hydroxytamoxifen (Fig. 1) are currently in
advanced clinical trials or in the market for the treatment of
* Corresponding author. Tel.: þ1 317 278 4671; fax: þ1 317 278 9711.
E-mail address: qzheng@iupui.edu (Q.-H. Zheng).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.01.001

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M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
OH
carbamate compound 2 in 96% yield. The subsequent cycliza-
OH
tion of compound 2 with polyphosphoric acid (PPA) provided
bicyclic lactam compound 3 in 77% yield. N-Arylation of
compound 3 with 1-fluoro-4-iodobenzene or 1-chloro-4-iodo-
benzene under Ullmann-type conditions using CuI in DMF af-
forded compounds 4a,b in 91% and 90% yields, respectively.
Treatment of compounds 4a,b with benzyloxyphenyllithium
and subsequent acidic workup with HClO4 gave intermediate
iminium salts 5a,b in quantitative yield. The iminium salts
5a,b were subsequently treated with MeMgBr in THF to
give 1-methyl-tetrahydroisoquinolines 6a,b in 75% and 73%
yields, respectively. AlCl3-mediated debenzylation in the pres-
ence of Me2NPh in CH2Cl2 of compounds 6a,b yielded phe-
nols 7a,b in 70% and 72% yields, respectively. Alkylation of
compounds 7a,b with BrCH2CH2Cl or ClCH2CH2OTs fur-
nished compounds 8a,b in 52e68% yields. Compounds 8a,b
were treated with methyl piperidine-4-carboxylate to give
esters 9a,b in 92% and 91% yields, respectively. The cleavage
of the methyl ether of compounds 9a,b in the presence of
AlCl3 and EtSH provided target tetrahydroisoquinoline com-
pounds 10a,b as reference standards in 41% and 36% yields,
respectively. The hydrolysis of compounds 10a,b afforded
acids 11a,b as precursors in 88% and 86% yields, respectively.
Compounds 10a,b were selected as the lead candidates for
PET radioligand development for reasons of ERa selectivity,
potency and feasibility of chemical modification to incorpo-
rate an O-methyl group at the ester moiety. The O-methyl
group serves as a platform for radiolabeling of this series of
methyl ester compounds with a positron emitting radioisotope
carbon-11 as potential PET radiopharmaceuticals. Compounds
10a,b (10a, X ¼ F; 10b, X ¼ Cl) are halo-tetrahydroisoquino-
line compounds, and they are amenable to labeling with
another positron emitting radioisotope fluorine-18 by a conven-
tional nucleophilic substitution with K [18F]F/Kryptofix 2.2.2
[9] to be new fluorine-18 PET agents. In this regard, com-
pound 10b could be the precursor for compound 10a in fluo-
rine-18 radiolabeling reaction.
18F
HO
HO
N
16α-[18F] Fluoro-17β-estradiol
17β-Estradiol
N
O
O
HO
4-Hydroxytamoxifen
Tamoxifen
Fig. 1. Chemical structures of estrogens and SERMs.
hormone-dependent breast cancer [4]. Recently, a series of
tetrahydroisoquinoline derivatives have been developed as
new and potent SERMs, and they are found to bind with high
affinity to the two currently known ERs, ERa and ERb, and
specificity exhibiting up to 50 folds for ERa over ERb [5,6].
Tetrahydroisoquinoline derivatives labeled with a positron
emitting radionuclide carbon-11 or fluorine-18 may enable
non-invasive monitoring of ER expression in breast cancer
and breast cancer response to hormone therapy. We are inter-
ested in the development of PET breast cancer imaging agents.
In our previous works, we have developed carbon-11 labeled
cyclofenil derivatives as new potential PET nonsteroidal estro-
gen radioligands for imaging ER expression in breast cancer
[7]. This ongoing study was to develop new SERM radioli-
gands. To further develop therapeutic agent for diagnostic
use, we have first designed, synthesized and evaluated car-
bon-11 labeled tetrahydroisoquinoline derivatives, [11C]methyl
1-(2-(4-(2-(4-fluorophenyl)-6-hydroxy-1-methyl-1,2,3,4-tetra-
hydroisoquinolin-1-yl)phenoxy)ethyl)piperidine-4-carboxylate
([11C]10a) and [11C]methyl 1-(2-(4-(2-(4-chlorophenyl)-6-
hydroxy-1-methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)
ethyl)piperidine-4-carboxylate ([11C]10b) as new potential
SERM radioligands for PET imaging of ER expression in
breast cancer.
2.2. Radiochemistry
Synthesis of the target tracers, carbon-11 labeled tetrahy-
droisoquinoline derivatives [11C]10a,b is outlined in Scheme
2. The precursor 11a or 11b was labeled by [11C]methyl tri-
flate ([11C]CH3OTf) [10,11] through O-[11C]methylation
[12] and isolated by a simplified solid-phase extraction
(SPE) purification [13] to produce corresponding pure target
radiolabeled compound [11C]10a or [11C]10b with 40e60%
radiochemical yields, based on [11C]CO2, decay corrected to
end of bombardment (EOB). The large polarity difference be-
tween the acid precursor and the labeled O-methylated ester
product permitted the use of SPE technique for purification
of labeled product from radiolabeling reaction mixture. Either
a light C-18 Sep-Pak cartridge or a semi-prep C-18 guard car-
tridge column was used in SPE purification technique. The re-
action mixture was loaded onto the cartridge by gas pressure.
