Synthesis of the carbon-14 labeled isotopomers of (R)-N-methyl-3-[2- methylphenoxyl]-benzenepropanamine hydrochloride (atomoxetine hydrochloride, LY139603), and two of its metabolites

Article abstract of DOI:10.1002/jlcr.849

Carbon-14 labeled Straterra (Atomoxetine HC1, LY139603, (-)-N-methyl-3-(2-methylphenoxy)-benzenepropanamine hydrochloride), a potent inhibitor of the presynaptic norepinephrine transporter, and two of its major metabolites were synthesized. The key compon

Full text of DOI:10.1002/jlcr.849

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS
J Label Compd Radiopharm 2004; 47: 615–625.
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jlcr.849
Research Article
Synthesis of the carbon-14 labeled isotopomers of (R)-
N-methyl-3-[2-methylphenoxyl]-benzenepropanamine
hydrochloride (atomoxetine hydrochloride, LY139603),
and two of its metabolitesy
Fengjiun Kuo*, Dean K. Clodfelter and William J. Wheeler
Lilly Research Laboratories, A Division of Eli Lilly and Company, Lilly Corporate
Center, Indianapolis, IN 46285, USA
Summary
Carbon-14 labeled StraterraTM (Atomoxetine HCl, LY139603, (-)-N-methyl-3-(2-
methylphenoxy)-benzenepropanamine hydrochloride), a potent inhibitor of the
presynaptic norepinephrine transporter, and two of its major metabolites were
synthesized. The key component, S-(+)-3-chloro-l-phenyl-l-propanol-[1-14C] was
synthesized by Stille coupling of benzoyl chloride-[carbonyl-14C] with vinyl tri-n-
butylstannane, followed by HCl addition to the vinyl ketone, and asymmetric
reduction of the ketone by Corey’s CBS reagent. Mitsunobu reaction of this S-(+)-3-
chloro-l-phenyl-l-propanol-[1-14C] with various phenol derivatives, followed by
converting the chloride to amines, gave desired products. Copyright # 2004 John
Wiley & Sons, Ltd.
Key Words: S-(+)-3-chloro-1-phenyl-1-propanol-[1-14C]; LY139603-[14C]; Straterra
Introduction
StraterraTM (Atomoxetine HCl, LY139603, (-)-N-methyl-3-(2-methylphe-
noxy)-benzenepropanamine hydrochloride) is a potent inhibitor of the
presynaptic norepinephrine transporter. Atomoxetine has been approved for
use as a therapeutic agent for the treatment of attention-deficit/hyperactivity
disorder (ADHD) in children, adolescents, and adults. The metabolism and
disposition of atomoxetine has been extensively examined in a number of
*Correspondence to: F. Kuo, Eli Lilly and Company, Lilly Corporate Center, DC1543, Indianapolis, IN
46285, USA. E-mail: kuo fengjiun@lilly.com
yA Poster was Presented at the 8th International Isotope Society Symposium on the Synthesis and Use of
Isotopes and Isotopically Labeled Compounds, Boston, MA, 1–5 June, 2003.
Copyright # 2004 John Wiley & Sons, Ltd.
Received 15 March 2004
Revised 21 April 2004
Accepted 30 April 2004

616
F. KUO ET AL.
animal species as well as man using its 14C-labeled isotopomer.1,2 The
biotransformation of atomoxetine was similar in the rat and dog, undergoing
aromatic ring-hydroxylation, benzylic oxidation (rat only), and N-demethyla-
tion. The primary oxidative metabolite of atomoxetine was 40-hydroxyato-
moxetine (3), which was subsequently conjugated forming O-glucuronide and
O-sulfate (dog only) metabolites. Smaller amounts of N-des-methylatomox-
etine (4) were also detected. The 14C-isotopomers of 3 and 4 were also
prepared for use in the determination of their protein binding. In this paper,
we discuss the preparation of these compounds.
