Design, synthesis and antifungal activity of isosteric analogues of benzoheterocyclic N-myristoyltransferase inhibitors

Article abstract of DOI:10.1016/j.ejmech.2010.03.007

N-myristoyltransferase (NMT) has been a promising new target for the design of novel antifungal agents with new mode of action. A series of benzoxazole and indole derivatives were designed and synthesized as isosteric analogues of benzoheterocyclic NMT Inhibitors. In vitro antifungal assay indicated that the benzoxazole derivatives were far more potent than the indoles. Molecular docking studies revealed that the hydrogen bonding interaction between the benzoheterocyclic core and NMT might be essential in the orientation of the inhibitor to a proper position. The antifungal activity of benzoxazole derivative 8f was comparable or superior to that of fluconazole, which can serve as a good starting point for further studies of structural diversity of the benzoheterocyclic NMT inhibitors. A series of benzoxazole and indole derivatives were designed and synthesized as isosteric analogues of benzoheterocyclic NMT Inhibitors. The binding mode was investigated by molecular docking.

Full text of DOI:10.1016/j.ejmech.2010.03.007

European Journal of Medicinal Chemistry 45 (2010) 3531e3540
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis and antifungal activity of isosteric analogues of
benzoheterocyclic N-myristoyltransferase inhibitors
Chunquan Sheng a, Hui Xu a, Wenya Wang a, Yongbing Cao a, Guoqiang Dong a, Shengzheng Wang a,
,
c
,
,
*
Xiaoying Che a, Haitao Ji b d, Zhenyuan Miao a, Jianzhong Yao a, Wannian Zhang a
a School of Pharmacy, Second Military Medical University, 325 Guohe Road, Shanghai 200433, PR China
b Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA
c Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208-3113, USA
d Center for Drug Discovery and Chemical Biology, Northwestern University, Evanston, IL 60208-3113, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
N-myristoyltransferase (NMT) has been a promising new target for the design of novel antifungal agents
with new mode of action. A series of benzoxazole and indole derivatives were designed and synthesized
as isosteric analogues of benzoheterocyclic NMT Inhibitors. In vitro antifungal assay indicated that the
benzoxazole derivatives were far more potent than the indoles. Molecular docking studies revealed that
the hydrogen bonding interaction between the benzoheterocyclic core and NMT might be essential in the
orientation of the inhibitor to a proper position. The antifungal activity of benzoxazole derivative 8f was
comparable or superior to that of fluconazole, which can serve as a good starting point for further studies
of structural diversity of the benzoheterocyclic NMT inhibitors.
Received 4 November 2009
Received in revised form
3 March 2010
Accepted 6 March 2010
Available online 12 March 2010
Keywords:
Benzoxazole
Indole
Ó 2010 Elsevier Masson SAS. All rights reserved.
N-Myristoyltransferase inhibitors
Antifungal activity
1. Introduction
drugs has also been observed [9]. Therefore, there is an emergent
need to develop new antifungal drugs with novel modes of action.
During the past two decades, the incidence of systemic fungal
infections has been increasing dramatically due to the increasing
number of immunocompromised hosts, such as patients under-
going anticancer chemotherapy or organ transplants, and patients
with AIDS [1]. Clinically, candidosis, aspergillosis and cryptococ-
cosis have been identified as three major fungal infections [2,3]. The
mortality rate associated with invasive Candida is approximately
40% [4], whereas associated with invasive Aspergillus reaches 100%
in solid organ transplant recipients [5]. In contrast to the large
number of antibacterial antibiotics, there are very few antifungal
agents that can be used for life-threatening fungal infections. These
drugs are amphotericin B [6], 5-fluorocytosine, azoles (such as
fluconazole and itraconazole) [7], and echinocandins (such as
caspofungin and micafungin) [8]. However, current antifungal
therapy is far from satisfaction, because currently available anti-
fungal agents have several drawbacks, such as drug related toxicity,
severe drug resistance, non-optimal pharmacokinetics, and serious
drugedrug interactions. Moreover, severe resistance of antifungal
Myristoyl-CoA: protein N-myristoyltransferase (NMT) is a cyto-
solic monomeric enzyme that catalyzes the transfer of the myri-
stoyl group from myristoyl-CoA to the N-terminal glycine of
a number of eukaryotic cellular and viral proteins [10,11]. Genetic
experiments have shown that NMT is a promising target enzyme
for the development of novel fungicidal drugs having a broad
antifungal spectrum [12]. Up to now, peptidomimetic inhibitors
[13e16], myristic acid analogues [17,18], benzofuran inhibitors
[19e23] and benzothiazole inhibitors [23,24] have been reported to
possess NMT inhibitory activity. Among them, only the benzofuran
and benzothiazole inhibitors showed high selectivity and good
antifungal activity. They can serve as a good starting point for the
discovery of novel antifungal agents. Therefore, the extension of
structureeactivity relationships (SARs) of these NMT inhibitors is of
great importance.
Analysis of the chemical structure of the benzofuran and
benzothiazole inhibitors reveals that they share three important
chemical elements (Fig.1), i.e. a benzoheterocyclic core, a secondary
amine at its C-4 side chain, a hydrophobic group attached to its C-2
position through various linkers. Crystal structure of NMT inhibitor
complex [25] and our docking studies [26] found that the benzo-
heterocyclic core was located at the center of the active site,
* Corresponding author. Tel./fax: þ86 021 81871243.
E-mail address: zhangwnk@hotmail.com (W. Zhang).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.03.007

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C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
Fig. 1. Representative structures of the benzofuran and benzothiazole NMT inhibitors.
surrounded by some hydrophobic residues, such as Tyr225, Tyr354
and Leu394. In an effort to investigate the importance of the ben-
zoheterocyclic core on the antifungal activities, we designed and
synthesized a series of benzoxazole and indoleanalogues as isosteric
analogues of benzoheterocyclic NMT Inhibitors.
Starting from salicylaldehyde (9), the indole intermediate 12
was synthesized by a four-step procedure (Scheme 2). Initially, the
hydroxyl group of 9 was protected by benzyl bromide. Then,
compound 10 was condensed with ethyl azidoacetate to form an
intermediate azide. By the thermal cycliation of the azide in
toluene at reflux, indole 11 was obtained, which was deprotected
to give key intermediate 12. Treatment of 12 with excess 1,3-
dibromopropane in the presence of potassium carbonate in DMF
gave O-bromopropanyl derivative 13. Amination of 13 with 3-
(aminomethyl)pyridine at 75 ꢀC in EtOH gave amino derivative 14
without affecting the ester group. The target compounds 16aeb
were prepared by Mitsunobu reaction of appropriate phenols with
alcohol 15 [20], which was obtained by the reduction of ester 14
with LiAlH4.
Compounds 20aee were prepared following the route depic-
ted in Scheme 3. Ester 13 was hydrolyzed by lithium hydroxide,
and the resulting acid 18 was converted into its acid chloride by
treatment with oxalyl chloride, which was immediately sub-
jected to the next anilide formation reaction. The resulting
amides 19aee was heated to 75 ꢀC with 3-aminomethylpyridine
in EtOH to give 20aee.
2. Chemistry
The synthetic route of benzoxazole derivatives was outlined in
Scheme 1. 2-Nitroresorcinol (1) was reduced to 2-aminoresorcinol
(2) by catalytic hydrogenation with H2 and 10% Pd/C in EtOH in 99%
yield. Reaction of 2 with ethyl chloroacetimidate gave 2-(chloro-
methyl)benzoxazol-4-ol (3). The hydroxyl group of 3 was protected
by (Boc)2O to give 4. In the presence of NaH, treatment of 4 with
various substituted phenols in DMF at room temperature provided
the ethers 5aeh. After removing the protecting group of
compounds 5aeh using CF3COOH, alkylation of the resulting 6aeh
with excess 1,3-dibromopropane gave bromopropanyl derivatives
7aeh in good yields. The target benzoxazoles 8aeh were prepared
by reacting 7aeh with 3-(aminomethyl)pyridine in EtOH at 75 ꢀC
with moderate to good yields.
