Synthesis, screening and quantitative structure-activity relationship (QSAR) studies of some glutamine analogues for possible anticancer activity

Article abstract of DOI:10.1016/S0968-0896(02)00079-2

We described the syntheses, biological activities and QSAR studies of 36 new 5-n-substituted-2-(substituted benzenesulphonyl) glutamines 6-41 with different substitutions. These compounds were designed as structural analogues of most reactive amino acid, 'glutamine' (GLN), especially in the tumor cells. They present the new basic lateral chains at R₅ position as well as different substitutions at 2′, 3′, 4′, and 5′ positions on the benzene ring. The synthesized compounds have been tested for antitumor activity against Ehrlich ascites carcinoma (EAC) in Swiss albino mice using percentage inhibition of tumor weight as inhibitory parameter. In order to elucidate the structural requirements for antitumor activity, quantitative structure-activity relationship (QSAR) studies have been performed using extra thermodynamic model of Hansch. QSAR equations showed that the electronic parameter (σ) on the aromatic ring system, steric parameter (Es) and to some extent Sterimol length of the substituent (L) on the aliphatic side chain correlate significantly with the antitumor activity. Resonance factor occupies the major electronic contribution on the aromatic ring system to the activity.

Full text of DOI:10.1016/S0968-0896(02)00079-2

Bioorganic & Medicinal Chemistry 10 (2002) 2119–2131
Synthesis, Screening and Quantitative Structure–Activity
Relationship (QSAR) Studies of Some Glutamine
Analogues for Possible Anticancer Activity
K. Srikanth, Ch. Anil Kumar, Balaram Ghosh and Tarun Jha*
Division of Medicinal Chemistry, Department of Pharmaceutical Technology, Jadavpur University, Kolkata 700 032, India
Received 22 January 2002;accepted 12 February 2002
Abstract—We described the syntheses, biological activities and QSAR studies of 36 new 5-n-substituted-2-(substituted benzenesul-
phonyl) glutamines 6–41 with different substitutions. These compounds were designed as structural analogues of most reactive
amino acid, ‘glutamine’ (GLN), especially in the tumor cells. They present the new basic lateral chains at R5 position as well as
different substitutions at 20, 30, 40, and 50 positions on the benzene ring. The synthesized compounds have been tested for antitumor
activity against Ehrlich ascites carcinoma (EAC) in Swiss albino mice using percentage inhibition of tumor weight as inhibitory
parameter. In order to elucidate the structural requirements for antitumor activity, quantitative structure–activity relationship
(QSAR) studies have been performed using extra thermodynamic model of Hansch. QSAR equations showed that the electronic
parameter (s) on the aromatic ring system, steric parameter (Es) and to some extent Sterimol length of the substituent (L) on the
aliphatic side chain correlate significantly with the antitumor activity. Resonance factor occupies the major electronic contribution
on the aromatic ring system to the activity. # 2002 Elsevier Science Ltd. All rights reserved.
Introduction
and macrophages in culture are glutamate, aspertate,
lactate and ammonia (25% of the GLN used is com-
pletely oxidized). The high rate of utilization of GLN by
the cells of immune system serves to maintain a high
intracellular concentration of intermediates of biosyn-
thetic pathways. GLN is synthesized in skeletal muscles.
The synthesis of interleukin-2 by lymphocytes8 and of
interleukin-1 of macrophages is GLN dependent. Low-
ered plasma GLN concentration contributes at least in
part to the immunosuppression,9 which is common to
most of the anticancer drugs. Overall, the amino acid
GLN is main substrate in many biosynthetic pathways
especially during cell division.
Cancer has been described as nitrogen trap.1 Glutamine
(GLN), a non essential amino acid, plays a key role in
tumor cell growth by supplying its amide nitrogen atoms
in the biosyntheses of other amino acids, purine, pyr-
imidine bases,2 aminosugars and coenzymes, via a family
comprised of 16 amido transferases3 with diversified
mechanisms.4 It also plays the central role in multiple
metabolic pathways and considered to be the most
essential component of tissue culture media for not only
as nitrogen source but also as carbon source.5 Rates of
cell growth, DNA and protein synthesis and thymidine
transport correlated with the GLN concentration in the
culture media.6,7 GLN uptake reported6 to be mediated
by the system of ASC (aryl sulphatase C) family of
transporters. In all cells, regardless of the tissue origin,
sodium-dependent GLN transport is mediated almost
exclusively by a single carrier. Cell growth is a function
of GLN influx and it was suggested that GLN supply
glutamate and cystine perhaps for glutathione synthesis.
The major products of GLN utilization by lymphocytes
Hence, structural variants of GLN were synthesized
which may supposedly show antitumor activities by
GLN10 and/or Folic acid antagonism. In order to identify
the chemical structural features important for the anti-
tumor activity, quantitative structure–activity relationship
(QSAR) studies have been performed.
Results and Discussion
Syntheses of 5-N-substituted-2-(substituted benzene-
sulphonyl) glutamines is carriedout according to Scheme 1.
*Corresponding author. Tel.: +91-33-483-0677;fax: +91-33-472-
4927;e-mail: sreekanth2k@yahoo.com
0968-0896/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(02)00079-2

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K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
final compounds are summarized in Tables 1 and 2,
respectively.
Antitumor activity of the final compounds were evaluated
by dissolving them in phosphate buffered saline (PBS) or
by suspending in PBS with 2% Tween 80 (where and when
necessary), 2 m mol/kg/day for 7 consecutive days, after
intraperitoneal inoculation of mice with 2Â106 EAC cells.
For the tumor growth inhibition, antitumor activity was
assessed on the basis of the percentage tumor inhibition
(%TI), calculated from mean tumor weight treated (T)
and control (C) mice on the day of evaluation. The% TI
was calculated as (1ÀT/C)Â100. The biological activity
results are presented in Table 3.
Figure 1. General structure for 5-N-substituted-2-(substituted benze-
nesulphonyl) glutamines.
We started with chlorosulphonation11 of substituted
benzene 1, to get corresponding sulphonyl chloride 2a–
2b, except in the case of p-tosyl chloride and benzene-
sulphonyl chloride, which were purchased. This halide
proved to be versatile synthon10 in the subsequent steps
in the preparation of substituted benzenesulphonyl glu-
tamic acids 4. With the application of Schotten–Bauman
reaction,12 2-(substituted benzenesulphonyl) glutamic
acids 4a–4e were prepared by one step condensation of
2 with l-glutamic acid 3. In this reaction, alkaline med-
ium was maintained to remove the hydrochloric acid
which is formed during condensation. Reaction of resul-
tant intermediate 4 with acetyl chloride afforded cyclized
acid intermediate, 1-(substituted benzenesulphonyl)-5-
oxopyrrolidine-2-carboxylicacids 5a–5e. Nucleophilic
displacement of intermediate 5 with amines13 (amino-
dehydroxylation) produced the corresponding amides
6–41 as crystalline solids with varying yields ranging
from 48 to 98%. Physical data of the intermediates and
Development of QSAR equations
In order to identify the substituent effects on the anti-
tumor activity, QSAR studies of 5-N-substituted 2-(sub-
stituted benzenesulphonyl) glutamines (Fig. 1) against
Ehrlich ascites carcinoma (EAC) were performed by
using the Hansch approach.14 Biological activity (BA)
data was calibrated to their logarithmic values (log BA)
and are listed in Table 3.
The congener series possesses the substitution on the
aromatic ring system at 20, 30, 40, 50 positions and at the
5-N position on the aliphatic side chain, as shown in Fig-
ure 1. Physicochemical parameters were taken as sum of all
the substituents on the benzene ring for each compound.
Scheme 1. General synthetic protocol for 5-N-substituted-2-(substituted benzenesulphonyl) glutamines: (a) HOSO2Cl;(b) 2 N NaOH/HCl;(c) CH
COCl;(d) R–NH 2.
3

K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
Table 1. Physical data of intermediate compounds
2121
MW
Compd
R1
R2
R3
R4
Mp (ꢀC)
% Yield
Molecular formula
2a
2b
4a
4b
4c
4d
4e
5a
5b
5c
5d
5e
CH3
H
H
CH3
H
H
H
H
CH3
H
H
H
NO2
H
H
NO2
H
H
H
H
NO2
H
H
CH3
CH3
H
CH3
C2H5
H
CH3
H
CH3
C2H5
H
NO2
H
H
NO2
H
H
H
H
NO2
H
H
42–44
Liquid
120–122
138–140
130–132
89–90
145–147
75–77
94–96
76.39
83.54
69.30
73.20
71.40
59.29
56.66
74.46
92.37
93.64
92.55
69.78
C7H6N1O4S1Cl
C7H6N1O4S1Cl
C12H15N1O6S1
C12H14N2O8S1
C12H14N2O8S1
C13H17N1O6S1
C11H13N1O6S1
C12H13N1O5S1
C12H12N2O7S1
C12H12N2O7S1
C13H15N1O5S1
C11H11N1O5S1
235.50
235.50
301.32
346.32
346.32
315.35
287.29
283.30
328.30
328.30
297.30
269.28
38–39
40–41
155–157
H
H
H
Table 2. Physical data of different substituted benzenesulphonyl glutamines 6–41
Compd
R1
R2
R3
R4
R5
Mp (ꢀC)
% Yield
Molecular formula
MW
6
7
8
9
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
H
H
H
H
H
H
H
H
H
H
CH3
CH3
H
H
H
H
H
H
H
H
H
H
i-Butyl
i-Propyl
i-Butyl
H
CH3
C2H5
n-C3H7
n-C4H9
i-Propyl
i-Butyl
C6H11
160–162
176–178
179–181
178–180
176–180
192–194
195
218–220
215–218
212
98.04
53.70
75.90
70.00
88.20
70.00
70.00
86.60
85.10
90.00
80.00
79.00
86.23
82.67
79.41
95.23
70.81
70.36
56.81
81.81
65.88
48.14
85.10
82.26
65.90
85.00
80.00
74.45
68.78
67.75
78.45
46.69
83.56
66.43
85.54
54.65
C15H22N2O5S1
C15H22N2O5S1
C16H24N2O5S1
C12H15N3O7S1
C13H17N3O7S1
C14H19N3O7S1
C15H21N3O7S1
C16H23N3O7S1
C15H21N3O7S1
C16H23N3O7S1
C18H25N3O7S1
C18H19N3O7S1
C19H21N3O7S1
C17H25N3O7S1
C18H27N3O7S1
C12H15N3O7S1
C13H17N3O7S1
C14H19N3O7S1
C15H21N3O7S1
C16H23N3O7S1
C17H25N3O7S1
C18H27N3O7S1
C15H21N3O7S1
C16H23N3O7S1
C18H25N3O7S1
C19H21N3O7S1
C18H19N3O7S1
C14H20N2O5S1
C15H22N2O5S1
C16H24N2O5S1
C17H26N2O5S1
C18H28N2O5S1
C19H30N2O5S1
C16H24N2O5S1
C20H24N2O5S1
C19H22N2O5S1
342.42
342.42
356.44
345.33
359.36
373.39
387.41
401.44
387.41
401.44
427.48
421.43
435.46
415.46
429.49
345.33
359.36
373.39
387.41
401.44
415.47
429.49
387.41
401.44
427.48
435.46
421.43
328.39
342.42
356.44
370.47
384.50
398.52
356.44
404.49
390.46
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
H
H
H
H
230
C6H5
210–213
180–182
146
C6H5CH2
n-C5H11
n-C6H13
H
CH3
C2H5
n-C3H7
n-C4H9
n-C5H11
n-C6H13
i-Propyl
i-Butyl
C6H11
C6H5CH2
C6H5
CH3
H
138–140
175–176
184–185
196–197
193–194
185–186
179–180
186–188
192–194
189–191
195–197
195–196
219–221
162–164
150–152
145–147
155–157
162–164
168–170
171–173
155–157
174–175
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
n-C3H7
n-C4H9
n-C5H11
n-C6H13
–CH(CH3)2
C6H5CH2
C6H5
QSAR studies were performed against antitumor activ-
ities of the compounds in training set by multiple
regression analysis. Physicochemical parameters used in
developing QSAR models are compiled15,16 in Tables 4
and 5. Correlation analysis was performed on all the
descriptors and the resultant correlation matrix is given
in Table 6. Depending on the intercorrelation among
the independent descriptors and also the their individual
correlation with BA, different possible combinations of
parameters were subjected to multiple regression analysis.
phenyl ring, steric factor (EsR5) and to some extent on
length (LR5) of the substituents at the R5 position, as
shown in eq 1.
Log ðBAÞ ¼ 1:5789 ðÆ0:0929Þ À 0:3180 ðÆ0:1267Þ
ꢀs þ 0:3353 ðÆ0:0504Þ Es R5 þ 0:1113ðÆ0:0152Þ
L R5 þ 0:2460 ðÆ0:715ÞI1 þ 0:2742 ðÆ0:0576ÞI2
n ¼ 30 R ¼ 0:8731; R2 ¼ 0:7623 F5;24 ¼ 15:40;
SEE ¼ 0:1014 p ¼ 0:0000
ð1Þ
Antineoplastic activity was found to have good corre-
lation with Hammett’s electronic constant (ꢀs) on the
where, ‘n’ represents the number of data points, ‘R’ is
correlation coefficient, ‘F’ is the F-ratio between variances

