A hybrid solid-fluorous phase radioiodination and purification platform

Article abstract of DOI:10.1002/jlcr.3214

A new class of fluorous materials was developed to create a hybrid solid-solution phase strategy for the expedient preparation and HPLC-free purification of ¹²⁵I-labeled compounds. The system is referred to as a hybrid platform in that it combines solution phase labeling and fluorous solid-phase purification in one step as opposed to two separate individual processes. Treatment of fluorous arylstannanes coated on fluorous silica with [¹²⁵I]NaI and the appropriate oxidant made it possible to produce and selectively isolate the nonfluorous radiolabeled products in high purity (>98%) free from excess starting material and unreacted radioiodine. Examples included simple aryl and heterocyclic (click) derivatives, known radiopharmaceuticals including meta-iodobenzylguanidine (MIBG) and iododeoxyuridine (IUdR), and a new agent with high affinity for prostate-specific membrane antigen. The coated fluorous silica kits are simple to prepare, and reactions can be performed at room temperature using different oxidants generating products in minutes in biocompatible solutions. Copyright

Full text of DOI:10.1002/jlcr.3214

Research Article
Received 23 December 2013,
Revised 21 May 2014,
Accepted 29 May 2014
Published online 28 July 2014 in Wiley Online Library
(wileyonlinelibrary.com) DOI: 10.1002/jlcr.3214
A hybrid solid-fluorous phase radioiodination
†
and purification platform
James P. K. Dzandzi, Denis R. Beckford Vera, and John F. Valliant*
A new class of fluorous materials was developed to create a hybrid solid-solution phase strategy for the expedient
1
25
preparation and HPLC-free purification of
I-labeled compounds. The system is referred to as a hybrid platform in that it
combines solution phase labeling and fluorous solid-phase purification in one step as opposed to two separate individual
1
25
processes. Treatment of fluorous arylstannanes coated on fluorous silica with [ I]NaI and the appropriate oxidant made
it possible to produce and selectively isolate the nonfluorous radiolabeled products in high purity (>98%) free from excess
starting material and unreacted radioiodine. Examples included simple aryl and heterocyclic (click) derivatives, known
radiopharmaceuticals including meta-iodobenzylguanidine (MIBG) and iododeoxyuridine (IUdR), and a new agent with high
affinity for prostate-specific membrane antigen. The coated fluorous silica kits are simple to prepare, and reactions can be
performed at room temperature using different oxidants generating products in minutes in biocompatible solutions.
Keywords: labeling methods; I-125; instant kits; fluorous; MIBG; IUdR
Introduction
which is associated with the heterogeneous nature of the
reaction mixture and nonspecific binding of the product and
isotope to the support. Solid-phase labeling can also require
Radiopharmaceuticals are typically produced using ‘just-in-time’
manufacturing methods where radioactive decay necessitates
expedient and efficient synthesis and purification methods. For
many targeted small molecule radiopharmaceuticals, unlike for
more traditional perfusion-type agents, HPLC is necessary to
separate the desired product from impurities and the large
excess of unlabeled precursor that is often used in radiolabeling
reactions. HPLC purification has a number of limitations
particularly for routine production of radiopharmaceuticals in
that it is time-consuming, requires extensive validation efforts
for agents being translated to clinical use, and adds the risk of
instrument failure during production runs.
4
heating and/or use of organic solvents.
One approach to addressing these limitations is to combine
fluorous and solid-phase labeling methods. Fluorous precursors
can be prepared, purified, and fully characterized using traditional
solution-phase methods and then the material loaded onto a solid
support by physisorption (taking advantage of the fluorine–fluorine
interactions) to create a hybrid fluorous-solid-phase system. The
product would be released from the support upon labeling because
it is rendered ‘nonfluorous’. The advantage of loading the material
onto the fluorous support, as opposed to labeling and then passing
the mixture through a FSPE cartridge, is that the combined system
could be used to create a single step ‘instant kit’, which would
minimize handling of the radioactive solutions and facilitate clinical
translation. Such a system, including the preparation of the fluorous
coated materials, was developed here for labeling and purifying a
range of different molecules with iodine-125.
