Rational Design of an Indolebutanoic Acid Derivative as a Novel Aldose Reductase Inhibitor Based on Docking and 3D QSAR Studies of Phenethylamine Derivatives

Article abstract of DOI:10.1021/jm0205346

A series of 45 phenethylamine derivatives were synthesized and evaluated for their inhibitory activity against pig kidney aldose reductase (ALR2, EC 1.1.1.21). Their IC₅₀ values ranged from 400 μM to 24 μM. The binding modes of compounds at the active site of ALR2 were examined using flexible docking. The results indicated that phenethylamine derivatives nicely fit into the active pocket of ALR2 by forming various hydrogen bonding and hydrophobic interactions. 3D-QSAR analysis was also conducted using FlexX-docked alignment of the compounds. The best prediction was obtained by CoMSIA combined with hydrophobic and hydrogen bond donor/acceptor field (q ² = 0.557, r² = 0.934). A new derivative, 4-oxo-4-(4-hydroxyindole)butanoic acid, was designed, taking into account the CoMSIA field and the binding mode derived by FlexX docking. This rationally designed compound exhibits an ALR2 inhibition with an IC₅₀ value of 7.4 μM, which compares favorably to that of a well-known ALR2 inhibitor, tolrestat (IC₅₀ = 16 μM) and represents a potency approximately 240-fold higher than that of an original phenethylamine lead compound, YUA001.

Full text of DOI:10.1021/jm0205346

J . Med. Chem. 2003, 46, 5619-5627
5619
Ra tion a l Design of a n In d olebu ta n oic Acid Der iva tive a s a Novel Ald ose
Red u cta se In h ibitor Ba sed on Dock in g a n d 3D QSAR Stu d ies of
P h en eth yla m in e Der iva tives
†
†
‡
†
†
†
Won Suck Sun, Yoon Sun Park, J akyung Yoo, Ki Duk Park, Sung Han Kim, J ung-Han Kim, and
Hyun-J u Park*,‡
Department of Biotechnology, College of Engineering and Bioproducts Research Center, Yonsei University,
Seoul 120-749, Korea, and College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Korea
Received November 26, 2002
A series of 45 phenethylamine derivatives were synthesized and evaluated for their inhibitory
activity against pig kidney aldose reductase (ALR2, EC 1.1.1.21). Their IC50 values ranged
from 400 µM to 24 µM. The binding modes of compounds at the active site of ALR2 were
examined using flexible docking. The results indicated that phenethylamine derivatives nicely
fit into the active pocket of ALR2 by forming various hydrogen bonding and hydrophobic
interactions. 3D-QSAR analysis was also conducted using FlexX-docked alignment of the
compounds. The best prediction was obtained by CoMSIA combined with hydrophobic and
2
2
hydrogen bond donor/acceptor field (q ) 0.557, r ) 0.934). A new derivative, 4-oxo-4-(4-
hydroxyindole)butanoic acid, was designed, taking into account the CoMSIA field and the
binding mode derived by FlexX docking. This rationally designed compound exhibits an ALR2
inhibition with an IC50 value of 7.4 µM, which compares favorably to that of a well-known
ALR2 inhibitor, tolrestat (IC50 ) 16 µM) and represents a potency approximately 240-fold higher
than that of an original phenethylamine lead compound, YUA001.
In tr od u ction
Since the early 1980s, along with progress in com-
puter technology, a significant advance has been made
in the application of computer modeling to medicinal
Aldose reductase (ALR2, EC 1.1.1.21) is a NADPH-
specific aldehyde reductase that catalyzes the conver-
sion of glucose to sorbitol in the polyol pathway and is
known to be involved in the onset of long-term diabetic
1
7-19
chemistry.
Although the predictive power of mo-
lecular modeling remains controversial, this methodol-
ogy has proven useful in drug discovery and recently
provides an alternative, so-called virtual screening.
Virtual screening is a computing technology to analyze
large databases of chemicals in order to discover possible
drug candidates, and complement current advances in
high-throughput chemical synthesis and biological
complications such as cataract, neuropathy, retinopathy,
and nephropathy.1-3 To date, studies to develop aldose
reductase inhibitors (ARIs) to prevent those complica-
tions have yielded many structually diverse ARIs such
as tolrestat, sorbinil, zopolrestat, and others.4-9
ALR2 contains a (R/â)8 barrel motif with a large
hydrophobic pocket, approximately 4 × 15 Å wide and
2
0-24
assays.
Recently, Costantino et al. reported a series
of benzopyran-4-one derivatives as ARIs on the basis
of binding mode, and enhanced their activity through
1
5 Å deep, which favors aromatic and apolar substrates
over highly polar monosaccharides. The cofactor NAD-
PH is bound in an extended conformation across the
barrel with the nicotinamide ring centered at the bottom
of this cavity. Crystal structures of ALR2 complexed
with NADPH and diverse ARIs revealed that this pocket
is the only possible active site and is mainly composed
of two regions: an anion binding site of hydrophilic
residues (Tyr48, His110, Trp111, and the 4-pro-R
hydrogen of the nicotineamide ring of NADPH) and a
2
5,26
SAR study.
Rastelli et al. identified candidate ARIs
having novel pharmacophoric groups such as sulfonic
acids, nitro derivatives, sulfonamides, and carbonyl
derivatives by performing database search and dock-
2
7
ing. Iwata et al. also discovered a series of indole-3-
acetic acids analogues as ARIs by screening the 3D
2
8
chemical database (ACD3D).
In our previous study, derivatives (1-11 in Figure 1)
of YUA001 (N-2-methylbutanoyl tyramine from alkalo-
philic Corynebacterium sp. YUA25) were synthesized
and evaluated for their inhibitory activity against pig
kidney ALR2. Most of them showed more potent inhibi-
tory activity than that of YUA001; however, the need
for enhancing their activity and elucidating their inhibi-
wall of hydrophobic residues (Trp20, Trp79, Trp111,
Phe122, Leu300, etc.).1
0-13
Many studies have proposed
the requisite properties of ARIs: (1) an aromatic ring
system to form hydrophobic or π-π stacking interac-
tions with the hydrophobic amino acid residues in the
active site, and (2) ionizable groups such as carboxylic
acids and spirohydantoins which can anchor the anionic
2
9
tory mechanism remained.
1
4-16
binding site.
In this study, we synthesized 45 phenethylamine
derivatives and evaluated their inhibitory activity against
ALR2. Then, a structure-based drug design approach
*
Corresponding author. Tel.: 82-31-290-7719. Fax: 82-31-290-5403.
e-mail: hyunju@skku.ac.kr.
†
was taken to find new derivatives with improved
Yonsei University.
Sungkyunkwan University.
‡
30-33
activity.
Flexible docking and 3D-QSAR/CoMSIA
1
0.1021/jm0205346 CCC: $25.00 © 2003 American Chemical Society
Published on Web 11/20/2003

5
620 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 26
Sun et al.
F igu r e 1. Preparation of (A) phenethylamine derivatives, 1-31, (B) benzyl and phenylamine derivatives, 32-39, (C) indoline
and indole derivatives, 40-46.
analysis were used to explore structure-activity rela-
tionships of the compounds we identified, and guided
the design of the most potent derivative, 4-oxo-4-(4-
hydroxyindole)butanoic acid (46 in Figure 1). The
present study demonstrates a successful example of
rational drug design approaches: we used not only a
CoMSIA model to decide the substituent properties of
a new derivative, but also a binding conformation
obtained from flexible docking analysis to define posi-
tions to be substituted.
