Selective COX-2 inhibitors. Part 2: Synthesis and biological evaluation of 4-benzylideneamino- and 4-phenyliminomethyl-benzenesulfonamides

Article abstract of DOI:10.1016/j.bmc.2007.11.033

Two series of 4-benzylideneamino- and 4-phenyliminomethyl-benzenesulfonamide derivatives were designed and synthesized for the evaluation as selective cyclooxygenase-2 (COX-2) inhibitors in a cellular assay using human whole blood (HWB). Extensive structure-activity relationships (SAR) were studied within these series. Several compounds were found to be novel and selective COX-2 inhibitors. Among them, the most potent and selective was 4-(3-carboxy-4-hydroxy-benzylideneamino)benzenesulfonamide (20, LA2135), (IC₅₀'s for COX-1: 85.13 μM; COX-2: 0.74 μM; SI: 114.5), being more active COX-2 selective than celecoxib.

Full text of DOI:10.1016/j.bmc.2007.11.033

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 2697–2706
Selective COX-2 inhibitors. Part 2: Synthesis
and biological evaluation of 4-benzylideneamino- and
4-phenyliminomethyl-benzenesulfonamidesq
Shwu-Jiuan Lin,a Wei-Jern Tsai,b Wen-Fei Chiou,b
Tsang-Hsiung Yanga and Li-Ming Yanga,b,
*
aDepartment of Medicinal Chemistry, College of Pharmacy, Taipei Medical University, 250 Wu-Hsing St., Taipei 110, Taiwan
bDivision of Medicinal Chemistry, National Research Institute of Chinese Medicine, 155-1 Li-Nong St., Sec. 2, Taipei 112, Taiwan
Received 16 October 2007; revised 11 November 2007; accepted 12 November 2007
Available online 17 November 2007
Abstract—Two series of 4-benzylideneamino- and 4-phenyliminomethyl-benzenesulfonamide derivatives were designed and synthe-
sized for the evaluation as selective cyclooxygenase-2 (COX-2) inhibitors in a cellular assay using human whole blood (HWB).
Extensive structure–activity relationships (SAR) were studied within these series. Several compounds were found to be novel and
selective COX-2 inhibitors. Among them, the most potent and selective was 4-(3-carboxy-4-hydroxy-benzylideneamino)benzenesul-
fonamide (20, LA2135), (IC50’s for COX-1: 85.13 lM; COX-2: 0.74 lM; SI: 114.5), being more active COX-2 selective than
celecoxib.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
toward thromboxane, which can increase the risk of car-
diovascular event, coronary artery diseases, heart at-
tack, and stroke in some patients.4 This could explain
the cardiotoxicity caused by rofecoxib (Vioxxꢁ) and val-
decoxib (Bextraꢁ), which were recently withdrawn from
the market.5 Thus, there is an urgent need to search for
new selective COX-2 inhibitors with a mild therapeutic
effect on COX-1 inhibition, which could theoretically re-
duce the cardiovascular side effects due to their anti-
platelet and anti-thrombotic activities, and improve
the safety profiles.6
Nonsteroidal anti-inflammatory drugs (NSAIDs) are
widely used for the treatment of pain, fever, and inflam-
mation. Traditional NSAIDs act as nonselective inhibi-
tors of cyclooxygenase (COX) enzymes, which catalyze
the formation of prostaglandins (PGs) from arachidonic
acid. COX exists in at least two isoforms.1,2 COX-2 is in-
duced in response to proinflammatory conditions, while
COX-1 is constitutive and responsible for the mainte-
nance of physiological homeostasis. This discovery led
to the theory that inhibition of COX-1 causes the side
effects of NSAIDs such as gastric ulceration, bleeding,
and renal function suppression, whereas inhibition of
COX-2 accounts for their therapeutic effects.3 Normally,
prostacyclin (PGI2) and thromboxane (TxA2) balance
each other’s opposing effects. Introducing the selective
COX-2 inhibitor may disrupt the balance dangerously
The majority of selective COX-2 inhibitors belong to a
class of tricyclic sulfone/sulfonamide compounds possess-
ing 1,2-diaryl substitution on a central heterocyclic or car-
bocyclic ring system.7,8 (Fig. 1). Recently, a number of
naturally occurring trans-stilbenoids have been reported
as inhibitors of COX. For example, resveratrol (3,40,5-tri-
hydroxy-trans-stilbene) is a phytoalexin present mainly in
the skin of grapes and red wine. It has broad spectrum
pharmacological activities (antioxidant, neuroprotective,
anti-inflammatory, cardioprotective, cancer chemopre-
ventive, etc.)9,10 and has been shown to exhibit moderate
selective COX-1 inhibitory activity.11,12
Keywords: Selective COX-2 inhibitors; Anti-inflammatory; Benzene-
sulfonamide; Benzylideneamino; Phenyliminomethyl; Resveratrol; Iso-
sterism; SAR.
q
A portion of this work was presented in poster form at the 234th
ACS National Meeting, Medicinal Chemistry (abstract #282),
Boston, MA, August 19–23, 2007.
Corresponding author. Tel.: +886 2 2820 1999x8551; fax: +886 2
*
As an alternative to convert a COX-1 selective com-
pound into a COX-2 selective inhibitor, we have de-
2826 4276; e-mail: lmyang@nricm.edu.tw
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.11.033

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S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
MeO2S H2NO2S
H2NO2S
N
N
CF3
O
O
N
O
Celecoxib (Celebrex
Rofecoxib (Vioxx
Valdecoxib (Bextra
)
)
)
Figure 1. Selective tricyclic COX-2 inhibitors.
signed and modified the basic skeleton of trans-stilbene
based on the concept of isosterism,13 which lacks a tra-
ditional central heterocyclicꢁor carbocyclic ring template
such as celecoxib (Celebrex ).14 We previously reported
that the 4-(4-amino-2-methylsulfanyl-phenylazo)ben-
zenesulfonamide (38) demonstrates a moderate COX-2
selectivity.15 However, it is still unclear if the central
double bond linkage within the scaffold optimizes their
activity. In order to extend SAR and design more effica-
cious and selective COX-2 inhibitors with less cardiotox-
icity, new benzenesulfonamides have been developed
based on the bioisosteric replacement of the central
–N@N– linkage with –N@C– or –C@N– double bond.
These include the 4-benzylideneamino- and 4-phenylim-
inomethyl-benzenesulfonamide derivatives (6–26 and
27–36, respectively). We further investigated various
substituents on the phenyl B-ring segment in order to
obtain compounds with high COX-2 selectivity and po-
tency that we were seeking. These strategies are illus-
trated in Figure 2.
2. Synthesis
4-Benzylideneaminobenzenesulfonamide
derivatives
were synthesized by condensation of sulfanilamide with
the appropriately substituted benzaldehyde according to
the standard procedures16 (Scheme 1). The usual work-
up was followed by recrystallization from ethanol to
give the corresponding Schiff bases (6–16 and 21–26,
respectively). However, attempts to use this general
approach for the coupling of sulfanilamide with
3-hydroxybenzaldehyde,
3,4-dihydroxybenzaldehyde,
vanillin, or 5-formylsalicylic acid, respectively, to give
the desired compounds (17–20) failed. Thus, these benz-
aldehydes were protected with benzyl bromide followed
O
H2N S
O
OH
SCH3
HO
N
N
NH2
Phenylazobenzene-
OH
Resveratrol
N
sulfonamide (38)
O
H2N S
O
O
H2N S
O
B
B
N
R
R
4-Benzylideneamino-
benzenesulfonamides
4-Phenyliminomethyl-
benzenesulfonamides
Figure 2. Classic bioisosterism.