To eliminate the need for HPLC, alternative labeling and
purification methods employing solid-phase synthesis and solid-
phase extraction (SPE) have been developed for a variety of
medical isotopes. These include systems based on polymer-
1
–7
8–11
supported precursors
and fluorous-tagged molecules.
In
solid-phase labeling, compounds are linked to insoluble supports
via covalent bonds or ionic interactions in a way that the desired
product is released upon labeling and isolated by simple filtration.
For the fluorous labeling strategy (FLS),
precursors, which are prepared and purified using traditional
synthetic methods,
upon labeling. The fluorous precursor is separated from the
desired radiolabeled compound by passing the reaction mixture
through a fluorous SPE (FSPE) cartridge.
Results and discussion
8–12
fluorous-tagged
Previous work on the FLS involved labeling fluorous tin
derivatives in solution and then isolation of the products
subsequently using a FSPE cartridge. Here, the goal was to
develop a different paradigm where labeling takes place directly
1
3,14
are converted to nonfluorous analogues
10,15–17
Department of Chemistry and Chemical Biology, McMaster University, Hamilton,
ON L8S 4M1, Canada
The advantage of the solid-phase system is that labeling and
purification is carried out in a single step. Unfortunately, the
inability to purify cross-linked polymer derivatives limits this *Correspondence to: John F. Valliant, Department of Chemistry and Chemical
Biology, McMaster University, Hamilton, ON, L8S 4M1, Canada.
E-mail: valliant@mcmaster.ca
method to the small number of loading reactions that proceed
in quantitative yield. Groups developing solid-phase labeling
systems have in certain instances also reported reduced
†
Additional supporting information may be found in the online version of this
radiochemical yields compared with solution phase methods, article at the publisher’s web site.
J. Label Compd. Radiopharm 2014, 57 551–557
Copyright © 2014 John Wiley & Sons, Ltd.

J. P. K. Dzandzi et al.
on a hybrid fluorous-solid-phase material such that the product, combination of materials was washed with water followed by
free from residual starting materials and impurities, can be different alcohol-water mixtures. The aqueous fractions did not
eluted directly and selectively.
contain any para-iodobenzoic acid, whereas the desired product
The initial focus was to determine the range of loadings that was eluted quantitatively using an 80:20 (v/v) MeOH-water mixture.
can be achieved on fluorous silica (FS), which was carried out None of the fractions contained any detectable amount of 1a.
using a simple fluorous-tin benzoic acid (FBA) derivative 1a
One of the concerns raised over using arylstannanes is their
(
Figure 1), which can be prepared using a commercially available potential toxicity, where the recommended parenteral limit for
18
20
fluorous tin bromide following a minor modification of a tin is 300 ppm. To further demonstrate that the FS is able to
previously published method. To prepare silica coated with tin effectively retain the tin precursors, a fluorous-tin derivative of
8
precursor, varying quantities of 1a as a 500 mg/mL solution in fluorescein was prepared and loaded onto FS. This provided a
CHCl were added to FS. The resulting chloroform-silica slurry convenient tool to visualize the distribution of the fluorous
3
was agitated periodically and the solvent allowed to evaporate precursor on the silica after loading and washing. Compound
to give loading ranges of 100–500 mg/g of coated FS in 50 mg/ 3a (Scheme 1) was prepared by coupling the fluorous-tin
g increments. The hybrid fluorous-solid-phase labeling and benzylamine 2a to fluorescein 5(6)-isothiocyanate, which was
purification cartridges were prepared by first loading normal achieved in 71% yield. FS(300)-3a was prepared as previously
(uncoated) FS (500 mg) that had been preconditioned with described for 1a, where visually the precoated fluorous-tin dye
DMF, H O, and 80:20 (v/v) MeOH/H O into a polypropylene SPE was clearly retained on the top portion of the FS. There was little
2
2
tube (3 mL) followed by a sample (50 mg) of coated FS. Each change after washing with water and 80:20 alcohol/H O
2
cartridge was capped with a polyethylene frit and washed with (Figure 2), and the precursor remained bound to the FS and
H O followed by 80:20 MeOH/H O where fractions (1 mL) were was not detected spectroscopically in any fraction where the
2
2
collected and analyzed by HPLC to determine if any 1a leached detection limit for 3a was 6 μg/mL (6 ppm), which is well below
from the support. (50×) the USP recommended limit. Inductively coupled plasma
Based on HPLC analysis, there was no elution of the tin mass spectrometry analysis was also performed on the product
19
precursor in the 100–300 mg/g samples of FS-1a. However, and showed that there was no tin present above the detection
the tin compound was detected in samples containing higher limit of the instrument (1 ppb).
