Convergent synthesis of two 14C-labeled β3- adrenergic receptor agonists

Article abstract of DOI:10.1002/jlcr.1086

The synthesis of β₃-adrenergic receptor agonists A and B with radiolabeled amide fragment, required for drug disposition studies, was accomplished based on initial formation of 2-(4-(2-amino-2-methylpropyl)phenoxy) -5-[¹⁴C]-cyanopyri

Full text of DOI:10.1002/jlcr.1086

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS
J Label Compd Radiopharm 2006; 49: 663–673.
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jlcr.1086
Research Article
14
Convergent synthesis of two C-labeled b3-adrenergic
receptor agonists
Boris A. Czeskis*, William J. Wheeler and Dean K. Clodfelter
Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
Summary
The synthesis of b3-adrenergic receptor agonists A and B with radiolabeled amide
fragment, required for drug disposition studies, was accomplished based on initial
formation of 2-(4-(2-amino-2-methylpropyl)phenoxy)-5-[14C]-cyanopyridine by the
reaction of 2-bromo-5-iodopyridine with para-substituted phenol, and following
cyanation of aromatic iodide with potassium cyanide-[14C]. After the coupling of the
resulted amine with glycidyl derivatives of 4-hydroxyindole and 4-hydroxycarbazole,
the corresponding nitriles were hydrolyzed with basic hydrogen peroxide to obtain
target amides A and B. Copyright # 2006 John Wiley & Sons, Ltd.
Received 27 April 2006; Revised 2 May 2006; Accepted 3 May 2006
Key Words: b3-adrenergic receptor agonists; carbon-14 labeled
Introduction
It is well known that b3-adrenergic receptor agonists potentially could be used
for the treatment of obesity and diabetes.1 Indole A2 and carbazole B3 belong
to this class of receptor agonists (Figure 1).
For the metabolism and disposition studies 14C-labeled materials were
required. Preliminary findings suggested that one of the main metabolic routes
leads to the cleavage of linear aliphatic parts of these molecules. Therefore,
each molecule had to be radiolabeled in two ‘side’ positions. The syntheses of
A with 14C-labeled indole fragment,4 and B containing 14C-labeled carbazole
fragment,5 have been published recently. In this communication we describe
the synthesis of both compounds with 14C-labeled carbamide moiety.
*Correspondence to: Boris A. Czeskis, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis,
IN 46285, USA. E-mail: czeskis@lilly.com
Copyright # 2006 John Wiley & Sons, Ltd.

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B. A. CZESKIS ET AL.
OH
H
O
HN
O
N
NH2
O
N
A
OH
H
O
HN
O
N
NH2
O
N
B
Figure 1.
Results and discussion
Retrosynthetic analysis of both molecules includes the coupling of corre-
sponding epoxides 1 and 2 with primary amine 3 (Scheme 1).
Our initial intention was the introduction of radiocarbon on a penultimate
step of the synthesis by cyanation of the iodide 8 (Scheme 2). For this purpose
2,5-diiodopyridine (4)6 was coupled with aminophenol 6 to form ether 7 in
59% yield. Exclusive regioselectivity in substitution at position 2 of pyridine
led us to attempt of replacement of diiodopyridine 4 by more stable 2-bromo-
5-iodopyridine (5)6. Not only was the regioselectivity retained, but also the
yield of the reaction was increased to 71%. Next step, the opening of epoxide 2
with amine 7, went smoothly to give the desired adduct 8. The attempts in the
cyanation of iodide 8 were not satisfactory. The heating of 8 with potassium
cyanide in the presence of copper (I) iodide in 1-methylpyrrolidinone (NMP)7
gave a low yield (less than 20%) of the cyanide 9 as a mixture with
1-methylpyrrolidinone. A similar result was obtained when copper (I) cyanide
alone8 was used for the same reaction.
The unsuccessful conversion of 8 into 9 may be attributed to the instability
of the substituted secondary alcohol fragment of the molecule under the high
temperature required for the reaction. It was necessary therefore to move the
cyanation to an earlier step of the synthesis. Indeed, the reaction of iodide 7
with potassium cyanide in the presence of copper (I) iodide in NMP proceeded
without complications, and provided cyanide 10 in high yield (Scheme 3). The
subsequent steps of coupling 10 with epoxides 1 and 2 leading to the
corresponding nitriles 11 and 9, and their hydrolysis with basic hydrogen
peroxide, went smoothly to give the target products, which were converted to
their salts A glycolate and B succinate.