O
H2N S
O
O
5
+
NH2
H2N S
O
N
OHC
R
4
1
R
3
6. R4= H
7. R4= F
15. R4= OCH3
16. R3= OCH3
8. R4= CO2Me 21. R3= OC2H5, R4= OH
9. R4= NO2
10. R3= NO2
11. R4= NMe2
12. R4= OH
13. R4= CF3
14. R4= CH3
22. R3= OH,
23. R3= OCH3, R4= OCH3
24. R3= OCH3, R5= OCH3
25. R3= OMe, R4= OMe, R5= OMe
26. R3= OMe, R4= OH, R5= OMe
R4= OCH3
Scheme 1. Synthesis of 4-benzylideneaminobenzenesulfonamides 6–16 and 21–26.

S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
2699
O
BBr3
CH2CH2
KI
BnBr,
Sulfanilamide
H2N S
O
N
OHC
OHC
K2CO3, EtOH
4
R
R
R
3
1a. R3= OBn
37a. R3= OBn
a. 3-hydroxybenzaldehyde
b. 3,4-dihydroxybenzaldehyde 1b. R3= OBn, R4= OBn
37b. R3= OBn, R4= OBn
37c. R3= OCH3, R4= OBn
37d. R3= CO2Bn, R4= OBn
c. vanillin
1c. R3= OCH3, R4= OBn
1d. R3= CO2Bn, R4= OBn
d. 5-formylsalicylic acid
O
H2N S
O
N
4
R
3
17. R3= OH
18. R3= OH,
19. R3= OCH3, R4= OH
20. R3= CO2H, R4= OH
R4= OH
Scheme 2. Synthesis of 4-benzylideneaminobenezenesulfonamides 17–20.
O
H2N S
O
O
H2N S
O
O
NaNO2
HCl
KCN
CuSO4 5H2O
NH2
N+ NCl−
H2N S
CN
.
O
2
3
O
O
H2N S
O
Ni-Al
HCO2H
+
CHO
H2N S
O
H2N
MeOH
R
4
N
5
4
R
3
27. R4= H
28. R4= F
29. R4= Me
32. R4= OH
33. R4= OMe
34. R3= OMe, R4= OMe
30. R4= CF3 35. R3= CO2Me, R4= OH
31. R4= NMe2 36. R4= CO2Me
Scheme 3. Synthesis of 4-phenyliminomethylbenzenesulfonamides 27–36.
by coupling with sulfanilamide to give the protected
intermediates (37a–d). Subsequent acidic cleavage of
the benzyl protecting group afforded the target com-
pounds (17–20) (Scheme 2).
to evaluate the selectivity of COX inhibitory potency
by the human whole blood (HWB) assay.18 The SAR
exploration is summarized in Tables 1 and 2. Resvera-
trol, NS398, and celecoxib were evaluated as reference
compounds in the in vitro assay. COX-1 activity was
measured as TxB2 production after stimulation of plate-
let aggregation by calcium ionophore A-23,187. COX-2
activity was measured as PGE2 levels produced by leu-
kocytes after stimulation by LPS.19
4-Phenyliminomethylbenzenesulfonamide
derivatives
(27–36) were synthesized according to synthetic proce-
dures described previously to prepare the key intermedi-
ate of 4-formylbenzenesulfonamide 417 as shown in
Scheme 3. Following the coupling of aldehyde 4 with
the appropriate aniline in methanol yielded the corre-
sponding imines (27–36). The proposed structures were
characterized by detailed 1H, 13C NMR (HMQC,
HMBC, COSY), high resolution electron impact (HR-
EIMS) analyses, and analytical thin-layer chroma-
tography.
The SAR of different monosubstituents in the phenyl
ring B is shown in Table 1. Different monosubstituents
preferably at the 3- or 4-position of the phenyl ring B
had the greatest influence on COX-2 selectivity. These
studies demonstrated that the 4-hydroxy derivative 12
as the parent compound exhibited moderate COX-2
selectivity (COX-2 IC50 = 3.42 lM; SI = 43.4). Com-
pared to compound 12, replacement of the 4-hydroxy
moiety 12 with an electron withdrawing group such as
4-fluoro (7), 4-methoxycarbonyl (8), or 4-nitro (9) sub-
stituents increased COX-2 inhibitory potency and selec-
tivity. However, compound 10 with a 3-nitro substituent
resulted in loss of COX-2 inhibitory potency. On the
other hand, the 4-N,N-dimethylamino substituent 11
exhibited potent and selective inhibition of COX-2
(COX-2 IC50 = 3.36 lM; SI = 58.2). Among these com-
3. Results and discussion
The extensive SAR studies of the 4-benzylideneamino-
and 4-phenyliminomethyl-benzenesulfonamides as the
selective COX-2 inhibitors have been investigated. The
IC50 lM values for COX isozymes activity and the selec-
tivity index (SI) calculation of COX-1/COX-2 IC50 ra-
tios for different COX inhibitory activities allowed us

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S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
Table 1. Inhibitory activity of 4-benzylideneaminobenzenesulfonamides using human whole blood assay
6' 5'
O
5
H2N S
O
N
4
2' 3'
R
3
*
Compound
R
HWB IC50 (lM)
Selectivity index
COX-1/COX-2
COX-1
COX-2
6
4-H
4-F
108.34
159.07
183.50
141.25
105.63
195.74
148.20
182.19
190.47
313.83
383.36
38.20
2.87
2.22
37.8
71.5
67.3
47.1
15.6
58.2
43.4
39.6
38.5
31.8
70.4
13.7
8.1
7
8
4-CO2Me
4-NO2
3-NO2
2.73
3.00
9
10
6.75
3.36
11
12
4-NMe2
4-OH
3.42
4.60
13
14
4-CF3
4-CH3
4.94
9.88
15
16
4-OCH3
3-OCH3
3-OH
5.45
2.78
17
18
3,4-(OH)2
3-OCH3, 4-OH
3-CO2H, 4-OH
3-OC2H5, 4-OH
3-OH, 4-OCH3
3,4-(OCH3)2
3,5-(OCH3)2
3,4,5-(OCH3)3
3,5-(OCH3)2, 4-OH
23.15
78.20
2.85
2.95
19
20 (LA2135)
26.5
114.5
13.0
12.5
35.6
32.3
57.0
57.5
0.1
85.13
47.91
43.80
0.74
3.69
21
22
3.50
3.09
23
24
110.27
109.69
167.09
155.95
3.40
2.93
25
26
2.71
Resveratrol
NS398
Celecoxib
4.12 1.76
35.68 5.80
23.47 3.45
34.61 1.57
0.61 0.12
0.30 0.06
59.0
78.0
* Values are the means SEM from three independent experiments using COX assay kits (Catalog Nos.: 519031 and 514010, Cayman Chemicals
Inc., Ann Arbor, MI, USA). Since SEM values never exceeded 15% of the media, they have been omitted.