loadings (400–500 mg/g). Initial experiments were therefore
Radiochemical experiments were performed subsequently
125
performed with the 200 mg/g (FS(200)-1a) material. To identify using Na I and a range of fluorous compounds to test the
the optimal elution conditions, a 50 mg sample of FS(200)-1a general utility of the approach and to allow for comparison to
that also contained para-iodobenzoic acid (10 mg) was loaded previously reported solution phase work. For the initial tests, a
onto a sample of preconditioned unmodified FS (500 mg). This cartridge containing 50 mg of FS(200)-1a and preconditioned
FS (500 mg) giving a ratio of loaded material to FS of 1:10 w/w
2
was prepared. EtOH/H O (80:20, pH adjusted to 3–4 with AcOH)
125
was added followed by iodogen and Na I (3.7–7.4 MBq). The
reaction was allowed to proceed for 20 min and then quenched
with aqueous Na
residual salts and unreacted Na I. The desired product was
obtained by elution with 80:20 EtOH/H O (5 mL), which was used
in place of MeOH/H O to ensure biocompatibility upon dilution
2 2 5
S O followed by a water wash to remove any
125
2
2
21
of the product with isotonic saline or buffer. HPLC analysis
revealed no evidence of 1a in the ultraviolet (UV)-trace and a
single peak in the γ-trace. The identity of the peak was confirmed
by comparing its retention time to that for an authentic sample
of para-iodobenzoic acid (Figure 3). The product was obtained
in 97% radiochemical purity and 49 ± 3% (n = 3) isolated
radiochemical yield. There was some small amount of residual
activity on the FSPE cartridge and the three-way-valve attached
to the polypropylene SPE tube. The remainder of the activity
125
was unreacted Na I, which was detected in the initial aqueous
fractions.
Following the successful proof of concept experiment with FS
200)-1a, the general utility of the method was evaluated using
Figure 1. Schematic representation of the hybrid solid-fluorous phase
radioiodination and purification system. R’ = (CH ) (CF ) CF . Additional examples
2 2 2 5 3
(
of compounds tested are shown in Scheme 2.
other previously reported fluorous-precursors. The fluorous-tin
Scheme 1. Synthesis of the fluorous-tin fluorescein derivative 3a.
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Copyright © 2014 John Wiley & Sons, Ltd.
J. Label Compd. Radiopharm 2014, 57 551–557

J. P. K. Dzandzi et al.
In all cases, radiochemical purities were greater than 95%
while isolated radiochemical yields ranged from 30% to 49%,
except for the nitrobenzene derivative where the isolated yield
was less than 5% (Table 1). For the anisole derivative 5b, the
yields were higher than for the phenyl (4b) and nitro (6b)
derivatives, which is expected given the electrophilic nature of
the starting material. The yields reported are lower than for the
traditional FLS reactions but were comparable with yields
4
reported for polymer supported aryltrifluoroborates.
The coated FS system was also evaluated using a series of
simple benzamides including an analogue of N-(2-(diethylamino)
ethyl)-4-iodobenzamide (BZA), an agent that has been evaluated
22
as a SPECT agent for imaging melanoma. The fluorous
precursors 7a–9a were prepared via the tetrafluorophenol (TFP)
8
active ester of 1a. The purified products were coated onto FS
using the chloroform evaporation method to give FS(200)-7a, FS
(
200)-8a, and FS(200)-9a, which were loaded onto FS (1:10 w/w).
