Synthesis and Neurotropic Activity of 4-Phenylpyridine-3-Carboxylic Acid and 3-Hydroxy-4-Phenylthieno[2,3-b]-Pyridine Derivatives

Article abstract of DOI:10.1007/s11094-019-1911-0

Aseries of pyridine-3-carboxylic acid derivatives were synthesized via recyclization of a thiopyran ring using cyclic secondary amines and then converted into substituted thieno[2,3-b]pyridines. Studies of the neurotropic properties identified several syn

Full text of DOI:10.1007/s11094-019-1911-0

DOI 10.1007/s11094-019-1911-0
Pharmaceutical Chemistry Journal, Vol. 52, No. 10, January, 2019 (Russian Original Vol. 52, No. 10, October, 2018)
SYNTHESIS AND NEUROTROPIC ACTIVITY
OF 4-PHENYLPYRIDINE-3-CARBOXYLIC ACID
AND 3-HYDROXY-4-PHENYLTHIENO[2,3-b ]-
PYRIDINE DERIVATIVES
E. G. Paronikyan,1 A. V. Ogannisyan,1,* R. G. Paronikyan,1
I. A. Dzhagatspanyan,1 I. M. Nazaryan,1 A. G. Akopyan,1 and N. S. Minasyan2
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 52, No. 10, pp. 22 – 27, October, 2018.
Original article submitted April 4, 2017.
A series of pyridine-3-carboxylic acid derivatives were synthesized via recyclization of a thiopyran ring using
cyclic secondary amines and then converted into substituted thieno[2,3-b]pyridines. Studies of the neurotropic
properties identified several synthesized compounds with anticonvulsant activity against corazole-induced
seizures. The compounds were active as psychological sedatives and, in contrast with the tranquilizer diaze-
pam, were inactive as central myorelaxants at anticonvulsant doses.
Keywords: pyridine-3-carboxylic acid derivatives, thieno[2,3-b]pyridines, neurotropic activity.
Modeling of a pathology itself in animals and of its sepa-
rate manifestations is an important and critical factor in the
search for new neurotropic compounds for experimental
psychopharmacology. Such an approach of differentiated
(use of interoceptive irritants, e.g., corazole) and integrated
(e.g., open field test) modeling, a biostatistical evaluation of
the spectra of pharmacological activity of the compounds,
and a comparison of main and side effects allow a more re-
fined selection from newly synthesized compounds.
Thieno[2,3-b]pyridines (IVa-l) were synthesized from
ethyl 6-amino-4-phenyl-2-thioxo-2H-thiopyran-5-carboxyla-
te [9], reaction of which with morpholine, piperidine, and
pyrrolidine occurred with recyclization of the thiopyran ring
and rearrangement to produce ethyl 4-phenyl-2-thioxo-1,2-
dihydropyridine-3-carboxylates (IIa-c). It was proposed that
the reaction with the amines involved nucleophilic attack at
thiopyran C-2, cleavage of the C(2)–S bond, and formation
of a pyridine ring.
Pyridine and its condensed analogs appear in the struc-
tures of many drugs [1]. Thieno[2,3-b]pyridines also include
compounds with high biological activity [2 – 5].
Thione–thiol tautomerism is known to occur in
2-thioxopyridines [10]. IR spectra showed that IIa-c in the
crystalline form existed as the thione because SH absorption
bands were missing in the spectra and absorption bands char-
acteristic of C=S and NH appeared at 1200 – 1200 and
3530 cm–1. However, the equilibrium shifted toward the thiol
form upon reaction with alkyl halides in basic solution. Ethyl
4-phenyl-2-thioxo-1,2-dihydropyridine-3-carboxylates IIa-c
were alkylated by various alkyl halides with electron-accept-
Condensed thieno[2,3-b]pyridines with neurotropic ac-
tivity were previously prepared by us [6 – 8]. In continuation
of this research, ethyl esters of 4-phenyl-2-thioxo-1,2-dihyd-
ropyridine-3-carboxylic acid were synthesized and cyclized
into thieno[2,3-b]pyridines that were studied for neurotropic
activity in the present work.
1
A. L. Mnjoyan Institute of Fine Organic Chemistry, Scientific and Tech-
ing groups in the a-position. Next, S-substituted pyridine de-
rivatives IIIa-l were cyclized by refluxing for 2 h in EtOH in
the presence of K CO . IR spectra of IVa-l contained absorp-
nological Center of Organic and Pharmaceutical Chemistry, National
Academy of Sciences of Armenia, 0014 Yerevan, 375014 Armenia.
2
Molecular Structure Research Center, Scientific and Technological Center
2
3
of Organic and Pharmaceutical Chemistry, National Academy of Sciences
of Armenia, 0014 Yerevan, 375014 Armenia.
tion bands for OH at 3180 – 3230 cm–1. PMR spectra had
*
e-mail: Haykuhihovhannisyan011@gmail.com
OH singlets at 10.40 – 14.00 ppm.
