The first synthesis of [11C]J147, a new potential PET agent for imaging of Alzheimer's disease

Article abstract of DOI:10.1016/j.bmcl.2012.11.031

J147 was synthesized from 2,4-dimethylphenylhydrazine hydrochloride and 3-methoxybenzaldehyde in 2 steps with 71% overall yield. The precursor desmethyl-J147 was synthesized from 3-hydroxybenzaldehyde and 2,4-dimethylphenylhydrazine hydrochloride in 4 steps with 63% overall yield. [¹¹C]J147 was prepared from desmethyl-J147 with [¹¹C] CH₃OTf through O-[¹¹C]methylation and isolated by HPLC combined with solid-phase extraction (SPE) in 35-50% radiochemical yield based on [¹¹C]CO₂ and decay corrected to end of bombardment (EOB), with 370-740 GBq/μmol specific activity at EOB.

Full text of DOI:10.1016/j.bmcl.2012.11.031

Bioorganic & Medicinal Chemistry Letters 23 (2013) 524–527
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
The first synthesis of [11C]J147, a new potential PET agent for imaging
of Alzheimer’s disease
⇑
Min Wang, Mingzhang Gao, Qi-Huang Zheng
Department of Radiology and Imaging Sciences, Indiana University School of Medicine, 1345 West 16th Street, Room 202, Indianapolis, IN 46202, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
J147 was synthesized from 2,4-dimethylphenylhydrazine hydrochloride and 3-methoxybenzaldehyde in
2 steps with 71% overall yield. The precursor desmethyl-J147 was synthesized from 3-hydroxybenzalde-
hyde and 2,4-dimethylphenylhydrazine hydrochloride in 4 steps with 63% overall yield. [11C]J147 was
prepared from desmethyl-J147 with [11C]CH3OTf through O-[11C]methylation and isolated by HPLC com-
bined with solid-phase extraction (SPE) in 35–50% radiochemical yield based on [11C]CO2 and decay cor-
Received 17 October 2012
Revised 27 October 2012
Accepted 7 November 2012
Available online 22 November 2012
rected to end of bombardment (EOB), with 370–740 GBq/
l
mol specific activity at EOB.
Keywords:
[
Ó 2012 Elsevier Ltd. All rights reserved.
11C]J147
Alzheimer’s disease (AD)
Radiosynthesis
Automation
Positron emission tomography (PET)
Brain imaging
Alzheimer’s disease (AD) is the most common neurodegenera-
tive disorder and almost 30 million people suffer this disease
worldwide.1 A major limitation in finding treatment for AD has
been the lack of a reliable early diagnosis for this devastating dis-
ease.2 The search for pathology-specific neuroimaging tools is crit-
ical at the present stage, and biomedical imaging technique
positron emission tomography (PET) is one of the tools in which
it is possible to explore the changes in the brain.3 The protein
aggregations such as amyloid beta plaque (Ab) deposits or neurofi-
brillary tangles containing tau-protein are considered to be the
popular targets for the development of therapeutic solutions and
diagnostic biomarkers like in vivo PET imaging agents for AD.4
Amyloid cascade hypothesis has resulted in a number of Ab PET
tracers such as [11C]PIB5 and [18F]Amyvid (formerly known as
H3C
H311C
HN
HN
18F
N
O
3
N
S
OH
[
18F]Amyvid ([18F]AV-45)
[
11C]PIB
O
N
CF3
N
N
N
N
N
H3C
CH3
18F
O11CH3
18F]-T808
[
11C]J147
[
Figure 1. Chemical structures of previously developed [11C]PIB, [18F]Amyvid and
18F]-T808, and newly developed [11C]J147.
[
[
18F]AV-45),6 as indicated in Figure 1, currently in different stages
of clinical development and commercialization. However, only a
few papers on imaging agents selectively targeting tau aggregates
(tau hypothesis) have been published.7 Recently, a highly selective
and specific PET tracer called [18F]-T808 (Fig. 1) for imaging of tau
pathologies has been developed by Siemens.8 In vitro and preclin-
ical in vivo studies suggested [18F]-T808 may be one of new next
generation of PET AD probes, a promising candidate progressing
to human PET studies for imaging of paired helical filament tau.8
Currently, the major imaging probe discovery paradigm for AD is
based upon high affinity ligands for single disease-specific targets
such as Ab or tau. Recently, an alternative drug discovery scheme
has been explored and developed, which is based upon efficacy
in multiple cell culture models of age-associated pathologies rather
than exclusively amyloid metabolism and tau-protein, since age is
the greatest risk factor for AD.9 Using this new approach, a novel,
exceptionally potent, orally active, neurotrophic drug called J147
for cognitive enhancement and AD has been identified.9 We are
interested in the development of new PET AD imaging agents,
and we apply this new drug discovery approach to our imaging
probe discovery practice. In this Letter, we report the synthesis
of [11C]J147 (Fig. 1), for the first time.
