Structural determinants of selective thyromimetics

Article abstract of DOI:10.1021/jm0301181

The thyromimetic GC-1 shows a preference for binding the β form of the thyroid hormone receptor (TR). GC-1 was designed as an analogue of the thyromimetic DIMIT, which has a lower affinity for TR and is not selective. GC-1 has a methylene group linking it

Full text of DOI:10.1021/jm0301181

3152
J . Med. Chem. 2003, 46, 3152-3161
Str u ctu r a l Deter m in a n ts of Selective Th yr om im etics
Hikari A. I. Yoshihara,† J ames W. Apriletti,‡ J ohn D. Baxter,‡ and Thomas S. Scanlan*,†
Departments of Pharmaceutical Chemistry and Cellular & Molecular Pharmacology, University of California,
San Francisco, California 94143-2280, and Metabolic Research Unit, University of California,
San Francisco, California 94143-0540
Received March 12, 2003
The thyromimetic GC-1 shows a preference for binding the â form of the thyroid hormone
receptor (TR). GC-1 was designed as an analogue of the thyromimetic DIMIT, which has a
lower affinity for TR and is not selective. GC-1 has a methylene group linking its two aromatic
rings and an oxyacetic acid polar side chain, while DIMIT has an ether oxygen linking its
aromatic rings and an L-alanine polar side chain. The structural features of GC-1 that confer
its greater affinity and selectivity compared to DIMIT were analyzed with the preparation of
analogues that bear only one of their two different structural features. The analogue of GC-1
with a biaryl ether has selectivity comparable to that of GC-1, while the analogue of DIMIT
with a methylene group linking its aromatic rings is only slightly selective. These results
demonstrate that the oxyacetic acid side chain of GC-1 is critical in conferring TR-â selectivity.
In tr od u ction
Thyroid hormone is a classical endocrine hormone
that plays important roles in the development and
regulation of homeostasis.1 Thyroxine (T4, 2, Figure 1)
is the major secreted form that is enzymatically de-
iodinated in peripheral tissues to the more active form
3,5,3′-triiodo-L-thyronine (T3, 1, Figure 1). Most of
thyroid hormone’s actions are believed to be mediated
through nuclear thyroid hormone receptors (TRs) that
regulate transcription of target genes either positively
or negatively in response to hormone binding.2 The two
genes for TR (TRR and TRâ) are each expressed in most
tissues in two alternatively spliced variants: TRR1 and
TRR2; TRâ1 and TRâ2.3 All these forms of the receptor
except TRR2 are activated by T3, which binds the ligand
binding domain (LBD) of the receptor with high affinity.
While TRR and TRâ are widely expressed, they have
distinct patterns of expression.3 Mice deficient in either
TRR or TRâ show different phenotypes,4-8 suggesting
that each receptor isoform has significantly different
regulatory roles.
T3 binds both TRR1 and TRâ1 with near-equal affin-
ity.9 Synthetic ligands that bind preferentially to only
one isoform could be powerful tools for studying each
isoform’s physiological roles. T3 is a potent serum
cholesterol lowering agent;10-12 however, its therapeutic
use in treating hypercholesterolemia is prevented by
various side effects. Tachycardia, increased cardiac
output, and the increased risk of cardiac arrhythmia13,14
are the most serious side effects that arise from an
excess of T3. Mice deficient in TRR1 have a 20% lower
heart rate than wild-type mice, and this does not
increase to wild-type levels with T3 treatment.15 TRâ is
the predominant isoform expressed in the liver,16 and
upon T3 treatment, mice deficient in TRâ do not up-
F igu r e 1. Structures of thyroid hormones and thyromimetics.
regulate CYP7A, the rate-limiting enzyme for the
conversion of cholesterol to bile acids.17 These results
suggest that TRâ-selective thyromimetics with the
expected tissue-selective action could function as useful
therapeutic agents.
A number of thyromimetics have been reported in
recent years to have tissue-selective action. Among these
compounds are CGS 2342518 (5, Figure 1), CGS 2621419
(6, Figure 1), and GC-19,20 (4, Figure 1). CGS 23425 has
* To whom correspondence should be addressed. Phone: (415) 476-
3620. Fax: (415) 502-7220. E-mail: scanlan@cgl.ucsf.edu.
† Departments of Pharmaceutical Chemistry and Cellular & Mo-
lecular Pharmacology.
‡ Metabolic Research Unit.
10.1021/jm0301181 CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/29/2003

Thyromimetics
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14 3153
a structure resembling the nonselective thyromimetic
3,5-dimethyl-3′-isopropyl-L-thyronine21 (DIMIT, 3, Fig-
ure 1) but with an oxamic acid polar side chain replacing
DIMIT’s alanine side chain. In hypercholesterolemic
rats, CGS 23425 lowers low-density lipoprotein choles-
terol by 44% without inducing cardiotoxic effects,18
demonstrating that the compound is a liver-selective,
cardiac-sparing thyromimetic. The selective action of
CGS 23425 has been attributed to the preferential
activation of TRâ over TRR. In assays of TR-mediated
transcription activation from a rat apoAI promoter in
HuH-7 cells, CGS 23425 has EC50 values of 0.002 nM
for hTRâ1 and 0.1 nM for hTRR1, a 50-fold preference
for activation of TRâ over TRR in this system.18 It has
not been reported whether this difference in potency for
the TR isoforms reflects differences in affinity.
F igu r e 2. Structures of target compounds to study effects of
CGS 26214 resembles CGS 23425 structurally but has
a 4-fluorophenylhydroxymethyl substituent at the 5′
position. When tested in rats and dogs, CGS 26214 is a
potent serum cholesterol lowering agent free of cardio-
vascular effects. In nuclear binding assays using intact
neonatal rat cardiac myocytes, CGS 26214 has an
apparent 100-fold lower affinity than T3, while the
affinities of the ligands are comparable when the assay
is performed using cultured liver (HepG2) cells.19 These
results suggest that the tissue-selective thyromimetic
effects of CGS 26214 may be due to preferential TR
binding in the liver.
methylene bridge and oxyacetic acid side chain on TR selectiv-
ity.
TRâ Asn331Ser has reduced affinity for GC-1 while TRR
Ser277Asn has increased affinity.28
When the structures of T3, DIMIT, GC-1, CGS 23425,
and CGS 26214 are compared, a correlation emerges
between selective action and the identity of the polar
side chain. DIMIT and T3 have an alanine polar side
chain and are not selective, while the TR ligands with
oxyacetic or oxamic acid side chains have selective
action in vivo. For GC-1, this selective action correlates
with its preferential binding to TRâ.
The thyromimetic GC-1 was developed in our labora-
tory and binds hTRâ1 with an affinity comparable to T3
but binds hTRR1 with a 10-fold lower affinity.9 This 10-
fold selectivity and ability to preferentially activate TRâ
is reflected in several in vivo studies where it exhibits
a distinct subset of physiological responses to T3 in such
TR-mediated processes as tadpole metamorphosis,22
lipid metabolism,23 cerebellar development,24 and adap-
tive thermogenesis.25 The structural features of GC-1
that confer its TRâ selectivity are not well defined. GC-1
was designed as a synthetically accessible thyromimetic
that would serve as a platform for the development of
TR antagonists. Its design was based on DIMIT, which
binds TR with approximately 100-fold lower affinity
than T3.9,26 For ease of synthesis, GC-1 was designed
with a methylene group joining the two aromatic rings,
instead of the ether oxygen of DIMIT and T3. The
R-amino group of T3 is not required for high affinity
binding to TR,26 and the oxyacetic acid polar side chain
was intended as a readily synthesized isostere of pro-
pionic acid. Comparing the structures and activities of
GC-1 and DIMIT, one concludes that the structural
changes introduced by the methylene bridge or oxyacetic
acid side chain are responsible for the GC-1’s higher
affinity and selectivity.
Seeking to understand better the specific roles of GC-
1’s methylene bridge and oxyacetic acid side chain in
its TRâ selectivity, we synthesized analogues of GC-1
and DIMIT bearing only one of the two different
structural features. By comparison of the binding af-
finities and selectivities of methylene-bridged DIMIT (8,
Figure 2) and GC-1 ether (7, Figure 2) to those of DIMIT
and GC-1, the effects of the ether to methylene and the
alanine to oxyacetic acid substitutions can be evaluated
individually. The methylene-bridged analogue of T3 has
a 2.5-fold higher affinity for TR than T3; however, this
result was from a binding assay based on a nuclear
extract, making it difficult to evaluate isoform-selective
binding.26 Additionally, the propionic acid side chain
analogue of GC-1 (9, Figure 2) was prepared to assess
the effect of the ether oxygen in the polar side chain of
GC-1. To ensure the most valid comparisons between
thyromimetic ligands, i.e., those with small perturba-
tions, the study was limited to GC-1, DIMIT, and their
related analogues.
Resu lts
Syn th esis of GC-1 Eth er . The synthesis of the biaryl
ether analogue of GC-1 was achieved in seven linear
steps starting from 2-isopropylphenol and 2,6-dimeth-
ylhydroquinone. The key step for joining the two aro-
matic rings in a biaryl ether linkage from arylboronic
acid and phenolic intermediates was achieved using the
copper(II) catalyzed coupling reaction developed by
Evans29 (Scheme 1). 4-Benzyloxy-2,6-dimethylphenol
(13) was prepared in low yield from the alkylation of
2,6-dimethylhydroquinone by a Williamson ether syn-
thesis. The site of alkylation was assigned on the basis
of 1H NMR chemical shift perturbations of the 3,5-
protons and the 2,6-methyl protons compared to the
Crystallographic studies have shown that only one
amino acid residue (Ser277 in hTRR1, Asn331 in hTRâ1)
is different in the ligand binding cavity of the two
receptors.4,27 This residue does not directly contact the
ligand, but a comparison of the cocrystal structures of
TRâ-LBD with GC-1 bound and with T3 bound shows
that Asn331 participates in a hydrogen bonding network
with neighboring arginine residues that is arranged
differently depending on the ligand present.28 The role
of Asn331/Ser277 in GC-1’s TRâ selectivity has been
confirmed with mutagenesis experiments showing that

3154 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14
Yoshihara et al.
