Design, syntheses, and structure-activity relationships of indan derivatives as endothelin antagonists; new lead generation of non-peptidic antagonist from peptidic leads

Article abstract of DOI:10.1016/S0968-0896(00)00241-8

A new lead generation of non-peptidic ET_A antagonists from two peptidic ET_A-selective ones, BQ-123 and FR139317, was performed. Using computer assisted molecular modeling, a putative pharmacophore was constructed from the superpositi

Full text of DOI:10.1016/S0968-0896(00)00241-8

Bioorganic & Medicinal Chemistry 9 (2001) 255±268
Design, Syntheses, and Structure±Activity Relationships of Indan
Derivatives as Endothelin Antagonists; New Lead Generation of
Non-peptidic Antagonist from Peptidic Leads
Hiroshi Morimoto, Chiaki Fukushima, Rikako Yamauchi, Tomoko Hosino,
Kohei Kikkawa, Kosuke Yasuda and Koichiro Yamada*
Discovery Research Laboratory, Tanabe Seiyaku Co., Ltd, 2-2-50 Kawagishi, Toda-shi, Saitama 335-8505, Japan
Received 30 May 2000; accepted 26 August 2000
AbstractÐA new lead generation of non-peptidic ETA antagonists from two peptidic ETA-selective ones, BQ-123 and FR139317,
was performed. Using computer assisted molecular modeling, a putative pharmacophore was constructed from the superposition of
the reported three-dimensional structure of the cyclic peptide BQ-123 and a presumable b-turn active conformation of the linear
peptide FR139317 formed by an intramolecular hydrogen bond. According to this model, a new series of indan derivatives were
designed and synthesized. Among these, 5-isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-thienyl)-1-indancarboxylic acid (1b)
showed a moderate ETA antagonistic activity (IC50=28 mM). # 2001 Elsevier Science Ltd. All rights reserved.
Introduction
Intending to ®nd non-peptidic compounds from pep-
tides, there have been numerous reports of the peptido-
mimetic approaches using nucleic templates, which
amino acid side chains were arranged around, based on
the hypothesis that the geometry of the side chain sub-
stituents in the parent peptides is critically important for
biological activities.7 Regarding the peptidic antagonists
BQ-123 and FR139317, we focused on the structure and
the di€erence of the activity. The similarity of the sub-
stituents between BQ-123 and FR139317 gave us a
hypothesis that the active conformation of FR139317
was in the b-turn structure with a possible intramole-
cular hydrogen bond between urea CO and d-pyr-
idylalanine (Pya) NH. The three-dimensional (3-D)
structure of the cyclic peptide BQ-123 has been studied
in detail,8 and the NMR conformational analysis in
solution was reported. It was proved that BQ-123 is
stabilized by two intramolecular hydrogen bonds.9 As
for the activity for ETA receptor (porcine aortic mem-
brane), FR139317 shows higher anity than BQ-123
(FR139317, IC50=0.53 nM and BQ-123, IC50=22 nM).
Investigating the reason for the di€erence, we super-
imposed the main chain of the putative b-turn structure
of FR139317 and one of the most stable conformations
of BQ-123 reported using computer assisted molecular
modeling. The superposition is shown in Figure 2 (left
side). Indeed almost all the side chain substituents
overlapped, but the location and direction of the car-
boxylic acids were di€erent. Then, we constructed a
Endothelin-1 (ET-1) was ®rst isolated from cultured
porcine vascular endothelial cells in 1988 and has been
found to be the most potent and long-lasting vasocon-
strictor peptide.1 ET has been implicated in the patho-
genesis of a number of disease states including renal
failure, pulmonary hypertension, cerebral ischemia,
vasospasm, endotoxic shock, and congestive heart fail-
ure.2 Inhibition of the biological actions of ET has been
suggested to o€er potential utility in the treatment of
these diseases. In the early 1990s, ETA-selective peptidic
antagonists such as cyclic peptide BQ-1233 and linear
peptide FR1393174 were disclosed. They have made
numerous contributions to clarifying the roles of ETs in
the physiological and pathophysiological processes.5
However, these peptidic antagonists have poor oral
activity and very short duration of action, probably due
to their low metabolic stability in vivo. For these, they
are unsuitable for therapeutic uses in chronic diseases in
which ETs are involved. To overcome these problems,
orally active and much durable non-peptidic antagonists
have been desired. A number of non-peptidic antago-
nists have been disclosed and the e€ects for the disease
states have been investigated.6
*Corresponding author. Discovery Research Laboratory, Tanabe
Seiyaku Co., Ltd, 2-2-50 Kawagishi, Toda-shi, Saitama 335-8505,
Japan.
0968-0896/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(00)00241-8

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H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
putative pharmacophore that might be important for
ET antagonistic activities taking into consideration that
the di€erence of the anity of these antagonists would
depend on the location of the carboxylic acid.
Methods
Molecular modeling of BQ-123 and FR139317
The initial structure of BQ-123 was constructed based
on the reported solution structure determined by
NMR.8b The structure was then energy minimized with
distance constraints between two pairs of hydrogen-
bonded atoms, so that it could match the g-turned
NMR structure. The initial structure of FR139317 was
constructed to overlapthe main chain of BQ-123, and
the structure was energy minimized with a distance
constraint between the oxygen of the urea CO and the
hydrogen of the d-Pya NH which were likely to make a
hydrogen bond.
According to the pharmacophore, seeking a new class of
non-peptidic ET antagonists, we investigated some
skeletons by computer assisted molecular design. Among
these, an indan template was selected and some most
promising side chain substituents were attached on it.
We report herein the design and the syntheses of the
indan derivatives and their anities for ETA receptor.
The whole shape of FR139317 after the energy mini-
mization was very similar to that of BQ-123. Their
superposition is shown in Figure 2 (left side). In this
model, homopiperidine ring, l-Leu residue, d-Trp(Me)
residue, and pyridine ring of FR139317 match with d-Val
residue, l-Leu residue, d-Trpresidue, and l-Pro residue
of BQ-123, respectively. However, the carboxylic acids
of FR139317 and BQ-123 did not overlapcompletely.
Construction of pharmacophore model
On the supposition that the relative geometry of the side
chain residues of these peptidic antagonists was the
most important for the interaction with ET receptor in
these peptidic antagonists, a pharmacophore model was
constructed from the obtained superposition. As shown
in Figure 2 (right side), the carboxylic acid, aromatic ring,
and two hydrophobic groups were regarded as the most
important components for the pharmacophore, and the
approximate distances among these groups were calcu-
lated. At this point, the area of the carboxylic acid was
estimated as large for the reason described above. The
area occupied by pyridine ring of FR139317 and l-Pro
of BQ-123 was omitted because the Pro residue of BQ-
123 just played a role to ®x conformation as the back-
bone ring of the peptide.9
Figure 1. Structures of peptidic ETA antagonists BQ-123 and
FR139317. The two reported hydrogen bonds in BQ-123 are indicated
with dashed lines, and the possible hydrogen bond in FR139317 is
indicated with an arrow.
Figure 2. A putative pharmacophore model derived from a superposition between BQ-123 (dashed line) and FR139317 (solid line).

H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
257
Design of indan derivatives
duced between indan and the residues at 6-position. In
addition, it was found that cis-indan derivatives ®t the
pharmacophore more suitably than trans ones. As the
area occupied by the carboxylic acid could not be ®xed
in a small range in the pharmacophore, the number of
the methylene which linked the carboxylic acid moiety to
the indan skeleton varied from 0 to 2 (Figure 3).
By the molecular modeling study of the peptides, rela-
tively rigid bicyclic rings such as indan, 2-indolinone,
and tetralin were thought to be suitable as a nucleus for
the pharmacophore because those templates could ®t
the size and shape of the peptidic backbone. From pre-
liminary conformational analysis and for facility in
synthesis, we selected indan as a nucleus, in which the
proper substituents were introduced onto 1-, 3-, 5-, and
6-positions. For BQ-518, having 2-thienyl group instead
of the Val residue of BQ-123, reported to be a more
potent ETA-selective antagonist than BQ-123,9 we
adopted 2-thienyl group as a substituent at 3-position.
Adjusting the distances among each residue and making
it easy to modify the residues synthetically, spacers such
as amide bond, ether bond, and methylene were intro-
Conformational analysis of indan derivatives
When the designed cis-indan derivative 1a (n=0, X=O,
R1=isopropyl, and R2=1-methylindol-2-ylmethyl; cis-
form) was superimposed on the putative conformation
of FR139317, we found that the four residues described
above occupied nearly the same area as its residues did
(Fig. 4). The location of the carboxylic acid in the
modeled indan derivative, with n=0, was the nearest to
that in the putative conformation of FR139317. The
method of the superposition in Figure 4 was as follows:
(1) an initial structure of cis-form of 1a was constructed,
(2) conformational analysis was performed (computa-
tional details are described in the Experimental section),
and (3) one of the local minimum conformations which
could ®t to the pharmacophore was superimposed on
the conformation of FR139317 constructed above.
Chemistry
Synthesis of indancarboxylic acid derivatives (n=0). The
synthetic route to 1b is shown as a representative in
Scheme 1. Diethyl (3-methoxyphenyl)malonate (2) was
treated with benzyl 2-bromoacetate in the presence of
NaH, followed by catalytic hydrogenation to a€ord 3 in
82% yield. The palladium-catalyzed cross-coupling of
tributyl-2-thienyltin with the acid chloride derived from
3 a€orded the desired ketone (4) in 95% yield. The
cyclization with polyphosphoric acid of 4 followed
by NaBH4±TFA reduction10 of the resulting indenes
Figure 3. Indan derivatives designed on the basis of the putative
pharmacophore.
Figure 4. A superposition between the indan derivative 1a (dashed line) and FR139317 (solid line).