Scheme 1. Reagents and conditions: a: H2, 10% Pd/C, EtOH; b: ClCH2C(]NH)OC2H5$HCl, 0 ꢀC; c: Boc2O, CH2Cl2; d: ROH, NaH, DMF; e: CF3COOH, CH2Cl2; f: 1,3-dibromopropane,
K2CO3, DMF, rt; g: 3-(Aminomethyl)pyridine, EtOH, 75 ꢀC.

C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
3533
Scheme 2. Reagents and conditions: a: benzyl bromide, 70 ꢀC, reflux; b; Ethyl azidoacetate, NaOEt, EtOH, ꢁ10 ꢀC; c: toluene, 120 ꢀC, reflux; d: H2, 10% Pd/C, EtOH, 50 ꢀC; e: 1,3-
dibromopropane, K2CO3, DMF, rt; f: 3-(Aminomethyl)pyridine, EtOH, 75 ꢀC, reflux; g: LiAlH4, THF, 0 ꢀC; h: TBP, ADDP, phenols, CH2Cl2, ꢁ20 ꢀC to rt. i: CF3COOH, benzenethiols,
CH2Cl2, rt.
3. Pharmacology
FluconazoleandbenzofuranNMT inhibitors(RO-09-4609andRO-09-
4879) were used as reference drugs. Test fungal strains were obtained
from the ATCC or were clinical isolates. The MIC determination was
performed according to the National Committee for Clinical
In vitro antifungal activity was measured by means of the MIC
using the serial dilution method in 96-well microtest plates.
Scheme 3. Reagents and conditions: a: LiOH, HCl, THF/MeOH, 0 ꢀC, 6 h; b: Oxalyl chloride, Et3N, CH2Cl2, rt, 12 h; c: substituted-anilines, CH2Cl2, rt, 3 h; d: 3-(Aminomethyl)pyridine,
EtOH, 75 ꢀC, reflux,12 h.

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C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
Table 2
Laboratory Standards (NCCLS) recommendations. The detailed
experimental protocols can be found in our previous studies [27].
Antifungal in vitro activities of the indole derivatives (MIC80, m
g mLꢁ1).a
Compounds
M. gyp.
T. rub.
C. alb.
C. neo.
A. fum.
14
16a
16b
17a
17b
20a
20b
20c
20d
20e
RO-09-4609
RO-09-4879
FLZ
32
8
32
8
64
32
128
64
16
64
128
64
32
128
4
>128
>128
>128
128
64
128
>128
>128
>128
>128
1
>128
64
128
64
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>64
4. Results and discussion
4.1. Antifungal activity of the benzoxazole derivatives
4
64
32
32
32
16
2
4
2
16
128
>128
>128
128
>128
64
The antifungal activity of each compound was expressed as the
minimal inhibitory concentration (MIC) that achieved 80% inhibi-
tion of the tested fungi. In vitro antifungal activity assay (Table 1)
indicated that the benzoxazole derivatives 8aeh showed moderate
to good potency against Candida spp. In general, these compounds
were more active against Candida parasilosis and Candida tropicalis
than Candida albicans. All the compounds showed better activity
against C. tropicalis than fluconazole with their MIC values in the
1
1
0.125
0.25
0.5
2
16
>64
a
Abbreviations: M. gyp. Microsporum gypseum; T. rub. Trichophyton rubrum; C. alb.
Candida albicans; C. neo. Cryptococcus neoformans; A. fum. Aspergillus fumigatus; FLZ:
Fluconazole.
range of 1
more active against C. tropicalis (MIC ¼ 0.0625
benzofuran inhibitor RO-09-4609 and RO-09-4879. On the C. par-
g/mL) were more
mg/mL to 0.0625
m
g/mL. Moreover, compound 8a was
mg/mL) than
slightly improvement of the antifungal activity. Compounds 17a
and 17b show marginal activity against deep fungal pathogens. For
the dermatophytes, their MIC values were in the range of 4
asilosis strain, compounds 8d and 8f (MIC ¼ 0.25
m
potent than fluconazole and RO-09-4609. However, they were
4-fold less potent than RO-09-4879. Most of the compounds
showed moderate activity against C. albicans except for compound
mg/mL
to 64 g/mL. They showed better inhibitory activity against
m
M. gypseum than fluconazole. If the thio-ether group is replaced by
the amide group (compounds 20aee), their antifungal activity
against deep fungal pathogens is lost again. Most of compounds
20a-e only showed moderate activity against dermatophytes with
8f. For C. albicans, the MIC value of compound 8f was 0.25 mg/mL,
which was comparable to that of fluconazole. However, it was
2-fold less active than RO-09-4879. As compared with Candida spp.,
the inhibitory activity of the compounds against Cryptococcus
neoformans was decreased. The MIC values for the most of the
MIC values in the range of 2 mg/mL to 64 mg/mL.
compounds were in the range of 16 mg/mL to 64 mg/mL. Moreover,
most of the compounds were inactive against Aspergillus fumigatus
and only compound 8g showed marginal inhibitory activity
4.3. SARs of the benzoxazole and indole derivatives
In vitro antifungal assay indicated that the benzoheterocyclic
core of the benzofuran and benzothiazole NMT inhibitors was
important for the antifungal activity. When the benzofuran scaffold
was replaced by benzoxazole, the antifungal was retained. The
antifungal activity of compound 8f was slightly less than that of
RO-09-4879. However, the antifungal activity of corresponding
indole analogues was almost lost. For the benzoxazole derivatives,
the substitutions on the phenyl ring were important for the anti-
fungal activity. In general, a nitro group at position 3 of the phenyl
group (compound 8h) was unfavorable for the antifungal activity.
When the phenyl group of compound 8c was substituted with one
or more fluorine atoms, the antifungal activity was increased. In
most cases, the antifungal activity increased as the increase of the
number of the fluorine atoms on the phenyl ring. For example,
compound 8f (2,3,4-trifluoro derivative) was the most active
compound with broad antifungal spectrum. However, fluorine
substitutions at both position 2 and 6 of the phenyl group led to the
decrease of the antifungal activity. For example, the movement of
the fluorine atom from position 4 (compound 8d) to position 6
(compound 8e) resulted in obvious decrease of the antifungal
activity. The similar results can be found in compounds 8f and 8g.
For the indole derivatives, the variation of the linker of C-2 side
chain can slightly improve the antifungal activity. The thio-ether
group was more favorable than ether or amide group.
(MIC ¼ 64
mg/mL). Among the benzoxazole derivatives, compound
8f was the most potent one with broad antifungal spectrum, which
was worthy of further optimization.
4.2. Antifungal activity of the indole derivatives
When the benzoxazole scaffold of compounds 8aeh was
changed to indole, the antifungal activity was decreased to the
large extent (Table 2). The loss of the antifungal activity against
deep fungal pathogens (i.e. C. albicans, C. parasilosis and C. tropicalis)
was observed for compounds 16a and 16b. Only compound 16a
showed marginal activity against C. neoformans (MIC ¼ 64
mg/mL).
Furthermore, we tested the inhibitory activity of indole derivatives
against dermatophytes. Compounds 16a and 16b showed moderate
activity against Microsporum gypseum and Trichophyton rubrum
with their MIC values in the range of 8 mg/mL to 128 mg/mL. We
further varied the linker between the phenyl group and indole ring.