2122
K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
Table 3. Antitumor activities of 5-N-substituted-2-(substituted benzenesulphonyl) glutamines and ClogP and CMR values for the whole molecules
Compd
R1
R2
R3
R4
R5
% Inhibition of
Tumor weight (BA)
Log (BA)
ClogP
CMR
6
7
8
9
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
H
H
H
H
H
H
H
H
H
H
CH3
CH3
H
H
H
H
H
H
H
H
H
H
i-Butyl
i-Propyl
i-Butyl
H
CH3
C2H5
n-C3H7
n-C4H9
i-Propyl
i-Butyl
C6H11
52.73
50.00
25.00
37.50
68.75
25.00
50.00
62.50
62.50
12.00
33.00
33.00
60.17
60.83
67.37
49.53
40.86
27.05
26.95
41.37
24.88
59.45
37.64
45.95
35.33
22.35
59.60
90.45
38.46
65.64
55.64
56.36
65.37
41.53
37.50
70.76
100.00
1.7220
1.6990
1.3980
1.5740
1.8370
1.3980
1.6990
1.7960
1.7960
1.0790
1.5190
1.5190
1.7790
1.7840
1.8280
1.6950
1.6110
1.4320
1.4310
1.6170
1.3960
1.7740
1.5760
1.6620
1.5480
1.3490
1.7750
1.9560
1.5850
1.8170
1.7450
1.7510
1.8150
1.6180
1.5740
1.8500
2.0000
0.9000
0.7800
1.4000
0.3000
0.3400
0.8600
1.3900
1.9200
1.1700
1.7900
2.3700
2.5700
2.3600
2.4500
2.9800
0.2200
0.2600
0.7800
1.3100
1.8400
2.3700
2.9000
1.0900
1.7100
2.2900
2.2800
2.4900
0.4700
1.0000
1.5300
2.0600
2.5900
3.1200
1.3100
2.5000
2.7100
—
8.7000
8.7000
9.1600
7.9200
8.3800
8.8400
9.3100
9.7700
9.3100
9.7700
10.5200
10.4300
10.8900
10.2400
10.7000
7.9200
8.3800
8.8400
9.3100
9.7700
10.2400
10.7000
9.3100
9.7700
10.5200
10.8900
10.4300
8.2300
8.7000
9.1600
9.6200
10.0900
10.5500
9.1600
10.7400
10.2800
–
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
H
H
H
H
C6H5
C6H5CH2
n-C5H11
n-C6H13
H
CH3
C2H5
n-C3H7
n-C4H9
n-C5H11
n-C6H13
i-Propyl
i-Butyl
C6H11
C6H5CH2
C6H5
CH3
H
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
Mitomycin-C
C2H5
n-C3H7
n-C4H9
n-C5H11
n-C6H13
–CH(CH3)2
C6H5CH2
C6H5
ClogP, calculated log P;CMR, calculated molar refractivity.
Table 4. Aromatic substituent constants used in deriving QSAR equations15,16
Substituent
p
s
MR
0.103
0.565
Es
J
R
H
0.00
0.56
0.00 (sÀp, sÀm)
À0.06 (sÀo)
À0.17 (sÀp)
À0.36 (sÀo)
À0.15 (sÀp)
0.71 (sÀm)
0.00
0.00
0.00
CH3
À1.24
À1.24
À0.13
C2H5
NO2
1.02
À0.28
1.03
0.736
À1.31
À2.52
À0.05
À0.10
0.67
0.16
MR values are scaled by factor of 0.1 as usual.
of the predicted and observed activities, and ‘SEE’ is
standard error of the estimate. It explains 76.23% of var-
iances in the activity.
sharing larger residuals. Both I1 and I2 were found to be
significantly contributing to the activity whereas, when
an indicator parameter was used for the i-butyl group,
there was no improvement in the QSAR model. This
implies that smaller groups at the R5 position may give
the better ligand fit into the active site. Field (ꢀJ ) and
Resonance (ꢀR) constants of the phenyl ring also yiel-
ded equally appreciable QSAR equations (eqs 2 and 3).
The negative ꢀs term in eq 1 explains the necessity of
electron donating groups on the phenyl ring for better
anticancer activity. This may be due to possible nucleo-
philic reactions of the ligand with the electrophilic
functions of the receptor surface. The positive coeffi-
cient of EsR5 indicates steric bulk at the R5 position
may not be useful for the activity or may be detrimental
to the activity. The length of the R5 substituent is also
marginally contributing to the activity.
Log ðBAÞ ¼ 1:5409 ðÆ0:0811Þ À 0:1614ðÆ0:0563Þ
ꢀJ þ 0:3153 ðÆ0:0475ÞEsR5 þ 0:1054 ðÆ0:0147Þ
L R5 þ 0:2294 ðÆ0:0687ÞI1 þ 0:2767 ðÆ0:0555ÞI2
n ¼ 30; R ¼ 0:8812; R2 ¼ 0:7765; F5;24 ¼ 16:68;
Indicator parameters, I1 and I2 were used for methyl
and i-propyl groups at the R5 position, as they were
SEE ¼ 0:0983; p ¼ 0:0000
ð2Þ

K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
Table 5. Aliphatic substituent constants used in deriving QSAR equations15,16
2123
B5
Substituent
p
MR
Es
L
B1
H
CH3
C2H5
0.00
0.04
0.56
1.09
1.62
2.15
2.68
2.07
0.87
1.49
2.27
2.06
0.103
0.357
0.817
1.29
1.747
2.217
2.677
2.497
1.287
1.747
2.277
2.867
0.00
À1.24
À1.31
À1.43
À1.63
À1.64
À1.54
À1.81
À1.71
À2.17
À1.01
À1.51
2.06
2.87
4.11
4.92
6.17
6.97
8.22
6.17
4.11
4.92
6.28
4.62
1.00
1.52
1.52
1.52
1.52
1.52
1.52
1.91
1.90
1.52
1.71
1.52
1.00
2.04
3.17
3.49
4.54
4.94
5.96
3.49
3.17
4.45
3.11
6.02
n-C3H7
n-C4H9
n-C5H11
n-C6H13
C6H11
i-Propyl
i-Butyl
C6H5
C6H5CH2
MR values are scaled by factor of 0.1 as usual.
Table 6. Correlation matrix for the descriptors used in QSAR studies
ꢀp
ꢀs
ꢀMR
ꢀEs
ꢀF
ꢀR
pR5
EsR5
MRR5
LR5
Log (BA)
I2
I1
ꢀp
ꢀs
1
À0.62
1
0.93
À0.49
0.93
1
0.94
À0.82
À0.76
1.00
À1.00
À1.00
0.16
À0.95
0.81
0.74
À0.91
0.86
0.81
À1.00
0.994
1.00
0.19
À0.06
À0.04
0.16
À0.16
À0.15
1.00
À0.08
0.29
0.29
0.12
À0.03
À0.03
0.10
À0.10
À0.09
0.96
0.11
0.00
0.02
0.08
À0.08
À0.06
0.90
0.35
À0.15
À0.06
0.29
À0.30
À0.27
0.10
0.07
À0.23
À0.21
0.14
0.006
0.055
0.075
À0.02
0.022
0.032
À0.49
0.137
À0.48
À0.43
0.293
0.389
1.00
À0.62
À0.49
0.942
À0.95
À0.91
0.196
À0.08
0.12
0.11
0.36
0.08
0.01
ꢀMR
ꢀEs
ꢀF
À0.82
À0.76
À1.00
À0.17
0.81
0.86
0.74
0.81
1.00
0.99
0.17
0.20
À0.13
À0.15
À0.39
À0.13
À0.35
À0.4
ꢀR
pR5
À0.06
À0.04
À0.16
À0.15
0.197
À0.1
À0.42
EsR5
MRR5
LR5
Log (BA)
I2
0.29
À0.03
0.00
0.29
À0.04
0.02
À0.17
0.17
À0.42
1.00
À0.51
À0.47
0.27
À0.01
0.1
0.08
À0.1
À0.08
À0.30
À0.14
0.02
0.97
0.90
À0.51
À0.47
0.27
1.00
0.84
0.84
1.00
À0.06
À0.27
À0.15
0.032
0.20
1.00
À0.15
À0.23
0.06
À0.06
À0.21
0.07
0.29
0.14
À0.02
0.10
À0.39
À0.01
À0.35
À0.48
0.21
0.29
À0.13
À0.4
0.29
0.29
1.00
0.38
I1
À0.49
0.14
À0.43
Table 7. Observed and calculated activities of 5-N-substituted-2-(substituted benzenesulphonyl) glutamines
Compd
Observed
Eq 1
Eq 2
Eq 3
Eq 4
Pred
LOO
Pred
LOO
Pred
LOO
Pred
LOO
7
8
9
1.699
1.398
1.574
1.837
1.398
1.699
1.796
1.079
1.519
1.784
1.828
1.695
1.611
1.432
1.431
1.617
1.774
1.576
1.548
1.349
1.775
1.956
1.585
1.817
1.745
1.751
1.815
1.618
1.574
1.85
1.772
1.434
1.697
1.892
1.486
1.536
1.626
1.288
1.548
1.694
1.867
1.656
1.576
1.445
1.495
1.567
1.825
1.585
1.506
1.434
1.787
1.936
1.531
1.581
1.653
1.738
1.911
1.671
1.520
1.873
1.658
1.313
1.699
1.871
1.471
1.499
1.570
1.349
1.525
1.643
1.812
1.621
1.546
1.468
1.517
1.576
1.828
1.641
1.523
1.466
1.778
1.978
1.574
1.592
1.683
1.772
1.963
1.782
1.567
1.897
1.718
1.382
1.656
1.857
1.460
1.507
1.610
1.274
1.519
1.657
1.820
1.656
1.580
1.460
1.507
1.576
1.820
1.610
1.519
1.450
1.783
1.967
1.569
1.617
1.686
1.767
1.930
1.720
1.560
1.893
1.817
1.460
1.779
1.924
1.493
1.527
1.570
1.349
1.550
1.686
1.876
1.630
1.544
1.446
1.501
1.562
1.839
1.589
1.501
1.445
1.789
1.924
1.525
1.562
1.646
1.737
1.938
1.685
1.515
1.877
1.735
1.398
1.659
1.859
1.459
1.507
1.607
1.270
1.519
1.659
1.824
1.659
1.582
1.459
1.507
1.576
1.824
1.607
1.519
1.449
1.787
1.963
1.563
1.611
1.681
1.763
1.928
1.711
1.554
1.891
1.725
1.376
1.709
1.869
1.465
1.494
1.544
1.334
1.519
1.642
1.818
1.632
1.552
1.462
1.512
1.572
1.833
1.622
1.516
1.459
1.784
1.975
1.566
1.590
1.678
1.769
1.967
1.753
1.558
1.903
1.668
1.331
1.650
1.858
1.465
1.512
1.625
1.289
1.525
1.658
1.816
1.650
1.577
1.465
1.512
1.579
1.816
1.625
1.525
1.457
1.777
1.969
1.576
1.623
1.690
1.769
1.927
1.737
1.568
1.888
1.749
1.399
1.714
1.872
1.465
1.493
1.538
1.331
1.519
1.644
1.823
1.637
1.556
1.461
1.512
1.573
1.838
1.618
1.516
1.458
1.788
1.968
1.559
1.586
1.673
1.765
1.964
1.741
1.551
1.901
10
11
12
14
15
16
19
20
21
22
23
24
25
27
28
30
31
32
33
34
35
36
37
38
39
40
41
Pred, predicted activities;Observed, observed activities.

