Synthesis and biological activity of heterocyclic borneol derivatives

Article abstract of DOI:10.1007/s10593-017-2063-3

(figure presented) A series of novel heterocyclic derivatives of (–)-borneol has been prepared by the interaction of (1S,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]-heptan-2-yl 2-chloroacetate and (1S,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl 3-chloropropanoate with different N- and S-nucleophiles. The obtained products were screened for antiviral, antiulcer, and analgesic activity.

Full text of DOI:10.1007/s10593-017-2063-3

DOI 10.1007/s10593-017-2063-3
Chemistry of Heterocyclic Compounds 2017, 53(3), 371–377
Synthesis and biological activity
of heterocyclic borneol derivatives
Anastasiya S. Sokolova1,2*, Оlga I. Yarovaya1,2, Anna A. Shtro3,
Marina S. Borisova1, Ekaterina A. Morozova1, Tatyana G. Tolstikova1,
Vladimir V. Zarubaev3, Nariman F. Salakhutdinov1,2
1 N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry,
Siberian Branch of the Russian Academy of Sciences,
9 Lavrentiev Ave., Novosibirsk 630090, Russia; e-mail: asokolova@nioch.nsc.ru
2 Novosibirsk State University,
2 Pirogova St., Novosibirsk 630090, Russia; e-mail: ooo@nioch.nsc.ru
3 Department of Chemotherapy, Research Institute of Influenza,
15/17 Prof. Popova St., Saint Petersburg 197376, Russia
e-mail: zarubaev@influenza.spb.ru
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2017, 53(3), 371–377
Submitted December 15, 2016
Accepted after revision February 20, 2017
A series of novel heterocyclic derivatives of (–)-borneol has been prepared by the interaction of (1S,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]-
heptan-2-yl 2-chloroacetate and (1S,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl 3-chloropropanoate with different N- and S-nucleo-
philes. The obtained products were screened for antiviral, antiulcer, and analgesic activity.
Keywords: 1H-benzimidazole-2-thiol, benzoxazole-2-thiol, benzthiazole-2-thiol, (–)-borneol, analgesic activity, antiulcer activity,
antiviral activity.
Borneol (1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol) is a
bicyclic monoterpenoid alcohol, which is a valuable medi-
cinal substance used in the traditional medicine of China
and India. Recent studies have shown that (–)-borneol and
its derivatives possess various types of biological effects,
such as antimicrobial,1,2 anti-inflammatory,3 and antiviral
activity.4 Some studies have shown that (–)-borneol can
improve the nasal and gastrointestinal bioavailability of
drugs,5 transiently increase the permeability of the blood-
brain barrier, and enhance the distribution of drugs in brain
tissue.6,7
We previously demonstrated that the presence of 1,7,7-tri-
methylbicyclo[2.2.1]heptane scaffold was associated with
high inhibitory activity of molecules on the replication of
influenza A virus.8–10 Moreover, it was reported that
borneol derivatives containing the structural motif of
α-truxillic acid showed analgesic activity.11 On the other
hand, heterocyclic compounds and their derivatives have
attracted strong interest in the field of medicinal chemistry
due to their beneficial biological and pharmacological
properties. Among such compounds, derivatives of benz-
imidazole, benzoxazole, and benzothiazole have been
shown to exhibit a wide range of biological effects,
including antiulcer, antihypertensive, analgesic, anti-
inflammatory, and antiviral activity.12
Thus, we considered it worthwhile to construct new
heterocyclic (–)-borneol derivatives bearing benzothiazole,
benzoxazole, benzimidazole, and other heterocycles, and to
evaluate their biological properties, such as the inhibition
of influenza virus replication, antiulcer action, and anal-
gesic effect.
The synthetic strategies for obtaining the target com-
pounds are outlined in Scheme 1. The starting (–)-borneol
esters 1a,b were synthesized by reactions between
(–)-borneol and acyl chlorides derived from α- or
β-chlorinated carboxylic acids (Scheme 1).
The reaction of compound 1a with benzothiazole-2-thiol
(2) in acetone medium in the presence of K2CO3 yielded
derivative 5a. Benzoxazole-2-thiol (3) and 1H-benz-
imidazole-2-thiol (4) were subjected to alkylation with
(1S,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl
chloro-
acetate (1a) in the presence of aqueous KOH in 2-PrOH,
0009-3122/17/53(03)-0371©2017 Springer Science+Business Media New York
371

Chemistry of Heterocyclic Compounds 2017, 53(3), 371–377
Scheme 1
various thiols led to the formation of a previously unknown
series of heterocyclic derivatives 5b–c, 6b–c, 7b, and 9a–g
(Scheme 1).
Due to the ambident nature of anions derived from thiols
2–4 in nucleophilic substitution reactions, either N- or
S-substituted products can be obtained depending on the
reaction conditions and the predominant mechanism.
Previously, it has been shown that the ethylation of thiols 2–4
occurred at the nitrogen rather than the sulfur atom of
thiol.13 In all SN2-type alkylations, e.g., with alkyl halides
and dialkyl sulfates, S-alkylated products were obtained. In
the case of ester 1b, the reaction with benzthiazole-2-thiol
(2) and benzoxazole-2-thiol (3) under basic conditions gave
a mixture containing products 5b,c (1:1) and 6b,c (0.5:1).
The ratio of products 5b,c and 6b,c was established by
1H NMR spectroscopy. The interaction of (1S,2R,4S)-1,7,7-
trimethylbicyclo[2.2.1]heptan-2-yl 3-chloropropanoate (1b)
with 1H-benzimidazole-2-thiol (4) in the presence of DBU
furnished only one product 7b. The formation of
N-substituted products can be explained by elimination
process in ester 1b that led to the electron-deficient alkene
8 with double bond activated toward nucleophilic attack.
Thus, alkyl halide 1b reacted with the thiol group, while
alkene 8 was attacked by nitrogen nucleophile.
It is known that nitrogen-containing five- and six-
membered heterocyclic compounds have recently attracted
considerable attention due to their prominent role in the
field of drug discovery.14 In the view of this, the library of
borneol propanoate derivatives was expanded by intro-
ducing pyridine, pyrimidine, imidazole, and triazole rings
in the molecules of interest. The target compounds 9a–g
were obtained from the reactions of compound 1b with
different nucleophiles in the presence of DBU (Scheme 1).