Sch em e 1. Preparation of the Ether-Bridged Analogue
group protecting the 4′-hydroxyl was unexpectedly
cleaved under saponification conditions, providing 7, the
biaryl ether analogue of GC-1.
of GC-1a
Syn th esis of Meth ylen e-Br id ged L-DIMIT. The
synthesis of the methylene-bridged analogue of L-DIMIT
was achieved in 14 linear steps starting from 4-bromo-
2-isopropylphenoland4-bromo-3,5-dimethylphenol(Scheme
2). The synthesis of the biphenylmethane scaffold
employed the same strategy used to make GC-1,9,20 with
the coupling of the aromatic rings effected by the 1,2-
addition of an aryllithium intermediate to a benzalde-
hyde intermediate. The hydroxyl of 4-bromo-3,5-dime-
thylphenol was protected as a benzyl ether, which was
removed during the catalytic hydrogenolysis of the
hydroxyl on the bridging carbon of 18. The L-alanine
side chain was synthesized from a propionic acid side
chain containing intermediate, using Evans’s chiral
auxiliary.
4-Benzyloxy-2,6-dimethylbromobenzene was prepared
by reaction of 4-bromo-3,5-dimethylphenol (15) with
benzyl bromide and potassium carbonate in DMF. The
benzaldehyde 16 was prepared in the usual fashion by
treatment first with n-butyllithium and then DMF as
a formylating reagent, followed by an aqueous acid
workup. The coupling of the rings by the addition of the
aryllithium reagent, derived from bromobenzene 17 and
n-butyllithium, to benzaldehyde 16 proceeded in good
yield. Catalytic hydrogenation of 18 yielded a phenolic
biarylmethane intermediate, which was reacted with
trifluoromethanesulfonic anhydride to produce the aryl-
trifluoromethanesulfonate (aryltriflate) 19 in high yield.
When a Stille coupling with vinyltributylstannane was
used, aryltriflate 19 was converted to a styrene inter-
mediate, which was cleaved to the benzaldehyde 20 via
ozonolysis and reduction using triphenylphosphine.
a
Reagents and conditions: (a) (i) n-BuLi, THF, -78 °C, (ii)
B(OMe)3, THF, -78 °C to room temp, (iii) H3O+; (b) BnBr, K2CO3,
DMF, 9%; (c) Cu(OAc)2 Et3N, CH2Cl2; (d) H2, Pd/C, EtOAc, 27%
from 13; (e) methyl bromoacetate, Cs2CO3, DMF, 81%; (f) LiOH,
H2O, MeOH, 30%.
corresponding chemical shifts in the starting material
and the other alkylated products.
The arylboronic acid intermediate 11 for the coupling
reaction was prepared from the para bromination of
2-isopropylphenol, followed by the protection of the
phenol as a methoxymethyl (MOM) ether. The aryl
bromide, 10,20 was converted to the arylboronic acid
with the sequential addition of n-butyllithium and
trimethylborate, followed by hydrolysis with aqueous
HCl. The coupling of 11 and 13 was effected with
copper(II) acetate and triethylamine as the base. The
oxyacetic acid polar side chain was installed by depro-
tection of the 1-hydroxyl of 14 with catalytic hydrogena-
tion, alkylation with methyl bromoacetate, and hydrol-
ysis of the ester with lithium hydroxide. The MOM
The propionic acid side chain was built from the benz-
aldehyde by a Wittig olefination with benzyl (triphen-
ylphosphoranylidene)acetate, followed by catalytic hy-
drogenation to reduce the acrylate ester to propionate
and hydrogenolyze the benzyl ester. To install the chiral
auxiliary (S)-4-benzyl-2-oxazolidinone, a mixed anhy-
Sch em e 2. Preparation of the Methylene-Bridged Analogue of DIMITa
a
Reagents and conditions: (a) BnBr, K2CO3, DMF, 78%; (b) (i) 1.1 equiv of n-BuLi, THF, -78 °C, (ii) DMF, THF, -78 °C, (iii) H3O+,
80%; (c) (i) 1.1 equiv of n-BuLi, THF, -78 °C, (ii) 16, THF, -78 °C, 77%; (d) H2, Pd/C, EtOH/AcOH, 100%; (e) Tf2O, pyr, DCM, 99%; (f)
vinyl-SnBu3, Cl2Pd(PPh3)2, LiCl, DMF, 85%; (g) (i) O3, CH2Cl2, -78 °C, (ii) PPh3, -78 °C to room temp, 86%; (h) benzyl (triphenylphos-
phoranylidene)acetate, THF, 100%; (i) H2, Pd/C, EtOAc, 86%; (j) (i) pivaloyl-Cl, Et3N, THF, (ii) lithium (S)-(-)-4-benzyl-2-oxazolidinone,
THF, -78 °C, 89%; (k) (i) KHMDS, THF, -78 °C, (ii) trisylazide, THF, -78 °C, (iii) AcOH, 73%; (l) LiOOH, 3:1 THF/H2O, 83%; (m) 100
equiv Et3N‚3HF, THF, 44%; (n) H2, Pd/C, 2:1 AcOH/H2O, 95%.

Thyromimetics
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14 3155
Ta ble 1. Binding Affinities of Thyromimetics for TR
Kd(hTRR1)
Kd(hTRâ1)
∆Gbind(hTRR1)
(kcal/mol)
∆Gbind(hTRâ1)
(kcal/mol)
compd
(nM)
(nM)
selectivity
T3 (1)
GC-1 (4)
0.060 ( 0.004
0.66 ( 0.05
2.4 ( 0.4
0.69 ( 0.05
2.02 ( 0.09
8.5 ( 0.8
0.087 ( 0.006
0.10 ( 0.01
0.36 ( 0.01
0.22 ( 0.01
1.26 ( 0.03
6.2 ( 0.2
1.0 ( 0.2
10 ( 2
-12.96 ( 0.04
-11.64 ( 0.05
-10.94 ( 0.08
-11.61 ( 0.04
-11.03 ( 0.03
-10.24 ( 0.05
-12.76 ( 0.04
-12.71 ( 0.06
-11.98 ( 0.02
-12.24 ( 0.04
-11.29 ( 0.01
-10.41 ( 0.02
ether-bridged GC-1 (7)a
propionic acid GC-1 (9)a
methylene-bridged DIMIT (8)a
DIMIT (3)
10 ( 2
4.5 ( 0.6
2.3 ( 0.3
2.0 ( 0.3
a
Compound purity >97% by HPLC.
F igu r e 3. Ether oxygen to methylene and alanine to oxyacetic acid side chain substitutions have distinct independent effects on
TR affinity and selectivity. Values indicate fold gain in affinity for TRR and TRâ.
Sch em e 3. Preparation of the Propionic Acid Side
ether for TRR1 and TRâ1 are summarized in Table 1.
To ensure a valid comparison of the affinities of different
ligands, all the compounds were assayed simultaneously
using the same preparation of purified TR. The selectiv-
ity was determined by the ratio of Kd(hTRR1) to Kd-
(hTRâ1) and normalized to the ratio of Kd(hTRR1) to
Kd(hTRâ1) for T3.
Chain Analogue of GC-1a
While none of the synthetic thyromimetics, except for
GC-1, bind to hTRâ1 as tightly as T3, the thyromimetics
containing the methylene bridge (GC-1, methylene-
bridged DIMIT, and propionic acid GC-1) bind with
greater affinities than those containing the ether bridge.
The ether to methylene substitution thus results in
increased affinity for TR with thyromimetics of the 3,5-
dimethyl-3′-isopropyl substitution pattern, as it does
with the 3,5,3′-triiodo substitution pattern of T3. Com-
paring the affinities and selectivities of DIMIT and T3
shows that 3,5-dimethyl-3′-isopropyl substitution results
in an approximate loss of affinity of 140-fold for hTRR
and 70-fold for hTRâ, resulting in a 2-fold gain in TRâ
selectivity.
a
Reagents and conditions: (a) benzyl (triphenylphosphora-
nylidene)acetate, THF, 100%; (b) 100 equiv of Et3N‚3HF, THF,
88%; (c) H2, Pd/C, 2:1 AcOH/H2O, 90%.
dride was generated from the propionic acid intermedi-
ate and pivaloyl chloride, which was reacted with the
lithium salt of (S)-4-benzyl-2-oxazolidinone. The chiral
N-acyloxazolidinone was deprotonated with potassium
bis(trimethylsilyl)amide and quickly reacted with 2,4,6-
triisopropylbenzenesulfonylazide, followed rapidly by an
acetic acid quench to give the single diastereomer (by
1H and 13C NMR) of the N-(R-azidoacyl)oxazolidinone
21. The chiral auxiliary was removed with lithium
peroxide followed by deprotection of the TIPS ether with
triethylamine trihydrofluoride. Finally, the R-azide was
reduced to the R-amine with catalytic hydrogenation to
yield the methylene-bridged analogue of L-DIMIT (8).
To analyze the role of the bridging moiety and polar
side chain in influencing TRR/TRâ selectivity, pairwise
comparisons were made among GC-1, DIMIT, methyl-
ene-bridged DIMIT, and ether-bridged GC-1. As shown
in Figure 3, the ether to methylene substitution results
in the same change in affinity for TRR and TRâ.
Methylene-bridged DIMIT shows (4.2 ( 0.5)-fold and
(4.9 ( 0.2)-fold increases in affinity for TRR and TRâ,
respectively, compared to DIMIT, while GC-1 cor-
respondingly has (3.6 ( 0.6)-fold and (3.8 ( 0.4)-fold
greater affinities than ether-bridge GC-1. Thus, the
ether to methylene substitution has little effect on
selectivity.
Syn th esis of P r op ion ic Acid Sid e Ch a in An a -
logu e of GC-1. The GC-1 analogue with a propionic
acid polar side chain (9, Scheme 3) was prepared from
the benzaldehyde intermediate (20, Scheme 2) from the
synthesis of methylene-bridged DIMIT. The TIPS pro-
tecting group was removed using the standard proce-
dure, and the product was hydrogenated to generate the
propionic acid side chain.
