Design, synthesis and antifungal activities of novel pyrrole alkaloid analogs

Article abstract of DOI:10.1016/j.ejmech.2011.01.031

A series of novel analogs of pyrrole alkaloid were designed and synthesized by a facile method and their structures were characterized by ¹H NMR, ¹³C NMR and high-resolution mass spectrometry (HRMS). The structure of compound 2a was identified by 2D NMR including heteronuclear multiple-quantum coherence (HMQC), heteronuclear multiple-bond correlation (HMBC) and H-H correlation spectrometry (H-H COSY) spectra. Their antifungal activities against five fungi were evaluated, and the results indicated that some of the title compounds showed moderate fungicidal activities in vitro against Alternaria solani, Cercospora arachidicola, Fusarium omysporum, Gibberella zeae and Physalospora piricola at the dosage of 50 μg mL ^-1. Compound 2a and 3a exhibited good activities against P. piricola at low dosage.

Full text of DOI:10.1016/j.ejmech.2011.01.031

European Journal of Medicinal Chemistry 46 (2011) 1463e1472
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis and antifungal activities of novel pyrrole alkaloid analogs
*
Ming-Zhong Wang, Han Xu, Tuan-Wei Liu, Qi Feng, Shu-Jing Yu, Su-Hua Wang, Zheng-Ming Li
State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel analogs of pyrrole alkaloid were designed and synthesized by a facile method and their
structures were characterized by 1H NMR, 13C NMR and high-resolution mass spectrometry (HRMS). The
structure of compound 2a was identified by 2D NMR including heteronuclear multiple-quantum
coherence (HMQC), heteronuclear multiple-bond correlation (HMBC) and HeH correlation spectrometry
(HeH COSY) spectra. Their antifungal activities against five fungi were evaluated, and the results indi-
cated that some of the title compounds showed moderate fungicidal activities in vitro against Alternaria
solani, Cercospora arachidicola, Fusarium omysporum, Gibberella zeae and Physalospora piricola at the
Received 30 September 2010
Received in revised form
13 January 2011
Accepted 17 January 2011
Available online 28 January 2011
Keywords:
Analogues
Pyrrole alkaloid
2D NMR
dosage of 50
m
g mLꢀ1. Compound 2a and 3a exhibited good activities against P. piricola at low dosage.
Ó 2011 Elsevier Masson SAS. All rights reserved.
Antifungal activities
1. Introduction
structureeactivity relationships (SAR) were discussed. In order to
study the SAR, these analogs’ benzene ring was replaced with
In the past century, a lot of bromopyrrole alkaloids had been iso-
lated from marine organism and exhibited good biological activities
[1e3]. For instance, the pyrrolomycin (A, Fig. 1) had distinguished
antibiotic activity [4]. It was commonly assumed that many bromo-
pyrrolealkaloidmetabolites wereservedasa chemical protection role
for the organism including antifeedant, antibacterial and antifungal
agent, etc [5e7]. For example, natural product dispacamide (B, Fig. 1)
and its derivatives isolated from sponge had evident antifeedant and
antibacterial activities [7e9]. Anthranilamide (C, Fig. 1) isolated from
a culture of marine Streptomyces sp. strain B7747 showed remarkable
antimicroalgal activity [10]. Comparing to dispacamide, there were
two similar four-membered carboxamide moieties among them
(eN(CH3)COCH2CH2e and eCONHCH2CH2e). Additionally, it is re-
ported that N-(benzyloxy)benzamide (D, Fig. 1) and its analogs with
the O-benzylhydroxylamine moiety (eCONHOCH2eAr) possessed
antibacterial, herbicidal and enzyme inhibiting activities [11e14]. The
pharmacophore (eCONHOCH2e) was generally considered to be
the bioisosteric analog (eCONHCH2CH2e) for drug’s design [15].
Considering the potential antifungal activity of the bromopyrrole
alkaloid and the activity contribution of the O-benzylhydroxylamine
group to the N-(benzyloxy)benzamide derivatives [11e14], a series
of new dibromopyrrole alkaloid analogs (E, Fig. 1) were desig-
ned, synthesized and tested against fungi in vitro. Their antifungal
activities against five fungi were evaluated and the possible
differentgroups.Basedon theSAR, someanalogs withthepyrrolering
substituted by eCl (m ¼ 2), eBr (m ¼ 3) or unsubstituted by any
halogen atom were also synthesized. And the pyrrole ring of some
derivatives was further methylated. All the new derivatives were
designed to learn whether those might increase or decrease their
biological activities.
2. Chemistry
2.1. Synthesis
In this paper, 1H-pyrrole-2-carboxylic acid 2 was successfully
synthesized through an improved procedure (see experimental
Section 5.2.1 and Scheme 1). Compound 2 was failed to be given
when the mixture was stirred for 10 h at room temperature
according to the literature [16]. 4,5-Dichloro-1H-pyrrole-2-carbox-
ylic acid 5 was also successfully synthesized using a mixture solution
(see experimental Section 5.2.1 and Scheme 1). It is failed to get
compound 5 when the solution was only dichloromethane and
stirred for 6 h at room temperature according to the literature [17].
Compounds 3aer, 2a, 2g, 2r, 4a, 4g, 4r, 5a, 5g, 5r, 2aa, 2ab were all
synthesized by a facile method referencing to the literature (see
experimental Section 5.2.1.4 and 5.2.1.5, Scheme 2 and Table 1) [18].
Especially, Compound 7r was fully synthesized by a novel method
described in the synthesis section. Since the reaction of brominewith
1H-pyrrole-2-carboxylic acid was complicated and the byproduct
was difficult to separate from each other [19e23], it is unfortunately
* Corresponding author. Tel.: þ86 22 23503732; fax: þ86 22 23505948.
E-mail address: nkzml@vip.163.com (Z.-M. Li).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.01.031

1464
M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
Br
NH
NH
CO H
2
Br
Br
2
O
Br
N
H
N
Br
Br
N
N
H
N
H
O
O
CH
O
OH
3
Pyrrolomycin A
Dispacamide B
Anthranilamide C
4
3
Rb
7
H
N
O
Rm
2
9
Ra= H; CH
6
8
N
3
O
10
11
N
5
Ra
Rb= H; CH
3
O
13
Rn
O
Rm= Cl, m = 2; Br, m = 0, 2, 3
Rn= F; Cl; Br; CN; NO etc.
2
12
n = 0, 1, 2
Compound D
Compound E
Target compounds in present work
Fig. 1. Chemical structure of compounds AeE.
to obtain the monobromine-1H-pyrrole-2-carboxylic acid and cor-
responding target product.
belonged to C-6, C-8, C-11, C-10 respectively. So dH ¼ 11.58 (s, 1H)
belonged to the PyrroleeNH. The correlations between dH ¼ 7.10 (s,
1H)/C-10 (dC ¼ 148.9), dH ¼ 6.92 (s, 1H), 6.09 (s, 1H)/C-6 (dC ¼ 159.7)
indicated dH ¼ 7.10 belonged to H-9 (AreH); dH ¼ 6.92, 6.09
belonged to PyrroleeH. So dH ¼ 6.71 (s, 1H) belonged to the H-2.
The correlations between dH ¼ 6.95 (d, 1H)/C-7 (dC ¼ 77.1)
explained dH ¼ 6.95 belonged to H-13; so dH ¼ 7.02 (d, 1H) belonged
to H-12. The correlations between dH ¼ 4.79 (H-14)/dC ¼ 79.2 (s),
78.2 (d); dH ¼ 3.55 (s, 1H)/C-14 (dC ¼ 55.9) indicated dH ¼ 3.55 and
dC ¼ 79.2 belonged to H-16 and C-15 respectively. All the data
indicated the structure of 2a should be as follow (Fig. 2).
In the HeH COSY spectra, the correlations between dH ¼ 6.09 (s,
1H)/dH ¼ 6.92 (s, 1H) and dH ¼ 6.09 (s, 1H)/dH ¼ 6.71 (H-2) indicated
dH ¼ 6.09, 6.92 belonged to H-3 and H-4 respectively. The corre-
lations between dH ¼ 11.58 (PyrroleeNH)/dH ¼ 6.09 (H-3), 6.71 (H-
2), 6.92 (H-4), the correlations between dH ¼ 7.02 (H-12)/dH ¼ 6.95
(H-13) and the correlations between dH ¼ 4.79 (H-14)/dH ¼ 3.55 (H-
16) further verified the positions of all the protons. Additionally, the
structures of compounds 2aa and 2ab were also testified by 1D
NMR and 2D NMR spectra.
2.2. Structure elucidation
The structure of the potential compound 2a was elucidated by 1D
NMR and 2D NMR as follows: The molecular formula of 2a was
revealed as C16H16N2O4 by HRMS data [M þ Na]þ (found 323.1004,
calcd 323.1002). The 1H and 13C NMR (2a) spectra showed the signals
of six quaternary, seven CH, two CH2 and one CH3 carbon atoms.
Considered the reagents, in the HMQC spectra showed dH ¼ 11.58 (s,
1H) and dH ¼ 11.24 (s, 1H) belonged to the PyrroleeNH or eCONHe;
dH ¼ 7.02 (d, 1H) and dH ¼ 6.95 (d, 1H) belonged to the AreH, which
was confirmed by their J value (J ¼ 8.0 Hz). dH ¼ 7.10 (s, 1H), 6.92 (s,
1H), 6.71 (s,1H) and 6.09 (s,1H) belonged to the AreH or PyrroleeH.
Based on the HMBC and 13C Dept spectra, the correlations
between dH ¼ 11.24 (s, 1H)/dC ¼ 159.7 (s), dH ¼ 4.83 (s, 2H)/
dC ¼ 129.6 (s), 4.79 (s, 2H)/dC ¼ 146.4 (s) and dH ¼ 3.78 (s, 3H)/
dC ¼ 148.9 (s) indicated dH ¼ 11.24, 4.83, 4.79, 3.78 belonged to
eCONHe, H-7, H-14, H-17 and dC ¼ 159.7, 129.6, 146.4, 148.9
Ag2O/NaOH (aq)
CO2H
POCl3/DMF
ClCH2CH2Cl
CHO
refluxed
N
H
N
H
N
H
1
2
Br
Br
CO2H
N
H
Br2 (2eq)/HOAc
Br2 (3eq)/HOAc
Cl
Cl
SO2Cl2
CH2Cl2, acetone
2
Br2 (1eq)
HOAc
3
CO2H
N
H
Br
Br
Br
5
CO2H
N
H
4
Scheme 1. Synthetic routes to compounds 1e5.

M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
1465
O
O
O
6a-r
NH OH HCl
pyridine
N H H O
2 4 2
ethanol
2
NH OCH R
2
2
N OCH R
O
NOH
2
DMF/NaOH
O
7a-r
O
O
8a-r
Br
Br
Oxalyl Chloride
CH Cl , DMF
8a-r
H
OH
OH
N
Br
Br
O
R
R
N
H
pyridine
N
H
2
2
O
O
O
3a-r
3
H
Oxalyl Chloride
CH Cl , DMF
N
8a, 8g, 8r
O
N
H
N
H
pyridine
2
2
O
2
2a, 2g, 2r
Br
Br
Br
Br
Br
Br
Oxalyl Chloride
CH Cl , DMF
H
8a, 8g, 8r
N
OH
OH
O
O
R
R
N
H
pyridine
N
2
2
H
O
O
4a, 4g, 4r
4
Cl
Cl
Cl
Cl
H
N
Oxalyl Chloride
CH Cl , DMF
8a, 8g, 8r
N
pyridine
N
H
2
2
H
O
O
5a, 5g, 5r
5
CH
N
3
O
O
O
N
H
H
O
O
N
O
K CO /CH I
2
3
3
O
N
H
2aa
O
DMF
O
2a
CH
3
N
O
O
O
N
CH
3
2ab
Scheme 2. Synthetic routes to compounds 7ae2ab.