The structures of the synthesized compounds were
deduced from 1H and 13C NMR spectra. It is noteworthy to
contrast the chemical shift observed for the methylene
protons at the C-13 atom in compounds 5b, 6b and 5c, 6c.
The SCH2 proton signals in 1H NMR spectra of compounds
5b, 6b appeared at 3.54–3.60 ppm, whereas the NCH2
1
signals in H NMR spectra of compounds 5c, 6c were
found at 4.44–4.69 ppm. The signals of compounds 5c, 6c
were shifted downfield due to the deshielding effect of the
thiocarbonyl group. In 13C NMR spectra of compounds 5b, 6b,
the C-14 atom signals appeared at 165.8 and 164.3 ppm,
respectively, whereas in their rearranged products 5c and
6c the С=S signals were found at 189.0 and 179.9 ppm,
respectively.
The prepared compounds were studied for their antiviral
activity against influenza virus A/Puerto Rico/8/34
(H1N1). The results of the investigation are presented in
Table 1. Rimantadine, amantadine, and deitiforin were used
as reference compounds due to a close similarity of their
rigid cage fragments to those in the tested compounds.
In general, the group of studied compounds has
demonstrated low-to-moderate viral inhibition activity.
Among the synthesized compounds, the bis-substituted
derivatives 7b having two (–)-borneol fragments attached
to 1H-benzimidazole-2-thiol core exhibited potent antiviral
properties. High antiviral activity was also observed in the
affording the required heterocyclic derivatives 6a and 7a.
The poor yield of compounds 5–7 a can be explained by
the fact that reactant 1a was unstable under these reaction
conditions. The reaction of (1S,2R,4S)-1,7,7-trimethyl-
bicyclo[2.2.1]heptan-2-yl 3-chloropropanoate (1b) with
372

Chemistry of Heterocyclic Compounds 2017, 53(3), 371–377
Table 1. Antiviral activity of borneol derivatives 5–9 against
influenza virus A/Puerto Rico/8/34 (H1N1)pdm09
Compound
CC50*, μM
IC50**, μM
SI***
301.1 26.2
Not tested
69.1 5.3
Not tested
26.7 3.1
8.7 1.0
>919.2
4
–
5a
5b
68.0 4.4
3
5c
21.4 1.3
2
6a
>919.2
1
6b
231.2 19.3
43.1 3.6
>91.9
3
6c
8.7 1.0
8.0 0.5
>28.8
5
7a
530.0 33.4
156.3 11.4
109.1 8.7
72.2 5.5
67
5
7b
8
12.2 1.3
9.7 0.9
6.7 0.5
14.0 1.5
7.1 0.9
17.5 2.1
41.9 3.8
67.0 4.9
64.2 4.7
208.6 15.4
9
9a
Figure 1. The antiulcer activity of the synthesized compounds in
indomethacin-induced gastric ulcer test.
7
9b
10.1 0.6
2
9c
329.2 14.9
10.7 0.6
24
2
9d
9e
score of 2.0. It should be noted that (–)-borneol itself does
not possess antiulcer activity.
The investigation of analgesic activity of derivatives
9a–d,g showed that all these compounds were inactive in
the acetic acid-induced writhing test. In the hot plate test,
only compound 9g exhibited a tendency to induce
hyperalgesia, reducing the time of animal pain response.
In summary, a novel series of (–)-borneol derivatives
containing different heterocyclic fragments have been
synthesized and screened for their antiviral, antiulcer, and
analgesic activity. Some of the compounds exhibited
promising antiviral and antiulcer activity. Thus, they can
be considered as lead compounds for further development
of more potent inhibitors of influenza virus and antiulcer
agents.
116.9 8.6
608.7 42.3
335.2 26.8
284.1 21.4
1266.2 81.5
7
9f
15
5
9g
Rimantadine
Amantadine
Deitiforin
4
6
* CC50 – cytotoxic concentration causing the death of 50% of cells.
** IC50 – the effective antiviral concentration causing 50% inhibition of
viral replication.
*** SI – selectivity index (the ratio of CC50/ IC50).
case of compounds 9d,g containing fragments of 1-methyl-
1H-imidazole-2(3H)-thione and 1,2,4-triazole, respectively.
The rest of the compounds showed significant antiviral
activity along with high toxicity (low CC50 values) that
resulted in low selectivity.
Experimental
1H NMR spectra were recorded on a Bruker AV400
(400 MHz) spectrometer and 13C NMR JMOD spectra were
recorded on a Bruker DRX 500 (125 MHz) spectrometer in
CDCl3. The chemical shifts are given in ppm relative to
solvent signals (δ(CHCl3) 7.24, δ(CDCl3) 76.9 ppm). The
atom numbering in the compounds (see Supporting
information file) is given for assigning the signals in the
NMR spectra and does not match the standard nomen-
clature of compounds. Optical rotation was measured on a
PolAAr 3005 instrument. High-resolution mass spectra
were recorded with a Thermo Scientific DFS mass spectro-
meter in a full scan mode (m/z 15–500, electron impact
ionization at 70 eV, direct sample introduction). The purity
of target compounds was determined by gas chromato-
graphy using an Agilent 7820A gas chromatograph with
flame ionization detector, Agilent HP-5 capillary column,
helium as carrier gas (flow rate 2 ml/min, flow split ratio
99:1). Column chromatography was performed on
Macherey-Nagel 60–200 µm silica gel. All the target
compounds reported in this publication were of at least
95% purity. Reagents and solvents were purchased from
commercial suppliers and used as received. Dry solvents
were obtained according to standard laboratory procedures.