The reference standard J147 (2) was synthesized according to
⇑
Corresponding author. Tel.: +1 317 278 4671.
E-mail address: qzheng@iupui.edu (Q.-H. Zheng).
the literature method with modifications.9 When we applied the
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.11.031

M. Wang et al. / Bioorg. Med. Chem. Lett. 23 (2013) 524–527
525
reported reaction conditions to the synthesis of aryl hydrazone 1
from 2,4-dimethylphenylhydrazine hydrochloride and 3-methoxy-
benzaldehyde in EtOH, the desired compound was not isolated. On
the contrary, we obtained a brown unstable reaction mixture
which decomposed to tar on standing. Attempts to isolate the aryl
hydrazone by prolonging the reaction time, raising reaction tem-
perature and cooling the reaction mixture also proved ineffective,
and thus, we turned our attention back to the classic synthetic
method.10 As outlined in Scheme 1, our experiment showed that
aryl hydrazone 1 can be successfully prepared by the reaction of
tion of [11C]2 from its phenolic hydroxyl precursor 6.19–22 The
radiosynthesis was performed in a home-built automated multi-
purpose 11C-radiosynthesis module, allowing measurement of
specific radioactivity during synthesis.23–25 This 11C-radiosynthesis
module includes the overall design of the reaction, purification and
reformulation capabilities of the prototype system. In addition,
11C-tracer specific activity (GBq/
lmol at EOB) can be automatically
determined prior to product delivery for compounds purified by
the HPLC-portion of the system. Briefly, analysis of the chromato-
graphic data utilized PeakSimple software (SRI Instruments, Las
Vegas, NV). Immediately following elution of the product peak,
the chromatographic data are exported to PeakSimple readable
files, and the area of the radioactivity peak is converted to GBq at
EOB by comparison to a reference calibration curve previously con-
structed using the same detector, loop and flow rate. The mass
peak from the UV chromatogram (without decay correction) is
similarly compared to a standard curve made at the same UV
wavelength, mobile phase and flow rate. Simple division of the
total EOB radioactivity peak (in GBq) by the total mass peak (in
3-methoxybenzaldehyde
with
2,4-dimethylphenylhydrazine
hydrochloride in the presence of sodium acetate in EtOH aqueous
solution. The experiment proceeded expeditiously and delivered
very good isolated yield (86%). The isolation procedure simply in-
volved the decantation of the clear solution and solidification the
sticky oil, followed by washing with hexanes and drying to obtain
high purity aryl hydrazone 1. Acetylation of 1 with trifluoroacetic
anhydride in CH2Cl2 in the presence of Et3N furnished standard 2
in 83% yield.
Initial attempts to achieve the precursor desmethyl-J147 (6) for
11C-labeling focused on desmethylation of J147. Treatment of 2
with sodium isopropyl thiolate in DMF at reflux resulted with no
desired product observed.11 Stirring 2 with trimethylsilyl chloride
(TMSCl) and NaI in acetonitrile at reflux provided only trace
amounts of the desired product.12 At this point we chose to explore
an alternative strategy to synthesize the precursor 6. As shown in
Scheme 2, the phenolic hydroxyl group of 3-hydroxybenzaldehyde
was protected as benzyl ether by reacting with benzyl bromide in
DMF in the presence of K2CO3 and KI to afford 3 in 87% yield. Con-
densation of 3 with 2,4-dimethylphenylhydrazine hydrochloride in
the presence of sodium acetate in EtOH aqueous solution gave 4 in
91% yield, which was acetylated with trifluoroacetic anhydride in
CH2Cl2 in the presence of Et3N to obtain 5 in 90% yield. Attempt
to remove benzyl group by catalytic hydrogenation 5 with 10%
Pd/C in EtOAc gave low yield. Prolonging reaction time, changing
solvent to THF/MeOH caused a decreased yield with two side prod-
ucts. Eventually, treatment 5 with that BF3ꢀOEt2-Me2S as a deben-
zylation agent in CH2Cl2 gave precursor 6 in 89% yield.13
nmoles) gives specific activity at EOB in GBq/lmol. The overall
synthesis, purification and reformulation time was 30–40 min
from EOB. The specific radioactivity was in a range of 370–
740 GBq/lmol at EOB. The specific activity can also be measured
by analytical HPLC, which is consistent with the on-the-fly tech-
nique to determine the specific activity by semi-preparative HPLC.