3. Biological results and discussion
A. solani except the compounds 3a, 3b, 3d-3g and 3i. Comparing the
biological activities with the rest of the compounds’, the inhibition
activities of 3a, 3b, 3deg and 3i were all over 60.0%. In comparison
with 3d, the results indicated that H-10 and H-11 substituted
by eOCH3 (3b) or H-13 substituted by eF (3e) in the aroma ring
would improve its fungicidal activity.
3.1. Fungicidal activities
Table 2 showed the fungicidal activities against Alternaria solani,
Cercospora arachidicola, Fusarium omysporum, Gibberella zeae,
Physalospora piricola of the compounds 3aer, 2a, 2g, 2r, 4a, 4g, 4r,
5a, 5g, 5r, 2aa, 2ab, anthranilamide and the commercial fungicide
3.1.2. Fungicidal activity against C. arachidicola
fenpiclonil at the dosage of 50
m
g mLꢀ1. Table 3 showed the EC50 of
The biological activity rules of 3ae2ab against C. arachidicola were
generally the same as the test against A. solani showed. To be pointed
out, the inhibition activities of 3aeg and 3i were all over 50.0%.
Comparing with 3d and anthranilamide, the results indicated that
H-10andH-11substitutedbyeOCH2O-(3c)orH-12substitutedbyeCl
(3i) in the aroma ring would evidently increase its fungicidal activity.
the high fungicidal activity compounds 2a, 3a, and fenpiclonil.
3.1.1. Fungicidal activity against A. solani
The screening data of Table 2 indicated that at the dosage of
50
m
g mLꢀ1, most compounds exhibited low activities against

1466
M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
Table 1
The R group in compounds of 6 (BreCH2R or CleCH2R)-5r.
Compd.
R
Compd.
R
Compd.
R
O
O
Br
Cl
Br
6a
6g
6m
F
Br
O
O
Cl
Cl
Cl
Br
Br
6b
6c
6h
6i
6n
6o
Cl
NC
Cl
O
O
Cl
CN
Cl
Cl
Cl
Br
Br
6d
6e
6j
6p
6q
CN
N
Cl
Cl
Br
Cl
6k
NO2
F
Cl
Br
Cl
Cl
6f
6l
6r
O
O
F
Cl
O
3.1.3. Fungicidal activity against F. omysporum
The screening data of Table 2 indicated that at the dosage of
g mLꢀ1, most compounds exhibited low activities against
F. omysporum except the compounds 3a, 3b, 3deg and 3i. The
fungicidal activities of 3a, 3b, 3eeg and 3i were all over 40.0%.
Comparing with 3d, the test indicated that H-10 substituted
by eOCH3 and H-11 substituted by propargyl (3a) or H-11
substituted by eF (3g), H-12 substituted by eCl (3i) in the aroma
ring would enhance fungicidal activity.
100% respectively. Comparing with 3d, the antifungal activities of
compounds 3a, 3b and 3g further testified their rules exhibited in
other fungi. To be pointed out, the activity of compound 3p showed
that H-11 in the aroma ring was substituted by eCN would enhance
its activity. The EC50 value of 2a and 3a against P. piricola was
50
m
4.50 m m
g mLꢀ1 and 9.78 g mLꢀ1 respectively (Table 3), which implied
that the pyrrole ring substituted by few halogen atoms and the 6a
moiety were vital for high activity against P. piricola.
Comparing the fungicidal activities of the series of compounds
2, 3, 4, 5 against all the fungi except for 2a against P. piricola, it
would be found that the series of compounds 3 had a little more
activities and spectrums than the 2, 4 and 5 series, which indicated
that the addition of two bromine atoms to the pyrrole ring 2 and 3
position might improve its antifungal activity. Comparing with the
series of 3, the addition of two chlorine atoms (5a, 5g and 5r) or
three bromine atoms (4a, 4g and 4r) to the pyrrole ring did not
increase its fungicidal activity. The biological activities of 2aa and
2ab against all the fungi implied that the methylated pyrrole ring
might decrease their activities.
3.1.4. Fungicidal activity against G. zeae
The screening data of Table 2 indicated that nearly all of the
compounds (3ae2ab) exhibited low activities against G. zeae.
3.1.5. Fungicidal activity against P. piricola
The screening data of Table 2 indicated that the target compounds
exhibited low activities against P. piricola except for 3a, 3b, 3g, 3p and
2a. At the dosage of 50
m
g mLꢀ1, the fungicidal activities of
compounds 3a, 3b, 3g, 3p and 2a were 90.0%, 50.0%, 55.1%, 48.1%,
H
H
3
4
H
9
H
N
6
7
10
8
N
O
O
O
17
H
O
O
N
H
N
H
5
2
13
H
11
O
O
O
14
12
15
H
H
16
Fig. 2. Key HMBC correlations (left) and key HeH correlations (right) of 2a.

M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
1467
Table 2
did not increase its activity. And the methylated pyrrole ring would
weaken its fungicidal activity. The 2a could be considered as
a potential compound for further structural optimization.
Fungicidal activities at dosage of 50 m .
g mLꢀ1
Compd.
A. solani C. arachidicola F. omysporum G. zeae P. piricola
Inhibition (%)
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
2a
2g
2r
4a
4g
4r
5a
5g
5r
2aa
64.9
73.3
31.6
66.7
76.2
61.9
66.5
19.0
66.7
5.3
21.1
40.0
31.6
10.5
21.1
31.6
26.7
52.4
35.3
0
56.3
60.0
75.0
53.3
50.3
54.0
62.5
20.0
80.0
28.6
35.7
43.8
50.0
14.3
35.7
35.0
18.8
26.7
20.0
12.0
13.3
33.3
28.0
26.7
44.0
16.0
40.0
19.2
7.7
47.1
41.2
23.8
40.0
41.2
40.8
58.0
0
47.0
23.8
33.3
23.5
4.8
14.0
18.0
19.0
17.6
6.7
16.7
0
0
22.2
8.3
27.8
0
22.2
8.3
31.6
31.6
27.8
18.0
8.7
4.6
14.7
9.1
18.2
4.5
21.7
13.6
17.4
0
11.8
17.4
2.9
14.7
8.8
20.6
13.0
0
9.1
7.0
8.5
9.1
15.5
13.6
21.1
19.5
21.1
0
20.0
38.0
100
90.0
50.0
18.5
40.9
27.3
40.9
55.1
13.4
38.9
37.0
33.3
27.8
33.3
14.8
25.3
48.1
16.7
13.6
100.0
6.2
5. Experimental section
5.1. Materials and methods
1H NMR, 13C NMR, HMQC, HMBC and HeH COSY spectra were
obtained at 300 MHz using a Bruker AV300 spectrometer or at
400 MHz using a Bruker AV400 spectrometer in CDCl3 or DMSO-d6
solution with tetramethylsilane (TMS) as the internal standard.
Chemical shift values (d) were given in ppm. High-resolution mass
spectrometry (HRMS) data were obtained on a Varian QFT-ESI
instrument. The melting points were determined on an X-4
binocular microscope melting point apparatus (Beijing Tech
Instruments Co., Beijing, China) and were uncorrected. Yields were
not optimized. The reagents were all analytically or chemically
pure. All solvents and liquid reagents were dried by standard
methods in advance and distilled before use. Pyrrole and benzyl
halogen (6deq) were purchased from the Alfa Aesar Company
(Tianjin, China). 6aec [24,25], 6r [26] and anthranilamide [10] were
synthesized according to literatures. Fenpiclonil was bought from
labor Dr. Ehrenstorfer-Schäfers (Augsburg, Germany).
0
16.1
25.8
18.5
25.0
6.2
18.5
24.7
5.8
11.8
19.2
5.9
42.3
30.8
42.3
13.3
16.7
42.3
5.2. Synthesis
2ab
6.0
43.2
100
5.2.1. General synthetic
Anthranilamide
Fenpiclonil
52.0
100
5.2.1.1. Synthesis procedures for compounds 1e5. 1H-Pyrrole-2-
carbaldehyde 1 was synthesized referencing to the literatures
[27,28]. 1H-Pyrrole-2-carboxylic acid 2 was synthesized through an
100
The data is the average of three duplicate results.
Table 3
EC50 (
m
g mLꢀ1) values of 2a, 3a and fenpiclonil.
Y ¼ aþbx
2a
EC50
R
3a
Y ¼ aþbx
EC50
20.03
24.39
>50
>50
9.78
R
A. solani
>50
>50
>50
>50
A. solani
Y ¼ 3.311 þ 1.296x
0.99
0.99
C. arachidicola
F. omysporum
G. zeae
C. arachidicola
F. omysporum
G. zeae
Y ¼ 2.735 þ 1.632x
P. piricola
Y ¼ 4.283 þ 1.095x
4.50
0.94
P. piricola
Y ¼ 3.380 þ 1.634x
0.98
Fenpiclonil
Y ¼ a þ bx
EC50
R
A. solani
Y ¼ 5.340 þ 1.322x
Y ¼ 5.477 þ 1.153x
0.55
0.38
>50
1.71
0.80
0.96
0.95
C. arachidicola
F. omysporum
G. zeae
Y ¼ 4.584 þ 1.780x
Y ¼ 5.226 þ 2.352x
0.97
0.99
P. piricola
4. Conclusion
improved procedure referencing to literature [16]: To a suspension
of sliver oxide was added 1 in ethanol. After stirring for 1 h at reflux
(It is failed to get compound 2 when the mixture was stirred for
10 h at room temperature according to the literature [16]), the
precipitate was filtered out and washed with hot water. The
combined filtrate and washings were acidified with concentrated
hydrochloride acid at room temperature and extracted with ethyl
acetate, drying (MgSO4) and removal the ethyl acetate under
vacuum to give the crude 2. 4,5-Dibromo-1H-pyrrole-2-carboxylic
acid 3 and 3,4,5-tribromo-1H-pyrrole-2-carboxylic acid 4 were
synthesized referencing to the literature [7,9]. When the bromine
was 3 equivalents of the 2 in HOAc and the reaction time was
prolonged. Compound 2 could be fully converted to the crude
product 4 which could be also obtained from compound 3 reacting
with the equivalent of bromine in HOAc. The crude 4 was then
recrystallized in the solution of ethanol/water to give the pure
Twenty-nine pyrrole alkaloid analogs were designed and
synthesized witha novel and facile procedure. Theresultsof bioassay
showed that the fungicidal activities of most target compounds
exhibited moderate activities against A. solani, C. arachidicola, F.
omysporum, G. zeae and P. piricola at the dosage of 50 m
g mLꢀ1. The
possibleSARof those targetcompounds wereasfollows:H-10 andH-
11 substituted by eOCH3; or H-10 and H-11 substituted by eOCH3
and propargyl; H-11 substituted by eF or eCN; H-12 substituted
by eCl;H-13 substituted byeF in thearomaring might improve their
fungicidal activities. The addition of bromine atoms to the pyrrole
ring 2 and 3 position might enhance its antifungal activity and
spectrum. The above terms were essential for high fungicidal activity
in this type of pyrrole alkaloid analogs. The addition of chlorine
atoms at 2 and 3 position or three bromine atoms to the pyrrole ring

1468
M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
product. 4,5-Dichloro-1H-pyrrole-2-carboxylic acid 5 was synthe-
sized through an improved procedure referencing to literature [17]:
To pyrrole-2-carboxylic acid 2 in the mixture solution of dichloro-
methane and acetone (v/v ¼ 4:1, It is failed to get compound 5
when the solution was only dichloromethane and stirred for 6 h at
room temperature according to the literature [17]), sulfuryl chlo-
ride was added dropwise in dichloromethane. The reaction
continued for 0.5 h at room temperature; then the reaction mixture
was poured slowly into water, followed by extraction with ethyl
acetate and washed with water, evaporation the solvent to give the
crude product 5 (Scheme 1).