The synthesis of radiolabeled compounds was accomplished using the same
approach (Scheme 3). The reaction of iodide 7 with potassium cyanide-[14C] in
Copyright # 2006 John Wiley & Sons, Ltd.
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DOI: 10.1002/jlcr

SYNTHESIS OF TWO 14C-LABELED b3-ADRENERGIC RECEPTOR AGONISTS
665
OH
O
H
HetO
N
NH2
O
N
A: Het = Indol-4-yl
B: Het = Carbazol-4-yl
O
H2N
X
+
HetO
O
N
1: Het = Indol-4-yl
2: Het = Carbazol-4-yl
3
Scheme 1.
AcO-
H3N+
H2N
I
I
K2CO3
DMF
+
O
N
OH
Y
N
7
4: Y = I
5: Y = Br
6
O
HN
O
OH
2
H
N
HN
O
R
i-PrOH
O
N
8: R = I
KCN
and/or
CuCN
9: R = CN
Scheme 2.
the presence of copper (I) iodide smoothly gave nitrile 10-[14C]. Condensation
of its amino group with epoxides 1 and 2 led to the corresponding adducts
11-[14C] and 9-[14C]. They were converted into the amides A-[14C] and B-[14C]
Copyright # 2006 John Wiley & Sons, Ltd.
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666
B. A. CZESKIS ET AL.
KnCN
CuCN
H2N
nCN
H2N
I
O
N
O
N
NMP
10, 10-[14C]
7
O
HetO
OH
1: Het = Indol-4-yl
2: Het = Carbazol-4-yl
H
N
HetO
nCN
O
N
i-PrOH
11, 11-[14C]: Het = Indol-4-yl
9, 9-[14C]: Het = Carbazol-4-yl
OH
H2O2,
K2CO3
H
N
HetO
nCONH2
O
N
A, A-[14C]: Het = Indol-4-yl
B, B-[14C]: Het = Carbazol-4-yl
HX
OH
H
nCONH2
HX
HetO
N
O
N
A, A-[14C] Glycolate: Het = Indol-4-yl, X = HOCH2COOH
B, B-[14C] Succinate: Het = Carbazol-4-yl, X = (CH2COOH)2
n = 12, 14
Scheme 3.
using hydrogen peroxide in the presence of potassium carbonate. On the final
step, the salts A-[14C] glycolate and B-[14C] succinate were formed. High total
chemical and radiochemical yields (more than 50%) from iodoamine 7 were
achieved for both target materials.
In conclusion, the cyanation of 2-aryloxy-5-iodopyridine 7 with potassium
cyanide-[14C] quantitatively provided 14C-labeled building block 10-[14C] that
was used for the efficient preparation of radiolabeled b3-adrenergic receptor
agonists A-[14C] and B-[14C].
Copyright # 2006 John Wiley & Sons, Ltd.
J Label Compd Radiopharm. 2006; 49: 663–673
DOI: 10.1002/jlcr

SYNTHESIS OF TWO 14C-LABELED b3-ADRENERGIC RECEPTOR AGONISTS
667
Experimental
The potassium cyanide-[14C]was purchased from American Radiolabeled
Chemicals, Inc. The NMR spectra were obtained in CDCl3 on a Varian
Mercury-400 at 400 (1H) and 100 (13C) MHz. Chemical shifts are reported in
parts per million (ppm) downfield from tetramethylsilane. Microanalytical,
IR, and UV data were provided by Physical Chemistry Department of Lilly
Research Laboratories. Flash column chromatography was performed using
silica gel 60 (230–400mesh) or Biotage Flash System. TLC was conducted on
precoated plates of silica gel 60 F254. HPLC was conducted on a Hitachi
instrument with UV detection at 230 nm at a flow rate of 1 ml/min; Conditions
A: column Zorbax RX-C8 (4.6 mm ꢀ 25 cm); mobile phase: aqueous 0.1%
trifluoroacetic acid/acetonitrile, 50:50; Conditions B: column Zorbax C8
(4.6 mm ꢀ 25 cm); mobile phase: aqueous 0.5% ammonium phosphate
monobasic/acetonitrile, 45:55. The radiochemical purity of A-[14C] glycolate
was determined by radio-HPLC: column: Zorbax SB-Phenyl (4.6 ꢀ 250 mm)
with gradient elution at 1.0 ml/min (Solvent A ¼ 70% of 0.1% ifluoroacetic
acid/30% of methanol, Solvent B ¼ 40% of 0.1% trifluoroacetic acid/60% of
methanol) from 0% B to 100% B over 30 min, and UV detection at 260 nm.