258
H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
a€orded a 5:1 mixture of the indan derivatives 5 and 6.
The ratio of the desired isomer (5) was improved up to
27:1 by single recrystallization from EtOH±H2O of the
crude mixture (71% yield from 4). BBr3 treatment of 5
followed by decarboxylation and esteri®cation furn-
ished the compound 7 (the ratio of cis:trans isomer=1:1
assigned by NMR spectrum)11 in 84% yield. Nitration
of 7 with aq HNO3 in AcOH gave a mixture of the 5-
and 7-nitro derivatives, which was separated by silica
gel column chromatography to a€ord 8 and 9 in 48%
and 47% yields, respectively. Due to high acidity of the
benzylic proton by both electron-withdrawing groups
(i.e., NO2 and carboxylic acid), 8 and 9 might be in
equilibrium between cis and trans isomers. Catalytic
hydrogenation of NO2 groupof 8 over Pd/C in the pre-
sence of isobutyric anhydride gave the N-amides 10 in
good yield. Finally, alkylation of phenolic hydroxyl
groupof 10 with 1-(chloromethyl)naphthalene, then
followed by alkaline hydrolysis of the ester group, fur-
nished the target compound 1b as a mixture of cis and
Scheme 1. Synthesis of indancarboxylic acid derivatives (n=0). (a) BrCH2CO2CH2Ph, NaH; (b) H2, Pd/C (82% in 2 steps); (c) (COCl)2; (d) tributyl-
2-thienyltin, PdCl2(PPh3)2 (95% in 2 steps); (e) PPA; (f) NaBH4, TFA (71% in 2 steps); (g) recrystallization from EtOH±H2O; (h) BBr3; (i) re¯ux in
xylene±dioxane; (j) HCl±MeOH (84% in 3 steps); (k) aq HNO3, AcOH (8: 48%, 9: 47%); (l) H2, Pd/C, (i-PrCO)2O (93%); (m) 1-(chloro-
methyl)naphthalene, K2CO3 (43%); (n) aq NaOH±EtOH (78%).
Scheme 2. Introduction of benzyl groupto compound 8. (a) PhCH2Br, K2CO3 (13: 11%, 14: 25%).

H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
259
trans isomers. As shown in Scheme 2, alkylation of
followed by hydrolysis of the ester groupled to the tar-
get compound 1l.
nitrophenol 8 with benzyl chloride in the presence of
K2CO3 a€orded a mixture of 13 and 14 instead of 12,
due to high acidity of the benzylic proton. The synthesis
of the 6-(1-methylindol-2-ylmethoxy)indan derivative
(1a), designed at ®rst, from 10 was suspended, because
the alkylating agents such as 1-methylindol-2-ylmethyl
chloride or (1-methylindol-2-ylmethyl)methanesulfon-
ate12 could not be obtained due to their instability. The
other indancarboxylic acid derivatives (1c±p) (see Table
1) were synthesized by the same manner described
above.
Indanpropanoic acid derivative (n=2). The indanpropa-
noic acid derivative (1m, cis:trans isomers=1:1) was
prepared from the aldehyde 18 as a starting material by
using Horner±Emmons ole®nation, followed by reduc-
15
tion of the ole®n 21 with NiCl2±NaBH4 system
(Scheme 4).
Indancarboxylic acid carba-analogues (n=0, X=C). In
order to investigate the substituent e€ects at 6-position
of 1b, we next attempted to synthesize the carba-
analogues (1n, 1o and 1p). The hydroxyl groupof
10 was converted to the corresponding O-tri-
¯uoromethanesulfonate, followed by the palladium-
catalyzed cross-coupling reaction with tributyl-1-naph-
thylethynyltin16 in the presence of LiCl a€orded the
compound 23, which was converted into the targeted 1n
by alkaline hydrolysis in good yield. Partial reduction
of 23 with palladium/carbon catalyst under H2
atmosphere gave a mixture of the cis-ole®n derivative
24 and the saturated compound 25, which were
separated by chromatography on silica gel to a€ord
24 and 25 in 40% and 51% yields, respectively. The
obtained methyl ester derivatives were hydrolyzed to
the corresponding carboxylic acids 1o and 1p
(Scheme 5).
Synthesis of indanacetic acid derivative (n=1). In order
to synthesize the indan acetic acid derivative (1l),
Arndt±Eistert reaction was ®rst applied to the car-
boxylic acid 1b, but the corresponding diazoketone was
not obtained. Therefore, we next attempted to synthe-
size 1l via Wittig reaction of the aldehyde 18 with (1,3-
dithian-2-yl)triphenylphosphonium chloride13 as shown
in Scheme 3. Acidic hydrolysis of 8 followed by B2H6
reduction of NO2 and CO2H groups gave the amino-
alcohol 15, which was acylated by isobutyric anhydride
to a€ord 16 in 43% yield from 8. O-alkylation of 16
with 1-(chloromethyl)naphthalene chloride followed by
Swern-oxidation gave the desired aldehyde 18, which
was converted directly to the dithian derivative 19 due
14
to its instability. HgCl2 treatment of 19 in methanol
Table 1. Structure±activity relationshipof indan derivatives 1
Compound
R1
R2
n
cis:trans
mp( ꢀC)
mol. formula
IC50 (mM)a
.
b
c
d
e
f
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
1-naphthyl-CH2OÐ
2-naphthyl-CH2OÐ
PhCH2OÐ
PhCH2CH2OÐ
Ph2CHOÐ
0
0
0
0
0
1:1.7
1:1.7
1:2
1:1.8
1:1.7
190±192
195±199
182±185
203±210
157±164
C29H27NO4S 0.2H2O
28
>100
>100
>100
>100
.
C29H27NO4S 0.2H2O
C25H25NO4S
C26H27NO4S
.
C31H29NO4S 0.5H2O
g
i-Pr
0
1:2
178±181
C27H27NO4S
60
h
i
j
k
l
m
i-Pr
i-Pr
i-Bu
t-Bu O
i-Pr
PhCOCH2OÐ
OH
1-naphthyl-CH2OÐ
1-naphthyl-CH2OÐ
1-naphthyl-CH2OÐ
1-naphthyl-CH2OÐ
0
0
0
0
1
2
1:1.6
1:1.1
1:1.7
1:1.7
1:2.4
1:1
188±190
(amorphous)
184±188
176±178 (dec)
177±180
162.5±166
C26H25NO5S
C18H19NO4S
.
C30H29NO4S 0.1H2O
80
>100
80
>100
>100
>100
C30H29NO5S
.
C30H29NO4S 0.2H2O
.
C31H31NO4S 0.1H2O
i-Pr
n
i-Pr
0
1:1.7
201.5Ð
C30H25NO3S
70
b
.
C30H27NO3S 0.3H2O
o
p
i-Pr
i-Pr
0
0
(amorphous)
229±230
52
75
.
C30H29NO3S 0.3H2O
1:2
aInhibition of [125I]ET-1 binding in vitro to porcine aortic membrane ETA receptors.
bNot determined.

260
H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
All the compounds synthesized were obtained as
inseparable mixtures of cis and trans forms neither by
recrystallization nor chromatography on silica gel,
which were therefore subjected to ETA receptor binding
assay as such. The con®gurations of cis-trans isomers
Results
Receptor binding was evaluated by concentration-
dependent inhibition of the binding of 125I-labeled ET-1
to porcine aortic membrane known to contain ETA
receptors. The structure±activity relationships of the
indan derivatives synthesized are shown in Table 1.
1
were presumed by the analogy of H NMR spectrum
with that of the compound 7.11
.
Scheme 3. Synthesis of indanacetic acid derivative (n=1). (a) aq HCl±dioxane; (b) NaBH4, BF3 OEt2; (c) (i-PrCO)2O, pyridine; (d) K2CO3 (43%
from 8); (e) 2-(chloromethyl)naphthalene, K2CO3, NaI (87%); (f) TFAA, Et3N; (g) (1,3-dithian-2-yl)triphenylphosphonium chloride, NaH (45%
from 17); (h) HgCl2, H2O, THF±MeOH (69%); (i) aq NaOH±EtOH (95%).
.
Scheme 4. Synthesis of indanpropanoic acid derivative (n=2). (a) Ph3PˆCHCOOEt (73%); (b) NiCl2 6H2O, NaBH4; (c) 2-(chloro-
methyl)naphthalene, K2CO3, NaI (46% in 2 steps); (d) aq NaOH±EtOH (94%).

H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
261
Among these, the compound 1b bearing 1-naphthyl-
methyl groupat 6-position showed moderate anity for
ETA receptor with an IC50 value of 28 mM. Never-
theless, this activity was much lower than those of BQ-
123 and FR139317. Substitutions of R2 groupto 2-
naphthylmethyl (compound 1c) or other groups (com-
pounds 1d±h) reduced the activity. Substitutions from
isopropyl to tert-butyl or tert-butyloxy groups in R1
group(compounds 1j, k), elongation of methylene at
1-position [1l (n=1), m (n=2)], and conversion to the
carba-analogues at 6-position (1n±p) also lowered the
activity compared to 1b.
Among them, the derivative 1b bearing carboxylic acid,
2-thienyl, isobutyrylamino, and 1-naphthylmethyloxy
groups at 1-, 3-, 5-, and 6-positions, respectively,
appeared the highest anity for the receptor.
Murugesan, N. et al.7d and Diguarher, T. L. et al.7e
reported designs and syntheses of ETA antagonists
using dibenzodiazepine and sugar as sca€olds respec-
tively to support appropriate side-chains which mimic
BQ-123. The dibenzodiazepine-10-acetic acid deriva-
tives showed moderate activity (Ki=7 mM for ETA
receptor) but the glucose and allose derivatives showed
no signi®cant binding. The hydrophilic main chain with
hydrogen bondings of the peptidic antagonists might
play an important role for the anity for the receptor.
While we were studying the indan compounds, Ohlstein,
E. H. et al. reported the results of their indan-2-car-
boxylic acid derivatives SB 20967017a and SB 21724217b
independently. But the relationships of our indan deri-
vatives to those remain unclear.
In functional assay, 1b suppressed ET-1-induced con-
traction in the isolated rat aorta (endothelium denuded;
data were not shown); however, it reduced K+-induced
contraction of the same preparation as well.
Discussion
Aiming to ®nd orally active and much durable non-
peptidic antagonists, design and syntheses of a new ser-
ies of indan derivatives were performed.
Although the most active compound 1b was proved not
to be speci®c in the functional assay, we successfully
developed non-peptidic ETA receptor antagonists from
peptides. Since the activities of these indan derivatives
in the micromolar range were not enough for thera-
peutic use, further modi®cations of the template, the
residue, and the spacer will be necessary for increasing
the activity.
We were interested in the similarity of the side chains
between BQ-123 and FR139317 (CO2H, indole, and
isopropyl groups) and hypothesized that the active con-
formation of the linear peptide FR139317 was also the
turned one by the possible intramolecular hydrogen
bond between urea CO and d-Pya NH. According to
this hypothesis, we performed a computer assisted
molecular modeling as shown in Figure 1, constructed a
putative pharmacophore model, and designed indan
derivatives to be matched to this model. We selected the
rigid indan as a suitable template to ®x the residues at
the proper areas. The indan derivatives synthesized
showed moderate ETA receptor binding activities.
Experimental
All melting points were determined on a Buchi 535
digital melting point apparatus and are uncorrected.
Infrared (IR) spectra were taken on an Analect RFX-65
1
or an Analect FX-6200 FT-IR spectrophotometer. H
NMR spectra were recorded on a JEOL JNM-FX200, a
Scheme 5. Synthesis of indancarboxylic acid carba-analogues (n=0, X=C). (a) Tf2O, Et3N; (b) LiCl, PdCl2(PPH3)2, tributyl-1-naphthylethynyltin
(77% in 2 steps); (c) aq NaOH±EtOH (92%); (d) H2, Pd/C (24: 40%, 25: 51%); (e) aq NaOH±EtOH (76%); (f) aq NaOH±EtOH (72%).

