A new efficient synthetic method for 3-iodothyronamine and its potent hypothermic efficacy

Article abstract of DOI:10.1002/cjoc.201180382

We developed a new efficient synthetic method for a 3-iodothyronamine (T₁AM) that has advantages of less synthetic steps and much higher overall yield compared to those in the conventional method. Our animal study showed that T₁AM synthesized by the method exerted a potent hypothermic effect in non-hibernator mice.

Full text of DOI:10.1002/cjoc.201180382

NOTE
A New Efficient Synthetic Method for 3-Iodothyronamine and
Its Potent Hypothermic Efficacy
Kim, Joong-Gona
Song, Young-Kyub
Choi, Inho*,c
Jeon, Su-Yeonb
Lim, Ye-Jib
Ju, Hyunwooc
Chung, Chan-Moon*,b
a Biotechnology Division, Hanwha Chemical R&D Center, Daejeon 305-345, Korea
b Department of Chemistry and Medical Chemistry, Yonsei University, Wonju, Gangwon-do 220-710, Korea
c Department of Biological Science and Technology, Yonsei University, Wonju, Gangwon-do 220-710, Korea
We developed a new efficient synthetic method for a 3-iodothyronamine (T1AM) that has advantages of less
synthetic steps and much higher overall yield compared to those in the conventional method. Our animal study
showed that T1AM synthesized by the method exerted a potent hypothermic effect in non-hibernator mice.
Keywords 3-iodothyronamine, hibernation-like state, ICR mouse
Introduction
to synthesize the compound in a more efficient manner
for a broad range of the possible medical applications.
Herein, we describe a new efficient synthetic method for
T1AM (10) having reduced synthetic steps and signifi-
cantly enhanced overall yield. Hypothermic efficacy of
the compound was also studied using laboratory mice.
As illustrated in Scheme 1, our new method employs
4-chloro-3-nitrobenzyl alcohol (1), 1-chloro-4-methyl-2-
nitrobenzene (2), or 2-(4-chlorophenyl)acetonitrile (3) as
starting materials. 2-(4-Chloro-3-nitrophenyl)acetonitrile
(4) could be prepared by four synthetic routes. First, 4
was synthesized via 4-chloro-2-nitrobenzyl chloride
intermediate that formed by treating 1 with aqueous HCl.
The intermediate then afforded 4 by reaction with NaCN
in the presence of a catalytic amount of NaI. Second, 4
was also synthesized via 4-chloro-2-nitrobenzyl bro-
mide intermediate that was formed by reaction of 1 with
CBr4. Third, 4 could also be synthesized by benzyl bro-
mination of 2 using N-bromosuccinimide (NBS) and
benzoyl peroxide (BPO) followed by substitution of
bromide with cyanide.8 Fourth, regioselective mono
nitration of 3 directly gave 4 in 74% yield.
Mammalian hibernation has been considered as a
fascinating physiological trait that enables them to
overcome harsh conditions (e.g., coldness and food
shortage).1 Hibernators actively suppress metabolism
and body temperature (Tb) and survive for four to six
months of winter without feeding. Because of the hy-
pometabolic and hypothermic features, hibernation
mechanism is considered to offer significant medical
benefits in emergency medical care, organ transplanta-
tion, and extended spaceflights.2
Metabolic rate and Tb are principally controlled by
thyroid hormones (TH) such as triiodothyronine (T3)
and thyroxine (T4). Since these hormones are ther-
mogenic, their levels in blood circulation are found to
increase in winter.3 Induction of hibernation is the op-
posite of the TH effect. Until recently, however, little
was known about a molecular mechanism underlying
the hibernation triggering process. One clue might be
seen from the action of 3-iodothyronamine (T1AM, 10),
a natural derivative of T4.4,5 When a single-dose was
injected to laboratory mice, it induced rapid hypome-
tabolism and hypothermia, with peak effect in 1— 2 h.
The Tb was then recovered gradually in about 6 h after
injection.
As shown in Scheme 2, the coupling reaction of 4
with 4-methoxyphenol (5) was performed to obtain 6 in
the presence of NaH.9,10 In the conventional method,6,7
the coupling reaction of N-t-Boc-3-iodotyramine with
4-(triisopropyl)silyloxyphenylboronic acid gave N-t-
Boc-4'-triisopropylsilyloxy-3-iodothyronamine in a low
yield (36%). Compared to this, a high yield (89%) was