The radiochemical purity of B-[14C] succinate was determined by radio-HPLC:
column Zorbax SB-Phenyl (4.6 ꢀ 250 mm) with gradient elution at 1.0 ml/min
(Solvent A ¼ 50% of 0.1% trifluoroacetic acid/50% of methanol, Solvent B ¼
25% of 0.1% trifluoroacetic acid/75% of methanol) from 0% B to 100% B
over 32 min, and UV detection at 240 nm. All 14C-compounds were identified
by TLC and/or HPLC comparison with the corresponding non-radiolabeled
isotopomers.
6-(4-(2-Amino-2-methylpropyl)phenoxy)-3-iodopyridine, 7
To a solution of 2-bromo-5-iodopyridine (5)6 (1.89 g, 6.66 mmol) in
dimethylformamide (40 ml) were added 4-(2-amino-2-methylpropyl)phenol
acetate (6) (1.5 g, 6.66 mmol) and potassium carbonate (2.77 g, 20 mmol). The
reaction mixture was heated at 1408C (bath) for 16 h, and at 1558C (bath) for
4.5 h, then cooled to room temperature, diluted with ethyl acetate (40 ml), and
filtered. The filtrate was evaporated under vacuum. Biotage chromatography
of the residue (column 40M, eluting sequentially with 500 ml of dichlo-
methane/methanol, 90:10; 1000 ml of dichlomethane/methanol/ammonium
hydroxide, 90:10:1; and 200 ml of dichlomethane/methanol/ammonium
hydroxide, 85:15:1.5) gave 7 (1.75 g, 71%) as a pale solid. TLC: Rf ¼ 0:1
(dichlomethane/methanol, 90:10). HPLC (conditions A): Rt ¼ 4:0 min. NMR
(CDCl3, d, ppm): 1.15 (s, 6H), 2.68 (s, 2H), 6.74 (d, J ¼ 8:8 Hz, 1H), 7.05 (d,
J ¼ 8:3 Hz, 2H), 7.21 (d, J ¼ 8:3 Hz, 2H), 7.90 (dd, J ¼ 8:8 and 2.2 Hz, 1H),
8.36 (d, J ¼ 2:2 Hz, 1H). IR (KBr, n, cm-1): 605, 757, 820, 837, 856, 996, 1076,
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1138, 1166, 1203, 1239, 1273, 1360, 1457, 1505, 1573, 2852, 2911, 2960, 3431.
UV (EtOH, lmax, nm): 290, 274, 236. MS (ES+, m/z, %): 369 (11, M+1), 352
(100). Analysis calculated for C15H17IN2O: C, 48.92; H, 4.62; I, 34.46; N, 7.61,
found: C, 48.85; H, 4.69; I, 33.96; N, 7.64.
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-3-iodopyridine, 8
A mixture of epoxide 22,3,5 (53 mg, 0.22 mmol) and amine 8 (164 mg,
0.445 mmol) in 2-propanol (2.3 ml) was heated at 75–808C (bath) for 24 h,
and evaporated under vacuum. Biotage chromatography of the residue
(column 12M, eluting with dichlomethane/methanol, 95:5) gave 8 (120 mg,
90%) as a white solid. TLC: Rf ¼ 0:39 (dichlomethane/methanol, 95:5).
