Synthesis, Structure, and Anti-influenza Activity of 2-(Adamantan-1-yl)-5-aryl-1,3,4-oxadiazoles and 2-(Adamantan-1-yl)-5-aryltetrazoles

Article abstract of DOI:10.1134/S107042801804019X

Two series of new adamantyl derivatives of polynitrogen heterocycles, 2-(adamantan-1-yl)-5-aryl- 1,3,4-oxadiazoles and 2-(adamantan-1-yl)-5-aryl-2H-tetrazoles, have been synthesized, and their structure has been determined by NMR spectroscopy, mass spectr

Full text of DOI:10.1134/S107042801804019X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2018, Vol. 54, No. 4, pp. 633–638. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © D.V. Seliverstova, V.V. Suslonov, V.V. Zarubaev, R.E. Trifonov, 2018, published in Zhurnal Organicheskoi Khimii, 2018, Vol. 54,
No. 4, pp. 630–635.
Synthesis, Structure, and Anti-influenza
Activity of 2-(Adamantan-1-yl)-5-aryl-1,3,4-oxadiazoles
and 2-(Adamantan-1-yl)-5-aryltetrazoles
D. V. Seliverstovaa, V. V. Suslonova, V. V. Zarubaevb, and R. E. Trifonova*
a St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, 199034 Russia
*e-mail: rost_trifonov@mail.ru
b Pasteur St. Petersburg Research Institute of Epidemiology and Microbiology,
ul. Mira 14, St. Petersburg, 197101 Russia
Received September 18, 2017
Abstract—Two series of new adamantyl derivatives of polynitrogen heterocycles, 2-(adamantan-1-yl)-5-aryl-
1,3,4-oxadiazoles and 2-(adamantan-1-yl)-5-aryl-2H-tetrazoles, have been synthesized, and their structure has
been determined by NMR spectroscopy, mass spectrometry, and X-ray analysis. Biological studies in vitro have
revealed high inhibitory activity of some of the synthesized 2-(adamantan-1-yl)-5-aryl-2H-tetrazoles against
H1N1 influenza A viruses in combination with a relatively low selectivity.
DOI: 10.1134/S107042801804019X
Amantadine and rimantadine [adamantan-1-amine
and 1-(adamantan-1yl)ethanamine hydrochlorides] are
traditional drugs used in the prevention and treatment
of influenza A infections [1, 2]. The mechanism of
action of these compounds is based on blocking of the
M2 protein channel of influenza A viruses [3, 4]. These
drugs have been developed several decades ago, and
their efficiency appreciably decreased due to acquired
resistance of some viral strains. Therefore, design of
new drug analogs containing cage hydrocarbon frag-
ments and active against influenza A viruses is a quite
important problem. A promising way of creating new
highly efficient anti-influenza drugs implies replace-
ment of the amino group in amino adamantane deriva-
tives by polynitrogen heterocyclic fragments [5–7].
Among the latter, of particular interest are 1,3,4-oxa-
diazoles and tetrazoles. 1,3,4-Oxadiazole derivatives
exhibit a broad spectrum of biological activity, includ-
ing antibacterial [8], antifungal [9], analgesic [10],
anti-inflammatory [11], and antitumor [12]. Tetrazole
ring is also known as a pharmacophore due to its high
stability in metabolic processes, low toxicity, ability to
form strong hydrogen bonds with proton donors, and
other useful properties [13–16]. A large number of
highly efficient drugs based on 1,3,4-oxadiazole and
tetrazole derivatives are now used in the treatment of
various diseases.
In the present work we synthesized by different
methods two series of new adamantyl derivatives of
polynitrogen heterocycles, 2-(adamantan-1-yl)-5-aryl-
1,3,4-oxadiazoles and 2-(adamantan-1-yl)-5-aryltetra-
zoles, and studied their structure and biological
activity.
2,5-Disubstituted 1,3,4-oxadiazoles can be obtained
by oxidation with molecular iodine of condensation
products of aldehydes and carboxylic acid hydrazides
Scheme 1.
i
ii
H
H
+
RCHO
O
N
N
NH2
N
R
R
N
O
O
N
1
2a–2c
Reagents and conditions: i: EtOH, 6–11 h; ii: I2, K2CO3, DMSO, 100°C, 1–4 h; R = Ph (a), naphthalen-1-yl (b), anthracen-9-yl (c).
633

SELIVERSTOVA et al.
634
Scheme 2.