Discussion
In 1995, Wheeler and Kuo reported on the synthesis of 14C-labeled
duloxetine.3 In that report, the Stille protocol4 was used to prepare 1-(2-
thienyl)-2-propen-l-one by the reaction of the acyl chloride of thiophene-2-
carboxylic acid with vinyl-tri-n-butylstannane/DMPU in the presence of
catalytic benzylchloro-bis-triphenyl-phosphine-palladium(II). Addition of
HCl/Et2O, followed by reduction with BH3 THF/S-2-methyl-CBS-oxazabor-
olidine yielded R-(+)-3-chloro-1(2-thienyl)-l-propanol. This chloroalcohol
represented a reasonable substrate for the Mitsunobu reaction with 1-
naphthol. The model chemistry using the commercially available R-(+)-3-
chloro-1-phenyl-1-propanol and 1-naphthol in the presence of diethyl
azodicarboxylate/Ph3P worked even better and provided the basis for much
of the chemistry presented in this paper.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

SYNTHESIS OF THE CARBON-14 LABELED ISOTOPOMERS
617
In the synthesis of atomoxetine, benzoyl-[carbonyl-14C] chloride was reacted
as described above with vinyl-tri-n-butylstannane/DMPU in the presence
of catalytic benzylchloro-bis-triphenylphosphinepalladium-(II)4 to yield
1-phenyl-2-propen-l-one-[1-14C]. Addition of HCl/Et2O, followed by
reduction with BH3THF/R-2-methyl-CBS-oxazaborolidine5 (1), yielded
S-(+)-3-chloro-l-phenyl-l-propanol-[1-14C] 2 in 46% yield (from benzoic-
[carbonyl-14C] acid). Reaction of 2 with 2-cresol/THF in the presence of di-iso-
propyl azodicarboxylate/Ph3P yielded R-3-chloro-1-phenyl-1-(2-methylphe-
noxy)-propane-[1-14C] (5) in 52% yield after chromatography. Activation of 5
(by reaction with NaI/acetone) followed by reaction of the iodide (6) with
methylamine/THF and salt formation yielded atomoxetine-[14C] HCl
(LY139693-[14C], 82% yield from 5). Treatment of 5 with NaN3/DMF
(94%), followed by reduction of the corresponding azide (7) with NaBH4/i-
PrOH and salt formation by reaction with HCl/CH3OH yielded 4-[14C] (24%
yield for the last two steps).
It was envisioned that 40-hydroxyatomoxetine (3) could be prepared by
using the same strategy as was used for the preparation of atomoxetine
(reaction of S-3-chloro-l-phenyl-1-propanol (2) with an appropriately
protected 2-methylhydroquinone). The key was to regioselectively protect
the 4-hydroxyl in 2-methylhydro-quinone. McGill found that when
2-methylhydroquinone was reacted with t-BOC2O and DMAP in THF,
the desired carbonate 8 was obtained in 76% yield.6 Reaction of 8 with
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

618
F. KUO ET AL.
S-3-chloro-1-phenyl-1-propanol-[1-14C] (2-[14C]) in the presence of ADDP/n-
Bu3P/THF yield 9. Reaction of 9 with NaI/acetone yielded 10(64%).
Reaction of 10 with CH3NH2/THF followed by salt formation with oxalic
acid/CH3OH yielded 3-[14C] oxalate (72% for the last two steps). The
analytical results for LY136903-[14C] and its metabolites (4-[14C] HCl and
3-[14C] oxalate are shown in Table 1.
Conclusions
A general and simple method has been developed for the synthesis of a carbon-
14 labeled LY139603, a potent inhibitor of the presynaptic norepinephrine
transporter, and its metabolites. The key component, S-(+)-3-chloro-l-
phenyl-1-propanol-[1-14C] 2-[14C] was synthesized by Stille coupling of
benzoyl chloride-[carbonyl-14C], followed by HCl addition to the olefin and
asymmetric ketone reduction by Corey’s CBS reagent. Mitsunobu reaction of
S-(+)-alcohol-[14C] with various phenols derivatives, followed by amination
of the halides gave the desired products.