262
H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
Varian Gemini 300, or a JEOL JNM-GSX400 spec-
trometer. Mass spectra were recorded on a JEOL
JMS-HX100 mass spectrometer. Elemental analyses
were performed on a Perkin±Elmer 2400 C, H, N ana-
lyzer and a YOKOGAWA IC 7000S ion chromato-
graphic analyzer with oxygen ¯ask combustion for sulfur
atom, and were within Æ0.3% of the calculated values.
Diethyl 3-methoxyphenyl-2-thenoylmethylmalonate (4).
A solution of 3 (100.0 g, 0.308 mol) in dry toluene (1 L)
with (COCl)2 (80 mL, 0.92 mol) was stirred at 80 ꢀC for
2.5 h. The volatile was removed under reduced pressure,
and the resulting oil was chased with toluene twice. A
mixture of the obtained oil (acid chloride), tributyl-2-
thienyltin (172 g, 0.462 mol), and PdCl2(PPh3)2 (10.8 g,
15.4 mmol) in dry dioxane (2 L) was degassed three
times under argon and re¯uxed for 20 h. 10% aq KF
(1 L) was added on an ice bath, and the whole was stir-
red at room temperature for 1 h. Insoluble material was
removed o€ through Celite and washed with H2O and
EtOAc. The aqueous layer of the ®ltrate and the wash-
ings were extracted with EtOAc. The extracts were
washed with H2O, aq NaHCO3, and brine, dried over
anhydrous MgSO4, treated with an active charcoal, and
concentrated in vacuo. The residue was recrystallized
from i-Pr2O to give colorless crystalline powder 4, and
the mother liquor was concentrated and puri®ed by
silica gel column chromatography (hexane:EtOAc, 4:1±
3:1, v/v) to a€ord a colorless crystalline powder 4 (total
114.4 g, 95%): mp79.5±80.5 ꢀC; 1H NMR (CDCl3,
300 MHz) d 6.8±7.8 (7H, m), 4.21±4.33 (4H, m), 3.95
(2H, s), 3.78 (3H, s), 1.25 (6H, t, J=7.1 Hz); IR (Nujol)
cmÀ1 3470, 3090, 1735, 1685, 1600, 1585, 1520, 1490;
EI±MS m/z 390 (M+), 345, 111.
Molecular modelings
All molecular modeling works were performed with
SYBYL 5.518 running on a Silicon Graphics IRIS 4D/
80 workstation.
Geometries of the molecules were optimized by using
MAXIMIN2 implemented in SYBYL with the TRIPOS
force ®eld. For the coulombic electrostatic energy term,
atomic charges were derived from MNDO calculations
with the semiempirical molecular orbital calculation
package MOPAC 5.01,19 and the dielectric constant was
set to 1r (i.e., interatomic distance dependent) so that
the e€ect of the solvent was included implicitly. The
minimization calculations were terminated when the
RMS change from one iteration to the next was below
0.05 kcal/mol A.
Conformations of the indan derivative 1a were gener-
ated with the SYBYL/Systematic Search routine. Seven
rotatable bonds (one for the carboxyl group, one for the
thienyl group, two for the group on the 5-position, three
Diethyl 6-methoxy-3-(2-thienyl)-1,1-indandicarboxylate
(5) and diethyl 4-methoxy-3-(2-thienyl)-1,1-indandicar-
boxylate (6). To pre-heated polyphosphoric acid
(>75% purity, 2.0 kg) was added 4 (123.1 g, 0.315 mol)
in small portions at 75±80 ꢀC over 10 min. The solution
was stirred at 75±83 ꢀC for 1 h, poured into ice water
(2 L), and extracted with EtOAc. The extracts were
washed with H2O, aq NaHCO3, and brine, dried over
anhydrous Na2SO4, and concentrated in vacuo to a€ord
a brown oil (117.4 g). To a stirred suspension of NaBH4
(22.2 g, 0.587 mol) in dry CH2Cl2 (1 L) was added
CF3COOH (158 mL, 2.06 mol) dropwise over 30 min
with vigorous stirring at 3±15 ꢀC on an ice bath, and the
mixture was stirred at 22 ꢀC for 1 h. A solution of the oil
obtained above (109.4 g, 0.294 mol) in CH2Cl2 (0.4 L)
was added at 7±10 ꢀC over 5 min, and the mixture was
stirred at 7±25 ꢀC for 2 h. H2O (1 L) was added slowly
on an ice bath, and the mixture was stirred at room
temperature for 1 h. The aqueous layer was extracted
with CHCl3, and the extracts were washed with H2O, aq
NaHCO3, and brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The resulting oil (a mixture
of 5 and 6 (5:1)) was crystallized from EtOH (190 mL)±
H2O (40 mL) to a€ord a mixture of 5 and 6 (27:1) as a
brown solid (81.1 g, 71%): mp65.5±67.5 C; H NMR
(CDCl3, 300 MHz) 5 d 7.19 (1H, dd, J=1.2, 5.0 Hz),
7.16 (1H, d, J=2.5 Hz), 7.01 (1H, dd, J=1.0, 8.4 Hz),
6.95 (1H, dd, J=3.5, 5.0 Hz), 6.90±6.93 (1H, m), 6.85
(1H, dd, J=2.5, 8.5 Hz), 4.78 (1H, br t, J=8.3 Hz),
4.10±4.35 (4H, m), 3.82 (3H, s), 3.33 (1H, dd, J=7.6,
13.3 Hz), 2.63 (1H, dd, J=9.1, 13.3 Hz), 1.28 (3H, t,
J=7.0 Hz), 1.26 (3H, t, J=7.0 Hz); 6 d 7.32 (1H, t,
J=8.1 Hz), 7.20 (1H, dd-like, J=1.0, 8.0 Hz), 7.09 (1H,
dd, J=1.5, 5.3 Hz), 6.81±6.88 (2H, m), 6.66 (1H, dt,
J=3.5, 1.0 Hz), 4.85 (1H, dd, J=4.5, 9.0 Hz), 4.05±4.34
(4H, m), 3.69 (3H, s), 3.34 (1H, dd, J=8.7, 13.8 Hz),
ꢀ
for the groupon the 6-position) were scanned with 30
increments within a 0±359ꢀ interval. A family of con-
formations which could ®t to the pharmacophore was
selected by using distances between pharmacophoric
groups, then the geometry of the lowest energy
conformation among the family was optimized.
2,2-Bis(ethoxycarbonyl)-2-(3-methoxyphenyl)propionic
acid (3). To a stirred solution of diethyl 3-methoxy-
phenylmalonate (20.0 g, 75.1 mmol) in dry DMF
(200 mL) was added 60% NaH in mineral oil (3.45 g,
90.1 mmol) on an ice bath. After 10 min, benzyl bro-
moacetate (20.6 g, 90.1 mmol) was added. The mixture
was stirred at room temperature for 16 h, diluted with
H2O, acidi®ed with 10% aq HCl, and then extracted
with EtOAc. The extracts were washed with H2O and
brine, dried over anhydrous Na2SO4, and concentrated
in vacuo. The residue was puri®ed by silica gel column
chromatography (hexane:EtOAc, 10:1, v/v) to a€ord a
colorless oil. A solution of the obtained oil (benzyl
ester) in EtOH (250 mL) was hydrogenated over 10%
Pd/C (water content 50%) (5.0 g) under atmospheric
pressure at room temperature for 4 h. The catalyst was
®ltered o€ and the ®ltrate was concentrated in vacuo to
a€ord 3 as a colorless crystalline powder (20.0 g, 82%):
ꢀ
1
mp113.5±114.5 ꢀC; H NMR (CDCl3, 300 MHz) d 7.26
1
(1H, t, J=8.0 Hz), 6.93 (1H, t, J=2.0 Hz), 6.91 (1H,
ddd, J=0.9, 2.0, 8.0 Hz), 6.84 (1H, ddd, J=0.9, 2.0,
8.0 Hz), 4.28 (2H, dq, J=7.0, 11.0 Hz), 4.26 (2H, dq,
J=7.0, 11.0 Hz), 3.78 (3H, s), 3.37 (2H, s), 1.25 (6H, t,
J=7.1 Hz); IR (Nujol) cmÀ1 2780, 2660, 2580, 1745,
1720, 1715, 1610, 1585, 1495; EI±MS m/z 324 (M+),
278, 206, 178, 161, 133.

