Synthesis and in vivo hypoglycemic activity of new imidazolidine-2,4-dione derivatives

Article abstract of DOI:10.1007/s11164-014-1814-3

A series of new 3-arylsulfonylimidazolidine-2,4-diones (2a-2p) were synthesized by reacting imidazolidine-2,4-diones (1a-1e) with arylsulfonyl chlorides in the presence of triethyl amine. The imidazolidine-2,4-diones (1a-1e) were in turn synthesized from the corresponding ketones through Bucherer-Bergs reaction. All the synthesized compounds were characterized on the basis of their spectral (IR, ¹H and ¹³C NMR and MS) and microanalytical data. The hypoglycemic activity of the compounds (2a-2p) was evaluated using alloxanized diabetic rat model. Compound 2a showed an excellent activity with a reduction in the blood glucose level of -286 ± 7 mg/dL after 5 h of drug administration as compared to -270 ± 8 mg/dL for glipizide. The hypoglycemic activity of compound 2b (-268 ± 9 mg/dL) was also comparable to the standard drug. However, only moderate activity was observed for compound 2e.

Full text of DOI:10.1007/s11164-014-1814-3

Res Chem Intermed
DOI 10.1007/s11164-014-1814-3
Synthesis and in vivo hypoglycemic activity of new
imidazolidine-2,4-dione derivatives
•
Abid Hussain Muhammad Kalim Kashif
•
•
•
Muhammad Moazzam Naseer Usman A. Rana
Shahid Hameed
Received: 2 August 2014 / Accepted: 15 September 2014
Ó Springer Science+Business Media Dordrecht 2014
Abstract A series of new 3-arylsulfonylimidazolidine-2,4-diones (2a–2p) were
synthesized by reacting imidazolidine-2,4-diones (1a–1e) with arylsulfonyl chlorides in
the presence of triethyl amine. The imidazolidine-2,4-diones (1a–1e) were in turn
synthesized from the corresponding ketones through Bucherer–Bergs reaction. All the
synthesized compounds were characterized on the basis of their spectral (IR, 1H and 13
C
NMR and MS) and microanalytical data. The hypoglycemic activity of the compounds
(2a–2p) was evaluated using alloxanized diabetic rat model. Compound 2a showed an
excellent activity with a reduction in the blood glucose level of -286 7 mg/dL after
5 h of drug administration as compared to -270 8 mg/dL for glipizide. The hypo-
glycemic activity of compound 2b (-268 9 mg/dL) was also comparable to the
standard drug. However, only moderate activity was observed for compound 2e.
Keywords Sulfonylureas ꢀ Imidazolidine-2,4-diones ꢀ In vivo hypoglycemic
activity
Introduction
Type 2 diabetes mellitus is more common than Type 1 diabetes mellitus and is
responsible for more than 90 % of the cases of diabetes worldwide. Individuals over
A. Hussain ꢀ M. K. Kashif ꢀ M. M. Naseer (&) ꢀ S. Hameed (&)
Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
e-mail: moazzam@qau.edu.pk
S. Hameed
e-mail: shameed@qau.edu.pk; shahidhameed@daad-alumni.de
U. A. Rana
Sustainable Energy Technologies Centre, College of Engineering, King Saud University,
Riyadh 11421, Saudi Arabia
123

A. Hussain et al.
45 years of age and those having a body mass index (BMI) of C25 kg/m2 are at an
increased risk of developing type 2 diabetes [1–3]. Furthermore, there are a number
of complications associated with the disease. These include diabetic retinopathy,
diabetic neuropathy, kidney failure, foot ulcers and eventual limb amputation, and
increased risk of heart disease and stroke [4–7]. Therefore, it is necessary and urgent
to discover novel and more effective agents to treat diabetes.
In recent years, small molecules which are capable of inhibiting protein tyrosine
phosphatase-1B (PTP1B) have attracted great attention while searching novel
agents for the treatment of type 2 diabetes and obesity [8–10]. Several studies have
demonstrated that compounds containing thiazolidinedione (TZD)-like scaffolds
show inhibitory effects against PTP1B and other enzymes [11–13]. Very recently,
imidazolidine-2,4-dione derivatives having a TZD-like scaffold were obtained by
virtual screening and proved to be selective Inhibitors by targeting PTP1B over T
cell protein tyrosine phosphatase [14].
Sulfonylureas have been available for the treatment of diabetes and associated
complications since the early 1950s [15–17] along with many herbal formulations
[18–20]. Because of their ability to increase or maintain insulin secretions from the
beta-cells of pancreas and slightly improving insulin resistance in peripheral target
tissues (muscle, fat, etc.), sulfonylureas are also the foundation of combination
therapy. Imidazolidine-2,4-diones, on the other hand, are cyclic ureas and are known
aldose reductase inhibitors [21] in addition to having other useful bioactivities [22–
25]. N-Arylsulfonyl derivatives of imidazolidine-2,4-diones, having both a sulfonyl
moiety and a urea core, may be the molecules of choice to treat diabetes and
associated complications. With this in mind, we have previously reported the
synthesis and hypoglycemic activity of a number of N-arylsulfonylureas [26–30]. In
continuation of our previous work, we report the synthesis of new N-arylsulfonyl
derivatives of imidazolidine-2,4-dione as potent hypoglycemic agents.
Experimental section
General
Melting points of the compounds were determined in open capillaries using
Gallenkemp melting point apparatus and are uncorrected. IR spectra were recorded
on FTS 3000 MX, Bio-Rad Merlin (Excalibur Model) spectrophotometer as KBr
1
discs while H- and 13C-NMR spectra were recorded on a BrukerAvance 300 MHz
NMR spectrophotometer and the signals calibrated to the residual solvent signal.
EIMS were measured on a MAT-112-S machine at 70 eV. The reactions were
monitored by TLC using Pre-coated Silicagel-60 HF254 TLC plates. All the solvents
were distilled before use. Dichloromethane was dried by distilling over phosphorus
pentaoxide.
123