5.2.1.2.3. 2-(Benzo[1,3]dioxol-5-ylmethoxy)-isoindole-1,3-dione
(7c). White solid; yield 83.3%; mp 172e174 ꢁC; 1H NMR (400 MHz,
CDCl3)
d
: 7.80 (dt, J ¼ 8.0, 3.2 Hz, 2H, AreH), 7.73 (dt, J ¼ 8.0, 3.2 Hz,
2H, AreH), 7.06 (s, 1H, AreH), 6.95 (d, J ¼ 8.0 Hz, 1H, AreH), 6.77 (d,
J ¼ 8.0 Hz,1H, AreH), 5.97 (s, 2H, eOCH2Oe), 5.10 (s, 2H, AreCH2Oe).
13C NMR (100 MHz, CDCl3)
d:163.5(2C),148.5,147.8,134.4(2C),128.8
(2C), 127.4, 124.1, 123.5 (2C), 110.3, 108.1, 101.2, 79.7.
5.2.1.2.4. 2-Benzyloxy-isoindole-1,3-dione (7d). White solid; yield
67.5%; mp 141e143 ꢁC; 1H NMR (400 MHz, CDCl3)
d
: 7.79 (dt, J ¼ 8.8,
3.2 Hz, 2H, AreH), 7.71 (dt, J ¼ 8.8, 3.2 Hz, 2H, AreH), 7.51e7.54 (m,
2H, AreH), 7.36e7.37 (m, 3H, AreH), 5.20 (s, 2H, AreCH2Oe). 13C
5.2.1.1.1. 1H-Pyrrole-2-carbaldehyde (1). Light yellow solid;
NMR (100 MHz, CDCl3) d: 163.5 (2C), 134.4 (2C), 133.6, 129.9 (2C),
129.3, 128.8 (2C), 128.5 (2C), 123.5 (2C), 79.8.
yield 58.8%; mp 40e42 ꢁC; 1H NMR (400 MHz, CDCl3)
d: 10.97 (brs,
1H, PyrroleeNH), 9.49 (s, 1H, eCHO), 7.18 (brs, 1H, PyrroleeH), 7.01
5.2.1.2.5. 2-(2-Fluoro-benzyloxy)-isoindole-1,3-dione (7e). White
(brs, 1H, PyrroleeH), 6.33 (brs, 1H, PyrroleeH). 13C NMR (100 MHz,
solid; yield 79.2%; mp 153e155 ꢁC; 1H NMR (400 MHz, CDCl3)
d:
CDCl3)
5.2.1.1.2. 1H-Pyrrole-2-carboxylic acid (2). White solid; yield
67.9%; mp 193e195 ꢁC; 1H NMR (400 MHz, DMSO-d6)
: 12.24 (brs,
d
: 179.6, 132.8, 127.4, 122.3, 111.3.
7.80 (dt, J ¼ 8.4, 3.2 Hz, 2H, AreH), 7.73 (dt, J ¼ 8.4, 3.2 Hz, 2H,
AreH), 7.53e7.57 (m, 1H, AreH), 7.34e7.37 (m, 1H, AreH), 7.14e7.18
(m, 1H, AreH), 7.05e7.09 (m, 1H, AreH), 5.29 (s, 2H, AreCH2Oe).
d
1H, eCOOH), 11.72 (brs, 1H, PyrroleeNH), 6.95 (brs, 1H, PyrroleeH),
13C NMR (100 MHz, CDCl3)
d: 163.3 (2C), 162.8 (AreF), 160.3 (AreF),
6.72 (brs, 1H, PyrroleeH), 6.13 (brs, 1H, PyrroleeH). 13C NMR
134.4 (2C), 132.2, 131.5, 128.8 (2C), 124.3, 123.5 (2C), 121.2, 115.5,
73.0.
(100 MHz, DMSO-d6) d: 161.8, 123.3, 122.8, 114.6, 109.2.
5.2.1.1.3. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (3). Light
5.2.1.2.6. 2-(3-Fluoro-benzyloxy)-isoindole-1,3-dione (7f). White
red solid; yield 67.2%; mp 180e182 ꢁC; 1H NMR (400 MHz, DMSO-
solid; yield 54.8%; mp 129e131 ꢁC; 1H NMR (400 MHz, CDCl3)
d:
d6)
(100 MHz, DMSO-d6)
5.2.1.1.4. 3,4,5-Tribromo-1H-pyrrole-2-carboxylic acid (4). Red
solid; yield 50.1%; mp 202e204 ꢁC; 1H NMR (400 MHz, DMSO-d6)
13.36 (brs, 1H, eCOOH), 13.16 (brs, 1H, PyrroleeNH). 13C NMR
(100 MHz, DMSO-d6) : 159.3, 122.5, 106.6, 104.2, 103.3.
5.2.1.1.5. 4,5-Dichloro-1H-pyrrole-2-carboxylic acid (5). Purple
solid; yield 75.0%; mp 169e171 ꢁC; 1H NMR (400 MHz, DMSO-d6)
d
: 12.96 (brs, 1H, eCOOH), 6.83 (brs, 1H, PyrroleeH). 13C NMR
7.74 (dt, J ¼ 8.4, 3.2 Hz, 2H, AreH), 7.67 (dt, J ¼ 8.4, 3.2 Hz, 2H,
AreH), 7.24e7.28 (m, 1H, AreH), 7.18e7.24 (m, 2H, AreH),
6.98e7.01 (m, 1H, AreH), 5.12 (s, 2H, AreCH2Oe). 13C NMR
d
: 160.2, 124.9, 116.8, 106.6, 98.7.
d:
(100 MHz, CDCl3) d: 163.9 (AreF), 161.4 (AreF), 163.4 (2C), 136.0,
134.5 (2C), 130.1, 128.8 (2C), 125.2, 123.6 (2C), 116.5, 116.2, 78.9.
5.2.1.2.7. 2-(4-Fluoro-benzyloxy)-isoindole-1,3-dione
d
(7g). White solid; yield 43.7%; mp 148e150 ꢁC; 1H NMR (400 MHz,
d:
CDCl3)
2H, AreH), 7.50e7.54 (m, 2H, AreH), 7.04e7.08 (m, 2H, AreH), 5.17
(s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
: 164.6 (AreF),162.1
d
: 7.81 (dt, J ¼ 8.4, 3.2 Hz, 2H, AreH), 7.74 (dt, J ¼ 8.4, 3.2 Hz,
13.02 (brs, 1H, eCOOH), 12.84 (brs, 1H, PyrroleeNH), 6.81 (brs, 1H,
PyrroleeH). 13C NMR (100 MHz, DMSO-d6)
d: 160.3, 121.6, 116.6,
d
113.9, 108.8.
(AreF), 163.4 (2C), 134.5 (2C), 131.9 (2C), 129.6, 128.8 (2C), 123.5
(2C), 115.6 (2C), 79.0.
5.2.1.2. Synthetic procedures for compounds 7aer. Compound 7a
was synthesized referencing to the literatures [18,29]. To be pointed
out, the crude products of 7b, 7i, 7k, 7l, 7nep required to wash with
the solution of ethyl acetate/petroleum ether (v/v ¼ 1:5) again; In
the preparation of 7r, the whole mixture of N-hydroxyphthalimide,
sodium hydroxide and 6r in DMF needed to be stirred at 80 ꢁC for
2 h, cooled, then poured into water, and stirred for 1 h to afford
a mucilaginous solid which was collected by vacuum filtration and
washed with water. The above mucilaginous solid was then dis-
solved in the solution of dichloromethane/water (v/v ¼ 1:1),
leaving the organic layer and removal the solvent under vacuum to
give the crude 7r which was then recrystallized in the solution of
ethyl acetate/petroleum ether (v/v ¼ 1:4). All the substituents at
the benzene ring were listed in Scheme 2 and Table 1.
5.2.1.2.8. 2-(2-Chloro-benzyloxy)-isoindole-1,3-dione (7h). White
solid; yield 29.0%; mp 154e156 ꢁC; 1H NMR (400 MHz, CDCl3)
d:
7.81 (dt, J ¼ 8.4, 3.2 Hz, 2H, AreH), 7.74 (dt, J ¼ 8.4, 3.2 Hz, 2H,
AreH), 7.62e7.64 (m, 1H, AreH), 7.37e7.39 (m, 1H, AreH),
7.29e7.31 (m, 2H, AreH), 5.36 (s, 2H, AreCH2Oe). 13C NMR
(100 MHz, CDCl3) d: 163.3 (2C), 134.7, 134.4 (2C), 131.9, 131.7, 130.5,
129.6, 128.8 (2C), 127.0, 123.5 (2C), 76.4.
5.2.1.2.9. 2-(3-Chloro-benzyloxy)-isoindole-1,3-dione (7i). White
solid; yield 29.2%; mp 134e136 ꢁC; 1H NMR (400 MHz, CDCl3)
d:
7.82 (dt, J ¼ 8.4, 3.2 Hz, 2H, AreH), 7.75 (dt, J ¼ 8.4, 3.2 Hz, 2H,
AreH), 7.54 (s, 1H, AreH), 7.43e7.44 (m, 1H, AreH), 7.32e7.34 (m,
2H, AreH), 5.17 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d:
163.4 (2C), 135.6, 134.5 (2C), 134.3, 129.8, 129.7, 129.4, 128.8 (2C),
127.7, 123.6 (2C), 78.9.
5.2.1.2.1. 2-(3-Methoxy-4-prop-2-ynyloxy-benzyloxy)-isoindole-
5.2.1.2.10. 2-(6-Chloro-pyridin-3-ylmethoxy)-isoindole-1,3-dione
1,3-dione (7a). White solid; yield 79.8%; mp 151e153 ꢁC; 1H NMR
(7j). White solid; yield 67.4%; mp 151e153 ꢁC; 1H NMR (400 MHz,
(400 MHz, CDCl3)
d
: 7.80 (brd, J ¼ 2.4 Hz, 2H, AreH), 7.73 (brs, 2H,
DMSO-d6)
H), 7.86 (brs, 4H, AreH), 7.58 (d, J ¼ 8.0 Hz, 1H, Pyridine-H), 5.24 (s,
2H, PyridineeCH2Oe). 13C NMR (100 MHz, DMSO-d6)
: 163.0 (2C),
d
: 8.54 (s,1H, Pyridine-H), 8.05 (d, J ¼ 8.0 Hz,1H, Pyridine-
AreH), 7.17 (s, 1H, AreH), 6.99e7.01 (m, 2H, AreH), 5.17 (s, 2H,
AreCH2Oe), 4.75 (s, 2H, AreOCH2e), 3.91 (s, 3H, AreOCH3), 2.50 (s,
d
1H, alkynyl-H). 13C NMR (100 MHz, CDCl3)
d: 163.5 (2C),149.5,147.5,
150.8 (2C), 141.1, 134.8 (2C), 129.9, 128.4 (2C), 124.1, 123.3 (2C), 75.6.