H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
263
2.79 (1H, dd, J=4.3, 13.8 Hz), 1.27 (3H, t, J=7.1 Hz),
1.16 (3H, t, J=7.1 Hz); IR (Nujol) cmÀ1 1750, 1725,
1610, 1580; EI±MS m/z 374 (M+), 300, 227.
4.09 (cis) (0.5H, dd, J=7.8, 10.4 Hz) and 4.21 (trans)
(0.5H, ddd, J=1.0, 4.1, 8.4 Hz), 3.84 (1.5H, s) and 3.77
(1.5H, s), 2.89±3.07 (1H, m) and 2.40±2.63 (1H, m); IR
(Neat) cmÀ1 3400±3000, 1740, 1735, 1630, 1585, 1540;
EI±MS m/z 319 (M+), 259, 213, 184. 9: 1H NMR
(CDCl3, 300 MHz) (cis:trans, 1:1) d 10.72 (0.5H, s) and
10.68 (0.5H, s), 7.34 (0.5H, d, J=8.5 Hz) and 7.31
(0.5H, d, J=8.5 Hz), 7.22 (0.5H, dd, J=1.2, 5.5 Hz) and
7.20 (0.5H, dd, J=1.2, 5.3 Hz), 7.11 (0.5H, dd, J=0.8,
8.5 Hz) and 7.10 (0.5H, d, J=8.7 Hz), 6.98 (0.5H, dd,
J=3.5, 5.1 Hz) and 6.95 (0.5H, dd, J=3.5, 5.1 Hz),
6.89±6.91 (0.5H, m) and 6.83±6.86 (0.5H, m), 4.75±4.82
(1H, m) and 4.58±4.69 (1H, m), 3.74 (1.5H, s) and 3.69
(1.5H, s), 2.29±3.19 (4H, m); IR (Neat) cmÀ1 3500±3000,
1735, 1615, 1590, 1535; EI±MS m/z 319 (M+), 301, 269.
Methyl 6-hydroxy-3-(2-thienyl)-1-indancarboxylate (7).
To a stirred solution of 5 (containing 1/28 of 6, 79.8 g,
0.123 mol) in dry CH2Cl2 (1.6 L) was added BBr3
(213.4 g, 0.852 mol) on an ice bath over 20 min. The
mixture was stirred at room temperature overnight, and
then poured into ice water (2 L). After removal of
CH2Cl2, the aqueous layer was extracted with EtOAc.
The extracts were washed with brine, dried over anhy-
drous Na2SO4, and concentrated in vacuo to a€ord a
brown oil. The oil was dissolved in a mixture of xylene
(1 L)±dioxane (0.5 L) and re¯uxed for 14 h. After
removal of the solvent, the residue was extracted three
times with aq NaHCO3. The aqueous layers were acid-
i®ed with 10% aq HCl and extracted with EtOAc. The
extracts were washed with H2O and brine, dried over
anhydrous Na2SO4, and concentrated in vacuo to a€ord
a dark brown oil. The obtained oil was treated with
28% HCl±MeOH (0.6 L) at re¯ux temperature for 2 h.
After removal of the solvent, the residual oil was diluted
with H2O and extracted with EtOAc. The extracts were
washed with H2O, aq NaHCO3, and brine, dried over
anhydrous Na2SO4, and concentrated in vacuo. The
residue was puri®ed by silica gel column chromato-
graphy (CHCl3:EtOAc, 20:1, v/v) to a€ord a dark green
oil 7 (48.8 g, 84%) as a diastereomixture (1:1): 1H NMR
(CDCl3, 300 MHz) cis-form d 6.70±7.25 (3H, m), 5.25
(1H, s), 4.55 (1H, dd, J=8.2, 19.1 Hz), 4.05 (1H, ddd,
J=1.1, 7.7, 8.8 Hz), 3.80 (3H, s), 2.88 (1H, dt, J=7.6,
12.8 Hz), 2.52 (1H, dt, J=9.9, 12.9 Hz); trans-form d
6.70±7.25 (3H, m), 5.23 (1H, s), 4.84 (1H, t, J=7.6 Hz),
4.15 (1H, dd, J=4.3, 8.3 Hz), 3.75 (3H, s), 2.98 (1H,
ddd, J=4.3, 7.9, 13.1 Hz), 2.40 (1H, ddd, J=7.3, 8.3,
13.1 Hz); IR (Neat) cmÀ1 3600±3100, 1735, 1710, 1610,
1590, 1490; EI±MS m/z 274 (M+), 214, 181, 131.
Methyl 6-hydroxy-5-isopropylamino-3-(2-thienyl)-1-in-
(800 mg,
dancarboxylate (10).
A
mixture of
8
2.51 mmol), isobutyric anhydride (627 mg, 3.77 mmol)
in THF (15 mL) was hydrogenated over 10% Pd/C
(water wet) (160 mg) under atmospheric pressure at
room temperature for 2 days. The catalyst was ®ltered
o€ and the ®ltrate was concentrated in vacuo. Puri®ca-
tion by silica gel column chromatography (hexane:EtOAc,
4:1, v/v) a€orded a yellow caramel 10 (836 mg, 93%):
1H NMR (CDCl3, 300 MHz) (cis:trans, 1:1) d 8.80
(0.5H, s) and 8.74 (0.5H, s), 7.49 (0.5H, br s) and 7.45
(0.5H, br s), 7.20 (0.5H, dd, J=1.2, 5.1 Hz) and 7.17
(0.5H, dd, J=1.2, 5.1 Hz), 7.04±7.07 (1H, m), 6.98
(0.5H, dd, J=3.5, 5.0 Hz) and 6.95 (0.5H, dd, J=3.5,
5.0 Hz), 6.92±6.95 (0.5H, m) and 6.84±6.87 (0.5H, m),
6.75 (0.5H, br s) and 6.74 (0.5H, d, J=1.0 Hz), 4.52 (cis)
(0.5H, dd, J=8.5, 9.3 Hz) and 4.80 (trans) (0.5H, t,
J=7.7 Hz), 4.03 (cis) (0.5H, t, J=8.9 Hz) and 4.12
(trans) (0.5H, dd, J=3.4, 8.5 Hz), 3.79 (1.5H, s) and
3.71 (1.5H, s), 2.47±2.63 (2H, m), 2.96 (0.5H, ddd,
J=3.6, 7.8, 13.1 Hz), 2.85 (0.5H, dt, J=7.6, 12.9 Hz),
2.53 (0.5H, dt, J=10.0, 13.0 Hz) and 2.36 (0.5H, dt,
J=8.2, 13.0 Hz), 1.25 (3H, d, J=7.1 Hz) and 1.24 (3H,
d, J=6.9 Hz); IR (Neat) cmÀ1 3500±2400, 1735, 1660,
1650, 1610; EI±MS m/z 359 (M+), 289, 230.
Methyl 6-hydroxy-5-nitro-3-(2-thienyl)-1-indancarboxy-
late (8) and methyl 6-hydroxy-7-nitro-3-(2-thienyl)-1-in-
dancarboxylate (9). To a suspension of 7 (50 mg,
0.182 mmol), acetic acid (0.5 mL), and CH2Cl2 (1.5 mL)
was added 60% aq HNO3 (19.1 mg, 0.182 mmol) in
acetic acid (0.5 mL) dropwise over 10 min at À33 to
À28 ꢀC. The mixture was stirred at À15 to À5 ꢀC for 1 h
then at 5 ꢀC for 1 h, diluted with EtOAc, and washed
with H2O and aq NaHCO3. The aqueous layer was
extracted with EtOAc, and the extracts were washed
with H2O and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. Separation on preparative TLC
(CHCl3:hexane, 1:1 v/v, three times) a€orded 8 (28 mg,
48%) and 9 (27 mg, 47%) both as yellow oils. In a case
of 0.169 mol scale, 8 was separated by silica gel column
chromatography in 28% yield. 8: 1H NMR (CDCl3,
300 MHz) (cis:trans, 1:1) d 10.70 (0.5H, s) and 10.70
(0.5H, s), 7.86 (0.5H, d, J=1.3 Hz) and 7.80 (0.5H, d,
J=1.5 Hz), 7.27 (0.5H, d, J=1.7 Hz) and 7.23 (0.5H, d,
J=1.0 Hz), 7.26 (0.5H, dd, J=1.3, 5.0 Hz) and 7.22
(0.5H, dd, J=1.2, 5.1 Hz), 7.02 (0.5H, dd, J=3.5,
5.0 Hz) and 6.98 (0.5H, dd, J=3.5, 5.1 Hz), 6.97±6.99
(0.5H, m) and 6.89±6.91 (0.5H, m), 4.57 (cis) (0.5H, dd,
J=8.5, 9.4 Hz) and 4.86 (trans) (0.5H, t, J=7.8 Hz),
Methyl 5-isopropylamino-6-(1-naphthylmethyloxy)-3-(2-
thienyl)-1-indancarboxylate (11b). To a stirred solution
of 10 (120 mg, 0.334 mmol) in dry DMF (3 mL) was
added 60% NaH in mineral oil dispersion (13.4 mg,
0.351 mmol) on an ice bath, and the mixture was stirred
at room temperature for 30 min. A solution of 1-
(chloromethyl)naphthalene (62 mg, 0.351 mmol) in dry
DMF (0.2 mL) was added, and the mixture was stirred
at room temperature for 20 h, diluted with 10% aq HCl,
and extracted with EtOAc. The extracts were washed
with H2O and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. Puri®cation by silica gel column
chromatography (hexane:EtOAc, 7:1, v/v) and follow-
ing trituration with hexane a€orded a light blue crys-
ꢀ
talline powder 11b (72 mg, 43%): mp144.0±150.0 C; 1H
NMR (CDCl3, 300 MHz) (cis:trans, 1:1.3) d 8.16 (cis)
(0.43H, s) and 8.22 (trans) (0.57H, s), 7.88±8.08 (3H, m),
7.64±7.72 (1H, broad), 7.45±7.59 (4H, m), 7.12±7.23
(2H, m), 6.87±6.97 (2H, m), 5.55 (2H, s), 4.61 (cis) (0.43
H, dd, J=8.0, 9.4 Hz) and 4.87 (trans) (0.57H, t,
J=7.5 Hz), 4.08 (cis) (0.43H, dd, J=8.2, 9.3 Hz) and

