Synthesis and biological evaluation of [18F]bicalutamide, 4-[76Br]bromobicalutamide, and 4-[76Br]bromo- thiobicalutamide as non-steroidal androgens for prostate cancer imaging

Article abstract of DOI:10.1021/jm060847r

Androgen receptors (AR) are overexpressed in most primary and metastatic prostate cancers. To develop a nonsteroidal AR-mediated imaging agent, we synthesized and radiolabeled several analogs of the potent antiandrogen bicalutamide: [¹⁸F]bicalutamide, 4-[⁷⁶Br] bromobicalutamide, and [⁷⁶Br]bromo-thiobicalutamide. Two of these analogs, 4-[⁷⁶Br]bromobicalutamide and [⁷⁶Br]bromo- thiobicalutamide, were found to have a substantially increased affinity for the androgen receptor (AR) compared to that of bicalutamide. The synthesis of [ ¹⁸F]bicalutamide utilized a pseudocarrier approach to effect addition of a carbanion generated from tracer-level amounts of a radiolabeled precursor to an unlabeled carbonyl precursor. 4-[⁷⁶Br]Bromobicalutamide and [⁷⁶Br]bromo-thiobicalutamide were labeled through electrophilic bromination of a tributylstannane precursor. The former could be prepared in high specific activity, and its tissue distribution was tested in vivo. Androgen target tissue uptake was evident in castrated adult male rats; however, in DES-treated, AR-positive, tumor-bearing male mice, tumor uptake was low.

Full text of DOI:10.1021/jm060847r

1028
J. Med. Chem. 2007, 50, 1028-1040
Synthesis and Biological Evaluation of [18F]Bicalutamide, 4-[76Br]Bromobicalutamide, and
4-[76Br]Bromo-thiobicalutamide as Non-Steroidal Androgens for Prostate Cancer Imaging
Ephraim E. Parent,† Carmen S. Dence,‡ Carl Jenks,‡ Terry L. Sharp,‡ Michael J. Welch,‡ and John A. Katzenellenbogen*,†
Department of Chemistry, UniVersity of Illinois, 600 South Mathews AVenue, Urbana, Illinois 61801, and Washington UniVersity School of
Medicine, Saint Louis, Missouri 63110
ReceiVed July 19, 2006
Androgen receptors (AR) are overexpressed in most primary and metastatic prostate cancers. To develop a
nonsteroidal AR-mediated imaging agent, we synthesized and radiolabeled several analogs of the potent
antiandrogen bicalutamide: [18F]bicalutamide, 4-[76Br]bromobicalutamide, and [76Br]bromo-thiobicalutamide.
Two of these analogs, 4-[76Br]bromobicalutamide and [76Br]bromo-thiobicalutamide, were found to have a
substantially increased affinity for the androgen receptor (AR) compared to that of bicalutamide. The synthesis
of [18F]bicalutamide utilized a pseudocarrier approach to effect addition of a carbanion generated from
tracer-level amounts of a radiolabeled precursor to an unlabeled carbonyl precursor. 4-[76Br]Bromobicaluta-
mide and [76Br]bromo-thiobicalutamide were labeled through electrophilic bromination of a tributylstannane
precursor. The former could be prepared in high specific activity, and its tissue distribution was tested in
vivo. Androgen target tissue uptake was evident in castrated adult male rats; however, in DES-treated,
AR-positive, tumor-bearing male mice, tumor uptake was low.
Introduction
imaging agents that are close structural analogs of the nonste-
roidal antiandrogen compounds used in second-line hormone
therapy, namely, flutamide and bicalutamide, might be particu-
larly useful because failure of these agents generally presages
the onset of unmanageable disease. The development of effective
PET imaging agents based on such nonsteroidal androgens,
however, has proved to be a challenge.16-18
Prostate cancer is the second leading cause of cancer death
in men in the United States,1 and it has been directly linked to
the androgen receptor (AR)a in most cases. Androgen ablation
monotherapy, surgical or chemical castration with nonsteroidal
antiandrogens such as flutamide (1) and bicalutamide (2), is
the principal initial treatment for progressive prostate cancer
and results in the regression of most androgen-dependent
tumors.2 Many men eventually fail androgen ablation therapy,
however, and die of recurrent androgen-independent prostate
cancer (AIPC).
In our efforts to develop agents for the in vivo imaging of
androgen receptor (AR) in prostate cancers by positron emission
tomography (PET), we and others have prepared steroidal3-5
and nonsteroidal6,7 AR ligands labeled with fluorine-18. Several
of these 18F-labeled steroidal androgens show tissue distribution
in chemically castrated rats that is consistent with their uptake
by an AR-dependent process, namely, selective target tissue
(prostate) accumulation that is effectively blocked by coadmin-
istration of a blocking dose of unlabeled androgen.3,5 One of
the agents we have developed, 16â-[18F]fluoro-5R-dihydrotes-
tosterone (FDHT), has proved to be an effective agent for PET
imaging of AR-positive prostate tumors in humans.8,9
The nonsteroidal antiandrogen bicalutamide is the leading
antiandrogen used for the treatment of prostate cancer. Non-
steroidal antiandrogens, such as flutamide and bicalutamide, are
often referred to as “pure antiandrogens” because they bind
exclusively to the AR and, therefore, are devoid of antigona-
dotropic, antiestrogenic, and progestational effects (Figure 1).19
Bicalutamide is a racemic mixture,20,21 with the R enantiomer
having 30-fold higher binding affinity than the S isomer.22 In
this study, we describe the syntheses of 18F and 76Br-labeled
androgen receptor ligands based on the bicalutamide core:
[18F]bicalutamide, 4-[76Br]bromobicalutamide, and [76Br]bromo-
thiobicalutamide, the last being based on thiobicalutamide, a
bicalutamide analog reported to have improved AR binding
affinity.23 We determined the AR binding affinity of these
compounds and related analogs, and we determined the meta-
bolic stability and tissue biodistribution of 4-[76Br]bromobi-
calutamide in rats and tumor-bearing mice.
Despite androgen deprivation therapy, most patients will
experience disease progression to AIPC,10 a stage at which only
a small fraction of tumors respond to secondary hormonal
therapies, including treatment with nonsteroidal antiandrogens.11
In fact, at this stage treatment with an antiandrogen often leads
to increased tumor growth.12-14 Although the cause of this
antiandrogen activation is not known, it is believed to be due
to changes in the androgen signaling cascade.15 Therefore, PET
Results
Chemistry. Linear Synthesis of Bicalutamide (1). Our first
attempt to develop a synthesis of bicalutamide suitable for
radiolabeling involved a linear synthetic route, shown in Scheme
1. 4-Cyano-3-trifluoromethyl-aniline (5) was condensed with
pyruvic acid chloride24 to produce ketoamide 6 in 27% yield.21
The keto moiety of 6 was attacked by the anion of amine 12,25
which was formed using either lithium diisopropyl amide (LDA)
or n-BuLi, to afford anilide 7 in 30%. Anilide 7 was protected
with acetyl chloride to give the corresponding ester (8),26 and
then N-methylated with methyl trifluoromethanesulfonate27,28
to form the ammonium salt 9 in 53% and 66% yields,
respectively.
* Corresponding author. Phone: 217-333-6310. E-mail: jkatzene@uiuc.edu.
† University of Illinois.
‡ Washington University School of Medicine.
a Abbreviations: AR, androgen receptor; AIPC, androgen-independent
prostate cancer; PET, positron emission tomography; FDHT, 16â-[18F]-
fluoro-5R-dihydrotestosterone; LDA, lithium diisopropyl amide; TBAF,
tetrabutylammonium fluoride; RBA, relative binding affinity; DHT, dihy-
drotestosterone.
10.1021/jm060847r CCC: $37.00 © 2007 American Chemical Society
Published on Web 01/20/2007

Non-Steroidal Androgens for Prostate Cancer Imaging
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5 1029
lipophilic and thus is readily separable from bicalutamide by
HPLC under reverse-phase conditions.
The pseudocarrier t-butylphenyl methyl sulfone (16) was
synthesized from 4-(t-butyl)phenyl mercaptan (15) in two steps
and in 75% yield, as shown in Scheme 3.35,36 This analog was
then treated with n-BuLi to generate the corresponding anion,
which reacted with keto amide 6 to afford the t-butyl analog of
bicalutamide (17) in 28%. The overall yield of this sequence
was 21%. This approach was investigated for the preparation
of fluorine-18 labeled material (below).
Synthesis of 4-Bromobicalutamide (19). The difficulty in
synthesizing no-carrier-added [18F]bicalutamide encouraged us
to examine the properties of some bromine analogs of bicaluta-
mide: 4-bromobicalutmaide (19) and 4-bromo-thiobicalutamide
(23). Bromine has several properties that make it a synthetically
appealing element for radiolabeling. Bromide ion can be easily
oxidized to create hypobromite, using either a peracid37,38 or
chloramine-T,39,40 and this electrophilic bromination species can
be incorporated into a variety of aromatic rings.41 Thus, we
found peracid oxidation of bromide ion to be an extremely
efficient and reliable method for incorporating this halogen into
the aforementioned sulfone-activated ring on suitable precursors
(Scheme 4).
An authentic sample of 4-bromobicalutamide was synthesized
as shown in Scheme 4. Bromophenyl sulfone 18 was treated
with n-BuLi to form the corresponding anion, which was then
reacted with ketoamide 6 to form 4-bromobicalutamide (19) in
78% yield. Palladium coupling with bis-(tributyltin)42 gave in
28% yield the precursor 20 suitable for radiolabeling. Am-
monium bromide was oxidized to hypobromite in a solution of
10% HOOAc/HOAc,41 and this electrophile was then used to
effect an aryl destannylation reaction with the tin precursor (20),
reforming the desired final product (19) in 84% yield. The
overall yield of 4-bromobicalutamide by this approach was 18%.
This route was also investigated for preparing radiolabeled
material (below).
Synthesis of 4-Bromo-thiobicalutamide (23). The ease with
which 4-bromobicalutamide could be prepared by this route
encouraged us to also explore the possibility of labeling 4
-bromo-thiobicalutamide. Thiobicalutamide (2) is reported to
have a 10-fold higher binding affinity for the AR than its sulfone
analog, bicalutamide.23 4-Bromo-thiobicalutamide was synthe-
sized as shown in Scheme 5.