Synthesis and in vivo hypoglycemic activity
General method for the synthesis of 5,5-dimethylimidazolidine-2,4-diones,
1a–1e
The ketone (0.1 mol) and ammonium carbonate (0.6 mol) were placed in a 100-mL
round bottom flask. Potassium cyanide (0.1 mol) was dissolved in ethanol (60 %)
and added to the reaction flask. The reaction mixture was heated on an oil bath at
55–60 °C. After completion of the reaction (TLC), the mixture was cooled to room
temperature and acidified using concentrated HCl. The resulting precipitates were
filtered, dissolved in saturated NaOH solution, and extracted once with diethyl ether.
The ethereal extract was discarded and the aqueous layer was acidified to get the
precipitates of immidazolidine-2,4-dione. The precipitates were filtered and
recrystallized from ethanol/water to give a pale yellow product [28].
5,5-Dimethylimidazolidine-2,4-dione, 1a
Yield: 65 %; mp 180 °C (lit. 182 °C). IR (KBr):mmax = 3,465, 3,278, 2,960, 1,776,
1,665, 1,275 cm-1
.
5-Methyl-5-phenylimidazolidine-2,4-dione, 1b
Yield: 78 %; mp 208–210 °C; Rf = 0.64 (petroleum ether/ethyl acetate 1: 2); IR
(KBr):mmax = 3,285, 3,215, 3,031, 2,961, 1,776, 1,714, 1,593, 1,273, 845 cm-1. 1H-
NMR (300 MHz, DMSO-d6): d = 1.66 (3H, s), 7.32 (1H, tt, J = 7.2, 2.1 Hz), 7.40
(2H, dt, J = 7.2, 2.1 Hz), 7.49 (2H, dd, J = 7.2, 1.5 Hz), 8.64 (1H, bs), 10.74 (1H,
bs) ppm; 13C-NMR (75 MHz, DMSO-d6): d = 25.4, 64.4, 125.8, 128.3, 128.9,
156.8, 177.5 ppm. EI MS: m/z = 190 (M?), 175, 147, 119, 113, 77.
5-(4-Fluorophenyl)-5-methylimidazolidine-2,4-dione, 1c
Yield: 75 %; mp 212–215 °C; Rf = 0.58 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,412, 3,245, 3,058, 2,989, 1,773, 1,719, 1,602, 1,378, 1,274,
1
838 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.80 (3H, s), 7.18 (2H, m), 7.64
(2H, m), 7.71 (1H, bs), 9.72 (1H, bs) ppm. EI MS: m/z = 208 (M?), 193, 165, 137,
122, 95.
5-(4-Bromophenyl)-5-methylimidazolidine-2,4-dione, 1d
Yield: 68 %; mp: 277–279 °C; Rf = 0.62 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,276, 3,211, 3,041, 2,978, 1,774, 1,722, 1,568, 1,271, 1,070,
828 cm-1 1H-NMR (300 MHz, acetone-d6): d = 1.80 (3H, s), 7.56 (2H, dd,
.
J = 9.0, 2.2 Hz), 7.61 (2H, dd, J = 8.7, 2.2 Hz), 7.72 (1H, bs), 9.73 (1H, bs) ppm.
EI MS: m/z = 270 (M ? 2), 268 (M?), 255, 253, 227, 225, 199, 197, 184, 182, 157,
155, 114, 112.
123

A. Hussain et al.
5-(4-Chlorophenyl)-5-methylimidazolidine-2,4-dione, 1e
Yield: 56 %; mp 266–268 °C; Rf = 0.56 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,276, 3,225, 3,038, 2,960, 1,774, 1,720, 1,576, 1,270, 1,030,
852 cm-1 1H-NMR (300 MHz, acetone-d6): d = 1.79 (3H, s), 7.54 (2H, dd,
.
J = 8.7, 2.1 Hz), 7.60 (2H, dd, J = 8.7, 2.1 Hz), 7.69 (1H, bs), 9.69 (1H, bs) ppm.
EI MS: m/z = 226 (M ? 2), 224 (M), 211, 209, 183, 181, 155, 153, 140, 138, 115,
113, 111.
General method for the synthesis of 3-arylsulfonylimidazolidine-2,4-diones,
2a–2p
To a well-stirred mixture of imidazolidine-2,4-dione (4.8 mmol), triethylamine
(4.8 mmol) and catalytic amounts of DMAP, was added dropwise a solution of aryl
sulfonyl chloride (5.8 mmol) in dichloromethane and the reaction mixture was
stirred at room temperature for 3 h. The reaction mixture was diluted with 1 N HCl
until pH 2 and extracted with dichloromethane (3 9 25 mL). The crude product
after evaporation of the solvent was recrystallized from ethyl acetate to afford the
pure product.
3-(4-Chlorophenylsulfonyl)-5,5-dimethylimidazolidine-2,4-dione, 2a
Yield: 56 %; mp 134 °C (lit. 134 °C) [28]. IR (KBr):mmax = 3,468, 3,279, 2,962,
1,693, 1,655, 1,358, 1,262, 1,145, 976, 848 cm-1
.
5-Methyl-3-(4-methylphenylsulfonyl)-5-phenylimidazolidine-2,4-dione, 2b
Yield: 54 %; mp 251 °C; Rf = 0.73 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,228, 3,019, 2,963, 1,762, 1,714, 1,611, 1,578, 1,358, 1,278, 1,153,
1
979, 869 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.86 (3H, s), 2.49 (3H, s),
7.14–7.25 (5H, m), 7.39 (2H, d, J = 8.1 Hz), 7.85 (2H, d, J = 8.2 Hz), 8.90 (1H, s)
ppm; 13C-NMR (75 MHz, acetone-d6): d = 21.0, 71.0, 114.0, 129.6, 130.3, 132.6,
136.5, 137.0, 139.5, 155.5, 176.6 ppm. EI MS: m/z = 344 (M?), 280, 265, 189, 155,
146, 91, 77, 65, 51. Anal. Calcd. for C17H16N2O4S: C, 59.29; H, 4.68; N, 8.13; S,
9.31. Found: C, 59.44; H, 4.51; N, 8.21; S, 9.56.
3-(4-Methoxyphenylsulfonyl)-5-methyl-5-phenylimidazolidine-2,4-dione, 2c
Yield: 62 %; mp 132 °C; Rf = 0.75 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,235, 3,023, 2,960, 1,771, 1,721, 1,616, 1,576, 1,366, 1,286, 1,160,
1
986, 856 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.75 (3H, s), 3.8 (3H, s),
7.10–7.28 (7H, m), 7.78 (2H, d, J = 8.7 Hz), 8.98 (1H, bs) ppm; 13C-NMR
(75 MHz, acetone-d6): d = 21.7, 55.6, 71.1, 114.2, 126.5, 128.8, 130.2, 131.8,
135.9, 136.8, 152.0, 159.1, 171.7 ppm. EI MS: m/z = 360 (M?), 296, 281, 189, 171,
146, 107, 77. Anal. Calcd. for C17H16N2O5S: C, 56.66; H, 4.47; N, 7.77; S, 8.90.
Found: C, 56.43; H, 4.54; N, 7.62, S, 9.09.
123