pounds (7–12) with monosubstituted at the para-posi-
tion, the COX-2 inhibitory selectivity order was
4-F > 4-CO2Me > 4-NMe2 > 4-NO2 > 4-OH > unselective
3-NO2. In contrast, introduction of a 4-trifluoromethyl
(13), 4-methyl (14), 4-methoxy (15), or the unsubstituted
analogue 6 exhibited slightly less selectivity than com-
pound 12 as shown in Table 1. Interestingly, substitu-
tion by a 3-methoxy (16) led to a drop in potency but
was quite selective for COX-2 (SI = 70.4). Thus, we
investigated the hydroxy derivatives (12, 17, and 18),
except for the 4-hydroxy substituent 12, exhibiting a
marked loss of COX-2 inhibitory selectivity. These
results suggest that compounds 17, 18, and 22 with an
electron donating hydroxyl substituent effect at the
3-position may display a dramatic loss of COX-2 inhib-
itory selectivity.
matic increase in potency (IC50 = 0.74 lM) with an
excellent selective COX-2 inhibitory activity (SI =
114.5) comparable to the selectivity of the reference
compounds resveratrol (SI = 0.1) and celecoxib
(SI = 78). One explanation for this dramatic substituent
effect is the electron withdrawing properties of the 3-car-
boxylic acid moiety attached adjacent to the electron
donating group, thus amplifying the conjugative effects
of the 4-hydroxy group. The counterbalancing effect of
these two groups results in the phenyl ring B having
an optimal potency to achieve the desired COX-2
selectivity.
In general, trisubstitution on the phenyl ring B further
increased the potency and selectivity of the COX-2
inhibitors. The 3,4,5-trimethoxy derivative 25 and 4-hy-
droxy-3,5-dimethoxy substituent 26 were more selective
against COX-2 (SI values of 57.0 and 57.7, respectively)
than the corresponding disubstituted analogues 3,4-
dimethoxy substituent 23 and 3,5-dimethoxy substituent
24 (SI values of 35.6 and 32.3, respectively). Again, the
more electron donating methoxy substituents on the
phenyl ring B made positive contributions to the
COX-2 inhibitory selectivity.
Other disubstitution at the 3- and 4-positions of the phe-
nyl ring B, except for compound 20, did not further en-
hance COX-2 selectivity compared to the monosubstitu-
tion. The 4-hydroxy-3-methoxy substitution 19 showed
a potent and moderate COX-2 selectivity (SI = 26.5).
Moreover, the substitution of the 3-ethoxy-4-hydroxy
(21) or 3-hydroxy-4-methoxy (22) reduced potency and
COX-2 selectivity more significantly. However, the
corresponding 4-(3-carboxy-4-hydroxy-benzylideneami-
no)benzenesulfonamide (20, LA2135) resulted in a dra-
To extend the exploration for the different central dou-
ble bond linkage, the bridge –N@C– was replaced by

S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
2701
Table 2. Inhibitory activity of 4-phenyliminomethylbenzenesulfonamides using human whole blood assay
6' 5'
O
H2N S
4
R
N
O
2' 3'
3
*
Compound
R
HWB IC50 (lM)
Selectivity index
COX-1
COX-2
COX-1/COX-2
27
28
4-H
4-F
63.59
80.20
63.22
43.89
64.42
51.83
60.74
31.27
23.99
56.73
3.11
4.38
20.5
18.3
13.7
6.7
29
30
4-Me
4-CF3
4.62
6.54
31
32
4-NMe2
4-OH
1.95
5.09
33.0
10.2
14.7
7.3
33
34
4-OMe
3,4-(OMe)2
3-CO2Me, 4-OH
4-CO2Me
4.14
4.28
35
36
3.13
3.72
7.7
15.3
0.1
Resveratrol
NS398
Celecoxib
4.12 1.76
35.68 5.80
23.47 3.45
34.61 1.57
0.61 0.12
0.30 0.06
59.0
78.0
* Values are the means SEM from three independent experiments using COX assay kits (Catalog Nos.: 519031 and 514010, Cayman Chemicals
Inc., Ann Arbor, MI, USA). Since SEM values never exceeded 15% of the media, they have been omitted.
isosteric –C@N– bond, and the 4-phenyliminomethyl-
benzenesulfonamide series were synthesized and evalu-
ated for their ability to inhibit COX isozymes in vitro.
Bioassay exploration results are shown in Table 2. These
series of compounds showed a poor COX-2 inhibitory
activity with the lower selectivity indices than the exhib-
iting of 4-benzylideneaminobenzenesulfonamides, but
31 with a 4-N,N-dimethylamino moiety exhibited a
moderate COX-2 inhibitory selectivity in this series with
an SI value of 33.0.
5. Experimental
5.1. General
All commercial chemicals were used as obtained without
further purification. Melting points were determined
with a Buchi capillary melting point apparatus and were
¨
uncorrected. NMR spectra were recorded on Varian
Unity Inova-500 spectrometer. The samples were dis-
solved in DMSO-d6 and measured in 5 mm NMR tubes.
Chemical shifts values (d) are expressed in ppm referred
to TMS and coupling constants (J) in hertz. The EIMS
spectra were measured with direct insertion probe on a
Finnigan GCQ spectrometer at 30 eV. HR-EIMS spec-
tral data were recorded on a Finnigan MAT 95S mass
spectrometer. Thin-layer chromatography was per-
formed on Merck Kieselgel 60 F254 precoated aluminum
silica gel sheets. Flash column chromatography was car-
ried out on Merck Kieselgel 60 (230–400 mesh).
4. Conclusions
In summary, an isosteric modification and optimiza-
tion of a central double bond of trans-stilbene resvera-
trol, a cyclooxygenase inhibitor with a moderate
activity against COX-1, can yield benzenesulfonamides
with altered COX-2 inhibitory potency and selectivity.
Based on these results, it is clear that the novel 4-ben-
zylideneaminobenzenesulfonamides
(the
central
5.2. General procedure for the synthesis of 4-benzylide-
neaminobenzenesulfonamides
–N@C– series) are more potent and selective for
COX-2 inhibitory activity than the 4-phenyliminom-
ethylbenzenesulfonamides (the central –C@N– series).
Several compounds (7, 20, 25, and 26) exhibited good
COX-2 inhibitory potency and selectivity. Among the
SAR studies, compound 20 (LA2135) was proved to
be the most potent and selective COX-2 inhibitor
(COX-1 IC50 = 85.13 lM; COX-2 IC50 = 0.74 lM;
SI = 114.5) exhibiting the comparable selectivity as
the reference compounds celecoxib, NS398, and resve-
ratrol in this series. Mechanisms of the COX-2 inhib-
itory selectivity remain to be elucidated, but
compound 20 (LA2135) can be considered as a lead
compound in the design of a new class of potent
drugs. Further optimization based on 20 will be de-
scribed in the near future.
A mixture of sulfanilamide and the appropriate benzal-
dehyde (1.15 equiv) was stirred in oil bath for 5 min at
150 ꢂC and then cooled to room temperature. The crude
crystalline obtained was filtered and purified by recrys-
tallization from ethanol to afford the corresponding
Schiff bases. Physical and spectral data for 6–16 and
21–26 are listed below.