839
0091-150X/19/5210-0839 © 2019 Springer Science+Business Media, LLC

840
E. G. Paronikyan et al.
C6H5
COOEt
C6H5
COOEt
C6H5
COOEt
C6H5
COOEt
R-H
S-
H
S
S
NH2
R
R
N
N
H
S
R
N
SH
HS
H
IIa – c
I
C6H5
C6H5
OH
R1
COOEt
K2CO3
R
N
SCH2R1
R
N
S
IIIa – l
IVa – l
II) a: R = morpholin-4-yl; b: R = piperidin-1-yl; c: R = pyrrolidin-1-yl. III, IV) a-g: R = morpholin-4-yl; III, IV) h, i: R = piperidin-1-yl; III,
IV) j-l: R = pyrrolidin-1-yl; III, IV) a, k: R1 = COOMe; b, h, j: R1 = COOEt; c, l: R1 = CONH2; d: R1 = morpholin-4-ylcarbonyl; e:
R1 = pyrrolidin-1-ylcarbonyl; f: R1 = N-1,3-thiazol-2-ylcarboxamide; g: R1 = (2-methoxyphenyl)aminocarbonyl; i: R1 = COC6H5.
EXPERIMENTAL CHEMICAL PART
134 – 135°C.
R
0.59. C H N O S. PMR spectrum
18 20 2 2
f
(DMSO-d ), d, ppm: 1.00 (t, 3 H, J 7.1 Hz, CH CH ),
6
2
3
IR spectra were recorded in mineral oil on a Nicolet Ava-
tar 330 FT-IR spectrometer (USA). PMR and 13C NMR spec-
2.01 – 2.07 (m, 4H, 6-(CH ) ), 3.50 – 3.56 (m, 4H,
2 2
N(CH ) ), 3.95 (q, 2H, J 7.1 Hz, CH CH ), 5.71 (s, 1H,
2 2
2
3
tra (d, ppm, SSCC J, Hz) were recorded in DMSO-d on a
5-CH), 7.29 – 7.42 (m, 5H, C H ), 11.29 (br.s, 1H, NH).
6
6
5
Mercury 300 Vx instrument (USA) at 300 and 75.462 MHz,
respectively. The purity of compounds was monitored by
TLC on Silufol UV-254 plates using Me CO–Et O (1:2,
General method for preparing IIIa-l. A solution of
Na CO prepared from Na CO (0.25 g, 2.3 mmol) and H O
2
3
2
3
2
(8 mL) was treated with IIa-c (2.3 mmol). The mixture was
stirred until transparent, treated with the appropriate alkyl
halide (2.3 mmol) in EtOH (8 mL), and stirred at 20 – 22°C
for 6 h. The resulting crystals were filtered off, rinsed with
H O, and recrystallized from EtOH. IR spectra, n , cm–1:
2
2
IIa-c); Et O–hexane (3:1, IIIa-l); and CHCl –hexane (3:1,
2
3
IVa-l) and detection by I vapor. Elemental analyses agreed
2
with the empirical formulas.
General method for preparing IIa-c. A mixture of I
(2.9 g, 10 mmol), the appropriate amine (5 mL), and anhy-
drous EtOH (15 mL) was refluxed for 4 h, cooled, treated
2
max
1650 – 1680 and 1690 – 1725 (C=O), 3350 and 3410 (NH)
(IIIf, g), 3144 – 3150 and 3425 – 3430 (NH ) (IIIc, l).
2
with H O (50 mL), and neutralized with HCl (10%). The re-
2
Ethyl 2-[(2-methoxy-2-oxoethyl)thio]-6-morpholin-4-
sulting crystals were filtered off, rinsed with H O, and
2
yl-4-phenylnicotinate (IIIa). Yield 0.93 g (97%), mp
recrystallized from EtOH. IR spectra, n , cm–1: 1200 –
max
163 – 164°C.
R
0.66. C H N O S. PMR spectrum
21 24 2 5
f
1220 (C=S), 1680 – 1695 (CO), 3530 (NH).
(DMSO-d ), d, ppm: 0.85 (t, 3 H, J 7.6 Hz, CH CH ),
6
2
3
Ethyl 6-morpholin-4-yl-4-phenyl-2-thioxo-1,2-dihyd-
ropyridine-3-carboxylate (IIa). Yield 2.5 g (73%), mp
3.58 – 3.69 (m, 11H, N(CH ) O, OCH ), 3.79 (s, 2H, SCH ),
2 4
3
2
3.89 (q, 2H, J 7.6, CH CH ), 6.31 (s, 1H, 5-CH), 7.20 – 7.27
2
3
109 – 110°C.