2-methylbutanamide (YUA001), isolated from alkalo-
2
9
philic Corynebacterium sp. YUA25, was chosen as a
lead, and various structural modifications were con-
ducted to find new synthetic derivatives with improved
activities. We modified it with an elongated aliphatic
chain (1-6) and the introduction of aromatic rings (7-
8) or terminal carboxyl acids (9-45), while maintaining
phenethylamine as a framework. The syntheses of
N-substituted tyramine derivatives 1-11 were reported
34,35
previously.
As outlined in Figure 1A and B, the para-
substituted tyramine derivatives 12-31 were prepared
by treating each anhydride with para-substituted amine
in acetonitrile (THF) at 40 °C. For benzyl and pheny-
lamine derivatives 32-39, cyclic anhydride was reacted
Resu lts
Syn th esis a n d Bioch em ica l Eva lu a tion . A novel
aldose reductase inhibitor, N-[2-(4-hydroxyphenyl)ethyl]-

Design of a Novel Aldose Reductase Inhibitor
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 26 5621
Ta ble 1. Inhibitory Activities against Pig Kidney Aldose
Reductase of Phenethylamine Derivatives 1-46
revealed that FlexX was successful in reproducing the
binding conformation of tolrestat.
compounds
IC50 value (M)a
compounds
IC50 value (M)a
To evaluate the relationship between relative ALR2
inhibitory activities and binding energy scores obtained
from FlexX docking, we have used consensus scoring
program, Cscore, that integrates multiple well-known
scoring functions: a GOLD-like function, a DOCK-like
-
-
-
-
-
-
-
-
-
-
-
-
3
-4
YUA001
1.8 × 10
1.6 × 10
1.3 × 10
1.2 × 10
1.1 × 10
1.1 × 10
1.5 × 10
1.6 × 10
1.0 × 10
3.9 × 10
0.8 × 10
3.4 × 10
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
0.99 × 10
4
-4
1
2
3
4
5
6
7
8
9
1.12 × 10
4
-4
2.03 × 10
4
-4
1.54 × 10
4
-4
0.94 × 10
4
-4
39-42
0.99 × 10
function, ChemScore, a PMF function, and FlexX.
4
-4
0.81 × 10
The FlexX scoring function performs best, and the
resulting ranking showed good agreement with the
ALR2 inhibitory activities of the compounds. Therefore,
we selected the top-scoring conformer of each ligand
based on the FlexX scores calculated from FlexX, and
positioned it onto the active site of ALR2. They fit well
into the active site pocket of ALR2 occupied by tolrestat
in the X-ray crystal structure. All the compounds
primarily contain either a phenolic hydroxyl (YUA001
and 1-8) or carboxylate (9-45) group. Those groups
anchor into the anionic binding site by forming numer-
4
-4
1.1× 10
4
-4
1.92 × 10
4
-4
1.82 × 10
4
-4
1
1
1
1
1
1
1
1
1
1
2
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
2.27 × 10
4
-4
4.4 × 10
-
-
-
-
4
4
4
4
4
-4
0.78 × 10
0.73 × 10
0.88 × 10
1.04 × 10
1.41 × 10
-4
1.5 × 10
-4
1.8 × 10
-4
1.33 × 10
-
-4
1.7 × 10
1.02 × 10
-
-
-
-
-
-
-
4
4
4
4
4
4
4
-4
1.55 × 10
1.77 × 10
1.85 × 10
0.94 × 10
0.75 × 10
0.88 × 10
0.76 × 10
0.4 × 10
-4
0.95 × 10
-4
0.24 × 10
+
-4
ous hydrogen bonds with NADP or the side chain of
0.37 × 10
-4
0.3 × 10
Trp111, His110, and Tyr48. The interaction between the
ligand and amino acid residues of the active site were
determined and are illustrated in Figure 2 for the three
representative compounds, YUA001, 10, and 43, in
-5
0.74 × 10
b
-4
Tolrestat
0.16 × 10
a
b
Evaluted in vitro against pig kidney aldose reductase. N-
[[6-Methoxy-5-(trifluoromethyl)-1-naphthalenyl]thioxomethyl]-N-
38
comparison with the X-ray structure of tolrestat. An
methylglycine.
aliphatic chain of the acyl moiety of YUA001 is posi-
tioned close to Phe122 and Leu300, possibly forming a
hydrophobic interaction. For compound 10, the phenolic
hydroxyl group forms additional hydrogen bonding with
the Ser302 residue. The indole moiety of compound 43
intercalates between Phe122 and Leu300 and is likely
to play an important role in enhancing the affinity in
the active site through the π-π interaction.
with benzyl or phenylamine for 10 h at 40 °C. The
indoline and indole derivatives 40-46 were synthesized
following the synthetic method shown in Figure 1C. The
anhydrides were treated with indoline and indole in the
presence of a large excess of triethylamine and vigor-
ously stirred for 24 h at 80 °C.
The inhibitory activities of the compounds (1-45)
against ALR2 are evaluated and expressed as IC50
values in Table 1. Various modifications of phenethyl,
phenyl, and benzylamine (1-39) did not improve the
inhibitory activity significantly, exhibiting IC50 values
in the low millimolar to micromolar range. However,
replacement of the phenethylamine unit with indole or
indoline ring (40-45) increased the activity signifi-
cantly. Notably, 4-oxo-4-indolebutanoic acid (43) exhib-
ited the strongest ALR2 inhibitory activity with an IC50
value of 24 µM, which is comparable to the activity of
tolrestat (IC50 ) 16 µM).
3
D-QSAR/CoMSIA Mod elin g. 3D-QSAR methods,
especially CoMFA(Comparative Molecular Field Analy-
43
sis), are used widely in drug design, because they allow
rapid generation of QSARs from which biological activ-
ity of newly designed molecules can be predicted. The
basic assumption in CoMFA is that an appropriate
sampling of the steric and electrostatic fields around a
set of aligned molecules might provide all the informa-
tion necessary for understanding their biological activi-
ties. A main difficulty in the application of 3D-QSAR
methods such as CoMFA is that a spatial orientation
of the ligands toward one another has to be found to
yield a correct model. Therefore, the success of molecular
field analysis largely determined by the quality of
alignment of studied molecules. Another 3D-QSAR
method, the CoMSIA (Comparative Molecular Similar-
Dock in g Stu d y. We conducted docking analysis
using the FlexX algorithm3
6,37
not only to examine the
binding mode of the compounds at the active site of
aldose reductase (AR), but also to obtain a basis for
further synthetic derivatization. The crystal structure
of the ternary complex which includes cofactor NADPH
and tolrestat was used in this study (pdb entry )
4
4,45
ity Indices Analysis)
technique, is recently of par-
ticular interest since it is less alignment-sensitive than
CoMFA and includes a hydrophobic field and two
hydrogen bond fields. In this study, we performed 3D-
QSAR by CoMSIA on a select 42 compounds (except
compound 46 in Table 2), by using hydrophobicity and
hydrogen bond donor and acceptor as descriptors and
attempted to obtain a reliable CoMSIA model to guide
to the design of analogous AR inhibitors. For alignment
of the ligands, we used a superimposition of the top-
scoring conformations derived from FlexX docking.46 As
listed in Table 2, the biological activities of 42 ligands
used for the 3D-QSAR study were expressed as pIC50
values. To derive a predictive relationship model, the
partial least squares (PLS) method was used, and the
3
8
1
AH3). A COOH hydrophilic head of tolrestat and the
compounds 9-45 (pKa between 3.5 and 5.0) is probably
bound by AR in the form of carboxylate anion; the
COOH group of those molecules was calculated in the
anionic form which shares a negative charge between
two oxygen atoms. The energy-minimized structure of
tolrestat was preliminarily docked into ALR2 to exam-
ine how closely the FlexX algorithm can reproduce the
experimentally determined binding conformation of
tolrestat at the active site of AR. A superposition of
docked tolrestat onto the crystallographic geometry
yielded a root-mean-square (rms) deviation of 0.74 Å and

5
622 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 26
Sun et al.