2124
K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
Table 8. Observed and calculated activities of compounds in test set as per QSAR models (eqs 1–4)
Compd
Observed
Calcd (eq 1)
Calcd (eq 2)
Calcd (eq 3)
Calcd (eq 4)
6
1.2950
1.5820
1.7160
1.4530
1.6940
1.3240
1.2469
1.5793
1.7772
1.4571
1.6581
1.2890
1.4183
1.6082
1.8284
1.4758
1.6526
1.2466
1.3754
1.5758
1.7829
1.4502
1.6570
1.2737
1.2939
1.5763
1.7865
1.4492
1.6585
1.2698
13
17
18
26
29
Calcd, calculated activities.
Log ðBAÞ ¼ 1:4635 ðÆ0:0745Þ À 0:8034ðÆ0:2828Þ
ꢀR þ 0:3202ðÆ0:0478ÞEsR5 þ 0:1067 ðÆ0:01477Þ
L R5 þ 0:2336 ðþ0:0690ÞI1 þ 0:2761 ðÆ0:0557Þ I2
n ¼ 30 R ¼ 0:8806; R2 ¼ 0:7755; F5;24 ¼ 16:58;
SEE ¼ 0:0985; p ¼ 0:0000
essential for possible reactions of the ligand with elec-
tron deficient receptor surface. Resonance also plays a
significant part in these interactions. Indicator para-
meters I1 and I2 and a positive steric parameter at the
R5 position explain why the smaller groups in that
position may give better fit with the receptor site. Some
possible hydrophobic interactions of the aromatic ring
system with the receptor surface are not ruled out but a
smaller coefficient of ꢀp and a lack of hydrophobic
parameter in the aliphatic portion necessitates the sub-
stitution elsewhere on the basic nucleus for proper entry
of the compound into the hydrophobic pocket of the
receptor site.
ð3Þ
Both eqs 2 and 3 are significant at the 99% level. Also,
they explain 77.60% of variances in activity. From these
equations it is clear that resonance effect (ꢀR) sig-
nificantly influences the biological activity when com-
pared with field effect (ꢀJ );possibly electron donating
groups on the phenyl ring favor biological activity
through resonance.
Experimental
Chemistry
Hydrophobic interactions of the aromatic ring system
were also found to be playing a role in ligand–receptor
interactions (eq 4).
All the melting points were determined on Mel-Temp II
melting point apparatus and are uncorrected. Elemental
or micro analyses (C, H, N) of the compounds were
performed on 2400 Series II CHN analyser of Perkin–
Elmer. Analytical results indicated by the symbols of
the elements are within Æ0.4% of the theoretical values.
Infrared spectra were performed on M-500 Model of
Buck Scientific, using KBr discs. The frequencies are
Log ðBAÞ ¼ 1:3975 ðÆ0:0771Þ þ 0:1501ðÆ0:0553Þ
ꢀp þ 0:3011 ðÆ0:0480ÞEs R5 þ 0:1021 ðÆ0:0151Þ
L R5 þ 0:2175 ð0:0697ÞI1 þ 0:2807 ðÆ0:561ÞI2
n ¼ 30; R ¼ 0:8777; R2 ¼ 0:7704; F5;24 ¼ 16:11;
SEE ¼ 0:0996; p ¼ 0:0000
ð4Þ
1
expressed in cmÀ1. H NMR spectra were recorded on
Bruker (300 MHz), Varian gemini (200 MHz) and Bru-
ker RDX (200 MHz) using Tetramethyl Silane (Me4 Si)
as an internal standard for solutions in CDCl3 and
DMSO-d6. Chemical shifts are expressed in d ppm
(parts per million) down field from Me4 Si and the cou-
pling constant J in Hz. Splitting patterns have been
designated as follows: s (singlet), d (doublet), t (triplet),
dd (doublet of doublet), m (multiplet). Position of
The data within the parentheses are significant at 99%
level. The hydrophobic constant at the R5 position was
not found to contribute to the activity. The robustness
of all these QSAR models was validated by the leave-
one-out (LOO) method and the calculated activities are
given in Table 7. All the models are equally robust and
valid, which predicts the compounds in test set almost
consistently. These calculated activities of the test
compounds are given in Table 8.
1
hydrogens described in H NMR interpretation are as
per general structure (Fig. 1) and substitutions at R5
position has taken the superscript ‘00’ (double dash). The
mass spectra (FAB) were recorded on JEOL-JMS-SX-
102 mass spectrometer. PNBA (p-nitro benzyl alcohol)
was used as matrix (M+) which showed the M+1 peak
at 154, 2M+1 peak at 307.
Conclusion
All the final compounds have shown the range of anti-
cancer activities depending on the nature of substitution
at different parts of the structure. Standard drug Mito-
mycin-C at a dose level of 1 mg/kg body wt has shown
100% tumor inhibition. In order to identify the essential
chemical structural features responsible for antitumor
activity, QSAR studies were performed using the
Hansch approach. From the QSAR study, it is evident
that electron-donating groups20 on the phenyl ring are
Reactions were monitored by analytical thin-layer
chromatography performed on silica gel G plates. The
spots were located keeping the TLC plates in iodine
chamber. p-Toluene sulphonyl chloride, o-nitro toluene, m-
nitro toluene, benzenesulphonyl chloride, chlorosulphonic
acid, l-glutamic acid, chloroform, ethyl acetate, acetyl
chloride and ethyl alcohol were the commercial products.