achieved under our coupling reaction condition.
The first synthesis of T1AM (10) was reported by
Scanlan et al. who developed a seven-step synthetic
process.6,7 The method involves the synthesis of N-t-
Boc-3-iodotyramine from tyramine and 4-(triisopropyl)-
silyloxyphenylboronic acid from p-bromophenol, cou-
pling of the two compounds, and removal of the pro-
tecting groups. However, the overall yield of the con-
ventional method was fairly low (3%), so it is necessary
7 was prepared from 6 in 88% yield via diazotization
followed by iodination of corresponding aniline.11,12 In
contrast, the conventional iodination method6,7 had
*
E-mail: cmchung@yonsei.ac.kr(C.-M. Chung), ichoi@yonsei.ac.kr(I. Choi); Tel.: ＋82 337602266; Fax: ＋82 337602182
Received March 10, 2011; revised June 17, 2011; accepted June 29, 2011.
Project supported by the National Space Lab program through the Korea Research Foundation and funded by the Ministry of Education, Science and
Technology (No. 2010-0015086) awarded to I. Choi.
Chin. J. Chem. 2011, 29, 2205— 2208
© 2011 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Kim et al.
NOTE
Scheme 1 Synthesis of 4
Reagents and conditions: (a) 35% HCl, r.t., 2 h, then NaCN, NaI, anhy acetone, reflux, 12 h, 83%; (b) CBr4, TPP, CH2Cl2, 0 ℃ to r.t., 2 h,
then NaCN, NaI, anhy acetone, reflux, 12 h, 73%; (c) NBS, dibenzoylperoxide, chlorobenzene, reflux, overnight, then NaCN, NaI, anhy ace-
tone, reflux, 12 h, 62%; (d) fuming HNO3, 95—100 ℃, 2.5 h, 74%.
Scheme 2 Synthesis of T1AM (10)
Reagents and conditions: (a) NaH, DMF, r.t., 2 h, 89%; (b) Pd/C, H2, EA, r.t., 6 h, then NaNO2, H2SO4, 0—5 ℃, 30 min, then KI, H2O, r.t.,
1
overnight, 88%; (c) BBr3, CH2Cl2, －78 ℃ to r.t., 15 h, 89%; (d) (Boc)2O, NiCl2, NaBH4, anhy MeOH, 0 ℃ to r.t., 1.5 h, 84%; (e) 2 mol•L－
HCl/EA, r.t., overnight, 92%.
some problems such as a very low yield (19%) and dif-
ficulty in purification due to the formation of a consid-
erable amount of N-t-Boc-3,5-diiodotyramine byproduct.
In this work the preparation of iodo compound 7 proceeds
regioselectively because nitro group is replaced with
iodine. 8 was obtained by demethylation of 7 using BBr3,
and 9 was synthesized by catalytic reduction of the
cyano group and subsequent Boc protection of 8.13
T1AM (10)14 was prepared by Boc deprotection of 9
gradually recovered for the following hours. It is worth
－
1
recognizing that the treated subjects (50 mg•kg ) were
unable to escape from an extremely low Tb condition,
although a sort of brief spasm was noticed at Tb of about
15 ℃ (Figure 1C). This indicates that the hibernation-
like state of mice is fundamentally different from deep
torpor of true hibernators. In the latter case, like squir-
rels and bats, Tb can decrease down to near 0 ℃.1 Nota-
bly, the hypothermic effect was additive within a limited
low range, because the Tb decreased by the first injec-
1
with HCl, and its H and 13C NMR spectra are in good
－
agreement with those previously reported.7
tion (50 mg•kg ) was further lowered by the second
treatment of the same dosage (Figure 1D). At this Ta
level, the treated subjects were likely to keep Tb at ＞28
℃ (Figures 1B and 1D) and even by a doubled dosage
(100 mg•kg－ 1).4 Together, these results imply that
non-hibernator mammals may remain torpid for an ex-
tended period at a certain Tb (e.g., 30 ℃) by repeated
administration of the compound.
1
Next, to investigate the hypothermic efficacy of
T1AM (10) synthesized in this work, it was treated to
laboratory mice.15 As shown in Figure 1A, the control
mouse maintained Tb in a range of 36.4—37.3 ℃. This
thermoregulatory activity was contrasted by the obser-
vation that Tb was immediately decreased in the
T1AM-injected subjects (Figure 1B). The extent of the
change was dose-dependent,4 with the lowest Tb of 32.2
In conclusion, a new efficient synthetic method was
developed for T1AM (10). Our synthetic method has
advantages of less synthetic steps and much higher
℃ by 25 mg•kg－ and 28.7 ℃ by 50 mg•kg－ at an
1
1
ambient temperature (Ta) of 23 ℃. The Tb was then
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© 2011 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2011, 29, 2205— 2208