F igu r e 2. Binding modes of phenethylamine derivatives obtained from the FlexX docking. Dotted lines indicate hydrogen bonding
interactions (<2.0 Å).
analysis was conducted by correlating variations in the
ligands’ biological activities with variations in their
into account the CoMSIA field and the binding mode
derived by FlexX docking, is a 243-fold more potent
inhibitor than YUA001, a mother compound of this
study.
2
CoMSIA fields. A correlation coefficient of r ) 0.934
and a cross-validated coefficient of q2 ) 0.557 were
obtained (Table 3). These results indicate a good predic-
tive ability of the model. This is also reflected by the
small deviation of the calculated from the experimental
values of IC50 (Table 2).
Con clu sion s
In this study, our laborious synthetic efforts (up to
compound 45 starting from phenylethylamine derivative
YUA001) yield AR inhibitors with IC50 values in the
range of 1.8 mM to 24 µM, and also indicated that indole
butanoic acid (compound 43) as a scaffold would have
the most potent activity. Therefore, we rationally de-
signed compound 46, a simple synthetic analogue of lead
compound 43, based upon the results obtained from
FlexX docking and 3D-QSAR/CoMSIA analysis. Com-
pound 46 exhibited improved activity in comparison
with compound 43, and 243-fold higher inhibitory
activity than YUA001. Further improvement of potency
would be achieved in future investigation using com-
pound 46 as a new lead. Our study demonstrates the
efficiency of computer-based drug design tools not only
for understanding the molecular basis of drug-receptor
interaction, but also for the discovery and further
optimization of new leads.
Design Ba sed on 3D-QSAR a n d Dock in g. Analysis
of CoMSIA contour maps (Figure 3) revealed that
hydrogen bond donor-favored region exists around 4-
position, and hydrophobicity-disfavored region around
the 5- and 6- of indole moiety of the most potent
compound, 43. On the basis of this observation, we built
three modified structures containing a hydroxyl group
at 4-, 5-, or 6-position of the indole ring, respectively.
Then, FlexX docking was conducted for the modified
structures, and resulting docked conformations were
examined to identify favorable interactions with ALR2.
As demonstrated in Figure 4, the analogue with a
hydroxyl group at the 4-position of the indole ring
(
compound 46) yielded the best agreement with the
ALR2-bound conformation of tolrestat. In particular,
-OH of 46 is superimposed onto the trifluoro group of
4
tolrestat, which forms a hydrogen bond with the OH
group of Ser 302 in the X-ray structure. In the docked
structure of 46:ALR2 complex, the distance between two
oxygen atoms in 4-OH of 46 and the OH of Ser 302 is
Exp er im en ta l Section
Ap p a r a tu s a n d Rea gen ts. Spectra of 1H NMR were
recorded on Varian UNITY 300 (Palo Alto, CA). The ESI mass
spectra were recorded with a Fison-VG platform (Beverly, MA).
UV spectrophotometer (Shimadzu, UV120) was used for aldose
reductase inhibitory activity assay at 340 nm. Computer
modeling was performed with Tripos Sybyl 6.847 in SGI Octane
II. Reagents and solvents for the synthesis of phenetylamine
derivatives (indole, indoline, etc.) were purchased from Sigma-
Aldrich Chemical Co. (St. Louis, MO). TLC was performed on
Merck Kiesel 60 F254 plates (Darmstadt, Germany). Merck
Kiesel 60 (Darmstadt, Germany) was used for column chro-
matography.
1
.4 Å, which is reasonable for the formation of a strong
hydrogen bond. In addition, the pIC50 value of 46
predicted by the CoMSIA model is 5.036 (Table 2), which
is higher than the activity of tolrestat (pIC50 ) 4.796).
Compound 46 was synthesized and tested for ALR2
inhibitory activity in comparison with tolrestat. The IC50
value of 46 was 7.4 µM, which is superior to that of both
tolrestat (IC50 ) 16 µM) and the lead compound, 43 (IC50
)
24 µM). Thus, compound 46, which was built taking

Design of a Novel Aldose Reductase Inhibitor
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 26 5623
Ta ble 2. Residuals of the Calculated Activities Derived from the CoMSIA Model
compounds
pIC50* a
hydrophobicb
donorc
acceptord
Pre-pIC50e
residualf
YUA001
2.745
3.959
3.886
3.921
3.796
4.000
4.108
4.097
3.469
4.108
4.137
4.056
3.983
3.770
3.807
3.752
3.733
4.027
4.125
4.056
4.119
4.004
3.951
3.693
3.813
4.027
4.004
4.092
3.959
3.717
3.740
3.644
3.357
3.851
3.824
3.876
3.991
4.398
4.022
4.620
4.523
4.796
5.131
4.65
3.59
4.7
1.97
1.98
1.13
1.15
2
2.28
2.64
2.64
2.65
2.65
2.32
4.97
4.93
4.91
4.85
5.03
4.94
4.11
5.12
5.03
5.19
4.47
4.85
5.03
4.62
4.36
4.85
5.03
4.63
4.36
4.85
4.45
4.63
4.84
4.79
4.52
4.2
2.813
3.839
3.938
3.845
3.765
4.044
4.154
4.118
3.326
3.999
4.059
3.998
3.933
3.88
3.952
3.833
3.673
4.008
3.974
4.103
3.959
4.018
3.988
3.891
3.945
4.026
4.087
3.939
4.048
3.633
3.7
-0.0683
0.1196
-0.0519
0.0758
1
2
3
7
8
9
5.55
4.66
3.74
4.04
3.91
4.97
4.37
4.25
4.98
4.61
3.92
3.83
4.66
4.15
4.54
4.46
5.07
4.78
5.19
5.15
5.76
5.46
5.78
5.65
6.34
5.91
3.47
3.32
4.3
0.0309
1.96
1.96
1.96
1.97
1.59
1.59
1.59
1.61
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.61
1.59
1.59
1.59
1.59
1.6
-0.044
-0.0461
-0.0211
0.1425
0.1089
0.0777
0.0575
0.05
-0.1104
-0.1453
-0.081
0.0598
0.0189
0.1509
-0.0475
0.1602
-0.0136
-0.0372
-0.1985
-0.1325
0.0009
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
4
4
4
4
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
9
0
1
2
3
5
-0.0826
0.1525
-0.0894
0.0837
0.0399
1.6
1.6
3.575
3.479
3.907
3.805
3.936
4.189
4.236
4.043
4.629
4.504
4.851
5.036
0.069
3.74
4.02
3.87
4.23
3.74
3.6
3.95
3.6
3.81
6.08
3.37
1.59
1.59
1.59
1.61
0
0
0
0
0
4.4
-0.1225
-0.0562
0.0189
-0.0599
-0.1976
0.1619
-0.0207
-0.0092
0.0189
4.21
4.06
4.18
4.87
4.65
4.46
4.85
4.47
3.62
4.98
tolr esta t
0
1.17
-0.0551
0.0947
4
6
a
pIC50* ) -log IC50. b Hydrophobicity. c Hydrogen bond donor. d Hydrogen bond acceptor fields. e Predicted pIC50. f pIC50 - Predicted
pIC50.