The replacement of ether group by the thio-ether group led to the
Table 1
Antifungal in vitro activities of the benzoxazole derivatives (MIC80
,
m
g mLꢁ1).a
A. fum.
Compounds
C. alb.
C. par.
C. tro.
C. neo.
8a
8b
8c
8d
8e
8f
8g
8h
4
16
16
1
64
0.25
16
>64
4
0.125
0.25
1
1
1
0.25
4
0.25
1
4
0.0625
1
0.25
1
1
0.25
1
0.25
1
0.125
4
16
16
64
16
64
64
16
>64
64
0.5
1
>64
>64
>64
>64
>64
>64
64
>64
>64
16
4.4. Molecular docking studies
In an attempt to correlate the SARs with the binding mode of the
synthesized compounds, two representative compounds, 8f and
16a, were docked into the crystal structure of NMT from C. albicans
(CaNMT) [25]. Our previous modeling studies have proved that the
affinity method within InsightII 2000 software package [28] was an
effective method to investigate the binding mode of the NMT
inhibitors [26]. The docking results of compounds 8f and 16a were
shown in Fig. 2. The overall conformation of compound 8f in the
RO-09-4609
RO-09-4879
FLZ
4
0.0625
4
>64
a
Abbreviations: C. alb. Candida albicans; C. par. Candida parasilosis; C. tro. Candida
tropicalis; C. neo. Cryptococcus neoformans; A. fum. Aspergillus fumigatus; FLZ:
Fluconazole.

C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
3535
Fig. 2. Stereoview of the docking conformation of compound 8f (A) and 16a (B) in the active site of CaNMT. The residues interacting with compound 8f and 16a are shown and
hydrogen bonds are displayed through red dotted lines (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).
active site of CaNMT was very similar to that of the benzofuran
inhibitors (Fig. 2A). The benzoxazole ring was located at the center
of the active site, surrounded by some hydrophobic residues, such
as Tyr225, Tyr354 and Leu394. The phenyl part of the benzoxazole
isostreric design of the benzoxazole and indole derivatives. In
vitro antifungal assay indicated that the replacement of benzo-
furan scaffold by benzoxazole led to a slight decrease of the
antifungal activity. However, the antifungal activity of the indole
derivatives was almost lost. They only showed moderate activity
against dermatophytes. The binding mode of the synthesized
compounds was explored by flexible molecular docking, which
indicated the importance of the hydrogen bonding interaction
between the benzoheterocyclic core and NMT in the orientation
of the inhibitor to a proper position. The benzoxazole derivative
8f showed good antifungal activity with broad spectrum, which
was comparable or superior to fluconazole. Although compound
8f is slightly less potent than RO-09-4879, it is more drug-like
with lower molecular weight and hydrophobicity, which can
serve as a good starting point for further studies of structural
diversity of the NMT inhibitors.
ring could form
p-p interaction with Tyr225. The substituted
phenyl group of C-2 side chain formed hydrophobic interaction
with Phe115 and Phe240. The terminal pyridinyl group C-4 side
chain was surrounded by hydrophobic aromatic residues, such as
Tyr119 and Phe123. Four hydrogen bonds were observed between
compound 8f and CaNMT. The second amine group of C-4 side
chain made a hydrogen bond with C-terminal carboxylate of
Leu451, which is an important functional residue in the catalytic
cycle of CaNMT [25]. The oxygen and nitrogen atom of the benz-
oxazole ring formed two hydrogen bonds with His227 and Tyr354,
respectively. Another hydrogen bond was formed between the
pyridine nitrogen of C-4 side chain and Tyr119 hydroxyl group.
Among them, hydrogen bonding interactions with His227, Tyr119
and Leu451 of compound 8f are identical to those of benzofuran
inhibitor RO-09-4879. In the crystal complex of CaNMT [25], the
ether oxygen of C-2 side chain made a hydrogen bond with Asn392.
However, this hydrogen bond was lost for compound 8f, mainly
because of the additional hydrogen bond between benzoxazole
nitrogen and Tyr354. As compared with compound 8f, RO-09-4879
has a C-3 methyl group, which can form additional van der Waals
interaction with CaNMT. As a result, the interaction energy of RO-
09-4879 with CaNMT was a little lower than compound 8f.
6. Experimental protocols
6.1. Chemistry
Melting points (mp) were determined by microscope melting
point apparatus with aromatic temperature control system (XT4A).
Nuclear magnetic resonance (NMR) spectra were recorded on
a Bruker 500 spectrometer with TMS as an internal standard and
d6-DMSO as solvent. Chemical shifts (
d values) and coupling
It is interesting that compound 16a shared a completely
different conformation in the active site of CaNMT (Fig. 2B). Instead
of the C-4 secondary amine, the indole nitrogen formed a weak
hydrogen bond with Leu451. As a result, important hydrogen
bonding and hydrophobic interactions observed for compound 8f
were lost. The docking result is supported by the weak antifungal
activity of compound 16a. Based on the above docking results, it is
supposed that the hydrogen bonding interactions between the
benzoheterocyclic core and CaNMT might be essential for orienting
the inhibitor to the correct direction in the active site.
constants (J values) are given in ppm and Hz, respectively. ESI mass
spectra were performed on an API-3000 LCeMS spectrometer.
High-resolution mass spectroscopy measurements were performed
on a Kratos-concep mass spectrometer under electron impact
ionization (EI) conditions. Elemental analyses were performed with
a MOD-1106 instrument and were consistent with theoretical
values within ꢂ0.4%. TLC analysis was carried out on silica gel plates
GF254 (Qindao Haiyang Chemical, China). Silica gel column chro-
matography was performed with Silica gel 60 G (Qindao Haiyang
Chemical, China). Commercial solvents were used without any
pretreatment.
5. Conclusion
6.1.1. Chemical synthesis of 2-aminobenzene-1,3-diol (2)
In summary, we have extended the SARs of the benzofuran and
benzothiazole NMT inhibitors. The importance of benzohetero-
cyclic core on the antifungal activity was investigated by the
10% PdeC (2.0 g) was added to a solution of 2-nitrobenzene-1,3-
diol (31.0 g, 0.2 mol) in EtOH (500 mL), then the reaction mixture
was put into the high-pressure reaction vessel under H2

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C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
atmosphere at 4 atm and stirred at room temperature for 10 h. The
mixture was filtered though celite and the resulting solution was
dried over anhydrous MgSO4, concentrated under reduced pressure
concentrated under reduced pressure. The residue was purified by
silica gel column chromatography (hexane/EtOAc ¼ 50:1, v/v) to
give compounds 7aeh.
to give 2 as brown solid (49.5 g, 99% yield). 1H NMR
d (ppm): 8.82 (s,
2H, OH), 6.21e6.27 (m, 3H, Ar-H), 3.82 (s, 2H, NH2). MS (ESI) m/z:
126 (M þ 1).