Chemical purity and radiochemical purity were determined by
analytical HPLC.26 The chemical purity of the precursor 6 and ref-
erence standard 2 was >96%. The radiochemical purity of the target
tracer [11C]2 was >99% determined by radio-HPLC through
c-ray
(PIN diode) flow detector, and the chemical purity of [11C]2 was
>93% determined by reverse-phase HPLC through UV flow detector.
A C-18 Plus Sep-Pak cartridge was used to significantly improve
the chemical purity of the tracer solution.19–21,26 The chemical
purity of the [11C]2 tracer solution with Sep-Pak purification was
usually increased higher 10–20% than that without Sep-Pak purifi-
cation.19–21
The octanol–water partition coefficient (commonly expressed
as LogP) is an important physical parameter directly correlated
with the biological activities of a wide variety of organic com-
pounds.27–31 LogP provides an assessment of lipophilicity that of-
ten correlates with a compound’s ability to penetrate the blood
brain barrier (BBB). We obtained calculated LogP (CLogP) value
of [11C]J147 in comparison with three other AD imaging agents
Radiosynthesis of the target tracer [11C]J147 ([11C]2) is indi-
cated in Scheme 3. The phenolic hydroxyl precursor desmethyl-
J147 (6) was labeled by [11C]methyl triflate ([11C]CH3OTf)14,15
through O-[11C]methylation16–18 in acetonitrile at 80 °C under
basic condition (NaH) and isolated by a semi-preparative high
performance liquid chromatography (HPLC) with a Prodigy C-18
column from Phenomenex and a solid-phase extraction (SPE) with
a disposable C-18 Plus Sep-Pak cartridge from Waters (a second
purification or isolation process)19–21 to produce the corresponding
pure radiolabeled compound [11C]2 in 35–50% radiochemical yield,
decay corrected to end of bombardment (EOB), based on [11C]CO2.
Addition of NaHCO3 to quench the radiolabeling reaction and to
dilute the radiolabeling mixture prior to the injection onto the
semi-preparative HPLC column for purification gave better separa-
[
11C]PIB, [18F]Amyvid and [18F]-T808 from ChemDraw Ultra 9.0
(ChemOffice 2005), and CLogP values for [11C]J147, [11C]PIB,
18F]Amyvid and [18F]-T808 are 4.55, 3.99, 3.52 and 4.05, respec-
tively. The CLogP value of [11C]J147 is higher than that of
[
[
11C]PIB, [18F]Amyvid and [18F]-T808. The data suggest [11C]J147
has higher lipophilicity to [11C]PIB, [18F]Amyvid and [18F]-T808,
more lipophilic than [11C]PIB, [18F]Amyvid and [18F]-T808. In gen-
eral, there is a suitable range of LogP value for favorable BBB pen-
etration.32 In other words, a compound with higher lipophilicity
O
H
N
HCl
+
NHNH2
CH3
(CF3CO)2O
CH3COONa
EtOH/H2O
N
H
Et3N, CH2Cl2
H3C
CH3
H3C
OCH3
OCH3
1, 86%
O
CF3
N
N
H3C
J147 (2), 83%
CH3
OCH3
Scheme 1. Synthesis of the reference standard J147 (2).

526
M. Wang et al. / Bioorg. Med. Chem. Lett. 23 (2013) 524–527
NHNH2 HCl
O
O
H
N
K2CO3, KI
H
H
N
H3C
CH3
BnBr, DMF
H3C
CH3
CH3COONa, EtOH/H2O
OH
OBn
3, 87%
OBn
4, 91%
O
N
CF3
N
O
N
CF3
BF3 Et2O
N
(CF3CO)2O
Me2S, CH2Cl2
CH3
Et3N, CH2Cl2
H3C
H3C
CH3
OBn
OH
5, 90%
desmethyl-J147 (6), 89%
Scheme 2. Synthesis of the precursor desmethyl-J147 (6).