5.2.1.2.11. 2-(2,4-Dichloro-benzyloxy)-isoindole-1,3-dione
134.4 (2C), 128.8 (2C), 127.5, 123.4 (2C), 122.3, 113.5, 113.2, 79.6,
78.2, 75.9, 56.6, 55.9.
(7k). White solid; yield 51.8%; mp 154e156 ꢁC; 1H NMR (400 MHz,
5.2.1.2.2. 2-(3,4-Dimethoxy-benzyloxy)-isoindole-1,3-dione (7b).
CDCl3)
d
: 7.82 (dt, J ¼ 8.4, 3.2 Hz, 2H, AreH), 7.75 (dt, J ¼ 8.4, 3.2 Hz,
White solid; yield 49.3%; mp 143e145 ꢁC; 1H NMR (400 MHz,
2H, AreH), 7.59 (d, J ¼ 8.4 Hz, 1H, AreH), 7.41 (d, J ¼ 1.6 Hz, 1H,
AreH), 7.27 (dt, J ¼ 8.4, 1.6 Hz, 1H, AreH), 5.32 (s, 2H, AreCH2Oe).
CDCl3)
d
: 7.80 (dt, J ¼ 8.0, 3.2 Hz, 2H, AreH), 7.73 (dt, J ¼ 8.0, 3.2 Hz,
2H, AreH), 7.13 (s, 1H, AreH), 7.03 (d, J ¼ 8.0 Hz, 1H, AreH), 6.82 (d,
J ¼ 8.0 Hz, 1H, AreH), 5.17 (s, 2H, AreCH2Oe), 3.91 (s, 3H,
13C NMR (100 MHz, CDCl3)
d: 163.3 (2C), 135.8, 135.3, 134.5 (2C),
132.4, 130.5, 129.5, 128.7 (2C), 127.4, 123.6 (2C), 75.7.
AreOCH3), 3.87 (s, 3H, AreOCH3). 13C NMR (100 MHz, CDCl3)
d
:
5.2.1.2.12. 2-(3,4-Dichloro-benzyloxy)-isoindole-1,3-dione
163.5 (2C), 149.8, 148.9, 134.4 (2C), 128.8 (2C), 126.1, 123.4 (2C),
122.7, 112.7, 110.6, 79.7, 55.9, 55.8.
(7l). Purple solid; yield 51.0%; mp 182e184 ꢁC; 1H NMR (400 MHz,
CDCl3)
d
: 7.82 (dt, J ¼ 8.4, 3.2 Hz, 2H, AreH), 7.75 (dt, J ¼ 8.4, 3.2 Hz,

M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
1469
2H, AreH), 7.64 (d, J ¼ 1.6 Hz, 1H, AreH), 7.46 (d, J ¼ 8.4 Hz, 1H,
AreH), 7.39 (dt, J ¼ 8.4, 1.6 Hz, 1H, AreH), 5.15 (s, 2H, AreCH2Oe).
AreH), 6.90 (d, J ¼ 8.0 Hz, 1H, AreH), 5.38 (s, 2H, eNH2), 4.75
(d, J ¼ 2.0 Hz, 2H, AreOCH2e), 4.62 (s, 2H, AreCH2Oe), 3.88
(s, 3H, AreOCH3), 2.50 (s, 1H, alkynyl-H). 13C NMR (100 MHz,
13C NMR (100 MHz, CDCl3)
d: 163.4 (2C), 134.6 (2C), 133.9, 133.5,
132.7, 131.4, 130.6, 128.8 (2C), 128.7, 123.6 (2C), 78.2.
CDCl3)
56.7, 55.8.
5.2.1.3.2. O-(3,4-Dimethoxy-benzyl)-hydroxylamine (8b). Colorless
oil; yield 20.5%; 1H NMR (400 MHz, CDCl3)
: 6.89e6.91 (m, 2H,
d: 149.7, 146.6, 131.4, 120.8, 114.1, 112.0, 78.5, 77.8, 75.8,
5.2.1.2.13. 2-(4-Bromo-benzyloxy)-isoindole-1,3-dione
(7m).
White solid; yield 60.6%; mp 143e145 ꢁC; 1H NMR (400 MHz,
CDCl3)
2H, AreH), 7.50 (d, J ¼ 8.4 Hz, 2H, AreH), 7.41 (d, J ¼ 8.4 Hz, 2H,
AreH), 5.16 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
: 163.4
d: 7.81 (dt, J ¼ 8.0, 3.2 Hz, 2H, AreH), 7.74 (dt, J ¼ 8.0, 3.2 Hz,
d
AreH), 6.82e6.85 (m, 1H, AreH), 4.61 (s, 2H, AreCH2Oe), 3.88 (s, 3H,
d
AreOCH3), 3.86 (s, 3H, AreOCH3). 13C NMR (100 MHz, CDCl3)
d: 149.0,
(2C), 134.5 (2C), 132.7, 131.7 (2C), 131.4 (3C), 128.7 (2C), 123.6 (2C),
78.9.
148.9, 129.9, 121.0, 111.6, 110.0, 77.8, 55.8 (2C).
5.2.1.3.3. O-Benzo[1,3]dioxol-5-ylmethyl-hydroxylamine (8c).
5.2.1.2.14. 2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yloxymethyl)-
Colorless oil; yield 69.6%; 1H NMR (400 MHz, CDCl3)
d
: 6.82 (s, 1H,
benzonitrile (7n). Purple solid; yield 54.3%; mp 195e197 ꢁC; 1H
AreH), 6.73e6.75 (m, 2H, AreH), 5.86 (s, 2H, eOCH2Oe), 5.32
NMR (300 MHz, CDCl3)
d
: 7.28e7.81 (m, 8H, AreH), 5.42 (s, 2H,
: 163.2 (2C), 137.3, 134.6
(brs, 2H, eNH2), 4.51 (s, 2H, AreCH2Oe). 13C NMR (100 MHz,
AreCH2Oe). 13C NMR (75 MHz, CDCl3)
d
CDCl3)
5.2.1.3.4. O-Benzylhydroxylamine (8d). Colorless oil; yield
58.8%; 1H NMR (400 MHz, CDCl3)
: 7.29e7.31 (m, 5H, AreH), 5.25
(brs, 2H, eNH2), 4.61 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d: 147.7, 147.3, 131.4, 122.0, 108.9, 108.0, 101.0, 77.5.
(2C), 133.0, 132.9, 130.8, 129.6, 128.7 (2C), 123.6 (2C), 116.8, 113.0,
77.3.
d
5.2.1.2.15. 3-(1,3-Dioxo-1,3-dihydro-isoindol-2-yloxymethyl)-
benzonitrile (7o). White solid; yield 54.5%; mp 173e175 ꢁC; 1H
d: 137.6, 128.5 (2C), 128.4 (2C), 127.9, 77.9.
NMR (300 MHz, CDCl3)
2H, AreH), 7.60e7.66 (m, 1H, AreH), 7.50e7.55 (m, 1H, AreH), 5.23
(s, 2H, AreCH2Oe). 13C NMR (75 MHz, CDCl3)
: 163.3 (2C), 135.4,
134.6 (2C), 133.8, 132.9, 132.8, 129.4, 128.7 (2C), 123.6 (2C), 118.2,
112.8, 78.4.
d
: 7.79e7.84 (m, 4H, AreH), 7.75e7.78 (m,
5.2.1.3.5. O-(2-Fluoro-benzyl)-hydroxylamine (8e). Colorless oil;
yield 49.3%; 1H NMR (400 MHz, CDCl3)
d: 7.36e7.41 (m, 1H, AreH),
d
7.26e7.28 (m, 1H, AreH), 7.01e7.14 (m, 2H, AreH), 5.42 (brs, 2H,
eNH2), 4.74 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
(AreF), 159.5 (AreF), 130.8, 129.7, 124.5, 123.9, 115.4, 71.3.
d: 162.8
5.2.1.2.16. 4-(1,3-Dioxo-1,3-dihydro-isoindol-2-yloxymethyl)-
5.2.1.3.6. O-(3-Fluoro-benzyl)-hydroxylamine (8f). Colorless oil;
benzonitrile (7p). White solid; yield 54.0%; mp 194e196 ꢁC; 1H
yield 44.1%; 1H NMR (400 MHz, CDCl3)
d
: 7.26e7.31 (m, 1H, AreH),
NMR (400 MHz, DMSO-d6)
(brs, 4H, AreH), 7.74 (d, J ¼ 8.4 Hz, 2H, AreH), 5.28 (s, 2H,
AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
: 163.0 (2C), 139.8,
d
: 7.89 (d, J ¼ 8.4 Hz, 2H, AreH), 7.86
7.04e7.10 (m, 2H, AreH), 6.95e6.99 (m, 1H, AreH), 5.45 (brs, 2H,
eNH2), 4.63 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
(AreF), 161.6 (AreF), 140.3, 130.0, 123.7, 115.0, 114.7, 76.9.
d: 164.1
d
134.8 (2C), 132.3 (2C), 130.0 (2C), 128.4 (2C), 123.2 (2C), 118.5, 111.5,
78.1.
5.2.1.3.7. O-(4-Fluoro-benzyl)-hydroxylamine (8g). Colorless oil;
yield 66.7%; 1H NMR (400 MHz, CDCl3)
d: 7.29e7.32 (m, 2H, AreH),
5.2.1.2.17. 2-(4-Nitro-benzyloxy)-isoindole-1,3-dione (7q). White
7.00e7.04 (m, 2H, AreH), 5.38 (brs, 2H, eNH2), 4.61 (s, 2H,
solid; yield 61.7%; mp 191e193 ꢁC; 1H NMR (400 MHz, CDCl3)
d:
AreCH2Oe). 13C NMR (100 MHz, CDCl3)
(AreF), 133.3, 130.2 (2C), 115.3 (2C), 77.1.
d: 163.7 (AreF), 161.3
8.25 (d, J ¼ 8.0 Hz, 2H, AreH), 7.80 (d, J ¼ 8.0 Hz, 2H, AreH), 7.74
(brs, 4H, AreH), 5.31 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
5.2.1.3.8. O-(2-Chloro-benzyl)-hydroxylamine (8h). Colorless oil;
d
: 163.3 (2C), 148.3, 140.8, 134.7 (2C), 130.0 (2C), 128.6 (2C), 123.7
(4C), 78.3.