Experimental
Benzoic acid-[14C] acid was purchased from ChemSyn Laboratories. NMR
spectra were obtained on a General Electric QE-300 nuclear magnetic
resonance spectrometer at 300 MHz. Chemical shifts are reported in parts
per million (ppm) downfield from tetramethylsilane. Direct chemical ioniza-
tion mass spectra (DCI-MS) and electron impact mass spectra (EI-MS) were
recorded on a Nermag R30-10 triple stage quadrapole mass spectrometer.
Flash chromatography was performed as described by Still et al.7 using E.M.
Science silica gel 60 (230–400 mesh). Unless otherwise noted, the organic
extracts were dried over anhydrous sodium sulfate. Radiochemical purity
(RCP) was assessed by autoradiography employing E. Merck silica gel F-254
TLC plates and Kodak BB-5 X-ray film. The radioactive lane was divided,
Table 1. Analytical results
LY136903-[14C]
4-[14C] HCl
3-[14C] Ox.
Specific activity in mCi/mg
Radiochemical purity (%)
Optical purity (%S)c
Identity
66.3
99.9a, 100b
0.2
Co-elutes with
standard
256
66.7
99.0b
55.8
99.0b
Co-elutes with
standard
Co-elutes with
standard
ES-MS: [M+H]+, m/z
a TLC (silica gel): CH2Cl2/CH3OH/NH4OH (100:10:1), rf=0.37.
b HPLC: Altima Phenyl (4.6 ꢀ 250 mm), gradient elution at 1 ml/min. (30% B for 20 min. increasing to
70% B over 10 min. and holding at 70% B for 5 min.) with radiochemical detection (Solvent A=pH 2.0
DEA, Solvent B=CH3CN).
c Chiral HPLC: Chiralcel OD-H eluting with IPA/hexanes (85:15) with 0.2% DEA at 1 ml/min, UV
detection at 271 nm.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

SYNTHESIS OF THE CARBON-14 LABELED ISOTOPOMERS
619
suspended in methanol, and after sonication, the mixture was diluted with
AquassureTM scintillation cocktail (DuPont NEN) and counted. As a further
check of the radiochemical purity, the sample was subjected to radio-HPLC;
30 s samples of the eluent were collected, diluted with AquassureTM and
counted.
Synthesis of (S)-(-)-3-chloro-1-phenyl-1-propanol-[1-14C], 2-[14C]
Benzoic acid-[carboxyl-14C] (70 mCi, 55.3 mCi/mmol) and benzoic acid (310 mg,
2.54 mmol) were suspended in 15 ml of toluene and treated with 1 ml of oxalyl
chloride and three drops of dimethylformamide. The solution was stirred at
room temperature over the weekend (about 70 h). The solution was
concentrated; to the residue was added 10 ml of toluene, and the solution was
concentrated again. The concentrating step was repeated three times to remove
oxalyl chloride completely. The final residue was dissolved in 4 ml of toluene and
treated with 1.14 ml of tributyl(vinyl)tin and 50mg of tetra-kis-(triphenylpho-
sphine)palladium(0) and heated for 4 h at 408C in an oil bath. TLC (SiO2,10:1
hexanes/ether) indicated the complete consumption of starting material.
The solution was concentrated and the residue was dissolved in 6 ml of
ether, added to an ether/HCl solution (20 ml, bubbled with anhydrous HCl for
2 min), stirred at 08C for 30 min and then at room temperature for 1 h. After
storing in the refrigerator overnight, the solution was concentrated and the
residue was dried in vacuo for 30 min to give crude chloroketone. A mixture of
crude ketone (in 10 ml of THF) and (R)-2-methyl-CBS-oxazaborolidine
(2.5 ml ꢀ 1 M in toluene) was concentrated in vacuo and redissolved in 10 ml
of THF. The solution was cooled in an ice bath under argon, treated dropwise
with borane-THF complex (3.8 ml ꢀ 1 M in THF) over a period of 50 min, and
stirred for another hour thereafter. The excess of borane was destroyed by the
dropwise addition of methanol (10 ml) and the resulting solution was
concentrated in vacuo. The crude product was purified by flash column
chromatography (SiO2, 4:1 hexanes/ether, twice) to give the desired product
2-[14C] as a white solid (297 mg, 1.75 mmol, 46% from benzoic acid). It was co-
eluted with a non-labeled reference on TLC (SiO2, 4:1=hexanes/Et2O).