Synthesis and in vivo hypoglycemic activity
3-(4-Bromophenylsulfonyl)-5-methyl-5-phenylimidazolidine-2,4-dione, 2d
Yield: 60 %; mp 216 °C; Rf = 0.73 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,192, 3,010, 2,974, 1,768, 1,722, 1,608, 1,563, 1,347, 1,269, 1,169,
1
1,070, 850 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.80 (3H, s), 7.12–7.27
(5H, m), 7.64 (2H, d, J = 8.7 Hz), 7.89 (2H, d, J = 8.7 Hz), 8.83 (1H, bs) ppm;
13C-NMR (75 MHz, acetone-d6): d = 21.5, 71.1, 114.2, 126.5, 130.2, 131.8, 133.0,
136.5, 136.8, 155.6, 159.1, 175.7 ppm. EI MS: m/z = 410 (M ? 2), 408 (M?), 346,
344, 331, 329, 221, 219, 189, 157, 155, 146, 77. Anal. Calcd. for C16H13BrN2O4S:
C, 46.96; H, 3.20; N, 6.84; S, 7.83. Found: C, 47.09; H, 3.11; N, 6.61; S, 8.13.
3-(4-Chlorophenylsulfonyl)-5-methyl-5-phenylimidazolidine-2,4-dione, 2e
Yield: 56 %; mp 168 °C; Rf = 0.71 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,236, 3,021, 2,979, 1,763, 1,710, 1,611, 1,567, 1,366, 1,275, 1,179,
1
1,028, 844 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.78 (3H, s), 7.10–7.25
(5H, m), 7.55 (2H, d, J = 8.7 Hz), 7.82 (2H, d, J = 8.7 Hz), 8.76 (1H, bs) ppm;
13C-NMR (75 MHz, acetone-d6): d = 21.7, 61.0, 126.8, 130.0, 132.7, 133.0, 138.0,
155.9, 176.3 ppm. EI MS: m/z = 366 (M? ? 2), 364 (M?), 302, 300, 189, 187,
185, 177, 175, 146, 113, 111, 77. Anal. Calcd. for C16H13ClN2O4S: C, 52.68; H,
3.59; N, 7.68; S, 8.79. Found: C, 52.82; H, 3.51; N, 7.42; S, 8.97.
5-Methyl-3-(naphthalen-2-ylsulfonyl)-5-phenylimidazolidine-2,4-dione, 2f
Yield: 53 %; mp 198 °C; Rf = 0.72 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,228, 3,023, 2,990, 1,770, 1,721, 1,600, 1,342, 1,265, 1,180, 976,
1
859 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.80 (3H, s), 7.17–7.28 (5H, m),
7.92–8.20 (7H, m), 8.80 (1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6): d = 20.4,
69.9, 112.0, 126.0, 126.2, 126.3, 127.1, 128.1, 128.4, 128.8, 130.0, 130.1, 135.3,
136.2, 138.4, 140.1, 155.2, 175.0 ppm. EI MS: m/z = 380 (M?), 316, 301, 191, 189,
146, 127, 77. Anal. Calcd. for C20H16N2O4S: C, 63.14; H, 4.24; N, 7.36; S, 8.43.
Found: C, 62.98; H, 4.35; N, 7.21; S, 8.57.
5-(4-Fluorophenyl)-5-methyl-3-(4-methylphenylsulfonyl)imidazolidine-2,4-dione,
2g
Yield: 56 %; mp 152 °C; Rf = 0.78 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,210, 3,012, 2,967, 1,763, 1,715, 1,605, 1,580, 1,386, 1,361, 1,269,
1
1,175, 977, 849 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.86 (3H, s), 2.95
(3H, s), 7.15–7.25 (2H, m), 7.40 (2H, d, J = 8.4 Hz), 7.48–7.58 (2H, m), 7.71 (2H,
d, J = 8.4 Hz), 9.47 (1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6): d = 20.6,
21.2, 71.2, 115.5 (J = 21.0 Hz), 115.7, 128.6 (J = 8.2 Hz), 130.2, 136.4
(J = 3.0 Hz), 136.5, 145.5, 155.9, 161.7 (J = 241.8 Hz), 164.3, 175.6 ppm. EI
MS: m/z = 362 (M?), 298, 283, 207, 164, 155, 95, 91, 65. Anal. Calcd. for
C17H15FN2O4S: C, 56.35; H, 4.17; N, 7.73; S, 8.85. Found: C, 56.24; H, 4.22; N,
7.81; S, 9.09.
123