N
N
H2SO4 (concd.), 40 min
R
N
+
N
N
R
N
OH
H
N
N
3a–3j
4a–4j
R = Ph (a), 2-MeC6H4 (b), 3-MeC6H4 (c), pyridin-4-yl (d), pyridin-2-yl (e), 4-CF3C6H4 (f), 3-CF3C6H4 (g),
2-ClC6H4 (h), 4-ClC6H4 (i), 4-O2NC6H4 (j).
(Scheme 1). Aldehydes containing both electron-donat-
ing and electron-withdrawing substituents and both
aromatic and aliphatic carboxylic acid hydrazides can
be used as starting compounds [17]. However, analo-
gous reactions with sterically hindered carboxylic acid
hydrazides have not been discussed previously. We
have found that the cyclization stage with the forma-
tion of 1,3,4-oxadiazoles 2a–2c is slow and that the
presence of excess iodine is necessary for the reaction
to occur. By optimizing the reaction conditions we
succeeded in obtaining target compounds 2a–2c in
fairly high yields (84–89%; Scheme 1). Initial adaman-
tane-1-carboxylic acid hydrazide (1) was synthesized
by treatment of the corresponding methyl ester with
hydrazine hydrate in ethanol under isothermal con-
ditions in a microwave reactor, which considerably
improved the yield and accelerated the process.
protonated tetrazole, which is responsible for the high
selectivity of the alkylation involving exclusively the
N2 atom of the tetrazole ring [5, 14, 18].
The structure of the isolated compounds was reli-
1
ably proved by H and 13C NMR spectroscopy, high-
resolution mass spectrometry, and X-ray analysis.
1
Their H NMR spectra contained signals typical of the
adamantane fragment and aromatic substituents. In the
13C NMR spectra of oxadiazoles 2a–2c, carbon atoms
of the heterocycle resonated at δC 162–164 and 172–
174 ppm, and in the C5 signal in the spectra of tetra-
zoles 4a–4j was located at δC 162–164 ppm. According
to the X-ray diffraction data for compounds 4f and 4j,
the 2H-tetrazole ring is a planar highly aromatic
system (Figs. 1, 2). The dihedral angle between the
tetrazole ring and the aromatic substituent on C5 is not
large (≤30°), which allows some π-conjugation be-
tween these fragments. The tetrazole ring is partially
sterically shielded by the bulky adamantyl substituent.
5-Substituted NH-tetrazoles 3a–3j were synthe-
sized by azidation of the corresponding nitriles with
dimethylammonium azide in DMFA at 110–115°C
[13, 14]. 2-(Adamantan-1-yl)-2H-tetrazoles 4a–4j
were prepared by alkylation of tetrazoles 3a–3j with
adamantan-1-ol in the presence of concentrated sul-
furic acid (Scheme 2). It is presumed that carbenium
ions generated from primary, secondary, and tertiary
alcohols by the action of mineral acids react with
All oxadiazole and tetrazole derivatives 2a–2c and
4a–4j were tested for antiviral activity against in-
fluenza A/Puerto Rico/8/34 viruses (H1N1) (Table 1).
Some adamantyltetrazoles showed a high inhibitory
activity, namely compounds 4a (IC50 0.6 μg/mL),
4b (IC50 5 μg/mL), 4c (IC50 2 μg/mL), and 4h
(IC50 2 μg/mL). However, these compounds also
showed appreciable cytotoxicity, which considerably
reduced the selectivity of their action. Thus, the syn-
thesized compounds can be used as basic structures for
the design of new antiviral agents.
F1
C7
F2
C2
C1
C3
C4
C12
C13
F3
C11
C14
N1
C10
EXPERIMENTAL
C6
C8
N2
C9
C5
The mass spectra (electrospray ionization) were
recorded on a Bruker MicrOTOF mass spectrometer.
C18
N4
C15
1
The H and 13C NMR spectra were measured on
C17
C16
N3
a Bruker Avance III‑400 spectrometer at 400.13 and
100.61 MHz, respectively, using tetramethylsilane as
internal standard. Thin-layer chromatography was
performed on Merck TLC Silica gel 60 F254 plates
using eluent systems individually selected for each
Fig. 1. Structure of the molecule of 2-(adamantan-1-yl)-
5-[4-(trifluoromethyl)phenyl]-2H-tetrazole (4f) according to
the X-ray diffraction data.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 4 2018

SYNTHESIS, STRUCTURE, AND ANTI-INFLUENZA ACTIVITY
635
O1
particular case; spots were visualized under UV light
C11
C10
C2
N5
(λ 254, 365 nm) or by treatment with iodine vapor. The
melting points were determined with a Wagetechnik
Rapido PHMK micro hot stage. The synthesis of
adamantane-1-carbohydrazide (1) was carried out in
a Biotage Initiator+ microwave reactor (maximum
pressure 30 bar).