R
0.59. C H N O S. PMR spectrum
18 20 2 3
f
(m, 2H, C H ), 7.29 – 7.36 (m, 3H, C H ). 13C NMR spec-
6
5
6
5
(DMSO-d ), d, ppm: 1.02 (t, 3H, J 7.1 Hz, CH CH );
6
2
3
trum, d , ppm: 12.9, 32.1, 44.4, 51.4, 59.5, 65.7, 102.6,
3.41 – 3.57 (m, 4H, N(CH ) ); 3.62 – 3.79 (m, 4H,
C
2 2
113.2, 127.1, 127.2, 127.5, 140.2, 151.7, 156.8, 157.1, 165.7,
169.0.
O(CH ) ); 3.97 (q, 2H, J 7.1 Hz, CH CH ); 6.03 (s, 1H,
2 2
2
3
5-CH); 7.24 – 7.41 (m, 5H, C H ); 12.31 (br.s, 1H, NH). 13
C
6
5
Ethyl 2-[(2-ethoxy-2-oxoethyl)thio]-6-morpholin-4-
yl-4-phenylnicotinate (IIIb). Yield 0.95 g (96%), mp
NMR spectrum, d , ppm: 13.1, 46.3, 59.6, 65.5, 98.2, 103.6,
C
127.0, 127.6, 127.8, 140.2, 151.8, 153.1, 158.2, 166.5.
Ethyl 4-phenyl-6-piperidin-1-yl-2-thioxo-1,2-dihydro-
pyridine-3-carboxylate (IIb). Yield 23.5 g (69%), mp
133 – 134°C.
R
0.67. C H N O S. PMR spectrum
22 26 2 5
f
(DMSO-d ), d, ppm: 0.83 (t, 3H, J 7.1 Hz, CH CH ), 1.26 (t,
6
2
3
3H, J 7.1 Hz, CH CH ), 3.54 – 3.62 (m, 4H, N(CH ) ),
141 – 142°C.
R
0.58. C H N O S. PMR spectrum
19 22 2 2
2
3
2 2
f
3.67 – 3.73 (m, 4H, O(CH ) ), 3.78 (s, 2H, SCH ), 3.90 (q,
(DMSO-d ), d, ppm: 0.96 (t, 3H, J 7.1 Hz, CH CH ),
2 2
2
6
2
3
2H, J 7.1 Hz, CH CH ), 4.11 (q, 2 H, J 7.1 Hz, CH CH ),
1.63 – 1.71 (m, 6H, 6-(CH ) ), 3.46 – 3.55 (m, 4H,
2
3
2
3
2 3
6.32 (s, 1H, 5-CH), 7.22 – 7.28 (m, 2H, C H ), 7.31 – 7.40
N(CH ) ), 3.79 (q, 2H, J 7.1 Hz, CH CH ), 5.97 (s, 1H,
6
5
2 2
2
3
5-CH), 7.30 – 7.39 (m, 5H, C H ), 12.19 (br.s, 1H, NH). 13
C
(m, 3H, C H ).
6 5
6
5
Ethyl
yl-4-phenylnicotinate (IIIc). Yield 0.80 g (87%), mp
172 – 173°C. 0.62. C H N O S. PMR spectrum
(DMSO-d ), d, ppm: 0.84 (t, 3 H, J 7.1 Hz, CH CH ),
2-[(2-amino-2-oxoethyl)thio]-6-morpholin-4-
NMR spectrum, d , ppm: 13.1, 23.5, 24.7, 45.2, 59.5, 103.1,
C
111.5, 127.0, 127.2, 127.4, 140.6, 152.0, 156.3, 157.1, 166.0.
Ethyl 4-phenyl-6-pyrrolidin-1-yl-2-thioxo-1,2-dihyd-
ropyridine-3-carboxylate (IIc). Yield 2.20 g (67%), mp
R
f
20 23
3
4
6
2
3

Synthesis and Neurotropic Activity
841
3.59 – 3.65 (m, 6H, N(CH ) , SCH ), 3.69 – 3.78 (m, 4H,
N(CH ) ), 3.89 (q, 2H, J 7.1 Hz, CH CH ), 4.58 (s, 2H,
2 2
2
2 2
2
3
O(CH ) ), 3.91 (q, 2H, J 7.1 Hz, CH CH ), 6.31 (s, 1H,
SCH ), 6.22 (s, 1H, 5-CH), 7.22 – 7.26 (m, 2H, C H ),
2 2
2
3
2
6
5
5-CH), 6.85 and 6.94 (br.s, 1H and 1H, NH ), 7.21 – 7.26 (m,
7.31 – 7.37 (m, 3H, C H ), 7.46 – 7.62 (m, 3H, C H ),
2
6
5
6
5
2H, C H ), 7.28 – 7.38 (m, 3H, C H ).
8.03 – 8.07 (m, 2H, C H ).