Primary amine 5 was condensed with methacroyl chloride
to form the acrylanilide 21,43 which was then treated with
performic acid to afford the epoxide 2244 in 59% and 88%
yields, respectively. Epoxide 22 was reacted with 4-bromo-
thiophenol to give 4-bromo-thiobicalutamide 23 in 61% yield.44
4-Bromo-thiobicalutamide 23 underwent palladium-mediated
coupling to form alkyl tin 24 in a 12% yield. Labeling precursor
24 reacted readily with hypobromite, formed by oxidation of
NH4Br in 1.6% HOOAc/HOAc, to give a mixture of the
sulfoxide 25 and sulfone 19.
Figure 1. Bicalutamide and other nonsteroidal anilide AR antagonists.
Whereas treatment of the labeling precursor 9 with either
tetrabutylammonium fluoride (TBAF), KF/kryptofix[2.2.2], or
CsF/ionic liquid, did result in the incorporation of fluorine into
the desired sulfone activated ring, it simultaneously led to the
unwanted formation of isomeric alkene by products 10ab.29,30
These elimination products are believed to arise from the
deprotonation of the anilide nitrogen of 9 by fluoride, producing
a reactive amide anion that extracts a hydrogen vicinal to the
acetate ester to furnish the observed alkene products. Several
attempts were made either to protect the anilide nitrogen or to
change the acetate protecting group to prevent this undesired
elimination reaction; however, in none of these cases were we
successful in producing a labeling precursor that did not undergo
this side reaction. Additionally, although there are literature
reports of using a sulfonyl substituent to activate the displace-
ment of a nitro group at a para position,31-33 we were unable
to achieve fluoride ion displacement of either the nitro analog
of ammonium salt 9 or the nitro group in 4-nitrophenyl methyl
sulfone itself.
Convergent Synthesis of Bicalutamide (1). Because of these
complications, the linear synthesis of [18F]bicalutamide was
abandoned in favor of an alternative, convergent approach
(Scheme 2), in the hope that protection and elimination of the
hydroxyl group could be avoided. Methyl sulfone 11 was treated
with iodomethane to produce dimethylamine 12 in 89% yield.34
The ammonium salt (13) was produced by the reaction of amine
12 with methyl trifluoromethanesulfonate in 31% yield.27
Treatment of labeling precursor 13 with TBAF yielded the
fluorophenyl sulfone 14 in 87% yield.29 This product was
deprotonated using n-BuLi at -78 °C and then combined with
keto amide 6 to form bicalutamide in 95% yield. This synthesis
proceeded in an overall yield of 23%, and the bicalutamide
produced by this approach was found to be identical to an
authentic commercially available sample by HPLC and NMR.
Use of this synthetic route at the tracer level, however, was
unsuccessful because we were unable to get tracer levels of [18F]-
fluorophenyl sulfone (18F-14) to react with ketoamide 6.
Because of problems encountered in the tracer-level radio-
chemical synthesis of 4-[18F]bicalutamide using this convergent
synthesis, we modified our synthetic route to include a
pseudocarrier. Pseudocarriers are often beneficial to a synthesis
when a reactive intermediate generated from tracer levels of
the radiolabeled component undergoes quenching from adventi-
tious water, which appeared to be the case here with the anion
derived from the [18F]fluorophenyl sulfone (18F-14).
The observed oxidation of the sulfide to the sulfoxide and
sulfone was expected and unavoidable.45 Fortunately, whereas
sulfones are difficult to reduce, sulfoxide compounds can be
reduced relatively easily because of the nucleophilic nature of
the sulfoxide oxygen, which can be covalently bound to
electrophilic species, producing an oxosulfonium species that
undergoes reduction by S-O bond scission.46 To obtain sulfide
23, it was necessary to reduce sulfoxide 25 under the conditions
consistent with work on the tracer level (i.e., normal atmosphere,
H2O). Diethyl chlorophosphite has been shown to reduce
sulfoxides in excellent yields at room temperature and to do so
4-(t-Butyl)phenyl methyl sulfone (16, Scheme 3) serves as
an effective pseudocarrier analog of sulfone 14 for the bicaluta-
mide synthesis by this convergent approach. Its reactivity for
anion generation and carbonyl addition is essentially the same
as that of the fluorophenyl sulfone 14, yet the bicalutamide
product analog that it produces (17) is considerably more

1030 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5
Scheme 1. Attempted Synthesis of Bicalutamide
Parent et al.
Scheme 2. Convergent Synthesis of Bicalutamide
Scheme 4. Synthesis of 4-Bromobicalutamide
level amounts of labeled sulfone (18F-14; Scheme 6), and trace
amounts of adventitious water readily quenched the low level
of the carbanion produced. Pseudocarrier 16 (Scheme 3) was
therefore added to raise the amount of total sulfone to a sufficient
level so that the required amount of n-BuLi could be added
accurately. In this case, the increased lipophilic nature of the
t-butyl group on the final product resulting from reaction with
the pseudocarrier (namely, compound 17) retarded its elution
from the reverse-phase HPLC column, compared to that of the
labeled product (18F-1). Thus, although the chemical reactivity
of the t-butyl carrier (16) is similar to that of the labeled
fluorophenyl intermediate (18F-14), the product it produces (17)
can readily be separated from the final product (18F-1) and
therefore does not increase the mass amount in the final product,
as is needed to maintain high effective specific activity
(Scheme 6).
Scheme 3. Pseudocarrier Synthesis and Reaction to Form the
Bicalutamide Analog
The synthesis of [18F]bicalutamide (18F-1, Scheme 6) was
accomplished by the reaction of the ammonium salt precursor
13 with [18F]fluoride ion in the form of tetrabutylammonium
[18F]fluoride ([18F]TBAF). The ammonium precursor 13 was
treated with [18F]TBAF and subjected to microwave irradiation
to produce [18F]fluorophenyl sulfone (18F-14). Water was added
to the solution, and the resulting mixture was purified by solid-
phase extraction on reverse-phase silica gel followed by HPLC
to give a radiochemical chemical yield of 61 ( 12% (n ) 3,
decay corrected), and the radiochemical purity (determined by
HPLC with UV and radiometric detection, respectively) was
>95%.
in the presence of water.47 Thus, when the crude mixture of
sulfoxide 25 and sulfone 19 was treated with diethyl chloro-
phosphite, it gave the desired sulfide (23) in 34% yield from
the tin precursor 24. The overall yield of 4-bromo-thiobicaluta-
mide was low, 1.3%, but this is still acceptable for the
preparation of experimental radiopharmaceuticals.
Radiochemistry. Radiochemical Synthesis of [18F]Bicaluta-
mide (18F-1). The synthesis of [18F]bicalutamide (18F-1) was
attempted with and without a pseudocarrier, as already noted.
To produce receptor-targeted imaging agents that are medically
useful, very high specific activity is required. Thus, initially a
no-carrier-added synthesis of bicalutamide was attempted. This
was unsuccessful, however, because it was not possible to titrate
precisely the amount of base needed to deprotonate the tracer-
The t-butylphenyl pseudocarrier 16 was added to the dry vial
containing purified fluorophenyl sulfone (18F-14), and the
mixture was dissolved in dry THF, cooled to -78 °C, and placed

Non-Steroidal Androgens for Prostate Cancer Imaging
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5 1031
Scheme 5. Synthesis of 4-Bromo-thiobicalutamide
Scheme 6. Radiosynthesis of 18F-Bicalutamide
free from other co-eluting material. This resulted in a product
with an effective specific activity that was too low for it to be
evaluated in vivo. Because of the difficulties in the synthesis
and purification of product (18F-1), work on this target molecule
was discontinued, and we focused on the preparation of the
higher affinity 76Br analogs (76Br-19).
Radiochemical Synthesis of 4-[76Br]Bromobicalutamide
(76Br-19). 4-[76Br]Bromobicalutamide (76Br-19) was synthesized
by bromination of the tin precursor 20 with bromine-76,
according to the sequence shown in Scheme 4. Tributyltin 20
was added to the reaction vial containing dry [76Br]bromide ion
along with a 1.6% HOOAc/HOAc solution, and the mixture
was stirred at room temperature for 20 min to give the final
product, 4-[76Br]bromobicalutamide (76Br-19). The overall ra-
diochemical chemical yield was 29 ( 6% (n ) 3, decay
corrected), the radiochemical purity (determined by HPLC with
UV and radiometric detection, respectively) was >95%, and
the effective specific activity (determined by analytical HPLC)
was approximately 282 Ci/mmol (10.4 GBq/µmol). This radio-
labeled compound was used in subsequent tissue distribution
and metabolic stability studies (below).
Radiochemical Synthesis of 4-[76Br]Bromo-thiobicaluta-
mide (76Br-23). 4-[76Br]Bromo-thiobicalutamide was synthe-
sized according to the following procedure (cf. Scheme 5): Tin
precursor 24 was added to the reaction vial containing dry [76-
Br]bromide ion along with a 1.6% HOOAc/HOAc solution, and
this mixture was stirred at room temperature for 15 min. At
this point, H2O was added, and the crude sulfoxide intermediate
(76Br-25) and sulfone (76Br-19) were isolated by solid-phase
extraction on C-18 silica gel. Sulfoxide (76Br-25) together with
the corresponding sulfone (76Br-19) were eluted from the C-18
column, and this mixture was then reduced by treatment with
diethyl chlorophosphite (20 µL, 139 µmol) and purified using
reverse-phase HPLC.
under Ar. The resulting solution was treated with n-BuLi until
a pale-yellow color appeared, indicating formation of the methyl
sulfone anion. The vial was stirred for 10 min at -78 °C. At
this time, keto amide 6 was added, and the mixture was allowed
to warm to room temperature and was stirred for an additional
15 min. The reaction was quenched with saturated ammonium
chloride, and the extracted product was purified by reverse-
phase HPLC to afford 18F-bicalutamide (18F-1). The overall
radiochemical chemical yield was 21% decay corrected, and
the radiochemical purity (determined by HPLC with UV and
radiometric detection, respectively) was >95%. The effective
specific activity (determined by analytical HPLC), however, was
surprisingly low, only ca. 13 Ci/mmol (480 MBq/µmol).