5.2.1.2.18. 2-[2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yloxymethyl)-
phenyl]-3-methoxy-acrylic acid methyl ester (7r). Gray solid; yield
32.6%; mp 162e164 ꢁC; 1H NMR (400 MHz, CDCl3)
: 7.79 (brs, 3H,
yield 90.9%; 1H NMR (400 MHz, CDCl3)
d
: 7.38e7.40 (m, 1H, AreH),
7.31e7.33 (m, 1H, AreH), 7.17e7.21 (m, 2H, AreH), 5.26 (brs, 2H,
eNH2), 4.76 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d: 135.2,
133.6, 129.9, 129.4, 129.0, 126.7, 74.9.
d
5.2.1.3.9. O-(3-Chloro-benzyl)-hydroxylamine (8i). Colorless oil;
AreH), 7.71 (brs, 2H, AreH), 7.62 (s, 1H, ]CHOCH3), 7.38 (brs, 2H,
AreH), 7.15 (brs, 1H, AreH), 5.12 (s, 2H, AreCH2Oe), 3.75 (s,
yield 88.0%; 1H NMR (400 MHz, CDCl3)
d: 7.34 (s, 1H, AreH),
7.25e7.26 (m, 2H, AreH), 7.20e7.21 (m, 1H, AreH), 5.43 (brs, 2H,
3H, eOCH3), 3.61 (s, 2H, eOCH3). 13C NMR (100 MHz, CDCl3)
d:
eNH2), 4.62 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d: 139.8,
167.8, 163.3 (2C), 160.6, 134.3 (2C), 133.1, 133.0, 130.9, 130.5, 129.0,
128.9 (2C), 128.0, 123.3 (2C), 109.5, 77.3, 61.9, 51.6.
134.3, 129.7, 128.2, 128.0, 126.2, 76.9.
5.2.1.3.10. O-(6-Chloro-pyridin-3-ylmethyl)-hydroxylamine (8j).
White solid; yield 57.8%; mp 58e60 ꢁC; 1H NMR (400 MHz, DMSO-
5.2.1.3. Synthetic procedures for compounds 8aer. Compound 8a
was synthesized by a facile method improving on the literature
[18]: To a solution of compound 7a in anhydrous ethanol, hydrazine
monohydrate was added. The mixture was refluxed for 1 h. The
resulting solid was removed by filtration, and the filtrate was
evaporated on a rotavap. The residue was slurried in anhydrous
ether and filtered, and the filtrate was washed with water again.
The ether layer was separated, dried with CaCl2 and evaporated to
afford Compound 8a. According to the above process, Compounds
8beq were prepared from 7beq respectively. To be pointed out, as
the product 8r was unstable, the mixture of 7r, ethanol and
hydrazine monohydrate was stirred overnight at room tempera-
ture. The final ether layer was dried with CaCl2 and used rapidly in
the next step of synthesis. All the substituents at the benzene ring
were listed in Scheme 2 and Table 1. As substance 8beq was
unstable, the boiling points of them were not detected.
d6)
d
: 8.34 (d, J ¼ 2.1 Hz, 1H, Pyridine-H), 7.68 (dt, J ¼ 8.1, 2.1 Hz, 1H,
Pyridine-H), 7.30 (d, J ¼ 8.1 Hz, 1H, Pyridine-H), 5.60 (brs,
2H, eNH2), 4.65 (s, 2H, Pyridine-CH2Oe). 13C NMR (100 MHz,
DMSO-d6)
5.2.1.3.11. O-(2,4-Dichloro-benzyl)-hydroxylamine (8k). Colorless
oil; yield 90.3%; 1H NMR (400 MHz, CDCl3)
: 7.34 (s,1H, AreH), 7.32
d: 150.6, 149.5, 138.9, 132.2, 123.9, 74.0.
d
(d, J ¼ 8.0 Hz, 1H, AreH), 7.20 (d, J ¼ 8.0 Hz, 1H, AreH), 5.50 (brs,
2H, eNH2), 4.72 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d:
134.2, 134.0 (2C), 130.6, 129.2, 126.9, 74.2.
5.2.1.3.12. O-(3,4-Dichloro-benzyl)-hydroxylamine (8l). Colorless
oil; yield 94.3%; 1H NMR (400 MHz, CDCl3)
d
: 7.40 (s, 1H, AreH),
7.36 (d, J ¼ 8.0 Hz, 1H, AreH), 7.13 (d, J ¼ 8.0 Hz, 1H, AreH), 5.45
(brs, 2H, eNH2), 4.57 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d: 138.1, 132.3, 131.6, 130.3, 130.0, 127.4, 76.1.
5.2.1.3.13. O-(4-Bromo-benzyl)-hydroxylamine (8m). Colorless
oil; yield 94.0%; 1H NMR (400 MHz, CDCl3)
d: 7.44 (d, J ¼ 8.1 Hz, 2H,
5.2.1.3.1. O-(3-Methoxy-4-prop-2-ynyloxy-benzyl)-hydroxyl-
AreH), 7.19 (d, J ¼ 8.1 Hz, 2H, AreH), 5.39 (brs, 2H, eNH2), 4.58 (s,
amine (8a). White solid; yield 68.9%; mp 30e32 ꢁC; 1H NMR
2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d: 136.6, 131.5 (2C),
(400 MHz, CDCl3)
d
: 7.00 (d, J ¼ 8.0 Hz, 1H, AreH), 6.93 (s, 1H,
130.0 (2C), 121.8, 77.0.

1470
M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
5.2.1.3.14. 2-Aminooxymethyl-benzonitrile (8n). Colorless oil;
yield 70.2%; 1H NMR (300 MHz, CDCl3)
: 7.52e7.57 (m, 1H, AreH),
5.2.1.4.3. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (benzo[1,3]
dioxol-5-ylmethoxy)-amide (3c). Gray solid; yield 61.8%; mp
99e101 ꢁC; 1H NMR (400 MHz, DMSO-d6)
: 12.83 (s, 1H, Pyrro-
leeNH), 11.39 (brs, 1H, eCONHe), 7.00 (s, 1H, AreH), 6.89e6.90
(m, 2H, AreH), 6.79 (d, J ¼ 1.8 Hz, 1H, PyrroleeH), 6.02 (s, 2H,
eOCH2Oe), 4.77 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
d
7.43e7.51 (m, 2H, AreH), 7.31e7.34 (m, 1H, AreH), 5.50 (brs, 2H,
d
eNH2), 4.76 (s, 2H, AreCH2Oe). 13C NMR (75 MHz, CDCl3)
d: 141.2,
132.8, 132.7, 129.4, 128.3, 117.4, 112.2, 75.2.
5.2.1.3.15. 3-Aminooxymethyl-benzonitrile (8o). Colorless oil;
yield 80.2%; 1H NMR (300 MHz, CDCl3)
d: 7.63 (s, 1H, AreH),
d: 157.6, 147.2, 147.1, 129.6, 125.2, 122.8, 112.7, 109.3, 107.9, 105.4,
7.56e7.58 (m, 2H, AreH), 7.43e7.47 (m, 1H, AreH), 5.57 (brs, 2H,
101.0, 97.8, 77.1. HRMS, m/z 416.8906. Calcd for C13H10Br2N2O4,
416.8914.
eNH2), 4.69 (s, 2H, AreCH2Oe).13C NMR (75 MHz, CDCl3)
d: 139.5,
132.4, 131.4, 131.2, 129.1, 118.7, 112.1, 76.2.
5.2.1.4.4. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid benzyloxy-
5.2.1.3.16. 4-Aminooxymethyl-benzonitrile (8p). Colorless oil;
amide (3d). Gray solid; yield 34.0%; mp 113e115 ꢁC; 1H NMR
yield 81.7%; 1H NMR (400 MHz, CDCl3)
d
: 7.50 (d, J ¼ 6.8 Hz, 2H,
(400 MHz, CDCl3)
eCONHe), 7.13e7.21 (m, 5H, AreH), 6.67 (s, 1H, PyrroleeH), 4.82 (s,
2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
: 159.9, 134.5, 129.3
d: 10.94 (s, 1H, PyrroleeNH), 9.56 (brs, 1H,
AreH), 7.35 (d, J ¼ 6.8 Hz, 2H, AreH), 5.48 (brs, 2H, eNH2), 4.61 (s,
2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d
: 143.5, 132.1 (2C),
d
128.4 (2C), 118.8, 111.2, 76.5.
(2C), 129.0, 128.7 (2C), 123.7, 115.3, 107.3, 100.2, 79.1. HRMS, m/z
372.9022. Calcd for C12H10Br2N2O2, 372.9016.
5.2.1.3.17. O-(4-Nitro-benzyl)-hydroxylamine (8q). Colorless oil;
yield 86.5%; 1H NMR (400 MHz, CDCl3)
d
: 8.14 (d, J ¼ 8.4 Hz, 2H,
5.2.1.4.5. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (2-fluoro-
AreH), 7.50 (d, J ¼ 8.4 Hz, 2H, AreH), 5.70 (brs, 2H, eNH2), 4.77 (s,
benzyloxy)-amide (3e). Gray solid; yield 57.6%; mp 82e84 ꢁC; 1H
2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d: 147.2, 145.7, 128.3
NMR (400 MHz, DMSO-d6) d: 12.86 (s, 1H, PyrroleeNH), 11.47 (brs,
(2C), 123.4 (2C), 76.2.
1H, eCONHe), 7.43e7.50 (m, 2H, AreH), 7.21e7.23 (m, 2H, AreH),
6.79 (s,1H, PyrroleeH), 4.95 (s, 2H, AreCH2Oe). 13C NMR (100 MHz,
5.2.1.4. Synthetic procedures for target compounds 3aer, 2a, 2g, 2r,
4a, 4g, 4r, 5a, 5g, 5r. Compound 3a was synthesized as follows: To
a solution of compound 3 (0.40 g, 1.5 mmol) in dry CH2Cl2 (15.0 mL)
0.5 mL oxalyl choride was added and stirred. 10 min later, two
drops of dry DMF was added to the above solution. The mixture was
stirred overnight at room temperature. Then the dark solution was
evaporated under vacuum to get the 4,5-dibromo-1H-pyrrole-2-
carbonyl chloride. Compounds 8a (0.31 g, 1.5 mmol) was dissolved
in the solution of dry CH2Cl2 (20.0 mL) and anhydrous pyridine
(0.3 mL). The 4,5-dibromo-1H-pyrrole-2-carbonyl chloride diluted
in dry CH2Cl2 (10.0 mL) was added dropwise to the above solution
of 8a. The whole mixture continued to stir for 1 h at room
temperature after the carbonyl chloride dripped off, then 50.0 mL
water and 100.0 mL ethyl acetate were added, washed with 2 N
dilute hydrochloric acid, saturated sodium bicarbonate and water
respectively. Separating the organic layer, the solvent was removed
by distillation. The residue was recrystallized with ethyl acetate/
petroleum ether (60e90 ꢁC, v/v ¼ 1:4) to give 4, 5-dibromo-N-(3-
DMSO-d6) d: 162.0 (AreF), 159.6 (AreF), 157.7, 132.1, 130.8, 125.1,
124.3, 122.6, 115.3, 112.8, 105.5, 97.9, 70.7. HRMS, m/z 390.8922.
Calcd for C12H9Br2FN2O2, 390.8922.