The cartridge was washed with water to remove non-reacted
[11C]CH3OTf, acid precursor and reaction solvent, and then
2. Results and discussion
2.1. Chemistry
Synthesis of precursors and reference standards was de-
signed and accomplished through chemical modification of
the previously reported procedures [5,6,8]. The synthetic ap-
proach is outlined in Scheme 1. 2-(3-Methoxyphenyl)-1-ethan-
amine (1) was treated with ethyl chloroformate to furnish

M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
2213
O
(i)
(ii)
O
NH
CH3O
NH2
CH3O
NH
O
CH3O
1
2
3
OBn
OBn
(iii)
O
(v)
X
(iv)
ClO4
N
X
N
N
X
CH3O
CH3O
CH3O
4a, X=F
4b, X=Cl
6a, X=F
6b, X=Cl
5a, X=F
5b, X=Cl
(vi)
OH
O
Cl
(vii)
N
X
N
X
CH3O
CH3O
7a, X=F
7b, X=Cl
8a, X=F
8b, X=Cl
O
(viii)
O
N
N
CO2CH3
(ix)
CO2CH3
N
X
N
X
HO
CH3O
10a, X=F
10b, X=Cl
9a, X=F
9b, X=Cl
(x)
O
N
CO2H
N
X
HO
11a, X=F
11b, X=Cl
Scheme 1. Synthesis of tetrahydroisoquinoline derivatives. Reagents and conditions: (i) ClCO2Et, Et3N, CH2Cl2, rt, 5 h. (ii) PPA, 120 ꢀC, 2 h. (iii) ArI, CuI,
K2CO3, DMF, reflux, 4 d. (iv) [LiArOBn] (generated from p-BrArOBn or p-ArOBn and n-BuLi), THF, ꢁ78 ꢀC, 3 h; HClO4, 15 min. (v) MeMgBr, THF, 0 ꢀC
to rt, 3 h. (vi) AlCl3, Me2NPh, CH2Cl2, rt, 1.5 h. (vii) BrCH2CH2Cl, K2CO3, CH3CN, reflux, 3 d; or ClCH2CH2OTs, 2-butanone, K2CO3, reflux, 2 d. (viii) Methyl
piperidine-4-carboxylate, K2CO3, CH3CN, reflux, 3 d. (ix) AlCl3, EtSH, CH2Cl2, 0 ꢀC to rt, 3 h. (x) KOH, MeOH, rt, 12 h, HCl.
final labeled product was eluted with ethanol. Overall synthe-
sis time was 15e20 min from EOB. SPE technique is fast,
efficient and convenient and works very well for the O-meth-
ylated tracer production. The radiosynthesis was performed in
an automated multi-purpose 11C-radiosynthesis module, al-
lowing measurement of specific activity during synthesis
[14,15]. The specific activity was estimated in a range of
74e111 GBq/mmol at the end of synthesis (EOS) based on
other compounds produced using the same targetry conditions
which have been measured by the on-the-fly technique
[15,16]. The actual measurement of specific activity at EOS
by analytical high pressure liquid chromatography (HPLC)
method [17] is in agreement with this estimation. The specific
activity obtained in our automated synthesis module was high,
since the methylation reagent we used was no-carrier-added
(high specific activity) [11C]CH3OTf, which was produced
by the gas-phase production method [11] from [11C]CO2
through [11C]CH4 and [11C]CH3Br with silver triflate (AgOTf)
column. In addition, we used very small amount of the precur-
sor 11a or 11b (0.1e0.3 mg) in radiosynthesis, which also
improved the specific activity data. Chemical purity and radio-
chemical purity were determined by analytical HPLC method.
The chemical purity of precursors and reference standards was
>95%. The radiochemical purity of target tracers was >99%

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M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
O
significantly change their biological activity in light of the
N
structureeactivity relationship (SAR). The preliminary biolog-
ical evaluation of the synthesized new tetrahydroisoquinoline
derivatives 10a,b was performed via an MCF-7 cell prolifera-
tion assay [5,6,20] and compared to 4-hydroxytamoxifen.
4-Hydroxytamoxifen (IC50 8.5 ꢂ 8.0 nM in MCF-7 cells) is
a more potent SERM than its parent compound tamoxifen
(IC50 580 ꢂ 160 nM in MCF-7 cells) [5], and MCF-7 cell
line is an ER positive human breast cancer cell line [21,22].
The results are shown in Fig. 2. As indicated in Fig. 2, prolif-
eration of MCF-7 cells was inhibited by 0.625 nM of 4-
hydroxytamoxifen, also by higher concentrations. MCF-7
cell proliferation was inhibited only by 0.625 nM of compound
10a, but not by higher concentrations. Similar to 4-hydroxyta-
moxifen, proliferation of MCF-7 cells was inhibited by
0.3125e0.625 nM of compound 10b, also by higher concen-
trations. Taken collectively, these results suggest that the
new compounds 10a,b were proved to be potent SERMs
CO211CH3
(i)
11a, X=F
11b, X=Cl
N
X
[
[
11C]10a, X=F
HO
11C]10b, X=Cl
Scheme 2. Synthesis of carbon-11 labeled tetrahydroisoquinoline derivatives.
Reagents and conditions: (i) [11C]CH3OTf, CH3CN, 3 N NaOH.
determined by radio-HPLC through g-ray (NaI) flow detector,
and the chemical purity of target tracers was >95% deter-
mined by reversed-phase HPLC through UV flow detector.
The O-[11C]methylation of phenolic hydroxyl position on
the precursor to form undesired radiolabeled ether byproduct
is a potential competing reaction, however, our previous re-
sults [18] have indicated that the O-[11C]methylation of acid
position on the precursor to form desired radiolabeled ester
product will be a major reaction. These results are consistent
with the theoretical explanation that the deprotonization at
the acid position of the precursor is much easier than at the
phenolic hydroxyl positions of the precursor, since the acidity
of HOe at the acid position of the precursor is greater than at
the phenolic hydroxyl position of the precursor, and the
O-[11C]methylation of the precursor will prefer to occur at
the acid position rather than at the phenolic hydroxyl position.