4. Mori, T.; Maeda, J.; Shimada, H.; Higuchi, M.; Shinotoh, H.; Ueno, S.; Suhara, T.
Psychogeriatrics 2012, 12, 106.
5. Klunk, W. E.; Engler, H.; Nordberg, A.; Bacskai, B. J.; Wang, Y.; Price, J. C.;
Bergström, M.; Hyman, B. T.; Långström, B.; Mathis, C. A. Neuroimaging Clin. N.
Am. 2003, 13, 781.
6. Carpenter, A. P., Jr.; Pontecorvo, M. J.; Hefti, F. F.; Skovronsky, D. M. Q. J. Nucl.
Med. Mol. Imaging 2009, 53, 387.
7. Jensen, J. R.; Cisek, K.; Funk, K. E.; Naphade, S.; Schafer, K. N.; Kuret, J. J.
Alzheimers Dis. 2011, 26, 147.
8. Zhang, W.; Arteaga, J.; Cashion, D. K.; Chen, G.; Gangadharmath, U.; Gomez, L.
F.; Kasi, D.; Lam, C.; Liang, Q.; Liu, C.; Mocharla, V. P.; Mu, F.; Sinha, A.;
Szardenings, A. K.; Wang, E.; Walsh, J. C.; Xia, C.; Yu, C.; Zhao, T.; Kolb, H. C. J.
Alzheimers Dis. 2012, 31, 601.
O
N
CF3
O
N
CF3
[
11C]CH3OTf, CH3CN
N
N
NaH, 80 oC, 3 min
H3C
CH3
H3C
CH3
O11CH3
11C]J147 ([11C]2), 35-50%
OH
[
desmethyl-J147 (6)
Scheme 3. Synthesis of the target tracer [11C]J147 ([11C]2).
doesn’t necessarily pass the BBB easier than a compound with low-
er lipophilicity if their LogP values are in the suitable range. There-
fore, we can predict [11C]J147 has suitable ability to pass the BBB.
The published biological results of J1479 further support that
9. Chen, Q.; Prior, M.; Dargusch, R.; Roberts, A.; Riek, R.; Eichmann, C.; Chiruta, C.;
Akaishi, T.; Abe, K.; Maher, P.; Schubert, D. PLoS ONE 2011, 6, e27865.
10. Vogel, A. I.; Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R. Vogel’s
Textbook of Practical Organic Chemistry, 5th ed.; Longman: London, 1989.
11. Jones, K.; Roset, X.; Rossiter, S.; Whitfield, P. Org. Biomol. Chem. 2003, 1, 4380.
12. Mathews, W. B.; Zober, T. G.; Ravert, H. T.; Scheffel, U.; Hilton, J.; Sleep, D.;
Dannals, R. F.; Szabo, Z. Nucl. Med. Biol. 2006, 33, 15.
13. Kim, Y. W.; Hackett, J. C.; Brueggemeier, R. W. J. Med. Chem. 2004, 47, 4032.
14. Jewett, D. M. Int. J. Radiat. Appl. Instrum. A 1992, 43, 1383.
15. Mock, B. H.; Mulholland, G. K.; Vavrek, M. T. Nucl. Med. Biol. 1999, 26, 467.
16. Wang, M.; Yoder, K. K.; Gao, M.; Mock, B. H.; Xu, X.-M.; Saykin, A. J.; Hutchins,
G. D.; Zheng, Q.-H. Bioorg. Med. Chem. Lett. 2009, 19, 5636.
17. Gao, M.; Lola, C. M.; Wang, M.; Miller, K. D.; Sledge, G. W.; Zheng, Q.-H. Bioorg.
Med. Chem. Lett. 2011, 21, 3222.
18. Gao, M.; Wang, M.; Zheng, Q.-H. Bioorg. Med. Chem. Lett. 2012, 22, 3704.
19. Gao, M.; Wang, M.; Mock, B. H.; Glick-Wilson, B. E.; Yoder, K. K.; Hutchins, G.
D.; Zheng, Q.-H. Appl. Radiat. Isot. 2010, 68, 1079.