HPLC (conditions A): Rt ¼ 9:7 min. NMR (CDCl3, d, ppm): 1.12 (s, 3H), 1.14
(s, 3H), 2.70 (dAB, J ¼ 3:5 Hz, 1H), 2.73 (dAB, J ¼ 3:5 Hz, 1H), 2.99
(dd, J ¼ 11:9 and 7.3 Hz, 1H), 3.11 (dd, J ¼ 11:9 and 4.0 Hz, 1H), 4.14–4.26
(m, 2H), 4.32 (dd, J ¼ 9:2 and 4.8 Hz, 1H), 6.69 (d, J ¼ 7:9 Hz, 1H), 6.70
(d, J ¼ 8:3 Hz, 1H), 6.95 (d, J ¼ 8:3 Hz, 2H), 7.05 (d, J ¼ 7:9 Hz, 1H), 7.17
(d, J ¼ 8:3 Hz, 2H), 7.21 (t, J ¼ 7:9 Hz, 1H), 7.32 (t, J ¼ 8:3 Hz, 1H), 7.39
(m, 2H), 7.88 (dd, J ¼ 8:8 and 2.5 Hz, 1H), 8.08 (br. s, 1H), 8.28
(d, J ¼ 7:9 Hz, 1H), 8.34 (d, J ¼ 2:2 Hz. 1H). IR (KBr, n, cmꢁ1): 722, 753,
784, 828, 995, 1098, 1205, 1264, 1360, 1456, 1506, 1572, 1607, 2860, 2918,
2964, 3409. UV (EtOH, lmax, nm): 332, 319, 286, 242. HRMS (AP+):
calculated for C30H30IN3O3: 608.1410, found: 608.1379. Analysis for
C30H30IN3O3: C, 59.31; H, 4.98; I, 20.89; N, 6.92; found: C, 59.18; H, 5.01;
I, 20.87; N, 6.76.
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-3-cyanopyridine, 9 (from iodide 8 )
A mixture of iodide 8 (60 mg, 0.099 mmol), potassium cyanide (7 mg,
0.107 mmol), and copper (I) iodide (10 mg, 0.053 mmol) in 1-methyl-2
pyrrolidinone (0.25 ml) was heated at 1908C (bath) for 3.5 h, cooled to room
temperature, diluted with 30% aqueous sodium cyanide (1 ml), stirred for
30 min, and extracted with ethyl acetate (20 ml). The extract was washed with
30% aqueous sodium cyanide (2 ml) and brine (2 ml). The combined aqueous
layer was re-extracted with ethyl acetate (10 ml). The combined organic extract
was dried over sodium sulfate, and evaporated under vacuum. Twice
performed biotage chromatography of the residue (column 12M, eluting with
dichlomethane/methanol, 90:10) gave 9 in a mixture (27 mg) with 1-methyl-2
pyrrolidinone in a ratioꢂ1:1 by NMR. For 9:TLC:Rf ¼ 0:35 (dichlomethane/
methanol, 90:0). HPLC (conditions A): Rt ¼ 6:3 min. NMR (CDCl3, d, ppm):
1.13 (s, 3H), 1.15 (s, 3H), 2.73 (dAB, J ¼ 3:5 Hz, 1H), 2.76 (dAB, J ¼ 3:5 Hz,
1H), 3.01 (dd, J ¼ 11:9 and 7.3 Hz, 1H), 3.14 (dd, J ¼ 11:9 and 4.0 Hz, 1H),
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SYNTHESIS OF TWO 14C-LABELED b3-ADRENERGIC RECEPTOR AGONISTS
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4.16-4.26 (m, 2H), 4.32 (m, 1H), 6.68 (d, J ¼ 7:9 Hz, 1H), 6.95 (d, J ¼ 8:3 Hz,
1H), 6.98 (d, J ¼ 8:3 Hz, 2H), 7.05 (d, J ¼ 8:3 Hz, 1H), 7.20 (t, J ¼ 7:9 Hz, 1H),
7.21 (d, J ¼ 8:3 Hz, 2H), 7.31 (t, J ¼ 8:3 Hz, 1H), 7.34–7.42 (m, 2H), 7.86
(dd, J ¼ 8:8 and 2.2 Hz, 1H), 8.21 (br. s, 1H), 8.27 (d, J ¼ 7:9 Hz, 1H), 8.42
(d, J ¼ 2:2 Hz. 1H).