Unfortunately, although the t-butyl analog produced from the
pseudocarrier (17) could be separated effectively, we were
unable to isolate the 18F-bicalutamide product (18F-1) sufficiently
The overall radiochemical chemical yield of 4-[76Br]Bromo-
thiobicalutamide (76Br-23) was 4% (decay corrected), and the
radiochemical purity (determined by HPLC with UV and

1032 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5
Parent et al.
Table 1. Binding Affinities of Bicalutamide and Bromine-Based
Table 2. 4-[76Br]Bromobicalutamide Tissue Distribution in Adult Rats
Analogs
% injected dose/ga
tissue
1 h
1 h blockb
18 h
18 h blockb
blood
liver
kidney
0.56 ( 0.046 0.62 ( 0.011 0.34 ( 0.010
0.29 ( 0.021
0.36 ( 0.060
0.26 ( 0.037
0.11 ( 0.023
2.1 ( 0.31
2.5 ( 0.18
0.56 ( 0.069
1.0 ( 0.055
1.0 ( 0.076 0.36 ( 0.034
muscle 0.34 ( 0.020 0.38 ( 0.024 0.15 ( 0.022
bone
prostate
0.28 ( 0.015 0.31 ( 0.012 0.13 ( 0.0092 0.12 ( 0.0018
1.0 ( 0.20 0.68 ( 0.13 0.27 ( 0.049 0.22 ( 0.027
a Groups of five animals per data point. b Non-castrated, testis-intact
animals.
Relative Binding Affinity (RBA) values in which the standard
AR ligand 27 has an RBA value of 100.3,48
(R)-Bicalutamide (R)-1 binds selectively to the AR,49 and in
our hands this compound had an affinity of around 1.3 µM, a
value lower than that reported by others.49 Because the affinities
that we measure for DHT and R1881 (27) with our binding
assay are in accordance with the affinities of these compounds
reported by others,50-53 the origin of the lower affinity we
measure for bicalutamide is unclear. Nevertheless, in our
modifications of bicalutamide we found that bromine substitu-
tion (19) for fluorine (1) did cause a large increase (12-fold) in
the AR affinity so that bromobicalutamide bound with a Kd of
110 nM. The reason for this increased affinity is not known,
but it might be due to the lower electronegativity and greater
polarizability of bromine versus that of fluorine. Because
bromobicalutamide (19) was the compound that could be
radiolabeled most easily and in highest effective activity and
was also the compound having nearly the highest AR binding
affinity of the ones investigated in this study, it was the
compound selected for further biodistribution and metabolic
stability studies.
We also reduced the sulfone linkage to the sulfide on 23 and
26, but we saw no change in binding affinities for the reduced
compounds even though there is reported to be a 10-fold
increase in binding affinity when the sulfone in bicalutamide is
reduced to the sulfide.23 We synthesized the nitro arene 26 to
see whether there was a change in affinity between the cyano-
and nitro-substituted A rings, as reported in some systems, but
no change in affinity was noted.54
Biodistribution of 4-[76Br]Bromobicalutamide (76Br-19).
Purified 4-[76Br]bromobicalutamide (76Br-19), the compound
selected for further study, was reconstituted in 10% ethanol-
saline and injected into mature, male Sprague-Dawley rats that
had been castrated to suppress endogenous androgen biosyn-
thesis. Doses of 76Br-19 employed were 4 or 7 µCi/animal, and
animals were sacrificed at 1 and 18 h postinjection, respectively.
To ascertain whether tissue accumulation of activity was
mediated by a high-affinity, limited-capacity uptake system, one
set of animals was left with testes intact. In these animals, high
levels of circulating testosterone occupy the AR nearly fully.55
The results of this experiment are shown in Table 2.
a Relative binding affinity (RBA) where R1881 (27) is 100%. The Kd
value of R1881 (27) is 0.6 nM.62 b Competitive radiometric binding assays
were done with the purified ligand binding domain of rat AR (Panvera/
Invitrogen), using [3H]R1881 (3H-27) as a tracer, as previously described.63
radiometric detection, respectively) was >95%. The specific
activity, however, was not calculated as a result of low levels
of activity and mass contamination. Because of difficulties
encountered in the synthesis and purification of the sulfide (76-
Br-23) and the lack of increased AR binding affinity for this
compound compared to that of the sulfone analog 19 (below),
further efforts to produce this target molecule were stopped,
and it was not brought forward for animal studies in vivo.
The uptake of 4-[76Br]bromobicalutamide (76Br-19) by the
prostate appears to be AR mediated. Tissue samples at the 1 h
point show prostate/muscle and prostate/blood ratios of 2.9 and
1.8, respectively. At the 1 h time point, the control study (testes
intact), in which AR is saturated by endogenous testosterone
in the noncastrated animals, shows a significant drop in prostate/
blood and prostate/muscle ratios, with the ratios declining to
1.8 and 1.1, respectively. It is important to note that other organs
with high levels of activity in the castrated rats (liver, kidney)
did not experience a similar drop in bromine-76 incorporation
as did the prostate in the testes-intact rats. In fact, their levels
increased, whereas the level of prostate incorporation decreased.
Biological Studies. Androgen Receptor Ligand Binding
Assays. The androgen receptor binding affinities of the bromo
and fluoro analogs of bicalutamide are shown in Table 1,
together with those of related compounds for comparison. These
binding affinities were determined by a competitive radiometric
binding assay using purified AR with the high-affinity steroidal
AR ligand [3H]R1881 (3H-27, Table 1) used as tracer and
unlabeled R1881 (27) as a standard. Affinities are expressed as

Non-Steroidal Androgens for Prostate Cancer Imaging
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5 1033
Table 3. 4-[76Br]Bromobicalutamide Tissue Distribution in CWR22
Tumor-Bearing Mice
and injected onto an analytical reverse-phase HPLC for analysis
of the reaction products. No significant decomposition of the
product or nucleophilic displacement of the fluorine or bromine
by glutathione was evident, indicating that these compounds
are stable under physiological conditions.
% injected dose/ga
tissue
30 min
90 min
90 min blockb
blood
liver
kidney
muscle
prostate
tumor
2.7 ( 0.47
15 ( 1.5
7.2 ( 1.1
2.5 ( 0.54
2.2 ( 0.57
2.5 ( 0.53
3.5 ( 0.47
18 ( 1.5
7.8 ( 1.8
2.9 ( 0.35
2.8 ( 0.90
3.8 ( 0.77
3.0 ( 0.44
14 ( 0.72
7.6 ( 1.3
2.8 ( 0.28
3.4 ( 1.1
4.5 ( 0.56
To investigate the in vivo stability of 4-[76Br]bromobicaluta-
mide (76Br-19), blood samples were taken from each time group
of the rats used in the biodistribution study, blocked and
unblocked (below), and the amount of intact 76Br-19 was
followed using radiometric normal-phase thin-layer chroma-
tography. Blood analysis showed that at 1 h only circa 20% of
the activity was due to intact 76Br-19 in both sets of animals.
The remaining activity was immobile on normal-phase TLC and
presumed to be inorganic bromine ion released by metabolism.
a Groups of five animals per data point. b AR-mediated uptake blocked
by addition of excess 17R-methyltestosterone.
Analysis of the tissue uptake data using a Student t test indicates
a >95% confidence that the androgen-depleted prostate has a
higher level of incorporation than in the testes-intact rats. In
addition, there is >99% confidence that the prostate incorporates
more activity than the nontarget tissues of muscle and blood.
At the extended time point of 18 h, there are greatly
diminished levels of bromine-76 incorporation in the prostate.
In addition, prostate activity levels are nearly the same as in
the nontarget tissues, and the testes-intact animals do not show
any significant reduction in prostate activity. This indicates that
whereas 4-[76Br]bromobicalutamide (76Br-19) is taken up by the
AR into the prostate at early times, 4-[76Br]bromobicalutamide
has a significantly reduced affinity for the AR when compared
to that of FDHT (0.53 vs 43%, respectively), a difference that
could account for the lower incorporation and poorer retention
of 76Br-19 into the rat prostate compared to that for FDHT.4
This compound is also metabolized rapidly in blood (below).
Thus, although 4-[76Br]bromobicalutamide has an AR affinity
higher than that of the parent compound bicalutamide, it is still
likely too low to be of clinical importance.
An additional study was undertaken to determine whether
4-[76Br]bromobicalutamide (76Br-19) would be taken up into
an experimental prostate tumor model. Purified 76Br-19 was
reconstituted in 10% ethanol-saline and injected (iv, tail vein)
into mature male mice having a previously implanted tumor
prostate (CWR22) in the flank. These animals had also been
injected subcutaneously with DES to suppress endogenous
androgen biosynthesis.56 CWR22 is an androgen-dependent
human prostate cancer cell line that has a high level of AR
expression;57 however, in 24 h castrated mice CWR22 cells
experience a much more significant drop of AR levels than does
the prostate.58
Doses of 76Br-19 employed were 6 µCi/animal, and animals
were sacrificed at 30 and 90 min postinjection. To ascertain
whether tissue accumulation of activity was mediated by a high-
affinity, limited-capacity uptake system, one set of animals was
co-injected with the radiotracer together with a blocking dose
of 17R-methyl testosterone. The results of these experiments
are shown in Table 3.
In these tumor-bearing nice, there was little incorporation of
4-[76Br]bromobicalutamide in the prostate tumors or in the target
tissues compared to the nontarget tissues. Additionally, there
was little difference between the androgen-blocked and the DES-
treated mice.
Stability and Metabolism of Bicalutamide, 4-Bromobi-
calutamide, 4-[76Br]Bromobicalutamide, and 4-Bromo-thio-
bicalutamide. Following the procedure by Grillo et al.,59 we
incubated bicalutamide, 4-bromobicalutamide, and 4-bromo-
thiobicalutamide in a potassium phosphate buffer treated with
glutathione to simulate nucleophilic conditions in vivo. Each
compound was separately incubated with glutathione and stirred
at 37 °C for 24 h. Aliquots at various time points were taken
At 18 h, all of the bromine-76 activity in both sets of animals
76
was found to be immobile, which indicated that no intact
-
Br-19 remained in the blood by this time. No studies were
undertaken to examine the activity present in the prostate.
In the tumor-bearing mice, a tumor was taken from each time
group, and the resulting activity was analyzed as previously
described for rat blood samples. At each time point, there was
no evidence of intact 4-[76Br]bromobicalutamide 76Br-19 in the
prostate tumors; consistent with the biodistribution study.