Ta ble 3. Summary of CoMSIA Results
nylamine was reacted with cyclic anhydrides, such as succinic,
maleic, phthalic, and glutaric anhydride (1.5 equiv) in aceto-
nitrile at room temperature, followed by stirring for 10 h in
CoMSIA
optimum number of components
probe atom
5
4
0 °C. The concentrated residual was further purified with
silica gel column chromatography (CHCl :MeOH ) 9:1) to give
2-39.
Gen er a l P r oced u r e for th e Syn th esis of In d olin e a n d
C sp3
0.557
0.102
0.934
105.508
3
2
2
cross-validated r (q )
3
standard error of estimate (S)
2
conventional r
In d ole Der iva tives (40-46). The reaction mixture of the
required indole or indoline, appropriate anhydrides (1.5 equiv)
and TEA (10 equiv) in acetonitrile was refluxed overnight.
After evaporation of solvent, residue was purified by silica gel
F-value
relative contributions
hydrophobicity
hydrogen donor
hydrogen acceptor
43.0%
22.1%
34.9%
chromatography (CHCl :MeOH ) 20:1) and washed with
3
hexane to give 40-46.
N-2-P h en yleth ylsu ccin a m ic Acid (12). The mixture of
succinic anhydride (262 mg, 2.62 mmol) and phenethylamine
(265 mg, 2.19 mmol) in acetonitrile (30 mL) gave 12 (513 mg,
Ald ose Red u cta se In h ibitor y Activity. The preparation
of AR and In vitro AR inhibition assays were conducted
3
4
according to the method in a previous publication. Tolrestat
was used as positive control.
6
4%): 1H NMR (DMSO-d
CH
6
, 300 MHz) δ 7.92 (1H, t, NHCH
2
-
2
Ar), δ 7.32 (1H, m, Ar-H), δ 7.15 (4H, m, Ar-H), δ 3.22
Gen er a l P r oced u r e for th e Syn th esis of P a r a -Su bsti-
tu ted P en eth yla m in e Der iva tives (12-31). Appropriate
anhydride (succinic, maleic, phthalic, and glutaric anhydride;
.5 equiv) was added to para-substituted amine relatively in
acetonitrile at room temperature. The mixture was stirred for
0 h at 40 °C and concentrated. The residual oil was chro-
(2H, m, NHCH
2
CH
2
2
Ar), δ 2.7 (2H, t, NHCH
2
CH
2
Ar), δ 2.41
(2H, t, COCH CH
2
COOH), δ 2.32 (2H, t, COCH
2
2
CH COOH);
+
3
ESI-MS m/z 221 (M ). Anal. (C12H15NO ) C, H, N.
1
N-2-P h en yleth ylm a lea m ic Acid (13). The mixture of
maleic anhydride (256 mg, 2.62 mmol) and phenethylamine
(265 mg, 2.19 mmol) in acetonitrile (30 mL) gave 13 (478 mg,
1
matographed on silica gel (CHCl :MeOH ) 9:1) and washed
3
with ether to give 12-31.
60%): 1H NMR (DMSO-d
6
, 300 MHz), δ 6.49 (3H, d, Ar-H), δ
6.48 (2H, d, Ar-H), δ 6.39 (1H, t, COCH ) CHCOOH), δ 6.29
(1H, t, COCHdCHCOOH), δ 3.41 (2H, m, NHCH CH Ar), δ
Gen er a l P r oced u r e for th e Syn th esis of Ben zyl a n d
P h en yla m in e Der iva tives (32-39). Each benzyl and phe-
2
2

5
624 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 26
Sun et al.
NHCH
(
2
CH
M ). Anal. (C13
calcd, 5.62; found, 5.71.
2
Ar), δ 2.72 (2H, t, NHCH
2
CH
2
Ar); ESI-MS m/z 249
+
4
H15NO ) C; H: calcd, 6.07; found, 6.19, N:
N-2-(p-Meth oxyp h en yl)eth ylp h th a la m ic Acid (18). The
mixture of phthalic anhydride (390 mg, 2.62 mmol) and (p-
methoxyphenyl)ethylamine (330 mg, 2.19 mmol) in acetonitrile
(
30 mL) gave 18 (276 mg, 25%): 1H NMR (DMSO-d
6
, 300 MHz)
Ar), δ 7.75 (1H, d, COPhCOOH), δ
.65 (2H, m, COPhCOOH), δ 7.18 (1H, m, COPhCOOH), δ 7.16
2H, d, Ar-H), δ 6.86 (2H, d, Ar-H), δ 3.72 (3H, s, OCH3), δ
.73 (2H, m, NHCH2CH2Ar), δ 2.49 (2H, t, NHCH2CH2Ar);
2 2
δ 8.37 (1H, t, NHCH CH
7
(
2
+
ESI-MS m/z 299 (M ). Anal. (C17
4
H17NO ) C; H: calcd, 5.72;
found, 5.68, N: calcd, 4.68; found, 4.63.
N-2-(p-Meth oxyp h en yl)eth ylglu ta r a m ic Acid (19). The
mixture of glutaric anhydride (299 mg, 2.62 mmol) and (p-
methoxyphenyl)ethylamine (330 mg, 2.19 mmol) in acetonitrile
(
30 mL) gave 19 (316 mg, 33%): 1H NMR (DMSO-d
6
, 300 MHz)
2 2
CH Ar), δ 7.1 (2H, d, Ar-H), δ 6.83 (2H,
δ 7.84 (1H, t, NHCH
dd, Ar-H), δ 3.71 (3H, s, OCH
Ar), δ 2.61 (2H, t, NHCH CH Ar), δ 2.17 (2H, m, COCH
CH COOH), δ 2.07 (2H, m, COCH CH CH
m, COCH CH CH COOH); ESI-MS m/z 265 (M ). Anal. (C14
NO ) C; H: calcd, 7.22; found, 7.28, N: calcd, 5.28; found, 5.21.
3
), δ 3.18 (2H, m, NHCH
2
CH
CH
2
-
-
2
2
2
2
2
2
2
2
COOH), δ 1.69 (2H,
+
2
2
2
19
H -
4
N-2-(p -F lu or op h en yl)et h ylsu ccin a m ic Acid (20). The
mixture of succinic anhydride (262 mg, 2.62 mmol) and (p-
fluorophenyl)ethylamine (304 mg, 2.19 mmol) in acetonitrile
(
30 mL) gave 20 (429 mg, 49%): 1H NMR (DMSO-d
6
, 300 MHz)
Ar), δ 7.22 (2H, d, Ar-H), δ 7.08 (2H,
d, Ar-H), δ 3.21 (2H, m, NHCH CH Ar), δ 2.66 (2H, t,
CH COOH), δ 2.26 (2H,
COOH); ESI-MS m/z 239 (M ). Anal. (C12
2 2
δ 7.92 (1H, t, NHCH CH
2
2
F igu r e 3. CoMSIA hydrogen bonding donor/acceptor and
hydrophobic contour plots of 4-oxo-4-indolebutanoic acid (43).
Cyan polyhedra indicate regions where hydrogen bonding
donor groups will enhance the binding. Magenta polyhedra
indicate regions where hydrogen bonding acceptor will enhance
the affinity. Red polyhedra indicate where hydrophilic groups
increase the binding.
NHCH
t, COCH
FNO
.91.
