Modification of the anticestodal drug 5-chloro-N-(2-chloro-4-nitrophenyl)- 2-hydroxybenzamide with a view to improve its biological effect

Article abstract of DOI:10.1134/S1070428014060074

Reactions of 5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide, the active substance of the drug Niclosamide (Phenasal), with higher amines (dodecan-1-amine, hexadecan-1-amine) and 1-(2-aminoethyl)-piperazine lead to the formation of the corresponding water-soluble ammonium salts with retention of pharmacophoric groups responsible for the antihelminthic effect, whereas no nucleophilic aromatic substitution of chlorine is observed. The product structure was determined by X-ray analysis.

Full text of DOI:10.1134/S1070428014060074

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 6, pp. 800–804. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © I.V. Galkina, D.R. Chubukaeva, Yu.V. Bakhtiyarova, V.I. Galkin, R.A. Cherkasov, D.R. Islamov, and O.N. Kataeva, 2014, published
in Zhurnal Organicheskoi Khimii, 2014, Vol. 50, No. 6, pp. 818–822.
Dedicated to Full Member of the Russian Academy of Sciences
O.N. Chupakhin on his 80th anniversary
Modification of the Anticestodal Drug
5-Chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide
with a View to Improve Its Biological Effect
I. V. Galkinaa, D. R. Chubukaevaa, Yu. V. Bakhtiyarovaa, V. I. Galkina, R. A. Cherkasova,
D. R. Islamova, and O. N. Kataevab
a Kazan (Volga Region) Federal University, ul. Kremlevskaya 18, Kazan, 420008 Tatarstan, Russia
e-mail: vig54@mail.ru
b Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences,
ul. Arbuzova 8, Kazan, 420088 Tatarstan, Russia
Received February 23, 2014
Abstract—Reactions of 5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide, the active substance of the
drug Niclosamide (Phenasal), with higher amines (dodecan-1-amine, hexadecan-1-amine) and 1-(2-aminoethyl)-
piperazine lead to the formation of the corresponding water-soluble ammonium salts with retention of
pharmacophoric groups responsible for the antihelminthic effect, whereas no nucleophilic aromatic substitution
of chlorine is observed. The product structure was determined by X-ray analysis.
DOI: 10.1134/S1070428014060074
Phenasal [I, Niclosamide, 5-chloro-N-(2-chloro-4-
nitrophenyl)-2-hydroxybenzamide] is the only fairly
accessible home-made drug active against cestodes
(tape warms inducing helminthoses in animals and
humans) [1]. Unfortunately, compound I is insoluble in
water, and its efficiency does not exceed 70–80%.
a lipid membrane anchor, such as higher aliphatic
amines with an alkyl chain length of C12 and C16. We
believed that such modification of Phenasal should
endow it with improved solubility and enhanced ability
to be embedded into parasite cell membrane and
destroy it, thus favoring both death of helminths and
considerable deterioration of their life cycle from
mature egg to invasive plerocercoids which are capa-
ble of developing both through intermediate hosts and
in the lungs of the main host.
Among other goals, the present study was aimed
at synthesizing new bioavailable and water-soluble
modifications of Phenasal possessing a lipophilic an-
choring group to fix them on biomembranes of para-
sites and their larvae, which should lead to biomem-
brane degradation, penetration of host digestive juice
into parasites, and hence death of the latter. A potential
drug can be fixed in the parasite body with the aid of
Compound I was treated with 2 equiv of dodecan-
1-amine (II) and hexadecan-1-amine (III) in anhy-
drous ethanol at room temperature. However, the reac-
tion gave not the expected chlorine substitution prod-
Scheme 1.
NO2
NO2
OH
O
O–
O
N
N
+
RNH2
RNH3
H
H
Cl
Cl
Cl
Cl
I
II, III
IV, V
II, IV, R = C12H25; III, V, R = C16H33.
800