20. Wang, M.; Gao, M.; Miller, K. D.; Zheng, Q.-H. Steroids 2011, 76, 1331.
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Lett. 2012, 22, 1569.
[
11C]J147 can readily pass the BBB, and it is a promising candidate
as potential PET AD imaging agent.
The experimental details and characterization data for com-
pounds 1-6 and for the target tracer [11C]2 are given.33
In summary,
a facile synthetic route to PET radioligand
[
11C]J147 has been developed. This synthetic approach provided
J147 and its corresponding normethyl precursor desmethyl-J147
in high overall chemical yields. An automated self-designed mul-
ti-purpose
[
[
11C]-radiosynthesis module for the synthesis of
11C]J147 has been built, featuring the measurement of specific
activity by the on-the-fly technique. The radiosynthesis employed
O-[11C]methylation radiolabeling on oxygen position of the pheno-
lic hydroxyl precursor. Radiolabeling procedures incorporated effi-
ciently with the most commonly used [11C]methylating agent,
22. Gao, M.; Wang, M.; Hutchins, G. D.; Zheng, Q.-H. Appl. Radiat. Isot. 2008, 66,
1891.
23. Mock, B. H.; Zheng, Q.-H.; DeGrado, T. R. J. Labelled Compd. Radiopharm. 2005,
48, S225.
24. Mock, B. H.; Glick-Wilson, B. E.; Zheng, Q.-H.; DeGrado, T. R. J. Labelled Compd.
Radiopharm. 2005, 48, S224.
[
[
11C]CH3OTf, which was produced by gas-phase production of
11C]methyl bromide ([11C]CH3Br) from our laboratory. The target
tracer was isolated and purified by a semi-preparative HPLC com-
bined with SPE procedure in high radiochemical yields, short over-
all synthesis time, and high specific activity. These results facilitate
the potential preclinical and clinical PET studies of [11C]J147 as a
brain AD imaging agent in animals and humans.
25. Wang, M.; Gao, M.; Zheng, Q.-H. Appl. Radiat. Isot. 2012, 70, 965.
26. Zheng, Q.-H.; Mock, B. H. Biomed. Chromatogr. 2005, 19, 671.
27. Haky, J. E.; Young, A. M. J. Liq. Chromatogr. 1984, 7, 675.
28. Fei, X.; Zheng, Q.-H. J. Liq. Chromatogr. Related Technol. 2005, 28, 939.
29. Gao, M.; Mock, B. H.; Hutchins, G. D.; Zheng, Q.-H. Nucl. Med. Biol. 2005, 32, 543.
30. Gao, M.; Wang, M.; Hutchins, G. D.; Zheng, Q.-H. Bioorg. Med. Chem. Lett. 2010,
20, 2529.
31. Wang, M.; Gao, M.; Steele, B. L.; Glick-Wilson, B. E.; Brown-Proctor, C.; Shekhar,
A.; Hutchins, G. D.; Zheng, Q.-H. Bioorg. Med. Chem. Lett. 2012, 22, 4713.
32. Mathis, C. A.; Wang, Y.; Holt, D. P.; Huang, G.-F.; Debnath, M. L.; Klunk, W. E. J.
Med. Chem. 2003, 46, 2740.
Acknowledgments
This work was partially supported by Indiana State Department
of Health (ISDH) Indiana Spinal Cord & Brain Injury Fund (ISDH
EDS-A70-2-079612). 1H NMR and 13C NMR spectra were recorded
on a Bruker Avance II 500 MHz NMR spectrometer in the Depart-
ment of Chemistry and Chemical Biology at Indiana University Pur-
due University Indianapolis (IUPUI), which is supported by a NSF-
MRI grant CHE-0619254.
33. (a). General. All commercial reagents and solvents were purchased from
Sigma-Aldrich and Fisher Scientific, and used without further purification.
[
11C]CH3OTf was prepared according to a literature procedure.15 Melting points
were determined on
a MEL-TEMP II capillary tube apparatus and were
uncorrected. 1H NMR and 13C NMR spectra were recorded at 500 and
125 MHz, respectively, on a Bruker Avance II 500 MHz NMR spectrometer
using tetramethylsilane (TMS) as an internal standard. Chemical shift data for
the proton resonances were reported in parts per million (ppm, d scale) relative
to internal standard TMS (d 0.0), and coupling constants (J) were reported in
hertz (Hz). LC–MS analysis was performed on an Agilent system, consisting of
an 1100 series HPLC connected to a diode array detector and a 1946D mass
spectrometer configured for positive-ion/negative-ion electrospray ionization.