6
5
6
5
6
5
Ethyl 6-morpholin-4-yl-2-[(2-morpholin-4-yl-2-oxo-
ethyl)thio]-4-phenylnicotinate (IIId). Yield 1.05 g (95%),
mp 158 – 160°C. R 0.67. C H N O S. PMR spectrum
Ethyl 2-[(2-ethoxy-2-oxoethyl)thio]-6-pyrrolidin-1-
yl-4-phenylnicotinate (IIIj). Yield 0.75 g (78%), mp
159 – 160°C. 0.67. C H N O S. PMR spectrum
(DMSO-d ), d, ppm: 0.82 (t, 3H, J 7.1 Hz, CH CH ), 1.27 (t,
R
f
24 29
3
5
f
22 26
2
4
(DMSO-d ), d, ppm: 0.84 (t, 3H, J 7.2 Hz, CH CH ),
6
2
3
6
2
3
3.49 – 3.73 (m, 16H, 2[N(CH ) O]), 3.86 (q, 2H, J 7.2 Hz,
3H, J 7.1 Hz, CH CH ), 2.00 – 2.06 (m, 4H, 6-(CH ) ),
2 4
2
3
2 2
CH CH ), 3.99 (c, 2H, SCH ), 6.33 (s, 1H, 5-CH),
3.47 – 3.54 (m, 4H, N(CH ) ), 3.82 (s, 2H, SCH ), 3.87 (q,
2
3
2
2 2
2
7.23 – 7.28 (m, 2H, C H ), 7.30 – 7.39 (m, 3H, C H ).
2H, J 7.1 Hz, OCH CH ), 4.15 (q, 2H J 7.1 Hz, OCH CH ),
6
5
6
5
2
3
2
3
Ethyl 6-morpholin-4-yl-2-[(2-oxo-2-pyrrolidin-1-yl-
ethyl)thio]-4-phenylnicotinate (IIIe). Yield 0.87 g (79%),
mp 177 – 180°C. R 0.63. C H N O S. PMR spectrum
5.97 (s, 1H, 5-CH), 7.21 – 7.26 (m, 2H, C H ), 7.31 – 7.38
6
5
(m, 3H, C H ). 13C NMR spectrum, d , ppm: 12.9, 13.7,
6
5
C
f
24 29
3
4
24.8, 32.3, 46.1, 59.2, 60.0, 102.5, 111.3, 126.9, 127.0,
127.4, 140.6, 151.3, 155.1, 157.3, 166.0, 168.6.
(DMSO-d ), d, ppm: 0.85 (t, 3H, J 7.1 Hz, CH CH ),
6
2
3
1.82 – 1.92 (m, 2H, NCH CH ), 1.95 – 2.04 (m, 2H,
Ethyl 2-[(2-methoxy-2-oxoethyl)thio]-6-pyrrolidin-1-
yl-4-phenylnicotinate (IIIk). Yield 0.67 g (72%), mp
2
2
NCH CH ), 3.37 (t, 2H, J 6.8 Hz, NCH CH ), 3.36 (t, 2H, J
2
2
2
2
6.8 Hz, NCH CH ), 3.58 – 3.63 (m, 4H, 6-N(CH ) ),
2
2
2 2
176 – 177°C.
R
0.65. C H N O S. PMR spectrum
21 24 2 4
f
3.68 – 3.73 (m, 4H, 6-O(CH ) ), 3.89 (c, 2H, SCH ), 3.91 (q,
2 2
2
(DMSO-d ), d, ppm: 0.81 (t, 3H, J 7.1 Hz, CH CH ),
6
2
3
2 H, J 7.1 Hz, CH CH ), 6.32 (c, 1H, 5-CH), 7.24 – 7.29 (m,
2
3
1.97 – 2.09 (m, 4H, 6-(CH ) ), 3.44 – 3.55 (m, 4H,
2 2
2H, C H ), 7.33 – 7.40 (m, 3H, C H ).
6
5
6
5
N(CH ) ), 3.68 (s, 3H, OCH ), 3.83 (s, 2H, SCH ), 3.87 (q,
2 2
3
2
Ethyl 6-morpholin-4-yl-2-{[2-oxo-2-(1,3-thiazol-2-yl)-
ethyl]thio}-4-phenylnicotinate (IIIf). Yield 0.85 g (77%),
mp 159 – 160°C. R 0.68. C H N O S . PMR spectrum
2H, J 7.1 Hz, CH CH ), 5.96 (s, 1H, 5-CH), 7.20 – 7.26 (m,
2
3
2H, C H ), 7.29 – 7.38 (m, 3H, C H ).