Upon labeling, the yields for 7b, 8b, and 9b were 42 ± 4%,
3 ± 6%, and 36 ± 2%, respectively, with radiochemical purities
4
greater than 98% in all cases. The yields were again lower than
the corresponding solution phase method, which were 78 ± 5%,
81 ± 2%, and 70± 3%, respectively. Elution of 7b was not
successful with 80:20 EtOH/H O as the majority of the product
2
was retained on the FSPE cartridge. Because of the basicity of
the tertiary amine, a small amount of acid (0.1% TFA) was needed
to elute the product.
Figure 2. Fluorescein derivative 3a (yellow color) loaded on unmodified fluorous
silica gel. The picture shows the cartridge after loading and elution with water and
8
2
0:20 EtOH/H O.
The system was also effective in producing meta-iodoben-
zylguanidine (MIBG, 10b), a radiopharmaceutical which is used for
23
compounds spanned simple aryl derivatives to known and imaging and treating neuroendocrine tumors. The yield obtained
emerging radiopharmaceuticals (Scheme 2). The FS-coated with the one-step radioiodination was 40 ± 6%, which is a twofold
materials (200 mg/g) were prepared and labeled as previously and 1.5-fold reduction in yield compared with the solution phase
described, and all reactions were performed in head-to-head FLS labeling and an existing polymer supported MIBG labeling
2
comparisons with solution phase (two steps) FLS reactions.
method, respectively. However, the radiochemical purity of the
A
B
C
D
Figure 3. (A) γ-HPLC chromatogram of 1b; (B) UV-HPLC chromatogram of the same sample; (C) γ-HPLC chromatogram of 1b co-injected with a cold reference standard; (D)
UV-HPLC chromatogram of the same sample. The small difference in the retention times between the UV and the corresponding γ-trace is due to the time lag between the
detectors, which are connected in series (elution method A). The peak and change in the baseline between 14.5 and 15.5 min is a result of a rapid change in the gradient.
J. Label Compd. Radiopharm 2014, 57 551–557
Copyright © 2014 John Wiley & Sons, Ltd.
www.jlcr.org

J. P. K. Dzandzi et al.
Scheme 2. Basic radioiodination reaction, fluorous precursors and radioiodinated products.
unreacted iodide. To test this, a new and polar heterocyclic
iodine prosthetic group known as the triazole-appending agent
Table 1. Radiochemical yields for solution (fluorous) and
hybrid fluorous-solid-phase radioiodination reactions with
different oxidants
24
(TAAG) was investigated as a substrate. The fluorous TAAG
precursor 11a could be effectively loaded onto FS to give FS
(200)-11a which when loaded onto FS (1:10 w/w) showed no
Iodogen
Solution
Chloramine-T
Coated
Precursor
evidence of breakthrough when using 80:20 EtOH/H
2
O. Upon
Coated
radioiodination however, some of the desired product, 11b,
125
1
4
5
6
7
8
9
1
1
1
1
a
a
a
a
a
a
a
0a
1a
2a
3a
83 ± 2
80 ± 2
86 ± 3
13 ± 5
78 ± 5
81 ± 2
70 ± 3
80 ± 3
78 ± 5
81 ± 3
—
49 ± 3
30 ± 4
45 ± 5
≤5
42 ± 4
43 ± 6
36 ± 2
40 ± 6
45 ± 3
48 ± 6
—
75 ± 6
47 ± 8
73 ± 3
—
72 ± 12
—
83 ± 6
63 ± 10
—
67 ± 2
57 ± 3
eluted in the 100% aqueous wash along with free [ I]NaI. To
address this, a C-18 SPE cartridge was connected in series to
the FSPE cartridge so that after elution with water the
radioiodinated product was retained and subsequently selective
2
eluted in 45 ± 3% radiochemical yield using 80:20 EtOH/H O.
The utility of the hybrid labeling system was tested further using
a novel TAAG derivative that can bind to prostate-specific
24
membrane antigen, a protein that is over expressed on prostate
25,26
cancers and associated metastases.
onto F-silica to give FS(200)-12a (1:10 w/w) and labeled with Na I.