5.2.1. 4-Benzylideneamino-benzenesulfonamide (6). Com-
pound 6 was synthesized using benzaldehyde (yield
78%); mp 188–190 ꢂC; 1H NMR: d 7.34 (s, –NH2),
7.38 (d, J = 8.5 Hz, H-30, H-50), 7.52–7.57 (m, H-
3,4,5), 7.84 (d, J = 8.5 Hz, H-20, H-60), 7.95 (d,
J = 8.0 Hz, H-2, H-6), 8.63 (s, –NCH). 13C NMR: d

2702
S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
121.3 (C-30, C-50), 127.0 (C-20, C-60), 128.9 (C-3, C-5),
129.0 (C-2, C-6), 132.1 (C-4), 135.6 (C-1), 141.2 (C-10),
154.4 (C-40), 162.8 (–NCH). HR-MS m/z calcd for
C13H12N2O2S 260.0619, found 260.0622.
6), 140.1 (C-10), 152.7 (C-4), 155.3 (C-40), 161.7
(–NCH). HR-MS m/z calcd for C15H17N3O2S
303.1042, found 303.1041.
5.2.7. 4-(4-Hydroxy-benzylideneamino)-benzenesulfon-
amide (12). Compound 12 was synthesized using 4-
hydroxybenzaldehyde (yield 40%); mp 208–210 ꢂC; H
NMR: d 6.89 (d, J = 8.5 Hz, H-3, H-5), 7.31 (s,
–NH2), 7.32 (d, J = 8.5 Hz, H-30, H-50), 7.79 (d,
J = 8.5 Hz, H-2, H-6), 7.81 (d, J = 8.5 Hz, H-20, H-60),
8.47 (s, –NCH). 13C NMR: d 115.8 (C-3, C-5), 121.1
(C-30, C-50), 126.9 (C-20, C-60), 127.1 (C-1), 131.1 (C-2,
C-6), 140.6 (C-10), 154.9 (C-40), 161.1 (C-4), 161.9
(–NCH). HR-MS m/z calcd for C13H12N2O3S
276.0569, found 276.0571.
5.2.2. 4-(4-Fluoro-benzylideneamino)-benzenesulfonamide
(7). Compound 7 was synthesized using 4-fluorobenzal-
dehyde (yield 80%); mp 145–147 ꢂC; 1H NMR: d 7.34 (s,
–NH2), 7.37 (t, J = 9.0 Hz, H-3, H-5), 7.38 (d,
J = 8.5 Hz, H-30, H-50), 7.84 (d, J = 8.5 Hz, H-20, H-
60), 8.01 (dd, J = 6.0, 9.0 Hz, H-2, H-6), 8.63 (s,
–NCH). 13C NMR: d 116.1 (d, J = 21.9 Hz, C-3, C-5),
121.3 (C-30, C-50), 127.0 (C-20, C-60), 131.5 (d,
J = 9.0 Hz, C-2, C-6), 132.4 (d, J = 2.9 Hz, C-1), 141.2
(C-10), 154.3 (C-40), 161.6 (–NCH), 164.4 (d,
1
J = 248.9 Hz,
C-4).
HR-MS
m/z
C13H11FN2O2S 278.0525, found 278.0525.
calcd
for
5.2.8. 4-(4-Trifluoromethyl-benzylideneamino)-benzene-
sulfonamide (13). Compound 13 was synthesized using
4-(trifluoromethyl)benzaldehyde (yield 67%); mp 188–
5.2.3. 4-(4-Methoxycarbonyl-benzylideneamino)-benzene-
sulfonamide (8). Compound 8 was synthesized using
methyl 4-formylbenzoate (yield 84%); mp 202–204 ꢂC;
1H NMR: d 3.87 (s, –OCH3), 7.36 (s, –NH2), 7.43 (d,
J = 8.5 Hz, H-30, H-50), 7.86 (d, J = 8.5 Hz, H-20, H-
60), 8.08 (d, J = 8.5 Hz, H-2, H-6), 8.11 (d, J = 8.5 Hz,
H-3, H-5), 8.74 (s, –NCH). 13C NMR: d 52.4
(–OCH3), 121.4 (C-30, C-50), 127.0 (C-20, C-60), 129.1
(C-2, C-6), 129.7 (C-3, C-5), 132.1 (C-4), 139.5 (C-1),
141.6 (C-10), 153.9 (C-40), 162.0 (–NCH), 165.8
(C@O). HR-MS m/z calcd for C15H14N2O4S 318.0674,
found 318.0674.
191 ꢂC; 1H NMR:
d 7.37 (s, –NH2), 7.44 (d,
J = 8.5 Hz, H-30, H-50), 7.87 (d, J = 8.5 Hz, H-20, H-
60), 7.91 (d, J = 8.5 Hz, H-3, H-5), 8.16 (d, J = 8.5 Hz,
13
H-2, H-6), 8.76 (s, –NCH). C NMR: d 121.4 (C-30,
C-50), 124.0 (q, J = 270.8 Hz, CF3), 125.9 (d,
J = 4.0 Hz, C-3, C-5), 127.0 (C-20, C-60), 129.6 (C-2,
C-6), 131.4 (q, J = 31.3 Hz, C-4), 139.2 (C-1), 141.7
(C-10), 153.8 (C-40), 161.7 (–NCH). HR-MS m/z calcd
for C14H11F3N2O2S 328.0493, found 328.0494.
5.2.9. 4-(4-Methyl-benzylideneamino)-benzenesulfon-
amide (14). Compound 14 was synthesized using p-tolu-
1
5.2.4. 4-(4-Nitro-benzylideneamino)-benzenesulfonamide
(9). Compound 9 was synthesized using 4-nitrobenzalde-
aldehyde (yield 55%); mp 198–200 ꢂC; H NMR: d 2.38
(s, –CH3), 7.33 (s, –NH2), 7.35 (d, J = 8.0 Hz, H-3, H-5),
7.37 (d, J = 8.5 Hz, H-30, H-50), 7.83 (d, J = 8.5 Hz, H-
20, H-60), 7.84 (d, J = 8.0 Hz, H-2, H-6), 8.58 (s,
1
hyde (yield 30%); mp 185–188 ꢂC; H NMR: d 7.38 (s,
–NH2), 7.47 (d, J = 8.5 Hz, H-30, H-50), 7.88 (d,
J = 8.5 Hz, H-20, H-60), 8.21 (d, J = 8.5 Hz, H-2, H-6),
8.38 (d, J = 8.5 Hz, H-3, H-5), 8.82 (s, –NCH). 13C
NMR: d 121.5 (C-30, C-50), 124.1 (C-3, C-5), 127.0 (C-
20, C-60), 130.0 (C-2, C-6), 141.0 (C-1), 142.0 (C-10),
149.2 (C-4), 153.5 (C-40), 161.2 (–NCH). HR-MS m/z
calcd for C13H11N3O4S 305.0470, found 305.0471.
13
–NCH). C NMR: d 21.3 (–CH3), 121.3 (C-30, C-50),
127.0 (C-20, C-60), 129.1 (C-2, C-6), 129.6 (C-3, C-5),
133.1 (C-1), 141.0 (C-10), 142.3 (C-4), 154.6 (C-40),
162.6 (–NCH). HR-MS m/z calcd for C14H14N2O2S
274.0776, found 274.0777.
