Synthesis and blood glucose lowering effect of novel pyridazinone substituted benzenesulfonylurea derivatives

Article abstract of DOI:10.1016/j.ejmech.2008.12.013

Fifteen novel pyridazinone substituted benzenesulfonylurea derivatives (3a-o) were synthesized from corresponding sulfonamides derivatives via novel carbamates (2a-e). These were characterized by elemental analysis and various spectroscopic methods viz. I

Full text of DOI:10.1016/j.ejmech.2008.12.013

European Journal of Medicinal Chemistry 44 (2009) 2673–2678
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and blood glucose lowering effect of novel pyridazinone substituted
benzenesulfonylurea derivatives
,
a
a
a
b
I.G. Rathish a, Kalim Javed a , Sameena Bano , Shamim Ahmad , M.S. Alam , K.K. Pillai
*
a Department of Chemistry, Faculty of Science, Jamia Hamdard (Hamdard University), New Delhi 110 062, India
b Department of Pharmacology, Faculty of Pharmacy, Jamia Hamdard (Hamdard University), New Delhi 110 062, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 July 2008
Received in revised form
29 November 2008
Accepted 5 December 2008
Available online 24 December 2008
Fifteen novel pyridazinone substituted benzenesulfonylurea derivatives (3a–o) were synthesized from
corresponding sulfonamides derivatives via novel carbamates (2a–e). These were characterized by
elemental analysis and various spectroscopic methods viz. IR, 1H NMR, 13C NMR and MS. Blood sugar
lowering effect of thirteen (3a–c, 3e, 3g–o) sulfonylurea derivatives at the dose of 20 mg/kg (p.o.) were
assessed using glucose tolerance test in normal and NIDDM (n2-STZ) rat models. All compounds except
3c, 3e and 3o almost completely prevented the rise of blood glucose of NIDDM rats as compared with
NIDDM control. While compounds 3c and 3o showed more than 50% prevention in the rise of blood
glucose levels. In glucose-fed normal rats these compounds at the same dose except 3e significantly
prevented the rise of blood glucose (more than 50%) when compared with control of glucose-fed normal
rats. From the results, novel compounds (3a–c, 3g–n) exhibited considerably potent blood glucose
lowering activity and may be used as lead compounds for developing new antidiabetic drugs. Some
structure–activity relationship was observed while varying nature of ‘Ar’ and ‘R’.
Keywords:
Pyridazinone
Sulfonylurea
Carbamate
Blood glucose lowering effect
Ó 2008 Published by Elsevier Masson SAS.
1. Introduction
from glucose by aldose reductase (AR) in polyol pathway. AR
converts glucose to sorbitol only at high glucose levels in plasma
Diabetes mellitus (DM) is one of the most daunting challenges
posed by chronic diseases resulting from insulin deficiency or
insulin resistance. Recent data show that approximately 135
million people suffer from diabetes mellitus worldwide, and that
this number will rise to almost 300 million by the year 2025. While
the rise will be of the order of 45% in developed countries, it will be
almost 200% in developing countries. India has 35 million diabetics.
As per WHO data the number would touch 50 million in 2020.
Generally DM is classified as Type I Insulin Dependent Diabetes
Mellitus (IDDM) caused by low or insufficient secretion of insulin
by pancreas and Type II Non-Insulin Dependent Diabetes Mellitus
(NIDDM) caused due to insufficient utilization of insulin [1,2].
NIDDM is the most common form of diabetes constituting nearly
90% of the diabetic population in any country.
and tissue in diabetes [3–5]. The result of clinical trials justifies the
importance of an improved glycemic control in diabetic patients in
order to prevent or at least to delay long-term complications. The
difficulty in obtaining normalization of blood glucose values has
underlined the importance of the search for new and effective
aldose reductase inhibitors (ARIs) to control the consequences of
elevated glucose levels and thereby delaying the onset and
retarding the progression of diabetic complications. There is need
to develop antidiabetic agents provided with ARI.
Over the last forty years oral therapy for type II has focused on
sulfonylureas and biguanides [6,7]. Sulfonylurea (SU) drugs
improve glucose levels by stimulating insulin secretion by the
pancreatic
b-cell. Recently compounds containing pyridazine
nucleus Chart 1 have been reported as AR inhibitors [8–10].
Therefore, it has been considered worthwhile to attach pyr-
idazinone ring to benzenesulfonylurea derivatives. In the present
study fifteen novel pyridazinone substituted benzenesulfonylurea
derivatives were synthesized from corresponding sulfonamide
derivatives via novel carbamates. These were characterized by
elemental analysis and various spectroscopic methods viz. IR, 1H
NMR, 13C NMR and MS. Oral antihyperglycemic efficacy of thirteen
out of fifteen sulfonylurea derivatives were assessed using an oral
glucose tolerance test in normal and NIDDM rat model.
Chronic diabetes is accompanied by complications such as
neuropathy, nephropathy, cataracts and retinopathy, which prac-
tically are not controlled by insulin. These complications are
considerably caused by accumulation of sorbitol, which is produced
* Corresponding author. Tel.: þ91 112 605 9688x5552.
E-mail addresses: kjavedchem@yahoo.co.in, kjaved@jamiahamdard.ac.in
(K. Javed).
