A Practical and Scalable Synthesis of GTx-134, an IGF-1R Inhibitor

Article abstract of DOI:10.1002/jhet.2443

A practical and scalable synthesis of GTx-134, a novel small-molecule inhibitor of insulin-like growth factor 1 receptor showing antitumor activity in preclinical models of multiple myeloma, is reported.

Full text of DOI:10.1002/jhet.2443

Month 2015
A Practical and Scalable Synthesis of GTx-134, an IGF-1R Inhibitor
*
Yahu A. Liu [1] and Vlad E. Gregor
ChemBridge Research Laboratories, Inc., San Diego, California 92127
*
E-mail: yahu_a_liu@yahoo.com
Received January 9, 2015
DOI 10.1002/jhet.2443
Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).
This work was dedicated in memory of Dr. Vlad E. Gregor (1954–2010) who made great contributions to medicinal chemistry and drug discovery.
A practical and scalable synthesis of GTx-134, a novel small-molecule inhibitor of insulin-like growth
factor 1 receptor showing antitumor activity in preclinical models of multiple myeloma, is reported.
J. Heterocyclic Chem., 00, 00 (2015).
INTRODUCTION
RESULTS AND DISCUSSION
Multiple myeloma (MM) is a cancer of plasma cells, a
type of white blood cells normally responsible for produc-
ing antibodies [2]. In MM, collections of abnormal plasma
cells accumulate in the bone marrow where they receive
proliferative, survival, and migratory signals from the bone
marrow microenvironment [2]. MM remains the most part
incurable, although the therapeutic landscape for the man-
agement of MM has been changed by the advent of
autologous stem cell transplantation and several novel ther-
apeutics such as the proteomsome inhibitor, bortezomib
and the immunomodulatory drugs, thalidomide, and
lenalidomide [2]. Insulin-like growth factor 1 receptor
(IGF-1R) is a receptor tyrosine kinase widely expressed
in normal tissues where it functions in growth regulation
[3]. IGF-1R is activated by IGF-1 and by the related
growth factor IGF-2. It is well known that IGF-1R stimu-
lates the proliferation and survival of MM cells as well as
their migration, adhesion, and invasion [3]. Therefore,
inhibition of IGF-1R represents an attractive therapeutic
target for MM [3,4].
GTx-134 (1) (Fig. 1), a novel small-molecule IGF-1R in-
hibitor, was discovered in our lab through structure-based
drug design [5,6]. GTx-134 (1) reduced autophosphoryla-
tion of its target receptor and inhibited signaling through
the PI3k/Akt pathway, inducing apoptosis of primary pa-
tient MM cells that led to an antitumor efficacy in a human
melanoma cell lines (HMCL) xenografts model [7]. Encour-
aged by the growing interests in compound 1 and its close
analogs [8], herein, we report an optimized, practical, and
scalable synthetic route toward compound 1 [9].
The synthetic work began from commercially available
4-amino-5-nitrophthalimide (2). According to various
research reports [10], Mitsunobu reaction could be a
very convenient method to make piperidine phthalimide 3
from phthalimide 2 using tert-butyl 4-hydroxypiperidine-
1-carboxylate (4) (Scheme 1). Mitsunobu reaction requires
stoichiometric quantities of an azodicarboxylate such as
diethyl azodicarboxylate or diisopropyl azodicarboxylate
and phosphorane reagents such as triphenylphosphine,
which not only adds additional cost but also increases
complexity of purification of the product. Thus, we were
inclined to develop a cost-effective method which is more
suitable for larger scale synthesis of phthalimide 3.
Inspired by a method described in a patent [11],
we found that a simple heating of 2 with tert-butyl 4-
aminopiperidine-1-carboxylate (5) in the presence of
imidazole in 1,4-dioxane in a sealed pressure vessel gave
phthalimide 3 in good yield (54%) (Scheme 1).
Stepwise synthesis of 1. The step by step synthesis of 1
from 3 was illustrated in Scheme 2. This linear synthesis
began from the hydrogenation of 3 which was performed
smoothly to give diaminophthalimide
6 in almost
quantitative yield (>99%). The reaction of 6 with 4-iodo-
2-methoxynicotinic aldehyde (7) was carried out in
methanol in the presence of HOAc [12,13]. An oxidizing
reagent is usually required for the formation of benzyl
imidazole [14], but we used O2 in the air as the oxidizing
reagent in order to avoid introducing additional chemicals
into the reaction mixture. The reaction, carried out in a
flask open to the air, reached completion after 72h to
© 2015 HeteroCorporation

Y. A. Liu and V. E. Gregor
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The amination of both iodide 11 and chloride 12 amine
13 was completed by heating in EtOH in the presence of
triethylamine to afford aminopyridone 14 in 71.2% yield
[17]. The reduction of phthalimide 14 using zinc dust in
acetic acid, followed by removing Boc protective group
with 4.0 M HCl in 1,4-dioxane, gave amide 15 in 63.4%
yield [5,18]. The addition of the piperidine in 15 to methyl
vinyl sulfone was carried out by heating in a mixed solvent
of EtOH and isopropanol (v/v, 1:1), providing the final tar-
get GTx-134 (1) in 78.5% yield [19]. The overall yield of
the linear route from 3 to 1 is 26.8%. Compound 1 has
two conformational isomers 1a and 1b, possibly owing to
tautomeric property of the imidazole moiety in 1 and hy-
drogen bond between imidazole proton and pyridone
O (Fig. 4), which was evidenced by the two sets of peaks
Figure 1. Structure of GTx-134 (1).