6.1.7. General procedure for the synthesis of compound 8aeh
3-(Aminomethyl)pyridine (0.92 mmol) was added to a solution
of compound 7aeh (0.92 mmol) in dried DMF (15 mL). The reaction
mixture was stirred at room temperature for 24 h, then was
quenched by the addition of H2O (100 mL) and extracted with
EtOAc (100 mL). The organic layer was separated, dried over
anhydrous Na2SO4, concentrated under reduced pressure. The
residue was purified by silica gel column chromatography (CH2Cl2/
MeOH/Et3N ¼ 50:1:0.2, v/v) to give compounds 8aeh
6.1.2. 2-(Chloromethyl)benzoxazol-4-ol (3)
Ethyl 2-chloroacetimidate hydrochloride (31.6 g, 0.26 mol) was
added to a solution of compound 2 (25.0 g, 0.2 mol) in CH2Cl2 (500
mL) at 0 ꢀC and the mixture was stirred for 2 h. Then, the reaction
mixture was heated to room temperature and stirred for 24 h. After
the reaction was completed, the resulting solution was diluted with
CH2Cl2 (500 mL) and washed with water (500 mL ꢃ 3). The organic
layer was separated, dried over anhydrous Na2SO4 and concen-
trated under reduced pressure. The residue was purified by silica
gel column chromatography (hexane/EtOAc ¼ 10:1, v/v) to give 3 as
white crystalline solid (16.0 g, 43.6% yield). mp: 148e149 ꢀC. 1H
6.1.8. 3-{2-[(2-Fluorophenoxy)methyl]benzoxazol-4-yloxy}-
N-(pyridin-3-ylmethyl) propan-1-amine (8a)
White solid (280 mg, 74.7% yield). mp: 47e48 ꢀC. 1H NMR
d
(ppm): 8.62 (s, 1H, pyridinyl-C2H), 8.51 (d, 1H, J ¼ 3.5 Hz, pyr-
idinyl-C6H), 7.86 (d, 1H, J ¼ 7.5 Hz, pyridinyl-C4H), 6.95e7.40 (m,
8H, Ar-H), 5.50 (s, 2H, CH2OPh), 4.31 (t, 2H, 6.0 Hz,
NMR
d
(ppm): 10.42 (s, 1H, OH), 7.23 (t, 1H, J ¼ 8.0 Hz, Ar-C7H), 7.15
(d, 1H, J ¼ 8.0 Hz, Ar-C6H), 6.77 (d, 1H, J ¼ 8.0 Hz, Ar-C5H), 5.03
J
¼
(s, 2H, CH2Cl). MS (ESI) m/z: 184 (M þ 1).
OCH2CH2CH2NH), 3.98 (s, 2H, NHCH2pyridinyl), 2.92 (t, 2H, J ¼ 6.5
Hz, OCH2CH2CH2NH), 2.04e2.10 (m, 2H, OCH2CH2CH2NH). 13C NMR
6.1.3. Tert-butyl 2-(chloromethyl)benzoxazol-4-yl carbonate (4)
Boc2O (2.5 g, 11.48 mmol) and dimethylaminopyridine (DMAP,
2.5 mg, 0.02 mmol) was added to a solution of compound 3 (1.835 g,
10 mmol) in CH2Cl2 (50 mL). The reaction mixture was stirred at
room temperature for 30 min. The organic layer was washed with
1N HCl (80 mL), H2O (80 mL), saturated NaHCO3 (80 mL) and
saturated brine (80 mL), then dried over anhydrous Na2SO4 and
concentrated under reduced pressure to give crude product as
yellow liquid which was purified by silica gel column chromato-
graphy (hexane/EtOAc ¼ 20:1, v/v) to give 4 as colorless oil (2.6 g,
d (ppm): 159.53 (C), 153.96 (C), 152.57 (C), 150.96 (C), 149.70 (CH),
148.50 (CH), 145.84 (C), 136.01 (CH), 135.01 (C), 130.38 (C), 126.39
(CH), 124.40 (CH), 123.39 (CH), 122.78 (CH), 116.46 (CH), 107.66
(CH), 103.74 (CH), 67.66 (CH2), 64.30 (CH2), 51.10 (CH2), 46.25 (CH2),
29.27 (CH2). HRMS (m/z): calcd. for C23H22FN3O3: 407.1645; found:
407.1634. Anal. calcd. for C23H22FN3O3: C, 67.80; H, 5.44; N, 10.31.
Found: C, 67.66; H, 5.45; N, 10.33.
6.1.9. 3-{2-[(4-Fluorophenoxy)methyl]benzoxazol-4-yloxy}-
N-(pyridin-3-ylmethyl) propan-1-amine (8b)
91.7% yield). 1H NMR
d
(ppm): 7.72 (d, 1H, J ¼ 8.0 Hz, Ar-C7H), 7.49
Pale yellow solid (264 mg, 70.4% yield). mp: 48e49 ꢀC. 1H NMR
(t, 1H, J ¼ 8.0 Hz, Ar-C6H), 7.29 (d, 1H, J ¼ 7.5 Hz, Ar-C5H), 5.09
(s, 2H, CH2Cl), 1.51 (s, 9H, tert-butyl). MS (ESI) m/z: 284 (M þ 1).
d
(ppm): 8.53 (s,1H, pyridinyl-C2H), 8.42 (d,1H, J ¼ 5.0 Hz, pyridinyl-
C6H), 7.74 (d,1H, J ¼ 7.5 Hz, pyridinyl-C4H), 6.94e7.36 (m, 8H, Ar-H),
5.40 (s, 2H, CH2OPh), 4.29 (t, 2H, J ¼ 6.0 Hz, OCH2CH2CH2NH), 3.73 (s,
2H, NHCH2Pyridinyl), 2.69 (t, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH), 1.95
6.1.4. General procedure for the synthesis of compounds 5aeh
Substituted phenol (1.03 mmol) was added to a suspension of
NaH (60%, 400 mg, 10 mmol) in dried DMF (20 mL) and was stirred
for 30 min. Compound 4 (2.6 g, 9.2 mmol) was added to the reaction
mixture and stirred for 3 h. The resulting mixture was diluted with
EtOAc (100 mL) and washed with H2O (100 mL ꢃ 2). The organic
layer was separated, dried over anhydrous Na2SO4 and concen-
trated under reduced pressure. The residue was purified by silica
gel column chromatography (hexane/EtOAc ¼ 20:1, v/v) to give
compounds 5aeh.
(p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH). 13C NMR
d (ppm): 159.76 (C),
158.82 (C),154.01 (C),152.51 (C),151.00 (C),149.62 (CH),148.37 (CH),
135.87 (CH), 135.41 (C), 130.37 (C), 126.32 (CH), 123.35 (CH), 116.14
(CH), 107.62 (CH), 103.60 (CH), 67.66 (CH2), 63.51 (CH2), 51.18 (CH2),
46.27 (CH2), 29.43 (CH2). HRMS (m/z): calcd. for C23H22FN3O3:
407.1645; found: 407.1638. Anal. calcd. for C23H22FN3O3: C, 67.80; H,
5.44; N, 10.31. Found: C, 67.87; H, 5.46; N, 10.27.
6.1.10. 3-[2-(Phenoxymethyl)benzoxazol-4-yloxy]-N-(pyridin-
3-ylmethyl)propan-1-amine (8c)
6.1.5. General procedure for the synthesis of compounds 6aeh
White solid (245 mg, 68.5% yield). mp: 48e49 ꢀC. 1H NMR
Trifluoroacetic acid (15 mL) was added to
a
solution of
d
(ppm): 8.54 (d,1H, J ¼ 1.5 Hz, pyridinyl-C2H), 8.44 (dd,1H, J1 ¼5.0
compound 5aeh (5.85 mmol) in CH2Cl2 (15 mL). The reaction
mixture was stirred at room temperature for 20 min. Trifluoroacetic
acid was evaporated under reduced pressure. The residue was
diluted with CH2Cl2 (100 mL), washed with H2O (100 mL), saturated
NaHCO3 (100 mL), and saturated brine (100 mL). Then the organic
layer was separated, dried over anhydrous Na2SO4, concentrated
under reduced pressure to give crude product which was purified
by silica gel column chromatography (hexane/EtOAc ¼ 4:1, v/v) to
give compounds 6aeh.