A. Hussain et al.
5-(4-Fluorophenyl)-3-(4-methoxyphenylsulfonyl)-5-methylimidazolidine-2,4-dione,
2h
Yield: 62 %; mp 236 °C; Rf = 0.75 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,231, 3,009, 2,977, 1,765, 1,720, 1,617, 1,559, 1,390, 1,360, 1,274,
1
1,182, 986, 848 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.91 (3H, s), 3.85
(3H, s), 6.85–7.00 (4H, m), 7.27–7.34 (2H, m), 7.71 (2H, dd, J = 9.0, 3.0 Hz), 9.51
(1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6): d = 21.9, 55.3, 71.1, 114.0, 114.6
(J = 21.2 Hz), 128.8 (J = 3.0 Hz), 130.2, 132.9, 136.4, 136.5 (J = 3.0 Hz), 157.0,
162.0 (J = 242.0 Hz), 163.0, 187.8 ppm. EI MS: m/z = 378 (M?), 314, 299, 207,
164, 159, 95. Anal. Calcd. for C17H15FN2O5S: C, 53.96; H, 4.00; N, 7.40; S, 8.47.
Found: C, 54.03; H, 3.91; N, 7.19; S, 8.78.
3-(4-Bromophenylsulfonyl)-5-(4-fluorophenyl)-5-methylimidazolidine-2,4-dione, 2i
Yield: 53 %; mp 218 °C; Rf = 0.74 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,229, 3,013, 2,978, 1,769, 1,717, 1,602, 1,572, 1,398, 1,343, 1,263,
1,163, 963, 858 cm-1 1H-NMR (300 MHz, acetone-d6): d = 1.88 (3H, s),
.
7.18–7.28 (2H, m), 7.52–7.60 (2H, m), 7.73 (2H, dd, J = 9.0, 1.8 Hz), 7.82 (2H,
dd, J = 8.7, 2.1 Hz), 9.47 (1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6):
d = 21.0, 71.2, 114.8 (J = 21.0 Hz), 128.6, 128.9 (J = 8.4 Hz), 130.3, 132.2,
136.6 (J = 2.8 Hz), 138.1, 157.9, 161.8 (J = 243.2 Hz), 176.5 ppm. EI MS:
m/z = 428 (M? ? 2), 426 (M?), 364, 362, 349, 347, 221, 219, 207, 164, 157, 155,
95. Anal. Calcd. for C16H12BrFN2O4S: C, 44.98; H, 2.83; N, 6.56; S, 7.51. Found:
C, 44.94; H, 2.77; N, 6.64; S, 7.80.
3-(4-Chlorophenylsulfonyl)-5-(4-fluorophenyl)-5-methylimidazolidine-2,4-dione, 2j
Yield: 49 %; mp 223 °C; Rf = 0.58 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,236, 3,014, 2,970, 1,770, 1,721, 1,600, 1,581, 1,398, 1,366, 1,284,
1,143, 986, 853 cm-1 1H-NMR (300 MHz, acetone-d6): d = 1.83 (3H, s),
.
7.05–7.15 (2H, m), 7.20–7.30 (2H, m), 7.57 (2H, dd, J = 9.0, 1.8 Hz), 7.71 (2H,
dd, J = 9.0, 2.1 Hz), 9.55 (1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6):
d = 20.8, 69.9, 115.7 (J = 21.9 Hz), 128.6 (J = 8.6 Hz), 129.6, 130.1, 132.9,
136.4 (J = 2.8 Hz), 138.4, 156.2, 162.2 (J = 242.2 Hz), 177.0 ppm. EI MS:
m/z = 384 (M? ? 2), 382 (M?), 320, 318, 305, 303, 207, 177, 175, 164, 113, 111,
95. Anal. Calcd. for C16H12ClFN2O4S: C, 50.20; H, 3.16; N, 7.32; S, 8.38. Found:
C, 50.34; H, 3.23; N, 7.12; S, 8.51.
5-(4-Bromophenyl)-5-methyl-3-(4-methylphenylsulfonyl)imidazolidine-2,4-dione,
2k
Yield: 43 %; mp 234 °C; Rf = 0.77 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,213, 3,023, 2,962, 1,768, 1,727, 1,612, 1,565, 1,346, 1,270, 1,162,
1
1,070, 856 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.86 (3H, s), 2.46 (3H, s),
7.38–7.48 (4H, m), 7.63 (2H, dd, J = 9.0, 2.1 Hz), 7.73 (2H, dd, J = 8.4, 1.8 Hz),
123

Synthesis and in vivo hypoglycemic activity
9.40 (1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6): d = 21.0, 21.3, 71.2, 125.7,
126.4, 129.9, 130.2, 132.8, 136.0, 137.5, 141.3, 156.9, 175.6 ppm. EI MS:
m/z = 424 (M? ? 2), 422 (M?), 360, 358, 345, 343, 269, 267, 226, 224, 157, 155,
91, 65. Anal. Calcd. for C17H15BrN2O4S: C, 48.24; H, 3.57; N, 6.62; S, 7.58. Found:
C, 48.31; H, 3.51; N, 6.47; S, 7.90.
5-(4-Bromophenyl)-3-(4-methoxyphenylsulfonyl)-5-methylimidazolidine-2,4-dione,
2l
Yield: 57 %; mp 245 °C; Rf = 0.69 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,181, 3,021, 2,970, 1,775, 1,722, 1,609, 1,562, 1,360, 1,273, 1,158,
1
1,070, 854 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.93 (3H, s), 3.86 (3H, s),
7.12 (2H, dd, J = 9.0, 1.8 Hz), 7.35 (2H, dd, J = 8.7, 2.1 Hz), 7.63 (2H, dd,
J = 9.0, 2.1 Hz), 7.71 (2H, dd, J = 9.0, 3.0 Hz), 9.55 (1H, bs) ppm; 13C-NMR
(75 MHz, acetone-d6): d = 21.6, 55.4, 69.7, 114.2, 126.6, 130.1, 130.5, 132.9,
136.4, 137.0, 155.5, 164.5, 175.9 ppm. EI MS: m/z = 440 (M? ? 2), 438 (M?),
376, 374, 361, 359, 269, 267, 226, 224, 171, 157, 155, 107. Anal. Calcd. for
C17H15BrN2O5S: C, 46.48; H, 3.44; N, 6.38; S, 7.30. Found: C, 46.57; H, 3.33; N,
6.21; S, 7.52.
5-(4-Bromophenyl)-3-(4-bromophenylsulfonyl)-5-methylimidazolidine-2,4-dione,
2m
Yield: 55 %; mp 238 °C; Rf = 0.75 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,198, 3,012, 2,965, 1,768, 1,714, 1,623, 1,561, 1,359, 1,271, 1,162,
1,068, 848 cm-1. 1H-NMR (300 MHz, acetone-d6): d = 1.90 (3H, s), 7.20 (2H, dd,
J = 8.7, 1.8 Hz), 7.65 (2H, dd, J = 9.0, 2.1 Hz), 7.85 (2H, dd, J = 8.7, 2.1 Hz),
9.57 (1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6): d = 21.0, 71.2, 127.0, 128.6,
129.1, 129.7, 130.3, 132.2, 136.4, 138.1, 156.4, 176.2 ppm. EI MS: m/z = 490
(M? ? 4), 488 (M? ? 2), 486 (M?), 426, 424, 422, 411, 409, 407, 269, 267, 226,
224, 221, 219, 157, 155. Anal. Calcd. for C16H12Br2N2O4S: C, 39.37; H, 2.48; N,
5.74; S, 6.57. Found: C, 39.24; H, 2.55; N, 5.61; S, 6.99.
5-(4-Chlorophenyl)-5-methyl-3-(4-methylphenylsulfonyl)imidazolidine-2,4-dione,
2n
Yield: 54 %; mp 197 °C; Rf = 0.66 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax 3,210, 3,024, 2,970, 1,768, 1,715, 1,590, 1,363,1,270, 1,168, 1,030,
1
854 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.8 (3H, s), 2.48 (3H, s), 7.22
(2H, dd, J = 9.0, 1.8 Hz), 7.31 (2H, dd, J = 8.7, 2.1 Hz), 7.37 (2H, dd, J = 8.7,
1.8 Hz), 7.77 (2H, dd, J = 8.4, 1.8 Hz), 9.43 (1H, bs) ppm; 13C-NMR (75 MHz,
acetone-d6): d = 21.8, 24.1, 71.4, 115.8, 127.7, 130.3, 131.8, 132.9, 133.0, 133.8,
137.0, 138.0, 155.0, 176.3 ppm. EI MS: m/z = 380 (M ? 2), 378 (M?), 316, 314,
301, 299, 225, 223, 182, 180, 157, 155, 113, 111, 91, 65. Anal. Calcd. for
C17H15ClN2O4S: C, 53.90; H, 3.99; N, 7.39; S, 8.46. Found: C, 54.04; H, 3.90; N,
7.21; S, 8.54.
123

A. Hussain et al.
5-(4-Chlorophenyl)-3-(4-methoxyphenylsulfonyl)-5-methylimidazolidine-2,4-dione,
2o
Yield: 50 %; mp 178 °C; Rf = 0.69 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax 3,223, 3,034, 2,970, 1,773, 1,719, 1,596, 1,366, 1,281, 1,164, 1,030,
1
847 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.86 (3H, s), 3.88 (3H, s), 7.12
(2H, dd, J = 9.0, 2.1 Hz), 7.20 (2H, dd, J = 8.7, 2.1 Hz), 7.33 (2H, dd, J = 9.0,
2.1 Hz), 7.78 (2H, dd, J = 9.0, 3.0 Hz), 9.68 (1H, bs) ppm; 13C-NMR (75 MHz,
acetone-d6): d = 21.9, 56.0, 70.9, 114.6, 128.9, 130.1, 133.0, 134.0, 136.2, 138.4,
156.2, 156.4, 176.0 ppm. EI MS: m/z = 396 (M ? 2), 394 (M?), 332, 330, 317,
315, 225, 223, 182, 180, 177, 175, 113, 111. Anal. Calcd. for C17H15ClN2O5S: C,
51.71; H, 3.83; N, 7.10; S, 8.12. Found: C, 51.63; H, 3.89; N, 6.91; S, 8.41.
5-(4-Chlorophenyl)-3-(4-bromophenylsulfonyl)-5-methylimidazolidine-2,4-dione,
2p
Yield: 48 %; mp 198 °C; Rf = 0.74 (petroleum ether/ethyl acetate 1: 2). IR
(KBr):mmax = 3,209, 2,998, 1,769, 1,721, 1,606, 1,574, 1,350, 1,285, 1,163, 1,030,
1
852 cm-1. H-NMR (300 MHz, acetone-d6): d = 1.90 (3H, s), 7.22–7.30 (2H, m),
7.35 (2H, dd, J = 8.7, 2.1 Hz), 7.73 (2H, dd, J = 9.0, 1.8 Hz), 7.85 (2H, dd,
J = 8.7, 2.1 Hz), 9.57 (1H, bs) ppm; 13C-NMR (75 MHz, acetone-d6): d = 21.0,
69.8, 128.0, 129.0, 130.0, 132.4, 132.8, 133.6, 136.8, 138.2, 154.9, 175.1 ppm. EI
MS: m/z = 446 (M? ? 4), 444 (M? ? 2), 442 (M?), 382, 380, 378, 367, 365, 363,
225, 223, 221, 219, 182, 180, 157, 155, 113, 111. Anal. Calcd. for C16H12BrClN2-
O4S: C, 43.31; H, 2.73; N, 6.31; S, 7.23. Found: C, 43.34; H, 2.64; N, 6.22; S, 7.40.
Pharmacological methods
The effectiveness of the synthesized 3-arylsulfonylimidazolidine-2,4-diones as
hypoglycemic agents was performed on albino rats. The animals were maintained
in cages with a 12-h light/dark cycle, with free access to food and water. Male rats of
the Sprague–Dawley strain (180–220 g) were made diabetic by intra-abdominal
injection of 225 mg/Kg alloxan monohydrate freshly dissolved in distilled water [31].
Three days later, the blood from each rat was tested for the glucose level using an
Accu-check blood glucose analyzer. Rats showing blood glucose levels above
300 mg/dL were taken for further experiments as diabetic animals. These diabetic rats
were segregated into groups of six rats each. After obtaining control blood samples
from the tail vein of all the rats, the test compound dissolved in DMSO and Glipizide
(as a standard drug) were administered orally at doses of 50 and 100 mg/Kg body
weight in separate experiments to compare their glucose-lowering potential. Blood
samples were again obtained for glucose assay after 3 and 5 h of compound
administration. An appropriate vehicle control (DMSO) was also run [32]. One group
of diabetic rats was left intact (untreated diabetic) for comparison. The results are
reported as mean standard deviation, n = 6 in each group.
123