MODIFICATION OF THE ANTICESTODAL DRUG
(a)
801
(b)
N
Cl
O
O
N
N
Cl
O
O
Fig. 1. (a) Structure of the molecule of dodecan-1-aminium 4-chloro-2-[(2-chloro-4-nitrophenyl)carbamoyl]phenoxide (IV) and
(b) a fragment of its crystal packing according to the X-ray diffraction data.
(a)
(b)
O
Cl
N
Cl
O
O
N
O
Fig. 2. (a) Structure of the molecule of hexadecan-1-aminium 4-chloro-2-[(2-chloro-4-nitrophenyl)carbamoyl]phenoxide (V) and
(b) a fragment of its crystal packing according to the X-ray diffraction data.
ucts but water-soluble ammonium salts IV and V with
retention of pharmacophoric groups responsible for the
antihelminthic effect. The yield of IV and V was about
~80% (Scheme 1). The structure, purity, and stability
of compounds IV and V were examined by physical,
physicochemical, and chemical methods, IR spectros-
copy, thermogravimetry in combination with differen-
tial scanning calorimetry (TG-DSC), and elemental
and X-ray analyses.
data for its water-soluble form [3] which is necessary
for devastation of helminth larvae (coracidia, procer-
coids, and plerocercoids) inhabiting out of intestine, in
biological fluids of animals and humans.
The X-ray analysis data for compounds IV and V
confirmed the formation of water-soluble ammonium
salts with retention of pharmacophoric groups inherent
to Phenasal (Figs. 1, 2).
One more modification of Phenasal was accom-
plished using 1-(2-aminoethyl)piperazine (VI) which
is a substituted analog of piperazine and piperazine
adipate that are well known antinematodal agents [4].
Such modification extends the spectrum of antipara-
sitic activity and gives rise to a new agent active
against cestodes and nematodes simultaneously.
The IR spectra of salts IV and V contained charac-
teristic absorption bands in the regions 3366–2800
(NH), 1650 (C=O), 1510, 1250 (NO2), and 740 cm–1
(C–Cl). The purity and thermal stability of IV and V
(up to 148.2 and 167.7°C, respectively) were proved
by the TG–DSC method.
The X-ray diffraction data for Phenasal were re-
ported in [2]; however, there are no X-ray diffraction
By reaction of Phenasal (I) with 1-(2-aminoethyl)-
piperazine (VI) in anhydrous ethanol at room tempera-
Scheme 2.
NO2
O
O
NH2
NH3
N
N
N
+
2I
·
H
HN
H2N
Cl
Cl
2
VI
VII
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 6 2014

GALKINA et al.
802
EXPERIMENTAL
Cl
N
The IR spectra were recorded on Specord M-80 and
Thermo Avatar 360 FT-IR spectrometers from samples
dispersed in mineral oil. The purity and thermal stabil-
ity of the products were studied by simultaneous TG–
DSC using a NETZSCH STA 449C TGA/S6TA85/E
instrument (temperature range 20–400°C, heating rate
10 deg/min, argon atmosphere). The solvents used
were purified according to standard procedures [5]. All
initial reactants were distilled and purified just before
use; their purity was checked by comparing their
physical constants with published data.
N
N
O
O
N
O
O
O
N
Cl
Cl
O
N
O
N
O
Cl
Dodecan-1-aminium 4-chloro-2-[(2-chloro-4-
nitrophenyl)carbamoyl]phenoxide (IV). A solution
of 0.370 g (2 mmol) of amine II in 30 mL of
anhydrous ethanol was added at 20°C to a solution of
0.327 g (1 mmol) of amide I in 30 mL of the same
solvent, and the resulting red mixture was left to stand
for 14 days to complete the reaction. The red crystals
were filtered off and repeatedly washed with anhy-
drous ethanol and diethyl ether. Yield 0.43 g (84%),
mp 148°C. IR spectrum, ν, cm–1: 3366–2800 (NH);
1650 (C=O); 1510, 1250 (NO2); 740 (C–Cl). Found,
%: C 58.37; H 7.12; N 8.27. C25H35Cl2N3O4. Calculat-
ed, %: C 58.59; H 6.84; N 8.20.
Fig. 3. Structure of the molecule of 4-(2-ammonioethyl)-
piperazin-1-ium bis{4-chloro-2-[(2-chloro-4-nitrophenyl)-
carbamoyl]phenoxide} (VII) according to the X-ray diffrac-
tion data.
ture we obtained 74% of bisammonium salt VII con-
sisting of one molecule of VI (dication) and two mole-
cules of I (anion; Scheme 2). The IR spectrum of VII
contained absorption bands typical of functional
groups present therein. The purity and thermal stability
of VII (up to 228°C) were determined by simultaneous
TG–DSC analysis.
The formation of water-soluble bis-ammonium salt
VII with retention of pharmacophoric groups was con-
firmed by X-ray analysis (Fig. 3).
Hexadecan-1-aminium 4-chloro-2-[(2-chloro-4-
nitrophenyl)carbamoyl]phenoxide (V). A solution of
0.482 g (2 mmol) of amine III in 30 mL of anhydrous
ethanol was added at 20°C to a solution of 0.327 g
(1 mmol) of amide I in 40 mL of the same solvent.
After 14 days, the product was isolated as described
above for salt IV. Yield 0.46 g (81%), mp 167.7°C. IR
spectrum, ν, cm–1: 3366–2800 (NH); 1650 (C=O);
1510, 1250 (NO2); 740 (C–Cl). Found, %: C 61.30;
H 7.62; N 7.38. C29H43Cl2N3O4. Calculated, %:
C 61.27; H 7.54; N 7.39.
The Phenasal anions in the crystal structures of IV,
V, and VII are almost planar, as in parent molecule I
[2]. Deprotonation of the phenolic hydroxy group leads
to shortening of the C–O bond to 1.306–1.318(3) Å
against 1.354(3) Å in the neutral molecule. The ammo-
nium groups in all crystalline salts IV, V, and VII are
involved in numerous hydrogen bonds with oxygen
atoms, the strongest bonds being those formed with the
anionic oxygen atom; the N···O– distance ranges from
2.58 to 2.71 Å, and the distance between the ammoni-
um nitrogen atoms and oxygen atoms in the carbonyl
and nitro groups varies within 2.96–3.01 Å.
4-(2-Ammonioethyl)piperazin-1-ium bis-
{4-chloro-2-[(2-chloro-4-nitrophenyl)carbamoyl]-
phenoxide} (VII). A solution of 0.129 g (1 mmol) of
diamine VI in 10 mL of anhydrous ethanol was added
dropwise under stirring at 20°C to a solution of 0.654 g
(2 mmol) of amide I in 20 mL of the same solvent. The
red mixture was stirred for 2 h and was left to stand for
14 days to complete the reaction. The orange crystals
were filtered off and washed with ethanol and diethyl
ether. Recrystallization from chloroform–hexane gave
an oily material which was kept for 2 months in
a crystallizer; orange crystal druses were formed. Yield
0.577 g (74%), mp 228°C. IR spectrum, ν, cm–1: 3370–
The crystal packing of ammonium salts IV and V
with higher alkyl substituents on the nitrogen is
characterized by alternation of hydrophilic and hydro-
phobic layers. In the crystal structure of salt IV with
dodecyl substituent transoid conformation in the
middle of the hydrocarbon chain is distorted, and the
ammonium group is oriented gauche, which favors
intermolecular hydrogen bonding. The long-chain
alkyl substituent in V in crystal has an ideal transoid
conformation.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 6 2014