K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
2125
General synthetic procedures
2H, H2-4), 2.02 (m, 2H, HA-3), 1.82 (m, 1H, HB-3). IR
(KBr, cmÀ1): 3227, 3031 (Ar–C–H str), 2861 (ali C–H
str), 1694 (C¼O str), 1512 (N¼O str of Ar–NO2), 1404,
1336 and 1165 (S¼O str of SO2NH), 1104, 894, 713
(Ar–C–H def ), 661. Anal. C12H14N2O8S1 (C, H, N)
calcd: 41.62, 4.05, 8.09;found: 41.59, 3.95, 8.12.
Method 1: substituted benzenesulphonyl chloride 2. To a
mixture of substituted benzene (0.1 mol) in chloroform
(50 mL), in a 500-mL flask equipped with dropping
funnel, thermometer, reflux condensor, is added chlor-
osulphonic acid (0.25 mol) drop wise over a period of
45–60 min. The reaction mixture was magnetically stir-
red at 0 ꢀC in a bath containing a freezing mixture of ice
and salt. Chlorosulphonic acid was added at such a rate
that the temperature of the reaction mixture did not
exceed 5 ꢀC. After the complete addition of chlor-
osulphonic acid, the reaction mixture was stirred for
another 45 min at room temperature and the mixture
was poured on to crushed ice. The product was extrac-
ted with three 50-mL portions of chloroform and dried
overnight over anhydrous sodium sulphate. Chloroform
was distilled off. The product was sufficiently pure for
no further purification. It has been taken for the next
step.
2-(40-Ethyl benzenesulphonyl) glutamic acid 4d. IR (KBr,
cmÀ1): 3253, 3031 (Ar–C–H str), 2876 (ali C–H str),
1702 (C¼O str), 1580, 1409, 1335 and 1148 (S¼O str of
SO2NH), 979, 897, 783 (Ar–C–H def), 651. Anal.
C13H17N1O6S1 (C, H, N) calcd: 49.52, 5.40, 4.44;found:
49.83, 5.19, 4.32.
2-(Benzenesulphonyl) glutamic acid 4e. IR (KBr, cmÀ1):
3191, 3031 (Ar–C–H str), 2881 (ali C–H str), 1726
(C¼O str), 1695, 1428, 1375, 1303 and 1155 (S¼O str of
SO2NH), 970, 888, 765 and 724 (Ar–C–H def). Anal.
C11H13N1O6S1 (C, H, N) calcd: 45.99, 4.53, 4.88;found:
45.96, 4.52, 4.62.
Method 2. 2-(Substituted benzenesulphonyl) glutamic
acid. 4a–4e. l-glutamic acid (14.7 g: 0.1 mol) was taken
in a 250-mL conical flask and sodium hydroxide solu-
tion (2N) was added slowly until all the glutamic acid
dissolved and the mixture became distinctly alkaline to
phenolphthalein. The reaction mixture was stirred on
the magnetic stirrer with temperature maintained at
70 ꢀC using a hot water bath. Substituted benzenesul-
phonyl chloride (0.15 mol) was added in small portions
with constant stirring and from time to time addition of
sodium hydroxide (2 N) to keep the reaction mixture
alkaline. The reaction was continued until a clear
homogeneous solution resulted or the thin-layer chro-
matography showed the reaction to be complete. After
the reaction was over, it was allowed to cool to room
temperature and filtered to separate undissolved solid
matter, if any. The filtrate was acidified with con-
centrated hydrochloric acid and saturated with sodium
chloride. The product was extracted with three 50-mL
portions of ethyl acetate. Ethyl acetate layer was
washed with brine solution (15 mL) and dried overnight
over anhydrous sodium sulphate. The solvent was dis-
tilled off to get the product.
Method 3. 1-(Substituted benzenesulphonyl)-5-oxo pyrro-
lidine-2-carboxilic acids 5a–5e. 2-(Substituted benzene-
sulphonyl) glutamic acid (0.01 mol) was taken in 100-
mL round-bottomed flask, fitted with reflux condensor
and calcium chloride guard tube. Acetyl chloride (0.025
mol) was added to it and refluxed for 2 h in a boiling
water bath. The completion of the reaction was tested
by thin-layer chromatography. After the reaction was
completed, the reaction mixture was cooled to room
temperature and then poured on to crushed ice with
continuous stirring. The precipitated product was fil-
tered and recrystallized from water with charcoal
treatment.
1-(40 -Methyl benzenesulphonyl)-5-oxopyrrolidine-2-car-
boxilic acid 5a. IR (KBr, cmÀ1): 3480, 3392, 2876 (ali
C–H str), 1715 (C¼O str), 1691, 1437, 1339 and 1154
(S¼O str of SO2NH), 944, 870, 789 and 736 (Ar–C–H
def), 671. Anal. C12H13N1O5S1 (C, H, N) calcd: 50.88,
4.59, 4.95;found: 50.68, 4.49, 5.21.
1 - (20 - Methyl 50 - nitro benzenesulphonyl) - 5 - oxopyrrol-
idine-2-carboxilic acid 5b. IR (KBr, cmÀ1): 3498, 3033
(Ar–C–H str), 2878 (ali C–H str), 1725 (C¼O str), 1586,
1512 (N¼O str of Ar–NO2), 1338 and 1161 (S¼O str of
SO2NH), 951, 887 (C–N str of Ar–NO2), 792 and 736
(Ar–C–H def). Anal. C12H12N2O7S1 (C, H, N) calcd:
43.90, 3.66, 8.54;found: 43.54, 3.56, 8.21.
2-(40-Methyl benzenesulphonyl) glutamic acid 4a. IR
(KBr, cmÀ1): 3253, 3031 (Ar–C–H str), 2871 (ali C–H
str), 1698 (C¼O str), 1409, 1334 and 1150 (S¼O str of
SO2NH), 985, 816 (Ar–C–H def), 658. Anal. C12H15
N1O6S1 (C, H, N) calcd: 47.84, 4.98, 4.04;found: 47.64,
4.78, 4.02.
1 - (40 - Methyl 30 - nitro benzenesulphonyl) - 5 - oxopyrrol-
1
idine-2-carboxilic acid 5c. H NMR (200 MHz, DMSO-
2-(20-Methyl-50-nitro benzenesulphonyl) glutamic acid 4b.
IR (KBr, cmÀ1): 3531, 3366, 3031 (Ar–C–H str), 2871
(ali C–H str), 1679 (C¼O str), 1515 (N¼O str of Ar–
NO2), 1337, 1191 (S¼O str of SO2NH), 914, 792 and
733 (Ar–C–H def), 626. Anal. C12H14N2O8S1 (C, H, N)
calcd: 41.62, 4.05, 8.09;found: 41.72, 4.18, 8.21.
d6): d 8.58 (d, 1H, H-20), 8.28 (dd, 1H, H-60), 7.55 (d,
1H, H-50), 4.92 (m, 1H, H-5), 2.65 (s, 3H, Ar–CH3), 2.50
(m, 2H, H2-4), 2.18 (m, 2H, HA-3,), 1.25 (m, 1H, HB-3).
IR (KBr, cmÀ1): 3191, 3031 (Ar–C–H str), 2866 (ali C–
H str), 1743, 1694 (C¼O str), 1517 (N¼O str of Ar–
NO2), 1341 and 1165 (S¼O str of SO2NH), 965, 891,
750 and 708 (Ar–C–H def), 659. Anal. C12H12N2O7S1 (C,
H, N) calcd: 43.90, 3.66, 8.54;found: 43.43, 3.72, 8.56.
2-(40-Methyl-30-nitro benzenesulphonyl) glutamic acid 4c.
1H NMR (200 MHz, DMSO-d6): d 8.42 (d, 1H, H-20),
8.05 (m, 1H, SO2NH), 7.96 (dd, 1H, H-60), 7.53 (d, 1H,
H-50), 3.88 (m, 1H, H-2), 2.58 (s, 3H, Ar–CH3), 2.30 (m,
1-(Benzenesulphonyl)-5-oxo pyrrolidine-2-carboxilic acid
5e. IR (KBr, cmÀ1): 3031 (Ar–C–H str), 2897 (ali C–H

2126
K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
str.), 1736 (C¼O str), 1681, 1355, 1330 and 1167 (S¼O
str of SO2NH), 1117, 952, 870, 750 and 721 (Ar–C–H
def). Anal. C11H11N1O5S1 (C, H, N) calcd: 49.07, 4.09,
5.20;found: 49.12, 4.21, 5.41.
7.49 (d, 1H, J=8.34, H-30), 6.54 (m, 2H, CONH2), 3.86
(m, 1H, H-2), 2.80 (s, 3H, Ar–CH3), 2.39 (m, 2H, H2-4),
2.10 (m, 2H, HA-3, HB-3). IR (KBr, cmÀ1): 3356, 3150
(N–H str of CONH), 3057 (Ar–C–H str), 1673 (C¼O
str), 1624, 1523 (N¼O str of Ar–NO2), 1435 (ali C–H
def), 1340 and 1155 (S¼O str of SO2NH), 1113, 916, 865
(C–N str of Ar–NO2), 795 and 733 (Ar–C–H def). Anal.
C16H24N2O5S1 (C, H, N) calcd: 53.93, 6.74, 7.86;found:
53.62, 6.71, 7.41.
Method 4. 5-N-Substituted-2-(substituted benzenesulph-
onyl) glutamines 6–41. In a 50-mL of loosely stoppered
conical flask, 1-(substituted benzenesulphonyl)-5-oxo-
pyrrolidine-2-carboxylic acid (0.1 mol) was suspended
in 20 mL of water. To this excess of amines (0.025 mol)
were added and allowed to stand overnight with con-
tinuous stirring. The reaction mixture was concentrated
over a steam bath to remove excess of amines. Then it
was cooled to room temperature and chilled in an ice
bath. The mixture was then acidified with 6 N hydro-
chloric acid to eliminate any traces of unreacted amine.
It was then filtered and the residue was washed many
times with cold water and finally recrystallized with
dilute ethanol.
5-N-Methyl-2-(20-methyl-50-nitro benzenesulphonyl) glu-
1
tamine 10. MS (FAB): M+H+ peak at m/z 360. H
NMR (200 MHz, CDCl3): d 8.78 (d, 1H, J=2.4, H-60),
8.24 (dd, 1H, J1=2.4, J2=8.30, H-40), 7.66 (d, 1H, J=
8.58, SO2NH), 7.50 (d, 1H, J=8.30, H-30), 6.83 (m, 1H,
CONH), 3.86 (m, 1H, H-2), 2.80 (s, 3H, Ar–CH3), 2.28
(m, 2H, H2-4), 1.94 (m, 2H, HA-3, HB-3), 1.43 (m, 3H,
N-CH3). IR (KBr, cmÀ1): 3301 (N–H str of CONH),
3044 (Ar–C–H str), 2920, 2888 (ali C–H str), 1691
(C¼O str), 1634, 1511 (N¼O str of Ar–NO2 ), 1437 (ali
C–H def), 1339 and 1154 (S¼O str of SO2NH), 1116,
792 and 737 (Ar–C–H def). Anal. C12H15N3O7S1 (C, H,
N) calcd: 41.74, 4.35, 12.17;found: 41.73, 4.36, 12.21.
5-N-i-Butyl-2-(benzenesulphonyl) glutamine 6. MS (FAB):
M+H+ peak at m/z 343. 1H NMR (200 MHz, CDCl3):
d 7.82 (m, 2H, H-20, H-60), 7.51 (m, 3H, H-30, H-40, H-
50), 7.24 (m, 1H, SO2NH), 5.90 (m, 1H, CONH), 3.90
(m, 1H, H-2), 3.11 (m, 2H, N–CH2-100), 1.95–1.65 (m,
4H, H2–4, H2-3), 1.20 (m, 1H, CH-200), 0.93 (m, 6H,
CH3-300, CH3-400). IR (KBr, cmÀ1): 3295, 3171 (N–H str
of CONH), 2903, 2824 (ali C–H str), 1682, 1585, 1555,
1444 (ali C–H def), 1321 and 1155 (S¼O str of SO2NH),
887, 752 and 728 (Ar C–H def), 683. Anal. C15H22
N2O5S1 (C, H, N) calcd: 52.63, 6.43, 8.18;found: 52.54,
6.42, 8.53.
5-N-Ethyl-2-(20-methyl-50-nitro benzenesulphonyl) gluta-
mine 11. MS (FAB): M+H+ peak at m/z 374. 1H
NMR (200 MHz, CDCl3): d 8.76 (d, 1H, J=2.4, H-60),
8.25 (dd, 1H, J1=2.46, J2=8.34, H-40), 7.68 (d, 1H,
J=8.58, SO2NH), 7.49 (d, 1H, J=8.34, H-30), 6.84 (m,
1H, CONH), 3.88 (m, 1H, H-2), 3.23 (m, 2H, N–CH2-
100), 2.80 (s, 3H, Ar–CH3), 2.34 (m, 2H, H2-4), 2.08 (m,
2H, HA-3, HB-3), 1.13 (m, 3H, CH3-200). IR (KBr,
cmÀ1): 3315, 3160 (N–H str of CONH), 3067 (Ar–C–H
str), 2887, 2825 (ali C–H str.), 1681 (C¼O str), 1594,
1542, 1518 (N¼O str of Ar–NO2), 1422 (ali C–H def.),
1342 and 1152 (S¼O str of SO2NH), 967, 891 (C–N str
of Ar–NO2), 796 and 735 (Ar–C–H def), 633. Anal.
C13H17N3O7S1 (C, H, N) calcd: 43.45, 4.73, 11.70;
found: 43.39, 4.68, 11.71.
5-N-i-Propyl-2-(40-methyl benzenesulphonyl) glutamine 7.
MS (FAB): M+H+ peak at m/z 343. 1H NMR
(200 MHz, CDCl3): d 7.71 (m, 2H, H-20, H-60), 7.30 (m,
2H, H-30, H-50), 7.14–6.87 (m, 2H, SO2NH, CONH),
3.78 (m, 1H, H-2), 2.40 (s, 3H, Ar–CH3), 2.23 (m, 2H,
H2-4), 2.38–1.72 (m, 3H, HA-3, HB-3, CH-100), 0.92 (m,
6H, CH3-200, CH3-300). IR (KBr, cmÀ1): 3298, 3186 (N–
H str of CONH), 2921, 2875 (ali C–H str), 1677 (C¼O
str), 1583, 1540, 1443 (ali C–H def), 1420, 1321 and
1153 (S¼O str of SO2NH), 811, 687, 661. Anal.
C13H18N2O5S1 (C, H, N) calcd: 49.68, 5.73, 8.92;found:
49.72, 5.78, 9.52.
5-N-n-Propyl-2-(20-methyl-50-nitro benzenesulphonyl) glu-
1
tamine 12. MS (FAB): M+H+ peak at m/z 388. H
NMR (200 MHz, CDCl3): d 8.77 (d, 1H, J=2.4, H-60),
8.25 (dd, 1H, J1=2.45, J2=8.33, H-40), 7.48 (d, 1H, J=
8.38, H-30), 7.37 (m, 1H, SO2NH), 6.58 (m, 1H,
CONH), 3.89 (m, 1H, H-2), 3.17 (m, 2H, N–CH2-100),
2.81 (s, 3H, Ar–CH3), 2.36 (m, 2H, H2-4), 2.08 (m, 2H,
HA-3, HB-3 ), 1.52 (m, 2H, CH2-200), 0.92 (m, 3H, CH3-
300). Signal for SO2NH appears to have merged in the
solvent signal at 7.36. IR (KBr, cmÀ1): 3316, 3147 (N–H
str of CONH), 3055 (Ar–C–H str), 2910, 2886, 2827 (ali
C–H str), 1674 (C¼O str), 1586, 1567, 1549, 1509 (N¼O
str of Ar–NO2), 1452 (ali C–H def), 1342 and 1160 (S¼O
str of SO2NH), 1114, 913, 887 (C–N str of Ar–NO2), 795
and 735 (Ar–C–H def). Anal. C14H19N3O7S1 (C, H, N)
calcd: 45.04, 5.09, 11.26;found: 45.21, 5.17, 11.34.
5-N-i-Butyl-2-(40-methyl benzenesulphonyl) glutamine 8.
MS (FAB): M+H+ peak at m/z 357. 1H NMR
(200 MHz, CDCl3): d 7.71 (m, 2H, H-20, H-60), 7.27 (m,
2H, H-30, H-50), 7.14–6.87 (m, 2H, SO2NH, CONH),
3.80 (m, 1H, H-2), 2.98 (m, 2H, N–CH2-100), 2.40 (s, 3H,
Ar–CH3), 2.25 (m, 2H, H2-4), 2.21–1.68 (m, 3H, HA-3,
HB-3, CH-200), 0.89 (m, 6H, CH3-300, CH3-400). IR (KBr,
cmÀ1): 3304, 3197 (N–H str of CONH), 2895, 2868 (ali
C–H str), 1702 (C¼O str), 1588, 1555, 1442 (ali C–H
def), 1327 and 1154 (S¼O str of SO2NH), 973, 808, 691.
Anal. C15H22N2O5S1 (C, H, N) calcd: 52.63, 6.43, 8.18;
found: 52.52, 6.26, 8.08.
5-N-n-Butyl-2-(20-methyl-50-nitro benzenesulphonyl) glu-
tamine 13. MS (FAB):M+H+ peak at m/z 402. 1H
NMR (200 MHz, CDCl3): d 8.74 (d, 1H, J=2.34, H-60),
8.21 (dd, 1H, J1=2.38, J2=8.33, H-40), 7.42 (d, 1H,
J=8.33, H-30), 7.34 (m, 1H, SO2NH), 6.54 (m, 1H,
CONH), 3.90 (m, 1H, H-2), 3.15 (m, 2H, N-CH2-100),
2-(20-Methyl-50-nitro benzenesulphonyl) glutamine 9. MS
1
(FAB): M+H+ peak at m/z 346. H NMR (200MHz,
CDCl3): d 8.74 (d, 1H, J=2.3, H-60), 8.27 (dd, 1H,
J1=2.34, J2=8.34, H-40), 7.67 (d, 1H, J=8.58, SO2NH),