Synthesis and in vivo hypoglycemic activity
Results and discussion
Chemistry
Imidazolidine-2,4-diones (1a–1e) were synthesized by treatment of the correspond-
ing ketone with potassium cyanide and ammonium carbonate [28] (Scheme 1).
The synthesis of imidazolidine-2,4-diones (1a–1e) was indicated in the IR
spectra by the presence of two strong peaks between 3,200 and 3,400 cm-1 that
were assigned to the N–H of the imide and amide groups. The absorption bands for
the two carbonyl groups appeared between 1,780 and 1,700 cm-1. The synthesis of
1
compounds 1b–1e was further confirmed in H-NMR spectra. The imidic proton
being more acidic appeared downfield (9.69–10.74 ppm) as compared to the amidic
proton (7.69–8.64 ppm). In the aromatic part of the spectrum two multiplets,
centered at d = 7.64 and 7.18 ppm, were observed for compound 1c due to the
coupling of protons with fluorine atom and assigned to H-30/50, and H-20/60,
respectively. In the case of compounds 1d and 1e, two doublets of doublets were
observed in the aromatic region. The protons of the methyl groups at position 5 of
the ring resonated around 1.80 ppm which is consistent with their environment,
being b to two electron-withdrawing groups. In the mass spectra of all these
compounds (1a–1e), the molecular ion peaks observed were of low intensity
(15–30 %). The base peak was observed at m/z = 122 in the case of compound 1c
and two intense peaks of almost equal intensity were observed for compound 1d at
m/z = 182 (100 %) and m/z = 184 (98 %). For compound 1e, the base peak was
observed at m/z = 138 along with the isotopic peak at m/z = 140.
The synthesis of 3-arylsulfonylimidazolidine-2,4-diones (2a–2p) was carried out
by the reaction of imidazolidine-2,4-diones with arylsulfonyl chlorides in the
presence of triethyl amine and catalytic amounts of DMAP (Scheme 2).
The coupling of imidazolidine-2,4-diones with arylsulfonyl chlorides was
indicated in the IR spectrum by disappearance of one of the N–H stretchings.
Only one peak was observed in the range of 3,236–3,181 cm-1 which indicated that
sulfonylation had taken place at N-3 of imidazolidine-2,4-dione. In addition, the
antisymmetric and symmetric O=S=O absorptions observed in the range of
1,379–1,335 cm-1 and 1,178–1,145 cm-1, respectively, also indicated the coupling.
The synthesis of 3-arylsulfonylimidazolidine-2,4-diones (2a–2p) was confirmed by
1H-NMR spectroscopy. In the 1H-NMR spectra of compound (2a–2p), the
appearance of signals for four additional protons in the aromatic region confirmed
the synthesis of these compounds. The disappearance of N–H signal in the range of
d = 9.69–10.74 ppm confirmed that the substitution had taken place at position 3 of
imidazolidine-2,4-dione ring. The 13C-NMR spectra demonstrated that the carbonyl
carbons, C-4 and C-2, resonate in the range of d = 187.8–174.3 and
d = 157.9–155.2 ppm, respectively. The upfield absorption of C-2 may be
attributed to its direct linkage to two mesomerically electron donating nitrogen
atoms, while C-4 is linked to only one. In the case of compounds (2g–2j), the C–F
couplings were also observed. The mass spectrometry further confirmed the
synthesis. A low intensity molecular ion peak was observed in all the cases. A
common observation was the loss of a neutral fragment of 64 mass units (M-SO2)
123

A. Hussain et al.
O
i) KCN
R
HN
ii) (NH4)2CO3
R
O
NH
60% ethanol, reflux
H3C
H3C
iii) HCl
O
1a: R = CH3
1b: R = C6H5
1c: R = 4-FC6H4
1d: R = 4-BrC6H4
1e: R = 4-ClC6H4
Scheme 1 Synthesis of imidazolidine-2,4-diones (1a–1e)
O
O
(i) Et3N
HN
HN
R
O
R
Ar
N
(ii) DMAP
NH
Ar
S
Cl
S
H3C
H3C
O
O
O
O
O
2a: R = CH3; Ar = 4-ClC6H5
2b: R = C6H5; Ar = 4-CH3C6H5
2c: R = C6H5; Ar = 4-CH3OC6H5
2d: R = C6H5; Ar = 4-BrC6H5
2e: R = C6H5; Ar = 4-ClC6H5
2f: R = C6H5; Ar = 2-naphthyl
2g: R = 4-FC6H5; Ar = 4-CH3C6H5
2h: R = 4-FC6H5; Ar = 4-CH3OC6H5
2i: R = 4-FC6H5; Ar = 4-BrC6H5
2j: R = 4-FC6H5; Ar = 4-ClC6H5
2k: R = 4-BrC6H5; Ar = 4-CH3C6H5
2l: R = 4-BrC6H5; Ar = 4-CH3OC6H5
2m: R = 4-BrC6H5; Ar = 4-BrC6H5
2n: R = 4-ClC6H5; Ar = 4-CH3C6H5
2o: R = 4-ClC6H5; Ar = 4-CH3OC6H5
2p: R = 4-ClC6H5; Ar = 4-BrC6H5
Scheme 2 Synthesis of 3-arylsulfonylimidazolidine-2,4-diones (2a–2p)
and a fragment formed by the loss of -SO2Ar. The isotopic M ? 2 peaks were also
observed in case of bromo- and chloro-substituted compounds.
Hypoglycemic activity (in vivo)
The hypoglycemic potential of compounds (2a–2p) was examined on alloxanized
diabetic male albino rats of the Sprague–Dawley strain (180–220 g; 6–8 weeks old)
123