N-2-(p-Flu or oph en yl)eth ylm aleam ic Acid (21). The mix-
2
CH
2
Ar), δ 2.38 (2H, t, COCH
2
2
2
+
2
CH
14
H -
3
) C; H: calcd, 5.90; found, 5.98, N: calcd, 5.85; found,
5
ture of maleic anhydride (256 mg, 2.62 mmol) and (p-fluo-
rophenyl)ethylamine (304 mg, 2.19 mmol) in acetonitrile (30
mL) gave 21 (650 mg, 75%): 1H NMR (DMSO-d
δ 9.12 (1H, t, NHCH CH
2 2
, 300 MHz),
Ar), δ 7.25 (2H, d, Ar-H), δ 7.10 (2H,
d, Ar-H), δ 6.36 (1H, t, COCH ) CHCOOH), δ 6.23 (1H, t,
COCHdCHCOOH), δ 3.37 (2H, m, NHCH CH Ar), δ 2.76 (2H,
Ar); ESI-MS m/z 237 (M ). Anal. (C12
C, H; N: calcd, 6.33; found, 6.43.
6
+
2
.46 (2H, t, NHCH
) C, H; N: calcd, 6.33; found, 6.43.
N-2-P h en yleth ylp h th a la m ic Acid (14). The mixture of
phthalic anhydride (390 mg, 2.62 mmol) and phenethylamine
265 mg, 2.19 mmol) in acetonitrile (30 mL) gave 14 (345 mg,
2
CH
2
Ar); ESI-MS m/z 219 (M ). Anal.
12 3
(C H13NO
2
2
+
t, NHCH
2
CH
2
3
H12FNO )
(
3
1
5%): H NMR (DMSO-d
CH Ar), δ 7.75 (2H, m, COPhCOOH), δ 7.4 (1H, d, COPh-
COOH), δ 7.3 (5H, m, Ar-H), δ 3.54 (2H, m, NHCH CH Ar), δ
.71 (2H, t, NHCH CH Ar); ESI-MS m/z 269 (M ). Anal.
) C, H; N: calcd, 5.20; found, 5.15.
N-2-P h en yleth ylglu ta r a m ic Acid (15). The mixture of
glutaric anhydride (299 mg, 2.62 mmol) and phenethylamine
265 mg, 2.19 mmol) in acetonitrile (30 mL) gave 15 (304 mg,
6
, 300 MHz) δ 8.4 (1H, d, NHCH
2
-
N-2-(p-F lu or op h en yl)eth ylp h th a la m ic Acid (22). The
mixture of phthalic anhydride (390 mg, 2.62 mmol) and (p-
fluorophenyl)ethylamine (304 mg, 2.19 mmol) in acetonitrile
2
2
2
+
(30 mL) gave 22 (746 mg, 71%): 1H NMR (DMSO-d
δ 8.38 (1H, t, NHCH CH
2 2
2
2
2
6
, 300 MHz)
Ar), δ 7.73 (1H, s, COPhCOOH), δ
7.54 (2H, d, Ar-H), δ 7.29 (3H, s, COPhCOOH), δ 7.11 (2H, d,
Ar-H), δ 3.15 (2H, m, NHCH CH Ar), δ 2.80 (2H, t, NHCH CH
Ar); ESI-MS m/z 287 (M ). Anal. (C16 ) C; H: calcd,
4.91; found, 4.87, N: calcd, 5.95; found, 5.90.
(C
16
H
15NO
3
2
2
2
2
-
+
(
3
H14FNO
3
1
6%): H NMR (DMSO-d
CH CH Ar), δ 6.89 (3H, m, Ar-H), δ 6.73 (2H, dd, Ar-H), δ 3.16
2H, m, NHCH CH Ar), δ 2.65 (2H, t, NHCH CH Ar), δ 2.16
2H, m, COCH CH CH COOH), δ 2.01 (1H, m, COCH CH CH
COOH), δ 1.52 (1H, m, COCH CH CH COOH); ESI-MS m/z
) C; H: calcd, 7.28; found, 7.32, N:
6
, 300 MHz) δ 7.87 (1H, t, NHCH
2
-
2
2
N-2-(p-F lu or op h en yl)eth ylglu ta r a m ic Acid (23). The
mixture of glutaric anhydride (299 mg, 2.62 mmol) and (p-
fluorophenyl)ethylamine (304 mg, 2.19 mmol) in acetonitrile
(
(
2
2
2
2
2
2
2
2
2
2
-
(30 mL) gave 23 (438 mg, 47%): 1H NMR (DMSO-d
δ 7.86 (1H, t, NHCH CH
2 2
, 300 MHz)
Ar), δ 7.21 (2H, d, Ar-H), δ 7.08 (2H,
dd, Ar-H), δ 3.23 (2H, m, NHCH CH Ar), δ 2.66 (2H, t,
NHCH CH Ar), δ 2.14 (2H, m, COCH CH CH COOH), δ 2.04
(2H, m, COCH CH CH COOH), δ 1.65 (2H, m, COCH CH
CH COOH); ESI-MS m/z 253 (M ). Anal. (C13 ) C, H;
N: calcd, 5.53; found, 5.41.
2
2
2
6
+
2
35 (M ). Anal. (C13
H
17NO
3
calcd, 5.95; found, 5.90.
N-2-(p-Meth oxyp h en yl)eth ylsu ccin a m ic Acid (16). The
mixture of succinic anhydride (262 mg, 2.62 mmol) and (p-
2
2
2
2
2
2
2
2
2
2
2
2
-
+
methoxyphenyl)ethylamine (330 mg, 2.19 mmol) in acetonitrile
2
H16FNO
3
1
(
30 mL) gave 16 (377 mg, 41%): H NMR (DMSO-d
6
, 300 MHz)
δ 7.89 (1H, t, NHCH
2
CH
2
Ar), δ 7.11 (2H, d, Ar-H), δ 6.83 (2H,
N-2-(p-Ch lor op h en yl)eth ylsu ccin a m ic Acid (24). The
mixture of succinic anhydride (262 mg, 2.62 mmol) and (p-
chlorophenyl)ethylamine (340 mg, 2.19 mmol) in acetonitrile
d, Ar-H), δ 3.70 (3H, s, OCH
3
), δ 3.20 (2H, m, NHCH
2
CH
2
Ar),
δ 2.59 (2H, t, NHCH
δ 2.27 (2H, t, COCH
2
CH
CH
2
Ar), δ 2.40 (2H, t, COCH
2
CH
2
+
COOH),
COOH); ESI-MS m/z 251 (M ). Anal.
(30 mL) gave 24 (213 mg, 23%): 1H NMR (DMSO-d
6
, 300 MHz)
δ 7.31 (2H, d, Ar-H), δ 7.20 (2H, d, Ar-H), δ 3.21 (2H, m,
NHCH CH Ar), δ 2.66 (2H, t, NHCH CH Ar), δ 2.40 (2H, t,
COCH CH COOH), δ 2.25 (2H, t, COCH CH COOH); ESI-MS
m/z 255 (M ). Anal. (C12 ) C; H: calcd, 5.52; found,
5.47, N: calcd, 5.48; found, 5.50.
2
2
(C
13
H
17NO
4
) C; H: calcd, 6.82; found, 6.95, N: calcd, 5.57;
found, 5.54.