The high resolution mass spectra (HRMS) were obtained using a Waters/
Micromass LCT Classic spectrometer. Chromatographic solvent proportions are
indicated as volume: volume ratio. Thin-layer chromatography (TLC) was run
References and notes
1. Någren, K.; Halldin, C.; Rinne, J. O. Eur. J. Nucl. Med. Mol. Imaging 2010, 37, 1575.
2. Rojo, L. E.; Gaspar, P. A.; Maccioni, R. B. Curr. Alzheimer Res. 2011, 8, 652.
3. Berti, V.; Pupi, A.; Mosconi, L. Ann. N.Y. Acad. Sci. 2011, 1228, 81.

M. Wang et al. / Bioorg. Med. Chem. Lett. 23 (2013) 524–527
527
using Analtech silica gel GF uniplates (5 ꢁ 10 cm2). Plates were visualized
under UV light. Normal phase flash column chromatography was carried out
on EM Science silica gel 60 (230–400 mesh) with a forced flow of the indicated
solvent system in the proportions described below. All moisture- and air-
sensitive reactions were performed under a positive pressure of nitrogen
maintained by a direct line from a nitrogen source. Analytical HPLC was
2H), 7.40 (t, J = 7.5 Hz, 2H), 7.35–7.28 (m, 4H), 7.19 (d, J = 7.5 Hz, 1H), 6.95–6.92
(m, 2H), 6.86 (s, 1H), 5.15 (s, 2H), 2.19 (s, 3H), 2.18 (s, 3H). 13C NMR (DMSO-d6):
d 158.7, 140.9, 137.5, 137.1, 137.0, 130.9, 129.7, 128.4, 127.8, 127.7, 127.4,
127.1, 120.7, 118.6, 114.5, 112.4, 111.1, 69.2, 20.2, 17.4. HRMS (ESI-TOF, m/z):
calcd for C22H23N2O ([M+H]+) 331.1800; found 331.1810.
(f). N-(2,4-Dimethylphenyl)-2,2,2-trifluoro-N0-(3-benzyloxybenzylidene)acetohy-
razide (5). To a stirred solution of 4 (4.0 g, 12.1 mmol) and Et3N (2.02 mL,
14.5 mmol) in CH2Cl2 (30 mL) was added trifluoroacetic anhydride (2.02 mL,
14.5 mmol) dropwise at 0 °C under nitrogen atmosphere. The reaction mixture
was stirred at 0 °C for 1.5 h. After the mixture was concentrated, the residue
was purified by column chromatography with acetone/hexanes (from 1:10 to
1:7) to afford 5 (4.64 g, 90%) as a pale yellow solid; mp 112–113 °C. 1H NMR
(CDCl3): d 7.43 (d, J = 7.5 Hz, 2H), 7.38 (t, J = 7.5 Hz, 2H),7.34–7.31 (m, 2H),
7.28–7.23 (m, 3H), 7.19 (d, J = 8.0 Hz, 1H), 7.11 (d, J = 7.5 Hz, 1H), 7.04–7.00 (m,
2H), 5.09 (s, 2H), 2.41(s, 3H), 2.07 (s, 3H). 13C NMR (CDCl3): d 159.2, 144.0,
141.1, 136.8, 136.3, 134.8, 132.7, 129.9, 129.7, 128.9, 128.7, 128.6, 128.2, 127.7,
121.5, 118.2, 112.7, 70.1, 21.4, 17.1. HRMS (ESI-TOF, m/z): calcd for
performed using a Prodigy (Phenomenex) 5
mobile phase 3:1:1 CH3CN:MeOH:20 mM phosphate buffer solution
(pH = 6.7); flow rate 1.5 mL/min; and UV (254 nm) and -ray (PIN diode)
flow detectors. Semi-preparative HPLC was performed using Prodigy
(Phenomenex) 5
m C-18 column, 12 nm, 10 ꢁ 250 mm; mobile phase 3:1:1
CH3CN:MeOH:20 mM phosphate buffer solution (pH = 6.7); flow rate 5.0 mL/
min; UV (254 nm) and -ray (PIN diode) flow detectors. C18 Plus Sep-Pak
cartridges were obtained from Waters Corporation (Milford, MA). Sterile
lm C-18 column, 4.6 ꢁ 250 mm;
c
a
l
c
Millex-FG 0.2
(Bedford, MA).