Proton NMR of non-labeled product: (in CDCl3, ppm) 7.40 (m, 5 H), 5.0 (m,
1 H), 3.8 (m, 1 H), 3.6 (m, 1 H), 2.3 (m, 1 H), 2.1 (m, 1 H), 2.0 (br. S, 1 H).
Synthesis of (R)-3-chloro-1-phenyl-1-[2-methylphenoxy]-propane-[1-14C],
5-[14C]
To a THF solution (18 ml) of 2-[14C] (279 mg, 1.75 mmol) was added 2-
methylphenol (o-cresol) (239 mg, 2.21 mmol), triphenylphosphine (599 mg,
2.29 mmol) and chilled in an ice bath under argon, Di-iso-propyl azodicarbox-
ylate (DIAD, 0.4 ml, 2.0 mmol) was added dropwise over 45 min. The solution
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

620
F. KUO ET AL.
was stirred in the ice bath for another hour then at room temperature
overnight. The solution was concentrated in vacuo and the residue was stirred
in 100 ml of 5% EtOAc in hexanes for 90 min. The white precipitate was
filtered and rinsed with 5% EtOAc in hexanes. The combined filtrates were
concentrated and the residue was purified by chromatography (SiO2, hexanes).
The desired fractions were pooled and concentrated, and the residue was
further dried in vacuo to give the product 5-[14C] (236 mg, 0.91 mmol, 51.9%)
as a colorless viscous oil. It was co-eluted with a non-labeled reference on TLC
(SiO2, hexanes). Proton-NMR of non-labeled product: (CDCl3, ppm) 7.4 (m,
5 H), 7.15 (d, 1 H), 7.0 (t, 1 H), 6.85 (t, 1 H), 6.65 (d, 1 H), 5.42 (m, 1 H), 3.85
(m, 1 H), 3.65 (m, 1 H), 2.55 (m, 1 H), 2.3 (M, 1 H), 2.35 (s, 3 H).
Synthesis of (R)-N-methyl-3-[2-methylphenoxy]-benzenepropanamine-[3-14C]-
hydrochloride, LY139603-[14C]
A solution of chloride 5 (236 mg, 0.91 mmol) in 50 ml of acetone was refluxed
with 5 g of NaI over the weekend (about 68 h). The solution was concentrated
and the residue, as a light yellow solid, was dissolved in 20 ml of water and
20 ml of hexanes. The organic layer was separated, washed with water
(25 ml ꢀ 3), and concentrated to give a colorless oil. HPLC (Zorbax ODS,
3 ꢀ 250 mm, 30:70 H2O/CH3CN, 0.8 ml/min, UV at 220 nm) indicated less
than 0.5% of chloride 5 remained. The colorless oil was dissolved in 15 ml of
THF and stirred with 5 ml of 40% aqueous CH3NH2 at room temperature
overnight (about 20 h). TLC indicated that iodide was consumed. The solution
was concentrated, the aqueous residue was added to 25 ml of EtOAc, and the
solution was washed with water. Removal of solvent and chromatography
(SiO2, 100:10:1 CH2Cl2/MeOH/NH4OH) gave the product (free base of
LY139603-[14C], co-eluted with non-labeled reference) as a colorless viscous oil
(222 mg, 0.87 mmol). Proton-NMR of non-labeled product (CDCl3, ppm) 7.35
(m, 5 H), 7.15 (d, 1 H), 7.0 (t, 1 H), 6.82 (t, 1 H), 6.65 (d, 1 H), 5.35 (m, 1 H),
2.6–3.2 (m, 2 H), 2.45 (s, 3 H), 2.37 (s, 3 H), 2.3–2.5 (m, 2 H). This free base was
dissolved in 30 ml of CH2Cl2, to which a solution of 0.5 ml of 12 N HCl in 2 ml
of MeOH was added with stirring, and the solution was then concentrated.