A New Efficient Synthetic Method for 3-Iodothyronamine and Its Potent Hypothermic Efficacy
Figure 1 Tb traces of ICR male mice after vehicle (A) or T1AM injection (B—D). Note that ambient temperature (Ta) was (23±0.5) ℃
for A, B and D, and (5±1.0) ℃ for C. (A) The control mouse displayed constant Tb (ca. 37 ℃), whereas (B) the subjects showed
－
－
1
1
dose-dependent hypothermic responses to either 25 or 50 mg•kg . (C) At Ta of 5 ℃, the treated mouse (50 mg•kg ) succumbed to
death at Tb below 9 ℃. The horizontal arrow indicates the Tb point (ca. 15 ℃) at which a brief spasm was observed. (D) T1AM treatment
－
1
exerted an additive effect as Tb at the rising phase following the first treatment (50 mg•kg ) was further decreased by the second trial of
the same dosage. i.p.: intraperitoneal; s. c.: subcutaneous.
overall yields (33%—45%) compared to those in the
conventional method (7-step process, 3% overall
yield6,7). T1AM (10) synthesized by this new method
showed a potent hypothermic effect. Because of these
hypometabolic and hypothermic efficacies, it is ex-
pected that T1AM has possible pharmaceutical merits
for emergency medical care, organ transplantation,
long-term space mission, as well as remedies for diabe-
tes and extended life span.2,16,17
J. Org. Chem. 1998, 877.
10 Theil, F. Angew. Chem., Int. Ed. 1999, 38, 2345.
11 In, J.-K.; Lee, M.-S.; Yang, J.-E.; Kwak, J.-H.; Lee, H.;
Boovanahalli, S. K.; Lee, K.; Kim, S. J.; Moon, S. K.; Lee,
S.; Choi, N, S.; Ahn, S. K.; Jung, J.-K. Bioorg. Med. Chem.
Lett. 2007, 17, 1799.
12 Xiang, Y.; Caron, P.-Y.; Lillie, B. M.; Vaidyanathan, R.
Org. Process Res. Dev. 2008, 12, 116.
13 Caddick, S.; Judd, D. B.; Lewis, A. K. K.; Reich, M. T.;
Williams, M. R. V. Tetrahedron 2003, 59, 5417.
14 m. p. 214—215 ℃; 1H NMR (DMSO-d6, 400 MHz) δ: 9.36
(s, 1H), 7.77 (s, 1H), 7.74 (brs, 3H), 7.23—7.20 (m, 1H),
6.82—6.76 (m, 4H), 6.71 (d, J＝8.4 Hz, 1H), 3.03 (t, J＝7.6
Hz, 2H), 2.80 (t, J＝7.6 Hz, 2H); 13C NMR (DMSO-d6, 100
MHz) δ: 155.9, 153.8, 148.1, 139.3, 133.9, 130.2, 119.9,
117.5, 116.2, 88.3, 38.8, 31.5; IR (KBr) ν: 3383, 3120, 3017,
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－
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4
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15 Animal experiment. To examine efficacy of the synthesized
T1AM (10), Tb of individual mice was monitored for 6 h af-
ter a single injection. Institute of Cancer Research (ICR)
male mice at ten weeks of age (ca. 35 g) were purchased
from a local supplier and housed at (23±0.5) ℃ in a 12
h∶12 h light-dark cycle with the light on at 06: 00. Mice
had ad libitum access to standard Purina chow and water.
5
6
Each mouse was injected intraperitoneally with 25 or 50
mg•kg －
T1AM dissolved in 60% dimethyl sulfoxide
1
7
Scanlan, T. S.; Hart, M. E.; Grandy, D. K.; Bunzow, J. R.
US 6979750, 2005.
(DMSO) and 40% saline (pH 7.4), or vehicle (60% DMSO
and 40% saline) for the control.4 Tb of the subjects was con-
tinuously recorded with a 0.025 mm diameter duplex cop-
8
9
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Chin. J. Chem. 2011, 29, 2205— 2208
© 2011 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
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Kim et al.
NOTE
per-constantan thermocouple (California Fine Wire, Grover
arouse as their Tb decreased to an extremely low level. The
experimental procedure of the study was approved by the
Yonsei University Animal Care and Use Committee.
City, CA) and an Omega 91100—20 thermocouple ther-
mometer (Cole-Palmer Instrument, Vernon Hills, IL). The
sensing tip of the thermocouple was inserted ca. 7 mm into
the pectoral muscle. In another set of experiment, a couple
16 Don, C. W.; Longstreth, W. T. Jr.; Maynard, C.; Olsufka,
M., Nichol, G.; Ray, T.; Kupchik, N.; Deem, S.; Copass, M.
K.; Cobb, L. A.; Kim, F. Crit. Care Med. 2009, 37, 3062.
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of mice (treated with 50 mg•kg－ T1AM) were examined at
1
Ta of (5±1.0) ℃ to test whether they were able to alert and
(E1103105 Cheng, F.; Zheng, G.)
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Chin. J. Chem. 2011, 29, 2205— 2208