The antiulcer activity (AA) of some synthesized com-
pounds was studied by applying the indomethacin-induced
gastric ulcer test in rats. The AA score of the substances
was determined as the ratio of the Paul's index (PI) in
control group to the PI of each experimental group. The
substances in question with the AA score greater than or
equal to 2 were considered as effective antiulcer agents.15
Compound 6c synthesized from 3-chloropropanoate of
borneol and containing benzoxazole-2-thiol fragment exhi-
bited significant antiulcer activity. The observation of the
gastric mucosa of the animals treated with compound 6c
prior to the indomethacin administration showed signi-
ficantly reduced ulceration rate (PI 0.8) in comparison with
the animals of the control group (PI 5.0). The experimental
results showed that the AA score of substance 6c (AA 6.5)
was higher than the same score for the reference compound
omeprazole (AA 3.8) (Fig. 1). It is also worth mentioning
that the 3-chloropropanoate derivatives 9a,b,d containing
pyridine, pyrimidine-2-thiol, and 1-methyl-1H-imidazole-
2(3H)-thione fragments slightly reduced the formation of
gastric lesions. Compound 5a, which was one of the bornyl
acetate derivatives, exhibited antiulcer activity with the AA
373

Chemistry of Heterocyclic Compounds 2017, 53(3), 371–377
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
4-CHendo); 1.17–1.27 (1H, m, 5-CHexo); 1.60–1.64 (1H, m,
3-CH); 1.64–1.72 (1H, m, 4-CHexo); 1.83–1.93 (1H, m,
5-CHendo); 2.30–2.39 (1H, m, 2-CHexo); 4.13 (1H, d,
J = 16.0) and 4.16 (1H, d, J = 16.0, 12-CH2); 4.94 (1H,
ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5, J1exo,5exo = 2.2,
1-CHexo); 7.23–7.29 (1H, m, H-16); 7.35–7.41 (1H, m,
H-15); 7.70–7.75 (1H, m, H-17); 7.80–7.84 (1H, m, H-18).
13C NMR spectrum, δ, ppm: 168.3 (s); 164.7 (s); 152.8 (s);
135.3 (s); 125.9 (d); 124.3 (d); 121.5 (d); 120.9 (d); 81.7
(d); 48.8 (s); 47.7 (s); 44.7 (d); 36.2 (t); 35.2 (t); 27.7 (t);
26.8 (t); 19.5 (q); 18.7 (q); 13.3 (q). Found, m/z: 361.1165
[M]+. C19H23O2NS2. Calculated, m/z: 361.1165.
2-chloroacetate (1a). Chloroacetyl chloride (5.6 g, 0.05 mol)
was added under argon atmosphere to a cooled (0–5°С)
mixture of (−)-borneol (4.6 g, 0.03 mol) and Et3N (3.0 g,
0.03 mol) in dry CH2Cl2 (20 ml), followed by stirring the
mixture for 12 h at 23–25°С. Brine was added and the
reaction mixture was extracted with CH2Cl2. The organic
phase was dried over anhydrous Na2SO4, and the solvent
was removed by evaporation. The crude product was puri-
fied by vacuum distillation (bp 105°C at 5 mmHg). Yield
4.5 g (65%), colorless oil. Spectral data were in a good
agreement with those reported for the same compound in
the literature.16
Synthesis of compounds 6a and 7a (General method).
Aqueous 18 M KOH solution (0.2 ml) was added to a
solution of benzoxazole-2-thiol (3) (0.5 g, 3.3 mmol) or
1H-benzimidazole-2-thiol (4) (0.5 g, 3.3 mmol) in 2-PrOH
(5 ml). The mixture was heated to 40°C, and compound 1a
(0.7 g, 3 mmol) was added, followed by stirring of the reaction
mixture at 80°C for 3 h. After the completion of the
reaction, the mixture was cooled to room temperature and
poured into water. The product was extracted several times
with EtOAc, the extract was dried over anhydrous Na2SO4,
and the solvent was removed under reduced pressure. The
residue was purified by flash column chromatography
(hexane – diethyl ether, 100:0→50:50) to yield ester 6a or 7a.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
2-(benzoxazol-2-ylsulfanyl)acetate (6a). Yield 0.30 g
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-chloropropanoate (1b). A solution of 3-chloropropanoic
acid (5.0 g, 46 mmol) in anhydrous CH2Cl2 (10 ml) was
treated with an excess of oxalyl chloride (8.7 g, 69 mmol),
and one drop of N,N-dimethylformamide was added. The
mixture was stirred under argon atmosphere at room
temperature for 4 h. The excess of the oxalyl chloride was
removed on a rotary evaporator. The resulting 3-chloro-
propanoyl chloride was immediately used in the further
reaction. 3-Chloropropanoyl chloride (3.8 g, 0.05 mol)
solution in CH2Cl2 (5 ml) was added to a solution of
(−)-borneol (4.6 g, 0.03 mol) and Et3N (3.0 g, 0.03 mol) in
CH2Cl2 (10 ml) at 0–5°C, and the mixture was stirred under
argon atmosphere at room temperature for 24 h. The
resulting precipitate was removed by filtration. The filtrate
was washed with brine and extracted with CH2Cl2. The
combined organic phase was dried over anhydrous Na2SO4,
and the solvent was removed by evaporation. The crude
product was purified by flash column chromatography
(eluent hexane – ethyl acetate, 100:0→70:30). Yield 4.3 g
1
(28%), white powder. H NMR spectrum, δ, ppm (J, Hz):
0.78 (3H, s, 9-CH3); 0.82 (3H, s, 10-CH3); 0.86 (3H, s,
2
8-CH3); 0.99 (1H, dd, J = 13.7, J2endo,1exo = 3.5, 2-CHendo);
1.05–1.14 (1H, m, 4-CHendo); 1.17–1.27 (1H, m, 5-CHexo);
1.61–1.65 (1H, m, 3-CH); 1.65–1.71 (1H, m, 4-CHexo);
1.81–1.90 (1H, m, 5-CHendo); 2.27–2.37 (1H, m, 2-CHexo);
4.07 (1H, d, J = 16.0) and 4.13 (1H, d, J = 16.0, 12-CH2);
4.94 (1H, ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5, J1exo,5exo = 2.2,
1-CHexo); 7.19–7.28 (2H, m, H-16,17); 7.39–7.43 (1H, m,
H-18); 7.54–7.57 (1H, m, H-15). 13C NMR spectrum,
δ, ppm: 167.9 (s); 163.1 (s); 151.8 (s); 141.6 (s); 124.2 (d);
123.8 (d); 118.4 (d); 109.8 (d); 81.9 (d); 48.8 (s); 47.7 (s);
44.6 (d); 36.2 (t); 34.3 (t); 27.7 (t); 26.7 (t); 19.4 (q); 18.6
(q); 13.2 (q). Found, m/z: 345.1398 [M]+. C19H23NO3S.