Hz, J2 ¼1.5 Hz, pyridinyl-C6H), 7.76 (d,1H, J ¼ 7.5 Hz, pyridinyl-C4H),
6.94e7.34 (m, 9H, Ar-H), 5.42 (s, 2H, CH2OPh), 4.29 (t, 2H, J ¼ 6.5 Hz,
OCH2CH2CH2NH), 3.78 (s, 2H, NHCH2Pyridinyl), 2.73 (t, 2H, J ¼ 7.0
Hz, OCH2CH2CH2NH), 1.97 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH). 13
C
NMR
d (ppm): 160.04 (C), 157.93 (C), 152.54 (C), 150.94 (C), 149.70
(CH), 148.48 (CH), 135.98 (CH), 135.01 (C), 130.45 (C), 129.59 (CH),
126.23 (CH), 123.37 (CH), 121.86 (CH), 114.89 (CH), 107.76 (CH),
103.69 (CH), 67.70 (CH2), 62.78 (CH2), 51.08 (CH2), 46.24 (CH2), 29.30
(CH2). HRMS (m/z): calcd. for C23H23N3O3: 389.1739; found:
389.1750. Anal. calcd. for C23H23N3O3: C, 70.93; H, 5.95; N, 10.79.
Found: C, 71.07; H, 5.92; N, 10.76.
6.1.6. General procedure for the synthesis of compounds 7aeh
Compounds 6aeh (1.16 mmol), anhydrous K2CO3 (690 mg, 4
mmol) and 1,3-dichloropropane were suspended in dried DMF (15
mL). The reaction mixture was stirred at room temperature for 5 h,
then was diluted with EtOAc (50 mL) and washed with H2O (50 mL).
The organic layer was separated, dried over anhydrous Na2SO4 and
6.1.11. 3-{2-[(2,4-Difluorophenoxy)methyl]benzoxazol-4-yloxy}-
N-(pyridin-3-yl methyl)propan-1-amine (8d)
White solid (302 mg, 77.2% yield). mp: 48e49 ꢀC. 1H NMR
(ppm): 8.52 (s, 1H, pyridinyl-C2H), 8.42 (dd, 1H, J1 ¼ 3.5 Hz,
d

C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
3537
J2 ¼ 1.0 Hz, pyridinyl-C6H), 7.73 (d, 1H, J ¼ 7.5 Hz, pyridinyl-C4H),
6.95e7.39 (m, 7H, Ar-H), 5.48 (s, 2H, CH2OPh), 4.29 (t, 2H, J ¼ 6.5 Hz,
OCH2CH2CH2NH), 3.72 (s, 2H, NHCH2Pyridinyl), 2.68 (t, 2H, J ¼ 6.5
Hz, OCH2CH2CH2NH), 1.94 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH).
HRMS (m/z): calcd. for C23H21F2N3O3: 425.1551; found: 425.1537.
Anal. calcd. for C23H21F2N3O3: C, 64.93; H, 4.98; N, 9.88. Found: C,
64.73; H, 4.99; N, 9.86.
Anal. calcd. for C23H22N4O5: C, 63.59; H, 5.10; N, 12.90. Found: C,
63.46; H, 5.11; N, 12.91.
6.1.16. 2-(Benzyloxy)benzaldehyde (10)
Salicylaldehyde (5.25 mL, 49.1 mmol) and benzyl bromide (6.45
mL, 54.0 mmol) were added to a suspension of K2CO3 (29.9 g, 216
mmol) in MeOH (300 mL) and CHCl3 (600 mL) under N2 atmosphere.
Then, the reaction mixture was refluxed for 24 h and filtrated. The
filtrate was concentrated under reduced pressure. 1N HCl (200 mL)
was added to the residue. Then the mixture was extracted with
CH2Cl2 (300 mL ꢃ 2). The combined organic layer was washed with
saturated brine (300 mL ꢃ 2), dried over anhydrous Na2SO4 and
concentrated under reduced pressure. The residue was recrystal-
lized from absolute EtOH to give 10 as white needles (9.1 g, 87.5%
yield). mp: 49e51 ꢀC. MS (ESI) m/z: 213 (M þ 1).
6.1.12. 3-{2-[(2,6-Difluorophenoxy)methyl]benzoxazol-4-yloxy}-
N-(pyridin-3-yl methyl)propan-1-amine (8e)
Pale yellow solid (221 mg, 56.4% yield). mp: 48e49 ꢀC. 1H NMR
d
(ppm): 8.53 (d,1H, J ¼ 1.5 Hz, pyridinyl-C2H), 8.43 (dd,1H, J1 ¼5.0
Hz, J2 ¼ 1.5 Hz, pyridinyl-C6H), 7.74 (d, 1H, J ¼ 8.0 Hz, pyridinyl-
C4H), 6.94e7.38 (m, 7H, Ar-H), 5.40 (s, 2H, CH2OPh), 4.28 (t, 2H,
J ¼ 6.5 Hz, OCH2CH2CH2NH), 3.73 (s, 2H, NHCH2Pyridinyl), 2.51 (t,
2H, J ¼ 7.0 Hz, OCH2CH2CH2NH), 1.94 (m, 2H, OCH2CH2CH2NH). 13
C
NMR
d
(ppm): 159.21 (C), 156.89 (C), 154.91 (C), 152.54 (C), 150.83
6.1.17. Ethyl 4-(benzyloxy)-1H-indole-2-carboxylate (11)
(C), 149.65 (CH), 148.45 (CH), 136.27 (CH), 133.90 (C), 130.24 (C),
126.35 (CH), 123.90 (CH), 123.34 (CH), 112.16 (CH), 107.66 (CH),
103.58 (CH), 67.52 (CH2), 50.53 (CH2), 45.83 (CH2), 28.66 (CH2).
HRMS (m/z): calcd. for C23H21F2N3O3: 425.1551; found: 425.1534.
Anal. calcd. for C23H21F2N3O3: C, 64.93; H, 4.98; N, 9.88. Found: C,
64.80; H, 4.97; N, 9.90.
Compound 10 (15.8 g, 74 mmol) and a solution of a-ethyl 2-
azidoacetate (50 mL) in EtOH (20 mL) was added to a suspension of
Na (7 g) in absolute EtOH (200 mL) at ꢁ10 ꢀC. After the addition
over a period of 2 h, the mixture was stirred for additional 8 h,
cooled to room temperature, and then quenched by the addition of
H2O (1500 mL). The precipitate was filtrated, washed with H2O
(500 mL) and dried under vacuum. The crude product was dis-
solved in toluene (250 mL). The solution was heated to reflux at 125
ꢀC for 3 h, then cooled to room temperature and filtrated. The
filtrate was concentrated under reduced pressure. The residue was
recrystallized from CHCl3/hexane to give 11 as white needles (6.7 g,
6.1.13. N-(Pyridin-3-ylmethyl)-3-{2-[(2,3,4-trifluorophenoxy)-
methyl]benzoxazol-4-yloxy}propan-1-amine (8f)
White solid (310 mg, 76.1% yield). mp: 49e51 ꢀC. 1H NMR
d
(ppm): 8.52 (s, 1H, pyridinyl-C2H), 8.41 (d, 1H, J ¼ 3.5 Hz,
pyridinyl-C6H), 7.73 (d,1H, J ¼ 7.5 Hz, pyridinyl-C4H), 6.95e7.37 (m,
6H, Ar-H), 5.55 (s, 2H, CH2OPh), 4.29 (t, 2H, 6.0 Hz,
30.6% yield). mp: 169e172 ꢀC. 1H NMR
d (ppm): 11.90 (s, 1H, indole-
J
¼
NH), 6.63e7.52 (m, 9H, Ar-H), 5.23 (s, 2H, OCH2Ph), 4.32 (q, 2H,
J ¼ 7.0 Hz, COOCH2CH3), 1.33 (t, 3H, J ¼ 7.0 Hz, COOCH2CH3). MS
(ESI) m/z: 296 (M þ 1).