afford tricyclic compound phthalimido imidazole 8 in 92%
yield. Demethylation of 2-methoxypyridine 8 using HCl
solution (4.0 M in 1,4-dioxane) resulted in a mixture of
iodopyridone 9 and chloropyridone 10 as the iodine in
both 8 and 9 could be replaced by chlorine under the
reaction condition [15]. Both iodide 9 and chloride 10 are
very insoluble, which made the separation of them from
the crude difficult, so the crude material was used in the
next step directly. The ratio of iodide 9 and chloride 10
1
in H NMR and 13C NMR (DMSO-d6), one set for each
of the conformational isomers. In order to prove the two
sets of the peaks in NMR spectra belong to the two confor-
mational isomers 1a and 1b, not two different compounds,
compound 1 was converted to di-hydrochloride salt
1
1
in the crude was proved to be 0.5:1 by H NMR analysis
(1 · 2HCl) which showed only one set of peaks in both H
NMR and 13C NMR obtained in DMSO-d6, an unambigu-
ous evidence of single compound.
(Fig. 2).
Because the Boc protective group on piperidine N in 8
was eliminated during the demethylation, it had to be
added to piperidines in 9 and 10 to provide iodide 11 and
chloride 12, respectively [16]. Iodide 11 and chloride 12
were isolated together from the reaction crude, although
As shown in Scheme 3, we had also attempted to use
chloronicotinic aldehyde 16 [20] as a replacement for its
iodo analog 7 to access compound 14. Aldehyde 16 was
treated with diamine 6 in MeOH in the presence of HOAc.
The reaction proceeded well but only afforded the desired
cyclized product 17 in 43% yield, much lower than the cy-
clization reaction of 7 with 6 (92%, Scheme 2), probably
because of different reactivity of aldehyde moiety. With
compound 17 in hand, de-methylation and subsequent
Boc protection generated compound 12 in 83% yield over
two steps. The following displacement of chlorine with
amine 13 in Et3N/EtOH afforded compound 14 in 72%
yield. This synthetic route was deprioritized because of
the low reaction yield from the cyclization reaction of di-
amine 6 and chloronicotinic aldehyde 16.
1
separation of one from the other was not successful. H
NMR spectra in both DMSO-d6 and CDCl3 indicated that
the ratio of iodide 11 to chloride 12 in the product was
0.5:1, which is consistent with that of 9 to 10 (Fig. 3).
The yield of the two steps from 8 to 11/12 was 83%, which
was calculated based on the weight average molecular
weight 528.41 of the 0.5:1 mixture of 11 and 12.
Scheme 1
Scalable synthesis of 1. The aforementioned stepwise
synthetic procedure was then modified into a scalable
procedure in which only column chromatography in the
reaction sequence from 3 to 1 was performed at the last
step. The synthesis started from hydrogenation of nitro
compound 3 to give diaminophthalimide 6 which was
reacted with nicotinic aldehyde 7 to give crude tricyclic
compound phthalimido imidazole 8. Demethylation of 8
followed by evaporation and basification resulted in a
crude containing both iodopyridone 9 and chloropyridone
10, which was then reacted with Boc2O to afford a crude
mixture of 11 and chloride 12. The amination of crude
iodide 11 and chloride 12 by heating with chiral amine
13 in EtOH afforded crude aminopyridone 14, which was
reduced with Zn dust in HOAc to give crude amide 15.
The transformation of 15 to 1 was carried out by heating
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Scheme 2
8.00
ppm (f1)
7.50
7.00
6.50
6.00
Figure 2. 1H NMR (DMSO-d6) of the crude [9 + 10]. The peaks at 6.56 (d, J = 5.6 Hz, 1H), 7.22 (d, J = 5.6 Hz, 1H), 7.50 (s, 1H), and 7.88 (s, 1H) belong
to 9, and the ones at 6.13 (d, J = 5.6 Hz, 1H), 7.53 (d, J = 5.6 Hz, 1H), 7.56 (s, 1H), and 7.90 (s, 1H) to 10.
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Y. A. Liu and V. E. Gregor
Vol 000
8.50
8.00
7.50
7.00
6.50
ppm (f1)
8.50
8.00
7.50
7.00
6.50
ppm (f1)
Figure 3. 1H NMR of the mixture of [11 + 12]: (a) in CDCl3. The peaks at 6.86 (d, J = 7.0 Hz), 7.09 (d, J = 7.0 Hz), 8.21 (s), and 8.60 (s) belong to 11,
while ones at 6.49 (d, J = 7.0 Hz), 7.38 (d, J = 7.0 Hz), 8.20 (s), and 8.57 (s) to 12. (b) in DMSO-d6. The peaks at 6.82 (d, J = 6.8 Hz), 7.37 (d, J = 6.8 Hz),
8.22 (s), and 8.34 (s) belong to 11, while the ones at 6.57 (d, J = 6.8 Hz), 6.82 7.71 (d, J = 7.2 Hz), 8.20 (s), and 8.31 (s) to 12.