C12
C9
C1
C6
C13
C3
C4
N1
O2
C8
C7
N2
C17
C14
C5
15
C
16
N4
N3
C
Adamantane-1-carbohydrazide (1). A mixture of
25.74 mmol of methyl adamantane-1-carboxylate,
128.68 mmol of hydrazine hydrate, and 5 mL of
ethanol was heated for 8 h at 150°C in a microwave
reactor. The mixture was poured into 50 mL of water,
and the precipitate was filtered off, washed with water,
and dried in a thermostat. Yield 4.8 g (96%), white
crystals, mp 153–155°C. 1H NMR spectrum
(DMSO-d6), δ, ppm: 1.57–1.73 m (6H, Ad), 1.76 d
(6H, Ad, J = 2.6 Hz), 1.94 s (3H, Ad), 4.11 s (2H,
NH2), 8.67 s (1H, NH). 13C NMR spectrum
(DMSO-d6), δC, ppm: 28.06, 36.62, 39.06, 39.51 (Ad),
176.79 (C=O). Mass spectrum: m/z 195.1491
[M + H]+. C11H18N2O. Calculated: M 194.2734.
Fig. 2. Structure of the molecule of 2-(adamantan-1-yl)-
5-(4-nitrophenyl)-2H-tetrazole (4j) according to the X-ray
diffraction data.
34.33, 36.25, 39.98 (Ad); 120.56, 125.62, 125.90,
127.08, 128.43, 128.71, 129.21, 129.74, 132.72,
133.90 (Carom); 163.88 and 172.01 (C2, C5). Mass spec-
trum: m/z 353.1623 [M + Na]+. C22H22N2O. Calculated:
M 330.4310.
2-(Adamantan-1-yl)-5-(anthracen-9-yl)-1,3,4-
oxadiazole (2c). Yield 0.175 g (84%), yellow powder,
1
mp 175–177°C. H NMR spectrum (CDCl3), δ, ppm:
1.92–1.80 m (6H, Ad), 2.19 s (3H, Ad), 2.27 d (6H,
Ad, J = 2.3 Hz), 7.52–7.60 m (4H, Harom), 7.96 d (2H,
2-(Adamantan-1-yl)-1,3,4-oxadiazoles 2a–2c
(general procedure). A mixture of 1 mmol of the corre-
sponding aldehyde, 1 mmol of hydrazide 1, and 20 mL
of ethanol was refluxed for 4–11 h (TLC, CCl4–
i-PrOH–AcOH, 85:15:5). The solvent was evaporated
under reduced pressure, the residue was dissolved in
5 mL of DMSO, and 1.7 mmol of iodine and 4.25 mmol
of potassium carbonate were added. The mixture was
heated at 100°C until the reaction was complete (TLC,
CH2Cl2–MeOH, 9:1) and treated with 20 mL of a 5%
solution of sodium thiosulfate, and the precipitate was
filtered off and recrystallized from aqueous ethanol.
H
arom, J = 9.2 Hz), 8.06–8.12 m (2H, Harom), 8.68 s
(1H, Harom). 13C NMR spectrum (CDCl3), δC, ppm:
27.82, 34.69, 36.34, 40.05 (Ad); 117.86, 125.12,
125.63, 127.55, 128.72, 131.04, 131.13, 131.35
(Carom); 162.73, 173.74 (C2, C5). Mass spectrum:
Table 1. Cytotoxicity (CC50), antiviral activity (IC50), and
selectivity indices (SI) of adamantyl-substituted 1,3,4-oxa-
diazoles 2a–2c and tetrazoles 4a–4j against influenza A
viruses (H1N1)
Compound no. CC50, μg/mL
IC50, μg/mL
SI
2a
89.0
270.0
>300.0
4.1
26
130
66
3
2
5
7
3
7
2
8
1
2
2
3
1
5
2-(Adamantan-1-yl)-5-phenyl-1,3,4-oxadiazole
(2a). Yield 0.249 g (89%), white powder, mp 105–
2b
1
107°C. H NMR spectrum (DMSO-d6), δ, ppm: 1.78 s
2c
(6H, Ad), 2.07 s (9H, Ad), 7.61 d.d (3H, Harom, J = 5.6,
3.6 Hz), 8.00 d.d (2H, Harom, J = 7.8, 1.7 Hz).
13C NMR spectrum (DMSO-d6), δC, ppm: 27.64,
34.34, 36.18, 39.86 (Ad); 124.11, 126.89, 129.84,
132.23 (Carom); 163.96 and 172.51 (C2, C5). Mass spec-
trum: m/z 303.1469 [M + Na]+. C18H20N2O. Calculated:
M 280.3710.