lm filter units were obtained from Millipore Corporation
(b). 1-(2,4-Dimethylphenyl)-2-(3-methoxybenzylidene)hydrazine (1). To a stirred
suspension of 2,4-dimethylphenylhydrazine hydrochloride (951 mg,
5.51 mmol) and sodium acetate (452 mg, 5.51 mmol) in water (5 mL) was
added 3-methoxybenzaldehyde (500 mg, 3.67 mmol) in EtOH (3 mL). The
reaction mixture was heated to 100 °C and held at this temperature for 20 min
with vigorous stirring. The mixture was cooled to 0 °C, the orange sticky oil
accumulated at the bottom of the flask. The yellow solution was decanted and
washed with cold water. The sticky oil was stored in refrigerator. After the
sticky oil solidified, it was washed with hexanes and dried to afford 1 (800 mg,
86%) as a yellow solid, which was stored at ꢂ20 °C; mp 58–59 °C. 1H NMR
(DMSO-d6): d 9.48 (s, 1H), 8.08 (s, 1H), 7.32 (d, J = 8.0 Hz, 1H), 7.29 (d, J = 8.0 Hz,
1H), 7.20–7.19 (m, 2H), 6.92 (d, J = 8.0 Hz, 1H), 6.88–6.86 (m, 2H), 3.80 (s, 3H),
2.19 (s, 6H).
C
24H22N2O2F3 ([M+H]+) 427.1633; found 427.1654.
(g). N-(2,4-Dimethylphenyl)-2,2,2-trifluoro-N0-(3-hydroxybenzylidene)acetohy-
razide (desmethyl-J147, 6). To a stirred solution of 5 (200 mg, 0.47 mmol) in
Me2S (3 mL) and CH2Cl2 (3 mL) was added BF3ꢀEt2O dropwise at room
temperature. The reaction mixture was stirred at room temperature for 4 h.
The mixture was poured into ice-water and extracted with EtOAc. The
combined layer was washed with brine, dried over anhydrous Na2SO4,
filtered and concentrated in vacuo. The residue was purified by column
chromatography with acetone/hexanes (from 1:7 to 1:4) to afford 6 (140 mg,
89%) as a white solid; mp 148–149 °C. 1H NMR (CDCl3): d 7.23–7.15 (m, 5H),
7.07 (d, J = 7.5 Hz, 1H), 7.03 (d, J = 8.0 Hz, 1H), 6.84 (ddd, J = 8.0, 2.5, 1.0 Hz, 1H),
5.45 (s, 1H), 2.39 (s, 3H), 2.07 (s, 3H). 13C NMR (CDCl3): d 156.2, 144.3, 141.2,
136.3, 134.8, 132.7, 130.1, 129.5, 128.9, 128.6, 121.2, 118.2, 113.7, 21.4, 17.1.
HRMS (ESI-TOF, m/z): calcd for C17H15N2O2NaF3 ([M+Na]+) 359.0988; found
359.0983.
(c). N-(2,4-Dimethylphenyl)-2,2,2-trifluoro-N0-(3-methoxybenzylidene)acetohy-
razide (J147, 2). To a stirred solution of 1 (500 mg, 1.97 mmol) and Et3N
(0.33 mL, 2.36 mmol) in CH2Cl2 (5 mL) was added trifluoroacetic anhydride
(0.33 mL, 2.36 mmol) dropwise at 0 °C under nitrogen atmosphere. The
reaction mixture was stirred at 0 °C for 1.5 h. After the mixture was
concentrated, the residue was purified by column chromatography with
acetone/hexanes (1:10) to afford compound 2 (571 mg, 83%) as a pale yellow
oil. 1H NMR (CDCl3): d 7.26–7.23 (m, 4H), 7.19 (d, J = 8.0 Hz, 1H), 7.12 (d,
J = 7.5 Hz, 1H), 7.03 (d, J = 8.0 Hz, 1H), 6.92 (dd, J = 8.5, 2.0 Hz, 1H), 3.79 (s, 3H),
2.39 (s, 3H), 2.08 (s, 3H). HRMS (ESI-TOF, m/z): calcd for C18H18N2O2F3 ([M+H]+)
351.1320; found 351.1311.