6-(4-(2-Amino-2-methylpropyl)phenoxy)-3-cyanopyridine, 10
A mixture of iodide 7 (475 mg, 1.29 mmol), potassium cyanide (85 mg,
1.3 mmol), and copper (I) iodide (124 mg, 0.65 mmol) in 1-methyl-2
pyrrolidinone (2.9 ml) was heated at 1908C (bath) for 3.5 h, and at 2008C
(bath) for 1 h, then cooled to room temperature, diluted with 30% aqueous
sodium cyanide (4 ml), stirred for 40 min, and extracted with ethyl acetate
(50 ml). The extract was washed with 30% aqueous sodium cyanide (5 ml) and
brine (2 ꢀ 3 ml). The combined aqueous layer was re-extracted with ethyl
acetate (10 ml). The combined organic extract was dried over sodium sulfate,
and evaporated under vacuum. Biotage chromatography of the residue
(column 40S, eluting with dichlomethane/methanol/ammonium hydroxide,
90:10:1) gave 10 (320 mg, 93%) as a grayish solid. TLC:Rf ¼ 0:31
(dichlomethane/methanol/ammonium hydroxide, 90:10:1). HPLC (conditions
A): Rt ¼ 3:2 min. NMR (CDCl3, d, ppm): 1.15 (s, 6H), 2.69 (s, 2H), 7.01 (d,
J ¼ 8:8 Hz, 1H), 7.07 (d, J ¼ 8:3 Hz, 2H), 7.25 (d, J ¼ 8:3 Hz, 2H), 7.90 (dd,
J ¼ 8:8 and 2.2 Hz, 1H), 8.46 (d, J ¼ 2:2 Hz, 1H). IR (KBr, n, cmꢁ1): 550, 766,
841, 890, 1018, 1129, 1165, 1205, 1288, 1381, 1474, 1507, 1592, 2231, 2931,
2962, 3431. UV (EtOH, lmax, nm): 463, 368, 238. MS (ES+, m/z, %): 268 (38,
M+1), 251 (100). HRMS (AP+): calculated for C16H17N3O: 268.1450, found:
268.1437.
6-(4-(2-Amino-2-methylpropyl)phenoxy)-3-[14c]-cyanopyridine, 10-½14Cꢃ
In the same manner as described above, starting from 7 (475 mg, 1.29 mmol),
potassium cyanide-[14C] (49.99 mCi, 55.1 mCi/mmol, 0.907 mmol), potassium
cyanide (25 mg, 0.384 mmol), and copper (I) iodide (124 mg, 0.65 mmol) in
1-methyl-2 pyrrolidinone (2.9 ml), 10-[14C] (450 mg) was obtained.
(S)-6-[4-[2-[3-(Indol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]phenoxy]-
3-cyanopyridine, 11
A mixture of amine 10 (93 mg, 0.35 mmol) and epoxide 1 (76 mg, 0.4 mmol) in
2-propanol (3 ml) was heated at 75–808C (bath) for 18 h, and evaporated under
vacuum. Flash chromatograpgy of the residue (silica gel column, eluting with
chloroform/methanol, 90:10) gave 11 (748 mg, 68%) as a light brown solid.
TLC:Rf ¼ 0:38 (chloroform/methanol, 90:10). HPLC (conditions B):
Rt ¼ 8:6 min. NMR (CDCl3, d, ppm): 1.11 (s, 3H), 1.13 (s, 3H), 2.75
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(s, 2H), 2.89 (dd, J ¼ 11:7 and 6.8 Hz, 1H), 3.02 (br. d, J ¼ 11:7 Hz, 1H),
4.07–4.17 (m, 3H), 6.49 (d, J ¼ 7:8 Hz, 1H), 6.59 (br. s 1H), 6.92–7.21 (m, 8H),
7.83 (dd, J ¼ 8:8 and 2.4 Hz, 1H), 8.15 (br. s, 1H), 8.39 (br. s, 1H). The
compound 11 is identical (TLC, HPLC, NMR) to an authentic sample of this
material.1
(S)-6-[4-[2-[3-(Indol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]phenoxy]-
3-[14C]-cyanopyridine, 11-[14C]
In the same manner as described above, starting from 10-[14C] (644 mg,
2.39 mmol), and epoxide 1 (520 mg, 2.75 mmol), in 2-propanol (20 ml), 11-[14C]
(748 mg, 68%) was obtained.
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-3-cyanopyridine, 9 (from amine 10)
A mixture of amine 10 (281 mg, 1.05 mmol) and epoxide 2 (287 mg, 1.2 mmol)
in 2-propanol (7 ml) was heated at 80–858C (bath) for 17 h, and evaporated
under vacuum. Biotage chromatography of the residue (column 40S, eluting
with dichloromethane/methanol, 93:7) gave 9 (427 mg, 80%) as a white solid.