The gains in affinity for ether-bridged GC-1 compared
to DIMIT ((3.6 ( 0.6)-fold for TRR and (17 ( 1)-fold for
TRâ) and correspondingly for GC-1 compared to meth-
TR Bin d in g. The affinities and selectivities of T3,
DIMIT, GC-1, methylene-bridged DIMIT, and GC-1

3156 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14
Yoshihara et al.
∆∆∆Gbind. Inspection of the ratios of affinities in Figure
3 shows the independent effects of the structural
changes on affinity. The ether bridge to methylene
substitution has practically the same effect on binding
affinity regardless of the identity of the polar side chain.
Similarly, the side chain substitutions have almost the
same effect on affinity and selectivity within the context
of either bridging moiety.
Discu ssion
The preceding results clearly demonstrate that the
TRâ selectivity of GC-1 is determined by its oxyacetic
acid side chain. In a comparison of the GC-1 analogues
with alanine and propionic acid side chains, it is also
apparent that both the loss of the R-amine and the
methylene to ether substitution make significant con-
tributions to differentially increase the affinity for TRâ.
That the polar side chain substitution has the same
effect on binding and selectivity in the context of either
bridging moiety strongly implies that the side chain and
the adjacent aromatic ring (A-ring) interact with the
receptors in the same fashion regardless of bridging
moiety. Accordingly, the small shift in the relative
positions of the A-ring and B-ring caused by the longer
carbon-carbon bonds of the methylene bridge (1.54
versus 1.39 Å for C-O) would be borne out by the B-ring
with the A-ring remaining in the same position relative
to the receptor.
Because the improvement in affinity observed with
the introduction of the methylene bridge is nearly equal
for both receptors in the context of either side chain, it
is possible that a factor external to the interaction of
ligand with receptor is mostly responsible for the
increased affinity. One such factor could be the in-
creased hydrophobicity of the ligands containing the
methylene bridge. Increased hydrophobicity of a ligand
increases the free energy in the unbound state by
increasing the energetic cost of solvation and results in
a greater free energy of binding and higher affinity. This
effect may not be functioning in this case because
diphenylmethane has a reported log P value of 4.14
while the corresponding value for diphenyl ether is
4.21,30 suggesting that a significant increase in hydro-
phobicity does not occur with the methylene for oxygen
substitution. Alternatively, the methylene bridge may
cause the B-ring to interact with the receptor in a more
energetically favorable fashion to cause the observed 3-
F igu r e 4. Loss of the R-amino group and the side chain ether
for methylene substitution both contribute toward TRâ selec-
tivity. Values indicate fold gain in affinity for TRR and TRâ.
ylene-bridged DIMIT ((3.1( 0.3)-fold for TRR and (13
( 2)-fold for TRâ) show a strong differential gain in
affinity for TRâ associated with the alanine to oxyacetic
acid polar side chain substitution. In comparison with
the results of the ether to methylene substitution, these
data clearly demonstrate the key role of the oxyacetic
acid side chain in GC-1’s preferential binding to TRâ.
The change of alanine side chain to oxyacetic acid can
be thought of as occurring in two steps: first, the
replacement of the R-amine with hydrogen and, second,
the ether replacement of the side chain methylene. To
determine the role of these specific structural changes
in influencing affinity and selectivity, the preceding
analysis was repeated with methylene-bridged DIMIT,
GC-1, and propionic acid GC-1. The comparison, shown
in Figure 4, demonstrates that both changes differen-
tially increase affinity for TRâ. The loss of the amino
group increases affinity (2.9 ( 0.3)-fold and (5.6 ( 0.4)-
fold for TRR and TRâ, respectively, while a correspond-
ing (2.3 ( 0.3)-fold gain in affinity for TRâ is observed
in the side chain methylene to ether substitution.
The free energies of binding associated with the
binding affinities of the compounds (calculated with
units of mol/L) are listed in Table 1. The changes in
selectivity associated with the various structural alter-
ations of the thyromimetics are expressed in Figure 5
as the differential gain in free energy of binding, or
F igu r e 5. Oxyacetic acid polar side chain is the key determinant of TRâ selectivity. Values indicate gain in TRâ selectivity
(kcal/mol).

Thyromimetics
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14 3157
This study demonstrates that subtle changes to the
structures of the polar side chains of high-affinity
thyromimetics can have significant effects on selectivity.
Our understanding of selectivity from these results,
along with the earlier structural and mutagenesis
studies,28 emphasizes the importance of polar interac-
tions between ligand and receptor in the vicinity of the
one varying amino acid residue in the ligand binding
cavity. While the precise ligand-receptor interactions
that govern selectivity remain elusive, structural fea-
tures of both the receptor and ligand that influence
selectivity have been identified.
Exp er im en ta l Section
Th yr oid Hor m on e Recep tor Bin d in g Assa ys. hTRR1
and hTRâ1 were expressed in Escherichia coli and purified as
described previously.35 Competition ligand binding affinities
were determined using 0.1 nM [125I]-T3 in gel filtration binding
assays performed in duplicate as described.35 The Kd and
standard error (SE) values were calculated by fitting the
competition data using the GraphPad Prism computer pro-
gram (GraphPad Software, Inc.)
Gen er a l Meth od s. Unless otherwise indicated, solvents
and reagents were purchased from the Aldrich Chemical Co.
and used without further purification. Tetrahydrofuran was
distilled from sodium benzophenone ketyl prior to use. Other
anhydrous solvents were from Aldrich SureSeal bottles. Water-
sensitive reactions were performed using oven- or flame-dried
glassware. Unless indicated, reactions were performed under
argon inert atmosphere. NMR spectra were obtained using a
Varian Inova 400 MHz spectrometer. Target compounds 7-9
were purified by reverse-phase preparative HPLC.
F igu r e 6. Structures of previously reported GC-1 analogues
with substituents at the 5′-position and at the bridging carbon.
4-Ben zyloxy-2,6-d im eth ylp h en ol (13). To a stirred sus-
pension of 2,6-dimethylhydroquinone (Ru¨tgers Organics) (3.00
g, 21.7 mmol) and potassium carbonate (6.30 g, 45.6 mmol) in
DMF (anhydrous, 10 mL) was added benzyl bromide (2.6 mL,
22 mmol). The reaction mixture was cooled in a cold water
bath and was stirred overnight at room temperature. After
21 h, the reaction was quenched by the cautious addition of 1
M HCl (50 mL), followed by extraction with ethyl acetate (4 ×
50 mL). The combined organic fractions were washed with
saturated aqueous NH4Cl (2 × 20 mL) and brine (2 × 20 mL),
to 5-fold increase in affinity. Interestingly, the B-ring
of GC-1 shows a slightly shifted position, while the
B-rings of triac, DIMIT, and T3 all closely overlap in
structural alignments of the crystal structures of ligand-
ed TR-LBDs.27,28,31
While we have shown the importance of the character
of the polar side chain in determining selectivity toward
binding TRâ, we do know that other features of the
ligand can influence selectivity. Our laboratory has
prepared over 20 analogues of GC-1 in studies of TR
antagonism.32-34 Their structures are summarized in
Figure 6. Most of these analogues bear substituted
phenyl or phenylethynyl substituents at the 5′-position
(24-38), while a racemic series with alkyl, allyl, and
aryl substiuents at the bridging carbon (39-42) has also
been prepared. All show reduced affinity for TR of about
200- to 7000-fold lower than GC-1. TRâ selectivity is
observed with most of these GC-1 analogues; however,
the degree of TRâ selectivity varies considerably be-
tween 0.33- and 20-fold in a manner that is not easily
explained by the character of the extra substituent. The
analogues with 5′ substituents all bind better to TRâ
than to TRR, though the degree of selectivity varies
between 3- and 20-fold.33,34 Analogues with hydroxy-
alkyl, aryl, and alkylamide substitutents at the bridging
carbon (40-42) show 3.6- to 1.5-fold TRR selectivity,
while the allyl-substituted analogue (39) is 7-fold TRâ-
selective.32 Substitution at the bridging carbon can, but
does not necessarily, confer slight TRR selectivity. The
binding characteristics of these analogues indicate that
their perturbations of the ligand binding cavity are not
equally tolerated by TRR and TRâ, presumably because
of structural differences in the ligand binding domains.
then dried (MgSO4), filtered through
a Celite pad, and
concentrated under reduced pressure. The residue was purified
by flash chromatography (silica, 5% f 10% ethyl acetate in
hexanes) to give the product (440 mg, 9% yield) as a white
1
solid. H NMR (400 MHz, CDCl3): δ 7.30-7.43 (m, 5 H), 6.63
(s, 2 H), 4.97 (s, 2 H), 4.25 (s, 1 H), 2.21 (s, 6 H). 13C NMR
(100 MHz, CDCl3): δ 152.23, 146.32, 137.48, 128.49, 127.77,
127.43, 124.09, 114.90, 70.56, 16.24. HRMS exact mass calcd
for C12H16O2: 228.1150. Found: 228.1148.
3-Isop r op yl-4-m et h oxym et h oxyp h en ylb or on ic Acid
(11). A stirred solution of 3-isopropyl-4-methoxymethoxybro-
mobenzene (2.5 g, 9.6 mmol) in THF (25 mL) was chilled to
-78 °C, and n-butyllithium (2.5 M in hexanes, 4.0 mL, 10
mmol) was added via syringe over several minutes. After 15
min of stirring, trimethyl borate (1.2 mL, 11 mmol) was added
via syringe. The mixture was stirred overnight, slowly warm-
ing to room temperature. Then 1 M HCl (25 mL) was added
and stirring was continued for another hour. The aqueous and
organic layers were separated, and the aqueous layer was
extracted with methylene chloride (2 × 40 mL). Combined
organic fractions were dried (MgSO4), filtered through a Celite
pad, and concentrated under reduced pressure to yield the
product (2.0 g) as a thick clear syrup that solidified over a few
days. The product was used directly in the next reaction
without further purification.
r-[4-(3-Isop r op yl-4-m et h oxym et h oxyp h en oxy)-3,5-d i-
m eth ylp h en oxy]tolu en e (14). To a stirred solution of 3-iso-
propyl-4-methoxymethoxyphenylboronic acid (11) (approxi-
mately 290 mg, 1.3 mmol) and 4-benzyloxy-2,6-dimethylphenol
(13) in methylene chloride (anhydrous, 10 mL) was added

3158 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14
Yoshihara et al.
copper(II) acetate (80 mg, 0.44 mmol), triethylamine (305 µL,
2.19 mmol), and powdered 4 Å molecular sieves (spatula tip).