OCH2CH2CH2NH), 3.73 (s, 2H, NHCH2Pyridinyl), 2.68 (t, 2H, J ¼ 6.5
Hz, OCH2CH2CH2NH), 1.94 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH). 13
C
NMR d (ppm): 158.84 (C), 152.55 (C), 151.01 (C), 149.59 (CH), 148.34
(CH), 147.80 (C), 145.95 (C), 143.60 (C), 142.01 (C), 135.82 (CH),
135.55 (C), 130.28 (C), 126.60 (CH), 123.33 (CH), 110.51 (CH), 110.18
(CH), 107.62 (CH), 103.61 (CH), 67.68 (CH2), 64.98 (CH2), 51.24 (CH2),
46.30 (CH2), 29.47 (CH2). HRMS (m/z): calcd. for C23H20F3N3O3:
443.1457; found: 443.1440. Anal. calcd. for C23H20F3N3O3: C, 62.30;
H, 4.55; N, 9.48. Found: C, 62.42; H, 4.53; N, 9.45.
6.1.18. Ethyl 4-hydroxy-1H-indole-2-carboxylate (12)
Compound 11 (3.0 g, 10.17 mol) and 10% PdeC (300 mg) were
suspended in EtOAc (200 mL) and EtOH (300 mL) under H2 atmo-
sphere (4 atm) and stirred at 50 ꢀC for 6 h. The reaction mixture was
filtered off using celite. The filtrate was concentrated under reduced
pressure to give crude solid. The crude product was recrystallized
from absolute EtOH (10 mL) to give 12 as grey solid (2.0 g, 96% yield).
6.1.14. N-(Pyridin-3-ylmethyl)-3-{2-[(2,4,6-trifluorophenoxy)-
methyl]benzoxazol-4-yloxy}propan-1-amine (8g)
mp: 160e162 ꢀC.1H NMR
d(ppm):11.70(s,1H, indole-NH), 9.67 (s,1H,
OH), 6.38e7.20(m, 4H, Ar-H), 4.32(q, 2H, J¼ 7.0 Hz, COOCH2CH3),1.33
Pale yellow solid (256 mg, 62.8% yield). mp: 48e49 ꢀC. 1H NMR
(t, 3H, J ¼ 7.0 Hz, COOCH2CH3). MS (ESI) m/z: 206 (M þ 1).
d
(ppm): 8.51 (d,1H, J ¼ 1.5 Hz, pyridinyl-C2H), 8.42 (dd,1H, J1 ¼ 5.0
Hz, J2 ¼ 1.5 Hz, pyridinyl-C6H), 7.73 (d, 1H, J ¼ 8.0 Hz, pyridinyl-
C4H), 6.94e7.38 (m, 6H, Ar-H), 5.35 (s, 2H, CH2OPh), 4.28 (t, 2H,
J ¼ 6.5 Hz, OCH2CH2CH2NH), 3.72 (s, 2H, NHCH2Pyridinyl), 2.66 (t,
2H, J ¼ 6.5 Hz, OCH2CH2CH2NH), 1.93 (p, 2H, J ¼ 6.5 Hz,
6.1.19. Ethyl 4-(3-bromopropoxy)-1H-indole-2-carboxylate (13)
Compound 12 (2.05 g, 10 mmol), anhydrous K2CO3 (6.9 g, 50
mmol) and 1,3-dibromopropane (5 mL, 50 mmol) were suspended
in DMF (25 mL). The reaction mixture was stirred at room
temperature for 3 h, then was diluted with EtOAc (300 mL) and
washed with H2O (300 mL ꢃ 2). The combined organic layer was
dried over anhydrous Na2SO4, and concentrated under reduced
pressure. The residue was purified by silica gel column chroma-
tography (hexane/EtOAc ¼ 50:1, v/v) to give 13 as white solid (1.5 g,
OCH2CH2CH2NH). 13C NMR
d (ppm): 158.82 (C), 156.79 (C), 154.85
(C), 152.51 (C), 150.94 (C), 149.41 (CH), 148.13 (CH), 135.70 (CH),
135.17 (C), 131.32 (C), 130.20 (C), 126.35 (CH), 123.14 (CH), 112.26
(CH), 107.57 (CH), 100.68 (CH), 67.65 (CH2), 50.89 (CH2), 45.99
(CH2), 29.19 (CH2). HRMS (m/z): calcd. for C23H20F3N3O3: 443.1457;
found: 443.1445. Anal. calcd. for C23H20F3N3O3: C, 62.30; H, 4.55; N,
9.48. Found: C, 62.23; H, 4.56; N, 9.49.
42.8% yield). 1H NMR
d (ppm): 11.90 (s, 1H, indole-NH), 6.55e7.17
(m, 4H, Ar-H), 4.33 (q, 2H, J ¼ 7.0 Hz, COOCH2CH3), 4.20 (t, 2H,
J ¼ 6.0 Hz, OCH2CH2CH2Br), 3.76 (t, 2H, J ¼ 6.5 Hz, OCH2CH2CH2Br),
2.33 (p, 2H, J ¼ 6.0 Hz, OCH2CH2CH2Br), 1.34 (t, 3H, J ¼ 7.0 Hz,
COOCH2CH3). MS (ESI) m/z: 327 (M þ 1).
6.1.15. 3-{2-[(3-Nitrophenoxy)methyl]benzoxazol-4-yloxy}-
N-(pyridin-3-ylmethyl) propan-1-amine (8h)
Pale yellow solid (322 mg, 80.7% yield). mp: 48e49 ꢀC. 1H NMR
d
(ppm): 8.53 (s, 1H, pyridinyl-C2H), 8.42 (d, 1H, J1 ¼ 3.5 Hz, J2 ¼ 1.5
6.1.20. Ethyl 4-[3-(pyridin-3-ylmethylamino)propoxy]-1H-indole-
2-carboxylate (14)
3-(Aminomethyl)pyridine (3 mL, 30 mmol) was added to
a solution of compound 13 (1.61 g, 4.94 mmol) in absolute EtOH (30
mL). The reaction mixture was stirred at 70 ꢀC for 24 h, then was
cooled to room temperature and concentrated under reduced
Hz, pyridinyl-C6H), 7.94 (d, 1H, J ¼ 2.0 Hz, pyridinyl-C4H),
6.95e7.88 (m, 8H, Ar-H), 5.61 (s, 2H, CH2OPh), 4.30 (t, 2H, J ¼ 6.5 Hz,
OCH2CH2CH2NH), 3.73 (s, 2H, NHCH2Pyridinyl), 2.69 (t, 2H, J ¼ 7.0
Hz, OCH2CH2CH2NH), 1.95 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH).
HRMS (m/z): calcd. for C23H22N4O5: 434.1590; found: 434.1603.

3538
C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
pressure. The residue was diluted with EtOAc (50 mL) and H2O (50
mL). The organic layer was separated, washed with saturated NH4Cl
(100 mL), dried over anhydrous Na2SO4 and concentrated under
reduced pressure to afford yellow oil, which was purified by silica
gel column chromatography (CH2Cl2/MeOH ¼ 50:1 / 20:1, v/v) to
NHCH2Pyridinyl), 2.70 (t, 2H, J ¼ 7.0 Hz, OCH2CH2CH2NH),1.93 (p, 2H,
J ¼ 6.5 Hz, OCH2CH2CH2NH). HRMS (m/z): calcd. for C24H24FN3O2:
405.1853; found: 405.1840. Anal. calcd. for C24H24FN3O2: C, 71.09; H,
5.97; N, 10.36. Found: C, 70.88; H, 5.98; N, 10.38.
give 14 as grey solid (1.3 g, 74.6% yield). 1H NMR
d
(ppm): 11.88 (s,
6.1.25. General procedure for the synthesis of compounds 17aeb
Substituted thiol (0.2 mmol) was added to a stirring solution of
compound 15 (0.2 mmol) and trifluoroacetic acid (0.2 mL) in dried
CH2Cl2 (5 mL). The reaction mixture was stirred at room temper-
ature for 2 h, then was diluted with CH2Cl2 (30 mL), washed with
0.1 mol/L NaOH (30 mL), H2O (30 mL) and saturated brine (30 mL).