6
5
6
5
f
23 24
4
4 2
Ethyl
yl-4-phenylnicotinate (IIIl). Yield 0.66 g (73%), mp
181 – 182°C. 0.69. C H N O S. PMR spectrum
(DMSO-d ), d, ppm: 0.82 (t, 3H, J 7.1 Hz, CH CH ),
2-[(2-amino-2-oxoethyl)thio]-6-pyrrolidin-1-
(DMSO-d ), d, ppm: 0.84 (t, 3 H, J 7.1 Hz, CH CH ),
6
2
3
3.51 – 3.58 (m, 8H, N(CH ) O), 3.91 (q, 2H, J 7.1 Hz,
2 4
R
f
20 23
3
3
CH CH ), 3.98 (s, 2H, SCH ), 6.29 (s, 1H, 5-CH), 6.97 (d,
2
3
2
6
2
3
1H, J 3.6 Hz, SCHCHN), 7.22 – 7.28 (m, 2H, C H ),
6
5
2.01 – 2.06 (m, 4H, 6-(CH ) ), 3.51 – 3.57 (m, 4H,
2 2
7.32 – 7.37 (m, 3H, C H ), 7.39 (d, 1H, J 3.6 Hz, SCHCHN),
6
5
N(CH ) ), 3.66 (s, 2H, SCH ), 3.87 (q, 2H, J 7.1 Hz,
12.08 (s, 1H, NH). 13C NMR spectrum, d , ppm: 13.0, 33.8,
2 2
2
C
CH CH ), 5.98 (s, 1H, 5-CH), 6.80 and 6.90 (br.s, 1H and
2
3
44.4, 59.5, 65.6, 102.6, 112.3, 113.4, 127.1, 127.2, 127.5,
136.9, 140.2, 151.4, 156.8, 157.2, 157.9, 165.9, 166.3.
Ethyl 2-({2-[(2-methoxyphenyl)amino]-2-oxoethyl}-
thio)-6-morpholin-4-yl-4-phenylnicotinate (IIIg). Yield
0.94 g (78%), mp 187 – 189°C. R 0.65. C H N O S. PMR
1H, NH ), 7.22 – 7.26 (m, 2H, C H ), 7.31 – 7.39 (m, 3H,
2
6
5
C H ). 13C NMR spectrum, d , ppm: 13.0, 24.8, 33.5, 46.2,
6
5
C
59.3, 102.5, 111.8, 127.0, 127.1, 127.4, 140.5, 151.1, 155.2,
157.0, 166.1, 170.0.
f
27 29
3
5
General method for preparing IVa-l. A mixture of
IIIa-l (2 mmol), K CO (0.28 g, 2 mmol), and anhydrous
spectrum (DMSO-d ), d, ppm: 0.87 (t, 3 H, J 7.1 Hz,
6
2
3
CH CH ), 3.56 – 3.64 (m, 8H, N(CH ) O), 3.77 (s, 3H,
2
3
2 4
EtOH (5 mL) was refluxed for 2 h. The resulting crystals
were filtered off, placed into a beaker, and treated with conc.
HCl (2 mL) until white crystals formed. These crystals were
OCH ), 3.86 (s, 2H, SCH ), 3.94 (q, 2H, J 7.1, CH CH ), 6.37
3
2
2
3
(s, 1H, 5-CH), 6.83 – 6.90 (m, 2H, C H ), 6.93 – 6.98 (m, 1H,
6
4
C H ), 7.24 – 7.30 (m, 2H, C H ), 7.34 – 7.40 (m, 3H, C H ),
6
4
6
5
6
5
filtered off, rinsed with H O until neutral, and recrystallized
cm–1:
2
8.20 (dd, 1H, J 8.6 Hz, 2.0 C H ), 9.08 (s, 1H, NH).
6
4
from CHCl –EtOH (1:1). IR spectra,
n
,
Ethyl 2-[(2-ethoxy-2-oxoethyl)thio]-6-piperidin-1-yl-
4-phenylnicotinate (IIIh). Yield 0.77 g (78%), mp
129 – 130°C. 0.63. C H N O S. PMR spectrum
(DMSO-d ), d, ppm: 0.82 (t, 3H, J 7.1 Hz, CH CH ), 1.27 (t,
3
max
1655 – 1716 (CO), 3180 – 3230 (OH), 3320 and 3380 (NH)
(IVf, g), 3330 and 3380 (NH ) (IVc, l).
R
2
f
23 28
2
4
Methyl 3-hydroxy-6-morpholin-4-yl-4-phenylthieno-
6
2
3
[2,3-b]pyridine-2-carboxylate (IVa). Yield 0.7 g (92%), mp
3H, J 7.1 Hz, CH CH ), 1.58 – 1.74 (m, 6H, 6-(CH ) ),
2
3
2 3
214 – 215°C.
R
0.67. C H N O S. PMR spectrum
19 18 2 4
3.60 – 3.66 (m, 4H, N(CH ) ), 3.79 (s, 2H, SCH ), 3.89 (q,
f
2 2
2
(DMSO-d ), d, ppm: 3.68 – 3.80 (m, 8H, N(CH ) O), 3.88
2H, J 7.1 Hz, OCH CH ), 4.13 (q, 2H, J 7.1 Hz, OCH CH ),
6
2 4
2
3
2
3
(s, 3H, OCH ), 6.63 (s, 1H, 5-CH), 7.38 – 7.46 (m, 5H,
6.25 (s, 1H, 5-CH), 7.21 – 7.26 (m, 2H, C H ), 7.31 – 7.38
3
6
5
C H ), 10.40 (s, 1H, OH). 13C NMR spectrum, d , ppm:
(m, 3H, C H ).