In addition, the minimal formation of the undesired labeled
byproduct, estimated to be <5%, will be washed out with
non-reacted [11C]CH3OTf, acid precursor and reaction solvent
by water during the SPE purification, since their polarities are
very similar. To prove that alkylation indeed occurred at the
carboxylate-O and not the phenylate-O, a control experiment
was designed and conducted using a previously reported pro-
cedure from our laboratory [19]. Briefly, the precursor 11a or
11b (0.1e0.3 mg) was dissolved in CH3CN (0.5 mL). To this
solution were added 3 N NaOH (2 mL) and 20 mM CH3OTf
(50 mL). The mixture was stirred at room temperature (rt)
for 10 min, and the reaction was monitored by the analytical
HPLC method aforementioned. The results showed that pre-
cursor 11a or 11b was completely converted to compound
10a or 10b, respectively, as indicated by their retention times
(tR 11a ¼ 1.69 min, tR 10a ¼ 4.03 min; and tR 11b ¼ 1.71 min,
tR 10b ¼ 3.06 min) on HPLC chromatograms. These chro-
matographic data support our conclusion.
4-HTX/MCF7 Celltiter96 Proliferation Assay
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
Cell Treatment
10a/MCF7 Celltiter96 Proliferation Assay
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
Cell Treatment
10b/MCF7 Celltiter96 Proliferation Assay
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
2.3. MCF-7 cell proliferation assay
Cell Treatment
Compounds 10a,b were designed and synthesized through
a slight structural modification based on a novel series of tet-
rahydroisoquinoline derivatives, potent SERMs, recently de-
veloped by Renaud et al., which have been fully evaluated
by radioligand binding assay and estrogen response element
(ERE) assay to ERa and ERb, and inhibition of MCF-7 cell
proliferation assay [5,6]. Thus, we can assume that the slight
structural modification of compounds 10a,b would not
Fig. 2. MCF-7 cell proliferation assay of 4-hydroxytamoxifen (4-HTX), and
new tetrahydroisoquinoline derivatives 10a and 10b. The X-axis represents
blank, cell control, carrier and different concentrations (0.156e10 nM) of 4-
HTX and 10a,b, and the Y-axis represents their average inhibition intensity
in MCF-7 cells measured under optical density (OD) 490 nm. Celltiter96 assay
demonstrated that new tetrahydroisoquinoline derivatives 10a and 10b have
similar potencies in the MCF-7 human breast cancer cell line compared to
the reference compound 4-HTX.

M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
2215
with very high binding affinity to ER, comparable to that of the
reference compound 4-hydroxytamoxifen under our assay
conditions.
performed using a Prodigy (Phenomenex) 5 mm C-18 column,
4.6 ꢃ 250 mm; 3:1:3 CH3CN:MeOH:20 mM, pH 6.7 KHPO4ꢁ
(buffer solution) mobile phase; flow rate 1.5 mL/min; and
UV (254 nm) and g-ray (NaI) flow detectors. Light C-18
Sep-Pak cartridges were obtained from Waters Corporate
Headquarters, Milford, MA. Semi-prep C-18 guard cartridge
column 1 ꢃ 1 cm was obtained from E. S. Industries, Berlin,
NJ, and part number 300121-C18-BD 10 mm. Sterile Millex-
GS 0.22 mm vented filter unit was obtained from Millipore
Corporation, Bedford, MA.
3. Conclusion
An efficient and convenient synthesis of new carbon-11 la-
beled tetrahydroisoquinoline derivatives has been well devel-
oped. The synthetic methodology employed classical organic
chemistry such as cyclization, arylation, debenzylation, alkyl-
ation, demethylation and hydrolysis reactions to synthesize
unlabeled tetrahydroisoquinoline derivatives. Carbon-11 label-
ing at oxygen position of the precursor through O-[11C]
methylation was incorporated efficiently using [11C]CH3OTf,
a signature reaction of carbon-11 radiochemistry from our lab-
oratory. Radiosynthesis produced new radioligands in amounts
and purity suitable for the preclinical application in animal
studies using PET. Labeled products are suitable for injection,
with the higher specific radioactivities in a range of 74e
111 GBq/mmol at EOS, and can be obtained within 20 min
from EOB including fast and efficient SPE purification and
formulation. Preliminary findings from in vitro biological as-
say indicate that the synthesized new tetrahydroisoquinoline
derivatives displayed similar potencies in the MCF-7 human
breast cancer cell line in comparison with reference compound
4-hydroxytamoxifen. These results encourage further in vivo
evaluation of carbon-11 labeled tetrahydroisoquinoline deriva-
tives as new potential SERM radioligands for PET imaging of
ER expression in breast cancer.
4.2. Ethyl 3-methoxyphenethylcarbamate (2)
2-(3-Methoxyphenyl)-1-ethanamine (1, 50 g, 330 mmol)
was dissolved in dichloromethane (500 mL) with Et3N
(51 mL, 360 mmol) at 0 ꢀC. Ethyl chloroformate (35 mL,
360 mmol) was added and stirring was continued at rt for 5 h.
The reaction mixture was washed with water (100 mL ꢃ 2),
dried with MgSO4, and filtered. The organic phase was evapo-
rated under reduced pressure to give oily compound 2 (64.0 g,
1
96%), Rf ¼ 0.85 (1:19 MeOH/CH2Cl2). H NMR (CDCl3) d:
1.22 (t, J ¼ 7.0 Hz, 3H, CH3), 2.78 (t, J ¼ 7.0 Hz, 2H,
CH2CH3), 3.40 (dd, J ¼ 7.0, 14.0 Hz, 2H, CH2CH2), 3.79 (s,
3H, OCH3), 4.08 (dd, J ¼ 7.0, 14.0 Hz, 2H, CH2CH2), 4.71
(s, 1H, CONH), 6.74e6.79 (m, 3H, Ph-H), 7.21 (t,
J ¼ 7.8 Hz, 1H, Ph-H).
4.3. 6-Methoxy-3,4-dihydroisoquinolin-1(2H )-one (3)
Compound 2 (30 g, 135 mmol) was treated with polyphos-
phoric acid (PPA, 100 g) at 120 ꢀC under N2 atmosphere for
2 h. After the reaction mixture was cooled down to rt, ice-
water was added (300 mL), and then extracted with EtOAc
(100 mL ꢃ 3) and CH2Cl2 (100 mL ꢃ 2), washed with brine,
and dried with Na2SO4. Combined organic layer was evapo-
rated, and the residue was recrystallized from EtOAc or puri-
fied by column chromatography with silica gel to afford
colorless solid 3 (18.4 g, 77%), mp 136e138 ꢀC, Rf ¼ 0.35
4. Experimental
4.1. General
All commercial reagents and solvents from Aldrich and
Sigma were used without further purification. [11C]CH3OTf
was prepared according to a literature procedure [11]. Melting
points were determined on a MEL-TEMP II capillary tube ap-
paratus and were uncorrected. 1H NMR spectra were recorded
on a Bruker QE 300 NMR spectrometer using tetramethylsi-
lane (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). The low
resolution mass spectra (LRMS) were obtained using a Bruker
Biflex III MALDI-Tof mass spectrometer, and the high resolu-
tion mass spectra (HRMS) were obtained using a Thermo
MAT 95XP-Trap spectrometer. Chromatographic solvent pro-
portions are indicated in a volume:volume ratio. Thin layer
chromatography was run using Analtech silica gel GF uni-
plates (5 ꢃ 10 cm2). Plates were visualized under UV light.
Normal phase flash chromatography was carried out on EM
Science silica gel 60 (230e400 mesh) with a forced flow of
the indicated solvent system in the proportions described
below. All moisture- and/or air-sensitive reactions were per-
formed under a positive pressure of nitrogen maintained by
a direct line from a nitrogen source. Analytical HPLC was
1
(EtOAc). H NMR (CDCl3) d: 2.95 (t, J ¼ 6.6 Hz, 2H, CH2),
3.54 (dt, J ¼ 2.6, 6.6 Hz, 2H, CH2N), 3.84 (s, 3H, OCH3),
6.70 (d, J ¼ 2.6 Hz, 1H, Ph-H), 6.83 (d, J ¼ 2.4 Hz, 1H, Ph-
H), 6.86 (d, J ¼ 2.4 Hz, 1H, Ph-H), 8.02 (d, J ¼ 8.6 Hz, 1H,
NHCO).
4.4. 6-Methoxy-2-(4-flurophenyl)-3,4-dihydro-2H-
isoquinolin-1-one (4a)
A mixture of compound 3 (8.16 g, 46 mmol), 1-fluoro-4-
iodobenzene (20 g, 90 mmol), K2CO3 (6.36 g, 46 mmol), and
CuI (1.75 g, 9.2 mmol) in DMF (90 mL) was heated at
160 ꢀC for 48 h under N2 atmosphere. After that, a second por-
tion of CuI (876 mg, 4.6 mmol) was added, and heating was
continued for another 48 h. Then the mixture was poured
into aqueous NH4OH (350 mL) and EtOAc (350 mL). The
layers were separated, and the aqueous layer was extracted
with EtOAc (350 mL ꢃ 3). The combined organic phases
were washed with brine (500 mL), dried with Na2SO4, and

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M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
concentrated in vacuo until the crystallization started. Hexanes
were added slowly to the solution. The crystallization provided
white solid 4a (11.35 g, 91%), mp 132e134 ꢀC, Rf ¼ 0.29 (1:3
EtOAc/hexanes). 1H NMR (CDCl3) d: 3.09 (t, J ¼ 6.4 Hz, 2H,
CH2), 3.85 (s, 3H, OCH3), 3.92 (t, J ¼ 6.4 Hz, 2H, CH2), 6.71
(d, J ¼ 2.4 Hz, 1H, Ph-H), 6.85 (dd, J ¼ 2.4, 8.6 Hz, 1H, Ph-
H), 7.06 (t, J ¼ 8.6 Hz, 2H, Ph-H), 7.31 (dd, J ¼ 4.8, 9.0 Hz,
2H, Ph-H), 8.05 (d, J ¼ 8.8 Hz, 1H, Ph-H).
4.8. 1-(4-Benzyloxyphenyl)-6-methoxy-2-(4-fluorophenyl)-
1-methyl-1,2,3,4-tetrahydroisoquinoline (6a)
To a cold solution (0 ꢀC) of compound 5a (8.36 g,
19.1 mmol) in anhydrous THF (150 mL) was added a solution
of MeMgBr in Et2O (3.0 M, 11 mL, 33 mmol) over 15 min.
The resultant mixture was stirred at 0 ꢀC for 30 min and was
allowed to warm up to rt. The suspension was poured into sat-
urated aqueous NH4Cl (250 mL) after being stirred for 2 h.
The aqueous layer was extracted with CH2Cl2 (250 mL ꢃ 3).
The combined organic phases were washed with brine
(220 mL), dried with Na2SO4, and concentrated in vacuo.
The crude product was recrystallized from EtOAc/hexanes
or purified by column chromatography with silica gel to
provide white solid 6a (6.49 g, 75%), mp 114e115 ꢀC,
4.5. 6-Methoxy-2-(4-chlorophenyl)-3,4-dihydro-2H-
isoquinolin-1-one (4b)
According to the procedure for preparation of 4a, com-
pound 4b was prepared from compound 3 and 1-chloro-4-
iodobenzene in 90% yield as white solid, mp 169e171 ꢀC,
1
1
Rf ¼ 0.31 (1:3 EtOAc/hexanes). H NMR (CDCl3) d: 3.10 (t,
Rf ¼ 0.82 (1:3 EtOAc/hexanes). H NMR (CDCl3) d: 1.63 (s,
J ¼ 6.4 Hz, 2H, CH2), 3.86 (s, 3H, OCH3), 3.94 (t,
J ¼ 6.4 Hz, 2H, CH2), 6.72 (d, J ¼ 2.4 Hz, 1H, Ph-H), 6.86
(dd, J ¼ 2.4, 8.8 Hz, 2H, Ph-H), 7.25e7.39 (m, 4H, Ph-H),
8.06 (d, J ¼ 8.8 Hz, 1H, Ph-H).
3H, CH3), 2.85e3.13 (m, 2H, CH2), 3.21e3.42 (m, 2H,
CH2), 3.78 (s, 3H, OCH3), 5.03 (s, 2H, OCH2), 6.50e6.83
(m, 9H, Ph-H), 7.03 (d, J ¼ 8.8 Hz, 2H, Ph-H), 7.31e7.41
(m, 5H, Ph-H).
4.6. 1-(4-(Benzyloxy)phenyl)-2-(4-fluorophenyl)-6-
methoxy-3,4-dihydro-2H-isoquinolinium (5a)
4.9. 1-(4-Benzyloxyphenyl)-6-methoxy-2-
(4-chlorophenyl)-1-methyl-1,2,3,4-
tetrahydroisoquinoline (6b)
To a cold solution (ꢁ78 ꢀC) of 4-benzyloxybromobenzene
(6.7 g, 25.4 mmol) in anhydrous THF (70 mL) was added a so-
lution of n-BuLi (2.5 M, 11.2 mL, 28 mmol) over a period of
30 min. After the resultant suspension was stirred at ꢁ78 ꢀC
for 40 min, a solution of compound 4a (5.2 g, 19.1 mmol) in
anhydrous THF (100 mL) was added over 30 min. Stirring
was continued for 50 min. The reaction mixture was poured
into water (220 mL) and EtOAc (220 mL). HClO4 (70%,
5.0 mL) was added, and the mixture was stirred for 20 min.
The pH value of aqueous layer was adjusted to 5 by addition
of aqueous NaHCO3. The layers were separated, and the aque-
ous layer was extracted with EtOAc (180 mL ꢃ 3). The com-
bined organic layers were washed with brine (220 mL) and
dried with MgSO4, and the solution was concentrated in vacuo
to obtain yellowish solid 5a (8.36 g, 100%), which was used
directly in the next step without further purification, mp
133e135 ꢀC, Rf ¼ 0.62 (1:9 CH3OH/CH2Cl2). 1H NMR
(CDCl3) d: 3.45 (t, J ¼ 7.5 Hz, 2H, CH2), 3.95 (s, 3H,
OCH3), 4.54 (t, J ¼ 7.5 Hz, 2H, CH2), 5.05 (s, 2H, OCH2Ph),
6.81e7.05 (m, 6H, Ph-H), 7.24 (t, J ¼ 2.4 Hz, 2H, Ph-H), 7.28
(d, J ¼ 2.4 Hz, 1H, Ph-H), 7.34e7.40 (m, 7H, Ph-H). MS
(ESI): 438 (Mþ, 100%).
According to the procedure for preparation of 6a, com-
pound 6b was prepared from compound 5b in 73% yield as
white solid, mp 148e150 ꢀC, Rf ¼ 0.81 (1:3 EtOAc/hexanes).
1H NMR (CDCl3) d: 1.64 (s, 3H, CH3), 2.89 9 (dt, J ¼ 4.4,
16.2 Hz, 1H, CHH), 3.16 (ddd, J ¼ 4.4, 9.6, 15.1 Hz, 1H,
CHH ), 3.30e3.37 (m, 1H, CHH), 3.41e3.49 (m, 1H,
CHH ), 3.77 (s, 3H, OCH3), 5.03 (s, 2H, OCH2), 6.49 (d,
J ¼ 8.9 Hz, 1H, Ph-H), 6.61e6.71 (m, 3H, Ph-H), 6.80 (d,
J ¼ 8.9 Hz, 2H, Ph-H), 6.98 (d, J ¼ 8.8 Hz, 2H, Ph-H), 7.08
(d, J ¼ 8.6 Hz, 2H, Ph-H), 7.32e7.45 (m, 5H, Ph-H).
4.10. 4-[6-Methoxy-2-(4-fluorophenyl)-1-methyl-1,2,3,4-
tetrahydroisoquinolin-yl]phenol (7a)
A solution of compound 6a (5.38 g, 11.86 mmol), AlCl3
(4.74 g, 35.58 mmol) and Me2NPh (14.3 g, 118.6 mmol) in
CH2Cl2 (270 mL) was stirred at rt for 1.5 h. Water (90 mL)
and CH2Cl2 (350 mL) were added to the reaction mixture,
and the pH value of aqueous layer was adjusted to 5 with
aqueous NaHCO3. The layer was separated, aqueous layer
was extracted with CH2Cl2 (250 mL ꢃ 2) and then EtOAc
(280 mL ꢃ 3). The combined organic phases were washed
with brine, dried with MgSO4, and concentrated in vacuo.
The resultant oil was purified by column chromatography
with silica gel to afford white solid product 7a (3.01 g,
70%), mp 56e57 ꢀC, Rf ¼ 0.47 (1:3 EtOAc/hexanes). 1H
NMR (CDCl3) d: 1.63 (s, 3H, CH3), 2.87 (dt, J ¼ 4.4,
15.8 Hz, 1H, CHH), 3.06e3.19 (m, 1H, CHH ), 3.21e3.48
(m, 2H, CH2), 3.78 (s, 3H, OCH3), 4.96 (s, 1H, OH), 6.51e
6.61 (m, 2H, Ph-H), 6.65e6.79 (m, 7H, Ph-H), 6.98 (d,
J ¼ 8.8 Hz, Ph-H).
4.7. 1-(4-(Benzyloxy)phenyl)-2-(4-chlorophenyl)-6-
methoxy-3,4-dihydro-2H-isoquinolinium (5b)
According to the procedure for preparation of 5a, com-
pound 5b was prepared from compound 4b in 100% yield as
yellowish solid, mp 154e156 ꢀC, Rf ¼ 0.64 (1:9 CH3OH/
1
CH2Cl2). H NMR (CDCl3) d: 3.44 (t, J ¼ 7.4 Hz, 2H, CH2),
3.94 (s, 3H, OCH3), 4.53 (t, J ¼ 7.4 Hz, 2H, CH2), 5.05 (s,
2H, OCH2Ph), 6.80e6.96 (m, 4H, Ph-H), 7.22e7.31 (m, 7H,
Ph-H), 7.36e7.42 (m, 5H, Ph-H). MS (ESI): 454 (Mþ, 100%).

M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
2217
4.11. 4-[6-Methoxy-2-(4-chlorophenyl)-1-methyl-1,2,3,4-
tetrahydroisoquinolin-yl]phenol (7b)
give white solid 9a (980 mg, 92%), mp 104e106 ꢀC,
1
Rf ¼ 0.34 (1:1 EtOAc/hexanes). H NMR (CDCl3) d: 1.63 (s,
3H, CH3), 1.75e1.93 (m, 4H), 2.13e2.36 (m, 3H), 2.77 (t,
J ¼ 6.0 Hz, 2H, NCH2), 2.87e2.99 (m, 3H), 3.11e3.41 (m,
3H), 3.67 (s, 3H, OCH3), 3.78 (s, 3H, OCH3), 4.06 (t,
J ¼ 6.0 Hz, 2H, OCH2), 6.50e6.57 (m, 2H, Ph-H), 6.60e6.78
(m, 7H, Ph-H), 7.01 (d, J ¼ 8.8 Hz, Ph-H). MS (CI): 533
([M þ H]þ, 100%), 532 (Mþ, 48%). HRMS (CI): calcd for
C32H38O4N2F, 533.2810, found, 533.2816.
According to the procedure for preparation of 7a, com-
pound 7b was prepared from compound 6b in 72% yield as
white solid, mp 110e112 ꢀC, Rf ¼ 0.48 (1:3 EtOAc/hexanes).
1H NMR (CDCl3) d: 1.64 (s, 3H, CH3), 2.86 (dt, J ¼ 4.0,
15.6 Hz, 1H, CHH), 3.08e3.21 (m, 1H, CHH ), 3.28e3.51
(m, 2H, CH2), 3.78 (s, 3H, OCH3), 4.71 (1H, OH), 6.50 (d,
J ¼ 8.8 Hz, 2H, Ph-H), 6.60e6.74 (m, 5H, Ph-H), 6.98e7.06
(m, 4H, Ph-H).
4.15. Methyl 1-(2-(4-(2-(4-chlorophenyl)-6-methoxy-1-
methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)-
piperidine-4-carboxylate (9b)
4.12. 1-(4-(2-Chloroethoxy)phenyl)-2-(4-fluorophenyl)-
6-methoxy-1-methyl-1,2,3,4-tetrahydroisoquinoline (8a)
According to the procedure for preparation of 9a, com-
pound 9b was prepared from compound 8b in 91% yield as
white solid, mp 76e78 ꢀC, Rf ¼ 0.33 (1:1 EtOAc/hexanes).
1H NMR (CDCl3) d: 1.64 (s, 3H, CH3), 1.75e1.94 (m, 4H),
2.12e2.36 (m, 3H), 2.78 (t, J ¼ 5.8 Hz, 2H, NCH2), 2.86e
2.99 (m, 3H), 3.11e3.23 (m, 1H), 3.28e3.49 (m, 2H), 3.67
(s, 3H, OCH3), 3.77 (s, 3H, OCH3), 4.06 (t, J ¼ 5.8 Hz, 2H,
OCH2), 6.48 (d, J ¼ 8.8 Hz, 2H, Ph-H), 6.60e6.64 (m,
2H, Ph-H), 6.69e6.75 (m, 2H, Ph-H), 6.98 (d, J ¼ 8.8 Hz,
2H, Ph-H), 7.05 (d, J ¼ 8.8 Hz, 2H, Ph-H). MS (CI): 549
([M þ H]þ, 100%), 548 (Mþ, 48%). HRMS (CI): calcd for
C32H38O4N2Cl, 549.2515, found, 549.2502.
Method A: a solution of compound 7a (363 mg, 1 mmol), 1-
bromo-2-chloroethane (789 mg, 5 mmol) and K2CO3 (207 mg,
1.5 mmol) in CH3CN (50 mL) was heated to reflux for 3 days.
The reaction mixture was filtered, and concentrated. The res-
idue was purified by column chromatography with silica gel to
give white solid 8a (221 mg, 52%). Method B: a solution of
compound 7a (1.82 g, 5 mmol), 2-chloroethyl 4-methylbenze-
nesulfonate (1.76 g, 7.5 mmol) and K2CO3 (1.38 g, 10 mmol)
in 2-butanone (120 mL) was heated to reflux for 3 days. The
reaction mixture was filtered, and concentrated. The residue
was purified by column chromatography with silica gel to
give white solid 8a (1.44 g, 68%), mp 119e121 ꢀC, Rf ¼ 0.78
(1:3 EtOAc/hexanes). 1H NMR (CDCl3) d: 1.63 (s, 3H,
CH3), 2.87 (dt, J ¼ 4.4, 15.6 Hz, CHH), 3.07e3.23 (m, 1H,
CHH ), 3.26e3.47 (m, 2H, CH2), 3.78 (s, 3H, OCH3), 3.80 (t,
J ¼ 6.0 Hz, 2H, CH2Cl), 4.20 (t, J ¼ 6.0 Hz, 2H, CH2O),
6.51e6.64 (m, 4H, Ph-H), 6.69e6.79 (m, 5H, Ph-H), 7.04 (d,
J ¼ 8.8 Hz, 2H, Ph-H).
4.16. Methyl 1-(2-(4-(2-(4-fluorophenyl)-6-hydroxy-1-
methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)-
piperidine-4-carboxylate (10a)
To a cold solution (0 ꢀC) of compound 9a (212 mg,
0.4 mmol) and EtSH (0.3 mL) in CH2Cl2 (15 mL) was added
AlCl3 (213 mg, 1.6 mmol). The mixture was stirred at 0 ꢀC
for 1 h, and then at rt for 3 h. The reaction was quenched by
adding some water, and the pH value of the solution was
adjusted to 6 with aqueous NaHCO3. Then the mixture was
extracted with CH2Cl2 (100 mL ꢃ 3). The combined organic
layers were washed with brine, dried with MgSO4, and con-
centrated in vacuo. The residue was purified by column chro-
matography with silica gel to afford white solid 10a (85 mg,
41%), mp 95e97 ꢀC, Rf ¼ 0.76 (1:9 CH3OH/CH2Cl2). 1H
NMR (CD3OD) d: 1.62 (s, 3H, CH3), 1.83e2.00 (m, 5H),
2.40e2.50 (m, 3H), 2.78e2.98 (m, 3H), 3.09e3.22 (m, 3H),
3.26e3.41 (m, 1H), 3.67 (s, 3H, OCH3), 4.14 (t, J ¼ 6.0 Hz,
2H, OCH2), 6.49e6.64 (m, 5H, Ph-H), 6.70e6.79 (m, 4H,
Ph-H), 7.03 (d, J ¼ 8.8 Hz, 2H, Ph-H). MS (ESI): 519
([M þ H]þ, 100%). HRMS (CI): calcd for C31H36O4N2F,
519.2654, found, 519.2643.
4.13. 1-(4-(2-Chloroethoxy)phenyl)-2-(4-chlorophenyl)-
6-methoxy-1-methyl-1,2,3,4-tetrahydroisoquinoline (8b)
According to the Method B for preparation of 8a, com-
pound 8b was prepared from compound 7b in 66% yield as
white solid, mp 138e140 ꢀC, Rf ¼ 0.78 (1:3 EtOAc/hexanes).
1H NMR (CDCl3) d: 1.64 (s, 3H, CH3), 2.88 (dt, J ¼ 4.4,
15.4 Hz, 1H, CHH), 3.12e3.21 (m, 1H, CHH ), 3.30e3.49
(m, 2H, CH2), 3.78 (s, 3H, OCH3), 3.80 (t, J ¼ 5.9 Hz, 2H,
CH2Cl), 4.20 (t, J ¼ 5.9 Hz, OCH2), 6.50 (d, J ¼ 8.8 Hz,
2H, Ph-H), 6.60e6.64 (m, 3H, Ph-H), 6.77 (d, J ¼ 8.8 Hz,
2H, Ph-H), 7.02 (d, J ¼ 8.8 Hz, 2H, Ph-H), 7.12 (d, J ¼
8.8 Hz, 2H, Ph-H).
4.14. Methyl 1-(2-(4-(2-(4-fluorophenyl)-6-methoxy-1-
methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)-
piperidine-4-carboxylate (9a)
4.17. Methyl 1-(2-(4-(2-(4-chlorophenyl)-6-hydroxy-1-
methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)-
piperidine-4-carboxylate (10b)
A solution of compound 8a (852 mg, 2 mmol), methyl piper-
idine-4-carboxylate (572 mg, 4 mmol) and K2CO3 (691 mg,
5 mmol) in CH3CN (60 mL) was heated to reflux for 3 days.
The reaction mixture was filtered, and concentrated. The resi-
due was purified by column chromatography with silica gel to
According to the procedure for preparation of 10a, com-
pound 10b was prepared from compound 9b in 36% yield as
white solid, mp 72e74 ꢀC, Rf ¼ 0.76 (1:9 CH3OH/CH2Cl2).

2218
M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
1H NMR (CD3OD) d: 1.63 (s, 3H, CH3), 1.72e1.95 (m, 4H),
2.21e2.44 (m, 4H), 2.79e2.87 (m, 3H), 2.99e3.05 (m, 3H),
3.34e3.45 (m, 1H), 3.67 (s, 3H, OCH3), 4.09 (t, J ¼ 5.8 Hz,
2H, OCH2), 6.43e6.60 (m, 5H, Ph-H), 7.74 (d, J ¼ 8.8 Hz,
2H, Ph-H), 6.95 (d, J ¼ 8.8 Hz, 2H, Ph-H), 7.06 (d,
J ¼ 8.8 Hz, 2H, Ph-H). MS (ESI): 535 ([M þ H]þ, 100%).
HRMS (CI): calcd for C31H36O4N2Cl, 535.2358, found,
535.2349.
RDS-111). The acid precursor 11a or 11b (0.1e0.3 mg) was
dissolved in CH3CN (300 mL). To this solution was added
3 N NaOH (2 mL). The mixture was transferred to a small re-
action vial. [11C]CH3OTf that was produced from [11C]CO2
through [11C]CH4 and [11C]CH3Br with AgOTf column was
passed into the reaction vial, which was cooled to 0 ꢀC, until
radioactivity reached a maximum (w2 min), and then the
reaction vial was isolated and heated at 80 ꢀC for 3 min. The
contents of the reaction vial were diluted with NaHCO3
(1 mL, 0.1 M). The reaction tube was connected to either
a light C-18 Sep-Pak cartridge or a semi-prep C-18 guard car-
tridge column. The labeled product mixture solution was
passed onto the cartridge for SPE purification by gas pressure.
The cartridge was washed with H2O (3 mL ꢃ 2), and the aque-
ous washing was discarded. The product was eluted from the
column with EtOH (3 mL ꢃ 2), and then passed onto a rotatory
evaporator. The solvent was removed by evaporation under
vacuum. The labeled product [11C]10a or [11C]10b was for-
mulated with saline, sterile-filtered through a sterile vented
Millex-GS 0.22 mm cellulose acetate membrane and collected
into a sterile vial, whose volume was dependent upon the use
of the labeled product in tissue biodistribution studies
(w6 mL, 2 mL ꢃ 3) or in PET imaging studies (1e3 mL).