2
2
2
2
N-2-(p-Meth oxyp h en yl)eth ylm a lea m ic Acid (17). The
mixture of maleic anhydride (256 mg, 2.62 mmol) and (p-
methoxyphenyl)ethylamine (330 mg, 2.19 mmol) in acetonitrile
2
2
2
2
+
H
14ClNO
3
1
(30 mL) gave 17 (176 mg, 19%): H NMR (DMSO-d
6
, 300 MHz)
N-2-(p-Ch lor oph en yl)eth ylm aleam ic Acid (25). The mix-
ture of maleic anhydride (256 mg, 2.62 mmol) and (p-chlo-
rophenyl)ethylamine (340 mg, 2.19 mmol) in acetonitrile (30
δ 9.13 (1H, t, NHCH
d, Ar-H), δ 6.38 (1H, d, COCH ) CHCOOH), δ 6.23 (1H, d,
COCHdCHCOOH), δ 3.72 (3H, s, OCH ), δ 3.4 (2H, m,
2 2
CH Ar), δ 7.14 (2H, d, Ar-H), δ 6.86 (2H,
mL) gave 25 (637 mg, 69%): 1H NMR (DMSO-d
, 300 MHz),
6
3

Design of a Novel Aldose Reductase Inhibitor
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 26 5625
F igu r e 4. Superposition of the docked conformation of compound 46, 4-oxo-4-(4-hydroxyindole)butanoic acid (magenta) with the
experimentally obtained ALR2-bound conformation of tolrestat (orange). The connolly surface of the active site is shown in green,
and the select residues which form hydrogen bonds with compound 46 or tolrestat are represented in line form. Hydrogen bonding
interactions are shown in yellow dotted lines (<2.0 Å).
δ 7.33 (2H, d, Ar-H), δ 7.24 (2H, d, Ar-H), δ 6.34 (1H, t, COCH
CHCOOH), δ 6.20 (1H, t, COCHdCHCOOH), δ 3.37 (2H,
m, NHCH CH Ar), δ 2.75 (2H, t, NHCH CH Ar); ESI-MS m/z
53 (M ). Anal. (C12 12ClNO ) C; H: calcd, 4.77; found, 4.68,
N: calcd, 5.52; found, 5.62.
N-2-(p-Br om op h en yl)eth ylp h th a la m ic Acid (30). The
mixture of phthalic anhydride (390 mg, 2.62 mmol) and (p-
bromophenyl)ethylamine (437 mg, 2.19 mmol) in acetonitrile
)
2
2
2
2
+
(30 mL) gave 30 (686 mg, 54%): 1H NMR (DMSO-d
2
H
3
6
, 300 MHz)
δ 7.73 (1H, d, Ar-H), δ 7.54 (4H, s, COPhCOOH), δ 7.30 (1H,
d, Ar-H), δ 7.22 (2H, d, Ar-H), δ 3.14 (2H, m, NHCH CH Ar),
Ar); ESI-MS m/z 348 (M ). Anal.
) C; H: calcd, 4.05; found, 3.97, N: calcd, 4.02;
N-2-(p-Ch lor op h en yl)eth ylp h th a la m ic Acid (26). The
mixture of phthalic anhydride (390 mg, 2.62 mmol) and (p-
2
2
+
δ 2.77 (2H, t, NHCH
14BrNO
found, 3.98.
2 2
CH
chlorophenyl)ethylamine (340 mg, 2.19 mmol) in acetonitrile
(C16
H
3
1
(
30 mL) gave 26 (607 mg, 55%): H NMR (DMSO-d
6
, 300 MHz)
δ 8.38 (1H, t, NHCH
2
CH
2
Ar), δ 7.74 (2H, d, Ar-H), δ 7.56 (4H,
N-2-(p-Br om op h en yl)eth ylglu ta r a m ic Acid (31). The
mixture of glutaric anhydride (299 mg, 2.62 mmol) and (p-
bromophenyl)ethylamine (437 mg, 2.19 mmol) in acetonitrile
m, COPhCOOH), δ 7.35 (2H, m, Ar-H), δ 3.15 (2H, m, NHCH
2
+
-
CH
Anal. (C16
.61; found, 4.58.
N-2-(p-Ch lor op h en yl)eth ylglu ta r a m ic Acid (27). The
2
Ar), δ 2.49 (2H, t, NHCH
2 2
CH Ar); ESI-MS m/z 303 (M ).
H
14ClNO ) C; H: calcd, 4.65; found, 4.56, N: calcd,
3
(30 mL) gave 31 (920 mg, 80%): 1H NMR (DMSO-d
6
, 300 MHz)
δ 7.44 (2H, d, Ar-H), δ 7.14 (2H, m, Ar-H), δ 3.20 (2H, m,
NHCH CH Ar), δ 2.62 (2H, t, NHCH CH Ar), δ 2.15 (2H, m,
COCH CH CH COOH), δ 2.03 (2H, m, COCH CH CH COOH),
δ 1.66 (2H, m, COCH CH CH COOH); ESI-MS m/z 314 (M ).
Anal. (C13 16BrNO ) C, N; H: calcd, 5.13; found, 5.08.
4
2
2
2
2
mixture of glutaric anhydride (299 mg, 2.62 mmol) and (p-
chlorophenyl)ethylamine (340 mg, 2.19 mmol) in acetonitrile
2
2
2
2
2
2
+
2
2
2
1
(30 mL) gave 27 (84 mg, 86%): H NMR (DMSO-d
6
, 300 MHz)
H
3
δ 7.86 (1H, t, NHCH
dd, Ar-H), δ 3.24 (2H, m, NHCH
NHCH CH
2H, m, COCH
2
CH
2
Ar), δ 7.31 (2H, m, Ar-H), δ 7.20 (2H,
CH Ar), δ 2.66 (2H, t,
Ar), δ 2.14 (2H, m, COCH CH CH COOH), δ 2.05
CH CH COOH), δ 1.65 (2H, m, COCH CH
COOH); ESI-MS m/z 269 (M ). Anal. (C13 16ClNO ) C:
N-P h en ylsu ccin a m ic Acid (32). The mixture of succinic
2
2
anhydride (262 mg, 2.62 mmol) and aniline (203 mg, 2.19
1
2
2
2
2
2
mmol) in acetonitrile (30 mL) gave 32 (149 mg, 21%): H NMR
(
2
2
2
2
2
-
(DMSO-d
6
, 300 MHz) δ 9.92 (1H, s, NHAr), δ 7.58 (2H, d, Ar-
+
CH
2
H
3
H), δ 7.28 (2H, t, Ar-H), δ 7.0 (1H, m, Ar-H), δ 2.57 (4H, br,
+
calcd, 57.89; found, 57.44, H: calcd, 5.98; found, 6.01, N: calcd,
COCH
2 2 3
CH COOH); ESI-MS m/z 193 (M ). Anal. (C10H11NO )
5
.19; found, 5.08.
C, N; H: calcd, 5.74; found, 5.70.
N-2-(p -Br om op h en yl)et h ylsu ccin a m ic Acid (28). The
N-P h en ylm a lea m ic Acid (33). The mixture of maleic
mixture of succinic anhydride (262 mg, 2.62 mmol) and (p-
anhydride (256 mg, 2.62 mmol) and aniline (203 mg, 2.19
mmol) in acetonitrile (30 mL) gave 33 (605 mg, 87%): H NMR
1
bromophenyl)ethylamine (437 mg, 2.19 mmol) in acetonitrile
1
(
30 mL) gave 28 (738 mg, 67%): H NMR (DMSO-d
6
, 300 MHz)
6
(DMSO-d , 300 MHz) δ 10.38 (1H, s, NHAr), δ 7.62 (2H, d,
δ 7.45 (2H, d, Ar-H), δ 7.15 (2H, d, Ar-H), δ 3.20 (2H, m,
NHCH CH Ar), δ 2.64 (2H, t, NHCH CH Ar), δ 2.49 (2H, t,
COCH CH COOH), δ 2.26 (2H, t, COCH CH COOH); ESI-MS
m/z 300 (M ). Anal. (C12 ) C, N; H: calcd, 6.33; found,
.43.