0223-5234/$ – see front matter Ó 2008 Published by Elsevier Masson SAS.
doi:10.1016/j.ejmech.2008.12.013

2674
I.G. Rathish et al. / European Journal of Medicinal Chemistry 44 (2009) 2673–2678
H
N
In the IR spectra of 3a–o five bands characteristic of sulfonylurea
moiety out of which three bands for NH (3390–3305 cmꢁ1, 3256–
3102 cmꢁ1 and 3099–3037 cmꢁ1) and two bands for carbonyl
function of ureido group were observed (1716–1670 cmꢁ1 and
1545–1517 cmꢁ1). Apart from these a band for carbonyl of pyr-
idazinone (1681–1654 cmꢁ1), a band for C]N of pyridazinone
(1607–1589 cmꢁ1) and two bands for SO2No (1350–1331 cmꢁ1 and
1172–1136 cmꢁ1) were also observed. The structures were further
established by proton NMR spectral data. A singlet for R-NH was
O
N
(
)
n
1-3
observed at d 5.68–6.56. Two doublets at d 7.16–7.65 and d 8.13–8.20
1: n = 1
2: n = 2
3: n = 3
(J ¼ 9.5–9.8 Hz) for the pyridazinone ring protons were also
observed.
In IR spectra of 2a–e bands at 3310–3042 cmꢁ1 (NH), 1753–
1736 cmꢁ1 (C]O of carbamate), 1668–1656 cmꢁ1 (cyclic carbonyl),
1356–1349 cmꢁ1 and 1167–1160 cmꢁ1 (SO2N), 1240–1222 cmꢁ1
and 1094–1089 cmꢁ1 (C–O of carbamate) were identified. The 1H
NMR spectral data are in accordance with the structure of carba-
Chart 1. Structure of some compounds possessing pyridazinone nucleus reported as
AR inhibitors.
2. Results and discussion
mates. A triplet at
assigned to –OCH2CH3. Pyridazinone ring protons were observed at
7.23–7.29 and
8.17–8.23 (J ¼ 9.6–9.8 Hz). Only two out of the five
carbamates exhibited a broad singlet for NH (exchangeable proton)
at 12.18 (2c) and at 12.27 (2d).
d 1.06–1.13 and a quartet at d 4.04–4.37 can be
2.1. Chemistry
d
d
The synthetic route used to synthesize title compounds (3a–o)
is outlined in Scheme 1. The pyridazinone substituted benzene-
sulfonamide derivatives (1a–e) synthesized through reported
method [11] were converted to corresponding novel carbamates
(2a–e) by refluxing with ethyl chloroformate in dry acetone con-
taining anhydrous K2CO3. The resulting carbamates were subse-
quently condensed with desired primary amines to give novel
pyridazinone substituted benzenesulfonylurea derivatives (3a–o).
The structures of sulfonylurea derivatives (3a–o) were deter-
mined on the basis of elemental analysis and various spectroscopic
methods such as IR, 1H NMR, 13C NMR and MS, while carbamates
(2a–e) were characterized by IR, 1H NMR, MS and elemental anal-
ysis. Elemental analysis (C, H, N and S) data were within ꢀ 0.4% of
the theoretical values.
d
d
2.2. Blood glucose lowering effect
In the present study streptozotocin injection in neonatal rats
induces in adult rats defects similar to those observed in mild type-
II human diabetes (Non-insulin dependent diabetes mellitus)
successfully [12]. NIDDM rats showed significantly higher glucose
levels of fasting (>140 mg/dl) and glucose (2 g/kg) fed levels
(>200 mg/dl two hours after oral administration of glucose). Oral
antihyperglycemic efficacies of thirteen compounds (3a–c, 3e, 3g–
o) were assessed using an oral glucose tolerance test in normal and
NIDDM rat model. The marketed sulfonylurea drug gliclazide was
selected as positive control. The sugar lowering effect of these
compounds is presented in Table 1.
The compounds (3a–c, 3e, 3g–o) except 3c, 3e and 3o at 20 mg/
kg b.w (p.o.) almost completely prevented the rise of blood glucose
of NIDDM rats as compared with NIDDM control. While
compounds 3c and 3o showed more than 50% reduction in the rise
of blood glucose levels. In glucose-fed normal rats these
compounds at the same dose except 3e significantly prevent the
rise of blood glucose (more than 50%) when compared with control
of glucose-fed normal rats.
O
Ar
O
Ar
N
N
N
N
(i)
The compound 3a with phenyl group at C6 of pyridazinone
nucleus and propyl moiety in the side chain –NHR is the most active
compound. The activity of 3a became less when the bulk of ‘R’ was
increased (3a–c). Introduction of Cl at para position of phenyl group
caused slightly reduction in the activity (3k vs. 3a). Activity of 3k
was further reduced when the bulk of ‘R’ was increased (3k–n).
Compound 3f with methoxyl moiety at para of phenyl group
exhibited inferior activity. Presence of methyl moiety in phenyl
group caused reduction in the activity (3g vs. 3a, 3o vs. 3m). On the
basis of these observations the SAR may be summarized as:
SO2NH2
1a-e
SO2NHCOOC2H5
2a-e
1a, 2a, 3a-d: Ar = -C6H5
(ii)
1b, 2b, 3e, 3f: Ar = 4-OCH3C6H4
1c, 2c, 3g-j: Ar = 4-CH3C6H4
1d, 2d, 3k-n: Ar = 4-ClC6H4
1e, 2e,3o: Ar = 4-Cl,3-CH3C6H3
O
Ar
N
N
- In the side chain –NHR, less bulky ‘R’ seems more favourable
for good activity.
- Presence of electron releasing moiety in phenyl group may
cause the reduction in the activity.
3a, g, k: R = n-C3H7
3b, e, h, l: R = n-C4H9
3c, i, f, m, o: R = -C6H11
3d, j, n: R = -CH2C6H5
It is well known that clinically used sulfonylureas exert anti-
hyperglycemia action by stimulating insulin secretion by binding to
and inhibiting the ATP-dependent Kþ channels in the ß-cell
membrane, resulting ultimately in an opening of Caþ channels [13].
Since the synthesized derivatives are also sulfonylurea derivatives,
SO2NHCONHR
3a-o
Scheme 1. Reagent and conditions: (i) ClCOOC2H5, K2CO3, dry acetone, REFLUX
18–24H. (ii) RNH2, toluene, reflux 3–4h.