6
5
6
5
C
Ethyl 2-[(2-oxo-2-phenylethyl)thio]-6-piperidin-1-yl-
4-phenylnicotinate (IIIi). Yield 0.87 g (79%), mp
169 – 170°C. 0.68. C H N O S. PMR spectrum
(DMSO-d ), d, ppm: 0.82 (t, 3H, J 7.1 Hz, CH CH ),
44.7, 51.1, 65.8, 104.4, 106.1, 112.2, 127.0, 127.6, 128.7,
137.2, 148.2, 158.2, 158.7, 161.1, 166.7.
R
Ethyl 3-hydroxy-6-morpholin-4-yl-4-phenylthieno-
[2,3-b]pyridine-2-carboxylate (IVb). Yield 0.74 g (99%),
mp 160 – 161°C. R 0.62. C H N O S. PMR spectrum
f
27 28
2
3
6
2
3
1.33 – 1.59 (m, 6H, 6-(CH ) ), 3.39 – 3.45 (m, 4 H,
2 3
f
20 20
2
4

842
E. G. Paronikyan et al.
N(CH ) ), 4.34 (q, 2 H, J 7.1 Hz, CH CH ), 6.29 (s, 1H,
(DMSO-d ), d, ppm: 1.39 (t, 3H, J 7.1 Hz, CH CH ),
2 2
2
3
6
2
3
5-CH), 7.36 – 7.48 (m, 5H, C H ), 10.50 (s, 1H, OH).
3.65 – 3.76 (m, 8H, N(CH ) O), 4.34 (q, 2H, J 7.1 Hz,
6
5
2 4
Methyl 3-hydroxy-4-phenyl-6-pyrrolidin-1-ylthieno-
[2,3-b]pyridine-2-carboxylate (IVk). Yield 0.73 g (91%),
mp 220 – 221°C. R 0.63. C H N O S. PMR spectrum
CH CH ), 6.55 (s, 1H, 5-CH), 7.33 – 7.45 (m, 5H, C H ),
2
3
6
5
10.48 (s, 1H, OH).
3-Hydroxy-6-morpholin-4-yl-4-phenylthieno[2,3-b]py-
ridine-2-carboxamide (IVc). Yield 0.66 g (88%), mp
249 – 250°C. 0.65. C H N O S. PMR spectrum
(DMSO-d ), d, ppm: 3.62 – 3.78 (m, 8H, N(CH ) O), 6.61 (s,
f
19 18
2
3
(DMSO-d ), d, ppm: 2.01 – 2.11 (m, 4H, 6-(CH ) ),
6
2 2
3.54 – 3.63 (m, 4H, N(CH ) ), 3.87 (s, 3H, OCH ), 6.29 (s,
R
2 2
3
f
18 17 3 3
1H, 5-CH), 7.35 – 7.47 (m, 5H, C H ), 10.43 (s, 1H, OH).
6
5
6
2 2
3-Hydroxy-4-phenyl-6-pyrrolidin-1-ylthieno[2,3-b]py-
ridine-2-carboxamide (IVl). Yield 0.36 g (79%), mp
251 – 252°C. 0.65. C H N O S. PMR spectrum
(DMSO-d ), d, ppm: 2.01 – 2.11 (m, 4H, 6-(CH ) ),
1H, 5-CH), 7.32 – 7.49 (m, 7H, C H , NH ), 13.08 (s, 1H, OH).
6
5
2
3-Hydroxy-6-morpholin-4-yl-2-(morpholin-4-ylcarbo-
nyl)-4-phenylthieno[2,3-b]pyridine (IVd). Yield 0.51 g
(60%), mp 196 – 197°C. R 0.62. C H N O S. PMR spec-
R
f
18 17
3
2
6
2 2
f
22 23
3
4
3.54 – 3.61 (m, 4H, N(CH ) ), 6.26 (s, 1H, CH), 7.20 (br.s,
trum (DMSO-d ), d, ppm: 3.66 – 3.81 (m, 16H,
2 2
6
2H, NH ), 7.35 – 7.49 (m, 5H, C H ), 13.08 (br.s, 1H, OH).
2[N(CH ) O]), 6.62 (s, 1H, 5-CH), 7.37 – 7.47 (m, 5H,
2
6
5
2 4
13C NMR spectrum, d , ppm: 24.8, 46.4, 94.6, 106.1, 111.6,
C H ), 13.36 (s, 1H, OH).
C
6
5
126.8, 127.3, 128.7, 147.3, 156.0, 158.3, 159.3, 160.2, 169.1.