N-2-(p-Br om oph en yl)eth ylm aleam ic Acid (29). The mix-
Ar-H), δ 7.32 (2H, m, Ar-H), δ 7.08 (H, t, Ar-H), δ 6.47 (1H, d,
2
2
2
2
COCH ) CHCOOH), δ 6.3 (1H, d, COCHdCHCOOH); ESI-
+
2
2
+
2
2
MS m/z 191 (M ). Anal. (C10
H
9
NO
3
) C, N; H: calcd, 4.74; found,
H
14BrNO
3
4.68.
6
N-P h en ylp h th a la m ic Acid (34). The mixture of phthalic
anhydride (390 mg, 2.62 mmol) and aniline (203 mg, 2.19
1
ture of maleic anhydride (256 mg, 2.62 mmol) and (p-bro-
mmol) in acetonitrile (30 mL) gave 34 (316 mg, 36%): H NMR
mophenyl)ethylamine (437 mg, 2.19 mmol) in acetonitrile (30
6
(DMSO-d , 300 MHz) δ 10.3 (1H, s, NHAr), δ 7.91 (1H, d,
1
mL) gave 29 (543 mg, 50%): H NMR (DMSO-d
6
, 300 MHz),
COPhCOOH), δ 7.62 (2H, m, COPhCOOH), δ 7.6 (1H, m, Ar-
δ 7.47 (2H, d, Ar-H), δ 7.18 (2H, d, Ar-H), δ 6.35 (1H, t, COCH
CHCOOH), δ 6.21 (1H, t, COCHdCHCOOH), δ 3.16 (2H,
m, NHCH CH Ar), δ 2.74 (2H, t, NHCH CH Ar); ESI-MS m/z
98 (M ). Anal. (C12 12BrNO ) C, N; H: calcd, 4.06; found,
.02.
H), δ 7.59 (2H, d, Ar-H), δ 7.3 (2H, d, Ar-H), δ 7.05 (1H, d,
+
)
COPhCOOH); ESI-MS m/z 241 (M ). Anal. (C14
H
11NO
3
) C, N;
2
2
2
2
H: calcd, 4.60; found, 4.53.
N-P h en ylglu ta r a m ic Acid (35). The mixture of glutaric
anhydride (299 mg, 2.62 mmol) and aniline (203 mg, 2.19
+
2
4
H
3

5
626 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 26
Sun et al.
mmol) in acetonitrile (30 mL) gave 35 (257 mg, 34%): 1H NMR
δ 7.93 (1H, d, NCCH ) CHCHdCH), δ 7.63 (1H, dd, NCCHd
CHCHdCH), δ 7.32 (1H, d, NCH ) CH), δ 7.25 (1H, d, NCHd
CH), δ 6.76 (1H, m, NCCHdCHCH ) CH), δ 3.25 (2H, t,
(
DMSO-d , 300 MHz) δ 9.86 (1H, s, NHAr), δ 7.58 (2H, d, Ar-
H), δ 7.3 (2H, t, Ar-H), δ 6.98 (H, dd, Ar-H), δ 2.23 (4H, m,
COCH CH CH CH CH COOH);
) C, H; N: calcd, 6.33;
6
2
2
2
COOH), δ 1.81 (2H, m, COCH
2
2
2
COCH
2
CH
2
+
COOH), δ 2.66 (2H, t, COCH
2
CH
2
COOH); ESI-MS
+
ESI-MS m/z 207 (M ). Anal. (C11
H
13NO
3
m/z 217 (M ). Anal. (C12H11NO ) C, H; N: calcd, 6.45; found,
3
found, 6.43.
6.36.
N-Ben zylsu ccin a m ic Acid (36). The mixture of succinic
anhydride (262 mg, 2.62 mmol) and benzylamine (234 mg, 2.19
mmol) in acetonitrile (30 mL) gave 36 (172 mg, 23%): 1H NMR
4-Oxo-4-in d ole-cis-2-bu ten eoic Acid (44). The mixture
of maleic anhydride (256 mg, 2.62 mmol), indole (256 mg, 2.19
mmol) and TEA (3 mL, 21.87 mmol) in acetonitrile (30 mL)
gave 44 (144 mg, 18%): 1H NMR (DMSO-d
, 300 MHz), δ 12.26
(
DMSO-d
Ar-H), δ 7.21 (2H, d, Ar-H), δ 4.25 (2H, d, NHCH
2H, t, COCH CH CH
) C, H; N: calcd, 6.33;
6
, 300 MHz) δ 8.35 (1H, s, NHCH
2
Ar), δ 7.32 (3H, d,
Ar), δ 2.44
COOH);
6
(1H, s, COCH CH COOH), δ 8.33 (1H, d, NCCHdCHCHdCH),
2 2
2
(
2
2
COOH), δ 2.39 (2H, t, COCH
2
2
δ 7.93 (1H, d, NCCH ) CHCHdCH), δ 7.63 (1H, dd, NCCHd
CHCHdCH), δ 7.32 (1H, d, NCH ) CH), δ 7.25 (1H, d, NCHd
CH), δ 6.76 (1H, m, NCCHdCHCH ) CH), δ 6.45 (1H, d,
+
ESI-MS m/z 207 (M ). Anal. (C11H13NO
3
found, 6.43.
COCH ) CHCOOH), δ 6.33 (1H, d, COCHdCHCOOH); ESI-
N-Ben zylm a lea m ic Acid (37). The mixture of maleic
+
MS m/z 215 (M ). Anal. (C12
9 3
H NO ) C: calcd, 66.97; found,
anhydride (256 mg, 2.62 mmol) and benzylamine (234 mg, 2.19
mmol) in acetonitrile (30 mL) gave 37 (203 mg, 27%): 1H NMR
57.38, H: calcd, 4.22; found, 4.39, N: calcd, 6.51; found, 5.31.
-Oxo-5-in d olep en ta n oic Acid (45). The mixture of glu-
5
(
DMSO-d
m, Ar-H), δ 6.44 (1H, d, COCH ) CHCOOH), δ 6.26 (1H, d,
COCHdCHCOOH), δ 4.39 (2H, d, NHCH Ar); ESI-MS m/z 205
) C, H; N: calcd, 6.33; found, 6.43.
N-Ben zylp h th a la m ic Acid (38). The mixture of phthalic
6
, 300 MHz) δ 9.39 (1H, s, NHCH
2
Ar), δ 7.34 (5H,
taric anhydride (299 mg, 2.62 mmol), indole (256 mg, 2.19
mmol) and TEA (3 mL, 21.87 mmol) in acetonitrile (30 mL)
2
gave 45 (471 mg, 56%): 1H NMR (DMSO-d , 300 MHz), δ 8.33
+
(M ). Anal. (C11
H
11NO
3
6
(
1H, d, NCCHdCHCHdCH), δ 7.86 (1H, d, NCCH ) CHCHd
CH), δ 7.60 (1H, dd, NCCHdCHCHdCH), δ 7.30 (1H, d, NCH
) CH), δ 7.24 (1H, d, NCHdCH), δ 6.73 (1H, m, NCCHd
anhydride (390 mg, 2.62 mmol) and benzylamine (234 mg, 2.19
mmol) in acetonitrile (30 mL) gave 38 (259 mg, 28%): 1H NMR
CHCH ) CH), δ 3.04 (2H, t, COCH
2H, t, COCH CH CH COOH), δ 1.90 (2H, t, COCH
COOH); ESI-MS m/z 231 (M ). Anal. (C13
67.52, found, 68.31, N: calcd, 6.06; found, 6.21.