15 with methyl vinyl sulfone in a mixed solvent of EtOH
and 2-propanol. The reaction crude was purified to afford
final product 1 by chromatography which was the only
column chromatography employed from 3 till the last
step. The overall yield of this scalable procedure is
27.2% from 3, very similar to that the stepwise procedure
(26.8%), but the separations and purifications in the
stepwise synthesis were eliminated except in the last step.
In summary, we have described a practical and scalable
synthesis of GTx-134 (1) as well as stepwise synthetic
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Scalable Synthesis of GTx-134
Figure 4. Two conformational isomers: 1a and 1b.
(320:10:1) afforded 3 (5.27g, 54%). 1H NMR (CDCl3)
Scheme 3
δ =1.48 (s, 9H), 1.64–1.68 (2H), 2.31–2.42 (2H), 2.74–2.80
(2H), 4.19–4.27 (3H), 7.03 (br s, 2H, NH), 7.33 (s, 1H),
1
8.59 (s, 1H). H NMR (DMSO-d6) δ= 1.42 (s, 9H), 1.63–
1.66 (2H), 2.04–2.15 (2H), 2.80 (br, 2H), 4.03 (br, 2H) 4.15
(m, 1H), 7.38 (s, 1H), 8.23 (s, 1H), 8.36 (br s, 2H, NH). 13
C
NMR (CDCl3) δ =28.4, 28.7, 43.4, 49.4, 79.9, 114.0, 118.0,
123.1, 133.7, 137.2, 149.2, 154.6, 166.1, 166.2. 13C NMR
(DMSO-d6) δ =28.0, 28.2, 43.5, 48.3, 78.7, 114.2, 115.6,
121.9, 131.6, 136.2, 150.1, 153.7, 165.8, 165.9. MS (ESI):
m/z= 391 [M+ H+].
tert-Butyl 4-(5,6-diamino-1,3-dioxoisoindolin-2-yl)piperidine-
1-carboxylate (6). To a mixture of nitro compound 3 (2.54g,
procedures with characterization of all key intermediates.
This novel small-molecule inhibitor of IGF-1R was pre-
pared from commercially available chemicals via a nine-
step reaction sequence in which only two chromatographic
purifications were employed.
6.51mmol) and 10% Pd/C (254.0mg) in 2-propanol (5mL)
was added MeOH (80mL). After it was stirred under
atmospheric hydrogen for 18h, the reaction mixture was
filtered through a pad of Celite and evaporated to give 6
1
(2.33g, 99%). H NMR (CDCl3) δ =1.47 (s, 9H), 1.62–
1.65 (2H), 2.31–2.41 (2H), 2.75 (br, 2H), 4.11–4.34 (3H),
1
7.06 (s, 2H). H NMR (DMSO-d6) δ =1.42 (s, 9H), 1.55–
EXPERIMENTAL
1.59 (2H), 2.03–2.13 (2H), 2.67–2.88 (2H), 3.99–4.07 (3H),
5.60 (br s, 4H, NH), 6.83 (s, 2H). 13C NMR (CDCl3)
δ =28.4, 29.1, 43.0, 48.6, 79.7, 110.2, 124.6, 139.4, 154.7,
168.8. 13C NMR (DMSO-d6) δ=28.6, 28.8, 43.0, 47.5,
78.0, 106.6, 120.9, 139.8, 153.7, 168.6. MS (ESI): m/z=
All commercial reagents and solvents were used without
purification. H and 13C NMR spectra were recorded on a
1
Bruker 300MHz spectrometer using TMS as internal stan-
dard set at 0 ppm. Thin-layer chromatography analysis was
carried out on silica gel 60 F254 precoated aluminum
sheets, and UV light was used for detection. Separation
by flash column chromatography was performed on Merck
silica gel (230–400 mesh). Low-resolution mass spectra
(ESI) were obtained with 1100LCMSD VL Series (Agilent
Technologies, Santa Clara, CA) spectrometer. The CHN
analysis was performed by Numega Resonance Labs, San
361 [M +H+].
tert-Butyl 4-(2-(4-iodo-2-methoxypyridin-3-yl)-5,7-dioxoimida
zo[4,5-f]isoindol-6(1H,5H,7H)-yl)piperidine-1-carboxylate
(8).
To a solution of 1,2-diamino compound 6 (2.23g,
6.20mmol) in MeOH (100mL) was added 4-iodo-2-
methoxynicotinic aldehyde (7) (1.71g, 6.51mmol) and
HOAc (5.0 mL) resulting in a mixture which was stirred at
the room temperature for 72h, and evaporated under reduced
pressure (the bath temperature from 60°C till 95°C).
The chromatography of the residue with DCM/MeOH/28%
aqueous NH4OH (240:10:1) furnished 8 (3.44 g, 92%).