3-Hydroxy-6-morpholin-4-yl-4-phenyl-2-(pyrrolidin-
1-ylcarbonyl)thieno[2,3-b]pyridine (IVe). Yield 0.82 g
(99%), mp 162 – 163°C. R 0.64. C H N O S. PMR spec-
EXPERIMENTAL BIOLOGICAL PART
f
22 23
3
3
trum (DMSO-d ), d, ppm: 2.01 (s, 4H, N(CH CH ) ),
6
2
2 2
Biological experiments were conducted in full compli-
ance with the European Convention for the Protection of Ver-
tebrate Animals Used for Experimental and Other Scientific
Purposes (European Treaty Series No. 123, Strasbourg, Mar.
18, 1986).
3.66 – 3.74 (m, 12H, N(CH CH ) , N(CH ) O), 6.62 (s, 1H,
2
2 2
2 4
5-CH), 7.37 – 7.48 (m, 5H, C H ), 13.95 (s, 1H, OH).
6
5
3-Hydroxy-6-morpholin-4-yl-4-phenyl-N-1,3-thiazol-
2-ylthieno[2,3-b]pyridine-2-carboxamide (IVf). Yield
0.6 g (68%). mp 253 – 254°C. R 0.64. C H N O S . PMR
f
21 18
4
3 2
Neurotropic activity of the synthesized compounds was
studied with respect to anticonvulsant activity with corazole
antagonism, exploratory activity in the open field test, and
central myorelaxant activity. The synthesized compounds
and reference drug diazepam were studied in 300 laboratory
white mice of both sexes (18 – 24 g) and 48 male Wistar rats
(120 – 140 g).
spectrum (DMSO-d ), d, ppm: 3.62 – 3.80 (m, 8H,
6
N(CH ) O), 6.58 (s, 1H, 5-CH), 6.81 (d, 1H, J 4.6 Hz,
2 4
SCHCHN), 7.23 (d, 1H, J 4.6 Hz, SCHCHN), 7.38 – 7.50
(m, 5H, C H ), 12.78 (br, 2H, NH, OH).
6
5
3-Hydroxy-N-(2-methoxyphenyl)-6-morpholin-4-yl-4-
phenylthieno[2,3-b]pyridine-2-carboxamide (IVg). Yield
0.55 g (60%), mp 171 – 172°C. R 0.68. C H N O S. PMR
f
25 23
3
4
Anticonvulsant activity was assessed from the preven-
tion of the clonic seizure component induced in mice by s.c.
injection of corazole (90 mg/kg) [11, 12]. Corazole antago-
nism was also a predictive test for tranquilizing activity of
the compounds. Adverse side effects in these same animals,
i.e., a central myorelaxant effect and uncoordinated move-
ments, were studied using the rotating rod method [13]. The
spectrum (DMSO-d ), d, ppm: 3.68 – 3.74 (m, 8H,
6
N(CH ) O), 3.93 (s, 3H, OCH ), 6.64 (s, 1H, 5-CH),
2 4
3
6.89 – 7.08 (m, 3H, C H ), 7.39 – 7.51 (m, 5H, C H ), 8.07 (dd,
6
4
6 5
1H, J 8.6 Hz, 2.0, C H ), 8.52 (s, 1H, NH), 11.81 (s, 1H, OH).
6
4
Ethyl
[2,3-b]pyridine-2-carboxylate (IVh). Yield 0.6 g (77%),
mp 189 – 190°C. R 0.64. C H N O S. PMR spectrum
3-hydroxy-4-phenyl-6-piperidin-1-ylthieno-
f
21 22
2
3
(DMSO-d ), d, ppm: 1.40 (t, 3H, J 7.1 Hz, CH CH ),
6
2
3
1.61 – 1.76 (m, 6H, 6-(CH ) ), 3.69 – 3.77 (m, 4H,
2 3
N(CH ) ), 4.34 (q, 2H, J 7.1 Hz, CH CH ), 6.56 (s, 1H,
TABLE 1. Comparative Anti-Corazole Activity of IIIa, d-f, and
Diazepam*
2 2
2
3
5-CH), 7.36 – 7.47 (m, 5H, C H ), 10.48 (s, 1H, OH).
6
5
Corazole antagonism, **
(3-Hydroxy-4-phenyl-6-piperidin-1-ylthieno[2,3-b]py-
ridin-2-yl)(phenyl)methanone (IVi). Yield 0.75 g (90%),
mp 169 – 170°C. R 0.7. C H N O S. PMR spectrum
Compound n = 8
(ED50, mg/kg)
f
25 22
2
2
IIIa
36.0 (30.0 ¸ 43.2)
41.0 (31.5 ¸ 53.3)
30.0 (24.0 ¸ 37.5)
42.0 (22.5 ¸ 74.6)
0.51(0.39 ¸ 0.69)
(DMSO-d ), d, ppm: 1.61 – 1.80 (m, 6H, 6-(CH ) ),
6
2 3
IIId
3.72 – 3.84 (m, 4H, N(CH ) ), 6.61 (s, 1H, 5-CH),
2 2
IIIc
7.39 – 7.60 (m, 3H, C H and 5H, 4-C H ), 7.91 – 7.97 (m,
6
5
6
5
IIIf
2H, C H ), 13.98 (br.s, 1H, OH).