-Oxo-4-(4-h yd r oxyin d ole)bu ta n oic Acid (46). The mix-
2
CH
2
CH
2
COOH), δ 2.36
CH CH
3
13NO ) H; C: calcd,
(
DMSO-d
COPhCOOH), δ 7.5 (2H, m, COPhCOOH), δ 7.3 (5H, br, Ar-
Ar); ESI-
) C, N, H: calcd, 5.13;
6
, 300 MHz) δ 8.83 (1H, s, NHCH
2
Ar), δ 7.76 (1H, s,
(
2
2
2
2
2
2
-
+
H
H), δ 7.2 (1H, d, COPhCOOH), δ 4.43 (2H, d, NHCH
MS m/z 255 (M ). Anal. (C15H13NO
3
2
+
4
found, 5.08.
ture of succinic anhydride (262 mg, 2.62 mmol), 4-hydroxyin-
dole (291 mg, 2.19 mmol) and TEA (3 mL, 21.87 mmol) in
acetonitrile (30 mL) gave 46 (300 mg, 33%): 1H NMR (DMSO-
N-Ben zylglu ta r a m ic Acid (39). The mixture of glutaric
anhydride (299 mg, 2.62 mmol) and benzylamine (234 mg, 2.19
mmol) in acetonitrile (30 mL) gave 39 (123 mg, 16%): 1H NMR
d , 300 MHz), δ 7.80 (1H, d, NCCH ) CHCHdCH), δ 7.77 (1H,
6
(
DMSO-d
m, Ar-H), δ 7.22 (2H, dd, Ar-H), δ 4.24 (2H, d, NHCH
.2 (4H, m, COCH CH CH COOH), δ 1.7 (2H, m, COCH
CH COOH); ESI-MS m/z 221 (M ). Anal. (C12
N: calcd, 6.33; found, 6.36.
-Oxo-4-(2,3-d ih yd r oin d ole)bu ta n oic Acid (40). The
mixture of succinic anhydride (262 mg, 2.62 mmol), indoline
260 mg, 2.19 mmol) and TEA (3 mL, 21.87 mmol) in aceto-
6
, 300 MHz) δ 8.32 (1H, s, NHCH
2
Ar), δ 7.29 (3H,
Ar), δ
CH
) C, H;
d, NCCHdCHCH ) CH), δ 7.10 (1H, m, NCH ) CH), δ 6.78
2
(
(
1H, dd, NCCHdCHCHdCH), δ 6.65 (1H, d, NCHdCH), δ 3.22
2H, t, COCH CH COOH), δ 2.62 (2H, t, COCH CH COOH);
) H; C: calcd, 61.80;
found, 61.20, N: calcd, 6.01; found, 5.87.
2
2
2
2
2
2
-
+
2
2
2
2
2
H15NO
3
+
ESI-MS m/z 233 (M ). Anal. (C12H11NO
4
4
F lexible Dock in g. The structures of the ligands were
prepared in MOL2 format using the sketcher module of Sybyl
(
47
6
.8 and Gasteiger-Huckel charges were assigned to the
1
nitrile (30 mL) gave 40 (171 mg, 21%): H NMR (DMSO-d
6
,
ligand atoms. The minimization was run until converged to a
3
00 MHz), δ 12.09 (1H, s, COCH CH COOH), δ 8.04 (1H, d,
2
2
-1
-1
maximum derivative of 0.001 kcal mol
Å , and the final
NCCH ) CHCHdCH), δ 7.22 (1H, dd, NCCHdCHCH ) CH),
coordinates were stored in database. The X-ray crystal struc-
δ 7.13 (1H, dd, NCCHdCHCHdCH), δ 6.97 (1H, t, NCCHd
+
ture of porcine ALR2 complexed with NADP and tolrestat
CHCHdCH), δ 4.09 (2H, t, NCH
2
CH
2
), δ 3.14 (2H, t, NCH
2
CH
CH
3
COOH); ESI-MS m/z 219 (M ). Anal. (C12H13NO ) C, H; N:
2
),
2
-
(pdb entry ) 1AH3) were retrieved from the Protein Data
δ 2.67 (2H, t, COCH
2
CH
2
COOH), δ 2.51 (2H, t, COCH
2
Bank (PDB). The active site was defined as all the amino acid
residues enclosed within 6.5 Å radius sphere centered by the
bound ligand, tolrestat. The docking and subsequent scoring
were performed using the default parameters of the FlexX
program implanted in the Sybyl 6. 8. For the docking of the
ligand library into the target active site, the main settings are
+
calcd, 6.33; found, 6.43.
4
-Oxo-4-(2,3-d ih yd r oin d ole)-cis-2-bu ten eoic Acid (41).
The mixture of maleic anhydride (256 mg, 2.62 mmol), indoline
260 mg, 2.19 mmol) and TEA (3 mL, 21.87 mmol) in aceto-
(
1
nitrile (30 mL) gave 41 (318 mg, 40%): H NMR (DMSO-d
6
,
1
000 solutions per iteration during the incremental construc-
3
00 MHz), δ 12.8 (1H, s, COCHdCHCOOH), δ 8.03 (1H, d,
tion algorithm and a maximum protein-ligand atom-atom
NCCH ) CHCHdCH), δ 7.24 (2H, m, NCCHdCHCH ) CH),
3
overlap of 2.5 Å . Final scores for all FlexX solutions (up to
δ 7.18 (1H, dd, NCCHdCHCHdCH), δ 7.90 (1H, d, COCH )
1
000) per compound were calculated by consensus scoring
program, Cscore, and used for database ranking.
D QSAR. Hydrophobic, donor, and acceptor fields were
CHCOOH), δ 6.12 (1H, d, COCHdCHCOOH), δ 3.98 (2H, t,
+
NCH
Anal. (C12
-Oxo-5-(2,3-d ih yd r oin d ole)p en ta n oic Acid (42). The
mixture of glutaric anhydride (299 mg, 2.62 mmol), indoline
260 mg, 2.19 mmol) and TEA (3 mL, 21.87 mmol) in aceto-
2
CH
2
), δ 3.1 (2H, t, NCH
2
CH
2
); ESI-MS m/z 217 (M ).
3
H
11NO ) C, N; H: calcd, 5.10; found, 5.15.
3
calculated with CoMSIA (Comparative Molecular Field Analy-
sis) module integrated in SYBYL 6.8. For building the pseudo
receptor, the hydrogen bond donor, the hydrogen bond accep-
5
(
3
tor, and the hydrophobic fields are considered. An sp carbon
1
nitrile (30 mL) gave 42 (211 mg, 25%): H NMR (DMSO-d
00 MHz) δ 8.04 (1H, d, NCCHdCHCHdCH), δ 7.20 (1H, m,
NCCHdCHCHdCH), δ 7.71 (1H, m, NCCHdCHCH ) CH), δ
.95 (1H, dd, NCCHdCHCHdCH), δ 4.03 (2H, t, NCH CH ),
δ 3.11 (2H, t, NCH CH ), δ 2.48 (2H, t, COCH CH CH COOH),
δ 2.29 (2H, t, COCH CH CH COOH), δ 1.78 (2H, t, COCH CH
CH COOH); ESI-MS m/z 233 (M ). Anal. (C13 ) H; C:
calcd, 66.94; found, 67.52, N: calcd, 6.00; found, 6.11.
-Oxo-4-in d olebu ta n oic Acid (43). The mixture of suc-
6
,
atom with a +1.0 charge was selected as a probe for the
calculation of hydrophobic, donor, and acceptor, filtered at 8
kcal/mol. The FlexX-docked alignment of top-scoring confor-
mations was used for 3D QSAR analysis.
3
6
2
2
2
2
2
2
2
-
Refer en ces
2
2
2
2
2
+
2
H15NO
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