The residue was added to 20 ml of anhydrous EtOH and concentrated again to
remove the residual water. The residue was dissolved in 2 ml of anhydrous
EtOH, diluted with 20 ml of ether, and stirred at room temperature for 30 min.
The white precipitate was filtered off, washed with ether, and dried in vacuo to
give the final product LY139603-[14C] as a white hydrochloride salt (217 mg,
0.74 mmol, 82% from chloride 5). Radiochemical purity: 99% by radio-HPLC
and TLC. Specific activity=60.94 mCi/mg, The white salt was mixed with
400 mg of LY139603, dissolved in CH2Cl2, and concentrated to give a white
salt. Recrystalization from EtOH and ether gave the product LY139603-[14C]
as a white crystalline solid (502 mg, 1.72 mmol). MS: M+H=256/258.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

SYNTHESIS OF THE CARBON-14 LABELED ISOTOPOMERS
621
Radiochemical purity: 99% by radio-HPLC. Chirality: 99% e.e. by chiral
HPLC. Specific activity: 22.43 mCi/mg. Proton NMR of a non-labeled product
(CDCl3, ppm) 7.35 (m, 5 H), 7.15 (d, 1 H), 7.0 (t, 1 H), 6.83(t, 1 H), 6.62 (d,
1 H), 5.0 (dd, 1 H), 3.2 (m, 2 H), 2.2–2.6 (m, 5 H), 2.14 (s, 3 H).
Radio-HPLC conditions: Alltech, Alltima phenyl column, 4.6 ꢀ 250 mm.
Mobile phase: 30:70 CH3CN/buffer (1% Et2NH in water, adjusted to pH 2.03
with conc. H2SO4).
Flow rate: 1 ml/min at 408C. UV: at 220 nm.
Chiral-HPLC conditions: Chiralcel OD-H, 4.6 ꢀ 250 mm. Mobile phase:
15:85 isopropanol/hexanes with 0.2% diethylamine. Flow rate: 1 ml/min at
room temperature UV at 271 nm.
Synthesis of (R)-3-chloro-1-phenyl-1[2-methyl-4-(tert.-butyloxycarbonyl)-oxy]
propane-[1-14C] (9)
A stirred toluene (3 ml) solution of (S)-(-)-3-chloro-1-phenyl-1-propanol-
[1-14C] (2, 0.083 g, 0.488 mmol), 2-methyl-4-[(tert.-butyloxycarbonyl)oxy]phe-
nol (8, 0.164 g, 0.732 mmol), and tri-n-butylphosphine (0.188 ml, 0.732 mmol)
was chilled in an ice bath (under argon) and treated with 1,1-(azodicarbonyl)-
dipiperidine (ADDP, 0.185 g, 0.732 mmol). Stirring in the cold was continued
for 1 h; the ice bath was removed and stirring was continued overnight. The
mixture was filtered and the filtrate was concentrated in vacuo. The residue was
purified by flash chromatography on silica gel (30 ꢀ 150 mm) eluting
with 10 ml fractions of toluene. Fractions 6–10 (co-eluted with authentic
material) were combined and concentrated in vacuo to yield (R)-3-chloro-1-
phenyl-1-[2-methyl-4-(tert.-butyloxycarbonyl)-oxy]propane-[1-14C] (9, 0.139 g,
76% yield).