1H NMR (CDCl3) δ =1.43 (s, 9H), 1.67–1.70 (2H), 2.38–
2.45 (2H), 2.69–2.83 (2H), 3.84 (s, 3H), 4.18–4.33 (3H),
7.48 (d, J=5.4Hz, 1H), 7.87 (d, J=5.4Hz, 1H), 8.03 (br,
2H). 1H NMR (DMSO-d6) δ =1.43 (s, 9H), 1.69–1.71 (2H),
2.14–2.24 (m, 2H), 2.74–2.92 (2H), 3.82 (s, 3H), 4.00–4.15
(2H), 4.24 (m, 1H), 7.66 (d, J=5.4Hz, 1H), 8.02 (2H), 8.03
(d, J=5.4Hz, 1H). 13C NMR (CDCl3) δ =28.4, 28.9, 44.0,
Diego, CA 92121.
4-(5-Amino-6-nitro-1,3-dioxo-1,3-dihydro-isoindol-2-yl)-
piperidine-1-carboxylic acid tert-butyl ester (3). A mixture of 5-
amino-6-nitro-isoindole-1,3-dione (2) (5.18g, 25.00mmol),
tert-butyl 4-amino-piperidine-1-carboxylate (5) (6.01 g,
30.0mmol), and imidazole (4.08g, 60.0mmol) in 1,4-
dioxane (200 mL) was sealed in a ChemGlass pressure
vessel. After it was heated at 140°C for 72h, the reaction
mixture was evaporated to dryness at 95°C (the bath
temperature) under reduced pressure. The chromatography
of the residue with DCM/MeOH/28% aqueous NH3H2O
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48.9, 54.6, 80.1, 111.0, 118.5, 126.8, 128.0, 149.0, 151.9,
154.8, 161.5, 168.1, 174.8. 13C NMR (DMSO-d6) δ =28.1,
28.6, 43.0, 48.1, 54.1, 78.8, 107.7, 113.1, 114.8, 119.9,
125.3, 126.0, 127.1, 137.7, 146.7, 148.8, 152.8, 153.9,
of 12), 8.20 (s, 2/3H of 12), 8.22 (s, 1/3H of 11), 8.31
(s, 2/3H of 12), 8.34 (s, 1/3H of 11). MS (ESI): m/z = 590
and 498 [M + H+].
(R)-tert-Butyl 4-(2-(4-((3-(2,4-dimethylphenoxy)-2-hydroxypropyl)
161.2, 167.8, 172.0. MS (ESI): m/z=604 [M+H+].
amino)-2-oxo-1,2-dihydropyridin-3-yl)-5,7-dioxoimidazo[4,5-f]
isoindol-6(1H,5H,7H)-yl)piperidine-1-carboxylate (14). To a
suspension of a mixture of iodide 11 and chloride 12 (11/
12=1:2, mol/mol, 2.41g, 4.56mol) in EtOH (50mL) was
added (R)-1-amino-3-(2,4-dimethyl-phenoxy)-propan-2-ol
(13) (1.34g, 6.84mmol) and Et3N (1.27mL, 922.9mg,
9.12mmol) resulting a mixture which was heated in a
ChemGlass pressure vessels at 100°C for 14h and
then concentrated. The residues was subjected to
chromatography with DCM/MeOH/28% aqueous NH3H2O
2-(4-Iodo-2-oxo-1,2-dihydropyridin-3-yl)-6-(piperidin-4-yl)
imidazo[4,5-f]isoindole-5,7(1H,6H)-dione (9) and 2-(4-chloro-2-
oxo-1,2-dihydropyridin-3-yl)-6-(piperidin-4-yl)imidazo[4,5-f]
isoindole-5,7(1H,6H)-dione (10).
A mixture of 2-
methoxypiridine compound (8) (3.38g, 5.60mmol), HCl in
1,4-dioxane (4M, 200mL), and H2O (1.80 mL) was heated
at 70°C for 4.0h, and evaporated under reduced pressure
(the bath temperature <60°C) to result in a residual crude
which was azeotropically distilled with 2-propanol under
reduced pressure (the bath temperature<98°C). The
residue was diluted with a mixed solvent of MeOH and
DCM (1:4, v/v, 250mL), basified with 28% aqueous
NH3H2O (5mL), sonicated for 10min, and evaporated to
dryness to provide a crude product which contained both 9
and 10. 1H NMR (DMSO-d6) δ=1.26–1.36 (2H), 1.76-1.80
(2H), 2.37–2.60 (2H), 2.90–2.94 (2H), 3.68–3.77 (1H), 6.13
(d, J=5.4Hz, 2/3H of 10), 6.56 (d, J=5.4Hz, 1/3H of 9),
7.22 (d, J=5.4Hz, 1/3H of 9), 7.50 (s, 1/3H of 9), 7.53 (s,
J=5.4Hz, 2/3H of 10), 7.56 (s, 2/3H of 10), 7.88 (s, 1/3H
of 9), 7.90 (s, 2/3H of 10). MS (ESI): m/z=490 and 398
1
(150:10:1) to give 14 (2.13g, 71%). H NMR (DMSO-d6)
δ = 1.30 (s, 9H), 1.66–1.70 (2H), 2.12–2.18 (2H), 2.18 (s,
3H), 2.20 (s, 3H), 2.72–2.90 (2H), 3.55 (m, 1H), 3.70 (m,
1H) 3.95–4.09 (4H), 4.11–4.24 (2H), 5.54 (d, J=5.2Hz,
1H, OH), 6.20 (d, J=7.6Hz, 1H), 6.82 (d, J= 8.4Hz, 1H),
6.91 (d, J=8.4Hz, 1H), 6.96 (s, 1H), 7.37 (m, 1H), 7.63 (s,
1H), 8.08 (s, 1H), 10.94 (1H, NH), 11.28 (s, 1H, NH). 13C
NMR (DMSO-d6) δ = 15.9, 20.2, 28.0, 28.6, 45.6, 47.9,
67.6, 69.6, 78.7, 90.9, 94.6, 107.7, 111.1, 111.8, 124.4,
124.9, 125.5, 127.0, 129.0, 131.1, 135.8, 136.4, 145.1,
153.8, 154.3, 155.8, 157.0, 162.3, 168.1 (one C is missing).