264
H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
4.20 (trans) (0.57H, dd, J=4.4, 8.3 Hz), 3.78 (cis) (1.3H,
s) and 3.73 (trans) (1.7H, s), 2.86±3.02 (1H, m), 2.39±
2.58 (1H, m), 2.09±2.22 (1H, m), 0.94±1.01 (6H, m); IR
(Nujol) cmÀ1 3300, 3180, 2720, 2670, 1730, 1660, 1610,
1600; EI±MS m/z 499 (M+), 288, 141.
5-Isopropylamino-6-(2-phenethyloxy)-3-(2-thienyl)-1-in-
dancarboxylic acid (1e). 2-Phenethylation of 10 and
subsequent alkaline hydrolysis of 11e a€orded 1e as
colorless needles: mp203±210 ꢀC; 1H NMR (CDCl3,
300 MHz) (cis:trans, 1:1.3) d 6.84±7.99 (11H, m), 4.57
(cis) (0.43H, dd, J=8.0, 9.2 Hz) and 4.84 (trans) (0.57H,
t, J=7.3 Hz), 4.23±4.36 (2H, m), 4.05 (cis) (0.43H, dd,
J=8.1, 9.4 Hz) and 4.16 (trans) (0.57H, dd, J=4.4,
8.3 Hz), 3.13 (2H, t, J=6.4 Hz), 2.84±2.99 (1H, m),
2.26±2.56 (2H, m), 1.14 (cis) (2.61H, d, J=6.9 Hz) and
1.13 (trans) (3.39H, d, J=6.9 Hz); IR (Nujol) cmÀ1
3300, 3200±2400, 1720, 1690, 1665; EI±MS m/z 449
(M+), 379, 275, 105. Anal. calcd for C26H27NO4S: C,
69.46; H, 6.05; N, 3.12; S, 7.13. Found: C, 69.48; H,
6.02; N, 2.90; S, 6.95.
5-Isopropylamino-6-(1-naphthylmethyloxy)-3-(2-thienyl)-
1-indancarboxylic acid (1b). A mixture of 11b (61 mg,
0.122 mmol) and 10% aq NaOH (2 mL) in EtOH
(2 mL)±THF (2 mL) was stirred at 0 ꢀC for 2 h and then
diluted with H2O. The aqueous layer was washed with
ether, acidi®ed with 10% aq HCl, and extracted with
EtOAc. The extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in
vacuo. Recrystallization from EtOAc±hexane a€orded
colorless needles 1b (46 mg, 78%): mp189.5±191.5 ꢀC;
1H NMR (CDCl3, 300 MHz) (cis:trans, 1:1.7) d 8.17
(cis) (0.37H, s) and 8.24 (trans) (0.63H, s), 6.87±8.08
(10H, m), 7.67 (cis) (0.37H, br s) and 7.69 (trans)
(0.63H, br s), 5.56 (1H, d, J=12 Hz), 5.52 (1H, d,
J=12 Hz), 4.63 (cis) (0.37H, t, J=8.7 Hz) and 4.89
(trans) (0.63H, t, J=7.6 Hz), 4.14 (cis) (0.37H, t,
J=8.2 Hz) and 4.24 (trans) (0.63H, dd, J=4.3, 8.1 Hz),
2.90±3.06 (1H, m), 2.40±2.63 (1H, m), 2.08±2.23 (1H,
m), 0.92±0.99 (6H, m); IR (Nujol) cmÀ1 3310, 3200±
2400, 1715, 1690, 1660, 1610, 1600; EI±MS m/z 485
(M+), 274, 141. Anal. calcd for C29H27NO4S (+0.2
H2O): C, 71.73 (71.20); H, 5.60 (5.65); N, 2.88 (2.86); S,
6.60 (6.55). Found: C, 71.20; H, 5.64; N, 2.82; S, 6.55.
6-Diphenylmethyloxy-5-isopropylamino-3-(2-thienyl)-1-
indancarboxylic acid (1f). Diphenylmethylation of 10
and subsequent alkaline hydrolysis of 11f a€orded 1f as
light brown needles: mp157±164 ꢀC; H NMR (CDCl3,
1
300 MHz) (cis:trans, 1:1.7) d 6.84±8.22 (16H, m), 6.20
(cis) (0.37H, s) and 6.19 (trans) (0.63H, s), 4.56 (cis)
(0.37H, t, J=8.6 Hz) and 4.83 (trans) (0.63H, t,
J=7.3 Hz), 3.96 (cis) (0.37H, t, J=8.5 Hz) and 4.05
(trans) (0.63H, dd, J=4.1, 7.8 Hz), 2.80±2.97 (1H, m),
2.30±2.53 (2H, m), 1.11±1.16 (6H, m); IR (Nujol) cmÀ1
3350, 3300±2400, 1715, 1695, 1675, 1655, 1590; EI±MS
m/z 511 (M+), 275, 230, 167. Anal. calcd for
C31H29NO4S (+0.5 H2O): C, 72.77 (71.52); H, 5.71
(5.81); N, 2.74 (2.69); S, 6.27 (6.15). Found: C, 71.69; H,
5.72; N, 2.56; S, 5.82.
5-Isopropylamino-6-(2-naphthylmethyloxy)-3-(2-thienyl)-
1-indancarboxylic acid (1c). 2-Naphthylmethylation of
10 and subsequent alkaline hydrolysis of 11c a€orded 1c
6-Cinnamyloxy-5-isopropylamino-3-(2-thienyl)-1-indan-
carboxylic acid (1g). Cinnamylation of 10 and sub-
sequent alkaline hydrolysis of 11g a€orded 1g as
colorless needles: mp178±181 ꢀC; 1H NMR (CDCl3,
300 MHz) (cis:trans, 1:2) d 6.85±7.90 (11H, m), 6.74
(1H, d, J=15.9 Hz), 6.41 (1H, dt, J=6.0, 15.9 Hz), 4.60
(cis) (0.33H, dd, J=8.1, 9.2 Hz) and 4.86 (trans) (0.67H,
t, J=7.3 Hz), 4.70±4.83 (2H, m), 4.08 (cis) (0.33H, dd,
J=8.2, 9.3 Hz) and 4.18 (trans) (0.67H, dd, J=4.4,
8.3 Hz), 2.85±3.02 (1H, m), 2.37±2.58 (2H, m), 1.22 (cis)
(2H, d, J=6.9 Hz) and 1.21 (trans) (4H, d, J=6.9 Hz);
IR (Nujol) cmÀ1 3300, 3200±2400, 1690, 1665, 1610,
1595; EI±MS m/z 461 (M+), 443, 371, 117. Anal. calcd
for C27H27NO4S: C, 70.26; H, 5.90; N, 3.03; S, 6.95.
Found: C, 70.27; H, 5.83; N, 2.79; S, 6.82.
as colorless needles: mp195±199 ꢀC; H NMR (CDCl3,
1
300 MHz) (cis:trans, 1:1.7) d 8.18 (cis) (0.37H, s) and
8.25 (trans) (0.63H, s), 7.12±7.91 (10H, m), 6.86±6.97
(2H, m), 5.22±5.33 (2H, m), 4.61 (cis) (0.37H, dd,
J=8.3, 9.3 Hz) and 4.88 (trans) (0.63H, t, J=7.4 Hz),
4.09 (cis) (0.37H, dd, J=8.1, 9.0 Hz) and 4.19 (trans)
(0.63H, dd, J=4.4, 8.2 Hz), 2.87±3.03 (1H, m), 2.38±
2.59 (2H, m), 1.16 (cis) (2.22H, d, J=6.9 Hz) and 1.16
(trans) (3.78H, d, J=6.9 Hz); IR (Nujol) cmÀ1 3320,
3200±2400, 1715, 1695, 1665, 1655, 1610, 1595; EI±MS
m/z 485 (M+), 274, 141. Anal. calcd for C29H27NO4S
(+0.2 H2O): C, 71.73 (71.20); H, 5.60 (5.65); N, 2.88
(2.86); S, 6.60 (6.55). Found: C, 71.03; H, 5.54; N, 2.84;
S, 6.66.
6-Benzyloxy-5-isopropylamino-3-(2-thienyl)-1-indancar-
boxylic acid (1d). Benzylation of 10 and subsequent
alkaline hydrolysis of 11d a€orded 1d as colorless
5-Isopropylamino-6-phenacyloxy)-3-(2-thienyl)-1-indan-
carboxylic acid (1h). Phenacylation of 10 and sub-
sequent alkaline hydrolysis of 11h a€orded 1h as faintly
gray needles: mp188±190 ꢀC; 1H NMR (CDCl3,
300 MHz) (cis:trans, 1:1.6) d 6.84±8.82 (11H, m), 5.93
(2H, s), 4.59 (cis) (0.38H, dd, J=8.1, 8.8 Hz) and 4.85
(trans) (0.62H, t, J=7.4 Hz), 4.06 (cis) (0.38H, dd,
J=8.7, 9.1 Hz) and 4.16 (trans) (0.62H, dd, J=4.4,
8.1 Hz), 2.84±3.01 (1H, m), 2.65 (1H, septet,
J=6.9 Hz), 2.36±2.56 (1H, m), 1.26 (6H, d, J=6.8 Hz);
IR (Nujol) cmÀ1 3400, 3350, 3200±2400, 1715, 1710,
1675, 1640, 1605; EI±MS m/z 463 (M+), 393, 343, 300,
274, 105. Anal. calcd for C26H25NO5S: C, 67.38; H,
5.44; N, 3.02; S, 6.92. Found: C, 67.39; H, 5.41; N,
2.82; S, 6.80.
ꢀ
1
needles: mp184±187 C; H NMR (CDCl3, 300 MHz)
(cis:trans, 1:2) d 8.16 (cis) (0.33H, s) and 8.23 (trans)
(0.67H, s), 6.86±7.84 (10H, m), 5.07±5.17 (2H, m), 4.61
(cis) (0.33H, t, J=8.7 Hz) and 4.87 (trans) (0.67H, t,
J=7.5 Hz), 4.08 (cis) (0.33H, t, J=8.7 Hz) and 4.19
(trans) (0.67H, dd, J=4.3, 8.2 Hz), 2.86±3.30 (1H, m),
2.37±2.58 (2H, m), 1.17 (cis) (2H, d, J=6.9 Hz) and 1.17
(trans) (4H, d, J=6.9 Hz); IR (Nujol) cmÀ1 3320, 3280,
3180, 1715, 1700, 1670, 1655, 1605, 1595, 1525; EI±MS
m/z 435 (M+), 365, 344, 274, 228. Anal. calcd for
C25H25NO4S: C, 68.94; H, 5.79; N, 3.22; S, 7.36. Found:
C, 68.76; H, 5.81; N, 3.19; S, 7.37.