A drying tube was attached, and the mixture was stirred under
ambient atmosphere. After 25 h, the mixture was filtered
through a pad of Celite, which was rinsed with ethyl acetate.
Rotary evaporation yielded a brown-green semisolid that was
purified by flash chromatography to yield the enriched product
(149 mg), which was used directly in the next reaction.
quenched with the cautious addition of 1 M HCl (250 mL).
The aqueous and organic phases were separated, and the
aqueous phase was extracted with diethyl ether (2 × 180 mL).
The combined organic phases were washed with saturated
NH4
filtered through a Celite pad, and concentrated under reduced
pressure. The crude product was purified with two rounds of
KugelRohr distillation, giving an off-white solid (22.3 g, 78%
yield). 1H NMR (400 MHz, CDCl3): δ 7.43-7.32 (m, 5 H), 6.73
(s, 2 H), 5.01 (s, 2 H), 2.38 (s, 6 H). 13C NMR (100 MHz,
CDCl3): δ 157.25, 139.12, 136.84, 128.57, 127.97, 127.40,
118.49, 114.72, 70.04, 24.06. HRMS exact mass calcd for
Cl (2 × 50 mL) and brine (2 × 50 mL), then dried (MgSO4),
4-(3-Isop r op yl-4-m eth oxym eth oxyp h en oxy)-3,5-d im e-
th ylp h en ol (14a ). A solution of R-[4-(3-isopropyl-4-meth-
oxymethoxyphenoxy)-3,5-dimethylphenoxy]toluene (14) (ap-
proximately 0.25 mmol) in ethyl acetate was sparged with Ar,
and a spatula tip of palladium on carbon (10%) was added.
The flask was purged with H2, and the mixture was stirred
overnight under H2 atmosphere maintained with balloon
pressure and then was filtered through a Celite pad that was
rinsed with ethyl acetate. After rotary evaporation, the crude
product was purified by flash chromatography (silica, 5% f
20% ethyl acetate in hexanes) to yield the product (36 mg, 27%
C
15H15BrO: 290.0306. Found: 290.0320.
4-Ben zyloxy-2,6-d im eth ylben za ld eh yd e (16). A stirred
solution of bromobenzene 15a (21.0 g, 72.1 mmol) in THF (200
mL) was cooled to -78 °C. Then n-butyllithium (2.5 M in
hexanes, 32 mL, 79 mmol) was added via syringe over several
minutes. A thick precipitate formed, and stirring was main-
tained manually. After 10 min, DMF (anhydrous, 8.4 mL, 110
mmol) was added via syringe over a period of 10 min with
frequent shaking of the flask as the precipitate dissolved.
Stirring at -78 °C was maintained for 20 min, and then the
reaction was quenched by the addition of 1 M HCl (150 mL).
The aqueous and organic layers were separated, and the
aqueous phase was extracted with diethyl ether (3 × 100 mL).
The combined organic fractions were washed with saturated
NaHCO3 (100 mL) and brine (100 mL) and then dried (MgSO4),
filtered through a Celite pad, and concentrated under reduced
pressure. Purification by short-path vacuum distillation, fol-
lowed by KugelRohr distillation (1 Torr, 160 °C) gave the
product (14.0 g, 80% yield) as an off-white solid. 1H NMR (400
MHz, CDCl3): δ 10.47 (s, 1 H), 7.42-7.32 (m, 5 H), 6.67 (s, 2
H), 5.09 (s, 2 H), 2.60 (s, 6 H). 13C NMR (100 MHz, CDCl3): δ
191.56, 161.85, 144.44, 136.17, 128.64, 128.18, 127.42, 126.13,
115.61, 69.84, 21.06. HRMS exact mass calcd for C16H16O2:
240.1150. Found: 240.1151.
3-Isop r op yl-4-tr iisop r op ylsilyloxybr om oben zen e (17).
To a stirred solution of triisopropylsilyl chloride (12 mL, 56
mmol) in anhydrous 1,2-dichloroethane (70 mL) was added
4-bromo-2-isopropylphenol (9.6 g, 46 mmol) and imidazole (7.8
g, 114 mmol). The reaction mixture was refluxed for 30 min
and then was stirred overnight at room temperature. The
reaction mixture was refluxed 1 h further, and then 150 mL
of 0.6 M HCl was added, layers were separated, and the
aqueous phase was extracted with diethyl ether. The combined
organic fractions were washed with saturated NaHCO3, dried
(MgSO4), and filtered through a Celite plug and solvent was
removed by rotary evaporation to yield an oil (18.3 g). Purifica-
tion by fractional distillation (bp 137 °C, 0.3 mm) yielded
bromobenzene 17 as a white solid (12.3 g, 72%). 1H NMR (600
MHz, CDCl3): δ 7.27 (d, J ) 2.6 Hz, 1 H), 7.11 (dd, J ) 8.4,
2.6 Hz, 1 H), 6.64 (d, J ) 8.8 Hz, 1 H), 3.33 (heptet, J ) 6.8
Hz, 1 H), 1.30 (heptet, J ) 7.5 Hz, 3 H), 1.19 (d, J ) 6.6 Hz,
6 H), 1.10 (d, J ) 7.7 Hz, 18 H). 13C NMR (100 MHz, CDCl3):
δ 152.29, 140.98, 129.27, 128.93, 119.36, 113.14, 26.85, 22.61,
18.04, 13.05. HRMS exact mass calcd for C18H31BrOSi: 370.1328.
Found: 370.1336.
1
yield from 13). H NMR (400 MHz, CDCl3): δ 6.89 (d, J ) 9.3
Hz, 1 H), 6.74 (d, J ) 2.9 Hz, 1 H), 6.54 (s, 2 H), 6.36 (dd, J )
8.8, 2.9 Hz, 1 H), 5.12 (s, 2 H), 4.93 (s, 1 H), 3.49 (s, 3 H), 3.29
(heptet, J ) 6.8, Hz, 1 H), 2.06 (s, 6 H), 1.18 (d, J ) 6.8 Hz, 6
H). 13C NMR (100 MHz, CDCl3): δ 153.19, 152.06, 148.81,
145.10, 139.47, 132.70, 115.41, 115.17, 112.91, 111.14, 95.38,
55.97, 27.05, 22.76, 22.63, 16.47. HRMS exact mass calcd for
C
19H24O3: 316.1675. Found: 316.1665.
[4-(3-Isopr opyl-4-m eth oxym eth oxyph en oxy)-3,5-dim eth -
ylp h en oxy]a cetic Acid Meth yl Ester (14b). To a stirred
suspension of 14a (30 mg, 0.095 mmol) and cesium carbonate
(46 mg, 0.14 mmol) in DMF (anhydrous, 200 µL) was added
methyl bromoacetate (13 µL, 0.14 mmol) via syringe. The
mixture was stirred overnight at room temperature. Then the
reaction was quenched with half-saturated NH4Cl (8 mL) and
the mixture was extracted with diethyl ether (2 × 10 mL). The
combined organic fractions were washed with brine (2 × 2 mL),
dried (MgSO4), filtered through a Celite pad, and concentrated
under reduced pressure to yield the product (30 mg, 81% yield).
1H NMR (400 MHz, CDCl3): δ 6.88 (d, J ) 9.3 Hz, 1 H), 6.73
(d, J ) 2.9 Hz, 1 H), 6.63 (s, 2 H), 6.34 (dd, J ) 9.0, 3.2 Hz, 1
H), 5.11 (s, 2 H), 4.62 (s, 2 H), 3.82 (s, 3 H), 3.48 (s, 3 H), 3.29
(heptet, J ) 6.8, Hz, 1 H), 2.09 (s, 6 H), 1.18 (d, J ) 7.3 Hz, 6
H). 13C NMR (100 MHz, CDCl3): δ 169.55, 154.30, 153.02,
148.90, 146.00, 139.44, 132.68, 115.34, 114.63, 112.94, 111.12,
95.35, 65.64, 55.94, 52.21, 27.05, 22.73, 16.66. HRMS exact
mass calcd for C22H28O6: 388.1886. Found: 388.1895.
[4-(4-Hyd r oxy-3-isop r op ylp h en oxy)-3,5-d im eth ylp h en -
oxy]a cetic Acid (7). To a stirred suspension of methyl ester
14b (30 mg, 0.077 mmol) and lithium hydroxide monohydrate
(7.0 mg, 0.17 mmol) in methanol (2 mL) was added water (7.6
µL, 0.42 mmol). The mixture was stirred at room temperature
for 4 h, and then solvent was removed under reduced pressure.
The residue was resuspended in a 1:1 mixture of saturated
NH4Cl/1 M HCl (6 mL) and extracted with ethyl acetate (3 ×
6 mL). The combined organic fractions were dried (MgSO4),
filtered through a Celite pad, and concentrated under reduced
pressure. The crude product was purified by flash chromatog-
raphy (silica, 7.5% ethyl acetate, 3% acetic acid in chloroform)
and preparative TLC (silica, 20 cm × 20 cm, 15% ethyl acetate,
3% acetic acid in chloroform, eluted with 10% methanol in
4-Ben zyloxy-2,6-d im eth ylp h en yl[3-isop r op yl-4-(tr iiso-
p r op ylsilyloxy)p h en yl]m eth a n ol (18). A stirred solution of
17 (13.9 g, 37.5 mmol) in THF (250 mL) was cooled to -78 °C,
and n-butyllithium (2.5 M in hexanes, 16 mL, 40 mmol) was
added via syringe over 10 min. After 10 min of stirring at -78
°C, 16 (9.00 g, 37.5 mmol), dissolved in THF (10 mL), was
added dropwise via cannula over 20 min, followed by rinses
with THF (2 × 5 mL). After the mixture was stirred for 30
min at -78 °C, the reaction was quenched with 1 M HCl (45
mL). The aqueous and organic layers were separated, and the
aqueous phase was extracted with diethyl ether (4 × 40 mL).