[M + H+].
MS (ESI): m/z=657 [M+H+].
(R)-2-(4-((3-(2,4-dimethylphenoxy)-2-hydroxypropyl)amino)-2-
oxo-1,2-dihydropyridin-3-yl)-6-(piperidin-4-yl)-6,7-dihydroimidazo
[4,5-f]isoindol-5(3H)-one (15). A suspension of phthalimide
tert-Butyl 4-(2-(4-iodo-2-oxo-1,2-dihydropyridin-3-yl)-5,7-
dioxoimidazo[4,5-f]isoindol-6(1H,5H,7H)-yl)piperidine-
1-carboxylate (11) and tert-butyl 4-(2-(4-chloro-2-oxo-1,
2-dihydropyridin-3-yl)-5,7-dioxoimidazo[4,5-f]isoindol-6(1H,5H,7H)-
14 (2.0 g, 3.05 mmol) and zinc dust (2.0 g, 30.6 mmol) in
HOAc (40 mL) was heated till refluxing (bath temperature
120°C) for 2h and concentrated to result in a crude, which
was then mixed with HCl in 1,4-dioxane (4.0 M, 40 mL),
heated at 90°C for 1h and evaporated. The residue was
diluted with a mixed solvent of MeOH and DCM (1:1, v/v,
50mL), basified with aqueous NH3H2O (28% in H2O,
10mL), concentrated, and loaded on silica gel to subject a
chromatographic purification with DCM/MeOH/28%
aqueous NH3H2O (90:10:1) to furnish 15 (1.05 g, 63.4%).
1H NMR (MeOH-d4) δ =2.11–2.21 (4H), 2.24 (s, 3H), 2.25
(s, 3H), 3.17–3.24 (2H), 3.54–3.57 (2H), 3.67 (m, 1H), 3.80
(m, 1H), 4.03–4.11 (2H), 4.27 (m, 1H), 4.43 (m, 1H), 4.52
(s, 2H), 6.32 (d, J= 7.6 Hz, 1H), 6.78 (d, J= 8.2 Hz, 1H),
6.90 (d, J=8.2Hz, 1H), 6.96 (s, 1H), 7.29 (d, J=7.6Hz,
1H), 7.49 (br s, 1H), 7.86 (s, 1H). 13C NMR (MeOH-d4)
δ =16.5, 20.7, 28.1, 44.9, 46.7, 47.6, 70.1, 70.7, 93.6, 97.0,
112.3, 113.8, 116.8, 119.7, 122.4, 127.0, 127.6, 128.2,
131.0, 132.5, 136.4, 137.0, 156.1, 159.0, 164.7, 171.3 (two
yl)piperidine-1-carboxylate (12).
To a solution of the crude
product of the last step (mixture of 9 and 10) in DCM
(200mL) was added Et3N (1.92 mL, 1.4 g, 13.8 mmol) at 0°C
under N2, followed by the addition of the solution of Boc2O
(1.52 g, 6.96 mmol) in DCM (50 mL). After the reaction
mixture was stirred at 0°C for 1 h and at the room
temperature for 19 h, MeOH (5.0mL) was added slowly
with at 0°C. The reaction mixture was then evaporated
under reduced pressure at 55°C (the bath temperature) to
afford
a
crude residue which was subjected to
chromatography with DCM/MeOH/28% aqueous NH3H2O
(115:10:1) to afford a mixture of 11 and 12 (2.46g, yield
83% for two steps, which was calculated based on the
weight average molecular weight 528.41 of the mixture of
11 and 12 in 1:2, the ratio determined by 1H NMR
analysis). 1H NMR (CDCl3) δ =1.47 (s, 9H), 1.69–1.72
(2H), 2.37–2.48 (2H), 2.72–2.82 (2H), 4.25–4.33 (3H), 6.49
(d, J=7.0Hz, 2/3H of 12), 6.86 (d, J=7.0Hz, 1/3H of 11),
7.09 (d, J=7.0Hz, 1/3H of 11), 7.38 (d, J=7.0Hz, 2/3H of
12), 8.20 (s, 2/3H of 12), 8.21 (s, 1/3H of 11), 8.57 (s, 2/3H
Cs are missing). MS (ESI): m/z=543 [M+H+].