K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
2127
2.81 (s, 3H, Ar–CH3), 2.36 (m, 2H, H2-4), 1.98 (m, 2H,
HA-3, HB-3), 1.52 (m, 2H, CH2-200), 0.92–0.81 (m, 6H,
CH3-300, CH3-400). IR (KBr, cmÀ1): 3315, 3221 (N–H str
of CONH), 3033 (Ar–C–H str), 2905 (ali C–H str), 1683
( C¼O str), 1548, 1507 (N¼O str of Ar–NO2 ), 1445 (ali
C–H def), 1340 and 1160 (S¼O str of SO2NH), 1116,
792 and 736 (Ar–C–H def ). Anal. C15H21N3O7S1 (C, H,
N) calcd: 46.51, 5.43, 10.85;found: 46.52, 5.44, 10.96.
str), 1687 (C¼O str), 1590, 1531 (N¼O str of Ar–NO2),
1431 (ali C–H def.), 1339 and 1158 (S¼O str of
SO2NH), 902, 754 and 739 (Ar–C–H def), 689. Anal.
C18H25N3O7S1 (C, H, N) calcd: 50.58, 5.85, 9.84;found:
50.56, 5.64, 9.83.
5-N-benzyl-2-(20-methyl-50-nitro benzenesulphonyl) gluta-
mine 18. MS (FAB): M+H+ peak at m/z 436. 1H
NMR (300 MHz, DMSO-d6): d 8.63 (s, 1H, SO2NH),
8.54 (d, 1H, J=2.34, H-60), 8.34 (dd, 1H, J1=2.42, J2=
8.33, H-40), 8.30 (m, 1H, CONH), 7.67 (d, 1H, J=8.42,
H-30), 7.33–7.20 (m, 5H, H5-ph), 4.21 (m, 2H, CH2–Ph),
3.77 (m, 1H, H-2), 2.72 (s, 3H, Ar–CH3), 2.20 (m, 2H,
H2–4), 1.94 (m, 1H, HA-3), 1.74 (m, 1H, HB-3). IR
(KBr, cmÀ1): 3314, 3222 (N–H str of CONH), 3050
(Ar–C–H str), 2874 (ali C–H str), 1682 (C¼O str),
1587,1504 (N¼O str of Ar–NO2,), 1444 (ali C–H def),
1338 and 1159 (S¼O str of SO2NH), 1114, 887 (C–N str
of Ar–NO2), 794 and 736 (Ar–C–H def), 697. Anal.
C18H19N3O7S1 (C, H, N) calcd: 51.31, 4.51, 9.98;found:
51.21, 4.34, 9.78.
5-N-i-Propyl-2-(20-methyl-50-nitro benzenesulphonyl) glu-
1
tamine 14. MS (FAB): M+H+ peak at m/z 388. H
NMR (200 MHz, CDCl3): d 8.76 (d, 1H, J=2.34, H-60),
8.24 (dd, 1H, J1=2.30, J2=8.30, H-40), 7.83 (d, 1H,
J=7.9, SO2NH), 7.51 (m, 1H, H-30 merged with CHCl3
peak of CDCl3), 6.69 (d, 1H, CONH), 4.01–3.86 (m,
2H, H-2, CH-100), 2.80 (s, 3H, Ar–CH3), 2.31 (m, 2H,
H2-4), 2.11–1.99 (m, 2H, HA-3, HB-3), 1.17–0.97 (m,
6H, CH3-200, CH3-300). IR (KBr, cmÀ1): 3311, 3230 (N–
H str of CONH), 2919, 2877 (ali C–H str.), 1674, 1630,
1538, 1511 (N¼O str of Ar–NO2), 1450 (ali C–H def.),
1339 and 1157 (S¼O str of SO2NH), 1117, 911, 796 and
737(Ar–C–H def). Anal. C16H23N3O7S1 (C, H, N) calcd:
47.88, 5.73, 10.47;found: 47.42, 5.43, 10.76.
5-N-n-Pentyl-2-(20-methyl-50-nitro benzenesulphonyl) glu-
1
tamine 19. MS (FAB): M+H+ peak at m/z 416. H
5-N-i-Butyl-2-(20-methyl-50-nitro benzenesulphonyl) glu-
NMR (300 MHz, DMSO-d6): d 8.63 (d, 1H, J=6.32,
SO2NH), 8.52 (d, 1H, J=2.38, H-60), 8.34 (dd, 1H,
J1=2.39, J2=8.34, H-40), 7.73 (m, 1H, CONH), 7.67 (d,
1H, J=8.42, H-30), 3.73 (m, 1H, H-2), 2.95 (m, 2H, N-
CH2-100), 2.71 (s, 3H, Ar–CH3), 2.08 (m, 2H, H2-4), 1.89
(m, 1H, HA-3 ), 1.69 (m, 1H, HB-3), 1.29 (m, 6H, CH2-
200,CH2-300, CH2-400), 0.85 (m, 3H, CH3-500). IR (KBr,
cmÀ1): 3320, 3227 (N–H str of CONH), 3041 (Ar–C–H
str), 2871 & 2809 (ali C–H str), 1684 (C¼O str), 1549,
1505 (N¼O str of Ar–NO2), 1442 (ali C–H def), 1340
and 1157 (S¼O str of SO2NH), 1097, 1051, 914, 793 and
737 (Ar–C–H def), 661. Anal. C19H21N3O7S1 (C, H, N)
calcd: 52.41, 4.83, 9.65;found: 52.39, 4.98, 9.76.
1
tamine 15. MS (FAB): M+H+ peak at m/z 402. H
NMR (300 MHz, CDCl3): d 8.75 (d, 1H, J=2.2, H-60),
8.29 (dd, 1H, J1=2.2, J2=8.32, H-40), 7.51 (d, 1H,
J=8.36, H-30), 6.07 (m, 1H, CONH), 5.99 (m, 1H,
SO2NH), 3.81 (m, 1H, H-2), 3.13 (m, 2H, N–CH2-100),
2.79 (s, 3H, Ar–CH3), 2.50 (m, 2H, H2-4), 2.13 (m, 2H,
HA-3, HB-3), 1.21 (m, 1H, CH-200), 0.94 (m, 6H, CH3-300,
CH3-400). IR (KBr, cmÀ1): 3316, 3160 (N–H str of
CONH), 3033 (Ar–C–H str), 2909, 2878, 2824 (ali C–H
str), 1675 (C¼O str), 1584, 1566, 1509 (N¼O str of Ar–
NO2), 1452 (ali C–H def), 1339 and 1158 (S¼O str of
SO2NH), 1114, 886 (C–N str. of Ar–NO2), 796 and 737
(Ar–C–H def), 633. Anal. C15H21N3O7S1 (C, H, N)
calcd: 46.51, 5.43, 10.85;found: 46.62, 5.76, 10.58.
5-N-n-Hexyl-2-(20-methyl-50-nitro benzenesulphonyl) glu-
1
tamine 20. MS (FAB): M+H+ peak at m/z 430. H
5-N-Cyclohexyl-2-(20-methyl-50-nitro benzenesulphonyl)
NMR (300 MHz, DMSO-d6): d 8.63 (m, 1H, SO2NH),
8.52 (d, 1H, J=2.44, H-60), 8.34 (dd, 1H, J1=2.49,
J2=8.35, H-40), 7.73 (m, 1H, CONH), 7.67 (d, 1H,
J=8.47, H-30), 3.74 (m, 1H, H-2), 2.96 (m, 2H, N–CH2-
100), 2.71 (s, 3H, Ar–CH3), 2.15–2.03 (m, 2H, H2-4),
1.95–1.87 (m, 1H, HA-3), 1.75–1.65 (m, 1H, HB-3) 1.38–
1.14 (m, 8H, CH2-200, CH2-300, CH2-400, CH2-500), 0.85
(m, 3H, CH3-600). IR (KBr, cmÀ1): 3325, 3227 (N–H str
of CONH), 3052 (Ar–C–H str), 2907, 2879, 2813 (ali C–
H str), 1687 (C¼O str), 1583, 1567, 1548, 1509 (N¼O str
of Ar–NO2), 1445 (ali C–H def), 1341 and 1161 (S¼O
str of SO2NH), 884 (C–N str of Ar–NO2), 794 and 736
(Ar–C–H def), 662. Anal. C17H25N3O7S1 (C, H, N)
calcd: 49.16, 6.02, 10.12;found: 59.34, 6.21, 10.32.
1
glutamine 16. MS (FAB): M+H+ peak at m/z 328. H
NMR (200 MHz, CDCl3): d 8.70 (m, 1H, H-60), 8.28–
8.23 (m, 2H, H-40, H-30), 7.53 (m, 1H, SO2NH), 7.21 (m,
1H, CONH), 3.79 (m, 1H, H-2), 2.79 (s, 3H, Ar–CH3),
2.57 (m, 2H, H2-4), 2.23 (m, 2H, H2-3), 1.94–1.67 and
1.34–1.11 (m, 11H, cyclohexyl protons). IR (KBr,
cmÀ1): 3320, 3176 (N–H str of CONH), 3046 (Ar–C–H
str), 2882, 2809 (ali C–H str.), 1678, 1620, 1588, 1540,
1511 (N¼O str of Ar–NO2), 1441 (ali C–H def), 1340
and 1157 (S¼O str of SO2NH), 1115, 914, 887 (C–N str
of Ar–NO2), 795, 736 (Ar–C–H def). Anal. C16H23
N3O7S1 (C, H, N) calcd: 47.88, 5.73, 10.47;found:
48.32, 5.50, 10.73.
5-N-Phenyl 2-(20-methyl 50-nitro benzenesulphonyl) gluta-
mine 17. MS (FAB): M+H+ peak at m/z 422. 1H NMR
(300 MHz, DMSO-d6): d 8.60 (s, 1H, SO2NH), 8.53 (d,
1H, H-60), 8.32 (dd, 1H, H-40), 8.27 (m, 1H, CONH),
7.62 (d, 1H, H-30), 7.36–7.25 (m, 5H, H5-ph), 3.82 (m,
1H, H-2), 2.72 (s, 3H, Ar–CH3), 2.20 (m, 2H, H2-4),
1.90 (m, 1H, HA-3), 1.71 (m, 1H, HB-3). IR (KBr,
cmÀ1): 3295, 3206 (N–H str of CONH), 3025 (Ar–C–H
2-(40-Methyl-30-nitro benzenesulphonyl) glutamine 21. MS
1
(FAB): M+H+ peak at m/z 346. H NMR (300 MHz,
DMSO-d6): d 8.47 (d, 1H, J=8.86, SO2NH), 8.28 (d,
1H, J=2.11, H-20), 7.99 (dd, 1H, J1=2.09, J2=8.07, H-
60), 7.70 (d, 1H, J=8.07, H-50), 7.44 (m, 2H, CONH2),
3.76 (m, 1H, H-2), 2.59 (s, 3H, Ar–CH3), 2.11 (m, 2H,
H2-4), 1.90 (m, 1H, HA-3), 1.71 (m, 1H, HB-3). IR (KBr,
cmÀ1): 3375, 3283, 3196 (N–H str of CONH), 3036 (Ar–