Synthesis and in vivo hypoglycemic activity
123

A. Hussain et al.
Fig. 1 Blood glucose level (mg/dL) at 100 mg/kg concentration of active compounds 2a–2c, 2e, and 2f
compared to Glipizide, a standard drug
at dose levels of 50 and 100 mg/kg of the mice body weight. The reduction in blood
glucose levels were measured 3 and 5 h after dose administration. Glipizide, a
second generation sulfonylurea, was used as the reference standard drug in this
study. Only five compounds 2a–2c, 2e, and 2f were found active showing a varying
degree of hypoglycemic potential, when compared to standard drug Glipizide
(Table 1, Fig. 1), while all other compounds showed no activity at non-toxic
concentrations. Compounds 2a and 2b exhibited excellent hypoglycemic activity.
Compound 2a was found to be more potent than the standard drug with a reduction
in the blood glucose level of -286 7 mg/dL after 5 hours of drug administration,
as compared to -270 8 mg/dL produced by glipizide. This amounts to the
percent decrease in blood glucose by 46.11 % in relation to the alloxan-induced
diabetic rats when compared to the 44.82 % produced by the standard. The observed
hypoglycemic activity of compound 2b (-268 9 mg/dL; 42.56 %) was also
comparable to glipizide (-270 8 mg/dL; 44.82 %). Interestingly, the replace-
ment of the methyl group of 2a (R=CH3) with the phenyl group in 2e (R=C6H5)
resulted in a decrease in the hypoglycemic activity. Therefore, a moderate activity
(-196 10 mg/dL; 30.15) was observed for compound 2e. However, compound 2f
revealed a non-significant activity. It appears that in the case of compound 2f, the
bulk of the aromatic part has resulted in a diminished hypoglycemic activity.
Surprisingly, compounds 2d and 2g–2p having halide substituents showed no
activity at non-toxic concentrations. In general, a higher reduction in blood glucose
level was observed for all the active compounds at a dose level of 100 mg/kg except
for 2c where an opposite trend was observed. This unusual behavior of compound
2c may be attributed to its low liposolubility and hence its poor permeation through
the lipoid layer of the membrane, making it less bioavailable at higher
concentrations. In the present study, increasing trends in hypoglycemic activity
were observed as the duration of action of the drug was increased from 3 to 5 h.
This indicates that significant amounts of active compounds remain available in
plasma for longer periods of time which may be beneficial for once a day dosing.
123

Synthesis and in vivo hypoglycemic activity
Conclusion
In conclusion, a series of new 3-arylsulfonylimidazolidine-2,4-diones (2a–2p)
having a TZD-like scaffold was synthesized from imidazolidine-2,4-diones (1a–1e),
obtained from ketones through Bucherer–Bergs reaction. All the synthesized
compounds were fully characterized on the basis of their spectral and microana-
lytical data. The compounds of the present series were also evaluated for their
in vivo hypoglycemic activity, where compound 2a and 2b were found to be the
most active compounds with excellent activity. Compound 2a showed even more
reduction in the blood glucose level after 3 and 5 h of drug administration than the
standard drug, glipizide. Similarly, compound 2b exhibited comparable hypogly-
cemic activity to the standard drug. However, a moderate and non-significant
activity was observed for compounds 2e and 2f, respectively, at 100 mg/kg
concentration. All other compounds were found inactive at non-toxic concentra-
tions. It is anticipated that the new compounds with a TZD-like scaffold may
become potential drug candidates or may play a positive role in finding novel
selective inhibitors against type 2 diabetes.
Acknowledgments We are very grateful to Dr. Rizwana A. Qureshi of the faculty of biological sciences
for help in bioevaluation. The financial support by Quaid-i-Azam University through URF is greatly
acknowledged.
References
1. A.D. Assoc, Diagnosis and classification of diabetes mellitus. Diabetes Care 36, S67 (2013)
2. K. Backholer, A. Peeters, W.H. Herman, J.E. Shaw, D. Liew, Z. Ademi, D.J. Magliano, Diabetes
prevention and treatment strategies: are we doing enough? Diabetes Care 36, 2714 (2013)
3. R.S. Bhopal, A four-stage model explaining the higher risk of Type 2 diabetes mellitus in South
Asians compared with European populations. Diabet. Med. 30, 35 (2013)
4. S. Yamagishi, K. Nakamura, T. Imaizumi, Advanced glycation end products (AGEs) and diabetic
vascular complications. Curr. Diabetes Rev. 1, 93 (2005)
5. S. Yamagishi, T. Imaizumi, Diabetic vascular complications: pathophysiology, biochemical basis and
potential therapeutic strategy. Curr. Pharm. Des. 11, 2279 (2005)
6. A. Abbas, S. Kalsoom, T.B. Hadda, M.M. Naseer, Evaluation of 4-alkoxychalcones as a new class of
antiglycating agents: a combined experimental and docking study. Res. Chem. Intermed. (2014).
doi:10.1007/s11164-014-1752-0
7. A.G. Memon, M.A. Rahman, A. Alghasham, S. Hamid, Q. Hamid, Correlation between adipocy-
tokines and AGE products in diabetic and non-diabetic patients with myocardial infarction. Res.
Chem. Intermed. (2013). doi:10.1007/s11164-013-1298-6
8. Z.Y. Zhang, Protein tyrosine phosphatases: structure and function, substrate specificity, and inhibitor
development. Annu. Rev. Pharmacol. Toxicol. 42, 209 (2002)
9. R. Hooft van Huijsduijnen, W.H. Sauer, A. Bombrun, D. Swinnen, Prospects for inhibitors of protein
tyrosine phosphatase 1B as antidiabetic drugs. J. Med. Chem. 47, 4142 (2004)
10. K.A. Kenner, E. Anyanwu, J.M. Olefsky, J. Kusari, Protein-tyrosine phosphatase 1B is a negative
regulator of insulin- and insulin-like growth factor-I-stimulated signaling. J. Biol. Chem. 271, 19810
(1996)
11. M.S. Malamas, J. Sredy, I. Gunawan, B. Mihan, D.R. Sawicki, L. Seestaller, D. Sullivan, B.R. Flam,
New azolidinediones as inhibitors of protein tyrosine phosphatase 1B with antihyperglycemic
properties. J. Med. Chem. 43, 995 (2000)
12. R. Maccari, R. Ottana, C. Curinga, M.G. Vigorita, D. Rakowitz, T. Steindl, T. Langer, Structure-
activity relationships and molecular modelling of 5-arylidene-2,4-thiazolidinediones active as aldose
reductase inhibitors. Bioorg. Med. Chem. 13, 2809 (2005)
123