5.2.10. 4-(4-Methoxy-benzylideneamino)-benzenesulfon-
amide (15). Compound 15 was synthesized using p-anis-
aldehyde (yield 70%); mp 195–197 ꢂC; H NMR: d 3.83
(s, –OCH3), 7.08 (d, J = 8.5 Hz, H-3, H-5), 7.32 (s,
–NH2), 7.34 (d, J = 8.5 Hz, H-30, H-50), 7.82 (d,
J = 8.5 Hz, H-20, H-60), 7.90 (d, J = 8.5 Hz, H-2, H-6),
8.54 (s, –NCH). 13C NMR: d 55.5 (–OCH3), 114.4 (C-
3, C-5), 121.2 (C-30, C-50), 127.0 (C-20, C-60), 128.6 (C-
1), 130.9 (C-2, C-6), 140.8 (C-10), 154.8 (C-40), 161.9
(–NCH), 162.4 (C-4). HR-MS m/z calcd for
C14H14N2O3S 290.0725, found 290.0728.
5.2.5. 4-(3-Nitro-benzylideneamino)-benzenesulfonamide
(10). Compound 10 was synthesized using 3-nitrobenzal-
dehyde (yield 23%); mp 169–171 ꢂC; 1H NMR: d 7.37 (s,
–NH2), 7.46 (d, J = 8.5 Hz, H-30, H-50), 7.84 (t,
J = 8.0 Hz, H-5), 7.87 (d, J = 8.5 Hz, H-20, H-60), 8.38
(d, J = 8.0 Hz, H-6), 8.41 (m, H-4), 8.75 (d, J = 1.7 Hz,
1
13
H-2), 8.83 (s, –NCH). C NMR: d 121.5 (C-30, C-50),
123.1 (C-2), 126.2 (C-4), 127.0 (C-20, C-60), 130.7 (C-
5), 134.8 (C-6), 137.1 (C-1), 141.8 (C-10), 148.2 (C-3),
153.5 (C-40), 161.1 (–NCH). HR-MS m/z calcd for
C13H11N3O4S 305.0470, found 305.0473.
5.2.11. 4-(3-Methoxy-benzylideneamino)-benzenesulfon-
amide (16). Compound 16 was synthesized using m-anis-
aldehyde (yield 32%); mp 145–148 ꢂC; H NMR: d 3.82
(s, –OCH3), 7.13–7.15 (m, H-4), 7.35 (s, –NH2), 7.38 (d,
J = 8.5 Hz, H-30, H-50), 7.45 (t, J = 8.0 Hz, H-5), 7.51 (d,
J = 1.5 Hz, H-2), 7.53 (m, H-6), 7.84 (d, J = 8.5 Hz, H-
20, H-60), 8.60 (s, –NCH). 13C NMR: d 55.3 (–OCH3),
112.8 (C-2), 118.3 (C-4), 121.3 (C-30, C-50), 122.0 (C-
6), 127.0 (C-20, C-60), 130.1 (C-5), 137.1 (C-1), 141.2
(C-10), 154.3 (C-40), 159.6 (C-3), 162.7 (–NCH). HR-
5.2.6. 4-(4-Dimethylamino-benzylideneamino)-benzene-
sulfonamide (11). Compound 11 was synthesized using
4-(dimethylamino)benzaldehyde (yield 65%); mp 212–
214 ꢂC; 1H NMR: d 3.01 (s, –N(CH3)2), 6.79 (d,
J = 8.5 Hz, H-3, H-5), 7.28 (s, –NH2), 7.30 (d,
J = 8.5 Hz, H-30, H-50), 7.75 (d, J = 8.5 Hz, H-2, H-6),
7.80 (d, J = 8.5 Hz, H-20, H-60), 8.41 (s, –NCH). 13C
NMR: d 39.8 (–N(CH3)2), 111.4 (C-3, C-5), 121.1 (C-
30, C-50), 123.3 (C-1), 126.9 (C-20, C-60), 130.7 (C-2, C-
1

S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
2703
MS m/z calcd for C14H14N2O3S 290.0725, found
290.0725.
(d, J = 8.5 Hz, H-30, H-50), 7.84 (d, J = 8.5 Hz, H-20,
H-60), 8.54 (s, –NCH). 13C NMR: d 56.0 (3- & 5-
OCH3), 60.2 (4-OCH3), 106.2 (C-2, C-6), 121.2 (C-30,
C-50), 127.0 (C-20, C-60), 131.1 (C-1), 140.8 (C-4),
141.1 (C-10), 153.2 (C-3, C-5), 154.4 (C-40), 162.3
(–NCH). HR-MS m/z calcd for C16H18N2O5S
350.0936, found 350.0935.
5.2.12. 4-(3-Ethoxy-4-hydroxy-benzylideneamino)-ben-
zenesulfonamide (21). Compound 21 was synthesized
using 3-ethoxy-4-hydroxybenzaldehyde (yield 15%);
mp 173–175 ꢂC; 1H NMR: d 1.36 (t, J = 7.0 Hz,
–CH3), 4.08 (q, J = 7.0 Hz, –OCH2), 6.91 (d,
J = 8.0 Hz, H-5), 7.31 (s, –NH2), 7.32 (d, J = 8.5 Hz,
H-30, H-50), 7.35 (dd, J = 1.5, 8.0 Hz, H-6), 7.50 (d,
J = 1.5 Hz, H-2), 7.81 (d, J = 8.5 Hz, H-20, H-60), 8.44
(s, –NCH), 9.78 (br, –OH). 13C NMR: d 14.7 (–CH3),
63.9 (–OCH2), 111.9 (C-2), 115.5 (C-5), 121.2 (C-30, C-
50), 124.5 (C-6); 126.9 (C-20, C-60), 127.5 (C-1), 140.6
(C-10), 147.2 (C-3), 151.0 (C-4), 154.9 (C-40), 162.1
(–NCH). HR-MS m/z calcd for C15H16N2O4S
320.0830, found 320.0831.
5.2.17. 4-(4-Hydroxy-3,5-dimethoxy-benzylideneamino)-
benzenesulfonamide (26). Compound 26 was synthesized
1
using syringaldehyde (yield 52%); mp 228–231 ꢂC; H
NMR: d 3.83 (s, –OCH3 · 2), 7.25 (s, –NH2), 7.32 (s,
H-2, H-6), 7.33 (d, J = 8.5 Hz, H-30, H-50), 7.82 (d,
J = 8.5 Hz, H-20, H-60), 8.46 (s, –NCH), 9.22 (br,
–OH). 13C NMR: d 56.0 (3- & 5-OCH3), 106.6 (C-2,
C-6), 121.1 (C-30, C-50), 126.1 (C-1), 127.0 (C-20, C-60),
139.7 (C-4), 140.6 (C-10), 148.1 (C-3, C-5), 154.8 (C-
40), 162.3 (–NCH). HR-MS m/z calcd for C15H16N2O5S
336.0779, found 336.0778.
5.2.13. 4-(3-Hydroxy-4-methoxy-benzylideneamino)-ben-
zenesulfonamide (22). Compound 22 was synthesized
using 3-hydroxy-4-methoxybenzaldehyde (yield 40%);
5.3. General procedure for the reaction of sulfanilamide
with benzyl-protected benzaldehydes
1
mp 215–218 ꢂC; H NMR: d 3.83 (s, –OCH3), 7.05 (d,
J = 8.5 Hz, H-5), 7.31 (s, –NH2), 7.32 (d, J = 8.5 Hz,
H-30, H-50), 7.34 (dd, J = 2.0, 8.5 Hz, H-6), 7.42 (d,
J = 2.0 Hz, H-2), 7.81 (d, J = 8.5 Hz, H-20, H-60), 8.44
(s, –NCH), 9.39 (br, –OH). 13C NMR: d 55.7 (–
OCH3), 111.7 (C-5), 113.7 (C-2), 121.2 (C-30, C-50),
122.9 (C-6), 126.9 (C-20, C-60), 128.8 (C-1), 140.7 (C-
10), 146.8 (C-3), 151.4 (C-4), 154.7 (C-40), 162.1 (–
NCH). HR-MS m/z calcd for C14H14N2O4S 306.0674,
found 306.0668.