Discussion
To develop nonsteroidal antiandrogens as PET imaging for
androgen-independent prostate cancer, we prepared bicalutamide
(1) and two analogs, bromobicalutamide (19) and bromo-
thiobicalutamide (23), along with their respective analogs labeled
with the positron-emitting radionuclides fluorine-18 (bicaluta-
mide itself) or bromine-76 (the two analogs). We measured the
androgen receptor (AR) binding affinity of these and related
compounds, and we selected one compound, 4-bromobicaluta-
mide, for further biological study to assess its potential as an
in vivo imaging agent for AR-positive prostate tumors. 4-Bro-
mobicalutamide (19) was one of the highest-affinity compounds,
and of the three, it was the only one that we could prepare in
radiolabeled form at high-effective specific activity. We then
studied the metabolic stability of 4-[76Br]bromobicalutamide (76-
Br-19) and its tissue distribution in surgically and chemically
castrated rats and mice.
We were able to prepare bicalutamide labeled with fluorine-
18 by performing an efficient nucleophilic aromatic substitution
on the trimethylammonium salt of the phenyl methyl sulfone
system followed by the addition of the lithium arylsulfonylm-
ethylide to a pyruvanilide. At the radiotracer level, we were
only able to get the second step to work when we added a
pseudocarrier sulfone, 4-(t-butyl)-phenyl methyl sulfone. Al-
though [18F]bicalutamide, obtained in reasonable yield by this
approach, could be separated by HPLC from the more lipophilic
product derived from the pseudocarrier sulfone, we were
discouraged from working further with this material because
the radiolabeled material was still sufficiently contaminated by
other coeluting and receptor-binding byproducts..
Radiobromination of tributyltin precurors with [76Br]hypo-
bromite readily gave the two bromobicalutamide analogs. In
this manner, 4-[76Br]bromobicalutamide (76Br-19) could be
obtained in good radiochemical yield (24-29% decay corrected
at 65 min) and at high effective specific activity (282 Ci/mmol).
By contrast, 4-[76Br]bromo-thiobicalutamide (76Br-23), whose
production required an additional reduction step, was obtained
only in low effective specific activity, insufficient for further
studies.
AR binding affinity measurements on these and related
compounds showed that 4-bromobicalutamide (19) has a

1034 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5
Parent et al.
was achieved by either UV light (254 nm) or after phosphomolybdic
acid indicator spray. Flash chromatography was performed accord-
ing to a literature method61 with Woelm silica gel (0.040-0.063
mm) packing. In most cases, product isolation consisted of removing
the solvent from the reaction mixture, extracting with an organic
solvent, washing with water and brine, drying with anhydrous
sodium sulfate, and filtering. The use of such a workup will be
indicated by the phrase “product isolation” (which is followed, in
parentheses, by the extracting solvent). Purification in most cases
was achieved by flash chromatography and is signified by the term
“flash chromatography” (which is followed, in parentheses, by the
elution solvent used). Melting points were determined on a Thomas
Hoover melting point apparatus and are uncorrected.
For radiosynthetic purification, a semipreparative reverse-phase
HPLC column (Alltech Alltima C18 column, 10 × 250 mm2) was
used. The mobile phase was either THF-water or acetonitrile-
water. Analytical purity was determined using a reverse-phase
HPLC (Phenomenex Luna C18 column, 4.6 × 150 mm2). The
eluant was monitored with a variable-wavelength detector set at
254 nm and a flow-through sodium iodide scintillation detector,
where appropriate. Radioactivity was determined with a dose
calibrator. Radiochemical yields are decay corrected to the begin-
ning of synthesis time (BOS).
significantly higher affinity for the AR than does the initial lead
compound, bicalutamide. Although thio-bicalutamide is reported
to bind to AR better than bicalutamide does, we did not find
this to be the case with the compounds we prepared in the
4-bromo series, namely, 4-bromo-thiobicalutamide (23) versus
4-bromobicalutamide (19).23
In biodistribution studies, 4-[76Br]bromobicalutamide (76Br-
19) is the first nonsteroidal AR antagonist to demonstrate AR-
mediated uptake into the prostate tissue. Target tissue-selective
uptake in rats is limited, however, and further studies in AR-
positive prostate tumor-bearing mice did not indicate selective
uptake into the tumor or target tissues. The specific activity of
our preparation of 4-[76Br]bromobicalutamide (76Br-19) was 282
Ci/mmol. Whereas this is reasonably high, we wanted to be
sure that the limited uptake of this compound into prostate tissue
is not due to saturation of the target tissue AR. At our specific
activity, the injected dose of 4 µCi per animal used in the
castrated rat model corresponds to a mass amount of 14 pmol.
On the basis of uptake studies we have previously done with
various radiolabeled androgens in the prostate of adult male
rats,55 we find a maximum of 0.7% ID/g uptake in prostate
tissue. In the case of 4-[76Br]bromobicalutamide (76Br-19), this
would correspond to a maximum exposure of the prostate to
0.10 pmol/g tissue. In earlier studies, we showed that the prostate
of surgically castrated adult male rats contains 5.4 pmol/g of
AR, all of which are unoccupied.55 Therefore, the administered
dose of 4 µCi of 4-[76Br]bromobicalutamide (76Br-19), which
gives a prostate exposure of only 0.10 pmol/g, would be
sufficient to reach less than a 2% saturation of the AR content
of the prostate. Thus, the limited uptake we see for 4-[76Br]-
bromobicalutamide (76Br-19) in the prostate is not due to the
saturation of target tissue AR, but is more likely due to the
relatively low affinity of this ligand for the receptor. Low affinity
is also the most likely explanation for the lack of AR-mediated
target tissue and tumor uptake found in the biodistribution
studies done in the CWR22 tumor-bearing mice, although the
rapid metabolism of [76Br]bromobicalutamide (76Br-19), noted
in rat blood, could also limit the extent of target-tissue uptake.
Whereas our studies demonstrate that nonsteroidal androgen
receptor ligands can be labeled with positron-emitting radio-
nuclides at high specific activity and that one of these, [76Br]-
bromobicalutamide (76Br-19), shows AR-mediated uptake in
castrated rats, in the principal androgen target tissue, the prostate,
this uptake is limited, and this compound is rapidly metabolized.
Clearly, the behavior of this radiopharmaceutical is not adequate
for imaging of the prostate or prostate tumors in a clinical
setting. Thus, there is still a need for the development of more
effective nonsteroidal androgens for PET imaging of AR in
prostate tumors; future studies should focus on increasing the
AR binding affinity of these ligands and should seek to
understand and possibly moderate the rate of metabolism of
these compounds.
1H and 13C NMR spectra were recorded on a U500 or U400
Varian FT-NMR spectrometer. Chemical shifts (δ) are reported in
ppm downfield by reference to proton resonances resulting from
incomplete deuteration of the NMR solvent. Higher-resolution EI
mass spectra were obtained on a Finnigan MAT 731 spectrometer.
Higher-resolution ESI and FAB mass spectra were obtained on a
Micromass Q-Tof Ultima and a Micromass 70-SE-4F, respectively.
Combustion analyses were obtained with a CE440 by Exeter
Analytical, Inc. and were within 0.4% of calculated values.
Androgen receptor binding affinity (RBA) assays were performed
according to literature methods.62,63 AR preparation used in these
experiments was purified from the rat AR ligand binding domain
(Panvera/Invitrogen, Madison, WI).
Radiosynthetic isolation and purification of fluorine-18 was
obtained from proton bombardment of oxygen-18 enriched water,
by an 18O(p, n)18F reaction. Activity in the irradiated water was
converted to [18F]TBAF by the addition of tetrabutylammonium
hydroxide, followed by careful evaporation of water and azeotropic
drying with acetonitrile, as previously described.64
Radiosynthetic isolation and purification of bromine-76 was
performed according to the following procedure:65 76Br- was
obtained from a 76Se(p, n)76Br reaction on an isotopically enriched
Cu76Se-coated tungsten incline target. The target was bombarded
with a 20 µA-15 MeV proton beam on a Cyclotron Corporation
CS15 for 2 h. The activity was dry distilled from the target under
argon gas flow in a quartz tube in a 1065 °C oven. The [76Br]-
bromide ion and a small amount of target material were deposited
outside of the oven in the quartz tube, and the [76Br]bromide ion
was washed from the quartz tube using 0.6 N NH4OH, which was
evaporated under a stream of nitrogen with gentle heating. The
bromine-76-containing NH4OH solution was passed over a C-18
separatory column that had been previously treated with H2O (3
mL). After the NH4OH was pushed through the column, it was
followed with EtOH (300 µL). The resulting solution was placed
in a glass reaction vial, and the solvent was removed using heat
(90 °C) and a stream of N2.
Experimental Section
N-(4-Cyano-3-trifluoromethyl-phenyl)-2-oxo-propionamide (6).