H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
265
6-Hydroxy-5-isopropylamino-3-(2-thienyl)-1-indancar-
boxylic acid (1i). Alkaline hydrolysis of 10 a€orded 1i
as light brown amorphous powder: 1H NMR
(CDCl3+DMSO-d6, 300 MHz) (cis:trans, 1:1.1) d 9.37
(1H, br s), 6.85±8.70 (6H, m), 4.57 (cis) (0.48H, t,
J=8.8 Hz) and 4.82 (trans) (0.52H, t, J=7.7 Hz), 3.97
(cis) (0.48H, t, J=8.7 Hz) and 4.07 (trans) (0.52H, dd,
J=4.1, 8.1 Hz), 2.78±3.00 (1H, m), 2.29±2.68 (2H, m),
1.20 (3H, d, J=6.8 Hz), 1.20 (3H, d, J=6.8 Hz); IR
(Nujol) cmÀ1 3420, 3400±2400, 1705, 1665, 1645, 1610;
EI±MS m/z 345 (M+), 327, 275, 230. Anal. calcd for
C18H19NO4S: C, 62.59; H, 5.54; N, 4.05; S, 9.58. Found:
C, 62.36; H, 5.62; N, 3.96; S, 8.94.
NaHCO3, saturated with NaCl, and extracted three
times with EtOAc. The extracts were washed with brine,
dried over anhydrous Na2SO4, and concentrated in
vacuo to a€ord 15 as a light yellow solid. To a stirred
solution of the crude 15 in dry pyridine (30 mL) was
added isobutyric anhydride (1.64 g, 9.83 mmol) on an
ice bath. The mixture was stirred at room temperature
for 14 h and concentrated in vacuo. The residual oil was
treated with K2CO3 (5.00 g, 36.4 mmol) in MeOH
(50 mL) at room temperature for 6 h, diluted with H2O,
acidi®ed with 10% aq HCl, and then extracted with
EtOAc. The extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in
vacuo. The residue was puri®ed by silica gel column
chromatography (CHCl3:MeOH, 50:1±20:1, v/v) to
a€ord a light brown caramel 16 (1.39 g, 43% from 8):
1H NMR (CDCl3, 300 MHz) (cis:trans, 1:1) d 8.83
(0.5H, br s) and 8.81 (0.5H, br s), 7.58 (1H, br s) and
7.48 (1H, br s), 6.76±7.19 (5H, m), 4.51 (cis) (0.5H, t,
J=8.6 Hz) and 4.63 (trans) (0.5H, t, J=7.7 Hz), 3.87
(1H, d, J=5.7 Hz) and 3.67±3.80 (1H, m), 3.25±3.45
(1H, m), 1.95±2.81 (3H, m), 1.7±1.9 (1H, broad), 1.24
(6H, d, J=6.8 Hz); IR (Nujol) cmÀ1 3600±2400, 1660,
1610, 1520; EI±MS m/z 331 (M+), 300, 261, 230.
5-Isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-thi-
enyl)-1-indancarboxylic acid (1j). 1j was prepared in a
similar manner as for 1b starting from 8 using isovaleric
anhydride instead of ꢀisobutyric anhydride: colorless
1
needles; mp184±187.5 C; H NMR (CDCl3, 300 MHz)
(cis:trans, 1:1.7) d 6.84±8.24 (13H, m), 5.54 (1H, d,
J=11.0 Hz), 5.53 (1H, d, J=11.0 Hz), 4.63 (cis) (0.37H,
dd, J=8.3, 8.8 Hz) and 4.89 (trans) (0.63H, t,
J=7.5 Hz), 4.13 (cis) (0.37H, dd, J=8.1, 9.2 Hz) and
4.24 (trans) (0.63H, dd, J=4.3, 8.1 Hz), 2.89±3.05 (1H,
m), 2.40±2.62 (1H, m), 1.78±1.97 (3H, m), 0.74±0.80
(6H, m); IR (Nujol) cmÀ1 3340, 3200-2400, 1720, 1690,
1660, 1610, 1600, 1525; EI±MS m/z 499 (M+), 415, 274,
141. Anal. calcd for C30H29NO4S (+0.1 H2O): C, 72.12
(71.86); H, 5.85 (5.87); N, 2.80 (2.79); S, 6.42 (6.39).
Found: C, 71.75; H, 5.84; N, 2.73; S, 6.20.
5-Isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-thi-
enyl)-1-indanmethanol (17). A mixture of 16 (1.34 g,
4.04 mmol), 1-(chloromethyl)naphthalene (786 mg,
4.44 mmol), NaI (606 mg, 4.04 mmol), and K2CO3
(1.68 g, 12.1 mmol) in dry DMF (15 mL) was stirred at
room temperature for 8 h, acidi®ed with 10% aq HCl,
and extracted with EtOAc. The extracts were washed
with H2O and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. The residue was puri®ed by silica
gel column chromatography (CHCl3:MeOH, 50:1, v/v)
and recrystallized from THF±EtOAc to a€ord colorless
5-tert-Butoxycarboxamido-6-(1-naphthylmethyloxy)-3-
(2-thienyl)-1-indancarboxylic acid (1k). 1k was prepared
in a similar manner as for 1b starting from 8 using di-
tert-butyl dicarbonate instead of isobutyric anhydride:
colorless needles; mp176±178 ꢀC (dec); 1H NMR
(CDCl3, 300 MHz) (cis:trans, 1:1.7) d 6.86±8.08 (13H,
m), 4.47±5.57 (2H, m), 4.67 (cis) (0.37H, t, J=8.5 Hz)
and 4.85 (trans) (0.63H, t, J=7.4 Hz), 4.10 (cis) (0.37H,
t, J=8.6 Hz) and 4.21 (trans) (0.63H, dd, J=4.7,
8.2 Hz), 2.88±3.03 (1H, m), 2.33±2.60 (1H, m), 1.37 (cis)
(3.33H, s) and 1.38 (trans) (5.67H, s); IR (Nujol) cmÀ1
3370, 3300±2400, 1710, 1685, 1610, 1600, 1525, 1490;
EI±MS m/z 515 (M+), 459, 415, 141. Anal. calcd for
C30H29NO5S: C, 69.88; H, 5.67; N, 2.72; S, 6.22. Found:
C, 69.85; H, 5.69; N, 2.62; S, 5.97.
needles 17 (1.65 g, 87%): mp176.5±180.5 ꢀC; H NMR
1
(CDCl3, 300 MHz) (cis:trans, 1:1) d 7.88±8.22 (4H, m),
7.64±7.69 (1H, broad), 7.45±7.58 (4H, m), 7.10±7.19
(2H, m), 6.85±6.95 (2H, m), 5.56 (1H, d, J=11.0 Hz)
and 5.52 (1H, d, J=11.0 Hz), 4.72 (0.5H, t, J=7.3 Hz)
and 4.61 (0.5H, t, J=8.4 Hz), 3.93 (1H, t, J=6.0 Hz)
and 3.73±3.89 (1H, m), 3.45±3.57 (0.5H, m) and 3.33±
3.45 (0.5H, m), 1.51 (0.5H, t, J=6.0 Hz) and 1.46 (0.5H,
t, J=6.0 Hz), 0.94±1.00 (6H, m); IR (Nujol) cmÀ1 3310,
3110, 3060, 1665, 1610, 1600, 1530; EI±MS m/z 471
(M+), 440, 401, 330, 260, 141.
6-Hydroxy-5-isobutyrylamino-3-(2-thienyl)-1-indan-
methanol (16). A mixture of 8 (5.0 g, 15.7 mmol), 10%
aq HCl (50 mL), and dioxane (100 mL) was re¯uxed for
6 h. After removal of the solvent, the residue was
extracted with EtOAc. The extracts were washed with
H2O and brine, dried over anhydrous Na2SO4, treated
with an active charcoal, and concentrated in vacuo to
a€ord a yellow oil (4.96 g). To a stirred suspension of
NaBH4 (3.32 g, 98.3 mmol) in dry THF (100 mL) was
5-Isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-thi-
enyl)-1-indancarbaldehyde (18). To a stirred solution of
DMSO (0.79 mL, 11.1 mmol) in dry CH2Cl2 (20 mL)
was added (CF3CO)2O (1.26 mL, 8.92 mmol) dropwise
at À65 to À62 ꢀC, and the mixture was stirred at the
same temperature for 20 min. A solution of 17 (1.05 g,
2.23 mmol) in dry CH2Cl2 (20 mL)±DMSO (3 mL) was
added over 5 min at À62 to À57 ꢀC, and the mixture was
stirred at À65 ꢀC for 1 h. Triethylamine (1.86 mL,
13.4 mmol) was added dropwise over 1 min at À65 to
À60 ꢀC, and the mixture was stirred at À65 to À10 ꢀC
for 2.5 h. The reaction mixture was diluted with H2O
and extracted with CHCl3. The extracts were washed
with H2O and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo to a€ord a yellow semisolid 18
.
added BF3 (C2H5)2O (16 mL, 128 mmol) dropwise on an
ice bath, and the reaction mixture was stirred at 0 ꢀC for
1 h. A solution of the carboxylic acid obtained (3.0 g,
9.83 mmol) in dry THF (15 mL) was added dropwise
over 15 min on an ice bath, and the whole was stirred at
room temperature for 4 h. The reaction mixture was
poured into ice water (0.3 L), neutralized with aq