The hydroxy groups of benzaldehyde (3-hydroxybenzal-
dehyde, 3,4-dihydroxybenzaldehyde, vanillin, or 5-form-
ylsalicylic acid, respectively) were protected with benzyl
bromide to give benzyl ether or ester derivatives 1a–d,
followed by coupling with sulfanilamide to give the pro-
tected intermediates (37a–d). Subsequent BBr3/CH2Cl2
cleavage of the protecting group afforded the target
compounds. Physical and spectral data for 17–20 are
listed below.
5.2.14. 4-(3,4-Dimethoxy-benzylideneamino)-benzenesul-
fonamide (23). Compound 23 was synthesized using
5.3.1. 4-(3-Hydroxy-benzylideneamino)-benzenesulfon-
amide (17). Compound 17 was synthesized using the
benzyl-protected 3-hydroxybenzaldehyde (yield 47%);
1
verataldehyde (yield 46%); mp 187–189 ꢂC; H NMR:
d
3.83 (s, –OCH3), 3.84 (s, –OCH3), 7.11 (d,
1
J = 8.5 Hz, H-5), 7.32 (s, –NH2), 7.35 (d, J = 8.5 Hz,
H-30, H-50), 7.47 (dd, J = 2.5, 8.5 Hz, H-6), 7.55 (d,
J = 2.5 Hz, H-2), 7.82 (d, J = 8.5 Hz, H-20, H-60), 8.52
(s, –NCH). 13C NMR: d 55.5, 55.7 (3- & 5-OCH3),
109.5 (C-2), 111.3 (C-5), 121.2 (C-30, C-50), 124.7 (C-
6), 126.9 (C-20, C-60), 128.6 (C-1), 140.8 (C-10), 149.1
(C-3), 152.3 (C-4), 154.7 (C-40), 162.1 (–NCH). HR-
MS m/z calcd for C15H16N2O4S 320.0831, found
320.0832.
mp 206–208 ꢂC; H NMR: d 6.80 (d, J = 8.5 Hz, H-30,
H-50), 7.08–7.11 (m, H-4), 7.13 (s, –NH2), 7.23 (d,
J = 1.5 Hz, H-2), 7.34 (m, H-6), 7.40 (t, J = 8.0 Hz, H-
5), 7.54 (d, J = 8.5 Hz, H-20, H-60), 9.89 (s, –NCH).
13C NMR: d 114.7 (C-2), 115.2 (C-30, C-50), 121.2 (C-
6), 121.9 (C-4), 127.5 (C-20, C-60), 130.4 (C-5), 133.2
(C-10), 137.7 (C-1), 148.1 (C-40), 158.1 (C-3), 193.3
(–NCH). HR-MS m/z calcd for C13H12N2O3S
276.0568, found 276.0567.
5.2.15. 4-(3,5-Dimethoxy-benzylideneamino)-benzenesul-
fonamide (24). Compound 24 was synthesized using 3,5-
dimethoxybenzaldehyde (yield 58%); mp 197–199 ꢂC;
1H NMR: d 3.80 (s, –OCH3 · 2), 6.69 (t, J = 2.5 Hz,
H-4), 7.12 (d, J = 2.5 Hz, H-2, H-6), 7.35 (s, –NH2),
7.37 (d, J = 8.5 Hz, H-30, H-50), 7.84 (d, J = 8.5 Hz, H-
20, H-60), 8.55 (s, –NCH). 13C NMR: d 55.5 (3- & 5-O
CH3), 104.3 (C-4), 106.6 (C-2, C-6), 121.3 (C-30, C-50),
127.0 (C-20, C-60), 137.6 (C-1), 141.3 (C-10), 154.2 (C-
40), 160.7 (C-3, C-5), 162.7 (–NCH). HR-MS m/z calcd
for C15H16N2O4S 320.0830, found 320.0831.
5.3.2. 4-(3,4-Dihydroxy-benzylideneamino)-benzenesul-
fonamide (18). Compound 18 was synthesized using
the benzyl-protected 3,4-dihydroxybenzaldehyde (yield
1
88%); mp 242–244 ꢂC; H NMR: d 6.80 (d, J = 8.5 Hz,
H-30, H-50), 6.89 (d, J = 8.0 Hz, H-5), 7.22 (d,
J = 2.0 Hz, H-2), 7.47 (dd, J = 2.0, 8.0 Hz, H-6), 7.55
(d, J = 8.5 Hz, H-20, H-60), 9.68 (s, –NCH). 13C NMR:
d 114.5 (C-2), 115.2 (C-30, C-50), 115.6 (C-5), 124.6 (C-
6), 127.5 (C-20, C-60), 128.9 (C-1), 146.0 (C-10), 149.1
(C-3), 148.0 (C-40), 152.2 (C-4), 191.2 (–NCH). HR-
MS m/z calcd for C13H12N2O4S 292.0518, found
292.0518.
5.2.16. 4-(3,4,5-Trimethoxy-benzylideneamino)-benzene-
sulfonamide (25). Compound 25 was synthesized using
3,4,5-trimethoxybenzaldehyde (yield 85%); mp 227–
230 ꢂC; 1H NMR: d 3.74 (s, –OCH3), 3.85 (s,
–OCH3 · 2), 7.29 (s, –NH2), 7.34 (s, H-2, H-6), 7.36
5.3.3. 4-(4-Hydroxy-3-methoxy-benzylideneamino)-ben-
zenesulfonamide (19). Compound 19 was synthesized
using the benzyl-protected vanillin (yield 84%); mp
212–214 ꢂC; 1H NMR: d 3.82 (s, –OCH3), 6.80 (d,

2704
S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
J = 8.5 Hz, H-30, H-50), 6.96 (d, J = 8.0 Hz, H-5), 7.37
(d, J = 2.0 Hz, H-2), 7.40 (dd, J = 2.0, 8.0 Hz, H-6),
7.55 (d, J = 8.5 Hz, H-20, H-60), 9.75 (s, –NCH). 13C
NMR: d 55.6 (–OCH3), 110.8 (C-2), 115.2 (C-30, C-50),
115.5 (C-5), 126.1 (C-6), 127.4 (C-20, C-60), 128.7 (C-
1), 133.3 (C-10), 148.0 (C-40), 148.2 (C-3), 153.1 (C-4),
191.1 (–NCH). HR-MS m/z calcd for C14H14N2O4S
306.0674, found 306.0674.
ether to give the corresponding imines. Physical and
spectral data for 27–36 are listed below.
5.6.1. 4-Phenyliminomethyl-benzenesulfonamide (27).