I.G. Rathish et al. / European Journal of Medicinal Chemistry 44 (2009) 2673–2678
2675
Table 1
Effect of sulfonylurea derivatives on blood glucose levels in normal and n2-STZ rats.
Compound Ar/R Blood glucose level (mg/dl) in normal rats Percent inhibition in
Blood glucose level (mg/dl) in n2-STZ rats Percent inhibition in
the rise of blood
the rise of blood glucose
level in normal rats
Just prior to
glucose loading
(2 g/kg)
After 90 min of
glucose loading
(2 g/kg)
Just prior to
glucose loading
(2 g/kg)
After 90 min of
glucose loading
(2 g/kg)
glucose level in
n2-STZ rats
Control
Gliclazide
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
–
–
146.3 ꢀ 10.2
135.0 ꢀ 9.1
143.2 ꢀ 11.3
138.6 ꢀ 14.2
140.3 ꢀ 13.2
ND
220.4 ꢀ 5.6
109.0 ꢀ 10.2
125.0 ꢀ 11.6
130.2 ꢀ 14.6
150.5 ꢀ 17.2
ND
–
135
77.3 ꢀ 4.3
65.7 ꢀ 3.2
73.5 ꢀ 5.7
75.6 ꢀ 4.3
70.0 ꢀ 2.3
ND
113.2 ꢀ 5.2
63.3 ꢀ 5.2
81.7 ꢀ 5.7
87.3 ꢀ 4.5
87.2 ꢀ 5.4
ND
–
106.7
77.2
67.4
52.1
ND
C6H5/C3H7
C6H5/C4H9
C6H5/C6H11
C6H5/CH2C6H5
4-OCH3C6H4/C4H9
4-OCH3C6H4/C6H11
4-CH3C6H4/C3H7
4-CH3C6H4/C4H9
4-CH3C6H4/C6H11
124.6
111.3
86.2
ND
25.6
ND
140.2 ꢀ 10.2
195.3 ꢀ 12.1
77.5 ꢀ 5.5
97.7 ꢀ 6.2
43.7
ND
ND
ND
ND
ND
142.2 ꢀ 11.3
146.6 ꢀ 14.3
137.7 ꢀ 13.2
135.5 ꢀ 12.2
140.0 ꢀ 15.2
130.0 ꢀ 10.2
125.0 ꢀ 12.2
120.5 ꢀ 10.2
140.3 ꢀ 11.7
136.6 ꢀ 9.7
139.0 ꢀ 15.2
180.4 ꢀ 11.1
109
75.3 ꢀ 5.8
76.6 ꢀ 5.7
77.4 ꢀ 6.7
76.2 ꢀ 4.5
75.3 ꢀ 5.8
77.7 ꢀ 6.8
72.0 ꢀ 3.3
74.0 ꢀ 4.3
78.5 ꢀ 6.5
82.3 ꢀ 6.3
81.4 ꢀ 5.8
84.6 ꢀ 6.1
88.8 ꢀ 5.2
84.5 ꢀ 6.3
89.9 ꢀ 7.2
86.7 ꢀ 5.4
87.8 ꢀ 4.7
92.4 ꢀ 5.8
80.5
86.6
79.9
64.9
74.3
66
59
61.6
62.1
108.9
110.4
119.3
121.7
100.1
114.3
111.1
55.2
4-CH3C6H4/CH2-C6H5 139.3 ꢀ 13.9
4-ClC6H4/C3H7
4-ClC6H4/C4H9
4-ClC6H4/C6H11
4-ClC6H4/CH2-C6H5
136.6 ꢀ 13.6
140.4 ꢀ 16.8
147.2 ꢀ 9.7
147.2 ꢀ 10.2
3o
4-Cl, 3-CH3C6H3/C6H11 147.2 ꢀ 10.2
Values are mean ꢀ SEM of 6 animals.
ND ¼ not determined.
it may be assumed that the blood glucose lowering effect of these
3042 (NH),1753 (C]O of carbamate),1664 (cyclic carbonyl),1351 and
derivatives (3a–c, 3g–n) is related to a stimulation of
b-cells.
1167 (SO2N), 1230 and 1089 (C–O of carbamate); 1H NMR (300 MHz,
DMSO-d6, d): 1.06 (3H, t, CH3), 4.11 (2H, q, OCH2), 7.24 (1H, d,
J ¼ 9.7 Hz, H-4), 7.50–7.94 (9H, m, Ar–H), 8.18 (1H, d, J ¼ 9.7 Hz, H-5);
3. Conclusions
FAB-MS (m/z): 399 [Mþ].
Our data suggested that eleven novel sulfonylurea derivatives
(3a–c, 3g–n) at the dose of 20 mg/kg exhibited considerably potent
blood glucose lowering activity. These derivatives may be used as
lead compounds for developing new antidiabetic drugs.
4.1.1.2. Ethyl({4-[6-(4-methoxyphenyl)-3-oxopyridazin-2-yl]phe-
nyl}sulfonyl)carbamate (2b). Yield ¼ 27.7%; m.p. 217–218 ꢂC; IR
nmax (KBr, in cmꢁ1): 3310 (NH), 1747 (C]O of carbamate), 1656
(cyclic carbonyl), 1349 and 1161 (SO2N), 1222 and 1094 (C–O of
carbamate); 1H NMR (300 MHz, DMSO-d6,
d): 1.06 (3H, t, CH3),
4. Experimental protocols
3.82 (3H, s, OCH3), 4.37 (2H, q, OCH2), 7.04–8.16 (10H, m, Ar–H,
H-4 and H-5); FAB-MS (m/z): 429 [Mþ].