Calculated, m/z: 345.1393.
27
1
(59%), yellow oil. [α]D –36.2 (СHCl3, c 0.7). H NMR
spectrum, δ, ppm (J, Hz): 0.80 (3H, s, 9-CH3); 0.84 (3H, s,
2
10-CH3); 0.87 (3H, s, 8-CH3); 0.97 (1H, dd, J = 13.7,
J2endo,1exo = 3.5, 2-CHendo); 1.16–1.33 (2H, m, 4-CHendo
,
5-CHexo); 1.65 (1H, dd, J3,2exo = 4.6, J3,4exo = 4.6, 3-CH);
2
1.67–1.77 (1H, m, 4-CHexo); 1.89 (1H, ddd, J = 12.9,
J5endo, 4endo = 9.3, J5endo,4exo = 4.4, 5-CHendo); 2.30–2.39 (1H, m,
2-CHexo); 2.77 (2H, t, J = 6.6, 12-CH2); 3.74 (2H, t, J = 6.6,
13-CH2); 4.91 (1H, ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5,
J
1exo,5exo = 2.2, 1-CHexo). 13C NMR spectrum, δ, ppm: 170.4 (s);
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
2-(1H-benzimidazol-2-ylsulfanyl)acetate (7a). Yield 0.36 g
80.5 (d); 48.7 (s); 47.7 (s); 44.7 (d); 39.2 (d); 37.8 (d); 36.5
(t); 27.9 (t); 27.0 (t); 19.6 (q); 18.7 (q); 13.3 (q). Found, m/z:
244.1225 [M]+. C13H21O2Cl. Calculated, m/z: 244.1222.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
2-(benzothiazol-2-ylsulfanyl)acetate (5a). 2-Benzothiazole-
2-thiol 2 (0.7 g, 4 mmol) and K2CO3 (1.1 g, 8 mmol) were
added to a solution of compound 1a (0.9 g, 4 mmol) in
acetone (30 ml). The reaction mixture was stirred at room
temperature for 48 h. After completion of the reaction, the
mixture was treated with brine, extracted with ethyl acetate
(3×10 ml), dried over anhydrous Na2SO4, and the solvent
was removed under reduced pressure. The crude product
was purified by flash column chromatography (hexane –
diethyl ether, 100:0→50:50) to yield 0.5 g (37%) of ester
1
(35%), white powder. H NMR spectrum, δ, ppm (J, Hz):
0.81 (3H, s, 9-CH3); 0.85 (3H, s, 10-CH3); 0.88 (3H, s,
2
8-CH3); 1.01 (1H, dd, J = 13.7, J2endo,1exo = 3.5, 2-CHendo);
1.12–1.32 (2H, m, 4-CHendo, 5-CHexo); 1.64–1.76 (2H, m,
3-CH, 4-CHexo); 1.84–1.92 (1H, m, 5-CHendo); 2.31–2.40
(1H, m, 2-CHexo); 3.94 (2H, s, 12-CH2); 4.97 (1H, ddd,
J1exo,2exo = 10.0, J1exo,2endo = 3.5, J1exo, 5exo = 2.2, 1-CHexo);
7.16–7.21 (2H, m, H-16,17); 7.36–7.72 (2H, m, H-15,18).
13C NMR spectrum, δ, ppm: 171.0 (s); 148.2 (s), 122.3 (d);
82.3 (d); 48.8 (s); 47.8 (s); 44.6 (d); 36.3 (t); 34.5 (t); 27.7
(t); 26.8 (t); 19.5 (q); 18.6 (q); 13.3 (q). Found, m/z:
344.1550 [M]+. C19H24O2N2S. Calculated, m/z: 344.1550.
Preparation of compounds 5b,c and 6b,c (General
method). Benzothiazole-2-thiol (2) or 1H-benzimidazole-
2-thiol (3) (1.2 mmol) in acetone (5 ml) and Et3N (0.3 ml,
2 mmol) were added to a solution of compound 1b (0.3 g,
1.4 mmol) in acetone (30 ml). The reaction mixture was
27
5a as white powder, mp 50–51°C. [α]D –20.7 (СHCl3,
c 0.8). 1H NMR spectrum, δ, ppm (J, Hz): 0.77 (3H, s, 9-CH3);
0.82 (3H, s, 10-CH3); 0.85 (3H, s, 8-CH3); 0.99 (1H, dd,
2J = 13.7, J2endo,1exo = 3.5, 2-CHendo); 1.04–1.12 (1H, m,
374

Chemistry of Heterocyclic Compounds 2017, 53(3), 371–377
heated at 40°C for 12 h. After completion of the reaction,
1.19–1.28 (1H, m, 5-CHexo); 1.61–1.65 (1H, m, 3-CH);
1.64–1.74 (1H, m, 4-CHexo); 1.76–1.85 (1H, m, 5-CHendo);
2.22–2.32 (1H, m, 2-CHexo); 2.96 (2H, t, J = 6.7, 12-CH2);
4.44 (2H, t, J = 6.7, 13-CH2); 4.81–4.87 (1H, m, 1-CHexo);
7.20–7.34 (4H, m, H Ar). 13C NMR spectrum, δ, ppm:
179.9 (s); 171.1 (s); 147.0 (s); 131.7 (s); 124.8 (d); 124.2
(d); 110.2 (d); 109.9 (d); 80.8 (d); 48.6 (s); 47.6 (s); 44.6
(d); 41.4 (t); 36.4 (t); 31.4 (t); 27.8 (t); 26.8 (t); 19.5 (q);
18.6 (q); 13.2 (q). Found, m/z: 359.1550 [M]+.