The desired product 12b was eluted with 80:20 EtOH/H O in
8 ± 6% radiochemical yield (n= 3) with a radiochemical purity that
was greater than 98%, which is comparable with that for the
Compound 12a was loaded
125
2
4
product was greater than 98%, and loading the material onto FS solution phase method. To test whether or not the cartridges can
was simple and optimized in a couple of hours whereas be used multiple times, following the elution of the product, the
developing a method to produce polymer supported MIBG labeling of FS(200)-12a was repeated using the same cartridge,
2
quantitatively was nontrivial.
which was washed with water followed by 80:20 EtOH/H O. The
2
One of the potential limitations of the fluorous system is in yield for the subsequent labeling was 30 ± 6% and the product
using FSPE to purify polar molecules which could co-elute with isolated in 90% radiochemical purity. A third labeling was
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Copyright © 2014 John Wiley & Sons, Ltd.
J. Label Compd. Radiopharm 2014, 57 551–557

J. P. K. Dzandzi et al.
performed, where the yield and radiochemical purity decreased to dichloromethane, and tetrahydrofuran (THF) were distilled using a PURE
®
SOLV distillation system. FC-72 was purchased from 3M; (CF
3
(CF
2 5 2
) (CH )
1
2 ± 7 and 75%, respectively, indicating that the cartridges are best
2
)
3
SnPh and (CF
3
(CF
2
)
5
(CH
2
)
2
)
3
SnH were purchased from Fluorous
suited for single use applications.
®
Technologies Inc. SiliaFlash P60 Silica gel from SiliCycle was used for
silica gel chromatography. Analytical thin-layer chromatograms (Merck
F254 silicagel on aluminum plates) were visualized using ultraviolet light.
Compounds 1a, 2a, and 4a–12a were prepared according to literature
methods.
Not all molecules can be iodinated effectively with iodogen;
consequently, the general utility of the system with other oxidants
was also explored. Preliminary experiments using peracetic acid
were found to give inconsistent radiochemical yields. Chloramine-
T in contrast showed that comparable or superior yields compared
8,9,12,24
1,3,5,7-Tetramethyl-2,4,8-trioxa-(2,4-dimethoxyphenyl)-
6
-phosphaadamantane ligand for cross coupling reactions was
with iodogen could be obtained using less precursor. Isolated yields generously provided by Prof. Alfredo Capretta (McMaster University,
3
1
of 65 ± 5%, 71 ± 3%, and 70 ± 2% (n= 3) were obtained using 30 mg Hamilton, Ontario). KF/silica stationary phase contained 10% w/w of
of FS(30)-1a, FS(50)-1a, and FS(100)-1a. With chloramine-T, it was KF and 90% w/w SiliaFlash P60 silica gel (finely ground together) loaded
in a disposable glass pipette plugged with glass wool. Empty fritted
polypropylene SPE tubes were purchased from Sigma-Aldrich. SepPak
advantageous to connect the FSPE cartridge to a C18 SPE cartridge
and to acidify the 80:20 EtOH/H O eluent with dilute phosphoric
2
acid. This eliminated the need to collect fractions and resulted in
selective separation of the desired product from free iodide. For
example, using this system isolated radiochemical yields of
®
Plus C18 cartridges were purchased from Waters Corporation. Sodium
1
25
[
I]iodide with a specific activity of ~17 Ci/mg was provided by the
McMaster Nuclear Reactor (Hamilton, ON, Canada).
125
Caution:
I is radioactive and should only be handled in an
75 ± 6% (n= 5) and radiochemical purity greater than 95% were
appropriately equipped and licensed facility.
obtained for 1b. To demonstrate the elution conditions did not
cause protodestannylation, compound 5a was incubated in the
Instrumentation
acidified 80:20 EtOH/H O solution and samples analyzed by HPLC
2
at 5 and 40 min, where there was no evidence of anisole at either NMR spectra were recorded using Bruker DRX-500 and 600 spectrometers
time point. The system remains biocompatible as the eluted with chemical shifts reported in parts per million relative to the residual
1
proton signal of the deuterated solvent ( H NMR) or the carbon signal of
product when added to PBS was isotonic and within a pH and
13
the solvent ( C NMR). Reactions requiring microwave heating were
performed using a Biotage Initiator 60 instrument. Infrared (IR) spectra
were acquired using a BioRad FTS-40 FT-IR spectrometer. ESI mass
spectrometry experiments were performed on a Waters/Micromass
Quattro Ultima instrument, where samples were first dissolved in
methanol. High resolution mass spectral data were obtained using a
Waters-Micromass quadrupole/time-of-flight Ultima Global spectrometer.
radioactivity concentration range suitable for injection.