6
5
Ethyl
[2,3-b]pyridine-2-carboxylate (IVj). Yield 0.73 g (84%),
mp 173 – 174°C. R 0.62. C H N O S. PMR spectrum
3-hydroxy-4-phenyl-6-pyrrolidin-1-ylthieno-
Diazepam
*
Diazepam (Polfa, Poland) was used as a solution for injection
f
20 20
2
3
(1 mL = 5 mg);
**
Confidence intervals at probability level p = 0.05.
(DMSO-d ), d, ppm: 1.39 (t, 3H, J 7.1 Hz, CH CH ),
6
2
3
2.03 – 2.09 (m, 4H, 6-(CH ) ), 3.55 – 3.62 (m, 4H,
2 2

Synthesis and Neurotropic Activity
843
laxation. Differences from the control and diazepam were
statistically significant because P.R. > fP.R. [14].
TABLE 2. Exploratory Activity of IIIa, d-f, and Diazepam in the
Open Field Model
The most effective compounds (IIIa, d-f) were studied
in the open field tests. The number of horizontal movements
was 23.8; vertical, 5.6; explored cells, 1.8 in the open field
test for rats in the control group for diazepam and IIIa, d-f
(Table 2).
Number of, absolute values for 5 min*
Compound
Horizontal
movements
Vertical
Explored
cells
(n = 8)
movements
Control, emulsifier
23.8 ± 3.2
14.4 ± 3.5**
12.8 ± 2.1**
13.6 ± 3.4**
16.2 ± 2.9**
33.6 ± 4.2**
5.6 ± 1.2
1.8 ± 0.6
1.4 ± 0.6
The tested compounds caused statistically significant be-
havioral changes as compared to the control and diazepam.
Injection of all compounds inhibited horizontal and vertical
movements of the animals, i.e., a psychosedative effect was
observed. Two of the selected compounds (IIIe, f) increased
the number of explored cells, which could be related to slight
anxiolytic activity for them (Table 2). Diazepam (2 mg/kg)
caused a significant increase of all these parameters as com-
pared to the control, i.e., activating and anxiolytic activities
were present.
IIIa
3.2 ± 1.0**
2.6 ± 1.1**
2.6 ± 1.1**
2.7 ± 1.5**
8.3 ± 1.1**
IIId
3.2 ± 0.8**
1.0 ± 0.4**
3.8 ± 1.2**
5.0 ± 1.3**
IIIe
IIIf
Diazepam
*
p £ 0.05.
**
Differences statistically significant vs. the control and diazepam.
Structure–activity relationship studies showed that com-
pounds with a pyridine ring (IIIa, d-f) had the strongest
anticonvulsant activity. Formation of a thiophene ring weak-
ened the activity. However, the most active compounds con-
tained a 6-morpholine moiety on the pyridine ring.
compounds were administered at doses of 25 – 100 mg/kg;
reference drug diazepam, 0.1 – 2 mg/kg i.p. 45 min before
injection of corazole as a suspension with carboxyme-
thylcellulose and Tween-80. Control animals received emul-
sifier. Each dose of the compounds was studied in eight ani-
REFERENCES
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50
the tested drugs by the Litchfield and Wilcoxon method [14].
Sedative, activating, and anxiolytic activities of the se-
lected most active compounds were studied using rats in the
open field test and their locomotor and orienting-exploratory
activity [15]. Tests were conducted during the day with natu-
ral lighting. Spontaneous behavior of each separate animal
was recorded for 5 min. Sedative and activating activity were
evaluated from the number of horizontal (squares crossed)
and vertical movements (rearings on hind paws). Anxiolytic
effects were assessed from the number of cells explored by
test and control animals. The compounds, the control, and di-
azepam were tested using eight animals each. Tested com-
pounds were injected i.p. to rats at the most effective dose of
50 mg/kg; the reference drug, at a dose of 2 mg/kg. Control
animals were injected with emulsifier. Results were pro-
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Studies of anticonvulsant activity found that all synthe-
sized pyridine derivatives possessed anti-corazole activity.
Thus, IIa-c, IIIb, c, g-l, and IVa-l at a dose of 50 mg/kg pre-
vented seizures in 20 – 40% of the animals. Compounds
IIIa, d-f possessed pronounced anticonvulsant activity.
Corazole seizures were prevented by these compounds start-
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ing at a dose of 12.5 mg/kg injected into mice. The ED val-
50
ues were 30 – 42 mg/kg (Table 1). Locomotor coordination
was not disrupted and myorelaxation was not observed at
doses of 50 – 75 mg/kg in mice. The anticonvulsant activi-
ties of the compounds were inferior to that of diazepam.
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Press, New York (1992), pp. 433 – 458.
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50
in mice was 0.5 mg/kg (Table 1). However, diazepam al-
ready at a dose of 2 mg/kg in mice caused central myore-