MODIFICATION OF THE ANTICESTODAL DRUG
Crystallographic and refinement parameters for structures IV, V, and VII
803
Parameter
IV
C13H7Cl2N2O4·C12H28N
512.46
V
VII
Formula
C13H7Cl2N2O4·C16H36N 2(C13H7Cl2N2O4)·C6H17N3
Molecular weight
568.56
Triclinic
P1¯
783.44
Triclinic
P1¯
Crystal system
Triclinic
Space group
P1¯
Unit cell parameters:
a, Å
08.2292(2)
15.1823(4)
22.1426(7)
104.662(2)
92.365(2)
103.9930(10)
2581.43(12)
4
08.0449(8)
11.4595(7)
16.707(1)
93.372(2)
91.942(2)
98.790(4)
1518.1(2)
2
09.0428(9)
10.934(1)
17.647(4)
75.886(5)
78.646(4)
84.125(3)
1656.3(4)
2
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
Z
Temperature, K
Absorption coefficient, μMo, mm–1
Total number of reflections
Number of independent reflections
Number of variables
Rint
198(2)
198(2)
150(2)
0.287
0.251
0.422
64046
47456
21045
10097
07915
06319
00639
00360
00488
0.0637
0.0331
0.0648
R1 [I > 2σ(I)]
0.0495
0.0336
0.0389
wR(F2) [I > 2σ(I)]
R1 (all reflections)
wR(F2) (all reflections)
Goodness of fit
0.1239
0.0846
0.0659
0.1188
0.0427
0.0773
0.1486
0.0915
0.0735
0.9780
0.9180
0.8560
2600 br (NH); 1650 (C=O); 1510, 1250 (NO2); 740
(C–Cl). Found, %: C 49.17; H 4.07; N 12.38.
C32H31Cl4N7O8. Calculated, %: C 49.04; H 3.96;
N 12.52.
density maps. All calculations were performed using
WinGX [8] and APEX2 [9]. The molecular and crystal
structures were plotted using Mercury 3.1 [10]. The
crystallographic parameters of compounds IV, V, and
VII and parameters of X-ray diffraction experiments
are collected in table. The CIF files containing com-
plete information on the examined structures were
deposited to the Cambridge Crystallographic Data
Centre (entry nos. CCDC 995031–995033) and are
available at www.ccdc.cam.ac.uk/data_request/cif.
The X-ray diffraction data for compounds IV, V,
and VII were acquired on a Bruker AXS Kappa Apex
II CCD diffractometer [λ(MoKα) = 0.71073 Å, graphite
monochromator]. A correction for absorption was
applied semiempirically using SADABS [6]. The
structures were solved by the direct method using
SHELXS97 [7]. The positions and temperature factors
of non-hydrogen atoms were refined in anisotropic
approximation using SHELX-97 [7]. Hydrogen atoms
attached to carbons were placed into geometrically cal-
culated positions which were refined according to the
riding model. Hydrogen atoms involved in hydrogen
bonds were localized from the difference electron
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