The combined organic fractions were washed with saturated
NaHCO3 (30 mL) and brine (30 mL), then dried (MgSO4),
filtered through a Celite pad, and concentrated under reduced
pressure. Flash chromatography of the residue (2% f 7% ethyl
acetate in hexanes) gave the purified product (15.5 g, 77%
yield). 1H NMR (400 MHz, CDCl3): δ 7.45-7.32 (m, 4 H), 7.23
1
chloroform) to give a white solid (7 mg, 30% yield). H NMR
(400 MHz, CD3OD): δ 6.70-6.65 (m, 2 H), 6.67 (s, 2 H), 6.25
(dd, J ) 8.8, 2.9 Hz, 1 H), 4.61 (s, 2 H), 3.21 (heptet, J ) 6.8
Hz, 1 H), 2.05 (s, 6 H), 1.13 (d, J ) 7.3 Hz, 6 H). 13C NMR
(100 MHz, CDCl3): δ 172.94, 155.94, 152.78, 149.66, 147.25,
137.52, 133.64, 116.52, 115.65, 113.28, 112.33, 66.22, 28.11,
22.95, 16.75. HRMS exact mass calcd for C19H22O5: 330.1467.
Found: 330.1471.
4-Ben zyloxy-2,6-d im eth ylbr om oben zen e (15a ). A sus-
pension 4-bromo-3,5-dimethylphenol (20.0 g, 99.5 mmol), ben-
zyl bromide (17 g, 99 mmol), and potassium carbonate (20.6
g, 149 mmol) in DMF (anhydrous, 20 mL) was stirred
overnight at room temperature. The reaction mixture was
diluted with diethyl ether (150 mL), and the reaction was

Thyromimetics
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14 3159
(d, J ) 1.5 Hz, 1 H), 6.75 (dd, J ) 8.2, 1.5 Hz, 1 H), 6.67-6.65
(m, 3 H), 6.24 (d, J ) 4.3 Hz, 1 H), 5.04 (s, 2 H), 3.36 (heptet,
J ) 7.0, Hz, 1 H), 2.24 (s, 6 H), 1.29 (heptet, J ) 7.6 Hz, 3 H),
1.17 (dd, J ) 8.2, 7.0 Hz, 6 H), 1.10 (d, J ) 7.3 Hz, 18 H). 13C
NMR (100 MHz, CDCl3): δ 157.62, 151.72, 138.72, 138.13,
137.16, 135.07, 132.49, 128.53, 127.87, 127.48, 123.50, 123.39,
117.46, 115.20, 70.95, 69.74, 26.74, 22.83, 20.99, 18.09, 13.07.
HRMS exact mass calcd for C34H48O3Si: 532.3373. Found:
532.3379.
) 17.6, 10.7 Hz, 1 H), 6.59 (d, J ) 8.3 Hz, 1 H), 6.50 (dd, J )
8.3, 2.0 Hz, 1 H), 5.71 (d, J ) 17.6 Hz, 1 H), 5.18 (d, J ) 11.7
Hz, 1 H), 3.94 (s, 2 H), 3.32 (heptet, J ) 6.8 Hz, 1 H), 2.24 (s,
6 H), 1.27 (heptet, J ) 7.3, Hz, 3 H), 1.16 (d, J ) 6.8 Hz, 6 H),
1.08 (d, J ) 7.3 Hz, 18 H). 13C NMR (100 MHz, CDCl3): δ
151.06, 138.17, 137.54, 137.24, 136.88, 135.20, 131.44, 125.99,
125.94, 124.90, 117.65, 112.65, 34.43, 26.66, 22.84, 20.29,
18.11, 13.07. HRMS exact mass calcd for C29H44OSi: 436.3161.
Found: 436.3163.
4-[3-Isop r op yl-4-(t r iisop r op ylsilyloxy)b en zyl]-3,5-d i-
m eth ylben za ld eh yd e (20). A stirred solution of styrene 19a
(2.15 g, 4.9 mmol) in methylene chloride (anhydrous, 200 mL)
was cooled to -78 °C and sparged with an oxygen/ozone
mixture until the solution took on a light-violet color. The
solution was then sparged with Ar for 15 min, and then
triphenylphosphine (7.5 g, 29 mmol) dissolved in methylene
chloride was added via cannula. After the mixture was stirred
for 50 min, the solvent was removed under reduced pressure.
The residue was purified by flash chromatography (silica, 0.5%
f 1% diethyl ether in hexanes) to give 20 (1.79 g, 86% yield)
4-[3-Isop r op yl-4-(t r iisop r op ylsilyloxy)b en zyl]-3,5-d i-
m eth ylp h en ol (18a ). A solution of 18 (9.35 g, 17.8 mmol) in
1:1 ethyl acetate/ethanol (30 mL) in a glass Parr hydrogenator
flask was sparged with Ar. Palladium on carbon (10%, 1.3 g)
was added, and the flask was attached to a Parr hydrogenator
and shaken for 24 h under H2 at 35 psi. The mixture was then
filtered through a pad of Celite, which was then rinsed with
ethyl acetate, and the filtrate was concentrated to yield the
product (7.77 g, 100% yield) as a white solid. 1H NMR (400
MHz, CDCl3): δ 6.92 (s, 1 H), 6.61 (d, J ) 8.3 Hz, 1 H), 6.54-
6.51 (m, 3 H), 4.96 (s, 1 H), 3.87 (s, 2 H), 3.33 (heptet, J ) 6.9
Hz, 1 H), 2.18 (s, 6 H), 1.27 (heptet, J ) 7.3 Hz, 3 H), 1.16 (d,
J ) 6.9 Hz, 6 H), 1.09 (d, J ) 7.6 Hz, 18 H). 13C NMR (100
MHz, CDCl3): δ 153.20, 150.96, 138.65, 138.10, 131.96, 130.02,
125.82, 124.83, 117.60, 114.72, 33.74, 26.62, 22.83, 20.32,
18.09, 13.05. HRMS exact mass calcd for C27H42O2Si: 426.2954.
Found: 426.2950.
1
as a white solid. H NMR (400 MHz, CDCl3): δ 9.94 (s, 1 H),
7.56 (s, 2 H), 6.90 (d, J ) 2.0 Hz, 1 H), 6.61 (d, J ) 8.3 Hz, 1
H), 6.48 (dd, J ) 8.3, 2.44 Hz, 1 H), 4.02 (s, 2 H), 3.32 (heptet,
J ) 6.8 Hz, 1 H), 2.33 (s, 6 H), 1.26 (heptet, J ) 7.3 Hz, 3 H),
1.15 (d, J ) 7.3 Hz, 6 H), 1.09 (d, J ) 7.3 Hz, 18 H). 13C NMR
(100 MHz, CDCl3): δ 192.51, 151.35, 145.30, 138.50, 138.18,
134.44, 130.07, 129.38, 125.93, 124.84, 117.78, 34.92, 26.63,
22.79, 20.23, 18.08, 13.05. HRMS exact mass calcd for C28H42O2-
Si: 438.2954. Found: 438.2959.
4-[3-Isop r op yl-4-(t r iisop r op ylsilyloxy)b en zyl]-3,5-d i-
m eth ylp h en yltr iflu or om eth a n esu lfon a te (19). A stirred
solution of 18a (10.0 g, 23.4 mmol) and pyridine (anhydrous,
20 mL, 250 mmol) in methylene chloride (anhydrous, 150 mL)
was cooled in an ice bath. Triflic anhydride (4.3 mL, 26 mmol)
was added via syringe over 5 min, with vigorous stirring
maintained. The mixure was stirred for 4 h, slowly warming
to room temperature. Then a 1:1 mixture of saturated NH4Cl
and 1 M HCl (100 mL) was added. The aqueous and organic
layers were separated, and the aqueous phase was extracted
with diethyl ether (3 × 100 mL). The combined organic
fractions were dried (MgSO4), filtered through a Celite pad,
and concentrated under reduced pressure. Flash chromatog-
raphy (silica, 9% diethyl ether in hexanes) gave the product
(9.2 g, 99% yield with recovered starting material) and
(E)-3-{4-[3-Isop r op yl-4-(t r iisop r op ylsilyloxy)b en zyl]-
3,5-d im eth ylp h en yl}a cr ylic Acid Ben zyl Ester (20a ). A
solution of benzaldehyde 20 (500 mg, 1.13 mmol) and benzyl
(triphenylphosphoranylidene)acetate (834 mg, 2.03 mmol) in
THF (25 mL) was stirred at reflux overnight. Solvent was
removed under reduced pressure, and the residue was purified
by flash chromatography (silica, 2% f 4% ethyl acetate in
hexanes) to give 20a (646 mg, 100% yield) as a syrup. 1H NMR
(400 MHz, CDCl3): δ 7.68 (d, J ) 16.1 Hz, 1 H), 7.42-7.31
(m, 5 H), 7.21 (s, 2 H), 6.92 (d, J ) 1.5 Hz, 1 H), 6.60 (d, J )
8.3 Hz, 1 H), 6.50-6.44 (m, 2 H), 5.25 (s, 2 H), 3.96 (s, 2 H),
3.32 (heptet, J ) 6.8 Hz, 1 H), 2.25 (s, 6 H), 1.27 (heptet, J )
7.3 Hz, 3 H), 1.15 (d, J ) 6.8 Hz, 6 H), 1.08 (d, J ) 7.3 Hz, 18
H). 13C NMR (100 MHz, CDCl3): δ 167.03, 151.18, 145.46,
140.71, 138.32, 137.76, 136.19, 132.01, 130.76, 128.53, 128.17,
128.13, 127.86, 125.94, 124.82, 117.69, 116.63, 66.17, 34.59,
26.63, 22.80, 20.25, 18.08, 13.03. HRMS exact mass calcd for
1
unreacted phenol (2.9 g). H NMR (400 MHz, CDCl3): δ 6.96
(s, 2 H), 6.88 (d, J ) 2.0 Hz, 1 H), 6.62 (d, J ) 8.3 Hz, 1 H),
6.46 (dd, J ) 8.3, 2.4 Hz, 1 H), 3.94 (s, 2 H), 3.32 (heptet, J )
6.8, Hz, 1 H), 2.27 (s, 6 H), 1.27 (heptet, J ) 7.8, Hz, 3 H),
1.15 (d, J ) 6.8 Hz, 6 H), 1.09 (d, J ) 7.3 Hz, 18 H). 13C NMR
(100 MHz, CDCl3): δ 151.37, 147.41, 139.74, 138.50, 138.25,
130.23, 125.82, 124.76, 120.20, 118.77 (qt, J ) 320.7 Hz),
117.78, 34.10, 26.64, 22.78, 20.42, 18.09, 13.07. HRMS exact
mass calcd for C28H41F3O4SSi: 558.2457. Found: 558.2447.