Melting points were determined by open capillary tubes and are
uncorrected. All the Fourier Transform Infra Red (FTIR) spectra were
recorded on Bio-rad FTS-135 spectrophotometer using KBr pellets;
nmax values are given in cmꢁ1. 1H NMR and 13C NMR spectra were
recorded on Bruker Spectrospin DPX 300 MHz and Bruker Spec-
trospin DPX 75 MHz spectrometer respectively using DMSO as
a solvent and trimethylsilane (TMS) as an internal standard.
4.1.1.3. Ethyl({4-[6-(4-methylphenyl)-3-oxopyridazin-2-yl]phenyl}
sulfonyl)carbamate (2c). Yield ¼ 71.7%; m.p. 187–188 ꢂC; IR nmax
(KBr, in cmꢁ1): 3305 (NH), 1736 (C]O of carbamate), 1656 (cyclic
carbonyl), 1351 and 1166 (SO2N), 1240 and 1092 (C–O of carba-
mate); 1H NMR (300 MHz, DMSO-d6,
d): 1.13 (3H, t, CH3), 2.37 (3H,s,
ArCH3), 4.05 (2H, q, OCH2), 7.23 (1H, d, J ¼ 9.7 Hz, H-4), 7.33 (2H, d,
J ¼ 7.2 Hz, Ar–H), 7.86 (2H, d, J ¼ 7.5 Hz, Ar–H) 8.02 (4H, m, Ar–H),
8.17 (1H, d, J ¼ 9.7 Hz, H-5), 12.18 (1H, brs, SO2NH); FAB-MS (m/z):
413 [Mþ].
Chemical shifts are given in
d (ppm) scale and coupling constants
(J values) are expressed in Hz. Mass spectra (MS) were scanned by
affecting FAB ionization JEOL-JMS-DX 303 system, equipped with
direct inlet probe system. The m/z values of the more intense peaks
are mentioned. Purity of the compounds was checked on TLC plates
(silica gel G), which were visualized by exposing to iodine vapours.
Elemental analysis was carried out on CHNS Elementar (Vario EL III).
4.1.1.4. Ethyl({4-[6-(4-chlorophenyl)-3-oxopyridazin-2-yl]phenyl}
sulfonyl)carbamate (2d). Yield ¼ 41.2%; m.p. 213–214 ꢂC; IR nmax
(KBr, in cmꢁ1): 3065 (NH), 1753 (C]O of carbamate), 1668 (cyclic
carbonyl), 1356 and 1167 (SO2N), 1224 and 1092 (C–O of carba-
4.1. Chemistry
mate); 1H NMR (300 MHz, DMSO-d6,
d): 1.12 (3H, t, CH3), 4.06 (2H,
q, OCH2), 7.29 (1H, d, J ¼ 9.7 Hz, H-4), 7.61 (2H, d, J ¼ 8.2 Hz, Ar–H),
7.92–8.06 (6H, m, Ar–H), 8.23 (1H, d, J ¼ 9.8 Hz, H-5), 12.27 (1H, brs,
SO2NH); FAB-MS (m/z): 434 [M þ 1], 420.
4.1.1. General procedure for the preparation of carbamates (2a–e)
A mixture of appropriate pyridazinone (1a–e) (0.01 mol), ethyl
chloroformate (0.013 mol), and anhydrous potassium carbonate
(2 g) in dry acetone (300–500 ml) was refluxed for 18 h. Acetone
was removed by distillation under reduced pressure; the residue
left was suspended in water (100 ml) and neutralized with acetic
acid. The product separated out was filtered and washed with
distilled water. The residue was dried and crystallized from meth-
anol or acetone.
4.1.1.5. Ethyl({4-[6-(4-chloro-3-methylphenyl)-3-oxopyridazin-2-yl]
phenyl}sulfonyl) carbamate (2e). Yield ¼ 26.6%; m.p. 203–204 ꢂC; IR
nmax (KBr, in cmꢁ1): 3310 (NH), 1741 (C]O of carbamate), 1659
(cyclic carbonyl), 1350 and 1160 (SO2N), 1231 and 1092 (C–O of
carbamate); 1H NMR (300 MHz, DMSO,
d): 1.13 (3H, t, CH3), 2.40
(3H, s, ArCH3), 4.04 (2H, q, OCH2), 7.25 (1H, d, J ¼ 9.6 Hz, H-4), 7.55
(1H, d, J ¼ 8.2 Hz, Ar–H), 7.80 (1H, d, J ¼ 7.8 Hz, Ar–H), 7.95–8.03
(5H, m, Ar–H), 8.18 (1H, d, J ¼ 9.6 Hz, H-5); FAB-MS (m/z): 448 [Mþ].
4.1.1.1. Ethyl({4-[6-phenyl-3-oxopyridazin-2-yl]phenyl}sulfonyl)carba-
mate (2a). Yield ¼ 32.7%; m.p. 206–207 ꢂC; IR nmax (KBr, in cmꢁ1):

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I.G. Rathish et al. / European Journal of Medicinal Chemistry 44 (2009) 2673–2678
4.1.2. General procedure for the preparation of pyridazinone
substituted benzenesulfonylurea (3a–o)
nmax (KBr, in cmꢁ1): 3097 (NH of ureido group), 1517 (C]O of urea),
1681 (cyclic carbonyl), 1589 (C]N), 1333 and 1136 (SO2N); 1H NMR
On complete dissolution of appropriate carbamates (2a–o)
(0.001 mol) in boiling toluene (25–75 ml) was added the desired
primaryamine(0.0011 mol)dropwise. Themixturewassubsequently
refluxed for further 3–4 h and cooled. The product, which precipi-
tated out on cooling, was filtered and crystallized from methanol.
(300 MHz, DMSO-d6, d): 1.00–1.87 (10H, m, cyclohexyl protons),
3.81 (3H, s, OCH3), 5.70 (1H, br s, NH–C6H11), 7.04 (2H, d, J ¼ 7.9 Hz,
Ar–H), 7.16 (1H, d, J ¼ 9.6 Hz, H-4), 7.62–7.91 (6H, m, Ar–H), 8.13
(1H, d, J ¼ 9.5 Hz, H-5); 13C NMR (75 MHz, DMSO-d6,
d, ppm): 24.81
(2 ꢃ CH2), 25.40 (CH2), 33.34 (2 ꢃ CH2), 49.35 (CH–NH), 144.10
(C]N of pyridazinone), 158.47 (C]O), 159.36 (C]O), 160.46 (Ar C–
O–C); FAB-MS (m/z): 482 [Mþ], 483 [M þ 1], 460.
4.1.2.1. 1-[4-(6-Phenyl-3-oxopyridazin-2-yl)benzenesulfonyl]-3-(1-
propyl)urea (3a). M.p. 187–188 ꢂC; yield 43.5%; IR nmax (KBr, in
cmꢁ1): 3390, 3192 and 3099 (NH of ureido group), 1716 and 1522
(C]O of urea), 1658 (cyclic carbonyl), 1596 (C]N), 1332 and 1162
4.1.2.7. 1-[4-{6-(4-Methylphenyl)-3-oxopyridazin-2-yl}benzenesulfon-
yl]-3-(1-propyl)urea (3g). M.p. 167–168 ꢂC; yield 48%; IR nmax (KBr,
in cmꢁ1): 3351, 3102 (NH of ureido group), 1670 (cyclic carbonyl),
1544 (C]O of urea), 1604 (C]N), 1350 and 1168 (SO2N); 1H NMR
(SO2N); 1H NMR (300 MHz, DMSO-d6,
d): 0.78 (3H, t, CH3), 1.36 (2H,
m, –CH2–CH2–CH3), 2.92 (2H, m, HN–CH2–CH2–CH3), 6.54 (1H, brs,
NH–C3H7), 7.24 (1H, d, J ¼ 9.8 Hz, H-4), 7.50 (3H, m, Ar–H), 7.96 (4H,
m, Ar–H), 8.04 (2H, d, J ¼ 8.5 Hz, Ar–H), 8.18 (1H, d, J ¼ 9.8 Hz, H-5),
(300 MHz, DMSO-d6, d): 0.77 (3H, t, CH3), 1.35 (2H, m, –CH2–CH2–
CH3), 2.36 (3H, s, C6H5CH3), 2.92 (2H, m, HN–CH2–CH2–CH3), 6.55
(1H, t, NH–C3H7), 7.22 (1H, d, J ¼ 9.8 Hz, H-4), 7.32 (2H, d, J ¼ 7.9 Hz,
Ar–H), 7.85 (2H, d, J ¼ 8.0 Hz, Ar–H), 7.95 (2H, d, J ¼ 8.6 Hz, Ar–H),
8.04 (2H, d, J ¼ 8.6 Hz, Ar–H), 8.16 (1H, d, J ¼ 9.8 Hz, H-5), 10.70 (1H,
10.61 (1H, br s, SO2NH); 13C NMR (75 MHz, DMSO-d6,
d, ppm): 11.12
(CH3), 22.45 (CH2), 40.96 (CH2NH), 144.98 (C]N of pyridazinone),
151.34 (C]O), 158.62 (C]O); FAB-MS (m/z): 412 [Mþ], 413 [M þ 1].
br s, SO2NH); 13C NMR (75 MHz, DMSO-d6,
d, ppm): 11.13 (CH3),
4.1.2.2. 1-[4-(6-Phenyl-3-oxopyridazin-2-yl)benzenesulfonyl]-3-(1-
butyl)urea (3b). M.p. 177–178 ꢂC; yield 37.4%; IR nmax (KBr, in
cmꢁ1): 3320, 3256 and 3037 (NH of ureido group), 1691 and 1535
(C]O of urea), 1669 (cyclic carbonyl), 1595 (C]N), 1337 and 1172
20.89 (ArCH3), 22.47 (CH2), 41.0 (CH2NH), 145.04 (C]N of pyr-
idazinone), 151.4 (C]O), 158.64 (C]O); FAB-MS (m/z): 426 [Mþ],
427 [M þ 1], 368, 342 and 278.
(SO2N); 1H NMR (300 MHz, DMSO-d6,
d): 0.82 (3H, t, CH3), 1.19 (2H,
4.1.2.8. 1-[4-{6-(4-Methylphenyl)-3-oxopyridazin-2-yl}benzenesulfon-
yl]-3-(1-butyl)urea (3h). M.p. 201–202 ꢂC; yield 47%; IR nmax (KBr, in
cmꢁ1): 3305 and 3217 (NH of ureido group), 1697 and 1536 (C]O of
urea), 1675 (cyclic carbonyl), 1604 (C]N), 1334 and 1162 (SO2N); 1H
m, CH2–CH2–CH2–CH3) 1.31 (2H, m, HN–CH2–CH2–CH2–CH3), 2.96
(2H, m, HN–CH2–CH2–CH2–CH3), 6.51 (1H, br s, NH–C4H9), 7.23 (1H,
d, J ¼ 9.7 Hz, H-4), 7.51 (3H, m, Ar–H), 7.96 (4H, m, Ar–H), 8.04 (2H,
d, J ¼ 8.5 Hz, Ar–H), 8.17 (1H, d, J ¼ 9.8 Hz, H-5), 10.67 (1H, brs,
NMR (300 MHz, DMSO-d6, d): 0.81 (3H, t, CH3), 1.19 (2H, m, CH2–
SO2NH); 13C NMR (75 MHz, DMSO-d6,
d
, ppm): 13.57 (CH3), 19.34
CH2–CH2–CH3) 1.31 (2H, m, HN–CH2–CH2–CH2–CH3), 2.37 (3H, s,
C6H5CH3), 2.96 (2H, m, HN–CH2–CH2–CH2–CH3), 6.52 (1H, br s, NH–
C4H9), 7.22 (1H, d, J ¼ 9.8 Hz, H-4), 7.32 (2H, d, J ¼ 7.9 Hz, Ar–H), 7.85
(2H, d, J ¼ 8.0 Hz, Ar–H), 7.95 (2H, d, J ¼ 8.6 Hz, Ar–H), 8.04 (2H, d,
J ¼ 8.6 Hz, Ar–H), 8.15 (1H, d, J ¼ 9.8 Hz, H-5),10.30 (1H, br s, SO2NH);
(CH3CH2), 31.26 (CH2CH2NH), 144.95 (C]N of pyridazinone), 151.33
(C]O), 158.60 (C]O); FAB-MS (m/z): 426 [Mþ], 427 [M þ 1].
4.1.2.3. 1-[4-(6-Phenyl-3-oxopyridazin-2-yl)benzenesulfonyl]-3-(cyclo-
hexyl)urea (3c). M.p. 261–262 ꢂC; yield ¼ 15.5%; IR nmax (KBr, in
cmꢁ1): 3312 and 3163 (NH of ureido group), 1656 (cyclic carbonyl),
1542 (C]O of urea), 1340 and 1166 (SO2N); 1H NMR (300 MHz,
13C NMR (75 MHz, DMSO-d6,
d, ppm): 13.61 (CH3), 19.41 (CH3CH2),
20.90 (ArCH3), 31.33 (CH2CH2NH), 145.07 (C]N of pyridazinone),
151.44 (C]O), 158.66 (C]O); FAB-MS (m/z): 440 [Mþ], 441 [M þ 1],
368, 342 and 278.
DMSO-d6, d): 1.01–1.88 (10H, m, cyclohexyl protons), 5.68 (1H, brs,
NH–C6H11), 7.18–8.20 (11H, m, Ar–H, H-4 and H-5); FAB-MS (m/z):
452 [Mþ], 453 [M þ 1].
4.1.2.9. 1-[4-{6-(4-Methylphenyl)-3-oxopyridazin-2-yl}benzenesulfon-
yl]-3-(cyclohexyl)urea (3i). M.p. 189–190 ꢂC; yield ¼ 55.7%; IR nmax
(KBr, in cmꢁ1): 3367, 3250 and 3080 (NH of ureido group), 1675
(cyclic carbonyl), 1520 (C]O of urea), 1602 (C]N), 1338 and
4.1.2.4. 1-[4-(6-Phenyl-3-oxopyridazin-2-yl)benzenesulfonyl]-3-(ben-
zyl)urea (3d). M.p. 201–202 ꢂC; yield ¼ 19.5%; IR nmax (KBr, in
cmꢁ1): 3330 (NH of ureido group), 1699 and 1523 (C]O of urea),
1655 (cyclic carbonyl), 1589 (C]N), 1335 and 1164 (SO2N); 1H NMR
1159 (SO2N); 1H NMR (300 MHz, DMSO-d6,
d): 1.09–1.88 (10H, m,
cyclohexyl protons), 2.35 (3H, s, C6H5CH3), 6.13 (1H, brs, NH–C6H11),
(300 MHz, DMSO-d6,
d
): 4.16 (2H, d, J ¼ 4.9 Hz, CH2–C6H5), 6.97–
7.30 (2H, m, Ar–H), 7.65 (1H, d, J ¼ 9.6 Hz, H-4), 7.83–7.94 (6H, m,
8.02 (15H, m, Ar–H and H-4), 8.19 (1H, d, J ¼ 9.8 Hz, H-5); FAB-MS
Ar–H), 8.14 (1H, d, J ¼ 9.6 Hz, H-5); 13C NMR (75 MHz, DMSO-d6,
d,
(m/z): 460 [Mþ], 461 [M þ 1].
ppm): 20.90 (ArCH3), 24.58 (2 ꢃ CH2), 25.24 (CH2), 32.83 (2 ꢃ CH2),
49.44 (CH–NH), 144.61 (C]N of pyridazinone), 154.95 (C]O),
158.66 (C]O); FAB-MS (m/z): 466 [Mþ], 467 [M þ 1], 385, 368, 342
and 278.
4.1.2.5. 1-[4-{6-(4-Methoxyphenyl)-3-oxopyridazin-2-yl}benzene-
sulfonyl]-3-(1-butyl)urea (3e). M.p. 167–168 ꢂC; yield ¼ 41.1%; IR
nmax (KBr, in cmꢁ1): 3313, 3243 and 3062 (NH of ureido group),1677
and 1518 (C]O of urea), 1654 (cyclic carbonyl), 1607 (C]N), 1340
4.1.2.10. 1-[4-{6-(4-Methylphenyl)-3-oxopyridazin-2-yl}benzenesulf-
onyl]-3-(benzyl)urea (3j). M.p. 209–210 ꢂC; yield ¼ 34%; IR nmax
(KBr, in cmꢁ1): 3345, 3247 and 3066 (NH of ureido group), 1701 and
1527 (C]O of urea), 1676 (cyclic carbonyl), 1602 (C]N), 1333 and
and 1170 (SO2N); 1H NMR (300 MHz, DMSO-d6,
d): 0.83 (3H, t, CH3),
1.20 (2H, m, CH2–CH2–CH2–CH3) 1.31 (2H, m, HN–CH2–CH2–CH2–
CH3), 2.95 (2H, m, HN–CH2–CH2–CH2–CH3), 3.82 (3H, s, OCH3), 6.54
(1H, brs, NH–C6H11), 7.05 (2H, d, J ¼ 8.1 Hz, Ar–H), 7.21 (1H, d,
J ¼ 9.7 Hz, H-4), 7.90–8.04 (6H, m, Ar–H), 8.16 (1H, d, J ¼ 9.8 Hz, H-
1162 (SO2N); 1H NMR (300 MHz, DMSO-d6,
d
): 2.37 (3H, s,
C6H5CH3), 4.18 (2H, s, CH2–C6H5), 7.07–8.19 (15H, m, Ar–H, H-4 and
H-5), 10.92 (1H, br s, SO2NH); 13C NMR (75 MHz, DMSO-d6,
, ppm):
5); 13C NMR (75 MHz, DMSO-d6,
d, ppm): 13.58 (CH3), 19.36
d
(CH3CH2), 31.28 (CH2CH2NH), 55.36 (OCH3) 145.03 (C]N of pyr-
idazinone), 151.40 (C]O), 158.51 (C]O), 160.62 (Ar C–O–C); FAB-
MS (m/z): 456 [Mþ].
20.85 (ArCH3), 42.78 (ArCH2), 144.98 (C]N of pyridazinone), 151.76
(C]O), 158.56 (C]O); FAB-MS (m/z): 474 [Mþ], 475 [M þ 1], 441,
342 and 262.
4.1.2.6. 1-[4-{6-(4-Methoxyphenyl)-3-oxopyridazin-2-yl}benzene-
sulfonyl]-3-(cyclohexyl)urea (3f). M.p. 269–270 ꢂC; yield ¼ 15%; IR
4.1.2.11. 1-[4-{6-(4-Chlorophenyl)-3-oxopyridazin-2-yl}benzenesulf-
onyl]-3-(1-propyl)urea (3k). M.p. 177–178 ꢂC; yield 30%; IR nmax

I.G. Rathish et al. / European Journal of Medicinal Chemistry 44 (2009) 2673–2678
2677
(KBr, in cmꢁ1): 3310, 3236 and 3041 (NH of ureido group), 1698 and
4.2.1. Induction of non-insulin dependent diabetes mellitus in rats
1534 (C]O of urea), 1673 (cyclic carbonyl), 1600 (C]N), 1335 and
Healthy albino female wistar rats were kept for breeding. To
induce NIDDM, streptozotocin (STZ) (100 mg/kg) freshly dissolved
in citrate buffer solution (0.1 M, pH 4.5) was administered intra-
peritoneally to 2-day old pups weighing 6–8 g. The pups were
weaned for 4 weeks and separated thereafter from their mothers.
Male and female rats were separately housed with food and water
ad libitum. When the rats were 12 weeks old the animals were
checked for fasting glucose levels. The animals showing fasting
glucose levels >140 mg/dl and 200 mg/dl 2 h after 2 g/kg oral
challenge of glucose were considered as diabetic.
1168 (SO2N); 1H NMR (300 MHz, DMSO-d6,
d): 0.77 (3H, t, CH3), 1.35
(2H, m, –CH2–CH2–CH3), 2.91 (2H, m, HN–CH2–CH2–CH3), 6.56 (1H,
t, NH–C3H7), 7.25 (1H, d, J ¼ 9.8 Hz, H-4), 7.58 (2H, d, J ¼ 8.5 Hz, Ar–
H), 7.94–8.05 (6H, m, Ar–H), 8.19 (1H, d, J ¼ 9.8 Hz, H-5); 13C NMR
(75 MHz, DMSO-d6,
d, ppm): 11.15 (CH3), 22.49 (CH2), 41.02
(CH2NH), 144.92 (C]N of pyridazinone), 151.46 (C]O), 158.61
(C]O); FAB-MS (m/z): 447 [Mþ], 391 and 362.
4.1.2.12. 1-[4-{6-(4-Chlorophenyl)-3-oxopyridazin-2-yl}benzenesulf-
onyl]-3-(1-butyl)urea (3l). M.p. 207–208 ꢂC; yield 38%; IR nmax (KBr,
in cmꢁ1): 3313, 3236 and 3063 (NH of ureido group), 1670 and 1542
(C]O of urea), 1673 (cyclic carbonyl), 1602 (C]N), 1337 and 1164
4.2.2. Effect of synthesized compounds on oral glucose tolerance in
diabetic (n2-STZ) rats
(SO2N); 1H NMR (300 MHz, DMSO-d6,
d): 0.82 (3H, t, CH3), 1.20 (2H,
Albino rats (either sex) of wistar strain weighing 160–200 g
were fasted overnight and classified into groups of six animals each.
Group I served as control received vehicle (1% CMC in distilled
water) in a volume of 10 ml/kg. The reference drug gliclazide
(20 mg/kg) and synthesized compounds (3a–c, 3e, 3g–o) in the
dose of 20 mg/kg suspended in vehicle were administered p.o. in
a volume of 10 ml/kg to respective groups. All the animals were
given glucose (2 g/kg p.o.) 15 min after dosing. Blood samples were
collected from the retro-orbital plexus just prior to and 90 min after
the glucose loading and glucose levels were measured (Table 1).
m, CH2–CH2–CH2–CH3) 1.31 (2H, m, HN–CH2–CH2–CH2–CH3), 2.93
(2H, m, HN–CH2–CH2–CH2–CH3), 6.43 (1H, br s, NH–C4H9), 7.24
(1H, d, J ¼ 9.8 Hz, H-4), 7.56 (2H, d, J ¼ 8.4 Hz, Ar–H), 7.90 (2H, d,
J ¼ 8.4 Hz, Ar–H), 7.99 (4H, m, Ar–H), 8.18 (1H, d, J ¼ 9.8 Hz, H-5). 13C
NMR (75 MHz, DMSO-d6, d, ppm): 13.64 (CH3), 19.42 (CH3CH2),
31.34 (CH2CH2NH), 144.93 (C]N of pyridazinone), 151.49 (C]O),
158.64 (C]O); FAB-MS (m/z): 461 [Mþ], 388 and 362.
4.1.2.13. 1-[4-{6-(4-Chlorophenyl)-3-oxopyridazin-2-yl}benzenesulf-
onyl]-3-(cyclohexyl)urea (3m). M.p. 281–282 ꢂC; yield ¼ 38%; IR
nmax (KBr, in cmꢁ1): 3308, 3248 and 3066 (NH of ureido group),
1703 and 1544 (C]O of urea), 1681 (cyclic carbonyl), 1601 (C]N),
4.2.3. Effect of synthesized compounds on oral glucose tolerance in
normal rats
The same protocol as mentioned in above experiment was
adopted for this experiment. Instead of n2-STZ rats, normal rats
were used (Table 1).
1344 and 1168 (SO2N); 1H NMR (300 MHz, DMSO-d6,
d
): 1.10–1.85
(10H, m, cyclohexyl protons), 6.39 (1H, br s, NH–C6H11), 7.23 (1H, d,
J ¼ 9.8 Hz, H-4), 7.55 (2H, d, J ¼ 8.5 Hz, Ar–H), 7.90–8.02 (6H, m, Ar–
H), 8.16 (1H, d, J ¼ 9.8 Hz, H-5); 13C NMR (75 MHz, DMSO-d6,
d,
ppm): 24.61 (2 ꢃ CH2), 25.29 (CH2), 33.0 (2 ꢃ CH2), 49.40 (CH–NH),
143.95 (C]N of pyridazinone),156.5 (C]O),158.59 (C]O); FAB-MS
(m/z): 487 [Mþ], 405, 391, 362.
4.2.4. Blood glucose estimation
The blood glucose level was assayed by an enzymatic colori-
metric method using a commercially available glucose oxidase–
peroxidase (GOD–POD) kit purchased from Span diagnostics Ltd.,
Surat, India. Glucose oxidase (GOD) oxidizes glucose to gluconic
acid and hydrogen peroxide. In presence of enzyme peroxidase,
released hydrogen peroxide is coupled with phenol and 4-amino-
antipyrine (4-AAP) to form coloured quinoneimine dye. Absor-
bance of coloured dye is measured at 505 nm and is directly
proportional to glucose concentration in the sample. It adheres to
the Beer–Lambert law over a wide range of glucose concentration.
4.1.2.14. 1-[4-{6-(4-Chlorophenyl)-3-oxopyridazin-2-yl}benzenesulf-
onyl]-3-(benzyl)urea (3n). M.p. 215–216 ꢂC; yield ¼ 24%; IR nmax
(KBr, in cmꢁ1): 3346, 3250 and 3066 (NH of ureido group), 1702
and 1528 (C]O of urea), 1678 (cyclic carbonyl), 1600 (C]N), 1331
and 1162 (SO2N); 1H NMR (300 MHz, DMSO-d6,
d): 4.18 (2H, d,
CH2–C6H5), 7.06–7.28 (6H, m, Ar–H and H-4), 7.58 (2H, d, J ¼ 8.5 Hz,
Ar–H), 7.96–8.06 (6H, m, Ar–H), 8.19 (1H, d, J ¼ 9.8 Hz, H-5); 13C
NMR (75 MHz, DMSO-d6, d, ppm): 42.87 (ArCH2), 144.90 (C]N of
pyridazinone), 152.0 (C]O), 158.65 (C]O); FAB-MS (m/z): 495
4.2.5. Calculation
[Mþ], 452, 387, 362, 281(base peak).
Results of blood glucose estimation are presented in the form of
ꢀSEM and percent reduction by test drug. The percent reduction
was calculated by considering the difference between the blood
glucose levels of respective control animals at just prior to glucose
loading and at 90 min after of glucose loading as 100% rise in the
blood sugar. A 100% reduction indicates there is no rise in the level
of blood sugar, while 0% reduction indicates there is no reduction in
the level of blood sugar.
4.1.2.15. 1-[4-{6-(4-Chloro-3-methylphenyl)-3-oxopyridazin-2-yl}
benzenesulfonyl]-3-(cyclohexyl)urea
(3o). M.p.
274–275 ꢂC;
yield ¼ 15.1%; IR nmax (KBr, in cmꢁ1): 3379 (NH of ureido group),
1707 and 1545 (C]O of urea), 1663 (cyclic carbonyl), 1604 (C]N),
1339 and 1160 (SO2N); 1H NMR (300 MHz, DMSO-d6,
d): d: 1.13–
1.65 (10H, m, cyclohexyl protons), 2.39 (3H, s, CH3), 6.38 (1H, br s,
NH–C6H11), 7.24 (1H, d, J ¼ 9.8 Hz, H-4), 7.49 (1H, d, J ¼ 8.4 Hz, Ar–
H), 7.80 (1H, d, J ¼ 7.9 Hz, Ar–H), 7.91–8.04 (5H, m, Ar–H), 8.20 (1H,
Acknowledgements
d, J ¼ 9.7 Hz, H-5); 13C NMR (75 MHz, DMSO-d6,
d, ppm): 19.65
(ArCH3), 24.24 (2 ꢃ CH2), 24.98 (CH2), 32.30 (2 ꢃ CH2), 48.20 (CH–
NH), 144.86 (C]N of pyridazinone), 150.55 (C]O), 158.55 (C]O);
FAB-MS (m/z): 501 [Mþ].
This work was supported by Grant No. 32-228/2006 (SR) from
the University Grants Commission, New Delhi, India. One of the
authors, I.G. Rathish is thankful to UGC for fellowship. Thanks are
also due to SAIF, CDRI, Lucknow, for providing Mass spectra.
4.2. Blood glucose lowering studies
References
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