2-{4-[(R)-3-(2,4-Dimethyl-phenoxy)-2-hydroxy-propylamino]-
2-oxo-1,2-dihydro-pyridin-3-yl}-6-[1-(2-methanesulfonyl-ethyl)-
piperidin-4-yl]-6,7-dihydro-3H-1,3,6-triaza-s-indacen-5-one
(1). To a solution of piperidine compound 15 (1.00 g,
1.84 mmol) in a mixed solvent of EtOH (25 mL) and
2-propanol (25 mL) was added methyl vinyl sulfone
1
of 12), 8.60 (s, 1/3H of 11). H NMR (DMSO-d6) δ=1.43
(s, 9H), 1.71–1.74 (2H), 2.12–2.22 (2H), 2.76–2.92
(2H), 4.00–4.11 (2H), 4.27–4.35 (1H), 6.57 (d,
J = 6.8 Hz, 2/3H of 12), 6.82 (d, J = 6.8 Hz, 1/3H of 11),
7.37 (d, J = 6.8 Hz, 1/3H of 11), 7.71 (d, J = 7.2 Hz, 2/3H
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Month 2015
Scalable Synthesis of GTx-134
(1.95 g, 18.4mmol), and the resulting mixture which was
heated at 100°C for 22h and concentrated. Chromatography
of the crude residue with DCM/MeOH/28% aqueous
NH4OH (190:10:1) provided title compound (937.1 mg,
temperature for 72 h, and evaporated under reduced
pressure (the bath temperature from 60°C till 95°C). The
chromatography of the residue with CH2Cl2/MeOH/28%
1
aqueous NH4OH (240:10:1) gave 17 (1.35 g, 42.5%). H
1
78.5%). H NMR (DMSO-d6) (two conformational isomers
NMR (DMSO-d6) δ=1.34 (s, 9H), 1.68–1.72 (2H), 2.13–
2.24 (m, 2H), 2.74–2.90 (2H), 3.85 (s, 3H), 4.00–4.15
(2H), 4.24 (m, 1H), 7.37 (d, J= 5.6 Hz, 1H), 8.02 (2H),
8.34 (d, J=5.6Hz, 1H). 13C NMR (DMSO-d6) δ =28.1,
28.7, 43.0, 48.0, 54.3, 78.8, 111.2, 113.8, 118.2, 125.2,
142.8, 144.8, 149.6, 153.8, 162.4, 167.9, 172.3. MS (ESI):
1a and 1b) δ =1.68–1.81 (4H), 2.10 (m, 2H), 2.15 (s, 3H,
CH3), 2.28 (s, 3H, CH3), 2.73 (m, 2H), 2.99 (m, 2H), 3.07
(s, 3H, CH3), 3.31 (m, 2H), 3.55 (m, 1H), 3.70 (m, 1H),
3.93–4.07 (3H), 4.13 (m, 1H), 4.43 (s, 1H), 4.47 (s, 1H),
5.48 (d, J=6Hz, 0.5H, exchangeable H), 5.53 (d, J=6Hz,
0.5H, exchangeable H), 6.20 (d, J=7.6Hz, 0.5H), 6.21
(d, J= 7.6Hz, 0.5H), 6.77 (d, J=8.4Hz, 0.5H), 6.78
(d, J= 8.4Hz, 0.5H), 6.90 (d, J=8.4Hz, 0.5H), 6.91
(d, J= 8.4Hz, 0.5H), 6.92 (s, 0.5H), 6.94 (s, 0.5H), 7.30–
7.347 (1.5H), 7.68 (s, 0.5H), 7.80 (s, 0.5H), 7.95 (s, 0.5H),
11.11–11.18 (1H, exchangeable NH), 11.22–11.23 (1H,
exchangeable NH). 13C NMR (DMSO-d6) (two
conformational isomers) δ=15.92, 20.04, 29.66, 41.53,
45.53, 45.48, 45.54, 45.61, 48.63, 51.04, 51.11, 52.13,
67.73, 67.76, 69.55, 69.71, 91.40, 91.45, 94.53, 94.58,
105.96,, 110.67, 110.72, 111.21, 125.54, 125.61, 126.23,
126.36, 127.03, 128.84, 128.93, 131.11, 131.82, 134.50,
134.88, 134.91, 135.72, 135.80, 141.22, 144.26, 153.81,
154.33, 154.40, 156.58, 156.74, 162.27, 167.45, 167.49. MS
(ESI): m/z=649 [M +H+]. Anal. Calcd for C33H40N6O6S: C,
61.09; H, 6.21; N, 12.95, S 4.94; Found: C, 60.85; H, 6.17;
m/z= 512 [M+ H+].
2-(4-Chloro-2-oxo-1,2-dihydropyridin-3-yl)-6-(piperidin-4-
yl)imidazo[4,5-f]isoindole-5,7(1H,6H)-dione (10).