Total radioactivity was assayed and the total volume (1.0e
6.0 mL) was noted. The overall synthesis time including
SPE purification and formulation was 15e20 min. The radio-
chemical yields were 40e60% decay corrected to EOB from
[11C]CO2 and 20e30% at EOS, respectively. Retention times
in the analytical HPLC system were: tR 11a ¼ 1.69 min, tR
10a ¼ 4.03 min, tR [11C]10a ¼ 4.03 min; and tR 11b ¼
1.71 min, tR 10b ¼ 3.06 min, tR [11C]10b ¼ 3.06 min.
4.18. 1-(2-(4-(2-(4-Fluorophenyl)-6-hydroxy-1-methyl-
1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)-
piperidine-4-carboxylic acid (11a)
A solution of compound 10a (52 mg, 0.1 mmol), potassium
hydroxide (56 mg, 1 mmol) and methanol (15 mL) was stirred
at rt for 12 h. The mixture was evaporated in vacuo, added wa-
ter (5 mL) and adjusted pH to 5e6 with 1 N HCl. The mixture
solution was extracted with EtOAc (50 mL ꢃ 3), washed with
brine, dried with MgSO4, and concentrated in vacuo. The res-
idue was purified by column chromatography to give yellow
compound 11a (44 mg, 88%), mp 185e187 ꢀC, Rf ¼ 0.40
(2:1 CH3OH/CH2Cl2). 1H NMR (CD3OD) d: 1.62 (s, 3H,
CH3), 1.80e2.02 (m, 4H), 2.19e2.31 (m, 1H), 2.53e2.63
(m, 3H), 2.80e2.88 (m, 1H), 2.98e3.01 (m, 3H), 3.20e3.46
(m, 3H), 4.18 (t, J ¼ 5.6 Hz, 2H, OCH2), 6.44e6.61 (m, 4H,
Ph-H), 6.63e6.87 (m, 5H, Ph-H), 7.03 (d, J ¼ 8.8 Hz, Ph-
H). MS (ESI): 505 ([M þ H]þ, 100%). HRMS (CI): calcd
for C30H34O4N2F, 505.2497, found, 505.2503.
4.19. 1-(2-(4-(2-(4-Chlorophenyl)-6-hydroxy-1-methyl-
1,2,3,4-tetrahydroisoquinolin-1-yl)phenoxy)ethyl)-
piperidine-4-carboxylic acid (11b)
4.21. MCF-7 cell proliferation assay
According to the procedure for preparation of 11a, com-
pound 11b was prepared from compound 10b in 86% yield
as yellow solid, mp 174e176 ꢀC, Rf ¼ 0.40 (2:1 CH3OH/
MCF-7 cell proliferation assay was performed following
a literature procedure [20]. Briefly, cell proliferation was per-
formed using Celltiter96 kits. For proliferation assays, 100 mL
of medium containing 5000 MCF-7 breast cancer cells was
plated in a 96-well flat-bottom microplate (Becton Dickinson
& Co., Lincoln Park, NJ) and was incubated at 37 ꢀC for
24 h in the presence of 0.156e10 nM of reference compound
4-hydroxytamoxifen, and synthesized new compounds 10a,b.
Following treatment, 20 mL of the reagent, the tetrazolium
compound MTS (Promega, Madison, WI), was added to
each well, and incubation was continued at 37 ꢀC for 1 h.
The absorbance was measured at a wavelength of 490 nm.
Control cells were not incubated with 4-hydroxytamoxifen
and 10a,b. Each series was performed in triplicate.
1
CH2Cl2). H NMR (CD3OD) d: 1.65 (s, 3H, CH3), 1.86e2.06
(m, 5H), 2.26e2.34 (m, 1H), 2.78e2.88 (m, 5H), 3.19e3.45
(m, 4H), 4.24 (t, J ¼ 5.2 Hz, OCH2), 6.43e6.62 (m, 5H, Ph-
H), 6.80 (d, J ¼ 8.8 Hz, 2H, Ph-H), 9.96 (d, J ¼ 8.8 Hz, 2H,
Ph-H), 7.11 (d, J ¼ 8.8 Hz, 2H, Ph-H), 7.97 (s, 1H, OH). MS
(ESI): 521 ([M þ H]þ, 100%). HRMS (CI): calcd for
C30H34O4N2Cl, 521.2202, found, 521.2216.
4.20. General method for the preparation of carbon-11
labeled tetrahydroisoquinoline derivatives, [11C]methyl
1-(2-(4-(2-(4-fluorophenyl)-6-hydroxy-1-methyl-1,2,3,4-
tetrahydroisoquinolin-1-yl)phenoxy)ethyl)piperidine-4-
carboxylate ([11C]10a) and [11C]methyl 1-(2-(4-(2-
(4-chlorophenyl)-6-hydroxy-1-methyl-1,2,3,4-
Acknowledgments
tetrahydroisoquinolin-1-yl)phenoxy)ethyl)piperidine-4-
carboxylate ([11C]10b)
This work was partially supported by the Susan G. Komen
for the Cure grant BCTR0504022, Breast Cancer Research
Foundation, and Indiana Genomics Initiative (INGEN) of Indi-
ana 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]CO2 was produced by the 14N(p,a)11C nuclear reac-
tion in small volume (9.5 cm3) aluminum gas target (CTI)
from 11 MeV proton cyclotron on research purity nitrogen
(þ1% O2) in a Siemens radionuclide delivery system (Eclipse

M. Gao et al. / European Journal of Medicinal Chemistry 43 (2008) 2211e2219
2219
[11C]CH3OTf. The referees’ criticisms and editor’s comments
for the revision of the manuscript are greatly appreciated.
[9] X. Fei, J.-Q. Wang, K.D. Miller, G.W. Sledge, G.D. Hutchins, Q.-H. Zheng,
Nucl. Med. Biol. 31 (2004) 1033e1041.
[10] D.M. Jewett, Appl. Radiat. Isot. 43 (1992) 1383e1385.
[11] B.H. Mock, G.K. Mulholland, M.T. Vavrek, Nucl. Med. Biol. 26 (1999)
467e471.
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