As a result of the increased yield with chloramine-T at reduced
ligand loading levels, several of the fluorous derivatives previously
labeled using iodogen were radioiodinated using chloramine-T. Yields
ranged from 47% to 83% (Table 1), where the radiochemical purity
was greater than 95% for all products. In terms of specific activity,
the limit of detection for 1b was determined, and the value was Elemental analyses were performed at the McMaster University
greater than 240 Ci/mmol (average of three experiments). As an Combustion Analysis and Optical Spectroscopy facility. HPLC was
performed using a Varian ProStar Model 230 instrument, fitted with a
Varian ProStar model 330 PDA detector, an IN/US γ-RAM gamma detector,
a Star 800 analog interface module, and a Phenomenex Gemini-C18
column (4.6× 100mm, 11nm, 5 μm). The wavelength for UV detection
was set at 254 nm, and the dwell time in the gamma detector was 5 s in
additional test of the labeling method, 5-iodo-2’-deoxyuridine (IUdR)-
1
3b, an agent currently undergoing investigation as therapeutic
27
radiopharmaceutical, was also produced using the chloramine-T
approach, where the isolated yield was 57% ± 3%. In general, the
isolated yields obtained using chloramine-T are comparable or higher
than those previously reported for other solid-phase radioiodination
a 10 μL loop. The mobile phase was composed of solvent A = H
TFA) and solvent B = CH CN (0.1% TFA). Method A: 0–10min, 40–100% B;
0–14 min, 100% B; 14–15 min, 100–40% B; 15–20 min, 40% B. Method B:
was evaluated over 2 months after storage at 4 °C, where there was 0–10 min, 2–100% B; 10–14 min, 100% B; 14–15 min 100–2% B; 15–
2
O (0.1%
3
2,4,28–30
methods.
It should also be noted that the coated material
1
no significant change in radiochemical yield or purity.
18 min 2% B. Method C: 0–1 min, 40% B; 1–7 min, 40–100% B, 7–12min,
100% B; 12–13 min, 100–40% B, 13–18 min 40% B. Method D: 0–1 min,
20% B; 1–7 min, 20–100% B, 7–12 min, 100% B; 12–13 min, 100–20% B,
13–18 min 20% B. Method E: 0–5 min, 5% B; 5–12 min, 5–100% B; 12–
Conclusion
The reported hybrid fluorous-solid phase labeling material is a 13 min 100–5% B, 13–18 min 5% B. For the anisole stability test, HPLC
was performed using a Waters 1525 Binary HPLC system fitted with a
convenient platform for producing radioiodinated compounds
2998 photodiode array detector and a Bioscan γ detector. A Phenomenex
in high purity and effective specific activity (i.e., free from any
residual precursor) without the need to use HPLC. An advantage
of the hybrid system over covalent polymer modification is that
the precursor compounds can be prepared and fully
characterized prior to immobilization, which is convenient and
can be carried out using a wide range of compounds. Reactions
Gemini column (5μm, 4.6 Å 250 mm, C18) at a flow rate of 1.0mL/min and
monitoring at 215 and 254nm was employed. The mobile phase was
composed of solvent A = H O (0.1% TFA) and solvent B = CH CN (0.1%
2 3
TFA). Method F: 0–15min, 20–100% B; 15–25 min, 100% B. For calibration
curves, each calibration solution was evaluated in triplicate and the data
analyzed by the least-squares method. The limit of quantitation and the
were performed at room temperature using either iodogen or limit of detection were calculated using the standard deviation method.
chloramine-T and reached completion within 20 min, and the
system did not require the use of organic solvents (other than
ethanol). All products can be isolated in biocompatible solvents
ready for injection by simple dilution with isotonic saline or PBS.
