Design, synthesis and hypolipidemic activity of novel 2-(m-tolyloxy) isobutyric acid derivatives

Article abstract of DOI:10.1016/j.ejmech.2008.12.009

Novel 2-substituted isobutyric acid derivatives were synthesized and their hypolipidemic activity was evaluated in high cholesterol diet fed rat model. The amide 5a was found to decrease the levels of serum total cholesterol, LDL cholesterol and triglycer

Full text of DOI:10.1016/j.ejmech.2008.12.009

European Journal of Medicinal Chemistry 44 (2009) 2679–2684
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Design, synthesis and hypolipidemic activity of novel 2-(m-tolyloxy)
isobutyric acid derivatives
*
Gamal A. Idrees, Gamal El-Din A. Abuo-Rahma , Omar M. Aly, Mohamed F. Radwan
Department of Medicinal Chemistry, Faculty of Pharmacy, Minia University, 47 Adnan El-Malky, 61519 Minia, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel 2-substituted isobutyric acid derivatives were synthesized and their hypolipidemic activity was
evaluated in high cholesterol diet fed rat model. The amide 5a was found to decrease the levels of serum
total cholesterol, LDL cholesterol and triglycerides in hyperlipidemic rats to a greater degree than the
reference gemfibrozil.
Received 19 July 2008
Received in revised form
5 November 2008
Accepted 8 December 2008
Available online 24 December 2008
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords:
Fibrates
Cholesterol
Triglycerides
Hypolipidemic
1. Introduction
The fibrates’ primary mode of action is to selectively activate the
alpha-isotype of the receptors peroxisome proliferator-activated
Derivatives of 2-methyl-2-phenoxypropanoic acid (fibric acid)
as clofibrate, bezafibrate and fenofibrate are called fibrates [1]. The
frequently prescribed hypolipidemic agent, gemfibrozil having
a 5-phenoxypentanoic acid moiety instead of the fibric acid moiety
is also considered a fibrate because of having almost similar phar-
macological properties as the other classical fibrates [2].
receptors (PPARs) [6]. Activation of PPAR-a modulates the expres-
sion of several genes involved in lipoprotein metabolism. The
activity of lipoprotein lipase is increased and results in an increase
in the clearance of circulating triglyceride-rich lipoproteins [7]. It is
established that the apolipoprotein C-III (apoC-III) inhibits lipo-
protein lipase [8]. The biosynthesis of apoC-III is decreased by
fibrates [7]. Hence, low apoC-III levels will further enhance the
clearance of triglyceride-rich lipoproteins. In addition to the anti-
hyperlipidemic effect, the fibrates have anti-inflammatory action
as evidenced by a reduction in acute phase reactants such as
C-reactive protein as well as a number of cytokines, IL-6, TNF-alpha
and interferon-gamma. This pleiotropic effect of fibrates contrib-
utes in their coronary risk reducing ability [9–11]. Moreover, several
studies indicate that fibrates decrease the levels of factors
promoting coagulation and increase fibrinolysis. The dual hypo-
lipidemic/antiplatelet effect of fibrates renders them interesting
candidates for reducing the risk of atherosclerosis and its throm-
botic complications [12], which are the major cause of coronary
artery diseases [13,14]. Recent studies revealed the ability of
fibrates to inhibit the activity of aldose reductase enzyme that
makes them reliable agents in preventing the progression of
secondary diabetic complications [15]. These interesting findings
motivated us to prepare new fibrate analogs that might hold
promising antidyslipidemic and antiatherosclerotic benefits. Our
strategy to develop new fibrates consists of modifying the fibric
acid moiety by replacing the phenyl group by an m-tolyl one and
O
O
O
O
OH
O
O
N
H
Cl
Cl
Bezafibrate
Clofibrate
O
O
O
OH
Cl
O
O
C
O
Gemfibrozil
Fenofibrate
In general, the major lipoprotein effects of fibrates are to reduce
the levels of plasma triglycerides by 30–50% and to increase levels of
HDL cholesterol by 5–6%. The magnitude of their effect is directly
related to the severity of lipoprotein abnormalities at baseline [3–5].
* Corresponding author. Tel.: þ20 103069431; fax: þ20 862369075.
E-mail address: gamalaburahma@yahoo.com (G.E.-DinA. Abuo-Rahma).
0223-5234/$ – see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.12.009

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G.A. Idrees et al. / European Journal of Medicinal Chemistry 44 (2009) 2679–2684
the carboxyl function by selected bulkier derivatives and studying
the impact of such modifications on the hypolipidemic activity.
attempts to cyclize the 1,4-disubstituted thiosemicarbazides 6a,b
into the corresponding mercaptotriazoles by piperidine in ethanol
or aqueous 2 N sodium hydroxide or sodium metal in methanol,
were all unsuccessful. This might be explained by the steric
hindrance created by the two methyl groups on the carbon alpha to
the carbonyl group which in turn prevents the intramolecular
cyclization.
2. Results and discussion
2.1. Chemistry
Regarding the prepared arylidenes 4a–d, it was noticed that
aromatic carbonyl compounds having electron-withdrawing
substituents (e.g. NO2 and Cl) give higher yields than those having
electron-releasing ones (e.g. OCH3). This could be explained by the
ability of electron attractors to intensify the positive charge on the
carbonyl carbon thereby increasing its susceptibility for nucleo-
philic attack while electron donors are likely to neutralize that
positive charge with the result that the carbonyl carbon becomes
less attractive to nucleophiles.
The syntheses of the designed compounds are outlined in
Scheme 1. Following reported procedures, treating m-cresol with
acetone and chloroform in the presence of sodium hydroxide
afforded 2-(m-tolyloxy)isobutyric acid 1 that was converted into
the hydrazide 3 by treating its ethyl ester 2 with hydrazine hydrate
[16]. Condensation of the hydrazide 3 with the appropriate
carbonyl compounds afforded the arylidenes 4a–d. The acid 1 was
converted to the corresponding carboxamides 5a–c by the mixed
anhydride method using ethyl chloroformate [17]. The desired 1,4-
disubstituted thiosemicarbazides 6a,b were obtained by treating
the hydrazide 3 with the appropriate alkyl isothiocyanate. Our
The structures of the prepared compounds were substantiated
by 1H NMR, 13C NMR spectra as well as elemental microanalyses.
O
OH
+
CHCl3
+
CH3
H3C
H3C
i. NaOH
ii. HCl
CH3
O
COOH
CH3
H3C
1
EtOH
c
°
H2SO4
5
-
0
/
N
)
t
CH3
E
(
/
t
O
COOC2H5
E
O
O
CH3
C
l
C
C
H3
2
O
O
CH3
CH3
NH2NH2.H2O
O
C
O
C
OEt
H3C
CH3
O
C
O
NHNH2
CH3
RNH2
H3C
3
CH3 O
O
C
NHR
RNCS
RCHO
CH3
H3C
5a-c
CH3
CH3
O
C
5a; R= p-(OCH3)C6H4
5b; R= p-(COOCH2CH3)C6H4
5c; R= C6 H5CH2CH2
CH3
O
C
S
O
O
NHN
CHR
NHNH C
CH3
H3C
NHR
H3C
4a-d
4a; R= C6H5
6a-b
4b; R= p-(OCH3)C6H4
4c; R= p-(NO2)C6H4
4d; R=o-(Cl)C6 H4
6a; R= CH3CH2
6b; R= CH2=CH-CH2
Scheme 1.

G.A. Idrees et al. / European Journal of Medicinal Chemistry 44 (2009) 2679–2684
2681
The 1H NMR spectra of the arylidenes 4a–d are characterized by the
presence of azomethine and amidic protons in the range of 8.09–
8.35 ppm and 8.59–10.04 ppm, respectively, whereas their 13C NMR
spectra show a characteristic azomethine carbon (CH]N) ranging
from 146.9 to 148.8 ppm. The appearance of amidic proton at 8.49–
9.11 ppm is a hallmark of the 1H NMR spectra of the amides 5a–c.
An interesting finding in the 1H NMR spectrum of compound 5c is
that it contains a quartet of 2 protons at 3.60 ppm for the methylene
group attached to NH that could be explained by the slow exchange
rate of the NH proton allowing splitting of the methylene proton
signals by the adjacent NH and CH2. The 1H NMR spectra of
compounds 6a,b showed 3 amidic NH protons beyond 7 ppm.
Furthermore, the 13C NMR spectra of compounds 6a,b showed
a characteristic thione (C]S) around 181 ppm. The 13C NMR spectra
of all synthesized compounds show a characteristic C]O group
above 170 ppm.
the tissues and is responsible for the atherogenesis process [19].
Decreasing the ratio of LDL-C (bad cholesterol) to that of HDL-C
(good cholesterol) plays a pivotal role in reducing the risk of
atherosclerosis [20]. Results showed that the lowest LDL-C/HDL-C
ratio was obtained by compound 5a.
3. Experimental
3.1. Chemistry
Melting points were determined on Stuart electrothermal
melting point apparatus and were uncorrected. 1H NMR spectra
were recorded on a JEOL Lambda 600 spectrometer (600 MHz), on
a Mercury 300BB NMR spectrometer (300 MHz), and on a GEMINI-
200 NMR spectrometer (200 MHz) with TMS as internal standard
and CDCl3 as a solvent. 13C NMR spectra were recorded on a JEOL
Lambda 600 spectrometer (600 MHz) with TMS as internal
standard and CDCl3 as a solvent. Elemental microanalysis was
performed on Hereaus Vario EL apparatus.
2.2. Hypolipidemic activity
The hypolipidemic activity of the synthesized compounds was
studied in the high cholesterol diet (HCD) fed hyperlipidemic rat
model [18] against hyperlipidemic control [i.e., rats fed with HCD
and given drug vehicle (0.5% CMC) only], by oral administration of
20 mg/kg of the compounds. The results were compared with
that obtained by the reference hypolipidemic agent gemfibrozil
(Table 1). The obtained results revealed that feeding rats with high
cholesterol diet for 14 days significantly elevated the serum level of
total cholesterol, triglycerides and LDL-C by 59.58%, 71.76% and
102.36%, respectively, when compared with normal control rats.
Moreover, induction of hyperlipidemia significantly decreased
serum HDL-C level by 34.77% from that of normal control rats. The
obtained data revealed that the tested compounds produced vari-
able effects on the serum levels of TC (Fig. 1), TG (Fig. 2), and LDL-C
(Fig. 3), as compared with the hyperlipidemic control group.
Compound 5a exhibited the maximum hypolipidemic activity
expressed as 23.24% and 25.97% reduction in the levels of TC and TG,
respectively, that was more active than the reference gemfibrozil
which afforded 4.68% and 22.23% reduction in the levels of TC and
TG, respectively. The acid 1 was effective in reducing the levels of TC
and TG by 15.89% and 17.98%, respectively, while compound 5c
reduced only TC by 12.95%. No significant lipid lowering activity was
produced by either the arylidenes 4a–d or the 1,4-disubstituted
thiosemicarbazides 6a,b. Also, there was no significant change in
HDL-C values in any of the treated animals (Fig. 4). The reduction of
the level of LDL-C (28.67%) by compound 5a is an interesting finding
because the LDL fraction is generally thought to carry cholesterol to
3.1.1. General procedure for the preparation of 2-methyl-2-m-
tolyloxypropionic acid (arylidene)hydrazides (4a–d)
A mixture of 2-methyl-2-m-tolyloxypropionic acid hydrazide
(2.08 g, 10 mmol) and the appropriate carbonyl compound
(10 mmol) in absolute ethanol (20 mL) was heated at reflux for 3 h.
The reaction mixture was cooled and the precipitated solid was
filtered off, dried and recrystallized from ethanol.
3.1.1.1. 2-Methyl-2-m-tolyloxypropionic acid benzylidene hydrazide
(4a). Colorless solid; m.p. 139–140 ꢀC; yield 70% (2.07 g); 1H NMR
(CDCl3, 200 MHz,
CH3), 6.80–7.80 (m, 9H, Ar-H), 8.17 (s, 1H, azomethine proton), 9.80
(s, 1H, NH); 13C NMR (CDCl3, 600 MHz,
, ppm): 21.5 (Ar-CH3), 25.2
d, ppm): 1.62 (s, 6H, O–C(CH3)2), 2.36 (s, 3H, Ar-
d
(O–C(CH3)2), 81.7 (O–C(CH3)2), 118.8, 122.7, 124.8, 127.9, 128.8,
129.2, 130.7, 133.6, 139.7 and 153.8 (aromatic carbons), 148.8
(CH]N), 171.2 (C]O); Anal. Calcd. for C18H20N2O2 (%): C, 72.95; H,
6.80; N, 9.45. Found: C, 73.06; H, 6.51; N, 9.12.
3.1.1.2. 2-Methyl-2-m-tolyloxypropionic acid (4-methoxybenzylidene)
hydrazide (4b). Colorless solid; m.p. 134–136 ꢀC; yield 69% (2.25 g);
1H NMR (CDCl3, 200 MHz,
d
, ppm): 1.61 (s, 6H, O–C(CH3)2), 2.34 (s, 3H,
Ar-CH3), 3.85 (s, 3H, OCH3), 6.79–7.74 (m, 8H, Ar-H), 8.09 (s, 1H,
azomethine proton), 9.73 (s, 1H, NH); 13C NMR (CDCl3, 600 MHz,
d,
ppm): 21.5 (Ar-CH3), 25.2 (O–C(CH3)2), 55.4 (OCH3), 81.7 (O–C(CH3)2),
114.2, 118, 122.7, 124.7, 126.2, 129.2, 129.5, 139.6, 153.8 and 161.7
(aromatic carbons), 148.6 (CH]N), 170.9 (C]O); Anal. Calcd. for
Table 1
Effect of tested compounds on lipid profile of hyperlipidemic rats.
Groups
TC (mg/dL)
% Fall
TG (mg/dL)
% Fall
HDL-C (mg/dL)
% Rise
LDL-C (mg/dL)
% Fall
LDL/HDL
Control
HCD fed
71.0 ꢁ 2.65
113.3 ꢁ 3.22
108.0 ꢁ 8.54
95.33 ꢁ 4.73**
108.7 ꢁ 2.52
113.3 ꢁ 6.51
113.0 ꢁ 9.54
120.7 ꢁ 4.73
87.00 ꢁ 4.58**
110.3 ꢁ 10.50
98.67 ꢁ 2.52
114.0 ꢁ 7.55
115.3 ꢁ 5.69
55.0 ꢁ 5.57
94.47 ꢁ 3.25
73.47 ꢁ 3.14**
77.48 ꢁ 9.28*
92.07 ꢁ 3.72
95.72 ꢁ 6.53
95.26 ꢁ 2.63
85.94 ꢁ 8.91
70.11 ꢁ 4.49**
94.06 ꢁ 5.54
93.34 ꢁ 3.52
89.33 ꢁ 2.00
95.99 ꢁ 4.58
19.67 ꢁ 5.13
12.83 ꢁ 2.02
16.07 ꢁ 1.01
14.21 ꢁ 0.79
15.20 ꢁ 1.31
14.70 ꢁ 1.54
14.00 ꢁ 0.89
14.87 ꢁ 0.81
14.80 ꢁ 0.57
14.77 ꢁ 0.91
15.72 ꢁ 0.67
13.58 ꢁ 0.73
13.70 ꢁ 1.32
40.33 ꢁ 2.64
81.61 ꢁ 1.67
77.24 ꢁ 9.77
65.63 ꢁ 3.15
75.05 ꢁ 1.53
79.49 ꢁ 6.26
79.95 ꢁ 9.03
89.28 ꢁ 5.00
58.18 ꢁ 6.35**
76.75 ꢁ 12.50
64.28 ꢁ 2.63*
82.55 ꢁ 7.65
82.43 ꢁ 4.99
2.05
6.36
4.81
4.62
4.94
5.41
5.71
6.00
3.93
5.20
4.09
6.08
6.02
HCD fed þ gemfibrozil
HCD fed þ 1
HCD fed þ 4a
HCD fed þ 4b
HCD fed þ 4c
HCD fed þ 4d
HCD fed þ 5a
HCD fed þ 5b
HCD fed þ 5c
HCD fed þ 6a
HCD fed þ 6b
4.68
15.89
4.12
22.23
17.98
2.54
25.18
10.68
18.47
14.58
9.12
15.82
15.28
15.04
22.45
5.85
5.35
19.56
8.02
0.00
0.29
ꢂ1.32a
ꢂ0.84a
9.03
2.60
2.30
ꢂ6.47a
23.24
2.65
ꢂ9.39a
28.67
5.94
25.79
0.43
1.20
12.95
ꢂ0.59
ꢂ1.77a
21.21
ꢂ1.16a
ꢂ1.00a
5.44
ꢂ1.61a
6.78
TC, total cholesterol; TG, triglycerides; HDL-C, high density lipoprotein cholesterol; LDL-C, low density lipoprotein cholesterol.
*Significantly different from hyperlipidemic control group at P < 0.05.
**Significantly different from hyperlipidemic control group at P < 0.01.
a
Negative values indicate increase in the level of the measured parameter % fall and % rise are calculated for groups in relation to the hyperlipidemic control group.

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G.A. Idrees et al. / European Journal of Medicinal Chemistry 44 (2009) 2679–2684
125
100
75
50
25
0
100
75
50
25
0
Fig. 1. Effect of the tested compounds and gemfibrozil on serum TC of hyperlipidemic
rats.
Fig. 3. Effect of the tested compounds and gemfibrozil on serum LDL-C of hyper-
lipidemic rats.
C19H22N2O3 (%): C, 69.92; H, 6.79; N, 8.58. Found: C, 69.87; H, 6.91;
N, 8.37.
124.2, 126.5, 128.7, 129.6, 130.8, 131.5, 132.3, 133.1, 136.5, 141.5 and
155.4 (aromatic carbons), 146.9 (CH]N), 173.8 (C]O); Anal. Calcd.
for C18H19ClN2O2 (%): C, 65.35; H, 5.79; N, 8.47. Found: C, 65.29; H,
5.63; N, 8.29.
3.1.1.3. 2-Methyl-2-m-tolyloxypropionic acid (4-nitrobenzylidene)
hydrazide (4c). Yellow solid; m.p. 156–157 ꢀC; yield 76% (2.60 g); 1H
NMR (CDCl3, 200 MHz,
Ar-CH3), 6.78–8.29 (m, 8H, Ar-H), 8.35 (s, 1H, azomethine proton),
10.04 (s, 1H, NH); 13C NMR (CDCl3, 600 MHz,
, ppm): 21.5 (Ar-CH3),
d, ppm): 1.62 (s, 6H, O–C(CH3)2), 2.35 (s, 3H,
3.1.2. General procedure for the preparation of 2-methyl-2-m-
tolyloxy-N-substituted propionamides (5a–c)
d
25.2 (O–C(CH3)2), 81.8 (O–C(CH3)2), 118.9, 122.8, 124.1, 125.0, 128.3,
129.2, 139.8, 145.9 and 153.5 (aromatic carbons), 148.8 (CH]N),
171.6 (C]O); Anal. Calcd. for C18H19N3O4 (%): C, 63.33; H, 5.61; N,
12.31. Found: C, 63.11; H, 5.54; N, 12.34.
To a stirred solution of 2-methyl-2-m-tolyloxypropionic acid
(1.94 g, 10 mmol), in 30 ml dry chloroform at 0–5 ꢀC, triethylamine
(1.01 g, 10 mmol) was added, followed by ethyl chloroformate
(1.08 g, 10 mmol) in a drop wise manner, the mixture was stirred in
the ice bath for 30 min, and then the appropriate amine (10 mmol)
in dry chloroform was added drop wise. The mixture was stirred for
additional 12 h at room temperature, the solvent was evaporated
under reduced pressure and the crude product was dissolved in
30 ml chloroform, washed with water (2 ꢃ 30 ml), 5% NaHCO3
solution (2 ꢃ 20 ml), 1 N HCl (2 ꢃ 20 ml), water (2 ꢃ 30 ml) and
3.1.1.4. 2-Methyl-2-m-tolyloxypropionic acid (2-chlorobenzylidene)
hydrazide (4d). Colorless solid; m.p. 140–142 ꢀC; yield 75% (2.48 g);
1H NMR (CDCl3, 200 MHz,
d
, ppm): 1.60 (s, 6H, O–C(CH3)2), 2.35 (s,
3H, Ar-CH3), 6.81–7.34 (m, 8H, Ar-H), 8.23 (s, 1H, azomethine
proton), 8.59 (s, 1H, NH); 13C NMR (CDCl3, 600 MHz,
, ppm): 21.5
d
(Ar-CH3), 25.2 (O–C(CH3)2), 55.4 (OCH3), 81.7 (O–C(CH3)2), 119.2,
25
20
15
10
5
100
75
50
25
0
0
Fig. 2. Effect of the tested compounds and gemfibrozil on serum TG of hyperlipidemic
Fig. 4. Effect of the tested compounds and gemfibrozil on serum HDL-C of hyper-
rats.
lipidemic rats.

G.A. Idrees et al. / European Journal of Medicinal Chemistry 44 (2009) 2679–2684
2683
finally with brine (2 ꢃ 30 ml). The organic layer was dried over
anhydrous sodium sulfate and evaporated under reduced pressure.
The product was collected and recrystallized from aqueous ethanol.
Calcd. for C15H21N3O2S (%): C, 58.61; H, 6.89; N, 13.67. Found: C,
58.26; H, 7.30; N, 13.61.
3.2. Hypolipidemic activity
3.1.2.1. N-(4-Methoxyphenyl)-2-methyl-2-m-tolyloxypropionamide
(5a). Colorless solid; m.p. 125–126 ꢀC; yield 74% (2.22 g); 1H NMR
Male albino rats of Wistar strain weighing 160–180 g were used
in this study. Rats were obtained from the animal house of National
Research Centre, Dokki, Cairo. The animals were kept for one week
in the laboratory under 12 h day and night cycle for accommodation
with free access to food and water ad libitum. Rats were divided into
control (fed normal rodent chow), hyperlipidemic control and
hyperlipidemic plus compound treated groups. Each group con-
sisted of six animals. Hyperlipidemia was induced by feeding rats
with high cholesterol diet (HCD) prepared by mixing normal rodent
chow with 2% cholesterol (Sigma, USA) and 1% cholic acid (Sigma,
USA). Hyperlipidemic rats had a free access to the HCD and water ad
libitum during the entire period of the experiment. The tested
compounds as well as the standard drug gemfibrozil were given
orally at a dose of 20 mg/kg using 0.5% carboxymethylcellulose as
a drug vehicle from day 8 to day 14 (7 days) in the HCD fed rats.
Control and hyperlipidemic control rats (fed with HCD) received
only the drug vehicle from day 8 to day 14 of the experiment. At the
end of the experiment, that is, on the 14th day, the animals were
fasted for 12 h and the tail blood was collected under mild ether
anesthesia. Serum was separated by centrifugation at 3000 rpm for
10 min for measurement of total cholesterol (TC), triglycerides (TGs)
and HDL cholesterol (HDL-C) using Randox kits (UK) on a Jenway
UV–vis spectrophotometer. Serum LDL–cholesterol concentration
was determined according to Friedewald’s formula [21].
(CDCl3, 200 MHz,
CH3), 3.81 (s, 3H, OCH3), 6.79–7.51 (m, 8H, Ar-H), 8.49 (s, 1H, NH);
13C NMR (CDCl3, 600 MHz,
, ppm): 21.5 (Ar-CH3), 25.2 (O–C(CH3)2),
d, ppm): 1.59 (s, 6H, O–C(CH3)2), 2.34 (s, 3H, Ar-
d
55.6 (OCH3), 81.9 (O–C(CH3)2), 114.3, 118.8, 121.6, 122.7, 124.7, 129.1,
130.8, 139.6, 154.1 and 156.6 (aromatic carbons), 172.9 (C]O); Anal.
Calcd. for C18H21NO3 (%): C, 72.22; H, 7.07; N, 4.68. Found: C, 72.27;
H, 7.14; N, 4.49.
3.1.2.2. 4-(2-Methyl-2-m-tolyloxypropionylamino)benzoic acid ethyl
ester (5b). Colorless solid; m.p. 118–120 ꢀC; yield 62% (2.11 g); 1H
NMR (CDCl3, 200 MHz,
d
, ppm): 1.70 (t, 3H, J ¼ 7 Hz, COOCH2CH3),
1.88 (s, 6H, O–C(CH3)2), 2.64 (s, 3H, Ar-CH3), 4.65 (q, 2H, J ¼ 7 Hz,
COOCH2CH3), 7.07–8.36 (m, 8H, Ar-H), 9.11 (s, 1H, NH); 13C NMR
(CDCl3, 600 MHz, d, ppm): 14.4 (CH3CH2), 21.5 (Ar-CH3), 25.1 (O–
C(CH3)2), 61.0 (CH3CH2), 82.0 (O–C(CH3)2), 118.96, 118.99, 122.91,
124.99, 126.2, 129.2, 130.9, 139.7, 141.7 and 153.7 (aromatic
carbons), 166.21 (CONH), 173.5 (COO); Anal. Calcd. for C20H23NO4
(%): C, 70.36; H, 6.79; N, 4.10. Found: C, 70.31; H, 6.96; N, 3.89.
3.1.2.3. 2-Methyl-N-phenethyl-2-m-tolyloxypropionamide (5c). Col-
orless solid; m.p. 124–126 ꢀC; yield 66% (1.96 g); 1H NMR (CDCl3,
200 MHz, d, ppm): 1.51 (s, 6H, O–C(CH3)2), 2.34 (s, 3H, Ar-CH3), 2.86
(t, 2H, J ¼ 7 Hz, CH2CH2NH), 3.60 (q, 2H, J ¼ 7 Hz, CH2CH2NH),
6.66–7.31 (m, 9H, 8 Ar-H þ NH); 13C NMR (CDCl3, 600 MHz,
d, ppm):
The results obtained were expressed as mean ꢁ SD. The differ-
ence between the groups was evaluated for its significance by one-
way ANOVA test. Mean, standard deviation calculations and ANOVA
test were performed using ‘‘GraphPad Prism version 4.0’’ software.
A P value < 0.05 was considered significant.
21.5 (Ar-CH3), 25.2 (O–C(CH3)2), 35.8 (ArCH2), 40.5 (CH2NH), 81.4
(O–C(CH3)2), 118.1, 122.0, 124.0, 126.6, 128.7, 128.8, 129.0, 138.9,
139.4 and 154.3 (aromatic carbons), 174.9 (C]O); Anal. Calcd.
for C19H23NO2 (%): C, 76.73; H, 7.80; N, 4.71. Found: C, 76.82; H, 7.67;
N, 4.54.
4. Conclusion
3.1.3. General procedure for the preparation of 1-(2-methyl-2-m-
tolyloxy)propionyl-4-substituted thiosemicarbazides (6a,b)
Novel 2-substituted isobutyric acid derivatives were prepared
and their hypolipidemic activity was screened in hyperlipidemic
rats. Among the synthesized compounds, the amide 5a was found
to be the most active hypolipidemic agent affording significant
hypocholesterolemic and hypotriglyceridemic activities and seems
to be a good candidate for developing a new strong fibrate deriv-
ative with good hypolipidemic and antiatherosclerotic benefits.
A mixture of 2-methyl-2-m-tolyloxypropionic acid hydrazide
(2.08 g, 10 mmol) and the appropriate alkyl isothiocyanate
(10 mmol) in absolute ethanol was refluxed for 4 h. The mixture
was cooled and the precipitated solid was filtered, dried and
recrystallized from methanol to give the title compounds.
3.1.3.1. 1-(2-Methyl-2-m-tolyloxypropionyl)-4-ethylthiosemicarbazide
(6a). Colorless solid; m.p. 140–142 ꢀC; yield 75% (2.21 g); 1H NMR
Acknowledgement
(CDCl3, 300 MHz,
d
, ppm): 1.15 (t, 3H, J ¼ 6.9 Hz, CH2CH3), 1.56 (s, 6H,
O–C(CH3)2), 2.34 (s, 3H, Ar-CH3), 3.56 (q, 2H, J ¼ 6.9 Hz, CH2CH3),
6.92–7.27 (m, 5H, 4 Ar-H þ NH), 9.09 (s, 1H, NH), 9.59 (s, 1H, NH);
The authors are grateful to Prof. Dr. Jochen Lehmann, Institute of
Pharmacy, Department of Pharmaceutical/Medicinal Chemistry,
Friedrich-Schiller University, Jena, Germany, for carrying out the
elemental microanalysis.
13C NMR (CDCl3, 600 MHz,
d, ppm): 14.6 (CH2-CH3), 21.5 (Ar-CH3),
25.3 (O–C(CH3)2), 41.6 (CH2-CH3), 81.0 (O–C(CH3)2), 115.7, 120.6,
123.0, 127.5, 136.4 and 150.5 (aromatic carbons), 170.5 (C]O), 181.5
(C]S); Anal. Calcd. for C14H21N3O2S (%): C, 56.92; H, 7.17; N, 14.22.
Found: C, 56.82; H, 7.26; N, 14.04.
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