C20H25O3NS. Calculated, m/z: 359.1546.
acetone was removed and brine was added, the mixture was
extracted with ethyl acetate (3×10 ml), the extract was
dried over anhydrous Na2SO4, and then the solvent was
removed under reduced pressure. The crude product was
purified by flash column chromatography (hexane–EtOAc,
100:0→70:30 + 1% MeOH) to yield esters 5b,c or 6b,c.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(benzothiazol-2-ylsulfanyl)propanoate (5b). Yield 0.07 g
1
(15%), colorless oil. H NMR spectrum, δ, ppm (J, Hz):
0.82 (3H, s, 9-CH3); 0.84 (3H, s, 10-CH3); 0.88 (3H, s,
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
acrylate (8). (1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]-
heptan-2-yl 3-chloropropanoate (1b) (0.30 g, 1.4 mmol)
was dissolved in acetone, Et3N (0.3 ml, 2 mmol) was
added, and the mixture was stirred at 40°C for 18 h. After
completion of the reaction, acetone was removed under
reduced pressure and brine was added, the mixture was
extracted with ethyl acetate (3×10 ml), the extract was
dried over anhydrous Na2SO4, and then the solvent was
removed under reduced pressure. Yield 0.19 g (65%),
colorless oil. 1H NMR spectrum, δ, ppm (J, Hz): 0.82 (3H,
s, 9-CH3); 0.85 (3H, s, 10-CH3); 0.89 (3H, s, 8-CH3); 0.99
2
8-CH3); 0.99 (1H, dd, J = 13.7, J2endo,1exo = 3.5, 2-CHendo);
1.16–1.32 (2H, m, 4-CHendo, 5-CHexo); 1.64–1.77 (2H, m,
3-CH, 4-CHexo); 1.85–1.94 (1H, m, 5-CHendo); 2.30–2.40
(1H, m, 2-CHexo); 2.92 (2H, t, J = 6.9, 12-CH2); 3.60 (2H, t,
J = 6.9, 13-CH2); 4.93 (1H, ddd, J1exo,2exo = 10.0,
J1exo,2endo = 3.5, J1exo,5exo = 2.2, 1-CHexo); 7.23–7.29 (1H, m,
H-16); 7.36–7.42 (1H, m, H-19); 7.70–7.74 (1H, m, H-17);
7.83–7.86 (1H, m, H-18). 13C NMR spectrum, δ, ppm: 171.5
(s); 165.8 (s); 153.0 (s); 135.1 (s); 125.8 (d); 124.1 (d);
121.4 (d); 120.8 (d); 80.4 (d); 48.6 (s); 47.6 (s); 44.7 (d);
36.6 (t); 34.6 (t); 28.2 (t); 27.8 (t); 26.9 (t); 19.5 (q); 18.6
(q); 13.3 (q). Found, m/z: 375.1320 [M]+. C20H25NO2S2.
Calculated, m/z: 375.1321.
2
(1H, dd, J = 13.7, J2endo,1exo = 3.5, 2-CHendo); 1.18–1.34
(2H, m, 4-CHendo, 5-CHexo); 1.63–1.78 (2H, m, 3-CH,
4-CHexo); 1.9–2.0 (1H, m, 5-CHendo); 2.30–2.42 (1H, m,
2-CHexo); 4.90–4.95 (1H, m, 1-CHexo); 5.78 (1H, dd,
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(benzoxazol-2-ylsulfanyl)propanoate (6b). Yield 0.09 g
(20%), yellow oil. 1H NMR spectrum, δ, ppm (J, Hz): 0.82
(3H, s, 9-CH3); 0.85 (3H, s, 10-CH3); 0.88 (3H, s, 8-CH3);
3
3
2J = 1.6, J = 10.5, CH=CHcis); 6.12 (1H, dd, Jtr3ans = 17.3,
3Jcis = 10.5, CH=CH2); 6.36 (1H, dd, J = 1.6, J = 17.3,
2
2
0.99 (1H, dd, J = 13.7, J2endo,1exo = 3.5, 2-CHendo); 1.16–
CH=CHtrans). 13C NMR spectrum, δ, ppm: 166.4 (s); 129.9
(t); 128.9 (d); 79.9 (d); 48.7 (s); 47.7 (s); 44.8 (d); 36.6 (t);
28.2 (t); 27.9 (t); 27.0 (t); 19.6 (q); 18.7 (q); 13.4 (q).
Found, m/z: 208.3015 [M]+. C13H20O2. Calculated, m/z:
208.3010.
1.32 (2H, m, 4-CHendo, 5-CHexo); 1.64–1.76 (2H, m, 3-CH,
4-CHexo); 1.84–1.93 (1H, m, 5-CHexo); 2.30–2.40 (1H, m,
2-CHexo); 2.94 (2H, t, J = 6.8, 12-CH2); 3.54 (2H, t, J = 6.8,
13-CH2); 4.93 (1H, ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5,
J
1exo,5exo = 2.2, 1-CHexo); 7.19–7.29 (2H, m, H-16,19); 7.39–
Preparation of compounds 7b, 9a–g (General method).
DBU (0.40 g, 2.5 mmol) was added to a solution of the
appropriate heterocycle (2.5 mmol) in MeCN (15 ml), and
the mixture was gently heated for 15 min. Then compound
1b (0.60 g, 2.5 mmol) was added, and the mixture was
refluxed for 8 h. After the completion of reaction, MeCN
was removed under reduced pressure, brine was added, the
mixture was extracted with ethyl acetate (3×10 ml), the
combined extracts were dried over anhydrous Na2SO4, and
the solvent was removed under reduced pressure. The
crude product was purified by flash column chromato-
graphy (hexane–EtOAc, 100:0→70:30 + 1% MeOH).
Bis((1S,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl)
3,3'-(2-thioxo-1H-benzimidazole-1,3(2H)-diyl)dipropanoate
(7b). Yield 0.78 g (63%), white powder, mp 115°С.
1H NMR spectrum, δ, ppm (J, Hz): 0.72 (6H, s, 9,9'-CH3);
0.81 (6H, s, 10,10'-CH3); 0.84 (6H, s, 8,,8'-CH3); 0.82–0.88
7.43 (1H, m, H-17); 7.56–7.60 (1H, m, H-18). 13C NMR
spectrum, δ, ppm: 171.5 (s); 164.3 (s); 151.8 (s); 141.7 (s);
124.2 (d); 123.8 (d); 118.3 (d); 109.8 (d); 80.6 (d); 48.7 (s);
47.5 (s); 44.7 (d); 36.6 (t); 34.5 (t); 27.9 (t); 27.1 (t); 27.0
(t); 19.6 (q); 18.7 (q); 13.4 (q). Found, m/z: 359.1553 [M]+.