Pyruvic acid (2.683 g, 27.38 mmol) was placed in an oven-dried
round-bottomed flask (250 mL), fitted with a magnetic stirring bar,
and was dissolved in dry CH2Cl2 (200 mL). The flask was capped
with a rubber septum. R,R-Dichloro-methyl methyl ether (4.9 mL,
55 mmol) was added dropwise by syringe, and the resulting solution
was fitted with a water condenser and refluxed for 1 h. The solution
was then removed from heat, and the volatile solvents were removed
under reduced pressure. The resulting acid chloride was redissolved
in dry CH2Cl2 (100 mL), and 4-amino-2-trifluoromethylbenzonitrile
(1.273 g, 6.84 mmol) was added. The resulting mixture was capped
with a rubber septum, and the mixture was cooled to 0 °C. Pyridine
General Methods. All reagents and solvents were obtained from
Aldrich (Milwaukee, WI), except for racemic and enantiomerically
pure bicalutamide (1) and hydroxyflutamide, which were purchased
from Toronto Research Chemicals Inc. (North York, ON, Canada)
and tested without further purification. Tetrahydrofuran, methylene
chloride, toluene, and diethyl ether were dried by a solvent delivery
system (neutral alumina column) designed by J.C. Meyer (Irvine,
CA).60 All reactions were performed under a dry (Drierite) nitrogen
atmosphere unless otherwise stated. Reaction progress was moni-
tored using analytical thin-layer chromatography (TLC) on 0.25
mm Merck F-254 silica gel glass plates. Visualization of the TLC

Non-Steroidal Androgens for Prostate Cancer Imaging
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5 1035
(2.2 mL, 27 mmol) was added by syringe, and the mixture was
slowly warmed to room temperature and stirred for 14 h. Product
isolation (CH2Cl2, water, Na2SO4) followed by flash chromatog-
raphy (40% EtOAc/60% hexanes) furnished the product (477 mg,
1.86 mmol) in 27% yield as a white solid with mp ) 148-149 °C
(lit. mp ) 147-148 °C).21 Rf ) 0.53 in 40% EtOAc/hex. 1H NMR
(500 MHz, CDCl3) δ: 9.12 (s, 1H), 8.14 (d, J ) 2.14 Hz, 1H),
8.00 (dd, J ) 2.14, 8.47 Hz, 1H), 7.84 (d, J ) 8.47 Hz, 1H), 2.58
(s, 3H). 13C NMR (125 MHz, CDCl3) δ: 195.92, 157.86, 140.40,
out from the mother liquor as a white solid (654 mg, 0.990 mmol)
in 66% yield. No further purification was necessary. mp ) 188-
1
191 °C. H NMR (500 MHz, CD3CN) δ: 9.32 (s, 1H), 8.11 (d, J
) 9.22 Hz, 1H), 8.07 (dd, J ) 2.14, 8.58 Hz, 1H), 8.06 (AA’XX’,
J ) 9.43 Hz, 2H), 7.89 (AA’XX’, J ) 8.58 Hz, 2H), 4.22 (d, J )
14.90 Hz, 1H), 4.17 (d, J ) 14.90 Hz, 1H), 3.59 (s, 9H), 2.06 (s,
3H), 1.82 (s, 3H). 13C NMR (125 MHz, CD3CN) δ: 170.96, 170.79,
151.57, 143.26, 143.03, 137.06, 133.46 (q,3JCF ) 32.22 Hz), 131.31,
124.11, 123.47 (q,2JCF ) 273.42 Hz), 122.92, 119.11 (q,4JCF ) 4.60
Hz), 118.38, 116.62, 104.77 (q,4JCF ) 1.84 Hz), 80.17, 58.42, 77.95,
55.24, 23.98, 21.98. HRMS (ESI, Q-TOF) calcd, 512.1449; found,
512.1449.
136.03, 134.24 (q,3JCF ) 32.22 Hz), 122.09, 121.93 (q,2JCF
274.34 Hz), 117.50 (q,4JCF ) 4.60 Hz), 115.22, 105.57, (q,4JCF
)
)
1.84 Hz), 23.83; HRMS (EI+) m/z: calcd, 256.0460; found,
256.0460.
(4-Methanesulfonyl-phenyl)-N,N-dimethyl-amine (12). 4-Me-
thylsulfonylaniline hydrochloride (1.050 g, 5.183 mmol) was added
to a flame-dried round-bottomed flask (250 mL) and was dissolved
in dry THF (150 mL). NaH (1.45 g of a 60% dispersion, 20.7 mmol)
was added in portions to the solution. The resulting mixture was
capped with a rubber septum, and HMPA (1.8 mL, 10.37 mmol)
and CH3I (3.2 mL, 52 mmol) were added slowly by syringe at room
temperature and allowed to stir for 18 h. The reaction was quenched
with saturated ammonium chloride (100 mL) and diluted with H2O
(100 mL). Product isolation (CH2Cl2, water, Na2SO4) followed by
flash chromatography (15% EtOAc/85% CH2Cl2) yielded a pure
product (906 mg, 4.55 mmol) as a white powder in 89% yield with
mp ) 163-166 °C (lit. mp ) 166-167 °C).25 Rf ) 0.50 in 80%
EtOAc/hexanes. 1H NMR (500 MHz, CDCl3) δ: 7.73 (AA’XX’, J
) 9.11 Hz, 2H), 6.69 (AA’XX’, J ) 9.11 Hz, 2H), 3.06 (s, 6H),
3.00 (s, 3H). 13C NMR (125 MHz, CDCl3) δ: 153.36, 129.04,
125.85, 110.95, 45.07, 40.07. HRMS (EI+) calcd, 199.0667; found,
199.0673.
(4-Methanesulfonyl-phenyl)-N,N,N-trimethyl-ammonium Tri-
fluoromethanesulfonate (13). Methyl sulfone 12 (410 mg, 2.06
mmol) was placed in a flame-dried flask (100 mL), fitted with a
magnetic stirring bar, and was dissolved in dry CH2Cl2 (40 mL).
Methyl trifluoromethanesulfonate (2.3 mL, 21 mmol) was added,
and the solution was refluxed for 20 h. Product (233 mg, 0.641
mmol) was found to have precipitated from the mother liquor as a
white solid in a 31% yield, and no further purification was
necessary. mp ) 189-193 °C. 1H NMR (500 MHz, DMSO-d6) δ:
8.27 (AA’XX’, J ) 9.11 Hz, 2H), 8.18 (AA’XX’, J ) 9.11 Hz,
2H), 3.67 (s, 9H), 3.32 (s, 3H). 13C NMR (125 MHz, DMSO-d6)
δ: 150.73, 142.28, 128.98, 122.26, 200.7 (q,2JCF ) 322.22 Hz),
56.52, 43.11. HRMS (FAB) calcd, 214.0902; found, 214.0942.
4-Fluorophenyl Methyl Sulfone (14). The trimethylammonium
sulfone precursor 13 (120 mg, 0.331 mmol) was placed in a pear-
shaped flask (50 mL), fitted with a magnetic stirring vane, and was
dissolved in DMSO (15 mL). TBAF (1 M, 1.7 mL, 1.7 mmol) was
added to the solution, and the solution was heated to 90 °C and
stirred for 30 min. Product isolation (CH2Cl2, LiCl(sat), Na2SO4)
followed by flash chromatography (30% EtOAc/70% hexanes)
afforded a pure product (50 mg, 0.287 mmol) in 87% yield. Product
authenticity was verified through coanalysis of NMR with a
commercially available compound.
N-(4-Cyano-3-trifluoromethyl-phenyl)-3-(4-fluoro-benzene-
sulfonyl)-2-hydroxy-2-methyl-propionamide (1). 4-Fluorophenyl
methyl sulfone 4 (72 mg, 0.414 mmol) was added to a flame-dried
pear-shaped flask (50 mL), fitted with a magnetic stirring vane,
and was dissolved in dry THF (20 mL). The resulting solution was
cooled to -78 °C. n-BuLi (1.2 M, 690 µL, 0.828 mmol) was added
drop by drop, and the resulting solution was stirred for 20 min
while a bright-yellow color developed. Meanwhile, in a separate
flame-dried round-bottomed flask (50 mL), also fitted with a
magnetic stirring bar, N-(4-cyano-3-trifluoromethyl-phenyl)-2-oxo-
propionamide (53 mg, 0.207 mmol) was dissolved in dry THF (10
mL) and cooled to -78 °C. The two solutions were combined
through a cannulus, allowed to warm slowly to room temperature,
and stirred for 3 h. Product isolation (CH2Cl2, water, Na2SO4)
followed by flash chromatography (5% EtOAc/95% CH2Cl2) gave
a pure product (85 mg, 0.198 mmol) in 95% yield. Product
authenticity was verified through coanalysis of NMR and HPLC
with a commercially available compound.
N-(4-Cyano-3-trifluoromethyl-phenyl)-3-(4-N,N-dimethylamino-
benzenesulfonyl)-2-hydroxy-2-methyl-propionamide (7). N,N-
Dimethylaniline-4-methyl sulfone (408 mg, 2.05 mmol) was added
to a flame-dried pear-shaped flask (65 mL), fitted with a magnetic
Teflon stirring vane, and dissolved in dry THF (20 mL). The flask
was fitted with a rubber septum and cooled to -78 °C. n-Butyl
lithium (1.2 M, 1.7 mL, 2.04 mmol) was added dropwise to the
chilled solution, and the reaction was stirred for 30 min, at which
time a bright-yellow color developed. While the previous vial was
stirring, propionamide 6 (547 mg, 2.13 mmol) was added to a flame-
dried, round-bottomed flask (100 mL) fitted with a magnetic stirring
bar and was dissolved in dry THF (40 mL). The solution was cooled
to -78 °C, and the sulfone solution was cannulated into the
propionamide solution. The solution was allowed to warm slowly
to room temperature and was stirred for 2 h. Product isolation (CH2-
Cl2, water, Na2SO4) followed by flash chromatography (15%
EtOAc/85% CH2Cl2) afforded a pure product as a white solid (281
mg, 0.618 mmol) in 30% yield with mp ) 146-151 °C. Rf ) 0.16
in 15% EtOAc/85% CH2Cl2. 1H NMR (500 MHz, CDCl3) δ: 9.11
(s, 1H), 7.98 (d, J ) 2.14 Hz, 1H), 7.73 (d, J ) 8.47 Hz, 1H), 7.65
(dd, J ) 2.05, 8.58 Hz, 1H), 7.58 (AA’XX’, J ) 9.22 Hz, 2H),
6.47 (AA’XX’, J ) 9.22 Hz, 2H), 5.51 (s, 1H), 3.98 (d, J ) 14.58
Hz, 1H), 3.37 (d, J ) 14.58 Hz, 1H,), 2.93 (s, 6H), 1.53 (s, 3H).
13C NMR (125 MHz, CDCl3) δ: 171.82, 153.65, 141.41, 135.49,
133.85 (q,3JCF ) 32.22 Hz), 129.87, 125.68, 122.84 (q,2JCF
)
274.36 Hz), 121.70, 117.14 (q,4JCF ) 4.60 Hz), 115.41, 110.63,
104.44 (q,4JCF ) 1.84 Hz), 73.94, 61.15, 39.79, 28.05. HRMS (ESI,
Q-TOF) calcd, 456.1205; found, 456.1191. Anal. calcd for
(C19H18F3N3O4S1): C, H, N.