3
1-(3’,6’-Dihydroxy-3-oxo-3H-spiro[isobenzofuran-1,9’-xanthen]-
6-yl)-3-(3-(tris(2-perfluorohexylethyl)stannyl)benzyl)thiourea (3a)
To a solution of compound 2a (50 mg, 0.039 mmol) in DMF (5 mL) was
added fluorescein 5(6)-isothiocyanate (41 mg, 0.11 mmol) and the
reaction mixture stirred at room temperature overnight. The solution
was subsequently concentrated to dryness, FC-72 was added (10 mL)
and the solution extracted with DCM (3 × 5 mL). FC-72 was removed by
rotary evaporation and the desired product isolated using column
chromatography eluting with methanol/DCM (1:9, v/v) yielding 3a as
Experimental
Reagents and general procedures
Unless otherwise stated, all chemical reagents were purchased and used
as received from Sigma-Aldrich without further purification. Toluene,
J. Label Compd. Radiopharm 2014, 57 551–557
Copyright © 2014 John Wiley & Sons, Ltd.
www.jlcr.org

J. P. K. Dzandzi et al.
1
an orange solid. Yield (46 mg, 71%). H NMR (600 MHz, MeOD-d
4
) δ 8.13
was added, and the system washed with water (5 mL) followed by
(s, 1H), 7.78–7.76 (m, 1H), 7.59 (s, 1H), 7.42–7.39 (s, 3H), 7.14–7.12 (m,
3 4 2
1.5:200:50 (v/v/v) H PO /EtOH/H O (5 mL) to elute the desired product.
1
1
H), 6.68–6.66 (m, 4H), 6.53–6.52 (m, 2H), 4.88 (s, 2H), 2.47–2.38 (m, 6H),
HPLC retention times were compared with those of nonradioactive
authentic standards.
+
.42–1.29 (m, 6H); HRMS (ESI ) m/z calcd. for
C
52
À1
H
32
F
39
N
2
O
5
SnS
+
[M + H] 1657.0431, found: 1657.0454; FTIR (KBr, cm ): 2922, 1699,
1
592, 1206; HPLC (method B) t = 12.8 min.
R
Stability study
1
-(4-Hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)-5-(tris
Compound 5a (20 μL of a 6.9 mg/mL solution in MeOH) was added to
(2-perfluorohexyl-ethyl)stannyl)pyrimidine-2,4(1H,3H)-dione
1
3 4 2
.5:200:50 (v/v/v) H PO /EtOH/H O (160 μL). Samples were taken at 5
(13a)
and 40 min and analyzed by reverse-phase HPLC (method C).
A solution of diacetoxypalladium (4 mg, 0.02 mmol) in THF (0.5 mL) was
added to 1,3,5,7-tetramethyl-2,4,8-trioxa-(2,4-dimethoxyphenyl)-6-phosphaa-
damantane (8 mg, 0.03 mmol) in THF (0.5 mL). The resulting solution was
12
Acknowledgements
stirred for 10 min, and tris-(2-perfluorohexylethyl)stannane (650 mg,
This work was supported by the Natural Sciences and
Engineering Research Council (NSERC) of Canada and the
Ontario Institute for Cancer Research (OICR) through funding
provided by the Government of Ontario.
0
(
(
.56 mmol) in THF (0.5 mL) was added. After 10 min, 1-(4-hydroxy-5-
hydroxymethyl)tetrahydrofuran-2-yl)-5-iodopyrimidine-2,4(1H,3H)-dione
92 mg, 0.26 mmol) in THF (0.5 mL) was added and the resulting mixture was
heated in a Biotage microwave reactor at 160 °C for 15 min. The reaction
mixture was filtered through KF/silica and the solvent removed by rotary
evaporation. The desired product was isolated using column chro- Conflict of Interest
matography eluting with methanol/DCM (1:9, v/v) yielding 13a as a colorless
1
The authors did not report any conflict of interest.