C20H25NO3S. Calculated, m/z: 359.1550.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(2-thioxobenzothiazol-3(2H)-yl)propanoate (5c). Yield
0.08 g (18%), white powder. H NMR spectrum, δ, ppm
1
(J, Hz): 0.74 (3H, s, 9-CH3); 0.83 (3H, s, 10-CH3); 0.85
(3H, s, 8-CH3); 0.84–0.90 (1H, m, 2-CHendo); 1.09–1.30
(2H, m, 4-CHendo, 5-CHexo); 1.61–1.65 (1H, m, 3-CH); 1.65–
1.74 (1H, m, 4-CHexo); 1.77–1.87 (1H, m, 5-CHendo); 2.24–
2.34 (1H, m, 2-CHexo); 2.88 (2H, t, J = 7.4, 12-CH2); 4.69
(2H, t, J = 6.8, 13-CH2); 4.82–4.87 (1H, m, 1-CHexo); 7.25–
7.34 (2H, m, H-16,19); 7.36–7.48 (2H, m, H-17,18).
13C NMR spectrum, δ, ppm: 189.0 (s); 171.0 (s); 141.0 (s);
127.6 (s); 126.9 (d); 124.7 (d); 121.3 (d); 112.3 (d); 80.7
(d); 48.6 (s); 47.6 (s); 44.6 (d); 41.9 (t); 36.4 (t); 31.4 (t);
27.8 (t); 26.9 (t); 19.5 (q); 18.6 (q); 13.3 (q). Found, m/z:
375.1323 [M]+. C20H25NO2S2. Calculated, m/z: 375.1321.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(2-thioxobenzoxazol-3(2H)-yl)propanoate (6c). Yield
(2H, m, 2,2'-CHendo); 1.07–1.26 (4H, m, 4,4'-CHendo
,
5,5'-CHexo); 1.59–1.63 (2H, m, 3,3'-CH); 1.63–1.71 (2H, m,
4,4'-CHexo); 1.76–1.85 (2H, m, 5,5'-CHendo); 2.22–2.32 (2H,
m, 2,2'-CHexo); 2.90 (4H, t, J = 7.2, 12,12'-CH2); 4.57 (4H,
t, J = 7.2, 13,13'-CH2); 4.79–4.85 (2H, m, 1,1'-CH); 7.20–
7.23 (2H, m, H-16,19); 7.27–7.32 (2H, m, H-17,18).
13C NMR spectrum, δ, ppm: 171.5 (s); 168.8 (s); 131.6 (s);
123.0 (d); 109.3 (d); 80.5 (d); 48.6 (s); 47.8 (s); 44.7 (d);
40.3 (t); 36.5 (t); 32.5 (t); 27.8 (t); 26.9 (t); 19.5 (q), 18.7
(q), 13.3 (q). Found, m/z: 566.3170 [M]+. C33H46O4N2S.
Calculated, m/z: 566.3173.
25
0.16 g (37%), white powder, mp 159.7°C. [α]D –26.5
1
(СHCl3, c 0.74). H NMR spectrum, δ, ppm (J, Hz): 0.71
(3H, s, 9-CH3); 0.82 (3H, s, 10-CH3); 0.84 (3H, s, 8-CH3);
0.84–0.90 (1H, m, 2-CHendo); 1.09–1.18 (1H, m, 4-CHendo);
375

Chemistry of Heterocyclic Compounds 2017, 53(3), 371–377
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
13C NMR spectrum, δ, ppm: 171.8 (s); 161.9 (s); 117.9 (d);
117.2 (d); 80.5 (d); 48.6 (s); 47.7 (s); 44.7 (d); 43.6 (t);
36.5 (t); 34.9 (q); 33.1 (t); 27.8 (t); 26.9 (t); 19.5 (q); 18.7
(q); 13.4 (q). Found, m/z: 322.1716 [M]+. C17H26N2O2S.
Calculated, m/z: 322.1710.
3-(pyridin-2-ylsulfanyl)propanoate (9a). Yield 0.4 g
(51%), colorless oil. [α]D27 –30.7 (СHCl3, c 0.84). 1H NMR
spectrum, δ, ppm (J, Hz): 0.79 (3H, s, 9-CH3); 0.82 (3H, s,
2
10-CH3); 0.86 (3H, s, 8-CH3); 0.96 (1H, dd, J = 13.7,
J2endo,1exo = 3.5, 2-CHendo); 1.13–1.29 (2H, m, 4-CHendo
,
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-[(1H-1,2,4-triazol-3-yl)sulfanyl]propanoate (9e). Yield
5-CHexo); 1.59–1.64 (1H, m, 3-CH); 1.65–1.75 (1H, m,
4-CHexo); 1.83–1.93 (1H, m, 5-CHendo); 2.23–2.41 (1H, m,
2-CHexo); 2.75 (2H, t, J = 6.9, 12-CH2); 3.41 (2H, t, J = 6.9,
13-CH2); 4.88 (1H, ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5,
J1exo,5exo = 2.2, 1-CHexo); 6.88–6.95 (1H, m, H-17); 7.08–
7.13 (1H, m, H-15); 7.38–7.44 (1H, m, H-16); 8.33–8.41
(1H, m, H-18). 13C NMR spectrum, δ, ppm: 172.1 (s);
158.0 (s); 149.2 (d); 135.7 (d); 122.2 (d); 119.2 (d); 80.0
(d); 48.6 (s); 47.6 (s); 44.6 (d); 36.5 (t); 34.8 (t); 27.8 (t);
26.9 (t); 24.8 (t); 19.5 (q); 18.6 (q); 13.3 (q). Found, m/z:
319.1606 [M]+. C18H25O2NS. Calculated, m/z: 319.1601.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(pyrimidin-2-ylsulfanyl)propanoate (9b). Yield 0.4 g
1
0.20 g (35%), colorless oil. H NMR spectrum, δ, ppm
(J, Hz): 0.79 (3H, s, 9-CH3); 0.83 (3H, s, 10-CH3); 0.85
2
(3H, s, 8-CH3); 0.95 (1H, dd, J = 13.7, J2endo,1exo = 3.5,
2-CHendo); 1.13–1.30 (2H, m, 4-CHendo, 5-CHexo); 1.61–1.65
(1H, m, 3-CH); 1.65–1.75 (1H, m, 4-CHexo); 1.80–1.89
(1H, m, 5-CHendo); 2.26–2.36 (1H, m, 2-CHexo); 2.81 (2H, t,
J = 6.9, 12-CH2); 3.38 (2H, t, J = 6.9, 13-CH2); 4.88 (1H,
ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5, J1exo,5exo = 2.2,
1-CHexo); 8.18 (1H, s, H-15). 13C NMR spectrum, δ, ppm:
172.1 (s); 156.6 (br. s); 146.9 (br. d); 80.6 (d); 48.6 (s);
47.6 (s); 44.6 (d); 36.49 (t); 35.0 (t); 27.8 (t); 27.5 (t); 26.9
(t); 19.5 (q); 18.6 (q); 13.3 (q). Found, m/z: 309.1504 [M]+.