Acetic Acid. 1-(4-Cyano-3-trifluoromethyl-phenylcarbamoyl)-
2-(4-N,N-dimethylamino-benzenesulfonyl)-1-methyl-ethyl Ester
(8). Amine 7 (280 mg, 0.615 mmol) was added to a flame-dried
round-bottomed flask (250 mL), fitted with a stirring bar, and was
dissolved in dry THF (50 mL). Acetyl chloride (440 µL, 6.15
mmol), pyridine (430 µL, 6.15 mmol), and DMAP (75 mg, 0.62
mmol) were added to the solution at room temperature, and the
mixture was stirred for 3 h. At this time, the volatile solvents were
evaporated under reduced pressure, and the mixture was purified
with flash chromatography using 15% EtOAc/85% hexanes to
produce the purified product (161 mg, 0.324 mmol) as a white solid
in 53% yield with mp ) 121-123 °C. Rf ) 0.19 in 15 EtOAc/
1
hexanes. H NMR (500 MHz, CDCl3) δ: 8.73 (s, 1H), 8.03 (d, J
) 2.04 Hz, 1H), 7.85 (dd, J ) 1.93, 8.47 Hz, 1H), 7.73 (d, J )
8.47 Hz, 1H), 7.58 (AA’XX’, J ) 9.22 Hz, 2H), 6.53 (AA’XX’, J
) 9.11 Hz, 2H), 4.18 (d, J ) 14.36 Hz, 1H), 3.95 (d, J ) 14.36
Hz, 1H), 2.94 (s, 6H), 2.22 (s, 3H), 1.81 (s, 3H). 13C NMR (125
MHz, CDCl3) δ: 169.62, 169.13, 153.46, 141.48, 135.49, 133.59
(q,3JCF ) 33.14 Hz), 129.76, 123.87, 122.64, 122.11 (q,2JCF
)
274.34 Hz), 117.92 (q,4JCF ) 5.52 Hz), 115.51, 110.66, 104.39
(q,4JCF ) 1.84 Hz), 80.00, 58.11, 39.78, 24.25, 22.06. HRMS (ESI,
Q-TOF) calcd, 498.1311; found, 498.1293.
4-[2-Acetoxy-2-(4-cyano-3-trifluoromethyl-phenylcarbamoyl)-
propane-1-sulfonyl]-phenyl-N,N,N-trimethyl-ammonium Trif-
luoromethanesulfonate (9). Amine 8 (750 mg, 1.50 mmol) was
added to a flame-dried round-bottomed flask (100 ml), fitted with
a stirring bar, and was dissolved in dry CH2Cl2 (40 mL). Methyl
trifluoromethanesulfonate (1.8 mL, 15.90 mmol) was added, and
the resulting solution was refluxed for 20 h. Product crystallized

1036 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5
Parent et al.
4-t-Butylphenyl Methyl Sulfone (16). 4-t-Butylbenzene thiol
(3.0 mL, 17 mmol) was placed in a round-bottomed flask (50 mL)
fitted with a magnetic stirring bar. H2O (15 mL) and NaOH (680
mg, 17 mmol) were added to the thiol, and the mixture was stirred
vigorously. While the solution was stirring, iodomethane (1.1 mL,
17 mmol) was slowly added, and the resulting two-phase system
was stirred at room temperature for 2 h. Product isolation (CH2-
Cl2, brine, Na2SO4) gave the crude compound that taken to the next
step without further purification.
The crude t-butylphenyl methyl sulfide was placed in a round-
bottomed flask (50 mL), fitted with a magnetic stirring bar, and
was dissolved in dry CH2Cl2 (30 mL). mCPBA (9.388 g, 51 mmol)
was added, and the reaction was stirred overnight at room
temperature. The volatile organics were removed under reduced
pressure, and the crude product was purified with flash chroma-
tography using 25% EtOAc/75% hexanes to afford a pure product
(3.058 g, 13.072 mmol) as a white crystal in 75% yield with mp )
94-96 °C (lit. mp ) 90-94 °C).36 Rf ) 0.23 in 25% EtOAc/
hexanes. 1H NMR (400 MHz, CDCl3) δ: 7.38 (AA’XX’, J ) 8.67
Hz, 2H), 7.28 (AA’XX’, J ) 8.67 Hz, 2H), 2.52 (s, 3H), 1.37 (s,
9H). 13C NMR (125 MHz, CDCl3) δ: 148.14, 134.77, 126.69,
125.77, 34.27, 31.23, 16.12. HRMS (EI+) calcd, 212.0871; found,
212.0874.
9.89 (s, 1H), 8.39 (d, J ) 1.93 Hz, 1H), 8.19 (dd, J ) 2.04, 8.58
Hz, 1H), 8.01 (d, J ) 8.58 Hz, 1H), 7.84 (AA’XX’, J ) 8.47 Hz,
2H), 7.70 (AA’XX’, J ) 8.47 Hz, 2H), 5.55 (s, 1H), 4.09 (d, J )
14.90 Hz, 1H), 3.69 (d, J ) 14.90 Hz, 1H), 1.54 (s, 3H). 13C NMR
(125 MHz, acetone-d6) δ: 173.74, 143.69, 140.99, 133.37 (q,3JCF
) 32.22 Hz), 132.90, 131.24, 136.86, 128.94, 123.55 (q,2JCF
)
273.42 Hz), 123.46, 118.27 (q,4JCF ) 4.60 Hz), 116.31, 104.24
(q,4JCF ) 1.84 Hz), 74.45, 63.93, 27.92. HRMS (ESI, Q-TOF) calcd,
490.9888; found, 490.9893. Anal. calcd (C17H12Br1F3N2O4S1):
C, H, N.
N-(4-Cyano-3-trifluoromethyl-phenyl)-2-hydroxy-2-methyl-
3-(4-tributylstannanyl-benzenesulfonyl)-propionamide (20). 4-Bro-
mobicalutamide (1.232 g, 2.60 mmol) was placed in a flame-dried
round-bottomed flask I250 mL), fitted with a magnetic stirring bar,
and was dissolved in dry toluene (100 mL). Triethylamine (1.9 mL,
26.0 mmol), bis(tributyltin) (6.6 mL, 13.0 mmol), and tetrakis-
(triphenylphosphine)palladium(0) (10 mg) were then added, and
the mixture was refluxed for 24 h. The volatile solvents were
removed under reduced pressure, and the crude mixture was purified
with flash chromatograpy using 50% EtOAc/50% hexanes to afford
a pure product (512 mg, 0.729 mmol) as an off-white solid in 28%
yield with mp ) 86-88 °C. Rf ) 0.41 in 50% EtOAc/hexanes. 1H
NMR (500 MHz, CDCl3) δ: 9.29 (s, 1H), 8.05 (d, J ) 1.72 Hz,
1H), 7.91 (dd, J ) 2.04, 8.58 Hz, 1H), 7.79 (AA’XX’, J ) 8.25
Hz, 2H), 7.75 (d, J ) 8.58 Hz, 1H), 7.64 (AA’XX’, J ) 8.25 Hz,
2H), 5.16 (s, 1H), 3.96 (d, J ) 14.36 Hz, 1H), 3.53 (d, J ) 14.36
Hz, 1H), 1.62 (s, 3H), 1.51 (pent, J ) 8.15 Hz, 6H), 1.31 (sextet,
J ) 7.40 Hz, 6H), 1.08 (t, J ) 8.04 Hz, 6H), 0.88 (t, J ) 7.29 Hz,
9H). 13C NMR (125 MHz, CDCl3) δ: 172.07, 153.30, 141.57,
138.72, 137.43, 135.91, 134.02 (q,3JCF ) 33.14 Hz), 126.28, 122.19,
122.05 (q,2JCF ) 274.34 Hz), 117.65 (q,4JCF ) 4.60 Hz), 115.61,
104.79 (q,4JCF ) 1.84 Hz), 74.80, 61.91, 29.06, 27.70, 27.41, 13.76,
9.90. HRMS (ESI, Q-TOF) calcd, 703.1839; found, 703.1831.
3-(4-Bromo-benzenesulfonyl)-N-(4-cyano-3-trifluoromethyl-
phenyl)-2-hydroxy-2-methyl-propionamide (19) from N-(4-Cy-
ano-3-trifluoromethyl-phenyl)-2-hydroxy-2-methyl-3-(4-tribu-
tylstannanyl-benzenesulfonyl)-propionamide (20). NH4Br (6 mg,
61 µmol) was placed in a conical vial (5 mL), dissolved in a 10%
HOOAc/HOAc solution (500 µL), and stirred for 20 min. During
this time, the solution turned a pale-amber color. Propionamide (20)
(43 mg, 62 µmol) was then added, and the solution was stirred at
room temperature open to the atmosphere for 45 min. Product
isolation (CH2Cl2, bicarbonate, Na2SO4) followed by flash chro-
matography using 50% EtOAc/50% hexanes afforded a pure product
as a white solid (26 mg, 52 µmol) in 84% yield.
3-(4-tert-Butyl-benzenesulfonyl)-N-(4-cyano-3-trifluoromethyl-
phenyl)-2-hydroxy-2-methyl-propionamide (17). 4-t-Butylphenyl
methyl sulfone (172 mg, 0.811 mmol) was added to a flame-dried
pear-shaped flask (65 mL), fitted with a magnetic stirring vane,
and was dissolved in dry THF (15 mL). The flask was fitted with
a rubber septum and cooled to -78 °C. n-Butyl lithium (1.2 M,
0.90 mL) was added dropwise to the chilled solution, and the
reaction was stirred for 20 min, at which time a dark-yellow color
evolved. While the previous vial was stirring, propionamide 6 (138
mg, 0.541 mmol) was added to a flame-dried round-bottomed flask
(100 mL), fitted with a magnetic stirring bar, and was dissolved in
dry THF (20 mL). The solution was cooled to -78 °C, and the
sulfone solution was cannulated into the propionamide solution.