4a
0.6
5
4b
12.6
4c
14.1
2
4d
>300.0
>300.0
>300.0
>300.0
3.7
200
36
4e
4f
>300
200
2
2-(Adamantan-1-yl)-5-(naphthalen-1-yl)-1,3,4-
4g
oxadiazole (2b). Yield 0.285 g (86%), white powder,
4h
1
mp 151–153°C. H NMR spectrum (DMSO-d6), δ,
4i
45.4
16
ppm: 1.80 t (6H, Ad, J = 2.8 Hz), 2.09–2.16 m (9H,
Ad), 7.59–7.76 m (3H, Harom), 8.05 d.d (1H, Harom, J =
8.2, 1.4 Hz), 8.18 t (2H, Harom), 9.06 d (1H, Harom).
13C NMR spectrum (DMSO-d6), δC, ppm: 27.70,
4j
>300.0
60.0
>300
12
Rimantadinea
a
Reference drug.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 4 2018

SELIVERSTOVA et al.
636
m/z 403.1772 [M + Na]+. C26H24N2O. Calculated:
M 380.4910.
1.72–1.85 m (6H, Ad), 2.22–2.28 m (3H, Ad), 2.33 d
(6H, Ad, J = 2.9 Hz), 2.41 s (3H, CH3), 7.35 d (1H,
H
arom, J = 7.4 Hz), 7.44 t (1H, Harom, J = 7.6 Hz), 7.83–
5-Substituted tetrazoles 3a–3j (general proce-
dure). Sodium azide, 11.4 mmol, and dimethylamine
hydrochloride, 11.2 mmol, were dissolved in 10 mL of
DMF, 10 mmol of the corresponding nitrile and 5 mL
of DMF were added, and the resulting suspension was
heated for 8 h at 110–115°C. The mixture was cooled
and filtered from the precipitate of sodium chloride,
and the precipitate was washed with 10 mL of DMF on
a filter. The filtrate was diluted with 30 mL of cold
water and acidified with 10% aqueous HCl to pH 2–3.
The precipitate was filtered off, thoroughly washed
with cold water (3×30 mL), and dried in air. The
physical constants and spectral parameters of 3a–3j
were in agreement with published data [13, 14].
7.91 m (2H, Harom). 13C NMR spectrum (DMSO-d6),
δC, ppm: 21.39 (CH3); 29.31, 35.63, 42.10, 64.11
(Ad); 123.95, 127.21, 127.63, 129.55, 131.47, 138.99
(Carom); 163.96 (C5). Mass spectrum: m/z 317.1730
[M + Na]+. C18H22N4. Calculated: M 294.4020.
4-[2-(Adamantan-1-yl)-2H-tetrazol-5-yl]pyridine
(4d). Yield 2.364 g (84%), white crystals, mp 132–
134°C. H NMR spectrum (DMSO-d6), δ, ppm: 1.79 t
(6H, Ad, J = 3.1 Hz), 2.27 q (3H, Ad, J = 2.8 Hz),
2.34 d (6H, Ad, J = 2.9 Hz), 7.93–8.00 m (2H, Py),
8.70–8.76 m (2H, Py). 13C NMR spectrum
(DMSO-d6), δC, ppm: 29.32, 35.68, 42.16, 64.55 (Ad);
120.75, 134.95, 150.91 (Py); 162.02 (C5). Mass spec-
trum: m/z 304.1538 [M + Na]+. C16H19N5. Calculated:
M 281.3630.
1
2-(Adamantan-1-yl)-2H-tetrazoles 4a–4j (general
procedure). Compound 3a–3j, 10 mmol, and adaman-
tan-1-ol, 10 mmol, were dissolved in 25 mL of
94% sulfuric acid. The mixture was kept for 40 min at
room temperature and poured into 150 mL of an ice–
watter mixture. The product was extracted with chloro-
form (2 × 20 mL), the extract was washed with
a 5% aqueous solution of Na2CO3 and with water and
dried over anhydrous MgSO4, and the solvent was
evaporated under reduced pressure.