The organic layer was separated, dried over anhydrous Na2SO4 and
concentrated under reduced pressure. The residue was purified by
silica gel column chromatography (CH2Cl2/MeOH ¼ 50:1, v/v) to
give compounds 17aeb.
1H, indole-NH), 8.56 (s, 1H, pyridinyl-C2H), 8.45 (m, 1H, pyridinyl-
C6H), 7.77 (d,1H, J ¼ 7.5 Hz, pyridinyl-C4H), 7.33 (dd,1H, J1 ¼7.5 Hz,
J2 ¼ 2.5 Hz, pyridinyl-C5H), 6.52e7.17 (m, 4H, Ar-H), 4.33 (q, 2H,
J ¼ 7.0 Hz, COOCH2CH3), 4.16 (t, 2H, J ¼ 6 Hz, OCH2CH2CH2NH), 3.80
(s, 2H, NHCH2Pyridinyl), 2.78 (t, 2H, J ¼ 7.0 Hz, OCH2CH2CH2NH),
1.99 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH), 1.35 (t, 3H, J ¼ 7.0 Hz,
COOCH2CH3). MS (ESI) m/z: 354 (M þ 1).
6.1.21. {4-[3-(Pyridin-3-ylmethylamino)propoxy]-1H-indol-2-yl}-
methanol (15)
LiAlH4 (1.5 g, 39.5 mmol) was added in small portions to
a solution of compound 14 (2.6 g, 7.37 mmol) in THF (30 mL) at 0 ꢀC.
The reaction mixture was stirred for 1 h. Then H2O (1 mL) was
added to get rid of excess LiAlH4. The mixture was stirred for 1 h,
dried with anhydrous Na2SO4 and concentrated under reduced
pressure. The residue was purified by silica gel column chroma-
tography (CH2Cl2/MeOH ¼ 50:1, v/v) to give 15 as yellow oil (1.4 g,
6.1.26. [3-(2-(Phenylthiomethyl)-1H-indol-4-yloxy)]-N-(pyridine-
3-ylmethyl)propan-1-amine (17a)
Colorless oil (22 mg, 27.5%). 1H NMR
d (ppm): 11.34 (s, 1H,
indole-NH), 8.52 (s, 1H, pyridinyl-C2H), 8.42 (d, 1H, J ¼ 3.5 Hz,
pyridinyl-C6H), 7.74 (d,1H, J ¼ 7.5 Hz, pyridinyl-C4H), 6.50e7.39 (m,
10H, Ar-H), 4.68 (d, 1H, J ¼ 13.5 Hz, CH2S), 4.45 (d, 1H, J ¼ 13.5 Hz,
CH2S), 4.12e4.15 (m, 2H, OCH2CH2CH2NH), 3.73 (s, 2H,
NHCH2Pyridinyl), 2.69e2.73 (m, 2H, OCH2CH2CH2NH), 1.93 (t, 2H,
J ¼ 6.5 Hz, OCH2CH2CH2NH). HRMS (m/z): calcd. for C24H25N3OS:
403.1718; found: 403.1705. Anal. calcd. for C24H25N3OS: C, 71.43; H,
6.24; N, 10.41. Found: C, 71.57; H, 6.22; N, 10.39.
87.3%). 1H NMR
d (ppm): 10.95 (s, 1H, indole-NH), 8.53 (s, 1H, pyr-
idinyl-C2H), 8.43 (d, 1H, J ¼ 4.5 Hz, pyridinyl-C6H), 7.74 (d, 1H,
J ¼ 8.0 Hz, pyridinyl-C4H), 7.31 (dd, 1H, J1 ¼ 7.5 Hz, J2 ¼ 5.0 Hz,
pyridinyl-C5H), 6.22e6.91 (m, 4H, Ar-H), 5.16 (s, 1H, OH), 4.56 (s,
2H, CH2OH), 4.11 (t, 2H, J ¼ 6.0 Hz, OCH2CH2CH2NH), 3.73 (s, 2H,
NHCH2Pyridinyl), 2.69 (t, 2H, J ¼ 7.0 Hz, OCH2CH2CH2NH), 1.92 (m,
2H, OCH2CH2CH2NH). MS (ESI) m/z: 312 (M þ 1).
6.1.27. 3-{2-[(2,6-Dichlorophenylthio)methyl]-1H-indol-4-yloxy}-
N-(pyridine-3-yl methyl)propan-1-amine (17b)
Colorless oil (18 mg, 19% yield). 1H NMR
d (ppm): 11.22 (s, 1H,
6.1.22. General procedure for the synthesis of 3-{2-[(substituted
phenoxy)methyl]-1H-indol-4-yloxy}-N-(pyridin-3-yl methyl)-
propan-1-amine (16aeb)
indole-NH), 8.52 (s, 1H, pyridinyl-C2H), 8.42 (d, 1H, J ¼ 4.5 Hz,
pyridinyl-C6H), 7.73 (d, 1H, J ¼ 7.5 Hz, pyridinyl-C4H), 7.54 (d, 1H,
J ¼ 8.0 Hz, pyridinyl-C5H), 6.41e7.40 (m, 7H, Ar-H), 4.54 (d, 1H,
J ¼ 13.5 Hz, CH2S), 4.31 (d, 1H, J ¼ 13.5 Hz, CH2S), 4.10e4.14 (m, 2H,
OCH2CH2CH2NH), 3.72 (s, 2H, NHCH2Pyridinyl), 2.69 (d, 2H, J ¼ 2.5
Hz, OCH2CH2CH2NH), 1.93 (p, 2H, J ¼ 6.0 Hz, OCH2CH2CH2NH).
HRMS (m/z): calcd. for C24H23Cl2N3OS: 471.0939; found: 471.0957.
Anal. calcd. for C24H23Cl2N3OS: C, 61.02; H, 4.91; N, 8.89. Found: C,
60.89; H, 4.92; N, 8.90.
1,1-(Azodicarbonyl)dipiperidine (0.9 mmol) was added to a solu-
tion of compound 15 (0.6 mmol), tri-tert-butylphosphine (TBP, 0.9
mmol) and substituted phenol (0.6 mmol) in dried CH2Cl2 (2 mL)
which was cooled to ꢁ20 ꢀC under N2 atmosphere and stirred for
15min. The reaction mixture was stirred at room temperature for 24
h, then was poured into saturated NaHCO3 (40 mL) and extracted
with EtoAc (40 mL). The combined organic layer was washed with
saturated brine (40 mL), dried over anhydrous Na2SO4 and concen-
trated under reduced pressure. The residue was purified by silica gel
column chromatography (CH2Cl2/MeOH ¼ 50:1 / 20:1, v/v) to give
compounds 16aeb.