C15H23N3O2S. Calculated, m/z: 309.1506.
30
(55%), pale yellow oil. [α]D –30.5 (СHCl3, c 0.76).
1H NMR spectrum, δ, ppm (J, Hz): 0.79 (3H, s, 9-CH3);
0.82 (3H, s, 10-CH3); 0.85 (3H, s, 8-CH3); 0.96 (1H, dd,
2J = 13.7, J2endo,1exo = 3.5, 2-CHendo); 1.14–1.29 (2H, m,
4-CHendo, 5-CHexo); 1.60–1.65 (1H, m, 3-CH); 1.65–1.74
(1H, m, 4-CHexo); 1.81–1.92 (1H, m, 5-CHendo); 2.27–2.36
(1H, m, 2-CHexo); 2.79 (2H, t, J = 7.1, 12-CH2); 3.36 (2H, t,
J = 7.1, 13-CH2); 4.88 (1H, ddd, J1exo,2exo = 10.0,
J1exo,2endo = 3.5, J1exo,5exo = 2.2, 1-CHexo); 6.91–6.96 (1H, m,
H-16); 8.44–8.52 (2H, m, H-15,17). 13C NMR spectrum,
δ, ppm: 172.0 (s); 171.7 (s); 157.1 (d), 116.4 (d); 80.1 (d);
48.6 (s); 47.6 (s); 44.7 (d); 36.6 (t); 34.5 (t); 27.8 (t); 26.9
(t); 25.9 (t); 19.5 (q); 18.6 (q); 13.4 (q). Found, m/z:
320.1563 [M]+. C17H24O2N2S. Calculated, m/z: 320.1553.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(2-thioxothiazolidin-3-yl)propanoate (9c). Yield 0.42 g
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(2,4-dioxothiazolidin-3-yl)propanoate (9f). Yield 0.10 g
(15%), colorless oil. [α]D29 –30.4 (СHCl3, c 0.54). H NMR
1
spectrum, δ, ppm (J, Hz): 0.79 (3H, s, 9-CH3); 0.83 (3H, s,
10-CH3); 0.86 (3H, s, 8-CH3); 0.92–0.97 (1H, m,
2-СHendo); 1.15–1.32 (2H, m, 4-СHendo, 5-CHexo); 1.63–1.66
(1H, m, 3-CH); 1.66–1.76 (1H, m, 4-CHexo); 1.79–1.89
(1H, m, 5-CHendo); 2.27–2.36 (1H, m, 2-CHexo); 2.59–2.69
(2H, m, 12-CH2); 3.84–3.97 (2H, m, 13-CH2); 3.93 (2H, s,
15-CH2); 4.84 (1H, ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5,
J
1exo,5exo = 2.2, 1-CHexo). 13C NMR spectrum, δ, ppm: 171.7
(s); 171.4 (s); 170.9 (s); 81.0 (d); 49.0 (s); 48.1 (s); 45.1
(d); 37.9 (t); 36.9 (t), 34.0 (t); 32.4 (t); 28.3 (t); 27.4 (t);
20.0 (q); 19.1 (q); 13.8 (q). Found, m/z: 325.1344 [M]+.
C16H23NO4S. Calculated, m/z: 325.1342.
30
(60%), white powder, mp 105°C. [α]D –25.4 (СHCl3,
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(1H-1,2,4-triazol-1-yl)propanoate (9g). Yield 0.30 g
1
c 0.52). H NMR spectrum, δ, ppm (J, Hz): 0.80 (3H, s,
27
9-CH3); 0.85 (3H, s, 10-CH3); 0.87 (3H, s, 8-CH3); 0.95
(45%), white powder. [α]D –33.6 (СHCl3, c 0.66).
2
(1H, dd, J = 13.7, J2endo,1exo = 3.5, 2-CHendo); 1.17–1.33
1H NMR spectrum, δ, ppm (J, Hz): 0.72 (3H, s, 9-CH3);
0.80 (3H, s, 10-CH3); 0.83 (3H, s, 8-CH3); 0.81–0.85 (1H,
m, 2-CHendo); 1.07–1.27 (2H, m, 4-CHendo, 5-CHexo); 1.58–
1.62 (1H, m, 3-CH); 1.62–1.80 (2H, m, 4-CHexo, 5-CHendo);
2.20–2.32 (1H, m, 2-CHexo); 2.82–2.95 (2H, m, 12-CH2);
2.35–2.48 (2H, m, 13-CH2); 4.82 (1H, ddd, J1exo,2exo = 10.0,
(2H, m, 4-CHendo, 5-CHexo); 1.65–1.68 (1H, m, 3-CH); 1.68–
1.77 (1H, m, 4-CHexo); 1.84–1.93 (1H, m, 5-CHendo); 2.28–
2.38 (1H, m, 2-CHexo); 2.80 (2H, t, J = 6.5, 12-CH2); 3.26
(2H, t, J = 6.5, 13-CH2); 3.99 (2H, t, J = 6.2, 16-CH2); 4.18
(2H, t, J = 6.2, 15-CH2); 4.87 (1H, ddd, J1exo,2exo = 10.0,
J1exo,2endo = 3.5, J1exo,5exo = 2.2, 1-CHexo). 13C NMR
spectrum, δ, ppm: 196.9 (s); 171.9 (s); 80.6 (d); 57.9 (t);
48.6 (s); 47.7 (s); 44.9 (t); 44.6 (d); 36.5 (t); 31.8 (t); 27.8
(t); 27.6 (t); 26.9 (t); 19.5 (q); 18.6 (q); 13.4 (q). Found, m/z:
327.1325 [M]+. C16H25NO2S2. Calculated, m/z: 327.1321.