Synthesis of (R)-3-iodo-1-phenyl-1[2-methyl-4-(tert.-butyloxycarbonyl)-oxy]-
propane-[1-14C] (10)
A mixture of (R)-3-chloro-1-phenyl-1[2-methyl-4-(tert.-butyloxycarbonyl)-
oxy]propane-[1-14C] (9, 0.139 g, 0.370 mmol) and sodium iodide (0.555 g,
3.70 mmol) was dissolved in 2-propanone (MEK, 25 ml) and stirred at reflux
(under argon) overnight. The reaction mixture was allowed to cool to room
temperature and poured into ether. A white precipitate was formed which was
removed by filtration. The filtrate was concentrated in vacuo. The residue was
re-dissolved in ether and filtered. The filtrate was purified by flash
chromatography on silica gel (40 ꢀ 150 mm) eluting with 10 ml fractions of
pentane/EtOAc (98:2). Fractions 6–7 were combined and concentrated
in vacuo to yield (R)-3-iodo-1-phenyl-1[2-methyl-4-(tert.-butyloxycarbonyl)-oxy]
propane-[1-14C] (10, 0.111g, 64% yield): ES-MS; [M+NH+4 ]+ m/z=
486/488.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

622
F. KUO ET AL.
Synthesis of g-(R)-N-methyl(2-methyl-4-hydroxyphenoxy)benzene-propana-
mine-[3-14C] oxalate salt, (3-[14C]) oxalate salt
A mixture of (R)-3-iodo-l-phenyl-1[2-methyl-4-(tert.-butyloxycarbonyl)-oxy]-
propane-[1-14C] (10, 0.111 g, 0.237 mmol) and methylamine (2 N in THF,
1.66 ml, 3.32 mmol) in THF (10 ml) was stirred at room temperature (under
argon) overnight. After ca. 18 h, TLC (silica gel, pentane/EtOAc, 80:20)
showed that 73% of the material remained at the origin while 24% co-eluted
with starting material. Another 15 eq. of methylamine was added and stirring
was continued. After an additional 24 h, the mixture was concentrated in
vacuo. The residue was purified by flash chromatography on silica gel
(30 ꢀ 150 mm) eluting with 10-ml fractions of CH2Cl2/CH3OH/NH4OH
(100:10:1). Fractions 12–20 were combined and concentrated in vacuo to
yield g-(R)-N-methyl(2-methyl-4-hydroxyphenoxy)benzenepropanamine-[3-14C]
(3-[14C], 0.046 g, 72%).
An EtOAc (3 ml) solution of g-(R)-N-methyl(2-methyl-4-hydroxyphenoxy)
benzene-propanamine-[3-14C] (0.046 g, 0.169 mmol) was stirred and treated
with oxalic acid (0.015 g, 0.167 mmol) in CH3OH (0.5 ml). A white crystalline
solid formed which was collected by filtration, washed with EtOAc (2 ꢀ 15 ml),
Et2O (15 ml) and dried in vacuo to yield g-(R)-N-methyl(2-methyl-4-
hydroxyphenoxy)benzenepropanamine-[3-14C] oxalate (3-[14C] oxalate, 0.02 g,
47.5% yield).
1
Physical data for the non-labeled product: H-NMR: (DMSO/d6 + D2O)
d 1.98 (1H, m, CH2CH), 2.08 (3H, s, aromatic CH3), 2.09 (1H, m,
CH2CH), 2.46 (1H, s, NCH3), 2.91 (2H, m, CH2N), 5.19 (1H, m, CH),
6.27 (1H, dd, 60-H), 6.43 (1H, m, 50-H), 7.19 (1H, m, 30-H), 7.28 (5H, s,
aromatic); Anal. Calc’d for C19H23NO6: C, 63.15; H, 6.41; N, 3.88. Found: C,
63.32; H, 6.59; N, 3.99; HPLC on a Zorbax Eclipse XDB-C18 column
(4.6 ꢀ 150 mm) eluting with 0.05 M NH4OAc/acetonitrile (80:20) at 10 ml/min
(column temperature 308C) showed a single peak at RT 8.57 min (20 ml of a
1 mg/ml sample dissolved in 0.05 M NH4OAc was injected). UV detection at
210 nm was used.