6.1.28. 4-(3-Bromopropoxy)-1H-indole-2-carboxylic acid (18)
LiOH$H2O (560 mg, 13.3 mmol), H2O (35 mL) and MeOH (12
mL) were added to a solution of compound 13 (1.63 g, 5.0 mmol) in
THF (45 mL) at 0 ꢀC. The reaction mixture was stirred at room
temperature for 6 h and was added 1N HCl (11 mL). After
removing the solvent under reduced pressure, the residue was
extracted with EtOAc (120 mL). The EtOAc solution was washed
with saturated brine (120 mL), dried over anhydrous Na2SO4 and
concentrated under reduced pressure to afford crude solid, which
was washed with haxene/EtOAc (4:1, v/v) and dried under vacuum
6.1.23. 3-{2-[(2,4-Difluorophenoxy)methyl]-1H-indol-4-yloxy}-
N-(pyridine-3-ylmethyl) propan-1-amine (16a)
Yellow solid: (7.0 mg, 2.8% yield). 1H NMR
d (ppm): 11.31 (s, 1H,
indole-NH), 8.53 (s, 1H, pyridinyl-C2H), 8.42 (d, 1H, J ¼ 3.5 Hz,
pyridinyl-C6H), 7.74 (d,1H, J ¼ 7.5 Hz, pyridinyl-C4H), 6.47e7.38 (m,
8H, Ar-H), 5.22 (s, 2H, CH2OPh), 4.13 (t, 2H,
J
¼
6.0 Hz,
to give 18 as grey solid (1.32 g, 88.6% yield). 1H NMR
d (ppm): 12.79
OCH2CH2CH2NH), 3.73 (s, 2H, NHCH2Pyridinyl), 2.69 (t, 2H, J ¼ 6.0
Hz, OCH2CH2CH2NH), 1.93 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH).
HRMS (m/z): calcd. for C24H23F2N3O2: 423.1758; found: 423.1774.
Anal. calcd. for C24H23F2N3O2: C, 68.07; H, 5.47; N, 9.92. Found: C,
68.20; H, 5.48; N, 9.89.
(s, 1H, COOH), 11.75 (s, 1H, indole-NH), 6.54e7.14 (m, 4H, Ar-H),
4.20 (t, 2H, J ¼ 6.0 Hz, OCH2CH2CH2Br), 3.75 (t, 2H, J ¼ 6.5 Hz,
OCH2CH2CH2Br), 2.33 (p, 2H, J ¼ 6.0 Hz, OCH2CH2CH2Br). MS (ESI)
m/z: 299 (M þ 1).
6.1.29. General procedure for the synthesis of compounds 19aee
Oxalyl chloride (0.5 mL) and a drop of triethylamine were added
to a stirring solution of 18 (0.67 mmol) in dried CH2Cl2 (5 mL). The
reaction mixture was stirred at room temperature for 12 h, and
then was added substituted aniline (0.67 mol). The mixture was
stirred at room temperature for 3 h and concentrated under
reduced pressure. The residue was purified by silica gel column
chromatography (CH2Cl2) to give compounds 19aee.
6.1.24. 3-{2-[(4-Fluorophenoxy)methyl]-1H-indol-4-yloxy}-
N-(pyridine-3-ylmethyl) propan-1-amine (16b)
Pale yellow solid (8.0 mg, 3.0% yield).1H NMR
d (ppm): 11.29 (s,1H,
indole-NH), 8.53 (s, 1H, pyridinyl-C2H), 8.42 (d, 1H, J ¼ 3.5 Hz, pyr-
idinyl-C6H), 7.74(d,1H, J¼ 7.5Hz, pyridinyl-C4H), 7.31(dd,1H, J1¼8.0
Hz, J2 ¼ 5.0 Hz, pyridinyl-C5H), 6.44e7.15 (m, 8H, Ar-H), 5.15 (s, 2H,
CH2OPh), 4.13 (t, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH), 3.74 (s, 2H,

C. Sheng et al. / European Journal of Medicinal Chemistry 45 (2010) 3531e3540
3539
6.1.30. General procedure for the synthesis of compounds 20aee
3-(Aminomethyl)pyridine (0.28 mol) was added to a solution of
compound 19aee (0.28 mmol) in absolute EtOH (5 mL). The reac-
tion mixture was stirred at 80 ꢀC for 12 h and evaporated under
reduced pressure. The residue was dissolved in EtOAc (50 mL) and
H2O (50 mL). The organic layer was separated, washed with satu-
rated NH4Cl (50 mL), dried over anhydrous Na2SO4 and concen-
trated under reduced pressure. The residue was purified by silica
gel column chromatography (CH2Cl2/MeOH ¼ 20:1, v/v) to give
compounds 20aee.
OCH2CH2CH2NH), 3.76 (s, 2H, NHCH2Pyridinyl), 2.74 (t, 2H, J ¼ 7.0
Hz, OCH2CH2CH2NH), 1.98 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH).
HRMS (m/z): calcd. for C24H23ClN4O2: 434.1510; found: 434.1494.
Anal. calcd. for C24H23ClN4O2: C, 66.28; H, 5.33; N, 12.88. Found: C,
66.01; H, 5.34; N, 12.90.
6.2. Molecular docking
ꢀ
The crystallographic coordinates of CaNMT [25] (0.32 A resolu-
tion, Rcryst ¼ 0.284) were obtained from the Brookheaven Protein
Databank as entries 1IYL. The chemical structures of compounds 8f
and 16a were built by InsightII 2000 software package. Followed by
energy minimization, compounds 8f and 16a were docked into the
active site of CaNMT using the Affinity module within InsightII
2000 software package. The detailed docking protocols are similar
to that in our previous modeling studies on CaNMT [26].
6.1.31. N-(3-Fluorophenyl)-4-[3-(pyridin-3-ylmethylamino)-
propoxy]-1H-indole-2-carboxamide (20a)
Yellow solid (30 mg, 25% yield). 1H NMR
d (ppm): 11.77 (s, 1H,
indole-NH), 10.35 (s, 1H, CONH), 8.55 (s, 1H, pyridinyl-C2H), 8.42 (d,
1H, J ¼ 4.5 Hz, pyridinyl-C6H), 7.81 (d, 1H, J ¼ 7.0 Hz, pyridinyl-
C4H), 6.54e7.75 (m, 9H, Ar-H), 4.18 (t, 2H,
J
¼
6.0 Hz,
OCH2CH2CH2NH), 3.75 (s, 2H, NHCH2Pyridinyl), 2.73 (t, 2H, J ¼ 6.5
Hz, OCH2CH2CH2NH), 1.98 (p, 2H, J ¼ 6.5 Hz, OCH2CH2CH2NH).
HRMS (m/z): calcd. for C24H23FN4O2: 418.1805; found: 418.1817.
Anal. calcd. for C24H23FN4O2: C, 68.88; H, 5.54; N, 13.39. Found: C,
69.01; H, 5.52; N, 13.40.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Grant Nos. 30973640), Shanghai Rising-Star
Program (Grant Nos. 09QA1407000), National Major Special Project
for the Creation of New Drugs (Grant Nos. 2009ZX09301-011) and
Shanghai Leading Academic Discipline Project (Project Nos. B906).
6.1.32. N-(4-Chlorophenyl)-4-[3-(pyridin-3-ylmethylamino)-
propoxy]-1H-indole-2-carboxamide (20b)
Yellow solid (36 mg, 30% yield). 1H NMR
d (ppm): 11.74 (s, 1H,
Appendix. Supplementary data
indole-NH), 10.29 (s, 1H, CONH), 8.54 (s, 1H, pyridinyl-C2H), 8.42 (d,
1H, J ¼ 4.5 Hz, pyridinyl-C6H), 7.86 (d, 1H, J ¼ 9.0 Hz, pyridinyl-
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ejmech.2010.03.007.
C4H), 6.53e7.75 (m, 9H, Ar-H), 4.18 (t, 2H,
J
¼
6.5 Hz,
OCH2CH2CH2NH), 3.75 (s, 2H, NHCH2Pyridinyl), 2.73 (t, 2H, J ¼ 6.5
Hz, OCH2CH2CH2NH), 1.98 (p, 2H, J ¼ 6.0 Hz, OCH2CH2CH2NH).
HRMS (m/z): calcd. for C24H23ClN4O2: 434.1510; found: 434.1499.
Anal. calcd. for C24H23ClN4O2: C, 66.28; H, 5.33; N, 12.88. Found: C,
66.08; H, 5.32; N, 12.91.
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