4
oil. Yield (126 mg, 35%). H NMR (600 MHz, MeOD-d ) δ 7.92 (s, 1H), 6.31 (m,
1
H), 4.41 (m, 1H), 3.95 (m, 1H), 3.78–3.72 (m, 2H), 2.47–2.41 (m, 6H), 2.32–2.21
13
(m, 2H), 1.35–1.23 (m, 6H); C NMR (150 MHz, MeOD-d
4
) δ 169.3, 152.7,
+
1
C
47.7, 110.8, 89.4, 87.0, 72.6, 62.9, 41.7, 28.7, 0.0; HRMS (ESI ) m/z calcd. for References
À
À1
33 23 39 2 5
H F N O Sn [M + H] 1389.0061, found: 1389.0084; FTIR (KBr, cm ):
[
[
[
1] P. A. Culbert, D. H. Hunter, React. Polym. 1993, 19, 247–253.
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General procedure for preparing coated fluorous silica
[
Fluorous silica was added to the required concentration of the fluorous
precursor in chloroform and the mixture agitated by hand until a slurry
was formed. After sitting at room temperature overnight, the resulting
powder was added to a polypropylene SPE tube that contained 500 mg
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[
[
[
[
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of unmodified FS previously washed with DMF (1 mL), H
0:20 EtOH/H O (5 mL).
2
O (5 mL), and
8
2
2
26–235.
8] A. Donovan, F. Forbes, P. Dorff, P. Schaffer, J. Babich, J. F. Valliant,
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General procedure for solid-phase radioiodination with
iodogen
[
10] R. Bejot, T. Fowler, L. Carroll, S. Boldon, J. E. Moore, J. Declerck, V.
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8
2
0% (v/v) EtOH/H O (100 μL) (pH adjusted between 3 and 4 with
[
conc. AcOH) was added to the SPE cartridge containing the coated
FS. Iodogen (5 μL, 0.4 mg/mL in MeOH) was added followed by
1
25
[12] J. W. McIntee, C. Sundararajan, A. C. Donovan, M. S. Kovacs, A.
Na
reaction was quenched with 0.1 M Na
cartridge was washed with water (5 mL) followed by 80% EtOH/
O (5 mL), where (0.5 mL) fractions were collected. HPLC retention
I
(10 μL, 3.7–7.4 MBq) in 0.1 M NaOH. After 20 min, the
Capretta, J. F. Valliant, J. Org. Chem. 2008, 73, 8236–8243.
2 2
S O
5(aq) (50 μL), and the
[
[
[
13] W. Zhang, Tetrahedron 2003, 59, 4475–4489.
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2004, pp. 101–127.
H
2
times for all products were compared with that for authentic non
radioactive standards.
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[
[
17] J.-M. Vincent, Top. Curr. Chem. 2012, 308, 153–174.
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General procedure for solution phase (FLS) labeling with iodogen
8
341–8349.
125
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Validation and Instrument Performance Verification, 1st edn, John
Wiley & Sons, Inc., Hoboken, New Jersey, 2004, pp. 37–40.
Iodogen (5 μL, 0.4 g/mL in MeOH) followed by Na I (10 μL, 3.7–7.4 MBq
in 0.1 M NaOH) was added to the fluorous-tin precursor (100 μL, 5 mg/mL
2 2
in 5% AcOH/MeOH). After 5 min, Na S O5(aq) (50 μL, 0.1 ) was added and
the mixture diluted to 1 mL with water. The solution was then transferred
to a 2 g preconditioned FSPE cartridge. This was washed with water
[
20] General chapter on inorganic impurities, United States
pharmacopeia, USP ad hoc advisory panel on inorganic impurities.
http://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/2008-04-
10InorganicImpuritiesStim.pdf. [24 May 2013].
2
(3 mL) followed by 80:20 EtOH/H O (8 mL), and 1 mL fractions were
collected.
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[
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General procedure for solid-phase radioiodination with
chloramine-T
[
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An SPE cartridge containing the coated FS was connected to a SepPak
plus C18 cartridge. Ten percent acetic acid in EtOH (50 μL) was added,
[
1
25
followed by chloramine-T (50 μL, 4 mg/mL in water) and Na I (10 μL,
.85 GBq/mL in 0.1 M NaOH). After 20 min, Na 5(aq) (50 μL, 0.2 M)
1
2 2
S O
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J. Label Compd. Radiopharm 2014, 57 551–557

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