TLC: Rf ¼ 0:32 (dichloromethane/methanol, 93:7). HPLC (conditions A):
Rt ¼ 6:2 min. NMR (CDCl3, d, ppm): 1.14 (s, 3H), 1.15 (s, 3H), 2.73 (dAB
,
J ¼ 3:5 Hz, 1H), 2.76 (dAB, J ¼ 3:5 Hz, 1H), 3.00 (dd, J ¼ 11:9 and 7.0 Hz,
1H), 3.13 (dd, J ¼ 11:9 and 4.0 Hz, 1H), 4.18–4.25 (m, 2H), 4.32 (m, 1H), 6.68
(d, J ¼ 8:3 Hz, 1H), 6.95 (d, J=8.3 Hz, 1H), 6.98 (d, J ¼ 8:3 Hz, 2H), 7.05
(d, J ¼ 7:9 Hz, 1H), 7.21 (t, J ¼ 7:9 Hz, 1H), 7.22 (d, J ¼ 8:3 Hz, 2H), 7.32
(t, J=8.3 Hz, 1H), 7.34–7.42 (m, 2H), 7.86 (dd, J=8.8 and 2.2 Hz, 1H), 8.11
(br. s, 1H), 8.28 (d, J=7.9 Hz, 1H), 8.43 (d, J=2.2 Hz. 1H). IR (KBr, n, cmꢁ1):
723, 883, 1015, 1089, 1283, 1380, 1474, 1592, 2229, 2918, 2957, 3408. UV
(EtOH, lmax, nm): 332, 320, 286, 243. MS (ES+, m/z, %): 507 (100, M+1).
HRMS (AP+): calculated for C31H30N4O3: 507.2396, found: 507.2395.
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-3-[14C]-cyanopyridine, 9-[14C]
In the same manner as described above, starting from 10-[14C] (347 mg,
1.29 mmol), and epoxide 2 (350 mg, 1.46 mmol), in 2-propanol (9 ml), 9-[14C]
(550 mg, 84%) was obtained.
(S)-6-[4-[2-[3-(Indol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]phenoxy]-
pyridine-3-carboxamide, A
To a solution of nitrile 11 (105 mg, 0.23 mmol) in dimethylsulfoxide (0.6 ml)
were added potassium carbonate (17 mg, 0.12 mmol) and water (0.1 ml). After
15 min, 30% hydrogen peroxide (65 mL, 0.68 mmol) was added dropwise. The
reaction mixture was stirred for 3.5 h at room temperature, then diluted with
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SYNTHESIS OF TWO 14C-LABELED b3-ADRENERGIC RECEPTOR AGONISTS
671
ethyl acetate (20 ml), washed with saturated aqueous sodium chloride
(2 ꢀ 3 ml), dried over sodium sulfate, and evaporated under vacuum. Flash
chromatography of the residue (silica gel column, eluting with chloroform/
methanol/ammonium hydroxide, 85:15:1.5) gave A (100 mg, 92%) as a white
solid. TLC: Rf ¼ 0:30 (chloroform/methanol/ammonium hydroxide, 90:10:1).
HPLC (conditions B): Rt ¼ 4:5 min. NMR: (CD3OD, d, ppm): 1.10 (s, 6H),
2.75 (d, J ¼ 5:4 Hz, 2H), 2.85 (m, 1H), 2.99 (m, 1H), 4.05–4.15 (m, 3H), 6.45
(dd, J ¼ 4:9 and 3.4 Hz, 1H), 6.49 (d, J ¼ 3:4 Hz, 1H), 6.85–6.95 (m, 5H), 7.05
(d, J ¼ 2:9 Hz, 1H), 7.23 (d, J ¼ 8:8 Hz, 2H), 8.18 (dd, J ¼ 8:8 and 2.4 Hz,
1H), 8.57 (d, J ¼ 2:4 Hz, 1H). The compound is identical (TLC, HPLC,
NMR) to an authentic sample of A.1
(S)-6-[4-[2-[3-(Indol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]phenoxy]-
pyridine-3-[14C]-carboxamide, A-½14Cꢃ
In the same manner as described above, starting from nitrile 11-[14C] (748 mg,
1.63 mmol), potassium carbonate (118 mg, 0.85 mmol), water (0.3 ml) and 30%
hydrogen peroxide (0.46 ml, 4.79 mmol) in dimethylsulfoxide (4 ml), A-[14C]
(582 mg, 75%) was obtained.