(d). 3-(Benzyloxy)benzaldehyde (3). A suspension of 3-hydroxybenzaldehyde
(2.0 g, 16.4 mmol), K2CO3 (3.39 g, 24.6 mmol) and KI (0.07 g) in DMF (10 mL)
was stirred and heated to 65 °C under nitrogen atmosphere. Benzyl bromide
(2.53 mL, 21.3 mmol) was added dropwise. After the reaction mixture was
stirred at 65 °C overnight, the mixture was cooled to room temperature. Water
was added and the mixture was extracted with Et2O. The combined organic
layer was washed with brine, dried over anhydrous Na2SO4, filtered and
concentrated in vacuo. The residue was triturated with cooled hexanes to give
3 (3.02 g, 87%) as a white solid; mp 42–43 °C. 1H NMR (CDCl3): d 9.97 (s, 1H),
7.48–7.43 (m, 5H), 7.41–7.38 (m, 2H), 7.35–7.32 (m, 1H), 7.26–7.24 (m, 1H),
5.12 (s, 2H).
(h). N-(2,4-Dimethylphenyl)-2,2,2-trifluoro-N0-(3-[11C]methoxybenzylidene)acet-
ohyrazide ([11C]J147,
[ [ a)
11C]2). 11C]CO2 was produced by the 14N(p, 11C
nuclear reaction in the small volume (9.5 cm3) aluminum gas target
provided with the Siemens RDS-111 Eclipse cyclotron. The target gas
consisted of 1% oxygen in nitrogen purchased as a specialty gas from Praxair,
Indianapolis, IN. Typical irradiations used for the development were 55 lA
beam current and 15 min on target. The production run produced
approximately 28.5 GBq of [11C]CO2 at EOB. In a small reaction vial (5 mL),
the precursor desmethyl-J147 (6) (0.3–0.5 mg) was dissolved in CH3CN
(300 lL). To this solution was added NaH (1 mg). No carrier-added (high
specific activity) [11C]CH3OTf that was produced by the gas-phase production
method15 from [11C]CO2 through [11C]CH4 and [11C]CH3Br with silver triflate
(AgOTf) column was passed into the reaction vial at RT, until radioactivity
reached a maximum (ꢃ2 min), and then the reaction vial was isolated and
heated at 80 °C for 3 min. The contents of the reaction vial were diluted with
NaHCO3 (0.1 M, 1 mL), and injected onto the semi-preparative HPLC column
with 3 mL injection loop for purification. The product fraction was collected in
a recovery vial containing 30 mL water. The diluted tracer solution was then
passed through
a C-18 Sep-Pak Plus cartridge, and washed with water
(e). 1-(3-(Benzyloxy)benzylidene)-2-(2,4-dimethylphenyl)hydrazine (4). To
stirred suspension of 2,4-dimethylphenylhydrazine hydrochloride (2.68 g,
15.54 mmol) and sodium acetate (1.27 g, 15.54 mmol) in water (20 mL) was
a
(5 mL ꢁ 4). The cartridge was eluted with EtOH (1 mL ꢁ 2), followed by
10 mL saline, to release [11C]2. The eluted product was then sterile-filtered
through a Millex-FG 0.2 lm membrane into a sterile vial. Total radioactivity
added
3
(3.0 g, 14.1 mmol) portionwise, followed by EtOH (10 mL). The
was assayed and total volume was noted for tracer dose dispensing. Retention
reaction mixture was heated to 75 °C and held at this temperature for
10 min with vigorous stirring until yellow solid precipitated. The mixture was
cooled to 0 °C and filtered. The solid was washed with cold water, hexanes and
dried to afford 4 (4.25 g, 91%) as a yellow solid, which was stored at ꢂ20 °C; mp
70–71 °C. 1H NMR (DMSO-d6): d 9.48 (s, 1H), 8.05 (s, 1H), 7.48 (d, J = 7.5 Hz,
times in the semi-preparative HPLC system were: tR 6 = 6.67 min, tR
2 = 12.48 min, tR
system were: tR 6 = 4.11 min, tR 2 = 8.57 min, tR
corrected radiochemical yield of [11C]2 from [11C]CO2 was 35–50%.
[
11C]2 = 12.48 min. Retention times in the analytical HPLC
[
11C]2 = 8.57 min. The decay