A. Hussain et al.
13. R. Maccari, P. Paoli, R. Ottana, M. Jacomelli, R. Ciurleo, G. Manao, T. Steindl, T. Langer, M.G.
Vigorita, G. Camici, 5-Arylidene-2,4-thiazolidinediones as inhibitors of protein tyrosine phospha-
tases. Bioorg. Med. Chem. 15, 5137 (2007)
14. Y. Ma, S.X. Sun, X.C. Cheng, S.Q. Wang, W.L. Dong, R.L. Wang, W.R. Xu, Design and synthesis of
imidazolidine-2,4-dione derivatives as selective inhibitors by targeting protein tyrosine phosphatase-
1B over T-cell protein tyrosine phosphatase. Chem. Biol. Drug Des. 82, 595 (2013)
15. N. Hosseinzadeh, S. Seraj, M.E. Bakhshi-Dezffoli, M. Hasani, M. Khoshneviszadeh, S. Fallah-
Bonekohal, M. Abdollahi, A. Foroumadi, A. Shafiee, Synthesis and antidiabetic evaluation of ben-
zenesulfonamide derivatives. Iran. J. Pharm. Res. 12, 325 (2013)
16. J.A. Wambach, B.A. Marshall, J.C. Koster, N.H. White, C.G. Nichols, Successful sulfonylurea
treatment of an insulin-naive neonate with diabetes mellitus due to a KCNJ11 mutation. Pediatr.
Diabetes 11, 286 (2010)
17. C.J. Currie, C.D. Poole, E.A. Gale, The influence of glucose-lowering therapies on cancer risk in type
2 diabetes. Diabetologia 52, 1766 (2009)
18. S. Rajeswarareddy, T. Lavany, G. Narasimhulu, K. Sathyavelureddy, Effect of pimpinellatir-
upatiensison oxidative enzymes in STZ-induced diabetic rat kidney. Iran. J. Pharm. Res. 11, 277
(2012)
19. S. Shaukat, A. Waqar, M.A. Waqar, Investigating the influence of folk anti-diabetic plants on glucose
diffusion. J. Chem. Soc. Pak. 31, 480 (2009)
20. N.M. Qadri, Zakir-Ur-Rehman, K. Shireen, Evaluation of antidiabetic activity of diabrid, a herbal
formulation, in type-II diabetic patients. J. Chem. Soc. Pak. 28, 281 (2006)
21. F. Da Settimo, G. Primofiore, C. La Motta, S. Salerno, E. Novellino, G. Greco, A. Lavecchia, S.
Laneri, E. Boldrini, Spirohydantoin derivatives of thiopyrano[2,3-b]pyridin-4(4H)-one as potent
in vitro and in vivo aldose reductase inhibitors. Bioorg. Med. Chem. 13, 491 (2005)
22. K. Li, D.Q. Shi, Synthesis and herbicidal activity of 3-Aryl-1-[2-(aryloxy)propanoyl]imidazolidine-
2,4-diones. J. Heterocycl. Chem. 46, 544 (2009)
23. W.J. Flosi, D.A. DeGoey, D.J. Grampovnik, H.J. Chen, L.L. Klein, T. Dekhtyar, S. Masse, K.C.
Marsh, H.M. Mo, D. Kempf, Discovery of imidazolidine-2,4-dione-linked HIV protease inhibitors
with activity against lopinavir-resistant mutant HIV. Bioorg. Med. Chem. 14, 6695 (2006)
24. G.G. Muccioli, N. Fazio, G.K.E. Scriba, W. Poppitz, F. Cannata, J.H. Poupaert, J. Wouters, D.M.
Lambert, Substituted 2-thioxoimidazolidin-4-ones and imidazolidine-2,4-diones as fatty acid amide
hydrolase inhibitors templates. J. Med. Chem. 49, 417 (2006)
25. E. Pekala, K. Stadnicka, A. Broda, M. Zygmunt, B. Filipek, K. Kiec-Kononowicz, Synthesis,
structure-activity relationship of some new anti-arrhythmic 5-arylidene imidazolidine-2,4-dione
derivatives. Eur. J. Med. Chem. 40, 259 (2005)
26. Z. Iqbal, S. Ali, J. Iqbal, Q. Abbas, I.Z. Qureshi, S. Hameed, Dual action spirobicycloimidazolidine-
2,4-diones: antidiabetic agents and inhibitors of aldose reductase-an enzyme involved in diabetic
complications. Bioorg. Med. Chem. Lett. 23, 488 (2013)
27. Z. Iqbal, T. Akhtar, A.D. Hendsbee, J.D. Masuda, S. Hameed, Synthesis, characterization, and
hypoglycemic activity of 3-(arylsulfonyl)spiroimidazolidine-2,4-diones. Monatsh. Chem. 143, 497
(2012)
28. M.K. Kashif, I. Ahmad, S. Hameed, Synthesis and hypoglycemic activity of 5,5-dimethylar-
ylsulfonylimidazolidine-2,4-diones. Arkivoc xvi, 311 (2008)
29. I. Ahmad, S. Hameed, H. Duddeck, S. Lenzen, I. Rustenbeck, R. Ahmad, N-arylsulfonyl-benzimi-
dazolones as potential hypoglycemic agents. Z. Naturforsch. B 57, 349 (2002)
30. M.K. Kashif, A. Hussain, M.K. Rauf, M. Ebihara, S. Hameed, 5-(4-fluorophenyl)-5-methyl-imida-
zolidine-2,4-dione. Acta Crystallogr. E64, o444 (2008)
31. E.H. Kass, B.A. Waisbren, A method for consistent induction of chronic hyperglycemia with alloxan.
Proc. Soc. Exp. Biol. Med. 60, 303 (1945)
32. R. Shukla, V. Barve, S. Padhye, R. Bhonde, Synthesis, structural properties and insulin-enhancing
potential of bis(quercetinato)oxovanadium(IV) conjugate. Bioorg. Med. Chem. Lett. 14, 4961 (2004)
123