A mixture
of 2-methoxypiridine compound 17 (1.28g, 2.5mmol),
HCl in 1,4-dioxane (4.0M, 60mL) and H2O (0.5mL) was
heated at 70°C for 4.0h, and evaporated under
reduced pressure (the bath temperature< 60°C) to result
in a residual crude, which was azeotropically distilled
with 2-propanol under reduced pressure (the bath
temperature<98°C). The residue was diluted with a mixed
solvent of MeOH and DCM (1:4, v/v, 250mL), basified
with 28% aqueous NH3H2O (5mL), sonicated for 10min,
1
and evaporated to dryness to furnish crude product 10. H
NMR (DMSO-d6) δ=1.26–1.35 (2H), 1.74–1.80 (2H),
2.37–2.60 (2H), 2.90–2.94 (2H), 3.75 (m, 1H), 6.13 (d,
J=5.2Hz, 1H), 7.53 (s, J=5.2Hz, 1H), 7.62 (s, 1H), 7.85
(s). MS (ESI): m/z=398 [M+H+].
N, 12.87, S 4.85.
Preparation and NMR analysis of dihydrochloride salt of
tert-Butyl 4-(2-(4-chloro-2-oxo-1,2-dihydropyridin-3-yl)-
5,7-dioxoimidazo[4,5-f]isoindol-6(1H,5H,7H)-yl)piperidine-
1. To a solution of compound 1 (108.5 mg, 0.20mmol)
in a mixed solvent of MeOH and DCM (200 mL) (3:1,
v/v) was added a solution of HCl (1.0 M, 0.42 mL)
resulting a clean solution which was stirred for 5 min at
room temperature, and evaporated to provide 1· 2HCl
(144.4 mg, 100%). 1H NMR (DMSO-d6) δ =1.95–1.99
(2H), 2.10 (m, 2H), 2.17 (s, 3H, CH3), 2.20 (s, 3H,
CH3), 2.20–2.30 (2H), 3.14 (s, 3H, CH3), 3.17–3.26
(2H), 3.47–3.57 (3H), 3.60–3.72 (3H), 3.80–3.84 (2H),
3.95–4.05 (2H), 4.12 (m, 1H), 4.37 (m, 1H), 4.45 (s,
2H), 6.21 (d, J = 7.6 Hz, 1H), 6.82 (d, J = 8.4 Hz, 1H),
6.91 (d, J = 8.4 Hz, 1H), 6.96 (s, 1H), 7.35 (d,
J = 7.6 Hz, 1H), (1.5H), 7.60 (s, 1H), 7.85 (s, 1H),
10.93 (br, 1H, exchangeable NH), 10.93 (d, J = 6.0 Hz,
1H, exchangeable NH), 11.36 (br, 1H, exchangeable
NH). 13C NMR (DMSO-d6) δ = 15.9, 20.1, 26.8, 40.8,
45.4, 45.9, 46.0, 48.0, 48.6, 51.0, 67.7, 69.7, 90.7,
94.7, 108.1, 108.8, 111.2, 125.6, 126.7, 127.1, 128.9,
131.1, 134.8, 135.5, 136.7, 138.7, 152.6, 154.4, 157.0,
1-carboxylate (12).
To a solution of the crude
chloropyridone compound 10 in DCM (80mL) was added
Et3N (0.77mL, 557.2mg, 5.51mmol) at 0°C under N2,
followed by the addition of the solution of Boc2O
(820.0mg, 3.75mmol) in DCM (50mL). After the reaction
mixture was stirred at 0°C for 1h and at the room
temperature for 19h, MeOH (2.0mL) was added slowly
with at 0°C. The reaction mixture was then evaporated
under reduced pressure at 55°C (the bath temperature) to
afford
chromatography
a
crude residue which was subjected to
with DCM/MeOH/28% aqueous
NH3H2O (115:10:1) to afford 12 (1.03g, yield 83% for
1
two steps). H NMR (CDCl3) δ =1.47 (s, 9H), 1.70–1.74
(2H), 2.37–2.49 (2H), 2.75–2.83 (2H), 4.25–4.33 (3H),
6.49 (d, J=6.8Hz, 1H), 7.39 (d, J=6.8Hz, 1H), 8.21 (s,
1H), 8.58 (s, 1H). H NMR (DMSO-d6) δ=1.43 (s, 9H),
1
1.71–1.74 (2H), 2.12–2.22 (2H), 2.76–2.92 (2H), 4.00–
4.11 (2H), 4.25 (m, 1H), 6.57 (d, J=7.0Hz, 1H), 7.71 (d,
J=7.0Hz, 1H), 8.22 (s, 1H), 8.31 (s,1H). 13C NMR
(CDCl3) δ=28.4, 29.0, 43.8, 49.3, 79.7, 109.4, 111.4,
116.3, 123.0, 128.0, 128.7, 135.8, 136.7, 146.4, 146.8,
148.5, 148.8, 154.6, 162.9, 167.8. 13C NMR (DMSO-d6)
δ =28.0, 28.7, 43.5, 48.3, 78.8, 107.0, 109.8, 115.5, 122.0,
127.5, 128.1, 135.9, 137.6, 145.8, 146.6, 149.3, 153.8,
160.4, 167.1, 167.2. MS (ESI): m/z=498 [M+H+].