5.2.1.4.6. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (3-fluoro-
benzyloxy)-amide (3f). Gray solid; yield 63.8%; mp 99e101 ꢁC; 1H
NMR (400 MHz, DMSO-d6) d: 12.87 (s, 1H, PyrroleeNH), 11.50 (brs,
1H, eCONHe), 7.42e7.44 (m, 1H, AreH), 7.28e7.30 (m, 2H, AreH),
7.19e7.26 (m, 1H, AreH), 6.79 (s, 1H, PyrroleeH), 4.91 (s, 2H,
AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
d: 163.3 (AreF), 160.8
(AreF), 157.8, 138.8, 130.3, 125.1, 124.6, 115.3, 114.9, 112.9, 105.7,
97.9, 76.5. HRMS, m/z 390.8925. Calcd for C12H9Br2FN2O2,
390.8922.
5.2.1.4.7. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (4-fluoro-
benzyloxy)-amide (3g). Gray solid; yield 58.3%; mp 140e142 ꢁC; 1H
NMR (400 MHz, DMSO-d6) d: 12.85 (s, 1H, PyrroleeNH), 11.44 (brs,
1H, eCONHe), 7.47e7.50 (m, 2H, AreH), 7.19e7.24 (m, 2H, AreH),
6.80 (s,1H, PyrroleeH), 4.87 (s, 2H, AreCH2Oe). 13C NMR (100 MHz,
DMSO-d6) d: 163.2 (AreF), 160.8 (AreF), 157.6, 132.1, 131.2 (2C),
125.1, 115.1 (2C), 112.7, 105.5, 97.9, 76.5. HRMS, m/z 390.8923. Calcd
for C12H9Br2FN2O2, 390.8922.
methoxy-4-(prop-2-ynyloxy)
benzyloxy)-1H-pyrrole-2-carbox-
amide (3a, 0.38 g, 56.5%). Using the same procedure, compounds
2ae5r were prepared from 8aer with corresponding carbonyl
chloride respectively. To be pointed out, compound 3r need to be
isolated from its crude residue by flash chromatography on silica
gel eluting with ethyl acetate/petroleum [elution solvent: ethyl
acetate/petroleum ether (60e90 ꢁC), v/v ¼ 1:4]. All the substituents
at the benzene ring were listed in Scheme 2 and Table 1.
5.2.1.4.8. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (2-chloro-
benzyloxy)-amide (3h). Gray solid; yield 44.5%; mp 124e126 ꢁC; 1H
NMR (400 MHz, DMSO-d6) d: 12.90 (s, 1H, PyrroleeNH), 11.54 (brs,
1H, eCONHe), 7.59e7.60 (m, 1H, AreH), 7.50e7.52 (m, 1H, AreH),
7.40e7.42 (m, 2H, AreH), 6.84 (s, 1H, PyrroleeH), 5.05 (s, 2H,
AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
d: 157.8, 133.3, 133.2,
5.2.1.4.1. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (3-methoxy-
4-prop-2-ynyloxy-benzyloxy)-amide (3a). Gray solid; yield 56.5%;
131.3, 130.2, 129.2, 127.2, 125.0, 112.9, 105.6, 97.9, 74.1. HRMS, m/z
406.8619. Calcd for C12H9Br2ClN2O2, 406.8625.
mp 164e166 ꢁC; 1H NMR (400 MHz, DMSO-d6)
d: 12.84 (s, 1H,
5.2.1.4.9. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (3-chloro-
PyrroleeNH), 11.40 (brs, 1H, eCONHe), 7.08 (s, 1H, AreH), 7.02 (d,
J ¼ 8.0 Hz, 1H, AreH), 6.93 (d, J ¼ 8.0 Hz, 1H, AreH), 6.80 (d,
J ¼ 2.0 Hz, 1H, PyrroleeH), 4.82 (s, 2H, AreCH2Oe), 4.78 (d,
J ¼ 2.0 Hz, 2H, AreOCH2e), 3.78 (s, 3H, AreOCH3), 3.54 (s, 1H,
benzyloxy)-amide (3i). Gray solid; yield 80.0%; mp 121e123 ꢁC; 1H
NMR (400 MHz, CDCl3)
eCONHe), 7.21 (s, 1H, AreH), 7.08e7.13 (m, 3H, AreH), 6.69 (s, 1H,
PyrroleeH), 4.79 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, CDCl3)
d: 10.87 (s, 1H, PyrroleeNH), 9.79 (brs, 1H,
d
:
alkynyl-H). 13C NMR (100 MHz, DMSO-d6)
d
: 157.6, 148.9, 146.5,
159.9, 136.7, 134.4, 129.9, 129.0 (2C), 127.1, 123.5, 115.5, 107.4, 100.3,
78.1. HRMS, m/z 406.8625. Calcd for C12H9Br2ClN2O2, 406.8625.
5.2.1.4.10. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (6-chloro-
pyridin-3-ylmethoxy)-amide (3j). Gray solid; yield 58.8%; mp
129.3,125.2,121.2,113.6,112.9 (2C),105.4, 97.9, 79.2, 78.2, 77.2, 55.9,
55.4. HRMS, m/z 456.9223. Calcd for C16H14Br2N2O4, 456.9227.
5.2.1.4.2. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (3,4-dime-
thoxy-benzyloxy)-amide (3b). Gray solid; yield 30.1%; mp
214e216 ꢁC; 1H NMR (400 MHz, DMSO-d6)
d: 12.87 (s, 1H, Pyrro-
197e199 ꢁC; 1H NMR (300 MHz, DMSO-d6)
d: 12.83 (s, 1H, Pyrro-
leeNH), 11.47 (brs, 1H, eCONHe), 8.47 (s, 1H, Pyridine-H), 7.93 (d,
J ¼ 8.0 Hz, 1H, Pyridine-H), 7.56 (d, J ¼ 8.0 Hz, 1H, Pyridine-H), 6.78
(s, 1H, PyrroleeH), 4.93 (s, 2H, PyridineeCH2Oe). 13C NMR
leeNH), 11.38 (brs, 1H, eCONHe), 7.03 (s, 1H, AreH), 6.93 (brs, 2H,
AreH), 6.79 (s, 1H, PyrroleeH), 4.80 (s, 2H, AreCH2Oe), 3.76 (s, 3H,
AreOCH3), 3.75 (s, 3H, AreOCH3). 13C NMR (75 MHz, DMSO-d6)
d:
(100 MHz, DMSO-d6) d: 157.8, 150.1 (2C), 140.4, 131.1, 124.9, 124.0,
157.6,148.9,148.5,128.1,125.3,121.6,112.7 (2C),111.3,105.4, 97.8, 77.3,
112.9, 105.6, 97.9, 73.8. HRMS, m/z 407.8578. Calcd for
55.4, 55.3. HRMS, m/z 432.9219. Calcd for C14H14Br2N2O4, 432.9227.
C11H8Br2ClN3O2, 407.8578.

M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
1471
5.2.1.4.11. 4,5-Dibromo-1H-pyrrole-2-carboxylic
dichloro-benzyloxy)-amide (3k). Gray solid; yield 50.0%; mp
202e204 ꢁC; 1H NMR (400 MHz, DMSO-d63
: 12.86 (s, 1H, Pyr-
acid
(2,4-
(100 MHz, DMSO-d6) d: 166.9, 160.8, 157.6, 134.9, 132.1, 130.8, 128.2,
127.5, 127.4, 125.2, 112.8, 108.4, 105.4, 97.8, 74.7, 61.7, 51.2. HRMS,
m/z 486.9330. Calcd for C17H16Br2N2O5, 486.9333.
)
d
roleeNH), 11.47 (s, 1H, eCONHe), 7.66 (s, 1H, AreH), 7.58 (d,
J ¼ 8.4 Hz, 1H, AreH), 7.47 (d, J ¼ 8.4 Hz, 1H, AreH), 6.79 (s, 1H,
PyrroleeH), 4.98 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
5.2.1.4.19. 1H-Pyrrole-2-carboxylic acid (3-methoxy-4-prop-2-
ynyloxy-benzyloxy)-amide (2a). White solid; yield 58.8%; mp
129e131 ꢁC; 1H NMR (400 MHz, DMSO-d6)
d: 11.58 (s, 1H, Pyrro-
d
: 157.8, 134.3, 133.9, 132.7, 132.6, 128.7, 127.3, 125.0, 112.9, 105.6,
leeNH), 11.24 (brs, 1H, eCONHe), 7.10 (s, 1H, H-9), 7.02 (d,
J ¼ 8.0 Hz, 1H, H-12), 6.95 (d, J ¼ 8.0 Hz, 1H, H-13), 6.92 (s, 1H, H-4),
6.71 (s, 1H, H-2), 6.09 (s, 1H, H-3), 4.83 (s, 2H, H-7), 4.79 (s, 2H, H-
14), 3.78 (s, 3H, H-17), 3.55 (s, 1H, H-16). 13C NMR (100 MHz, DMSO-
97.9, 73.5. HRMS, m/z 440.8227. Calcd for C12H8Br2Cl2N2O2,
440.8234.
5.2.1.4.12. 4,5-Dibromo-1H-pyrrole-2-carboxylic
dichloro-benzyloxy)-amide (3l). Gray solid; yield 54.5%; mp
94e96 ꢁC; 1H NMR (400 MHz, DMSO-d6)
: 12.87 (s, 1H, Pyrro-
leeNH), 11.48 (brs, 1H, eCONHe), 7.74 (s, 1H, AreH), 7.65 (d,
J ¼ 8.0 Hz, 1H, AreH), 7.42 (d, J ¼ 8.0 Hz, 1H, AreH), 6.78 (s, 1H,
PyrroleeH), 4.89 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
acid
(3,4-
d6) d: 159.7 (s, C-6), 148.9 (s, C-10), 146.4 (s, C-11), 129.6 (s, C-8),
d
123.1 (s, C-5), 122.0 (d, C-4), 121.1 (d, C-13), 113.6 (d, C-12), 112.8 (d,
C-9), 110.3 (d, C-2), 108.6 (d, C-3), 79.2 (s, C-15), 78.2 (d, C-16), 77.1
(t, C-7), 55.9 (t, C-14), 55.4 (q, C-17). HRMS, m/z 323.1004. Calcd for
C16H16N2O4, 323.1002 [M þ Na]þ.
d: 157.8, 137.2, 130.9, 130.8, 130.6, 130.4, 128.9, 124.9, 112.8, 105.7,
5.2.1.4.20. 1H-Pyrrole-2-carboxylic acid (4-fluoro-benzyloxy)-
amide (2g). Gray solid; yield 76.9%; mp 144e146 ꢁC; 1H NMR
97.9, 75.7. HRMS, m/z 440.8228. Calcd for C12H8Br2Cl2N2O2,
440.8234.
(300 MHz, DMSO-d6) d: 11.58 (s, 1H, PyrroleeNH), 11.27 (brs, 1H,
5.2.1.4.13. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (4-bromo-
eCONHe), 7.48e7.51 (m, 2H, AreH), 7.19e7.24 (m, 2H, AreH), 6.91
(s, 1H, PyrroleeH), 6.68 (s, 1H, PyrroleeH), 6.08 (d, J ¼ 2.4 Hz, 1H,
PyrroleeH), 4.87 (s, 2H, AreCH2Oe). 13C NMR (75 MHz, DMSO-d6)
benzyloxy)-amide (3m). Gray solid; yield 80.1%; mp 160e162 ꢁC; 1H
NMR (400 MHz, DMSO-d6) d: 12.84 (s, 1H, PyrroleeNH), 11.44 (brs,
1H, eCONHe), 7.59 (d, J ¼ 8.0 Hz, 2H, AreH), 7.39 (d, J ¼ 8.0 Hz, 2H,
d: 163.2 (AreF), 160.7 (AreF), 159.7, 132.4, 131.0 (2C), 123.0, 122.1,
AreH), 6.78 (d, J ¼ 2.4 Hz, 1H, PyrroleeH), 4.86 (s, 2H, AreCH2Oe).