Compound 27 was synthesized using aniline (yield
1
43%); mp 201–203 ꢂC; H NMR: d 7.27–7.32 (m, H-
2,4,6), 7.44 (t, J = 8.0 Hz, H-3, H-5), 7.49 (s, –NH2),
7.95 (d, J = 8.0 Hz, H-20, H-60), 8.10 (d, J = 8.0 Hz, H-
30, H-50), 8.71 (s, –NCH). 13C NMR: d 121.1 (C-2, C-
6), 126.1 (C-20, C-60), 126.5 (C-4), 129.0 (C-30, C-50),
129.3 (C-3, C-5), 138.7 (C-40), 146.1 (C-10), 150.1 (C-
1), 159.4 (–NCH). HR-MS m/z calcd for C13H12N2O2S
260.0619, found 260.0621.
5.3.4. 4-(3-Carboxy-4-hydroxy-benzylideneamino)-ben-
zenesulfonamide (20). Compound 20 was synthesized
using the benzyl-protected 5-formylsalicylic acid (yield
1
73%); mp 213–215 ꢂC; H NMR: d 6.88 (d, J = 8.5 Hz,
H-30, H-50), 7.13 (d, J = 8.5 Hz, H-5), 7.58 (d,
J = 8.5 Hz, H-20, H-60), 8.45 (dd, J = 2.0, 8.5 Hz, H-6),
8.34 (d, J = 2.0 Hz, H-2), 9.87 (s, –NCH). 13C NMR: d
113.8 (C-3), 116.1 (C-30, C-50), 118.3 (C-5), 127.4 (C-
20, C-60), 128.4 (C-1), 133.9 (C-2), 134.3 (C-10), 135.2
(C-6), 146.8 (C-40), 165.7 (C-4), 171.1 (C@O), 191.1
(–NCH). HR-MS m/z calcd for C14H12N2O5S
320.0467, found 320.0467.
5.6.2.
4-(4-Fluoro-phenyliminomethyl)-benzenesulfon-
amide (28). Compound 28 was synthesized using 4-fluo-
roaniline (yield 72%); mp 179–181 ꢂC; 1H NMR: d 7.25–
7.29 (m, H-3, H-5), 7.38–7.40 (m, H-2, H-6), 7.46 (s,
–NH2), 7.94 (d, J = 8.5 Hz, H-20, H-60), 8.09 (d,
J = 8.5 Hz, H-30, H-50), 8.73 (s, –NCH). 13C NMR: d
116.0 (d, J = 22.4 Hz, C-3, C-5), 123.1 (d, J = 8.0 Hz,
C-2, C-6), 126.1 (C-20, C-60), 129.0 (C-30, C-50), 138.6
(C-40), 146.2 (C-10), 147.1 (C-1), 159.4 (–NCH), 160.8
(d, J = 242.0 Hz, C-4). HR-MS m/z calcd for
C13H11FN2O2S 278.0525, found 278.0525.
5.4. 4-Cyanobenzenesulfonamide (3)
A cold solution of NaNO2 (11.7 g, 0.17 mol) was added
to a suspension of sulfanilamide (25 g, 0.15 mol) in
aqueous HCl (2.3 N, 200 mL) at 0 ꢂC with stirring for
10 min. The diazotized solution was poured with vigor-
ous stirring into a suspension of KCN (41.6 g, 0.64 mol)
and CuSO4Æ5H2O (38.5 g, 0.15 mol) in 200 mL of water.
The mixture was stirred at 0 ꢂC for 30 min and was then
heated to 80 ꢂC for 30 min and then chilled. The brown
solid precipitate was collected, dried, and successively
extracted with 5% ethanol in benzene. The combined or-
ganic extracts were concentrated and recrystallized from
water to afford benzonitrile 3 (17.39 g, 66%); mp 155–
5.6.3. 4-(4-Methyl-phenyliminomethyl)-benzenesulfon-
amide (29). Compound 29 was synthesized using p-tolu-
1
idine (yield 66%); mp 206–208 ꢂC; H NMR: d 2.33 (s,
–CH3), 7.24 (s, H-2, H-3, H-5, H-6), 7.47 (s, –NH2),
7.93 (d, J = 8.5 Hz, H-20, H-60), 8.09 (d, J = 8.5 Hz, H-
30, H-50), 8.72 (s, –NCH). 13C NMR: d 20.6 (-CH3),
121.1 (C-2, C-6), 126.1 (C-20, C-60), 128.9 (C-30, C-50),
129.7 (C-3, C-5), 136.1 (C-4), 138.9 (C-40), 146.0 (C-
10), 148.2 (C-1), 158.3 (–NCH). HR-MS m/z calcd for
C14H14N2O2S 274.0776, found 274.0775.
157 ꢂC; 1H NMR:
d 7.63 (s, –NH2), 7.97 (d,
J = 8.5 Hz, H-20, H-60), 8.05 (d, J = 8.5 Hz, H-30, H-
5.6.4. 4-(4-Trifluoromethyl-phenyliminomethyl)-benzene-
sulfonamide (30). Compound 30 was synthesized using 4-
(trifluoromethyl)aniline (yield 63%); mp 165–167 ꢂC; 1H
NMR: d 7.46 (d, J = 8.5 Hz, H-2, H-6), 7.51 (s, –NH2),
7.79 (d, J = 8.5 Hz, H-3, H-5), 7.97 (d, J = 8.5 Hz, H-20,
H-60), 8.13 (d, J = 8.5 Hz, H-30, H-50), 8.74 (s, –NCH).
13C NMR: d 121.7 (C-2, C-6), 125.4 (q, J = 270.0 Hz,
CF3), 126.2 (C-20, C-60), 126.4 (d, J = 3.3 Hz, C-3, C-
5), 131.4 (q, J = 31.3 Hz, C-4), 129.4 (C-30, C-50),
138.2 (C-40), 146.6 (C-10), 154.5 (C-1), 162.0 (–NCH).
HR-MS m/z calcd for C14H11F3N2O2S 328.0493, found
328.0494.
13
50). C NMR: d 114.3 (C-40), 117.9 (–CN), 126.5 (C-
20, C-60), 133.3 (C-30, C-50), 148.0 (C-10).
5.5. 4-Formylbenzenesulfonamide (4)
To a solution of 4-cyanobenzenesulfonamide 3 (5.85 g,
32.15 mmol) in formic acid (75%, 84 mL) was added Ra-
ney nickel (6.2 g). This stirred mixture was refluxed for
1 h and then filtered through Celite. The combined fil-
trate was concentrated to afford benzaldehyde 4 (5.1 g,
86%); mp 105–107 ꢂC; 1H NMR: d 7.55 (s, –NH2),
8.02 (d, J = 8.5 Hz, H-20, H-60), 8.08 (d, J = 8.5 Hz, H-
13
30, H-50), 10.1 (–CHO). C NMR: d 126.3 (C-20, C-
5.6.5. 4-(4-Dimethylamino-phenyliminomethyl)-benzene-
sulfonamide (31). Compound 31 was synthesized using
4-(dimethylamino)aniline (yield 59%); mp 246–248 ꢂC;
1H NMR: d 2.94 (s, –N(CH3)2), 6.76 (d, J = 8.5 Hz,
H-3, H-5), 7.33 (d, J = 8.5 Hz, H-2, H-6), 7.43 (s,
–NH2), 7.90 (d, J = 8.5 Hz, H-20, H-60), 8.04 (d,
J = 8.5 Hz, H-30, H-50), 8.73 (s, –NCH). 13C NMR: d
40.1 (–N(CH3)2), 112.4 (C-3, C-5), 122.7 (C-2, C-6),
126.0 (C-20, C-60), 128.2 (C-30, C-50), 138.9 (C-1),
139.6 (C-40), 145.1 (C-10), 149.8 (C-4), 153.2 (–NCH).