C
37H50O3Si: 570.3529. Found: 570.3524.
3-[4-(4-Hydr oxy-3-isopr opylben zyl)-3,5-dim eth ylph en yl]-
a cr ylic Acid Ben zyl Ester (20b). A solution of aryl silyl ether
20a (60 mg, 0.11 mmol) and triethylamine trihydrofluoride (1.7
mL, 11 mmol) in THF (3 mL) was stirred overnight and then
cooled in an ice bath and quenched with the cautious addition
of potassium carbonate (2.0 g, 15 mmol) dissolved in water (5
mL). After addition of saturated NaHCO3 (5 mL), the mix was
extracted with diethyl ether (3 × 15 mL), then dried (MgSO4),
filtered through a Celite pad, and concentrated under reduced
pressure. Purification of the residue with flash chromatogra-
phy (silica, 10% f 20% ethyl acetate in hexanes) gave 20b
[4-(2,6-Dim eth yl-4-vin ylben zyl)-2-isop r op ylp h en oxy]-
tr iisop r op ylsila n e (19a ). To a stirred suspension of triflate
19 (5.00 g, 8.95 mmol), lithium chloride (1.14 g, 26.8 mmol),
and dichlorobis(triphenylphosphine)palladium(II) (314 mg,
0.447 mmol) in DMF (anhydrous, degassed, 25 mL) was added
vinyltributyltin (2.8 mL, 9.8 mmol). The reaction flask was
fitted with a heating mantle, and a thermocouple needle was
attached to a temperature controller. The reaction mixture was
stirred for 2 h at 60 °C, and then most of the solvent was
removed under reduced pressure. The residue was resus-
pended in 1:1 diethyl ether/hexanes (50 mL) and aqueous
saturated potassium fluoride (10 mL). The mixture was stirred
for 2 h and then filtered through a pad of Celite, which was
rinsed with diethyl ether (200 mL). Hexanes (200 mL) were
added to the filtrate, and the aqueous and organic phases were
separated. The organic layer was washed with saturated
NaHCO3 (25 mL) and half-saturated brine (4 × 25 mL), then
dried (MgSO4), filtered through a Celite pad, and concentrated
under reduced pressure. Flash chromatography (silica, hex-
anes), followed by KugelRohr vacuum distillation to remove
the organotin residue, gave a cloudy syrup that contained ∼13
mol % organotin residue (1H NMR) (3.80 g, 85% yield). A small
sample was repurified for characterization. 1H NMR (400 MHz,
CDCl3): δ 7.10 (s, 2 H), 6.94 (d, J ) 2.0 Hz, 1 H), 6.66 (dd, J
1
(40 mg, 88% yield). H NMR (400 MHz, CDCl3): δ 7.68 (d, J
) 16.1 Hz, 1 H), 7.42-7.32 (m, 5 H), 7.20 (s, 2 H), 6.59 (d, J
) 8.3 Hz, 1 H), 6.53 (d, J ) 8.3 Hz, 1 H), 6.46 (d, J ) 16.1 Hz,
1 H), 5.25 (s, 2 H), 3.96 (s, 2 H), 3.17 (heptet, J ) 6.8 Hz, 1 H),
2.24 (s, 6 H), 1.20 (d, J ) 6.8 Hz, 6 H). 13C NMR (100 MHz,
CDCl3): δ 167.26, 151.07, 145.62, 140.50, 137.72, 136.05,
134.45, 132.00, 130.89, 128.53, 128.46, 128.17, 127.90, 126.16,
125.27, 116.57, 115.22, 66.30, 34.46, 27.07, 22.52, 20.18. HRMS
exact mass calcd for (M - benzyl) C21H23O3: 323.1647.
Found: 323.1632.
3-{4-[3-Isop r op yl-4-(t r iisop r op ylsilyloxy)b en zyl]-3,5-
d im eth ylp h en yl}p r op ion ic Acid (20c). A solution of benzyl
ester 20b (490 mg, 0.86 mmol) in ethyl acetate (30 mL) and
acetic acid (2 mL) was put in a Parr hydrogenator flask and
sparged with Ar. Palladium on carbon (10%, 90 mg) was added,
and the mixture was shaken for 20 h under H2 atmosphere at

3160 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14
Yoshihara et al.
33 psi. The mixture was then filtered through a Celite pad,
which was rinsed with ethyl acetate and ethanol. The filtrate
was concentrated under reduced pressure, with toluene azeotro-
ping to remove residual acetic acid. Flash chromatography
(silica, 10% ethyl acetate, 1% acetic acid in hexanes) gave 20c
(355 mg, 86% yield) as a crystalline solid. 1H NMR (400 MHz,
CDCl3): δ 6.94 (s, 1 H), 6.89 (s, 2 H), 6.59 (d, J ) 7.8 Hz, 1 H),
6.49 (d, J ) 8.3 Hz, 1 H), 3.92 (s, 2 H), 3.32 (heptet, J ) 6.8
Hz, 1 H), 2.90 (t, J ) 7.8 Hz, 2 H), 2.69 (t, J ) 8.3 Hz, 2 H),
2.22 (s, 6 H), 1.27 (heptet, J ) 7.8 Hz, 3 H), 1.16 (d, J ) 6.8
Hz, 6 H), 1.08 (d, J ) 7.3 Hz, 18 H). 13C NMR (100 MHz,
CDCl3): δ 178.73, 151.01, 138.12, 137.65, 137.31, 135.69,
131.57, 127.87, 126.00, 124.82, 117.61, 35.62, 34.23, 30.18,
26.63, 22.83, 20.25, 18.11, 13.06. HRMS exact mass calcd for
in toluene, 0.90 mL, 0.45 mmol). After the mixture was stirred
for 15 min, a prechilled solution of trisylazide (Omega, Inc.,
175 mg, 0.57 mmol) in THF (15 mL) was added via Teflon
cannula over 1 min. After approximately 45 s from the end of
the addition, acetic acid (78 µL, 1.4 mmol) was added via
syringe and the reaction mixture was slowly warmed to room
temperature over 2.5 h. Solvent was removed under reduced
pressure, and the residue was dissolved in methylene chloride
(100 mL) and washed with half-saturated NaHCO3 (20 mL)
and brine (20 mL). The solution was dried (MgSO4), filtered
through a Celite pad, and concentrated under reduced pres-
sure. The residue was purified by flash chromatography (silica,
5% f 10% ethyl acetate in hexanes) to give 21 (226 mg, 73%)
as a thick syrup. 1H NMR (400 MHz, CDCl3): δ 7.37-7.27 (m,
3 H), 7.22-7.18 (m, 2 H), 6.98 (s, 2 H), 6.95 (d, J ) 2.0 Hz, 1
H), 6.58 (d, J ) 8.3 Hz, 1 H), 6.47 (dd, J ) 8.1, 2.2 Hz, 1 H),
5.29 (dd, J ) 8.8, 5.9 Hz, 1 H), 4.60-4.55 (m, 1 H), 4.13 (dd,
J ) 9.0, 2.7 Hz, 1 H), 3.99 (t, J ) 8.3 Hz, 1 H), 3.92 (dd, J )
16.1, 5.9 Hz, 2 H), 3.35-3.28 (m, 2 H), 3.14 (dd, J ) 13.7, 5.9
Hz, 1 H), 3.00 (dd, J ) 13.4, 9.0 Hz, 1 H), 2.83 (dd, J ) 13.4,
9.5 Hz, 1 H), 2.23 (s, 6 H), 1.31-1.24 (m, 3 H), 1.16 (dd, J )
6.8, 2.0 Hz, 6 H), 1.08 (d, J ) 6.8 Hz, 18 H). 13C NMR (100
MHz, CDCl3): δ 170.77, 152.69, 151.04, 138.14, 137.45, 136.79,
134.71, 132.92, 131.31, 129.38, 129.01, 128.85, 127.48, 126.04,
124.78, 117.54, 66.42, 61.17, 55.40, 37.58, 37.34, 34.26, 26.62,
22.79, 20.21, 18.07, 13.02. HRMS exact mass calcd for
C
30H46O3Si: 482.3216. Found: 482.3217.
3-[4-(4-Hydr oxy-3-isopr opylben zyl)-3,5-dim eth ylph en yl]-
p r op ion ic Acid (9). A solution of benzyl ester 20b (21 mg,
0.051 mmol) in ethyl acetate (2 mL) was sparged with Ar, and
then palladium on carbon (10%, small spatula tip) was added.
After being stirred overnight under H2 atmosphere maintained
with balloon pressure, the mixture was filtered through a
Celite pad, which was rinsed with ethyl acetate and ethanol.