266
H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
(1.64 g), which was used without puri®cation due to its
instability.
0.94±1.00 (6H, m); IR (Nujol) cmÀ1 3300, 1715, 1695,
1660, 1610, 1600, 1530, 1495; EI±MS m/z 499 (M+),
429, 358, 141. Anal. calcd for C30H29NO4S (+0.2
H2O): C, 72.12 (71.60); H, 5.85 (5.89); N, 2.80 (2.78);
S, 6.42 (6.37). Found: C, 71.54; H, 5.82; N, 2.69; S,
6.14.
2-(5-Isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-thi-
enyl)indan-1-ylmethylene)-1,3-dithiane (19). To a stirred
suspension of (1,3-dithian-2-yl)triphenylphosphonium
chloride (2.95 g, 7.1 mmol) in dry THF (20 mL) was
added 60% NaH in mineral oil (243 mg, 6.36 mmol) at
room temperature, and the whole was stirred for 30 min.
H2O (0.3 mL) was added slowly to this mixture. After
5 min, a solution of crude 18 (520 mg, 0.707 mmol) in
dry THF (5 mL) was added, and then stirred at room
temperature for 14 h. The reaction mixture was diluted
with H2O and extracted with EtOAc. The extracts were
washed with H2O and brine, dried over anhydrous
Na2SO4, and concentrated in vacuo. The residue was
puri®ed by silica gel column chromatography (toluene:
EtOAc, 40:1, v/v (twice), then hexane:EtOAc, 4:1, v/v)
to a€ord a light orange crystalline solid 19 (181 mg,
45% from 17): 1H NMR (CDCl3, 300MHz) (diastereomer
ratio 1:2.4) d 7.87±8.28 (4H, m), 7.62±7.70 (1H, broad),
7.46±7.59 (4H, m), 6.79±7.18 (4H, m), 6.05 (0.29H, d,
J=8.4 Hz) and 5.99 (0.71H, d, J=9.1 Hz), 5.33 (2H, s),
4.29±4.72 (2H, m), 2.80±3.00 (4H, m), 1.87±2.55 (5H,
m), 0.93±1.00 (6H, m); IR (Nujol) cmÀ1 3420, 3310,
2720, 2670, 1685, 1665, 1600; FAB±MS m/z 572
(M+H+), 441, 430, 300, 141.
Ethyl 5-isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-
thienyl)-1-indanacrylate (21). A mixture of the crude 18
(820 mg, 1.12 mmol) and (C6H5)3PˆCHCOOC2H5
(0.78 g, 2.24 mmol) in CHCl3 (10 mL) was stirred at
room temperature for 3 days. After removal of solvent,
the residue was puri®ed by silica gel column chromato-
graphy (toluene:EtOAc, 30:1, v/v) to a€ord a light
brown solid 21 (439 mg, 73%) as a mixture of Z- and E-
forms. A small portion of 21 was separated on pre-
parative TLC (EtOAc:hexane, 4:1, v/v, then toluene:
EtOAc, 2:1, v/v) to a€ord Z main-portion as a colorless
semi-solid and E main-portion as a colorless crystalline
1
powder. Z main-portion: H NMR (CDCl3, 200 MHz)
(diastereomer ratio, 1:2) d 6.8±8.3 (13H, m), 6.26
(0.33H, t, J=10.3 Hz) and 6.21 (0.67H, t, J=11.2 Hz),
5.96 (0.67H, dd, J=1.0, 10.3 Hz) and 5.90 (0.33H, dd,
J=1.0, 11.2 Hz), 5.50 (2H, s), 4.1±5.4 (4H, m), 1.85±
3.05 (3H, m), 1.2±1.4 (3H, m), 0.90±1.05 (6H, m); IR
(Nujol) cmÀ1 3300, 1720, 1660, 1610, 1600, 1525; EI±
MS m/z 539 (M+), 469, 398, 328, 141. E main-portion:
mp140.0±147.0 ꢀC; H NMR (CDCl3, 200 MHz) (dia-
1
Methyl 5-isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-
thienyl)-1-indanacetate (20). A mixture of 19 (189 mg,
0.331 mmol), HgCl2 (224 mg, 0.828 mmol), MeOH
(27 mL), H2O (3 mL), and THF (10 mL) was re¯uxed
for 3 h. After cooling, the resulting precipitate was ®l-
tered o€ and washed with EtOAc. The ®ltrate and the
washings were combined and concentrated in vacuo.
The residue was dissolved in EtOAc and washed with
H2O and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. The residue was puri®ed by silica
gel column chromatography (toluene:EtOAc, 50:1±30:1,
v/v) and recrystallized from toluene±hexane to a€ord
colorless needles 20 (117 mg, 69%): mp116.5±119.0 ꢀC;
1H NMR (CDCl3, 300 MHz) (cis:trans, 1:2.5) d 8.15
(cis) (0.29H, s) and 8.20 (trans) (0.71H, s), 8.01±8.08
(1H, m), 7.88±7.95 (2H, m), 7.62±7.68 (1H, broad),
7.45±7.58 (4H, m), 7.10±7.17 (1H, m), 7.00 (cis) (0.29H,
s) and 7.03 (trans) (0.71H, s), 6.83±6.96 (2H, m), 5.52
(2H, s), 4.57 (cis) (0.29H, t, J=8.5 Hz) and 4.69 (trans)
(0.71H, t, J=7.1 Hz), 3.71 (cis) (2.1H, s) and 3.70 (trans)
(0.86H, s), 3.50±3.85 (1H, m), 2.31±2.98 (4H, m), 2.09±
2.21 (1H, m), 0.94±1.01 (6H, m); IR (Nujol) cmÀ1 3300,
1735, 1660, 1610, 1600, 1525, 1495; EI±MS m/z 513
(M+), 443, 401, 372, 302, 228, 141.
stereomer ratio, 2:3) d 6.8±8.3 (14H, m), 6.06 (0.4H, d,
J=16.1 Hz) and 5.91 (0.6H, dd, J=1.0, 15.6 Hz), 5.52
(2H, s), 4.55±4.75 (1H, m), 3.85±4.30 (3H, m), 1.95±
3.00 (3H, m), 1.2±1.4 (3H, m), 0.90±1.05 (6H, m); IR
(Nujol) cmÀ1 3300, 1720, 1705, 1685, 1660, 1665,
1650, 1610, 1600; EI±MS m/z 539 (M+), 398, 328,
141.
Ethyl 5-isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-
thienyl)-1-indanpropionate (22). To a stirred mixture of
.
21 (501 mg, 0.928 mmol) and NiCl2 6H2O (44 mg,
0.186 mmol) in THF (15 mL)±EtOH (15 mL) was added
NaBH4 (229 mg, 6.03 mmol) portionwise at 0.5±1 h
intervals at 0 ꢀC. The whole was stirred at room tem-
perature for 14 h, diluted with H2O, and extracted with
EtOAc. The extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in
vacuo. The residue was dissolved in DMF (5 mL).
1-(Chloromethyl)naphthalene (66 mg, 0.371 mmol), NaI
(56 mg, 0.928 mmol), and K2CO3 (128 mg, 0.928 mmol)
were added to this solution, and the whole was stirred at
room temperature for 2.5 h, diluted with H2O, and
extracted with EtOAc. The extracts were washed with
H2O and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. The residue was puri®ed by silica
gel column chromatography (toluene:EtOAc, 30:1, v/v)
and recrystallized from EtOAc±hexane to a€ord light
Methyl 5-isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-
thienyl)-1-indanacetic acid (1l). 20 (113 mg, 0.220 mmol)
was treated in a similar manner described for the
preparation of 1b and recrystallized from EtOAc±
hexane to a€ord colorless needles 1l (104 mg, 95%):
mp177.0±180.0 ꢀC; 1H NMR (CDCl3, 300 MHz)
(cis:trans, 1:2.4) d 6.80±8.22 (12H, m), 7.63±7.68 (1H,
broad), 5.51 (2H, s), 4.55 (cis) (0.29H, t, J=8.6 Hz) and
4.68 (trans) (0.71H, t, J=7.1 Hz), 3.50±3.65 (cis) (0.29H,
m) and 3.72±3.84 (trans) (0.71H, m), 1.8±3.0 (5H, m),
ꢀ
brown needles 22 (230 mg, 46%): mp121.0±123.0 C; 1H
NMR (CDCl3, 200 MHz) (diastereomer ratio, 1:1.5) d
6.75±8.25 (13H, m), 5.54 (2H, s), 4.68 (0.6H, t,
J=6.8 Hz) and 4.55 (0.4H, dd, J=8.0, 11.0 Hz), 4.05±
4.35 (2H, m), 3.05±3.45 (1H, m), 1.3±2.9 (7H, m), 1.1±
1.4 (3H, m), 0.7±1.1 (6H, m); IR (Nujol) cmÀ1 3360,
1735, 1660, 1610, 1530; FAB±MS m/z 542 (M+H+),
400, 318, 141.