HR-MS m/z calcd for C15H17N3O2S 303.1042, found
303.1043.
60), 130.0 (C-30, C-50), 138.0 (C-40), 148.7 (C-10), 192.4
(C@O).
5.6. General procedure for the synthesis of 4-phenylimino-
methylbenzenesulfonamides
A mixture of 4-formylbenzenesulfonamide 4 and the
appropriate aniline (1.05 equiv) in methanol (2 mL)
was stirred in oil bath for 5 min at 150 ꢂC, and then al-
lowed to cool to room temperature. The crude product
was purified by recrystallization from isopropanol and

S.-J. Lin et al. / Bioorg. Med. Chem. 16 (2008) 2697–2706
2705
5.6.6. 4-(4-Hydroxy-phenyliminomethyl)-benzenesulfon-
5.7. Cyclooxygenase inhibition assays in human whole
blood (HWB)
amide (32). Compound 32 was synthesized using 4-ami-
nophenol (yield 75%); mp 242–244 ꢂC; 1H NMR: d 6.81
(d, J = 8.5 Hz, H-3, H-5), 7.26 (d, J = 8.5 Hz, H-2, H-6),
7.45 (s, –NH2), 7.91 (d, J = 8.0 Hz, H-20, H-60), 8.05 (d,
J = 8.0 Hz, H-30, H-50), 8.70 (s, –NCH). 13C NMR: d
115.7 (C-3, C-5), 122.8 (C-2, C-6), 126.1 (C-20, C-60),
128.5 (C-30, C-50), 139.2 (C-40), 141.9 (C-1), 145.5 (C-
10), 155.5 (–NCH), 156.8 (C-4). HR-MS m/z calcd for
C13H12N2O3S 276.0569, found 276.0570.
The assays for COX isozymes activity in human whole
blood were performed according to Patrignani
et al.18,19 In blood, thromboxane B2 (TxB2) production
from platelets is a substitute measure of COX-1 activity,
while PGE2 production is a substitute measure of COX-2
activity. Blood samples were divided in two parts for par-
allel experiments to test COX-1 and COX-2 inhibition.
Test compounds were dissolved and diluted in DMSO,
and 2 lL of each dilution of the test compound was
added into each well in duplicate. Then, 500 lL blood
aliquots were dispensed into each well and incubated at
37 ꢂC for 15 min with shaking. To induce COX-2, lipo-
polysaccharide (LPS, 2 lL of 5 mg/mL) was added to
each well, except the basal control 15 min after the addi-
tion of the test compounds. To stimulate COX-1, the cal-
cium ionophore A23187 (2 lL of 5 mM stock in DMSO)
was added to each well, except the basal control, 15 min
after the addition of the test compounds. At 1 h after
A23187 addition or 8 h after LPS addition, the blood
samples were transferred and centrifuged at 1000 ·g
for 3 min. The supernatants were collected and stored
at ꢀ80 ꢂC until ready for analysis. After reconstitution
with EIA buffer and appropriate dilution, the samples
were assayed for TxB2 (COX-1) and PGE2 (COX-2)
using EIA kits supplied by Cayman Chemical Co.
(Ann Arbor, MI, Cat. Nos.: 519031 and 514010). The
IC50 of the tested compounds was calculated from the
concentration–inhibition response curves.
5.6.7. 4-(4-Methoxy-phenyliminomethyl)-benzenesulfon-
amide (33). Compound 33 was synthesized using p-anisi-
1
dine (yield 76%); mp 207–209 ꢂC; H NMR: d 3.78 (s,
–OCH3), 7.00 (d, J = 8.5 Hz, H-3, H-5), 7.36 (d,
J = 8.5 Hz, H-2, H-6), 7.46 (s, –NH2), 7.93 (d,
J = 8.5 Hz, H-20, H-60), 8.07 (d, J = 8.5 Hz, H-30, H-
50), 8.74 (s, –NCH). 13C NMR: d 55.3 (–OCH3), 114.5
(C-3, C-5), 122.7 (C-2, C-6), 126.1 (C-20, C-60), 128.7
(C-30, C-50), 139.1 (C-40), 143.4 (C-1), 145.7 (C-10),
156.8 (–NCH), 158.4 (C-4). HR-MS m/z calcd for
C14H14N2O3S 290.0725, found 290.0725.
5.6.8. 4-(3,4-Dimethoxy-phenyliminomethyl)-benzenesul-
fonamide (34). Compound 34 was synthesized using 3,4-
dimethoxyaniline (yield 76%); mp 221–223 ꢂC; 1H
NMR: d 3.78 (s, 4-OCH3), 3.81 (s, 3-OCH3), 6.95 (dd,
J = 2.5, 8.5 Hz, H-6), 7.00 (d, J = 8.5 Hz, H-5), 7.06
(d, J = 2.5 Hz, H-2), 7.47 (s, –NH2), 7.93 (d,
J = 8.0 Hz, H-20, H-60), 8.07 (d, J = 8.0 Hz, H-30, H-
50), 8.77 (s, –NCH). 13C NMR: d 55.5 (4-OCH3), 55.7
(3-OCH3), 105.3 (C-2), 111.9 (C-5), 114.0 (C-6), 126.1
(C-20, C-60), 128.7 (C-30, C-50), 139.1 (C-40), 143.6 (C-
1), 145.7 (C-10), 148.1 (C-4), 149.2 (C-3), 156.8
(–NCH). HR-MS m/z calcd for C15H16N2O4S
320.0831, found 320.0832.
Acknowledgments
We thank the National Science Council of Taiwan for
Grants NSC-94-2320-B-077-005 (L.-M.Y.) and NSC-
95-2320-B-038-033 (S.-J.L.) and the National Research
Institute of Chinese Medicine for providing research
support (Grant NRICM-96-DMC-06).
5.6.9. 4-(4-Hydroxy-3-methoxycarbonyl-phenyliminom-
ethyl)-benzenesulfonamide (35). Compound 35 was syn-
thesized using methyl 5-aminosalicylate (yield 64%);
1
mp 183–185 ꢂC; H NMR: d 3.91 (s, –OCH3), 7.07 (d,
J = 8.5 Hz, H-5), 7.47 (s, –NH2), 7.61 (dd, J = 2.5,
8.5 Hz, H-6), 7.76 (d, J = 2.5 Hz, H-2), 7.93 (d,
J = 8.5 Hz, H-20, H-60), 8.09 (d, J = 8.5 Hz, H-30, H-
50), 8.78 (s, –NCH). 13C NMR: d 52.5 (–OCH3), 113.6
(C-3), 118.3 (C-5), 122.5 (C-2), 126.1 (C-20, C-60),
128.8 (C-30, C-50), 128.9 (C-6), 138.8 (C-40), 142.1 (C-
1), 145.9 (C-10), 158.0 (–NCH), 158.7 (C-4), 168.7
(C@O). HR-MS m/z calcd for C15H14N2O5S 334.0467,
found 334.0468.
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J = 8.0 Hz, H-2, H-6), 7.51 (s, –NH2), 7.96 (d,
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´

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