The filtrate was concentrated under reduced pressure, and the
residue was purified by preparative TLC (silica, 20 cm × 20
cm × 1000 µm, 4% methanol, 1% acetic acid in chloroform) to
give 9 (15 mg, 90% yield). 1H NMR (400 MHz, CD3OD): δ 6.88
(s, 2 H), 6.81 (s, 1 H), 6.56 (d, J ) 8.3 Hz, 1 H), 6.49 (dd, J )
8.3, 2.0 Hz, 1 H), 3.89 (s, 2 H), 3.19 (heptet, J ) 7.3 Hz, 1 H),
2.82 (t, J ) 7.6 Hz, 2 H), 2.57 (t, J ) 7.8 Hz, 2 H), 2.18 (s, 6
H), 1.12 (d, J ) 6.8 Hz, 6 H). 13C NMR (100 MHz, CD3OD): δ
176.98, 153.39, 139.61, 138.08, 136.65, 135.82, 131.78, 128.94,
126.70, 126.33, 115.82, 36.92, 34.85, 31.67, 28.01, 23.05, 20.30.
HRMS exact mass calcd for C21H26O3: 326.1882. Found:
326.1888.
(S)-(4)-Ben zyl-3-(3-{4-[3-isop r op yl-4-(t r iisop r op ylsil-
yloxy)ben zyl]-3,5-d im eth ylp h en yl}p r op ion yl)oxa zolid in -
2-on e (20d ). A stirred solution of carboxylic acid 20c (304 mg,
0.63 mmol) in THF (15 mL) was chilled to -78 °C, and
triethylamine (114 µL, 0.82 mmol) and pivaloyl chloride (85
µL, 0.69 mmol) were added via syringe. The mixture was
stirred for 15 min at -78 °C, then for 30 min on an ice bath,
and then at -78 °C again. To a separate stirred solution of
(S)-4-benzyl-2-oxazolidinone (200 mg, 1.13 mmol) in THF (9
mL) cooled to -78 °C was added n-butyllithium (2.5 M in
hexane, 450 µL, 1.13 mmol). After 10 min of stirring, the
oxazolidinone lithium salt was added via cannula to the mixed
anhydride solution. After the mixture was stirred for 30 min
at -78 °C and another 30 min while slowly warming to room
temperature, the reaction was quenched with the addition of
1 M NaHSO4 (15 mL). After removal of most of the THF under
reduced pressure, the residue was extracted with ethyl acetate
(3 × 20 mL). The combined organic fractions were washed with
saturated NaHCO3 (15 mL) and brine (10 mL), then dried
(MgSO4), filtered through a Celite pad, and concentrated under
reduced pressure. Purification of the residue by flash chro-
matography (silica, 5% ethyl acetate in hexanes) gave 20d (359
mg, 89% yield) as a colorless syrup. 1H NMR (400 MHz,
CDCl3): δ 7.31-7.23 (m, 3 H), 7.18 (d, J ) 6.8 Hz, 2 H), 6.96
(d, J ) 2.4 Hz, 1 H), 6.94 (s, 2 H), 6.58 (d, J ) 8.3 Hz, 1 H),
6.48 (dd, J ) 8.3, 2.4 Hz, 1 H), 4.67 (td, J ) 6.4, 3.4 Hz, 1 H),
4.19-4.13 (m, 2 H), 3.92 (s, 2 H), 3.36-3.21 (m, 4 H), 3.02-
2.90 (m, 2 H), 2.76 (dd, J ) 13.4, 9.5 Hz, 1 H), 2.22 (s, 6 H),
1.26 (m, J ) 7.8 Hz, 3 H), 1.17 (d, J ) 6.4 Hz, 6 H), 1.08 (d, J
) 7.3 Hz, 18 H). 13C NMR (100 MHz, CDCl3): δ 172.59, 153.38,
150.96, 138.04, 137.86, 137.14, 135.54, 135.19, 131.61, 129.37,
128.89, 128.15, 127.29, 126.02, 124.79, 117.56, 66.11, 55.07,
37.81, 37.22, 34.21, 29.85, 26.62, 22.81, 20.22, 18.08, 13.01.
HRMS exact mass calcd for C40H55NO4Si: 641.3900. Found:
641.3905.
C
40H54N4O4Si: 682.3914. Found: 682.3932.
(S)-2-Azid o-3-{4-[3-isop r op yl-4-(tr iisop r op ylsilyloxy)-
ben zyl]-3,5-d im eth ylp h en yl}p r op ion ic Acid (21a ). To a
stirred solution of N-acyloxazolidinone 21 (58 mg, 0.085 mmol)
in 3:1 THF/water (4 mL) cooled to 0 °C was added hydrogen
peroxide (50 wt % solution, 20 µL, 0.34 mmol) and lithium
hydroxide monohydrate (7.1 mg, 0.17 mmol). After the mixture
was stirred for 2.5 h, the reaction was quenched with Na2S2O3
(0.4 M, 935 µL, 0.37 mmol) and half-saturated NaHCO3 (5 mL).
After acidification to pH 1 with HCl, the mixture was extracted
with methylene chloride (4 × 10 mL). The combined organic
fractions were washed with 1 M NaHSO4 (5 mL), then dried
(MgSO4), filtered through a Celite pad, and concentrated under
reduced pressure. Purification of the residue with flash chro-
matography (silica, 7.5% ethyl acetate, 1% acetic acid in
hexanes) gave 21a (37 mg, 83% yield). 1H NMR (400 MHz,
CDCl3): δ 6.94 (s, 2 H), 6.92 (d, J ) 1.95 Hz, 1 H), 6.60 (d, J
) 8.30 Hz, 1 H), 6.50 (dd, J ) 8.30, 1.95 Hz, 1 H), 4.14 (dd, J
) 9.28, 4.88 Hz, 1 H), 3.94 (s, 2 H), 3.32 (heptet, J ) 6.84 Hz,
1 H), 3.19 (dd, J ) 14.16, 4.88 Hz, 1 H), 2.95 (dd, J ) 13.92,
9.52 Hz, 1 H), 2.24 (s, 6 H), 1.26 (heptet, J ) 7.81 Hz, 3 H),
1.15 (d, J ) 6.84 Hz, 6 H), 1.09 (d, J ) 7.32 Hz, 18 H). 13C
NMR (100 MHz, CDCl3): δ 175.48, 151.06, 138.19, 137.61,
136.85, 133.13, 131.29, 128.74, 125.94, 124.85, 117.63, 63.23,
37.22, 34.28, 26.62, 22.80, 20.26, 18.10, 13.05. HRMS exact
mass calcd for C30H45N3O3Si: 523.3230. Found: 523.3245.
(S )-2-Azid o-3-{4-[3-isop r op yl-4-h yd r oxyb e n zyl]-3,5-
d im eth ylp h en yl}p r op ion ic Acid (21b). To a stirred solution
of silyl ether 21a (35 mg, 0.067 mmol) in THF (3 mL) was
added triethylamine trihydrofluoride (1.1 mL, 6.7 mmol). After
the mixture was stirred overnight, most of the THF was
removed under reduced pressure. The reaction mixture was
cooled in an ice bath, and the reaction was quenched with the
cautious addition of potassium carbonate (1.3 g, 9.0 mmol)
dissolved in water (5 mL). The solution was reacidified to pH
3 with 6 M HCl and extracted with methylene chloride (3 ×
10 mL). The combined organic fractions were dried (MgSO4),
filtered through a Celite pad, and concentrated under reduced
pressure. The residue was purified by preparative TLC (silica,
20 cm × 20 cm × 1000 µm, 8% methanol, 1% acetic acid in
chloroform) to give 21b (11 mg, 44% yield). 1H NMR (400 MHz,
CD3OD): δ 6.95 (s, 2 H), 6.80 (d, J ) 2.0 Hz, 1 H), 6.56 (d, J
) 8.3 Hz, 2 H), 6.50 (dd, J ) 8.3, 2.0 Hz, 1 H), 4.13 (br s, 1 H),
3.91 (s, 2 H), 3.19 (heptet, J ) 6.8 Hz, 1 H), 3.11 (dd, J ) 13.9,
4.2 Hz, 1 H), 2.90 (dd, J ) 13.4, 8.6 Hz, 1 H), 2.19 (s, 6 H),
1.11 (d, J ) 6.8 Hz, 6 H). 13C NMR (100 MHz, CD3OD): δ
153.41, 138.26, 137.60, 135.86, 135.42, 131.57, 129.97, 126.66,
3-((S)-2-Azido-3-{4-[3-isopr opyl-4-(tr iisopr opylsilyloxy)-
ben zyl]-3,5-dim eth ylph en yl}pr opion yl)-(S)-(4)-ben zyloxa-
zolid in -2-on e (21). To a stirred solution of N-acyloxazolidi-
none 20d (290 mg, 0.45 mmol) in THF (20 mL) cooled to -78
°C was added potassium bis(trimethylsilyl)amide (0.5 M

Thyromimetics
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 14 3161
(15) Wikstrom, L.; J ohansson, C.; Salto, C.; Barlow, C.; Campos
Barros, A.; et al. Abnormal heart rate and body temperature in
mice lacking thyroid hormone receptor alpha 1. EMBO J . 1998,
17, 455-461.
126.36, 115.83, 38.38, 34.87, 28.00, 23.04, 20.29. HRMS exact
mass calcd for C21H25N3O3: 367.1896. Found: 367.1936.
(S)-2-Am in o-3-{4-[3-isop r op yl-4-h yd r oxyb en zyl]-3,5-
d im eth ylp h en yl}p r op ion ic Acid (8). A solution of azidocar-
boxylic acid 21b (11 mg, 0.11 mmol) in 2:1 acetic acid/water
(3 mL) was sparged with Ar, then palladium on carbon (10%,
22 mg) was added, and the mixture was stirred overnight
under H2 atmosphere maintained with balloon pressure. The
reaction mixture was filtered through a small plug of cotton,
concentrated under reduced pressure, and dried in vacuo to
give 8 (10 mg, 97% yield) as a white solid. 1H NMR (400 MHz,
CD3OD): δ 6.99 (s, 2 H), 6.87 (s, 1 H), 6.56 (d, J ) 8.3 Hz, 1
H), 6.51 (dd, J ) 8.3, 2.0 Hz, 1 H), 3.90 (d, J ) 7.8 Hz, 2 H),
3.76 (br s, 1 H), 3.27-3.16 (m, 2 H), 2.91 (dd, J ) 13.7, 8.8 Hz,
1 H), 2.22 (s, 6 H), 1.12 (d, J ) 7.3 Hz, 6 H). 13C NMR (100
MHz, CD3OD): δ 169.33, 153.54, 138.73, 138.12, 135.88,
134.73, 131.47, 130.03, 126.94, 126.36, 115.85, 34.98, 28.13,
23.04, 20.38. HRMS exact mass calcd for C21H27NO3: 341.1991.