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-pyridine-3-carboxamide, B
To a solution of nitrile 9 (396 mg, 0.78 mmol) in dimethylsulfoxide (2 ml) were
added potassium carbonate (59 mg, 0.427 mmol) and water (0.1 ml). After
5 min, 30% hydrogen peroxide (250 ml) was added dropwise. The reaction
mixture was stirred for 4 h at room temperature, then diluted with water
(1 ml), and extracted with ethyl acetate (40 ml). The extract was washed with
10% aqueous sodium chloride (2 ml), brine (2 ml), dried over sodium sulfate,
and evaporated under vacuum. Biotage chromatography of the residue
(column 40S, eluting sequentially with 500 ml of dichloromethane/methanol,
90:10; and with 1000 ml of dichloromethane/methanol/ammonium hydroxide,
92:8:08) gave B (385 mg, 94%) as a white solid. TLC: Rf ¼ 0:24 (dichlor-
omethane/methanol/ammonium hydroxide, 92:8:08). HPLC (conditions A):
Rt ¼ 3:8 min. NMR (CDCl3, d, ppm): 1.13 (s, 3H), 1.15 (s, 3H), 2.72 (dAB
,
J ¼ 3:5 Hz, 1H), 2.74 (dAB, J ¼ 3:5 Hz, 1H), 3.00 (dd, J ¼ 11:9 and 6.6 Hz,
1H), 3.12 (dd, J ¼ 11:9and 4.0 Hz, 1H), 4.19–4.24 (m, 2H), 4.32 (m, 1H), 6.68
(d, J ¼ 7:9 Hz, 1H), 6.90 (d, J ¼ 8:8 Hz, 1H), 6.96 (d, J ¼ 8:8 Hz, 2H), 7.04
(d, J ¼ 7:9 Hz, 1H), 7.20 (t, J ¼ 7:9 Hz, 1H), 7.21 (d, J ¼ 8:8 Hz, 2H), 7.31
(t, J ¼ 7:9 Hz, 1H), 7.34–7.41 (m, 2H), 8.12 (dd, J ¼ 8:8 and 2.6 Hz, 1H), 8.16
(br. s, 1H), 8.29 (d, J ¼ 7:9 Hz, 1H), 8.54 (d, J ¼ 2:6 Hz. 1H). The compound
is identical (TLC, HPLC, NMR) to an authentic sample of B.2
Copyright # 2006 John Wiley & Sons, Ltd.
J Label Compd Radiopharm. 2006; 49: 663–673
DOI: 10.1002/jlcr

672
B. A. CZESKIS ET AL.
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-pyridine-3-[14C]-carboxamide, B-½14Cꢃ
In the same manner as described above, starting from nitrile 9-[14C] (550 mg,
1.08 mmol), potassium carbonate (85 mg, 0.615 mmol), water (0.15 ml) and
30% hydrogen peroxide (0.35 ml) in dimethylsulfoxide (2.8 ml), B-[14C]
(370 mg, 65%) was obtained.
(S)-6-[4-[2-[3-(Indol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]phenoxy]-
pyridine-3-carboxamide glycolate, A glycolate
To a solution of A (85 mg, 0.179 mmol) in ethanol (0.55 ml) was added a
solution of glycolic acid (14 mg, 0.184 mmol) in ethanol (0.37 ml) dropwise.