115.0 (2C), 110.2, 108.6, 76.4. HRMS, m/z 257.0701. Calcd for
13C NMR (100 MHz, DMSO-d6)
d: 157.7, 135.3, 131.2 (2C), 131.0 (2C),
125.1, 121.5, 112.8, 105.5, 97.9, 76.4. HRMS, m/z 450.8114. Calcd for
C12H9Br3N2O2, 450.8121.
C12H11FN2O2, 257.0697 [M þ Na]þ.
5.2.1.4.21. 3-Methoxy-2-{2-[(1H-pyrrole-2-carbonyl)-amino-
oxymethyl]-phenyl}-acrylic acid methyl ester (2r). Light yellow oil;
5.2.1.4.14. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (2-cyano-
yield 56.6%; 1H NMR (400 MHz, DMSO-d6)
d: 11.59 (s, 1H, Pyrro-
benzyloxy)-amide (3n). Gray solid; yield 46.1%; mp 193e195 ꢁC; 1H
leeNH), 11.25 (brs, 1H, eCONHe), 7.67 (s, 1H, ]CHOCH3), 7.64 (d,
J ¼ 7.2 Hz, 1H, AreH), 7.31e7.36 (m, 2H, AreH), 7.12 (d, J ¼ 7.2 Hz, 1H,
AreH), 6.93 (s, 1H, PyrroleeH), 6.72 (s, 1H, PyrroleeH), 6.11 (s, 1H,
PyrroleeH), 4.79 (s, 2H, AreCH2Oe), 3.78 (s, 3H, eOCH3), 3.60 (s, 3H,
NMR (400 MHz, DMSO-d6) d: 12.86 (s, 1H, PyrroleeNH), 11.51 (brs,
1H, eCONHe), 7.87 (d, J ¼ 6.8 Hz, 1H, AreH), 7.70e7.74 (m, 2H,
AreH), 7.58 (d, J ¼ 6.8 Hz,1H, AreH), 6.78 (s,1H, PyrroleeH), 5.06 (s,
2H, AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
d: 157.8, 138.9,
eOCH3). 13C NMR (100 MHz, DMSO-d6)
d: 166.9, 160.8, 159.7, 135.3,
133.2, 132.9, 130.8, 129.3, 124.9, 117.2, 112.9, 112.1, 105.6, 97.9, 74.7.
HRMS, m/z 397.8971. Calcd for C13H9Br2N3O2, 397.8968.
131.8,130.8,128.0,127.3(2C),123.1,122.0,110.3,108.6,108.5, 74.7, 61.7,
51.1. HRMS, m/z 353.1101. Calcd for C17H18N2O5, 353.1108 [M þ Na]þ.
5.2.1.4.22. 3,4,5-Tribromo-1H-pyrrole-2-carboxylic acid (3-
methoxy-4-prop-2-ynyloxy-benzyloxy)-amide (4a). White solid;
5.2.1.4.15. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (3-cyano-
benzyloxy)-amide (3o). Gray solid; yield 40.1%; mp 190e192 ꢁC; 1H
NMR (300 MHz, DMSO-d6)
d
: 12.87 (s, 1H, PyrroleeNH), 11.50 (brs,
yield 39.0%; mp 142e144 ꢁC; 1H NMR (400 MHz, DMSO-d6)
d:
1H, eCONHe), 7.92 (s, 1H, AreH), 7.76e7.83 (m, 2H, AreH),
7.59e7.62 (m, 1H, AreH), 6.79 (s, 1H, PyrroleeH), 4.95 (s, 2H,
13.13 (s, 1H, PyrroleeNH), 11.08 (brs, 1H, eCONHe), 7.08 (s, 1H,
AreH), 7.01 (d, J ¼ 8.0 Hz, 1H, AreH), 6.97 (d, J ¼ 8.0 Hz, 1H, AreH),
4.82 (s, 2H, AreCH2Oe), 4.78 (d, J ¼ 2.0 Hz, 2H, AreOCH2e), 3.78
(s, 3H, AreOCH3), 3.54 (s, 1H, alkynyl-H). 13C NMR (100 MHz,
AreCH2Oe). 13C NMR (75 MHz, DMSO-d6)
d: 157.8, 137.7, 133.4,
132.0, 131.9, 129.5, 125.0, 118.6, 112.9, 111.3, 105.6, 97.9, 76.1. HRMS,
m/z 397.8971. Calcd for C13H9Br2N3O2, 397.8968.
DMSO-d6) d: 157.3, 148.8, 146.5, 129.1, 124.2, 121.3, 113.5, 112.8,
5.2.1.4.16. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (4-cyano-
104.7, 102.0, 100.1, 79.2, 78.2, 77.1, 55.9, 55.4. HRMS, m/z
558.8296. Calcd for C16H13Br3 N2O4, 558.8297 [M þ Na]þ.
5.2.1.4.23. 3,4,5-Tribromo-1H-pyrrole-2-carboxylic acid (4-flu-
oro-benzyloxy)-amide (4g). Gray solid; yield 45.4%; mp 172e174 ꢁC;
benzyloxy)-amide (3p). Gray solid; yield 35.2%; mp 212e214 ꢁC; 1H
NMR (400 MHz, DMSO-d6) d: 12.87 (s, 1H, PyrroleeNH), 11.52 (brs,
1H, eCONHe), 7.86 (d, J ¼ 8.0 Hz, 2H, AreH), 7.64 (d, J ¼ 8.0 Hz, 2H,
AreH), 6.78 (s, 1H, PyrroleeH), 4.98 (s, 2H, AreCH2Oe). 13C NMR
1H NMR (400 MHz, DMSO-d6)
d
: 13.16 (brs, 1H, PyrroleeNH), 11.14
(s, 1H, eCONHe), 7.49e7.52 (m, 2H, AreH), 7.19e7.24 (m, 2H,
AreH), 4.87 (s, 2H, AreCH2Oe). 13C NMR (100 MHz, DMSO-d6)
d:
(100 MHz, DMSO-d6) d: 157.8, 141.6, 132.2 (2C), 129.2 (2C), 124.9,
118.7, 112.9, 110.8, 105.7, 97.9, 76.3. HRMS, m/z 397.8968. Calcd for
C13H9Br2N3O2, 397.8968.
163.2 (AreF), 160.8 (AreF), 157.4, 132.0, 131.2 (2C), 124.1, 115.0 (2C),
104.9, 102.0, 100.1, 76.3. HRMS, m/z 492.7999. Calcd for
C12H8Br3FN2O2, 492.7992 [M þ Na]þ.
5.2.1.4.17. 4,5-Dibromo-1H-pyrrole-2-carboxylic acid (4-nitro-
benzyloxy)-amide (3q). Gray solid; yield 60.6%; mp 191e193 ꢁC; 1H
NMR (400 MHz, DMSO-d6)
d: 12.88 (s, 1H, PyrroleeNH),11.56 (s,1H,
5.2.1.4.24. 3-Methoxy-2-{2-[(3,4,5-tribromo-1H-pyrrole-2-
carbonyl)-aminooxymethyl]-phenyl}-acrylic acid methyl ester
(4r). White solid; yield 34.7%; mp 179e181 ꢁC; 1H NMR (400 MHz,
eCONHe), 8.25 (d, J ¼ 8.4 Hz, 2H, AreH), 7.73 (d, J ¼ 8.4 Hz, 2H,
AreH), 6.79 (d, J ¼ 2.4 Hz, 1H, PyrroleeH), 5.04 (s, 2H, AreCH2Oe).
13C NMR (100 MHz, DMSO-d6)
d
: 157.8, 147.2, 143.7, 129.5 (2C),
DMSO-d6) d: 13.15 (s, 1H, PyrroleeNH), 11.02 (brs, 1H, eCONHe),
124.9, 123.3 (2C), 112.9, 105.7, 97.9, 76.0. HRMS, m/z 417.8859. Calcd
for C12H9Br2N3O4, 417.8867.
7.68 (s, 1H, ]CHOCH3), 7.56 (d, J ¼ 7.2 Hz, 1H, AreH), 7.31e7.34 (m,
2H, AreH), 7.10 (d, J ¼ 7.2 Hz, 1H, AreH), 4.75 (s, 2H, AreCH2Oe),
3.80 (s, 3H, eOCH3), 3.60 (s, 3H, eOCH3). 13C NMR (100 MHz,
5.2.1.4.18. 2-{2-[(4,5-Dibromo-1H-pyrrole-2-carbonyl)-amino-
oxymethyl]-phenyl}-3-methoxy-acrylic acid methyl ester (3r). Light
DMSO-d6) d: 166.9, 160.9, 157.1, 134.7, 132.0, 130.9, 128.2, 127.6,
yellow oil; yield 32.6%; 1H NMR (400 MHz, DMSO-d6)
d: 12.85 (s,
127.4, 124.0, 108.4, 104.8, 102.1, 100.2, 74.7, 61.7, 51.2. HRMS, m/z
1H, PyrroleeNH), 11.43 (brs, 1H, eCONHe), 7.65 (s, 1H, ]CHOCH3),
7.56 (d, J ¼ 7.2 Hz, 1H, AreH), 7.30e7.35 (m, 2H, AreH), 7.09 (d,
J ¼ 7.2 Hz, 1H, AreH), 6.79 (s, 1H, PyrroleeH), 4.73 (s, 2H,
AreCH2Oe), 3.77 (s, 3H, eOCH3), 3.57 (s, 3H, eOCH3). 13C NMR
588.8397. Calcd for C17H15Br3N2O5, 588.8403 [M þ Na]þ.
5.2.1.4.25. 4,5-Dichloro-1H-pyrrole-2-carboxylic acid (3-methoxy-
4-prop-2-ynyloxy-benzyloxy)-amide (5a). Yellow solid; yield 41.8%;
mp 169e171 ꢁC; 1H NMR (400 MHz, DMSO-d6)
d: 12.90 (s, 1H,

1472
M.-Z. Wang et al. / European Journal of Medicinal Chemistry 46 (2011) 1463e1472
PyrroleeNH), 11.45 (brs, 1H, eCONHe), 7.08 (s, 1H, AreH), 7.02 (d,
J ¼ 8.4 Hz, 1H, AreH), 6.93 (d, J ¼ 8.4 Hz, 1H, AreH), 6.77 (s, 1H,
PyrroleeH), 4.81 (s, 2H, AreCH2Oe), 4.78 (s, 2H, AreOCH2e), 3.77
(s, 3H, AreOCH3), 3.55 (s, 1H, alkynyl-H). 13C NMR (100 MHz,
5.3. Antifungal activity
The fungicidal activities of the compounds 3aer, 2a, 2g, 2r, 4a,
4g, 4r, 5a, 5g, 5r, 2aa, 2ab were tested in vitro against A. solani,
C. arachidicola, F. omysporum, G. zeae and P. piricola and their rela-
tive inhibitory ratio (%) had been determined by using the myce-
lium growth rate method [30]. Anthranilamide and fenpiclonil
were used as control. After the mycelia grew completely, the
diameter of the mycelia was measured and the inhibition rate was
calculated according to the formula:
DMSO-d6) d: 157.7, 148.9, 146.5,129.2,121.9,121.2,115.6,113.5, 112.8,
109.7, 108.0, 79.2, 78.2, 77.2, 55.9, 55.3. HRMS, m/z 391.0232. Calcd
for C16H14Cl2N2O4, 391.0223 [M þ Na]þ.