(1S,2R,4S)-1,7,7-Trimethylbicyclo[2.2.1]heptan-2-yl
3-(3-methyl-2-thioxoimidazolidin-1-yl)propanoate (9d).
J
1exo,2endo = 3.5, J1exo,5exo = 2.2, 1-CHexo); 7.88 (1H, s, H-15);
8.08 (1H, s, H-14). 13C NMR spectrum, δ, ppm: 170.6 (s);
151.9 (d); 143.4 (d); 80.7 (d); 48.5 (s); 47.6 (s); 44.9 (t);
44.5 (d); 36.4 (t); 34.2 (t); 27.7 (t); 26.8 (t); 19.4 (q); 18.6
(q); 13.3 (q). Found, m/z: 277.1788 [M]+. C15H23N3O2.
Calculated, m/z: 277.1785.
Biological studies. Cytotoxicity assessment. Micro-
tetrazolium test (MTT) was used to study the cytotoxicity
of the compounds.17 A series of threefold dilutions of each
compound (300–3 µg/ml) in minimal essential medium
(MEM) were prepared. MDCK cells were incubated for 48 h
at 37°C under 5% CO2 atmosphere in the presence of
dissolved study compounds. The degree of destruction of
the cell monolayer was then evaluated by the micro-
tetrazolium test (MTT). The cells were washed twice with
saline, and a solution of 3-(4,5-dimethylthiazolyl-2)-2,5-
diphenyltetrazolium bromide (ICN Biochemicals Inc.,
30
Yield 0.30 g (47%), white powder, mp 95°C. [α]D –26.9
1
(СHCl3, c 0.52). H NMR spectrum, δ, ppm (J, Hz): 0.77
(3H, s, 9-CH3); 0.83 (3H, s, 10-CH3); 0.86 (3H, s, 8-CH3);
2
0.90 (1H, dd, J = 13.7, J2endo,1exo = 3.5, 2-CHendo); 1.26–
1.29 (2H, m, 4-CHendo, 5-CHexo); 1.61–1.65 (1H, m, 3-CH);
1.66–1.75 (1H, m, 4-CHexo); 1.80–1.88 (1H, m, 5-CHendo);
2.25–2.35 (1H, m, 2-CHexo); 2.88 (2H, t, J = 6.0, 12-CH2);
3.57 (3H, s, 17-CH3); 4.29 (2H, t, J = 6.0, 13-CH2); 4.84
(1H, ddd, J1exo,2exo = 10.0, J1exo,2endo = 3.5, J1exo,5exo = 2.2,
1-CHexo); 6.62 (1H, br. s, H-15); 6.82 (1H, br. s, H-16).
376

Chemistry of Heterocyclic Compounds 2017, 53(3), 371–377
Aurora, OH, USA) (0.5 mg/ml) in phosphate-buffered
the hind paw or jumping occurred was recorded by a
stopwatch.20
saline was added to the wells. After 1 h incubation, the
wells were washed and the formazan residue dissolved in
DMSO (0.1 ml per well). The optical density of cells was
then measured on a Victor 2 1440 multifunctional reader
(Perkin Elmer, Finland) at 535 nm and plotted against the
concentration of the compounds. Each concentration was
tested in three parallel tests. The 50% cytotoxic dose
(CC50) of each compound (i.e., the compound concentra-
tion that caused the death of 50% cells in a culture, or
decreasing the optical density to one half of the value in
control wells) was calculated from the data obtained.
1
The Supplementary information file, containing H and
13C NMR spectra of compounds 2–3 a–c, 4a,b, 6a–g, is
available from the journal website at http://
link.springer.com/journal/10593.
This work was supported by the Russian Foundation for
Basic Research (grant No. 15-03-00193).
References
Antiviral activity. To assess the antiviral activity, cells
were infected with 100 TCID50 of influenza virus A/Puerto
Rico/8/34 (H1N1) in the presence of threefold dilutions of
compounds, and the virus titer was further measured by
TCID50 titration. Based on the data obtained, 50%
cytotoxic concentration CC50 (the concentration resulting in
the death of 50% of cells), 50% inhibiting concentration
IC50 (the concentration resulting in a decrease of virus titer
by 50%) and the selectivity index SI (the ratio of CC50 to
IC50) were calculated.
Antiulcer activity. Female Wistar rats weighing 180–200 g
were obtained from the Laboratory of Experimental Animal
Breeding of the Institute of Cytology and Genetics, Novo-
sibirsk, Russia. The animals were kept in environmentally
controlled rooms (21°C, 12 h light and dark cycle) with
free access to water. The animals were fasted for approxi-
mately 24 h prior to the experiment. The agents were
suspended in distilled water containing 0.5% of Tween 80
and were administered to the animals per os in the dose of
100 mg/kg. Omeprazole in the dose of 100 mg/kg was used
as a reference compound. The animals in the control group
were treated with distilled water containing Tween 80.
Indomethacin aqueous suspension was administered to the
rats per os in the dose of 25 mg/kg 1 h later to induce ulce-
ration.18 All the animals were sacrificed 24 h after the
administration of indomethacin, their stomachs were
excised and observed for lesions. The Pauls' index (PI)
representing the degree of ulceration was calculated for
every experimental group using the following formula:
PI = (A × B)/100%, where A is the mean number of ulcers
per animal and B is the percent of animals with ulcerations
in the group. The substances in question with the AA score
greater than or equal to 2 were considered as effective
antiulcer agents.
Analgesic tests. The studies were carried out on outbred
albino mice weighing 20–25 g obtained from the
Laboratory of Experimental Animal Breeding of the
Institute of Cytology and Genetics, Novosibirsk, Russia.
The agents were dissolved in distilled water containing
0.5% of Tween 80 just before use and were administered
per os in the dose of 10 mg/kg for compound 9g and in the
dose of 20 mg/kg for compounds 9a–d 1 h before the acetic
acid-induced writhing test and hot plate test. In the acetic
acid-induced writhing test, the pain reaction was determined
by the number of abdominal convulsions, recorded from
the 5th to 8th min following the acetic acid injection (0.75
%, 0.1 ml/10 g of body weight).19 In the hot plate test,
animals were placed individually on a metallic plate
warmed to 54 0.5°C, and the time until either licking of
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