The solution was allowed to warm slowly to room temperature and
was stirred for 2 h. Product isolation (CH2Cl2, water, Na2SO4)
followed by flash chromatography (50% EtOAc/50% hexanes)
afforded a pure product as a white solid (71 mg, 0.152 mmol) in
28% yield with mp ) 89-92 °C. Rf ) 0.33 in 10% EtOAc/90%
CH2Cl2. 1H NMR (500 MHz, CDCl3) δ: 9.19 (s, 1H), 8.01 (d, J )
2.04 Hz, 1H), 7.82 (dd, J ) 2.14, 8.47 Hz, 1H), 7.78 (AA’XX’, J
) 8.79 Hz, 2H), 7.75 (d, J ) 8.58 Hz, 1H), 7.49 (AA’XX’, J )
8.90 Hz, 2H), 5.95 (s, 1H), 3.97 (d, J ) 14.47 Hz, 1H), 3.47
(d, J ) 14.47 Hz, 1H), 1.59 (s, 3H), 1.27 (s, 9H). 13C NMR (125
MHz, CDCl3) δ: 171.66, 158.85, 141.24, 135.84, 135.76, 134.13,
N-(4-Cyano-3-trifluoromethyl-phenyl)-2-methyl-2-oxirane-
propionamide (22). N-(4-Cyano-3-trifluoromethyl-phenyl)-2-meth-
yl-acrylamide (513 mg, 2.02 mmol) was dissolved in 96% formic
acid (15 mL). H2O2 (37%, 8 mL) was slowly added, and the
resulting solution was stirred at 40 °C for 2 h. Product isolation
(CH2Cl2, bicarbonate, Na2SO4) followed by flash chromatography
(100% CH2Cl2) produced a pure product (480 mg, 1.778 mmol) in
133.73 (q,3JCF ) 33.14 Hz), 127.73, 126.45, 122.03 (q,2JCF
)
273.34 Hz), 121.89, 117.31 (q,4JCF ) 4.60 Hz), 115.38, 104.76
(q,4JCF ) 1.84 Hz), 74.38, 73.42, 61.40, 35.27, 30.85, 27.74.
HRMS (EI+) calculated 468.1331 found 468.1323. Anal. calcd.
(C21H21F3N2O4S1): C, H, N.
88% yield as an off-white powder. (lit. mp ) 149-150 °C).44 1
H
3-(4-Bromo-benzenesulfonyl)-N-(4-cyano-3-trifluoromethyl-
phenyl)-2-hydroxy-2-methyl-propionamide (19). 4-Bromophenyl
methyl sulfone (1.488 mg, 6.33 mmol) was added to a flame-dried
pear-shaped flask (65 mL), fitted with a magnetic stirring vane,
and was dissolved in dry THF (30 mL). The flask was fitted with
a rubber septum and cooled to -78 °C. n-Butyl lithium (1.2 M,
5.3 mL) was added dropwise to the chilled solution, and the reaction
was stirred for 30 min, at which time a dark-yellow color developed.
While the previous vial was stirring, N-(4-cyano-3-trifluoromethyl-
phenyl)-2-oxo-propionamide (818 mg, 3.20 mmol) was added to a
flame-dried round-bottomed flask (100 mL), fitted with a magnetic
stirring bar, and was dissolved in dry THF (50 mL). The solution
was cooled to -78 °C, and the sulfone solution was cannulated
into the propionamide solution. The solution was allowed to warm
slowly to room temperature and was stirred for 2 h. Product isolation
(CH2Cl2, H2O, Na2SO4) followed by flash chromatography (50%
EtOAc/50% hexanes) afforded a pure product as a white solid
(1.232 g, 2.52 mmol) in 78% yield with mp ) 94-96 °C. Rf )
NMR (500 MHz, CDCl3) δ: 8.41 (s, 1H), 8.01 (d, J ) 1.93 Hz,
1H), 7.89 (dd, J ) 2.64, 8.58 Hz, 1H), 7.78 (d, J ) 8.68 Hz, 1H),
2.99 (s, 2H), 1.66 (s, 3H). 13C NMR (125 MHz, CDCl3) δ: 169.28,
141.19, 135.88, 133.78 (q,3JCF ) 33.14 Hz), 122.51 (q,2JCF
)
139.93 Hz), 117.24 (q,4JCF ) 4.60 Hz), 121.78, 115.40, 104.73
(q,4JCF ) 1.84 Hz), 56.65, 54.09, 16.61. HRMS (EI+) calcd,
290.0514; found, 290.0516.
3-(4-Bromo-phenylsulfanyl)-N-(4-cyano-3-trifluoromethyl-
phenyl)-2-hydroxy-2-methyl-propionamide (23). 4-Bromoben-
zenethiol (832 mg, 3.56 mmol) was added to a flame-dried round-
bottomed flask (100 mL), fitted with a magnetic stirring bar, and
was dissolved in dry THF (50 mL) and cooled to 0 °C. NaH (60%)
(142 mg, 3.56 mmol) was added, and the mixture was allowed to
stir for 5 min. While the above reaction was stirring, N-(4-cyano-
3-trifluoromethyl-phenyl)-2-methyl-2-oxirane-propionamide (480
mg, 1.78 mmol) was added to a flame-dried pear-shaped flask (50
mL) and was dissolved in dry THF (5 mL). The resulting solution
was added to the thiol. Product isolation (CH2Cl2, ammonium
1
0.24 in 50% EtOAc/hexane. H NMR (500 MHz, acetone-d6) δ:

Non-Steroidal Androgens for Prostate Cancer Imaging
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5 1037
sulfate, Na2SO4) followed by flash chromatography (40% EtOAc/
60% hexanes) yielded a pure product as an off-white solid (496
mg, 1.085 mmol) in 61% yield with mp ) 62-64 °C. Rf ) 0.27 in
removed using reduced pressure. The crude mixture was purified
with flash chromatography using 40% EtOAc/60% hexanes to yield
a pure product as an off-white solid (76 mg, 0.159 mmol) in 32%
yield with mp ) 54-56 °C. Rf ) 0.30 in 40% EtOAc/hexanes. 1H
NMR (500 MHz, CDCl3) δ: 9.03 (s, 1H), 7.94 (d, J ) 8.90 Hz,
1H), 7.91 (d, J ) 2.25 Hz, 1H), 7.80 (dd, J ) 2.36, 8.79 Hz, 1H),
7.26 (m, 4H), 3.78 (d, J ) 14.15 Hz, 1H), 3.55 (s, 1H), 3.12 (d, J
) 14.26 Hz, 1H), 1.55 (s, 3H). 13C NMR (125 MHz, CDCl3) δ:
173.18, 143.25, 141.41, 132.72, 132.69, 132.32, 127.20, 125.26
(q,3JCF ) 34.98 Hz), 122.08, 121.79, 120.77, 118.23 (q,4JCF ) 5.52
Hz), 75.43, 44.77, 26.38. HRMS (EI+) calcd, 477.9810; found,
477.9803. Anal. calcd (C16H12Br1F3N2O4S1): C, H, N.
1
40% EtOAc/60% hexanes. H NMR (500 MHz, CDCl3) δ: 9.08
(s, 1H), 7.95 (d, J ) 1.61 Hz, 1H), 7.76 (dd, J ) 2.04, 8.58 Hz,
1H), 7.73 (d, J ) 8.58 Hz, 1H), 7.24 (m, 4H), 3.78 (s, 1H), 3.72
(d, J ) 14.15 Hz, 1H), 3.12 (d, J ) 14.04 Hz, 1H), 1.55 (s, 3H).
13C NMR (125 MHz, CDCl3) δ: 173.39, 141.49, 135.85, 133.90
(q,3JCF ) 33.14 Hz), 133.18, 132.42, 132.14, 122.00 (q,2JCF
)
274.34), 121.88, 121.42, 117.28 (q,4JCF ) 4.60 Hz), 115.75, 104.26
(q,4JCF ) 2.76 Hz), 75.52, 44.71, 26.23. HRMS (EI+) calcd,
457.9915; found, 457.9906. Anal. calcd (C17H12Br1F3N2O2S1):
C, H, N.
N-(4-Cyano-3-trifluoromethyl-phenyl)-3-(4-[18F]fluoro-benze-
nesulfonyl)-2-hydroxy-2-methyl-propionamide (18F-1). Resin-
treated target [18O]H2O was subjected to proton bombardment, and
an aliquot containing 42.2 mCi (1.56 GBq) of [18F]fluoride was
transferred to a Vacutainer that had previously been treated with
tetrabutylammonium hydroxide (2 µL). The [18O]H2O was removed
by azeotropic distillation with acetonitrile (3 × 0.75 mL), N2, and
heat.66 Ammonium precursor 13 (1.1 mg, 3.0 µmol) was added to
the vessel and dissolved in DMSO (400 µL). The resulting mixture
was heated by microwave irradiation (3 × 20 s). The crude mixture
was passed over a silica pipet column (50 mg) with CH3CN (3
mL), and the volatile organics were then removed using reduced
pressure. The vial containing a crude mixture of [18F]fluorophenyl
methyl sulfone was dissolved in CH3CN (500 mL) and injected
through a Teflon filter onto a reverse-phase HPLC column (40%
CH3CN/60% H2O, 3.5 mL/min) to obtain 14.2 mCi (525 MBq) of
pure [18F]fluorophenyl methyl sulfone, which eluted at 4.50 min
(65% yield, decay corrected, 112 min). Dry [18F]fluorophenyl
methyl sulfone was placed in a pear-shaped flask under a stream
of argon, and pseudocarrier 16 was added (3 mg, 14 µmol) and
dissolved in dry THF (2 mL). The reaction vial was capped and
cooled to -78 °C, and n-BuLi (70 µL, 110 µmol) was added
dropwise by syringe until a yellow color persisted. The reaction
was stirred for 10 min, and propionamide 6 was added (30 mg,
120 µmol), at which point the yellow color disappeared. The
resulting solution was allowed to warm to room temperature and
was stirred for 15 min. The mixture was quenched with saturated
ammonium chloride (30 µL) and then injected through a Teflon
filter onto a reverse-phase HPLC (50% CH3CN/50% H2O, 3.0 mL/
min) to obtain 894 µCi of product eluted at 27.02 min (35% yield,
decay corrected, 293 min). The total yield was 23% (decay
corrected, 405 min). 18F-1 was identified by co-injection with an
authentic sample on HPLC.
3-(4-[76Br]Bromo-benzenesulfonyl)-N-(4-cyano-3-trifluorom-
ethyl-phenyl)-2-hydroxy-2-methyl-propionamide (76Br-19). 76Br-
was obtained from an isotopically enriched Cu76Se-coated tungsten
target that was subjected to proton bombardment, and an aliquot
containing 5.8 mCi (215 MBq) was transferred to a small reaction
vial in a 0.6 N NH4OH solution. The bromine-76-containing NH4-
OH solution was passed over a C-18 separatory column that had
been previously treated with H2O (3 mL). After the NH4OH was
pushed through the column, it was followed with EtOH (300 µL).