161.9, 167.4.
tert-Butyl 4-(2-(4-chloro-2-methoxypyridin-3-yl)-5,7-dioxoimidazo
[4,5-f]isoindol-6(1H,5H,7H)-yl)piperidine-1-carboxylate (17). To
a solution of 1,2-diamino compound 6 (2.23g, 6.20 mmol)
in MeOH (100 mL) was added 4-chloro-2-methoxynicotinic
aldehyde (7) (1.12g, 6.51mmol) and HOAc (5.0mL)
resulting in a mixture which was stirred at the room
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Y. A. Liu and V. E. Gregor
Vol 000
Preparation of 14 from 12. To a suspension of chloride 12
(747.0mg, 1.50mol) in EtOH (25mL) was added (R)-1-
amino-3-(2,4-dimethyl-phenoxy)-propan-2-ol (13) (439.3mg,
2.25 mmol) and Et3N (0.42 mL, 3.4.7 mg, 3.0 mmol)
resulting a mixture which was heated in a ChemGlass
pressure vessels at 100°C for 14 h and then concentrated.
The residues was subjected to chromatography with CH2Cl2/
MeOH/28% aqueous NH3H2O (150:10:1) to provide 14
with saturated NaCl solution, dried over MgSO4, and
concentrated to give a crude product 15, which was
heated together with methyl vinyl sulfone (2.0 g,
16.9 mmol) in a mixed solvent of EtOH (25 mL) and 2-
propanol (25 mL) at 100°C for 22 h. The reaction
mixture was concentrated to result in a crude residue,
which was subjected to chromatography (CH2Cl2
/MeOH/28% aqueous NH3H2O) (190:10:1) to afford 1
(1.15 g, 27.2%).
(711.3mg, 72%).
Scalable synthetic procedure of 1 from 3. To a mixture of
nitro compound 3 (2.54 g, 6.51 mmol) and 10% Pd/C
(254.0 mg) was added 2-propanol (5.0 mL), and then
MeOH (80.0 mL). After it was stirred under atmospheric
hydrogen for 18 h, the reaction mixture was diluted with
MeOH (40.0mL) and HOAc (5.0 mL), sonicated for
30min, and filtered over Celite. The filtrate was mixed
with aldehyde 7 (1.76 g, 6.69mmol), stirred at room
temperature for 72 h, and evaporated under reduced
pressure (the bath temperature from 60°C till 95°C) to
afford an oil which was mixed with 4.0M HCl
in1,4-dioxane (200.0 mL) and H2O (2.0 mL), heated at
70°C for 4.0h and evaporated under reduced pressure
(the bath temperature <60°C), and the residual crude was
azeotropically distilled with 2-propanol under reduced
pressure (the bath temperature < 98°C) and pumped at
25°C for 16h, affording 3.64 g crude product. To a
solution of the crude in DCM (100 mL) was added Et3N
(3.00 mL, 2.17g, 21.44 mmol) 0°C under N2, followed by
the addition of the solution of Boc2O (2.40g,
11.00mmol). After the reaction mixture was stirred at 0°C
for 1h and at the room temperature for 19h, MeOH
(5mL) was added slowly with at 0°C and then evaporated
under reduced pressure at 55°C (the bath temperature) to
afford a crude residue which was pumped for 16h. The
residue was then mixed with amine 13 (2.00g,
10.24mmol) and Et3N (1.20mL, 867.0mg, 8.57mmol) in
EtOH (50mL) resulting a mixture that was heated in a
ChemGlass pressure vessel at 100°C for 14h and then
concentrated to give a fluorescent crude product, which
was mixed with zinc dust (425.0mg, 65.0mmol) and
HOAc (50mL). After it was heated till refluxing (bath
temperature 120°C) for 2h, the reaction mixture was
cooled to room temperature, diluted with a mixed solvent
of MeOH (120mL) and DCM (20mL), and filtered. The
filtrate was concentrated at 70°C (the bath temperature)
under reduced pressure, and further dried azotroplically
with isopropanol. The resulting residue was dissolved in
a mixed solvent of DCM and MeOH (1:1, v/v, 200mL)
at room temperature, basified with aqueous NH3H2O
(28% in H2O, 50 mL) at 0°C, stirred for 30 min at room
temperature, and then poured into water (150 mL). The
aqueous phase was extracted with DCM (3 × 60 mL),
and then with 60 mL of mixed solvent DCM and MeOH
(4:1, v/v). The combined organic extracts were washed
REFERENCES AND NOTES
[1] Present address: Genomics Institute of the Novartis Research
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2015
Scalable Synthesis of GTx-134
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San Diego, CA, 92121); 4-Iodo-2-methoxy-1,2-dihydropyridine-3-
carbaldehyde (7), the lowest price in November, 2014: $65.8/mmol
($250/g) (Key Organics, Camelford, Cornwall, PL32 9RA, UK).
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet