Synthesis and antioxidant properties of α- and β-heterylamides and N-heterylimides of (±)-1,2,2-trimethylcyclopentane-1,3-dicarboxylic acid

Full text of DOI:10.1023/A:1010401827902

Pharmaceutical Chemistry Journal
Vol. 35, No. 3, 2001
SYNTHESIS AND ANTIOXIDANT PROPERTIES
OF a- AND b-HETERYLAMIDES AND N-HETERYLIMIDES
OF ( ± )-1,2,2-TRIMETHYLCYCLOPENTANE-1,3-DICARBOXYLIC ACID
S. I. Merzlikin,1 S. I. Sal’nikova,1 and F. G. Yaremenko2
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 35, No. 3, pp. 19 – 21, March, 2001.
Original article submitted April 3, 2000.
It was experimentally established that hyperglycemia is
accompanied by increased intensity of lipid peroxidation
(LPO). The administration of antioxidants leads to normal-
ization of the LPO process and decreases the blood glucose
level [1, 2]. In continuation of the search for new substances
possessing antidiabetic activity [3, 4], we have synthesized
a- and b-heterylamides and the corresponding N-im-
ides – the derivatives of ( ± )-1,2,2-trimethylcyclopenta-
ne-1,3-dicarboxylic acid (I):
in DMF. The reactions were carried out by heating the reac-
tion mixtures to 150°C for 30 min and the products were
obtained with a yield of up to 60%.
Imides IVa – IVc were synthesized by heating the corre-
sponding heterylamides for 30 min in the presence of acetyl
chloride (in a 2 : 1 ratio) in glacial acetic acid. The final
products were obtained with a yield of about 50%. The pro-
posed structures were confirmed by countersynthesis using
cyclization of the corresponding b-heterylamides Va – Vc
under analogous conditions. b-Heterylamides Va – Vc were
obtained by heating imides IVa – IVc for 2 h in a 10% aque-
ous KOH solution. These products were obtained with a
yield of up to 45%.
NH2R
COOH
NH
HOOC
COOH
O
O
O
O
The synthesized a-amides IIIa – IIIc and b-amides
Va – Vc are soluble in alcohols, acetone, and aqueous alkali
solutions. Imides IVa – IVc are soluble in alcohols and ace-
tone.
I
II
R
IIIa – IIIc
N
(a)
R =
S
In order to confirm the proposed structures of the synthe-
sized compounds, we studied their 13C and 1H NMR spectra.
The 13C NMR spectrum of acid I (dissolved in CD3OD) ex-
hibits two signals in the region corresponding to carbon at-
oms of the carbonyl groups. The low-field signal (d =
179.54 ppm) is related to the carbon atom of a carboxy group
at the quaternary carbon atom C1, while the high-field signal
(d = 177.70 ppm) is assigned to the carbon atom of a carboxy
group at C3 (Table 1). The passage to amides is usually ac-
N
H7C3
KOH
COOH
NH
O
O
N
R
O
N
N
S
(b)
R
IVa – IVc
Va – Vc
H3C
CH3
(c)
N
O
N
CH3
C6H5
TABLE 1. Chemical Shifts in the 13C NMR Spectra of the Synthe-
sized Compounds
The synthesis proceeded from heterylamines and
d,l-camphor anhydride (II) obtained by boiling acid I with a
double excess (by weight) of acetic anhydride. a-Amides
(IIIa – IIIc) were synthesized by interaction of anhydride II
with equimolar amounts of the corresponding heterylamines
d, ppm
Compound
3-CO
1-CO
C3
C1
I
177.70
173.70
173.35
177.15
179.54
179.17
177.04
175.90
53.8
54.8
57.30
57.64
56.46
57.73
IIIa
IVa
Va
55.02
53.85
1
National Pharmaceutical Academy of Ukraine, Kiev, Ukraine.
Institute for Pharmacotherapy of Endocrine Disorders, Kharkov, Ukraine.
2
139
0091-150X/01/3503-0139$25.00 © 2001 Plenum Publishing Corporation

140
S. I. Merzlikin et al.
1
TABLE 2. Parameters of the H NMR Spectra of the Synthesized
Compounds*
(in contrast to the analogous value for the a-amide IIIa) re-
mains almost unchanged (cf. d = 177.70 ppm for acid I and
177.15 ppm for compound Va), whereas the signal due to
carbon of the carbamide group at C1 significantly shifts
(Dd = 3.64 ppm) toward higher fields: from d = 179.54 ppm
for acid I to 175.90 ppm for compound Va, which confirms
the b-amide structure.
The 1H NMR spectra of the a- and b-amides also exhibit
characteristic distinctions when compared to the spectrum of
imide IVa. The main difference is that the signal due to a
C(3)H-methine proton in the spectrum of imide IVa has the
form of a quartet or triplet, while the signal of analogous protons
in a- and b-amides IIIa and Va appear as doublets (Table 2).
The IR absorption spectra most clearly reveal a differ-
ence between the structures of amides (III, V) and imides
(IV). The spectra of the latter compounds display character-
istic bands with the ns and nas frequencies of the carbonyl
groups (Table 3) significantly reduced as compared to the
analogous values for the initial anhydride II (1760 and
1800 cm – 1). The data of our spectroscopic measurements
confirm the results of calculations [4] showing evidence of a
regioselective character of the opening anhydride and
N-imide cycles in acid I.
d (ppm), multiplicity, J (Hz)
Com-
***
1 – CH3, 2.2 – (CH3)2
0.86 s, 1.28 s, 1.22 s
C(3)
2.83 q
(9.0; 9.8) 1.47 t
H
C(5)H**
C(4)H2
pound
I
2.50 t
2.10 q
1.81 q
IIa
IVa
Va
0.88 s, 1.29 s, 1.28 s
1.06 s, 1.25 s, 1.15 s
0.85 s, 1.36 s, 1.35 s
2.98 t
(7.3)
2.6 m
1.6 m
2.2 m
1.9 m
2.87 d
(6.8)
2.3 m
2.2 m
2.1 m
2.88 q 2.6 t,
(8.0, 10.0) 1.69 t
2.23 q
1.93 q
*
**
Solvent CD3OD (for I, IVa, Va) and CDCl3 (for IV).
J2 = 12.0 ± 0.2 Hz.
J2 = 13.7 ± 0.1 Hz.
***
companied by a decrease in the chemical shift for the carbon
atoms of carboxy groups [5]. In the spectrum of amide IIIa,
the chemical shift of carbon in the carboxy group at C1 re-
mains virtually unchanged (d = 179.17 ppm), while the sig-
nal due to carbon of the carbamide group at C3 exhibits a
shift by 4 ppm toward higher fields: from d = 177.70 ppm for
acid I to 173.70 ppm for compound IIIa.
The 13C NMR spectrum of imide IVa is characterized by
a decrease in the chemical shift of carbon atoms in both car-
bonyl groups relative to the value for the initial acid I, which
The results of TLC analyses confirmed the purity of the
synthesized compounds. The proposed structures are consis-
tent with the results of elemental analyses and IR spectro-
scopic measurements (Table 3).
It was a established that compounds IIIa and IVc possess
antioxidant properties comparable to those of vitamin E.
Tested under analogous conditions, the synthesized
b-heterylamides exhibited no antioxidant activity.
confirms cyclization of the a- and b-amides with the forma-
tion of imide structures. In the spectrum of b-amide Va, the
chemical shift of the carbon atom in the carboxy group at C3
TABLE 3. Yields and Physicochemical Characteristics of the Synthesized Compounds
Rf in solvent system*
M.p.,
°C
Empirical
formula
IR spectrum:
n, cm – 1
Compound
Yield, %
(1)
(2)
(3)
…
IIIa
45
216 – 219
C15H23N3O3S
0.33
0.65
1677 (nCONH); 1554 (dNH); 1718 (nC=O);
3202 (nNH
1541(dNH); 1692(nC=O); 3185 (nNH
1670 (nCONH); 1575 (dNH); 3260 (nNH
)
IIIb
IIIc
IVa
48
45
257 – 260
238 – 240
82 – 83
C13H19N3O3S
C21H27N3O4
C15H21N3O2S
0.24
0.26
0.33
0.44
0.29
0.54
0.29
…
)
)
)
58,** 56***
…
as
s
1680 (n
); 1731 (n
)
)
C=O
C=O
IVb
IVc
59,** 56***
59,** 54***
112 – 114
223 – 225
C13H17N3O2S
C21H25N3O3
0.50
0.41
0.41
0.24
0.28
…
as
s
1681 (n
); 1732 (n
C=O
C=O
as
s
1701(n
); 1742(n
)
C=O
C=O
Va
60
59
118 – 120
137 – 138
C15H23N3O3S
C13H19N3O3S
0.33
0.21
…
…
0.44
0.41
1675 (nCONH); 1555 (dNH); 3204 (nNH
Vb
1688 (nCONH); 1537 (dNH); 1722 (nC=O);
3205 (nNH
1659 (nCONH); 1574 (dNH); 1680 (nC=O);
3271 (nNH
)
Vc
*
59
215 – 216
C21H27N3O4
0.26
0.40
…
)
Rf determined in solvent systems (1) chloroform – acetone, 2 : 1; (2) chloroform – ethanol – hexane, 1 : 1 : 1; (3) carbon tetrachloride – ac-
etone, 6 : 4.
**
Yield from amides IIIa – IIIc.
***
Yield from amides Va – Vc.

Synthesis and Antioxidant Properties of a- and b-Heterylamides
141
TABLE 4. Acute Toxicity and Antioxidant Activity of Compounds
IIIa and Va
EXPERIMENTAL CHEMICAL PART
1
The H and 13C NMR spectra were measured on an
LD50 (mice)
Antioxidant effect:
XL-400 (Varian) spectrometer using CD3OD as the solvent
and TMS as the internal standard. The IR absorption spectra
were recorded on a Specord M-80 spectrophotometer using
samples pelletized with KBr. The course of reactions was
intraperito
Dose,
intragastri
Compound
MDA content,
mM
neal ad-
ministra-
tion
mg/kg
c adminis-
tration
Vitamin E + tetra-
chloromethane
monitored and purity of the reaction products was checked
by TLC on Silufol UV-254 plates (Czech Republic). The
plates were developed by treatment with Bromocresol Blue,
revealing blue spots of imides and yellow spots of amides.
The melting temperatures were determined with the aid of a
Boetius heating table. The yields and physicochemical char-
acteristics of the synthesized compounds are listed in Table 3.
The data of elemental analyses (S, N) of compounds III – V
agree with the results of analytical calculations performed
according to their empirical formulas.
50
25
“
115.0 ± 5.31**
91.3 ± 7.0**
IIIa + tetrachloro-
methane
10000
9000
2300
2000
IVc + tetrachloro-
methane
108 ± 8.20**
85.8 ± 3.22
Intact control
Tetrachloromethane
145.7 ± 6.11*
Notes. Each test group contained five animals.
*
p < 0.05 relative to intact control.
p < 0.05 relative to tetrachloromethane.
**
1,2,2-Trimethylcyclopentane-1,3-dicarboxylic
acid
( æ )-a-N-(5-propyl-1,3,4-thia-2-diazolyl)amide (IIIa). A
mixture of 1.82 g (0.01 mole) of anhydride II, 1.15 g
(0.01 mole) of 2-amino-5-propyl-1,3,4-thiadiazole, and 2 ml
of DMF was boiled for 30 min, cooled, and diluted with two
volumes of water. The precipitate was separated by filtration,
dried, and crystallized from methyl alcohol. Analogous pro-
cedures were used to obtain amides IIIb and IIIc.
model of acute toxic hepatitis induced by intragastric intro-
duction of tetrachloromethane (1 ml of 50% oil solution per
100 g body weight). The compounds studied (in a dose of
25 mg/kg) and the reference drug (vitamin E, 50 mg/kg)
were administered perorally 2 h before and 2 h after intro-
1,2,2-Trimethylcyclopentane-1,3-dicarboxylic
acid
duction of the hepatotoxic agent.
The antioxidant effect was evaluated by the decrease in
( æ )-N-(5-propyl-1,3,4-thia-2-diazolyl)imide (IVa).
M e t h o d A . A mixture of 3.25 g (0.01 mole) of amide
IIIa, 4 ml of glacial acetic acid, and 2 ml of acetyl chloride
was heated on a water bath for 30 min, cooled, and diluted
with two volumes of water. The precipitate was separated by
filtration, dried, and crystallized from methyl alcohol.
M e t h o d B . A mixture of 3.25 g (0.01 mole) of amide
Va, 4 ml of glacial acetic acid, and 2 ml of acetyl chloride
was heated on a water bath for 30 min, cooled, and diluted
with two volumes of water. The precipitate was separated by
filtration, dried, and crystallized from methyl alcohol.
Analogous procedures were used to obtain imides IVb
and IVc.
the malonic dialdehyde (MDA) content in rat liver
homogenates determined according to [6]. The acute toxicity
(LD50) was determined in mice according to [7] for the sub-
stances introduced (in the form of a 3 – 5% aqueous suspen-
sion stabilized with Tween-80) intragastrically or intraperito-
neally in a volume not exceeding 1 ml (Table 4).
REFERENCES
1. G. G. Gatsko, L. M. Mashul’, and O. V. Shablinskaya, Probl.
Endokrinol., 2, 68 – 70 (1985).
1,2,2-Trimethylcyclopentane-1,3-dicarboxylic
acid
2. M. I. Balabolkin, Diabetology [in Russian], Meditsina, Moscow
(2000), p. 672.
( æ )-b-N-(5-propyl-1,3,4-thia-2-diazolyl)amide (Va).
A
mixture of 3.07 g (0.01 mole) of imide IVa and 11.2 ml
(0.02 mole) of a 10% aqueous KOH solution was heated on a
water bath for 2 h, cooled, and acidified with diluted (1 : 1)
HCl to pH 4. The precipitate was separated by filtration,
dried, and crystallized from methyl alcohol. Analogous pro-
cedures were used to obtain amides Vb and Vc (Table 3).
3. S. I. Merzlikin, V. P. Chernikh, and O. P. Gladkikh, Visn.
Farmats., 22(2), 3 – 6 (2000).
4. S. I. Merzlikin, V. P. Chernikh, V. V. Bolotov, et al., Visn.
Farmats., 21(1), 9 – 12 (2000).
5. B. I. Ionov, B. A. Ershov, and A. I. Kol’tsov, NMR Spectroscopy
in Organic Chemistry [in Russian], Khimiya, Leningrad (1983),
p. 268.
6. I. D. Stal’naya and T. G. Garishvili, Modern Methods in Bio-
chemistry [in Russian], Meditsina, Moscow (1977), pp. 44 – 46.
7. V. V. Gatsura, Methods of Primary Pharmacological Character-
ization of Biologically Active Substances [in Russian],
Meditsina, Moscow (1974), p. 114.
EXPERIMENTAL BIOLOGICAL PART
The antioxidant activity of the synthesized compounds
was studied on Wistar rats weighing 175 – 180 g with a