2128
K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
C–H str), 1705 (C¼O str), 1658, 1580, 1511 (N¼O str of
Ar–NO2), 1339 and 1162 (S¼O str of SO2NH), 1102,
969, 878 (C–N str of Ar–NO2), 787, 757, 707 (Ar–C–H
def), 672. Anal. C18H27N3O7S1 (C, H, N) calcd: 50.35,
6.29, 9.79;found: 49.46, 6.00, 10.18.
3188 (N–H str of CONH), 3026 (Ar–C–H str), 2882,
2825 (ali C–H str), 1695 (C¼O str), 1558, 1517 (N¼O
str of Ar–NO2), 1443 (ali C–H def), 1333 and 1162
(S¼O str of SO2NH), 973, 880 (C–N str of Ar–NO2),
798 and 754 (Ar–C–H def ). Anal. C15H21N3O7S1 (C, H,
N) calcd: 46.51, 5.43, 10.85;found: 46.34, 5.11, 10.90.
5-N-Methyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
tamine 22. MS (FAB): M+H+ peak at m/z 360. H
5-N-n-Pentyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
1
1
NMR (300 MHz, DMSO-d6): d 12.72 (s, 1H, COOH),
8.47 (d, 1H, J=8.87, SO2NH), 8.30 (d, 1H, J=1.81, H-
20), 7.96 (dd, 1H, J1=1.81, J2=8.07, H-60), 7.70 (d, 1H,
J=8.14, H-50), 7.68 (m, 1H, CONH), 3.80 (m, 1H, H-2),
2.59 (s, 3H, Ar–CH3), 2.51 (m, 3H, N-CH3), 2.08 (m,
2H, H2-4), 1.88 (m, 1H, HA-3), 1.67 (m, 1H, HB-3). IR
(KBr, cmÀ1): 3319, 3181 (N–H str of CONH), 3025
(Ar–C–H str), 2887, 2819 (ali C–H str), 1690 (C¼O str),
1573, 1517 (N¼O str of Ar–NO2, asymmetric) 1438 (ali
C–H def), 1394, 1333 and 1164 (S¼O str of SO2NH),
970, 904, 880 (C–N str of Ar-NO2), 798 and 755 (Ar–C–
H def). Anal. C12H15N3O7S1 (C, H, N) calcd: 41.74,
4.85, 12.17;found: 41.56, 4.24, 12.24.
tamine 26. MS (FAB): M+H+ peak at m/z 416. H
NMR (200 MHz, DMSO-d6): d 8.42 (m, 1H, SO2NH),
7.96 (d, 1H, H-20), 7.74 (dd, 1H, H-60), 7.52–7.38 (m,
2H, H-50, CONH), 3.85 (m, 1H, H-2), 3.16 (m, 2H, N–
CH2-100), 2.56 (s, 3H, Ar–CH3), 2.28 (m, 2H, H2-4), 2.08
(m, 1H, HA-3), 1.92 (m, 1H, HB-3), 1.50–1.20 (m, 6H,
CH2-200, CH2-300, CH2-400), 0.89 (m, 3H, CH3-50). IR
(KBr, cmÀ1): 3313, 3191 (N–H str of CONH), 3022
(Ar–C–H str), 2879, 2813 (ali C–H str.), 1693 (C¼O
str), 1572, 1519 (N¼O str of Ar–NO2), 1442 (ali C–H
def.), 1332 and 1164 (S¼O str of SO2NH), 977, 897, 880
(C–N str of Ar–NO2), 798, 753 (Ar–C–H def), 662.
Anal. C16H23N3O7S1 (C, H, N) calcd: 47.88, 5.73, 10.47;
found: 47.99, 5.62, 10.12.
5-N-Ethyl-2-(40-methyl-30-nitro benzenesulphonyl) gluta-
mine 23. MS(FAB): M+H+ peak at m/z 374. 1H
NMR (300 MHz, DMSO-d6): d 12.73 (s, 1H, COOH),
8.47 (d, 1H, J=8.82, SO2NH), 8.31 (d, 1H, J=1.74, H-
20), 7.96 (dd, 1H, J1=1.92, J2=8.1, H-60), 7.75 (m, 1H,
CONH), 7.71 (d, 1H, J=8.16, H-50), 3.80 (m, 1H, H-2),
3.01 (m, 2H, N–CH2-100), 2.59 (s, 3H, Ar–CH3), 2.09 (m,
2H, H2-4), 1.89 (m, 1H, HA-3), 1.67 (m, 1H, HB-3), 0.97
(m, 3H, CH3-200). IR (KBr, cmÀ1): 3310, 3188 (N–H str
of CONH), 3033 (Ar–C–H str), 2885, 2831 (ali C–H
str), 1692 (C¼O str), 1565, 1518 (N¼O str of Ar–NO2)
1436 (ali C–H def), 1333 and 1163 (S¼O str of SO2NH),
973, 879 (C–N str of Ar–NO2), 796 and 754 (Ar–C–H
def), 662. Anal. C13H17N3O7S1 (C, H, N) calcd: 43.54,
4.73, 11.70;found: 43.42, 4.45, 11.70.
5-N-n-Hexyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
1
tamine 27. MS (FAB): M+H+ peak at m/z 430. H
NMR (200 MHz, DMSO-d6): d 8.40 (m, 1H, SO2NH),
7.95 (d, 1H, H-20), 7.70 (dd, 1H, H-60), 7.50–7.40 (m,
2H, H-50, CONH), 3.83 (m, 1H, H-2), 3.14 (m, 2H, N–
CH2-100), 2.56 (s, 3H, Ar–CH3), 2.28 (m, 2H, H2-4), 2.06
(m, 1H, HA-3), 1.92 (m, 1H, HB-3), 1.50–1.11 (m, 8H,
CH2-200, CH2-300, CH2-400, CH2-500), 0.84 (m, 3H, CH3-
600). IR (KBr, cmÀ1): 3308, 3189 (N–H str of CONH),
3023 (Ar–C–H str), 2879, 2812 (ali C–H str), 1694
(C¼O str), 1557, 1518 (N¼O str of Ar–NO2), 1444 (ali
C–H def), 1331 and 1165 (S¼O str of SO2NH), 971, 898
(C–N str of Ar–NO2), 832, 799 and 717 (Ar–C–H def),
662. Anal. C17H25N3O7S1 (C, H, N) calcd: 49.16, 6.02,
10.12;found: 49.02, 5.94, 10.34.
5-N-n-Propyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
tamine 24. MS (FAB): M+H+ peak at m/z 388. H
5-N-i-Propyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
1
1
NMR (300 MHz, DMSO-d6): d 12.72 (s, 1H, COOH),
8.47 (d, 1H, J=8.85, SO2NH), 8.31 (d, 1H, J=1.77, H-
20), 7.96 (dd, 1H, J1=1.83, J2=8.07, H-60), 7.75 (m, 1H,
CONH), 7.71 (d, 1H, J=8.19, H-50), 3.80 (m, 1H, H-2),
2.94 (m, 2H, N–CH2-10), 2.59 (s, 3H, Ar–CH3), 2.11 (m,
2H, H2-4), 1.89 (m, 1H, HA-3), 1.68 (m, 1H, HB-3), 1.36
(m, 2H, CH2-200), 0.81 (m, 3H, CH3-300). IR (KBr,
cmÀ1): 3311, 3188 (N–H str of CONH), 3027 (Ar–C–H
str), 2886, 2829 (ali C–H str), 1694 (C¼O str), 1563,
1519 (N¼O str of Ar–NO2) 1441 (ali C–H def), 1334
and 1164 (S¼O str of SO2NH), 972, 896, 882 (C–N str
of Ar–NO2), 797 and 753 (Ar–C–H def), 663. anal. C14
H19N3O7S1 (C, H, N) calcd: 45.04, 5.09, 11.26;found:
45.14, 4.82, 11.31.
tamine 28. MS (FAB): M+H+ peak at m/z 388. H
NMR (300 MHz, DMSO-d6): 8.44 (d, 1H, J=8.70,
SO2NH), 8.30 (d, 1H, J=1.90, H-20), 7.94 (dd, 1H,
J1=1.91, J2=8.10, H-60), 7.70 (d, 1H, J=8.10, H-50),
7.64 (m, 1H, CONH), 3.82 (m, 1H, H-2), 2.92 (m, 1H,
N–CH-100), 2.59 (s, 3H, Ar–CH3), 2.10 (m, 2H, H2-4),
1.87 (m, 1H, HA-3), 1.71 (m, 1H, HB-3), 1.06–0.91 (m,
6H, CH3-200, CH3-300). IR (KBr, cmÀ1): 3296, 3198 (N–
H str of CONH), 3024 (Ar–C–H str), 2921, 2882 (ali C–
H str), 1699 (C¼O str), 1573, 1549, 1519 (N¼O str of
Ar–NO2), 1436 (ali C–H def), 1334 & 1164 (S¼O str of
SO2NH), 975, 898 (C–N str of Ar–NO2), 757 and 723
(Ar–C–H def), 675, 662. Anal. C18H27N3O7S1 (C, H, N)
calcd: 50.35, 6.29, 9.79;found: 50.32, 6.34, 10.02.
5-N-n-Butyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
5-N-i-Butyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
1
1
tamine 25. MS (FAB): M+H+ peak at m/z 402. H
tamine 29. MS (FAB): M+H+ peak at m/z 402. H
NMR (200 MHz, DMSO-d6): d 8.30 (m, 2H, H-20,
SO2NH), 7.96 (dd, 1H, H-60), 7.73 (m, 2H, H-50 CONH-
5), 3.82 (m, 1H, H-2), 3.00 (m, 2H, N-CH2-100), 2.56 (s,
3H, Ar–CH3), 2.11 (m, 2H, H2-4), 1.88 (m, 1H, HA-3),
1.70 (m, 1H, HB-3), 1.35 (m, 2H, CH-200), 1.25 (m, 2H,
CH2-300), 0.85 (m, 3H, CH3-400). IR (KBr, cmÀ1): 3309,
NMR (300 MHz, DMSO-d6): d 12.72 (s, 1H, COOH),
8.47 (d, 1H, J=8.73, SO2NH), 8.30 (d, 1H, J=1.84, H-
20), 7.96 (dd, 1H, J1=1.90, J2=8.07, H-60), 7.77 (m, 1H,
CONH), 7.70 (d, 1H, J=8.16, H-50), 3.80 (m, 1H, H-2),
2.81 (m, 2H, N–CH2-100), 2.59 (s, 3H, Ar–CH3), 2.12 (m,
2H, H2-4), 1.89 (m, 1H, HA-3), 1.70 (m, 1H, HB-3), 1.62