The resulting solution was placed in a glass reaction vial, and the
solvent was removed using heat (90 °C) and a stream of N2. A 1%
HOOAc/HOAc (500 µL) solution was placed in the dry vial
containing 76Br- along with propionamide 19 (2.3 mg, 3.3 µmol),
and this mixture was stirred at room temperature for 20 min. A
400 µL portion of a 50% THF/50% H2O solution was added to the
vial, and the resulting mixture was taken up into a syringe (1 mL)
and injected through a Teflon filter onto a reverse-phase HPLC
column (40% THF/60% H2O, 4.0 mL/min) to obtain 1.65 mCi of
4-[76Br]bromobicalutamide, which eluted at 10.08 min (29%, decay
corrected, 65 min). [76Br] product was identified by co-injection
with an authentic sample on HPLC. An aliquot (194 µCi, 7.18 MBq)
was taken and combined with CH3CN (1 mL), and the solvent was
removed under reduced pressure and heat. To the resulting dry flask
was added EtOH (500 µL) followed by saline (4.5 mL). The
resulting solution was taken up into 26 fractions for biodistribution.
3-(4-Bromo-phenylsulfanyl)-N-(4-[76Br]cyano-3-trifluoromethyl-
N-(4-Cyano-3-trifluoromethyl-phenyl)-2-hydroxy-2-methyl-
3-(4-tributylstannanyl-phenylsulfanyl)-propionamide (24). Pro-
pionamide 23 (416 mg, 0.910 mmol) was placed in a flame-dried
round-bottomed flask (100 mL), fitted with a magnetic stirring bar,
and was dissolved in dry toluene (50 mL). TEA (660 µL, 9.10
mmol), bis(tributyltin) (2.3 mL, 4.55 mmol), and tetrakis(triph-
enylphosphine)palladium(0) (10 mg) were then added, and the
mixture was refluxed for 24 h. The volatile solvents were removed
under reduced pressure, and the crude mixture was purified with
flash chromatography using 30% EtOAc/70% hexanes to afford a
pure product (76 mg, 0.11 mmol) as a clear oil in 12% yield. Rf )
0.26 in 30% EtOAc/hexanes. 1H NMR (500 MHz, CDCl3) δ: 9.02
(s, 1H), 7.95 (d, J ) 2.04 Hz, 1H), 7.83 (dd, J ) 2.14, 8.47 Hz,
1H), 7.73 (d, J ) 8.47 Hz, 1H), 7.33 (AA’XX’, J ) 12.65 Hz,
2H), 7.32 (AA’XX’, J ) 12.54 Hz, 2H), 3.71 (d, J ) 14.15 Hz,
1H), 3.22 (d, J ) 14.15 Hz, 1H), 1.48 (m, 6H), 1.30 (sextet, J )
7.40 Hz, 6H), 1.00 (t, J ) 8.04 Hz, 6H), 0.87 (t, J ) 7.18 Hz, 9H).
13C NMR (125 MHz, CDCl3) δ: 173.14, 131.79, 141.32, 137.15,
135.75, 133.94 (q,3JCF ) 33.14 Hz), 133.54, 129.95, 129.82, 122.05
(q,2JCF ) 274.34 Hz), 121.74, 117.19 (q,4JCF ) 4.60 Hz), 115.44,
104.51 (q,4JCF ) 1.84 Hz), 75.67, 44.55, 28.97, 27.28, 13.61, 9.53.
HRMS (ESI, Q-TOF) calcd, 671.1941; found, 671.1908.
3-(4-Bromo-phenylsulfanyl)-N-(4-cyano-3-trifluoromethyl-
phenyl)-2-hydroxy-2-methyl-propionamide (23) from N-(4-Cy-
ano-3-trifluoromethyl-phenyl)-2-hydroxy-2-methyl-3-(4-tribu-
tylstannanyl-phenylsulfanyl)-propionamide (24). NH4Br (4 mg,
41 µmol) was placed in a conical vial (5 mL), dissolved in 1.5%
HOOAc/HOAc (500 µL) solution, and stirred for 10 min, during
which time the solution turned a pale-amber color. At this point,
propionamide 23 (26 mg, 39 µmol) was added, and the mixture
was stirred at room temperature open to the atmosphere for 11 min.
The reaction was then diluted with H2O (300 µL) and passed over
a C-18 column. H2O (3 × 1 mL) was pushed through the column
followed by 10 mL of air. This was followed by CH2Cl2 (3 × 1
mL) in which the product was eluted. The CH2Cl2 fractions were
combined, dried with Na2SO4, and filtered. The resulting solution,
containing a mixture of sulfoxide and sulfone compounds, was
treated with a solution of diethyl chlorophosphite (100 µL, 0.916
mmol) in 400 µL of CH2Cl2 and stirred at room temperature for
20 min. The volatile solvents were removed under reduced pressure,
and the product was purified with flash chromatography using 20%
EtOAc/80% hexanes to give the desired product in 34% yield (6
mg, 13 µmol).
3-(4-Bromo-phenylsulfanyl)-2-hydroxy-2-methyl-N-(4-nitro-
3-trifluoromethyl-phenyl)-propionamide (26). 4-Bromobenzene
thiol (188 mg, 0.995 mmol) was added to a flame-dried round-
bottomed flask (100 mL), fitted with a stirring bar, and was
dissolved in dry THF (30 mL) and cooled to 0 °C. At this point,
NaH (60%) (40 mg, 1.0 mmol) was added, and the mixture was
allowed to stir for 5 min. While the above reaction was stirring,
propionamide 22 (144 mg, 0.497 mmol) was added to a flame-
dried pear-shaped flask (50 mL) and dissolved in dry THF (5 mL)
and also cooled to 0 °C. The two solutions were combined through
a cannula, and the resulting mixture was slowly warmed to room
temperature and stirred for 5 h. The reaction was quenched by the
addition of a saturated ammonium sulfate solution (10 mL) and
extracted with CH2Cl2 (3 × 40 mL). The organic layers were
combined and dried with Na2SO4, and the volatile organics were

1038 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 5
Parent et al.
phenyl)-2-hydroxy-2-methyl-propionamide (76Br-23). 76Br (670
µCi, 24.7 MBq) was delivered in an ammonium hydroxide solution
that had been worked up as previously described. The resulting
solution was placed in a glass reaction vial, and the solvent was
removed using heat (90 °C) and a stream of N2. Propionamide 24
(6.0 mg, 8.9 µmol) was placed in the 76Br-containing vial along
with 1% HOOAc/HOAc (400 µL) and was stirred at room
temperature for 15 min. H2O (500 µL) was added, and the resulting
cloudy mixture was taken up into a 1 mL syringe and passed over
a C-18 separatory column that had previously been washed with
H2O (2 mL). The column containing the radioactive compound was
then flushed with H2O (2 × 1 mL) and air (2 × 1 mL). The product
was eluted from the column using Et2O (2 × 1 mL), and the organic
layers were combined and dried using Na2SO4, and the solvent was
removed using N2. CH2Cl2 (400 µL) was added to the dry vial
containing the crude mixture followed by diethyl chlorophosphite
(5 µL, 0.05 µmol). The reaction was stirred for 5 min and then
combined with a 50% THF/50% H2O solution. The resulting
mixture was taken up into a 1 mL syringe and injected through a
Teflon filter onto a semipreparatory reverse-phase HPLC column
(45% THF/65% H2O, 4.0 mL/min) to obtain 28 µCi of product
that eluted at 12.51 min (4%, decay corrected, 125 min). 4-[76Br]-
bromo-thiobicalutamide product was identified by co-injection with
an authentic sample on HPLC.
Animal Biodistribution Study. In the following experiments,
animals were handled in accordance with the Animal Studies
Committee at Washington University, School of Medicine. A
complete description of the animal handling procedure, including
animal care, anesthesia, and monitoring, can be found in ref 67.
In the rat biodistribution study, purified (76Br-19) was reconsti-
tuted in 10% ethanol-saline and injected (iv, tail vein) into mature
male Sprague-Dawley rats (250 g) castrated 7 days prior to the
experiment. Doses employed were 4 and 7 µCi/animal, respectively,
at the two time points (in 150 and 260 µL volumes, respectively),
and animals were sacrificed at 1 and 18 h postinjection. To
determine whether uptake was mediated by a high-affinity, limited-
capacity system, one set of animals was left with testes intact to
provide saturation of the AR by the endogenous androgens. At 1
and 18 h after the injection of the 76Br-tracer, groups of five animals
each were killed, tissues of interest were removed, weighed, washed
with saline, blotted dry, and the radioactivity was counted. The
percent injected dose in each tissue was calculated by comparison
to injected dose standards of appropriate count rates.
centrifuged at 3000 rpm for 4 min to separate the plasma and
cellular fractions, and the individual fractions were counted in a
well counter. The plasma was then treated with CH3CN (1 mL)
and centrifuged as before, and the supernatant was separated from
the precipitated debris. The fractions were again counted, with the
bulk of the activity residing the plasma supernatant. The activity
in the supernatant was purity analyzed by radiometric thin-layer
chromatography. At the 1 h time point, the bulk of the 76Br activity
in the blood was found to be immobile with only 20% as intact
76Br-19. At the 18 h time point, all 76Br was consistent with the
complete debromination of 76Br-19.
In the CWR22 tumor implanted mice, a tumor was selected from
the DES-treated mice at each time point and ground, extracted with
CH3CN (1 mL), and analyzed as previously described. At each time
point, all 76Br was immobile, consistent with the complete debro-
mination of 76Br-19.
Acknowledgment. We thank Kathryn E. Carlson for her
assistance with RBA analysis. This work was supported in part
by DOE grants (FG02 86ER60401 to J.A.K. and FG02
84ER60218 to M.J.W.) and an NIH grant (PHS 1R24 CA86307
to M.J.W.).
Supporting Information Available: Elemental analyses of new
derivatives 7, 17, 19, 23, and 26. This material is available free of
charge via the Internet at http://pubs.acs.org.
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mature male mice (25 g) having a previously implanted tumor
prostate (CWR22) in the flank. CWR22 implanted mice had been
injected subcutaneously with DES (0.2 mg) in sesame oil (0.1 mL)
24 and 3 h prior to the injection of the tracer to suppress endogenous
androgen biosynthesis.56 Doses of (76Br-19) employed were 6 µCi/
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90 min postinjection. To ascertain whether tissue accumulation of
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