The reaction mixture was stirred for 30 min at room temperature and
evaporated under vacuum. The residue was triturated with ethyl ether
(3 ꢀ 3 ml), and the supernatant liquid was decanted each time. After drying
under vacuum obtained A glycolate (88 mg, 89%) as a white solid. HPLC
(conditions B): Rt ¼ 4:5 min. NMR: (DMSO-D6, d, ppm): 1.02 (s, 3H), 1.03 (s,
3H), 2.71 (s, 2H), 2.82 (m, 1H), 2.95 (m, 1H), 3.71 (s, 2H), 4.0.1 (m, 3H), 6.39
(br. s, 1H), 6.43 (dd, J ¼ 6:8 and 1.9 Hz, 1H), 6.88–6.99 (m, 5H), 7.14 (br. s,
1H), 7.18 (d, J ¼ 8:3 Hz, 2H), 7.42 (br. s, 1H), 7.97 (br. s, 1H), 8.18 (dd,
J ¼ 8:8 and 2.4 Hz, 1H), 8.56 (d, J ¼ 2:4 Hz, 1H), 11.00 (s, 1H). The
compound is identical (HPLC, NMR) to an authentic sample of A glycolate.1
(S)-6-[4-[2-[3-(Indol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-pyridine-3-[14C]-carboxamide glycolate, A-½14Cꢃ glycolate
In the same manner as described above, starting from A-[14C] (203 mg,
0.426 mmol) in ethanol (1.3 ml), and glycolic acid (33 mg, 0.434 mmol) in
ethanol (0.9 ml), A-[14C] glycolate (191 mg, 81%) was obtained. The final
sample had specific activity 62.9 mCi/mmol, and radiochemical purity 99.0%.
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-pyridine-3-carboxamide succinate, B succinate
To a solution of B (350 mg, 0.667 mmol) in ethyl acetate (2 ml) at 608C (bath)
was added a solution of succinic acid (40 mg, 0.339 mmol) in ethanol (1 ml)
dropwise. The precipitate formed was dissolved by addition of ethanol
(2 ꢀ 0.5 ml) followed by stirring at 708C (bath) for 20 min. The reaction
mixture was allowed to cool to room temperature, and evaporated under
vacuum. The residual solid was triturated with ethyl ether (3 ml), filtered off,
rinsed with ethyl ether (2 ꢀ 2 ml), and dried under vacuum to give B succinate
(340 mg, 87%) as a white solid. HPLC (conditions A): Rt ¼ 3:8 min. NMR
(CD3OD, d, ppm): 1.28 (s, 6H), 2.51 (s, 2H), 2.92 (s, 2H), 3.25 (dd, J ¼ 12:3
and 8.3 Hz, 1H), 3.40 (dd, J ¼ 12:3 and 2.6 Hz, 1H), 4.26–4.29 (m, 2H),
Copyright # 2006 John Wiley & Sons, Ltd.
J Label Compd Radiopharm. 2006; 49: 663–673
DOI: 10.1002/jlcr

SYNTHESIS OF TWO 14C-LABELED b3-ADRENERGIC RECEPTOR AGONISTS
673
4.36 (m, 1H), 6.70 (d, J ¼ 7:9 Hz, 1H), 6.97 (d, J ¼ 8:8 Hz, 1H), 6.96
(d, J ¼ 8:3 Hz, 2H), 7.05 (d, J ¼ 8:3 Hz, 1H), 7.11 (t, J ¼ 7:9 Hz, 1H), 7.26
(d, J ¼ 8:3 Hz, 2H), 7.26–7.31 (m, 1H), 7.31 (t, J ¼ 7:9 Hz; 1H), 7.40
d, J ¼ 7:9 Hz, 1H), 8.24 (dd, J ¼ 8:8 and 2.6 Hz, 1H), 8.29 (d, J ¼ 7:9 Hz, 1H),
8.60 (d, J ¼ 2:6 Hz. 1H).
(S)-6-[4-[2-[3-(9H-Carbazol-4-yloxy)-2-hydroxypropylamino]-2-methylpropyl]
phenoxy]-pyridine-3-[14C]-carboxamide succinate, B-½14Cꢃ succinate
In the same manner as described above, starting from B-[14C] (370 mg,
0.703 mmol) in ethyl acetate (1.5 ml), and succinic acid (42 mg, 0.356 mmol) in
ethanol (1 ml), B-[14C] succinate (378 mg, 92%) was obtained. The final sample
had specific activity 51.8 mCi/mmol, and radiochemical purity 98.7%.
Acknowledgements
Authors are grateful to Chris Rito of Discovery Chemistry research, and Mary
Peters of Chemical Process Research and Development for the supplying of
some of the intermediates and experimental procedures.
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Copyright # 2006 John Wiley & Sons, Ltd.
J Label Compd Radiopharm. 2006; 49: 663–673
DOI: 10.1002/jlcr