K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
2129
(m, 1H, CH-200), 0.80 (m, 6H, CH3-300, CH3-400). IR
(KBr, cmÀ1): 3311, 3198 (N–H str of CONH), 3035
(Ar–C–H str), 2880, 2822 (ali C–H str), 1697 (C¼O str),
1581, 1522 (N¼O str of Ar–NO2), 1434 (ali C–H def),
1332 and 1165 (S¼O str of SO2NH), 897, 881 (C–N str
of Ar–NO2), 796 and 756 (Ar–C–H def), 661. Anal.
C15H21N3O7S1 (C, H, N) calcd: 46.51, 5.43, 10.85;
found: 46.49, 5.42, 10.39.
and 1151 (S¼O str of SO2NH), 827, 784 and 724 (Ar C–
H def), 690, 652. Anal. C18H19N3O7S1 (C, H, N) calcd:
51.31, 4.51, 9.98;found: 51.22, 4.34, 9.98.
5-N-Ethyl-2-(40 -ethyl benzenesulphonyl) glutamine 34.
MS (FAB): M+H+ peak at m/z 343. 1H NMR
(200 MHz, CDCl3): d 7.70 (m, 2H, H-20, H-60), 7.32 (m,
2H, H-30, H-50), 6.19 (m, 1H, SO2NH), 5.80 (d, 1H,
CONH), 3.80 (m, 1H, H-2), 3.20 (m, 2H, N-CH2-100),
2.71 (m, 2H, CH2 of C2H5ph), 2.50–2.35 (m, 2H, H2-3),
2.15–2.10 (m, 2H, H2-4), 1.28 (t, 3H, CH3 of C2H5ph),
1.00 (t, 3H, CH3-200). IR (KBr, cmÀ1): 3296, 3197 (N–H
str of CONH), 2918, 2877 (ali C–H str), 1712 (C¼O str),
1582, 1520, 1447 (ali C–H def), 1327 and 1156 (S¼O str
of SO2NH), 1087, 966, 831, 783 (Ar C—H def), 679,
653. Anal. C14H20N2O5S1 (C, H, N) calcd: 51.22, 6.10,
8.54;found: 51.11, 6.21, 8.37.
5-N-Cyclohexyl-2-(40-methyl-30-nitro benzenesulphonyl)
1
glutamine 30. MS (FAB):M+H+ peak at m/z 428. H
NMR (300 MHz, DMSO-d6): d 12.70 (s, 1H, COOH),
8.46 (d, 1H, J=8.62, SO2NH), 8.30 (d, 1H, J=1.55, H-
20), 7.96 (dd, 1H, J1=1.62, J2=8.09, H-60), 7.71 (d, 1H,
J=8.15, H-50), 7.66 (m, 1H, CONH), 3.79 (m, 1H, H-2),
3.43 (m, 1H, N–CH2-10), 2.59 (s, 3H, Ar–CH3), 2.09 (m,
2H, H2-4), 1.88 (m, 1H, HA-3), 1.67–1.52 (m, 5H, HB-3,
CH-20, CH2-600), 1.37–1.03 (m, 6H, CH2-300, CH2-400,
CH2-500). IR (KBr, cmÀ1): 3297, 3206 (N–H str of
CONH), 3032 (Ar–C–H str), 2878, 2807 (ali C–H str),
1702 (C¼O str), 1576, 1545, 1519 (N¼O str of Ar–
NO2), 1437 (ali C–H def), 1334 and 1164 (S¼O str of
SO2NH), 989, 879 (C–N str of Ar–NO2), 797 and 754
(Ar–C–H def), 662. Anal. C16H23N3O7S1 (C, H, N)
calcd: 47.88, 5.73, 10.47;found: 47.79, 5.74, 10.46.
5-N-n-Propyl-2-(40-ethyl benzenesulphonyl) glutamine 35.
MS(FAB): M+H+ peak at m/z 357. 1H NMR
(200 MHz, CDCl3): d 7.72 (m, 2H, H-20, H-60), 7.30 (m,
2H, H-30, H-50), 6.17 (m, 1H, SO2NH), 5.83 (d, 1H,
CONH), 3.82 (m, 1H, H-2), 3.23 (m, 2H, N–CH2-100),
2.73 (m, 2H, CH2 of C2H5ph), 2.65–2.31 (m, 2H, H2-3),
2.15–2.05 (m, 2H, H2-4), 1.60–1.49 (m, 2H, CH2-200),
1.26 (t, 3H, CH3 of C2H5ph), 0.93 (t, 3H, CH3-300). IR
(KBr, cmÀ1): 3311, 3191 (N–H str of CONH), 2995,
2907, 2878 (ali C–H str), 1697 (C¼O str), 1585, 1555,
1442 (ali C–H def), 1328 1156 (S¼O str of SO2NH), 784
and 700 (Ar C–H def), 661. Anal. C15H22N2O5S1 (C, H,
N) calcd: 52.63, 6.43, 8.18;found: 52.59, 6.63, 6.78.
5-N-Benzyl-2-(40-methyl-30-nitro benzenesulphonyl) gluta-
mine 31. MS (FAB): M+H+ peak at m/z 436. 1H NMR
(200 MHz, DMSO-d6): d 8.45 (m, 1H, SO2NH), 7.95 (d,
1H, H-20), 7.60–7.20 (m, 8H, H-60, H-50, ph. protons
CONH), 4.26 (m, 2H, CH2tÀph), 3.92 (m, 1H, H-2),
2.58 (s, 3H, Ar–CH3), 2.36 (m, 2H, H2-4), 2.16 (m, 1H,
HA-3), 1.99 (m, 1H, HB-3). IR (KBr, cmÀ1): 3301, 3197
(N–H str of CONH), 3014 (Ar–C–H str), 1695 (C¼O
str), 1577, 1559, 1518 (N¼O str of Ar–NO2), 1331 and
1154 (S¼O str of SO2NH), 982, 899, 882 (C–N str of
Ar–NO2), 799 and 737 (Ar–C–H def), 662, 620. Anal.
C18H25N3O7S1 (C, H, N) calcd: 50.58, 5.85, 9.84;found:
50.49, 5.68, 9.90.
5-N-n-Butyl-2-(40-ethyl benzenesulphonyl) glutamine 36.
MS(FAB): M+H+ peak at m/z 371. 1H NMR
(200 MHz, CDCl3): d 8.92 (m, 2H, H-20, H-60), 7.51 (m,
2H, H-30, H-50), 6.29 (m, 2H, SO2NH), 5.88 (d, 1H,
CONH), 3.89 (m, 1H, H-2), 3.46 (m, 2H, N–CH2-100),
2.90 (m, 2H, CH2 of C2H5ph), 2.83–2.23 (m, 4H, H2–4,
H2-3), 1.80–1.39 (m, 7H, CH2-200, CH2-300, CH3 of
C2H5ph), 1.10–0.98 (m, 3H, CH3-400). IR (KBr, cmÀ1):
3306, 3190 (N–H str of CONH), 3000, 2904, 2876 (ali
C–H str), 1696 (C¼O str), 1584, 1553, 1441 (ali C–H
def), 1327 and 1156 (S¼O str of SO2NH), 969, 784 and
704 (Ar C–H def), 662. Anal. C16H24N2O5S1 (C, H, N)
calcd: 53.93, 6.74, 7.86;found: 53.58, 6.71, 7.56.
5-N-Phenyl-2-(40-methyl-30-nitro benzenesulphonyl) glu-
1
tamine 32. MS (FAB): M+H+ peak at m/z 422. H
NMR (200 MHz, DMSO-d6): d 8.43 (m, 1H, SO2NH),
7.98 (d, 1H, H-20), 7.67–7.28 (m, 8H, H-60, H-50, ph.
protons CONH), 3.94 (m, 1H, H-2), 2.58 (s, 3H, Ar–
CH3), 2.39 (m, 2H, H2-4), 2.13 (m, 1H, HA-3), 1.96 (m,
1H, HB-3). IR (KBr, cmÀ1): 3299, 3188 (N–H str of
CONH), 3029 (Ar–C–H str), 1700 (C¼O str), 1581,
1538, 1517 (N¼O str of Ar–NO2), 1433, 1331 and 1155
(S¼O str of SO2NH), 971, 897 (C–N str of Ar–NO2),
751 and 715 (Ar–C–H def), 687, 661. Anal. C19H21
N3O7S1 (C, H, N) calcd: 52.41, 4.83, 9.65;found: 52.51,
4.89, 9.64.
5-N-n-Pentyl-2-(40-ethyl benzenesulphonyl) glutamine 37.
1
MS (FAB): M+H+ peak at 385. H NMR (200 MHz,
CDCl3): d 8.90 (m, 2H, H-20, H-600), 7.46 (m, 2H, H-30,
H-50), 6.31 (m, 2H, SO2NH), 5.90 (d, 1H, CONH), 3.96
(m, 1H, H-2), 3.48 (m, 2H, N–CH2-100), 2.90 (m, 2H,
CH2 of C2H5ph), 2.81–2.11 (m, 4H, H2-4, H2-3), 1.85–
1.35 (m, 9H, CH2-200, CH2-300, CH2-400, CH3 of C2H5ph),
1.15–0.90 (m, 3H, CH3-500). IR (KBr, cmÀ1): 3307, 3190
(N–H str of CONH), 3032 (Ar C–H str), 2902, 2876 (ali
C–H str.), 1696 (C¼O str), 1584, 1554, 1443 (ali C–H
def.), 1329 and 1155 (S¼O str of SO2NH), 784, 704 (Ar
C–H def), 662. Anal. C17H26N2O5S1 (C, H, N) calcd:
55.13, 7.03, 7.57;found: 55.01, 7.21, 7.55.
5-N-Methyl-2-(40-ethyl benzenesulphonyl) glutamine 33.
MS (FAB): M+H+ peak at m/z 329. 1H NMR
(200 MHz, CDCl3): d 7.81 (m, 2H, H-20, H-60), 7.34 (m,
2H, H-30, H-50), 6.19 (m, 1H, SO2NH), 5.98 (d, 1H,
CONH), 3.86 (m, 1H, H-2), 2.73 (m, 2H, CH2 of C2H5ph),
2.60–2.40 (m, 2H, H2-3), 2.20–2.10 (m, 2H, H2-4), 1.49
(m, 3H, N–CH3), 1.26 (t, 3H, CH3 of C2H5ph). IR
(KBr, cmÀ1): 3298, 3168 (N–H str of CONH), 2919,
2883 (ali C–H str), 1676, 1581, 1443 (ali C–H def), 1320
5-N-n-Hexyl-2-(40-ethyl benzenesulphonyl) glutamine 38.
MS (FAB): M+H+ peak at m/z 399. 1H NMR (200 MHz,
CDCl3): d 8.94 (m, 2H, H-20, H-60), 7.51 (m, 2H, H-30,