Synthesis of (R)-3-azido-1-phenyl-1(2-methylphenoxy)propane-[1-14C](7-[14C])
An aqueous (1 ml) solution of sodium azide (0.094 g, 1.45 mmol) was
added at room temperature to a DMF (4 ml) solution of (R)-3-chloro-1-
phenyl-1(2-methylphenoxy)-propane-[1-14C] (5-[14C], 7.2 mCi, 20 mCi/mmol,
0.36 mmol) under argon. The mixture was stirred at 85–908C overnight.
The DMF was removed in vacuo and the residue was partitioned between
water and EtOAc. The aqueous layer was washed with EtOAc; the combined
EtOAc extracts were washed with saturated aqueous NaCl solution, dried
(anhydrous MgSO4), and concentrated in vacuo to yield (R)-3-azido-l-
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

SYNTHESIS OF THE CARBON-14 LABELED ISOTOPOMERS
623
phenyl-1(2-methylphenoxy)-propane-[1-14C] (7-[14C], 0.090 g, 94% yield).
TLC (silica gel, pentane/EtOAc 98:2) showed a new spot running slightly
ahead of 5-[14C].
A subsequent preparation of 7-[14C] from 5-[14C] (0.028 g, 0.107 mmol)
yielded an additional 0.023 g of material.
Synthesis of g-(R)-(2-methylphenoxy)benzenepropanamine-[3-14C] (4-[14C])
method A
A
mixture of (R)-3-azido-l-phenyl-1(2-methylphenoxy)-propane-[1-14C]
(7-[14C], 0.090 g, 0.337 mmol) and triphenylphosphine (0.177 g, 0.674 mmol)
in THF/water (15 ml/2 ml) was stirred at 50–558C under argon for 16 h. An
aliquot was worked up (see below); TLC (silica gel, pentane/EtOAc 98:2)
showed loss of starting material (except for a small amount of 2 remaining
from the previous reaction). TLC (silica gel, CH2Cl2/CH3OH/NH4OH
100:10:1) showed the formation of the desired product (7-[14C]) as well as
contamination by 5-[14C], unreacted iminophosphorane, and what is
presumably an adduct of 5-[14C] and Ph3P). The entire reaction mixture was
diluted with water (10 ml) and stirred for 0.5 h. The resulting mixture was
extracted with EtOAc (50 ml). Solid NaCl was added to clear the emulsion and
the aqueous layer was re-extracted with EtOAc (50 ml). The combined EtOAc
extracts were washed with saturated brine, dried (anhydrous Na2SO4), and
concentrated in vacuo. The residue was re-dissolved in EtOAc and extracted
with HC1 (1 N). The aqueous layer was re-washed with EtOAc and then made
basic with conc. NH4OH. This solution was extracted with EtOAc (3 ꢀ 15 ml).
This material was saved for later purification with the material from method B
(see below).
The EtOAc extracts from the acidic solution were concentrated and re-
dissolved in CH3OH (2 ml) and treated with NH4OH. This solution was
concentrated in vacuo and the residue was purified by flash chromatography
on silica gel (40 ꢀ 140 mm) eluting with 10-ml fractions of CH2Cl2/CH3OH/
NH4OH (100:10:1). Fractions 9–10 were combined and concentrated in vacuo
to yield g-(R)-(2-methylphenoxy)benzene-propanamine-[3-14C] (4-[14C],
0.009 g). Fraction 8 was contaminated and was retained for later purification
with the material from method B (see below).