5.2.1.4.26. 4,5-Dichloro-1H-pyrrole-2-carboxylic acid (4-fluoro-
benzyloxy)-amide (5g). Yellow solid; yield 69.5%; mp 123e125 ꢁC;
1H NMR (400 MHz, DMSO-d6)
d: 12.96 (brs, 1H, PyrroleeNH), 11.55
(brs, 1H, eCONHe), 7.51e7.54 (m, 2H, AreH), 7.23e7.28 (m, 2H,
I¼(D1ꢀD2)/D1 ꢂ 100% where I was the inhibition rate, D1 was
the average diameter of mycelia in the blank test, and D2 was the
average diameter of mycelia in the presence of those compounds.
AreH), 6.81 (s, 1H, PyrroleeH), 4.91 (s, 2H, AreCH2Oe). 13C NMR
(100 MHz, DMSO-d6) d: 163.2 (AreF), 160.8 (AreF), 157.7, 132.1,
131.2 (2C), 121.8, 115.7, 115.1 (2C), 109.8, 108.0, 76.5. HRMS, m/z
The inhibition ratio of those compounds at the dose of 50 m
g mLꢀ1
324.9921. Calcd for C12H9Cl2FN2O2, 324.9917 [M þ Na]þ.
was summarized in Table 2. The EC50 values of compounds 2a, 3a
and fenpiclonil had been experimented and calculated by the
Scatchard method. And the results were summarized in Table 3.
5.2.1.4.27. 2-{2-[(4,5-Dichloro-1H-pyrrole-2-carbonyl)-amino-
oxymethyl]-phenyl}-3-methoxy-acrylic acid methyl ester (5r). Light
yellow oil; yield 53.5%; 1H NMR (400 MHz, DMSO-d6)
d: 12.89 (s,
1H, PyrroleeNH), 11.45 (brs, 1H, eCONHe), 7.64 (s, 1H, ]CHOCH3),
7.55e7.58 (m, 1H, AreH), 7.30e7.37 (m, 2H, AreH), 7.07e7.10 (m,
1H, AreH), 6.75 (s, 1H, PyrroleeH), 4.73 (s, 2H, AreCH2Oe), 3.77 (s,
Acknowledgments
We gratefully acknowledge the financial support of this work by
the National Key Project for Basic Research (2010CB26106) and the
Tianjin S&T Commission.
3H, eOCH3), 3.57 (s, 3H, eOCH3). 13C NMR (100 MHz, DMSO-d6)
d:
166.9,160.8,157.7,134.9,132.0,130.8,128.2,127.5,127.4,121.9,115.6,
109.9, 108.5, 108.0, 74.7, 61.7, 51.1. HRMS, m/z 421.0327. Calcd for
C17H16Cl2N2O5, 421.0328 [M þ Na]þ.
References
5.2.1.5. Synthetic procedures for compounds 2aa, 2ab. Compound
2aa and 2ab were synthesized as follows: To a solution of
compound 2a (0.1 g, 0.33 mmol) in dry DMF (20.0 mL) potassium
carbonate (1.0 g, 7.2 mmol) was added and stirred. 10 min later, two
drops of CH3I was added to the above solution. The mixture was
stirred for 5 h at room temperature [5]. Then the suspension was
extracted with ethyl acetate/water system. Separating the organic
layer, the solvent was removed by distillation to give the crude
residue. 2aa and 2ab were isolated from the residue by flash
chromatography on silica gel eluting with ethyl acetate/petroleum
[elution solvent: ethyl acetate/petroleum ether (60e90 ꢁC), v/
v ¼ 1:8]. Respective substituents at the benzene ring were listed in
Scheme 2 and Table 1.
[1] G.W. Gribble, Chem. Soc. Rev. 28 (1999) 335e346.
[2] J.F. Liu, S.P. Guo, B. Jiang, Chin. J. Org. Chem. 25 (2005) 788e799.
[3] G.W. Gribble, J. Nat. Prod. 55 (1992) 1353e1395.
[4] K.H. Pée, J.M. Ligon, Nat. Prod. Rep. 17 (2000) 157e164.
[5] P.M. Fresneda, P. Molina, M.A. Sanz, Tetrahedron Lett. 42 (2001) 851e854.
[6] T. Lindel, H. Hoffmann, M. Hochgurtel, J. Pawlik, J. Chem. Ecol. 26 (2000)
1477e1496.
[7] J.A. Ponasik, D.J. Kassab, B. Ganem, Tetrahedron Lett. 37 (1996) 6041e6044.
[8] B. Chanas, J.R. Pawlik, T. Lindelb, W. Fenicalb, J. Exp. Mar. Biol. Eco. 208 (1996)
185e196.
[9] J.A. Ponasik, S. Conova, D. Kinghorn, W.A. Kinney, D. Rittschof, B. Ganem,
Tetrahedron 54 (1998) 6977e6986.
[10] M.A.F. Biabani, M. Baake, B. Lovisetto, H. Laatsch, E. Helmke, H. Weyland,
J. Antibiot. 51 (1998) 333e340.
[11] B.J. Ludwig, F. Dursch, M. Auerbach, K. Tomeczek, F.M. Berger, J. Med. Chem.
10 (1967) 556e563.
[12] S.A. Glover, G.P.A. Hammond, J. Org. Chem. 63 (1998) 9684e9689.
[13] M.A. Bailén, R. Chinchilla, D.J. Dodsworth, C. Nájera, Tetrahedron Lett. 42
(2001) 5013e5016.
[14] N.D. Kokare, R.R. Nagawade, V.P. Ranea, D.B. Shindea, Tetrahedron Lett. 48
(2007) 4437e4440.
5.2.1.5.1. 1H-Pyrrole-2-carboxylic acid (3-methoxy-4-prop-2-
ynyloxy-benzyloxy)-methyl-amide (2aa). Light yellow solid; yield
60.1%; mp 99e101 ꢁC; 1H NMR (400 MHz, CDCl3)
d: 9.86 (brs, 1H,
PyrroleeNH), 6.98 (d, J ¼ 8.0 Hz, 1H, AreH), 6.87e6.89 (m, 2H,
AreH), 6.87e6.89 (m, 2H, PyrroleeH), 6.16e6.19 (m, 1H,
PyrroleeH), 4.79 (s, 2H, AreCH2Oe), 4.70 (d, J ¼ 2.4 Hz, 2H,
AreOCH2e), 3.80 (s, 3H, AreOCH3), 3.28 (s, 3H, eCONCH3), 2.45 (s,
[15] H.Sauter,Strobilurinsand othercomplexIIIinhibitors.in:W.Krämer, U.Schirmer
(Eds.), Modern Crop Protection Compounds. Wiley, 2007, pp. 457e491.
[16] B.P. Hodge, R.W. Rickards, J. Chem. Soc. Perkin. Trans. 1 (1963) 2543e2545.
[17] H. Kikuchi, M. Sekiya, Y. Katou, K. Ueda, T. Kabeya, S. Kurata, Y. Oshima, Org.
Lett. 11 (2009) 1693e1695.
1H, alkynyl-H). 13C NMR (100 MHz, CDCl3)
d: 160.7, 148.6, 146.2,
[18] Y. Li, H.Q. Zhang, J. Liu, X.P. Yang, Z.J. Liu, J. Agric, Food Chem. 54 (2006)
3636e3640.
127.1, 122.5, 121.0, 120.9, 114.3, 112.9, 111.8, 109.3, 77.2, 75.2, 75.0,
55.6, 54.9, 33.7. HRMS, m/z 337.1165. Calcd for C17H18N2O4, 337.1159
[M þ Na]þ.
[19] C.X. Zeng, S.H. Xu, Y.Q. Li, Y.F. Wang, Chin. J. Org. Chem. 25 (2005) 954e958.
[20] H.J. Anderson, S.F. Lee, Canad. J. Chem. 43 (1965) 409e414.
[21] B.P. Hodge, R.W. Rickards, J. Chem. Soc. (1965) 459e470.
[22] B.R. Clark, C.D. Murphy, Org. Biomol. Chem. 7 (2009) 111e116.
[23] D.O.A. Garrido, G. Buldain, M.I. Ojea, B. Frydman, J.Org.Chem. 53(1988)403e407.
[24] H.T. Wu, P.L. Micca, M.S. Makar, M. Miura, Bioorg. Med. Chem. 14 (2006)
5083e5092.
[25] A.V. Oeveren, J.F.G.A. Jansen, B.L. Feringa, J. Org. Chem. 59 (1994) 5999e6007.
[26] M. Yasuyuki, S. Takahiro, I. Yutaka, Y. Hiroyuki, F. Makoto, T. Mitsuru,
I. Yoshiyuki, Y. Satoru, K. Noriaki. US 2004152894 (2004).
[27] D.M. Wallace, S.H. Leung, M.O. Senge, K.M. Smith, J. Org. Chem 58 (1993)
7245e7257.
[28] A. Mai, S. Massa, R. Ragno, I. Cerbara, F. Jesacher, P. Loidl, G. Brosch, J. Med.
Chem. 46 (2003) 512e524.
[29] L.F. Fieser, M. Fieser, Regent for Organic Synthesis. John Wiley and Sons, Inc.,
New York, 1967, pp. 485e486.
[30] N.C. Chen, Bioassay of Pesticides. Beijing Agricultural University Press, Beijing,
China, 1991, pp. 161e162.
5.2.1.5.2. 1-Methyl-1H-pyrrole-2-carboxylic acid (3-methoxy-4-
prop-2-ynyloxy-benzyloxy)-methyl-amide
(2ab). Light
yellow
solid; yield 20.0%; mp 94e96 ꢁC; 1H NMR (400 MHz, CDCl3)
d
:
6.99 (d, J ¼ 8.0 Hz, 1H, AreH), 6.88 (s, 1H, AreH), 6.86 (d,
J ¼ 8.0 Hz, 1H, AreH), 6.83 (s, 1H, PyrroleeH), 6.71 (s, 1H,
PyrroleeH), 6.08e6.09 (m, 1H, PyrroleeH), 4.76 (s, 2H,
AreCH2Oe), 4.76 (s, 2H, AreOCH2e), 3.84 (s, 3H, AreOCH3), 3.81
(s, 3H, Pyrrole-NCH3), 3.34 (s, 3H, eCONCH3), 2.51 (s, 1H,
alkynyl-H). 13C NMR (100 MHz, CDCl3)
d: 162.9, 149.5, 147.1,
128.4, 127.8, 123.6, 122.0, 116.5, 113.7, 113.1, 107.1, 78.3, 75.9, 75.8,
56.6, 55.8, 36.8, 35.1. HRMS, m/z 351.1316. Calcd for C18H20N2O4,
351.1315 [M þ Na]þ.