Found: 341.1993.
(16) Schwartz, H. L.; Strait, K. A.; Ling, N. C.; Oppenheimer, J . H.
Quantitation of rat tissue thyroid hormone binding receptor
isoforms by immunoprecipitation of nuclear triiodothyronine
binding capacity. J . Biol. Chem. 1992, 267, 11794-11799.
(17) Gullberg, H.; Rudling, M.; Forrest, D.; Angelin, B.; Vennstrom,
B. Thyroid hormone receptor beta-deficient mice show complete
loss of the normal cholesterol 7alpha-hydroxylase (CYP7A)
response to thyroid hormone but display enhanced resistance
to dietary cholesterol. Mol. Endocrinol. 2000, 14, 1739-1749.
(18) Taylor, A. H.; Stephan, Z. F.; Steele, R. E.; Wong, N. C. W.
Beneficial effects of a novel thyromimetic on lipoprotein me-
tabolism. Mol. Pharmacol. 1997, 52, 542-547.
(19) Stephan, Z. F.; Yurachek, E. C.; Sharif, R.; Wasvary, J . M.;
Leonards, K. S.; et al. Demonstration of Potent Lipid-Lowering
Activity by a Thyromimetic Agent Devoid of Cardiovascular and
Thermogenic Effects. Atherosclerosis 1996, 126, 53-63.
(20) Chiellini, G.; Nguyen, N. H.; Yoshihara, H. A. I.; Scanlan, T. S.
Improved synthesis of the iodine-free thyromimetic GC-1. Bioorg.
Med. Chem. Lett. 2000, 10, 2607-2611.
(21) J orgensen, E. C.; Murray, W. J .; Block, P., J r. Thyroxine analogs.
22. Thyromimetic activity of halogen-free derivatives of 3,5-
dimethyl-L-thyronine. J . Med. Chem. 1974, 17, 434-439.
(22) Baxter, J . D.; Dillmann, W. H.; West, B. L.; Huber, R.; Furlow,
J . D.; et al. Selective modulation of thyroid hormone receptor
action. J . Steroid Biochem. Mol. Biol. 2001, 76, 31-42.
(23) Trost, S. U.; Swanson, E.; Gloss, B.; Wang-Iverson, D. B.; Zhang,
H. J .; et al. The thyroid hormone receptor-beta-selective agonist
GC-1 differentially affects plasma lipids and cardiac activity.
Endocrinology 2000, 141, 3057-3064.
(24) Morte, B.; Manzano, J .; Scanlan, T.; Vennstrom, B.; Bernal, J .
Deletion of the thyroid hormone receptor alpha 1 prevents the
structural alterations of the cerebellum induced by hypothy-
roidism. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 3985-3989.
(25) Ribeiro, M. O.; Carvalho, S. D.; Schultz, J . J .; Chiellini, G.;
Scanlan, T. S.; et al. Thyroid hormone-sympathetic interaction
and adaptive thermogenesis are thyroid hormone receptor
isoform-specific. J . Clin. Invest. 2001, 108, 97-105.
(26) Koerner, D.; Schwartz, H. L.; Surks, M. I.; Oppenheimer, J . H.
Binding of selected iodothyronine analogues to receptor sites of
isolated rat hepatic nuclei. High correlation between structural
requirements for nuclear binding and biological activity. J . Biol.
Chem. 1975, 250, 6417-6423.
(27) Wagner, R. L.; Apriletti, J . W.; McGrath, M. E.; West, B. L.;
Baxter, J . D.; et al. A structural role for hormone in the thyroid
hormone receptor. Nature 1995, 378, 690-697.
(28) Wagner, R. L.; Huber, B. R.; Shiau, A. K.; Kelly, A.; Lima, S. T.
C.; et al. Hormone selectivity in thyroid hormone receptors. Mol.
Endocrinol. 2001, 15, 398-410.
(29) Evans, D. A.; Katz, J . L.; West, T. R. Synthesis of diaryl ethers
through the copper-promoted arylation of phenols with arylbo-
ronic acids. An expedient synthesis of thyroxine. Tetrahedron
Lett. 1998, 39, 2937-2940.
(30) Hansch, C.; Leo, A.; Hoekman, D. Exploring QSAR: Hydropho-
bic, Electronic, and Steric Constants; American Chemical Soci-
ety: Washington, DC, 1995; p 384.
(31) Darimont, B. D.; Wagner, R. L.; Apriletti, J . W.; Stallcup, M.
R.; Kushner, P. J .; et al. Structure and specificity of nuclear
receptor-coactivator interactions. Genes Dev. 1998, 12, 3343-
3356.
(32) Yoshihara, H. A. I.; Apriletti, J . W.; Baxter, J . D.; Scanlan, T.
S. A designed antagonist of the thyroid hormone receptor. Bioorg.
Med. Chem. Lett. 2001, 11, 2821-2825.
(33) Chiellini, G.; Nguyen, N. H.; Apriletti, J . W.; Baxter, J . D.;
Scanlan, T. S. Synthesis and biological activity of novel thyroid
hormone analogues: 5′-aryl substituted GC-1 derivatives. Bioorg.
Med. Chem. 2002, 10, 333-346.
(34) Nguyen, N. H.; Apriletti, J . W.; Cunha Lima, S. T.; Webb, P.;
Baxter, J . D.; et al. Rational design and synthesis of a novel
thyroid hormone antagonist that blocks coactivator recruitment.
J . Med. Chem. 2002, 45, 3310-3320.
(35) Apriletti, J . W.; Baxter, J . D.; Lau, K. H.; West, B. L. Expression
of the rat alpha 1 thyroid hormone receptor ligand binding
domain in Escherichia coli and the use of a ligand-induced
conformation change as a method for its purification to homo-
geneity. Protein Expression Purif. 1995, 6, 363-370.
Ack n ow led gm en t. This work was supported by the
National Institutes of Health (Grant DK52798 for T.S.S.
and Grant DK41842 for J .D.B.).
Su p p or t in g In for m a t ion Ava ila b le: Analytical HPLC
chromatograms of compounds 7-9. This material is available
free of charge via the Internet at http://pubs.acs.org.
Refer en ces
(1) Braverman, L. E.; Utiger, R. D.; Werner, S. C.; Ingbar, S. H.
Werner and Ingbar’s the Thyroid: a Fundamental and Clinical
Text, 6th ed.; Lippincott: Philadelphia, PA, 1991; Chapter xxiii,
p 1365.
(2) Yen, P. M. Physiological and molecular basis of thyroid hormone
action. Physiol. Rev. 2001, 81, 1097-1142.
(3) Lazar, M. A. Thyroid hormone receptors: multiple forms,
multiple possibilities. Endocr. Rev. 1993, 14, 184-193.
(4) Forrest, D.; Hanebuth, E.; Smeyne, R. J .; Everds, N.; Stewart,
C. L.; et al. Recessive resistance to thyroid hormone in mice
lacking thyroid hormone receptor beta: evidence for tissue-
specific modulation of receptor function. EMBO J . 1996, 15,
3006-3015.
(5) Forrest, D.; Erway, L. C.; Ng, L.; Altschuler, R.; Curran, T.
Thyroid hormone receptor beta is essential for development of
auditory function. Nat. Genet. 1996, 13, 354-357.
(6) Fraichard, A.; Chassande, O.; Plateroti, M.; Roux, J . P.; Trouillas,
J .; et al. The T3R alpha gene encoding a thyroid hormone
receptor is essential for post-natal development and thyroid
hormone production. EMBO J . 1997, 16, 4412-4420.
(7) Gauthier, K.; Chassande, O.; Plateroti, M.; Roux, J . P.; Legrand,
C.; et al. Different functions for the thyroid hormone receptors
TRalpha and TRbeta in the control of thyroid hormone produc-
tion and post-natal development. EMBO J . 1999, 18, 623-631.
(8) Ng, L.; Hurley, J . B.; Dierks, B.; Srinivas, M.; Salto, C.; et al. A
thyroid hormone receptor that is required for the development
of green cone photoreceptors. Nat. Genet. 2001, 27, 94-98.
(9) Chiellini, G.; Apriletti, J . W.; Yoshihara, H. A. I.; Baxter, J . D.;
Ribeiro, R. C. J .; et al. A high-affinity subtype-selective agonist
ligand for the thyroid hormone receptor. Chem. Biol. 1998, 5,
299-306.
(10) Boyd, G. S.; Oliver, M. F. The effect of certain thyroxine
analogues on the serum lipids in human subjects. J . Endocrinol.
1960, 21, 33-43.
(11) Ballantyne, F. C.; Epenetos, A. A.; Caslake, M.; Forsythe, S.;
Ballantyne, D. The composition of low-density lipoprotein and
very-low-density lipoprotein subfractions in primary hypothy-
roidism and the effect of hormone-replacement therapy. Clin.
Sci. (London) 1979, 57, 83-88.
(12) Hansson, P.; Valdemarsson, S.; Nilssonehle, P. Experimental
Hyperthyroidism in MansEffects on Plasma-Lipoproteins, Li-
poprotein-Lipase and Hepatic Lipase. Horm. Metab. Res. 1983,
15, 449-452.
(13) Gomberg-Maitland, M.; Frishman, W. H. Thyroid hormone and
cardiovascular disease. Am. Heart J . 1998, 135, 187-196.
(14) Klein, I.; Ojamaa, K. Mechanisms of disease: thyroid hormone
and the cardiovascular system. N. Engl. J . Med. 2001, 344, 501-
509.
J M0301181