H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
267
5-Isobutyrylamino-6-(1-naphthylmethyloxy)-3-(2-thien-
yl)-1-indanpropionic acid (1m). 22 (214 mg, 0.395 mmol)
was treated in a similar manner described for the pre-
paration of 1b to a€ord 1m as colorless needles (191 mg,
6.78±8.21 (15H, m), 4.51±4.99 (1H, m), 3.97±4.27 (1H,
m), 3.52±3.83 (3H, m), 1.65±3.07 (3H, m), 0.75±1.28
(6H, m); IR (Nujol) cmÀ1 3290, 1735, 1665, 1570, 1510;
ꢀ
EI±MS m/z 495 (M+), 452, 424. 25: mp161.0±165.0 C;
94%): mp162.5±166.0 ꢀC; H NMR (CDCl3, 300 MHz)
1H NMR (CDCl3, 300 MHz) (cis:trans, 1:1.5) d 6.83±
8.08 (12H, m), 5.91 (1H, broad), 4.59 (cis) (0.4H, t,
J=8.8 Hz) and 4.87 (trans) (0.6H, t, J=7.6 Hz), 4.18
(trans) (0.6H, dd, J=4.4, 8.2 Hz) and 4.06 (cis) (0.4H, t,
J=8.7 Hz), 3.81 (cis) (1.2H, s) and 3.73 (trans) (1.8H, s),
3.25±3.54 (2H, m), 2.83±3.09 (3H, m), 2.34±2.57 (1H,
m), 1.5±1.7 (1H, m), 0.89 (cis) (2.4H, d, J=6.9 Hz) and
0.90 (trans) (3.6H, d, J=6.9 Hz); IR (Nujol) cmÀ1 3290,
1740, 1665, 1585, 1520; EI±MS m/z 495 (M+), 356.
1
(diastereomer ratio, 1:1) d 6.81±8.20 (12H, m), 7.64
(0.5H, broad) and 7.66 (0.5H, broad), 5.53 (2H, s), 4.68
(0.5H, t, J=7.0 Hz) and 4.54 (0.5H, t, J=8.7 Hz), 3.26±
3.42 (0.5H, m) and 3.11±3.25 (0.5H, m), 1.80±2.80 (7H,
m), 1.2±1.4 (3H, m), 0.93±0.99 (6H, m); IR (Nujol)
cmÀ1 3300, 2730, 2670, 1705, 1665, 1610, 1600, 1530,
1495; FAB±MS m/z 514 (M+H+), 372, 303, 290, 141.
Anal. calcd for C31H31NO4S (+0.1 H2O): C, 72.49
(72.23); H, 6.08 (6.10); N, 2.73 (2.66); S, 6.24 (6.03).
Found: C, 72.14; H, 6.09; N, 2.66; S, 6.03.
5-Isobutyrylamino-6-(1-naphthylethynyl)-3-(2-thienyl)-1-
indancarboxylic acid (1n). A solution of 23 (60 mg,
0.122 mmol) in THF (2 mL)±MeOH (2 mL) was treated
in a similar manner described for the preparation of 1b
to a€ord 1n as colorless needles (54 mg, 92%): mp
Methyl
5-isobutyrylamino-6-(1-naphthylethynyl)-3-(2-
thienyl)-1-indancarboxylate (23). To a stirred suspen-
sion of 10 (477 mg, 1.33 mmol) and triethylamine
(213 mL, 1.53 mmol) in dry CH2Cl2 (5 mL) was added
(CF3SO2)2O (246 mL, 1.46 mmol) at 0 ꢀC, and the mix-
ture was stirred at the same temperature for 30 min.
10% aq HCl was added to the reaction mixture and the
aqueous layer was extracted with CHCl3. The extracts
were washed with H2O and brine, dried over anhydrous
Na2SO4, and concentrated in vacuo. The residue was
puri®ed by silica gel column chromatography (hexane:
EtOAc, 4:1, v/v) to a€ord a light reddish caramel
(548 mg). A mixture of the obtained caramel (260 mg,
0.529 mmol) and LiCl (56 mg, 1.32 mmol) was chased
with toluene. A mixture of the caramel obtained, tribu-
tyl-1-naphthylethynyltin (350 mg, 0.794 mmol), and
PdCl2(PPh3)2 (19 mg, 0.0265 mmol) in dry dioxane
(10 mL) was re¯uxed under argon atmosphere for 4 h
and concentrated in vacuo. The residue was puri®ed by
silica gel column chromatography (toluene:EtOAc, 50:1,
v/v) and recrystallized from EtOAc±hexane to a€ord
faintly yellow needles 23 (200 mg, 77%): mp133.0±
201.5 ꢀC; H NMR (CDCl3, 300 MHz) (cis:trans, 1:1.7)
1
d 8.19±8.25 (1H, broad), 6.90±8.39 (12H, m), 4.68 (cis)
(0.37H, t, J=9.0 Hz) and 4.95 (trans) (0.63H, t,
J=7.5 Hz), 4.13 (cis) (0.37H, t, J=8.8 Hz) and 4.24
(trans) (0.63H, dd, J=4.4, 8.1 Hz), 2.43±2.64 (2H, m),
1.25 (6H, d, J=7.0 Hz); IR (Nujol) cmÀ1 3300, 3200±
2400, 1710, 1690, 1665, 1570, 1515; EI±MS m/z 479 (M+),
408, 364. Anal. calcd for C30H25NO3S: C, 75.13; H, 5.25;
N, 2.92; S, 6.69. Found: C, 74.87; H, 5.27; N, 2.73; S, 6.39.
5-Isobutyrylamino-6-(2-(1-( Z)-naphthyl)ethenyl)-3-(2-
thienyl)-1-indancarboxylic acid (1o). A solution of 24
(45 mg, 0.0908 mmol) in THF (2 mL)±MeOH (2 mL)
was treated in a similar manner described for the pre-
paration of 1b to a€ord 1o as faintly brown amorphous
powder (33 mg, 76%): 1H NMR (CDCl3, 300 MHz)
(diastereomer ratio was not determined) d 6.75±8.20
(15H, m), 4.53±5.02 (1H, m), 3.95±4.30 (1H, m), 2.8±3.6
(1H, m), 2.3±2.7 (1H, m), 1.55±1.78 (1H, m), 0.65±1.30
(6H, m); IR (Nujol) cmÀ1 3400, 3200±2400, 1710, 1695,
1660; EI±MS m/z 481 (M+), 410, 366, 326. Anal. calcd
for C30H27NO3S (+0.3 H2O): C, 74.82 (74.00); H, 5.65
(5.71); N, 2.91 (2.88); S, 6.66 (6.58). Found: C, 74.08; H,
5.72; N, 2.74; S, 6.51.
ꢀ
1
146.0 C; H NMR (CDCl3, 300 MHz) (cis:trans, 1:1.2)
d 8.15±8.25 (1H, broad), 6.90±8.40 (12H, m), 4.66 (cis)
(0.45H, dd, J=8.4, 9.4 Hz), and 4.94 (trans) (0.55H, t,
J=7.7 Hz), 4.08 (cis) (0.45H, t, J=8.8 Hz) and 4.21
(trans) (0.55H, dd, J=4.1, 8.0 Hz), 3.83 (cis) (1.4H, s)
and 3.76 (trans) (1.6H, s), 2.88±3.50 (1H, m), 2.41±2.63
(2H, m), 1.22±1.27 (6H, m); IR (Nujol) cmÀ1 3280,
3180, 2720, 2670, 1740, 1735, 1665, 1570, 1520, 1465;
EI±MS m/z 493 (M+), 422, 364.
5-Isobutyrylamino-6-(2-(1-naphthyl)ethyl)-3-(2-thienyl)-
1-indancarboxylic acid (1p). A solution of 25 (54 mg,
0.112 mmol) in THF (2 mL)±MeOH (2 mL) was treated
in a similar manner described for the preparation of 1b
to a€ord 1p as colorless needles (39 mg, 72%): mp
Methyl 5-isobutyrylamino-6-(2-(1-(Z)-naphthyl)ethenyl)-
3-(2-thienyl)-1-indancarboxylate (24) and methyl 5-iso-
butyrylamino-6-(2-(1-naphthyl)ethyl)-3-(2-thienyl)-1-in-
229.0±230.0 ꢀC; H NMR (CDCl3, 300 MHz) (cis:trans,
1
1:2) d 7.72±8.10 (3H, m), 7.46±7.56 (3H, m), 7.27±7.37
(2H, m), 7.09±7.22 (2H, m), 6.83±6.97 (2H, m), 6.14
(1H, broad), 4.55±4.64 (cis) (0.33H, m) and 4.88 (trans)
(0.67H, t, J=7.7 Hz), 4.05 (cis) (0.33H, t, J=9.1 Hz)
and 4.16 (trans) (0.67H, dd, J=4.2, 8.2 Hz), 3.25±3.51
(2H, m), 2.84±3.06 (3H, m), 2.33±2.60 (1H, m), 1.67
(1H, quintet, J=6.9 Hz), 0.90 (cis) (1H, d, J=6.8 Hz)
and 0.90 (trans) (2H, d, J=6.8 Hz); IR (Nujol) cmÀ1
3280, 3200±2500, 1720, 1690, 1655; EI±MS m/z 483
(M+), 440, 342, 272, 141. Anal. calcd for C30H29NO3S
(+0.3 H2O): C, 74.51 (73.95); H, 6.04 (6.08); N, 2.90
(2.87); S, 6.63 (6.58). Found: C, 73.91; H, 6.00; N, 2.74;
S, 6.60.
dancarboxylate (25).
A solution of 23 (102 mg,
0.207 mmol) in THF (10 mL)±MeOH (20 mL) was
hydrogenated over 10% Pd/C (water wet) (100 mg) at
3.5 atm for 34 h. The catalyst was ®ltered o€, and the
®ltrate was concentrated in vacuo. The residue was
puri®ed by silica gel column chromatography (toluene:
EtOAc, 20:1, v/v) to a€ord 24 (41 mg, 40%) as a light
yellow crystalline powder which was recrystallized from
ether±hexane and 25 (52 mg, 51%) as colorless needles
which was recrystallized from EtOAc±hexane, respec-
tively. 24: mp142.5±154.0 ꢀC; 1H NMR (CDCl3,
300 MHz) (diastereomer ratio was not determined) d

268
H. Morimoto et al. / Bioorg. Med. Chem. 9 (2001) 255±268
Receptor binding assay: porcine aortic membrane
Pelton, J. T.; Miller, R. C. Pharmacol. Ther. 1993, 59, 55. (c)
Gray, G. A.; Webb, D. J. Pharmacol. Ther. 1996, 72, 109.
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J. D. Current Pharmaceutical Design 1995, 1, 425. (c) Doherty,
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Porcine aorta (known to contain ETA receptors) from
which endothelium was removed was homogenized in
10 mM MOPS bu€er (pH 7.4) containing 20% sucrose.
The homogenate was centrifuged under cooling for
15 min at 1000Âg. The supernatant was centrifuged
under cooling for 45 min at 90,000Âg. The precipitate
was re-suspended in 5 mM HEPES±Tris bu€er to obtain
a membrane preparation. 50 mL of the diluted mem-
brane preparation (2 mg/mL), 50 mL of 125I-labeled
endothelin-1 (®nal concentration of 125I-labeled endo-
thelin-1: 20 pM, speci®c activity: 74 TBq/mmol, Amer-
sham Japan), and 50 mL of a test compound solution in
various concentrations were admixed. The mixture was
added to 150 mL of assay bu€er (50 mM Tris±HCl bu€er
(pH 7.4) containing 0.1% BSA, 0.1 mM phenylmethyl-
sulfonyl ¯uoride, 1 mM pepstatin A, 2 mM leupeptin,
1 mM 1,10-phenanethrorine and 1 mM EDTA), and
incubated for 2 h at 25 ꢀC. The incubation was terminated
by rapid ®ltration through Whatman GF/B glass ®ber
®lters. The ®lters were washed with ice-cooled 5 mM
HEPES±Tris bu€er (pH 7.4) containing 0.1% BSA and
the radioactivity was counted by a gamma counter
(ARC-360, Aloka Ltd). The antagonistic activity of the
test compound (inhibitory e€ect on 125I-labeled endo-
thelin-1 binding to porcine aortic membranes) was esti-
mated as IC50 which is the concentration (M) required
to inhibit the speci®c binding of 125I-labeled endothelin-1
by 50%. Meanwhile, the non-speci®c binding of endothelin
was estimated in the presence of 2Â10À7 M endothelin-1.
10. Reduction of the indene 4 under H2 atmosphere in the
presence of acetic acid with palladium catalysts such as palla-
dium on activated carbon or colloidal palladium resulted in
low yield of the indan derivatives 5 and 6.
11. The con®gurations of cis-trans isomer were assigned by
1
analysis of nuclear Overhauser e€ect (NOE) in H NMR. In
cis isomer, NOEs between one of the protons at 2-position and
both of the protons at 1- and 3-positions were observed, but
not in trans isomer.
12. 1-Methyl-3-hydroxymethylindole was synthesized by the
method of Mattocks, A. R. J. C. S. Perkin I 1978, 896. How-
ever, neither a chlorination nor a mesylation of the hydroxyl
groupwas not successful, probably due to instability of the
generated alkylating agents.
Acknowledgements
The authors are grateful to Dr. M. Ozeki for his
encouragement. Thanks are also due to the sta€ of the
analytical section of our research laboratory for spectral
measurements and elemental analyses.
13. Kruse, C. G.; Broekhof, N. L. J. M.; Wijsman, A.; van der
Gen, A. Tetrahedron Lett. 1977, 10, 885.
14. Chamberlin, A. R.; Nguyen, H. D.; Chung, J. Y. L. J.
Org. Chem. 1984, 49, 1682.
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led to tributyl-1-naphthylethynyltin by a reaction with n-BuLi
and n-Bu3SnCl.
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