Synthesis of g-(R)-(2-methylphenoxy)benzenepropanamine-[3-14C] (4-[14C])
method B
An IPA (5 ml) solution of (R)-3-azido-1-phenyl-1(2-methylphenoxy)-propane-
[1-14C] (7-[14C], 0.023 g, 0.086 mmol) was treated with NaBH4 (0.023 g) and
stirred overnight at 80–908C. TLC (silica gel, CH2Cl2/CH3OH/ NH4OH, 100:
10:1) showed a mixture of 4-[14C] and 7-[14C]. An additional 0.023 g of NaBH4
was added and heating was continued for an additional 7 h. There was still
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

624
F. KUO ET AL.
unreacted 7-[14C] remaining, so the mixture was diluted with THF (5 ml) and
IPA (1 ml) and an additional 0.023 g of NaBH4 was added and heating was
continued overnight. TLC showed that the reaction was 75% complete. The
reaction was quenched with HCl (1 N ꢀ 1 ml); conc. NH4OH (3 ml) was added
and the mixture was extracted with EtOAc (25 ml). The EtOAc layer was
washed with saturated brine, dried (anhydrous MgSO4), and concentrated
in vacuo. The residue was mixed with the residual material as well as fraction 8
from method A and purified by flash chromatography on silica gel
(30 ꢀ 150 mm) eluting with 10-ml fractions of CH2Cl2/CH3OH/NH4OH
(100:10:1). Fraction 6 was concentrated in vacuo to yield g-(R)-(2-methylphe-
noxy)benzenepropanamine-[3-14C] (4-[14C], 0.019 g).
Synthesis of g-(R)-(2-methylphenoxy)benzenepropanamine-[3-14C] (4-[14C]
HC1)
A methanol (2 ml) solution of g-(R)-(2-methylphenoxy)benzenepropanamine-
[3-14C] (4-[14C], 0.009 g from method A and 0.019 g from method B) was
treated with HCl (5 N ꢀ 0.025 ml) and concentrated in vacuo to a white foam.
This material was triturated with EtOAc (3 ml) and stirred until the material
crystallized. The white material was collected by filtration, washed with EtOAc
(5 ml) and Et2O (5 ml) and dried in vacuo to yield g-(R)-(2-methylphenoxy)
benzenepropanamine-[3-14C] hydrochloride (4-[14C] HCl, 0.025 g).
Acknowledgements
The authors would like to thank the colleagues in the Radiochemistry Group for
support and also Mr J. Matthew Clements of Department of Drug Disposition
for his support on the Mass Spectral analysis of the final product LY139603-[14C].
References
1. Barbuch RJ, Conrad PC, Kuo F, Li Q, Mattiuz EL, Mullen JH, Ponsler GD,
Sauer JM, Shugert RL, Wheeler WJ, Wood PG. Disposition and metabolic fate of
Atomoxetine Hydrochloride: pharmacokinetics, metabolism and excretion of
Atomoxetine in the Fischer 344 rat and beagle dog. Drug Metab Dispos 2003; 31:
88–97.
2. Sauer JM, Ponsler GD, Mattiuz EL, Lond AJ, Witcher JW, Thomasson HR,
DeSante KA. Disposition and metabolic fate of Atomoxetine HCl: the role of
CYP2D6 in human disposition and metabolism. Drug Metab Dispos 2003; 31:
98–107.
3. Wheeler WJ, Kuo F. An asymmetric synthesis of duloxetine hydrochloride, a
mixed uptake inhibitor of serotonin and norepinephrine, and its C-14 labeled
isotopomers. J Label Compd Radiopharm 1995; 36: 213–223.
4. Milstein D, Stille J. A mild, selective, general method of Ketone synthesis from
acid chlorides and organotin compounds catalysed by Palladium. J Org Chem
1979; 44: 1613–1618.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625

SYNTHESIS OF THE CARBON-14 LABELED ISOTOPOMERS
625
5. Corey EJ, Reichard GA. Tetrahedron Lett 1989; 30: 5207.
6. Dr John M McGill, personal communication, Lilly Research Laboratories, A
Division of Eli Lilly and Company, Indianapolis, IN 46285.
7. Still WC, Kahn M, Mitra A. J Org Chem 1978; 43: 2923.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 615–625