2130
K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
H-50), 6.35 (m, 2H, SO2NH), 6.02 (d, 1H, CONH), 4.01
(m, 1H, H-2), 3.47 (m, 2H, N–CH2-100), 2.92 (m, 2H,
CH2 of C2H5ph), 2.79–2.31 (m, 4H, H2-4, H2-3), 1.85–
1.42 (m, 8H, CH2-200, CH2-300, CH2-400, CH2-500), 1.33–
1.25 (m, 3H, CH3 of C2H5ph), 0.89 (m, 3H, CH3-600). IR
KBr, cmÀ1): 3309, 3191 (N–H str of CONH), 3005 (Ar
C–H str), 2906, 2876 (ali C–H str), 1696 (C¼O str),
1585, 1555, 1444 (ali C–H def), 1329 and 1156 (S¼O str
of SO2NH), 826, 786, 703 (Ar C–H def), 664. Anal.
C18H28N2O5S1 (C, H, N) calcd: 56.25, 7.29, 7.29;found:
56.32, 7.36, 7.30.
Screening protocol. Two groups of five mice each were
kept in separate cages under identical conditions. One
of these groups was served as control and other as test.
Compound were dissolved or suspended (where and when
necessary with 2% Tween 80) in phosphate buffered saline
(PBS: pH 7.2). EAC cells were collected from the donor
mouse and were suspended in sterile isotonic saline. The
viable EAC cells were counted (Trypan blue indicator)
under the microscope and were adjusted at 10Â106 cells/
mL. 0.1 mL of EAC cells per 10-g body weight of the
animals was injected (ip) on day zero. A day of incu-
bation was allowed for multiplication of the cells. Seven
doses of compound (0.2 mmol/kg, 0.1 mL per 10-g body
weight) were injected ip from the first day up to the
seventh day with 24-h intervals. Control animals
received only vehicle. Food and water were withheld 6 h
before sacrificing the animals. On day eight all the ani-
mals were sacrificed, peritoneal fluid was collected and
the cell count was noted. All the fluid in the peritoneal
cavity was wiped off with absorbent cotton, the weight
of the animals was taken before sacrificing and after
removing the fluid from the peritoneal cavity. The dif-
ference in weight was considered as tumor weight.
Mitomycin-C at a dose level of 1 mg per kg body weight
was used as standard, which showed 100% inhibition.
5-N-i-Propyl-2-(40-ethyl benzenesulphonyl) glutamine 39.
MS (FAB): M+H+ peak at m/z 357. 1H NMR (200MHz,
CDCl3): d 8.03–7.84 (m, 2H, H-20, H-60), 7.65–7.4 (m,
2H, H-30, H-50), 6.18 (m, 1H, SO2NH), 5.95 (d, 1H,
CONH), 4.30 (m, 2H, N–CH), 4.00 (m, 1H, H-2), 2.96
(m, 2H, CH2 of C2H5ph), 2.70–2.20 (m, 4H, H2-4, H2-
3), 1.55–1.00 (m, 9H, CH3-200, CH3-300, CH3 of C2H5ph).
IR (KBr, cmÀ1): 3295, 3196 (N–H str of CONH), 3033
(Ar C–H str), 2915, 2877 (ali C–H str), 1702 (C¼O str),
1582, 1543, 1442 (ali C–H def), 1327 and 1156 (S¼O str
of SO2NH), 825, 784, 724, 687 (Ar C–H def). Anal.
C19H30N2O5S1 (C, H, N) calcd: 57.29, 7.54, 7.03;found:
57.21, 7.61, 7.21.
5-N-Benzyl-2-(40-ethyl benzenesulphonyl) glutamine 40.
QSAR methods
1
MS (FAB): M+H+ peak at m/z 405. H NMR (200
MHz, CDCl3): d 7.70 (m, 2H, H-20, H-60), 7.5–7.15 (m,
7H, H-30, H-50, ph-protons), 6.75 (m, 2H, SO2NH), 5.85
(m, 1H, CONH), 4.45 (m, 2H, N–CH2), 3.85 (m, 1H, H-
2), 2.75 (m, 2H, CH2 of C2H5ph), 2.50–2.10 (m, 4H, H2-
4, H2-3), 1.30 (m, 3H, CH3 of C2H5ph). IR (KBr, cmÀ1):
3296, 3197 (N–H str of CONH), 2912, 2878 (ali C–H
str), 1700 (C¼O str), 1584, 1551, 1434 (ali C–H def),
1327 and 1152 (S¼O str of SO2NH), 981, 783, 719, 690
(Ar C–H def), 660, 618. Anal. C16H24N2O5S1 (C, H, N)
calcd: 53.93, 6.74, 7.86;found: 53.84, 6.68, 7.49.
Data set and parameters. Physicochemical parameters
for the substituents like Hansch–Fujita’s substituent con-
stant characterizing hydrophobicity (p), Hammet’s con-
stant (s) representing electron withdrawing power of the
substituent, steric parameter (Es), molar refractivity
(MR), field effect (F), resonance effect (R), sterimol
steric parameters (L, B1 and B5) were compiled from
the literature.15 Descriptors for the whole molecule like
Clog P and CMR were calculated using software pro-
gram ClogP of Biobyte corporation16 (http://www.bioby-
te.com/). Partition coefficients (pR5) and molar
refractivity (MRR5) for aliphatic substituents were calcu-
lated by subtracting the parent structure value from that
of the respective compound. For example, p value of
CH3 group in compound 22 was obtained by subtract-
ing Clog P value of parent structure 21 from compound 22
(i.e., 0.26–0.22=0.04). All the parameters are recorded in
Tables 4 and 5. Antitumor activities of the compounds
were subjected to multiple regression analyses.
5-N-Phenyl-2-(40-ethyl benzenesulphonyl) glutamine 41.
MS (FAB): M+H+ peak at m/z 391. 1H NMR
(200MHz, CDCl3): d 7.78 (m, 2H, H-20, H-60), 7.65–7.20
(m, 7H, H-30, H-50, ph-protons), 6.78 (m, 2H, SO2NH),
5.89 (m, 1H, CONH), 3.87 (m, 1H, H-2), 2.74 (m, 2H,
CH2 of C2H5ph), 2.48–2.15 (m, 4H, H2-4, H2-3), 1.30
(m, 3H, CH3 of C2H5ph). IR (KBr, cmÀ1): 3307, 3185
(N–H str of CONH), 3034 (Ar C–H str), 2912, 2878 (ali
C–H str), 1705 (C¼O str), 1617, 1583, 1534, 1432 (ali C–
H def), 1326, 1308 and 1152 (S¼O str of SO2NH), 826,
748 and 705 (Ar C–H def), 688. Anal. C20H24N2O5S1 (C,
H, N) calcd: 59.40, 5.94, 6.93;found: 59.39, 5.68, 7.21.
Correlation analysis
Correlation analyses of various physicochemical para-
meters used in developing the equation were performed
and the resultant correlation matrix is given in Table 6.
Intercorrelated parameters were eliminated stepwise
depending on their individual correlation with the bio-
logical activity. All possible combinations of parameters
were considered.
Pharmacology
Tumor cells. Ehrlich ascites carcinoma (EAC) cells were
maintained in vivo in Swiss albino mice, by passage
after every 10 days. EAC cells 9 days old were used for
the screening of all final compounds 6–41.
Multiple regression analysis
Animals. Male Swiss albino mice 10 weeks old with
an average body weight of 18–20 g were used. All
mice were kept on basal metabolic diet with water ad
libitum.
Multiple regression analysis was carried out and statis-
tical quality of the equations17 were justified by para-
meters like correlation coefficient (r or R), standard error

K. Srikanth et al. / Bioorg. Med. Chem. 10 (2002) 2119–2131
2131
of the estimate (SEE), variance ratio (F) at specified
degrees of freedom (df) and constant terms of regression
equations: regression coefficients and intercepts. Sig-
nificance of the regression coefficients was justified by t-
test.18 Predictor variables with the higher p values were
removed in developing the equation to get the more
acceptable equation with statistical quality.
7. (a) Sukemori, S.;Sugimura, K. Cancer Biochem. Biophys
1994, 14, 99. (b) Devreker, F.;Winston, R. M.;Hardy, K.
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8. Yaqoob, P.;Calder, P. C. Nutrition 1997, 13, 646.
9. New Sholme, E. A.;Calder, P. C. Nutrition 1997, 13, 728.
10. (a) Srikanth, K.;Debnath, B.;Jha, T. Bioorg. Med. Chem.
2002, 10, 1841–1854. (b) Srikanth, K.;Kumar, Ch. A.;
Goswami, D.;De, A. U.;Jha, T. Ind. J. Biochem. Biophys.
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A. U. Anticancer Drug Des. 1993, 8, 95.
11. Hannaford, F.;Tatchell, S. In: Vogel’s Textbook of Prac-
tical Organic Chemistry;ELBS/Longman: Singapore, 1996;p
877.
12. March, J. (Ed). In Advanced Organic Chemistry, Reac-
tions, Mechanism and Structure;John Wiley & Sons: New
York, 1992;p 417.
QSAR validation
Robustness of the QSAR model was done by cross
validation21 by predicting the activities of the com-
pounds in test set. Test set compounds were those which
were not used in developing QSAR model. In this study,
six compounds were grouped as the test set and 30
compounds were used in developing a QSAR model
which were labeled as the training set. Calculation
power of the final QSAR equations was validated by
leave-one-out (LOO)19 prediction. Each compound of
the list was deleted once from the data set and the
regression equation obtained thereby was used to cal-
culate the activity of the deleted compound. These are
listed in Table 4.
13. Thomas, S.;Huy nh, T.;Enriquez-Rios, V.;Singaram, B.
Org. Lett. 2001, 3, 3915.
14. (a) Netzeva, T.;Doytchinova, I.;Natcheva, R.
Pharm.
Res. 2000, 17, 727. (b) So, S. S.;van Helden, S. P.;van Geer-
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Acknowledgements
One of the authors (K. Srikanth) is thankful to the
Council of Scientific and Industrial Research (CSIR),
New Delhi, India for providing a Senior Research Fel-
lowship (Award No.: 9/96(320)/99—EMR-I). The work
is also supported by the funding from the University
Grants Commission (UGC), New Delhi as well as the
All India Council for Technical Education (AICTE),
New Delhi.
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