2-[2-(Adamantan-1-yl)-2H-tetrazol-5-yl]pyridine
(4e). Yield 2.153 g (77%), white crystals, mp 118–
120°C. H NMR spectrum (DMSO-d6), δ, ppm: 1.72–
1
1.85 m (6H, Ad), 2.22–2.29 m (3H, Ad), 2.34 d (6H,
Ad, J = 2.9 Hz), 7.51–7.59 m (1H, Py), 8.01 t.d (1H,
Py, J = 7.7, 1.8 Hz), 8.15 d (1H, Py, J = 7.8 Hz), 8.72–
8.78 m (1H, Py). 13C NMR spectrum (DMSO-d6), δC,
ppm: 29.32, 35.60, 42.11, 64.41 (Ad); 122.80, 125.57,
138.00, 146.95, 150.55 (Py); 163.98 (C5). Mass spec-
trum: m/z 304.1537 [M + Na]+. C16H19N5. Calculated:
M 281.3630.
2-(Adamantan-1-yl)-5-phenyl-2H-tetrazole (4a).
Yield 1.797 g (64%), white crystals, mp 89–91°C.
1H NMR spectrum (DMSO-d6), δ, ppm: 1.78 q (6H,
Ad, J = 2.2 Hz), 2.25 t (3H, Ad, J = 3.1 Hz), 2.34 d
(6H, Ad, J = 2.9 Hz), 7.45–7.66 m (3H, Harom), 8.01–
8.15 m (2H, Harom). 13C NMR spectrum (DMSO-d6),
δC, ppm: 29.31, 35.63, 42.11, 64.16 (Ad); 126.78,
127.69, 129.66, 130.84 (Carom), 163.89 (C5). Mass
spectrum: m/z 303.1565 [M + Na]+. C17H20N4. Calcu-
lated: M 280.3750.
2-(Adamantan-1-yl)-5-(4-trifluoromethyl-
phenyl)-2H-tetrazole (4f). Yield 2.938 g (84%),
white crystals, mp 120–122°C. H NMR spectrum
1
(DMSO-d6), δ, ppm: 1.79 t (6H, Ad, J = 3.0 Hz), 2.23–
2.29 m (3H, Ad), 2.35 d (6H, Ad, J = 2.9 Hz), 7.93 d
(2H, Harom, J = 8.2 Hz), 8.28 d (2H, Harom, J = 8.0 Hz).
13C NMR spectrum (DMSO-d6), δC, ppm: 29.31,
35.58, 42.08, 64.57 (Ad), 123.07, 125.78 (CF3),
126.67, 126.71, 127.55, 131.47 (Carom), 130.36,
130.68, 130.99, 131.31 (C4′), 162.74 (C5). Mass spec-
trum: m/z 371.1460 [M + Na]+. C18H19F3N4. Calculat-
ed: M 348.3732.
2-(Adamantan-1-yl)-5-(2-methylphenyl)-2H-
tetrazole (4b). Yield 1.90 g (65%), white crystals,
1
mp 84–86°C. H NMR spectrum (DMSO-d6), δ, ppm:
1.72–1.85 m (6H, Ad), 2.22–2.29 m (3H, Ad), 2.34 d
(6H, Ad, J = 3.4 Hz), 2.56 s (3H, CH3), 7.31–7.45 m
(3H, Harom), 7.92 d.d (1H, Harom, J = 7.7, 1.3 Hz).
13C NMR spectrum (DMSO-d6), δC, ppm: 21.56 (CH3),
29.31, 35.65, 42.11, 63.97 (Ad); 126.63, 126.92,
129.42, 130.36, 131.81, 137.09 (Carom); 164.24 (C5).
Mass spectrum: m/z 317.1731 [M + Na]+. C18H22N4.
Calculated: M 294.4020.
2-(Adamantan-1-yl)-5-(3-trifluoromethyl-
phenyl)-2H-tetrazole (4g). Yield 3.164 g (91%),
white crystals, mp 129–131°C. H NMR spectrum
1
(DMSO-d6), δ, ppm: 1.79 d (6H, Ad, J = 3.3 Hz),
2.24–2.31 m (3H, Ad), 2.35 d (6H, Ad, J = 2.8 Hz),
7.72 d.d (2H, Harom, J = 16.4, 8.2 Hz), 8.27–8.35 m
(2H, Harom). 13C NMR spectrum (DMSO-d6), δC, ppm:
29.33, 35.72, 42.20, 64.31 (Ad), 122.72, 125.43 (CF3),
123.15, 126.82, 128.87, 131.11, 130.27 (Carom), 130.60,
2-(Adamantan-1-yl)-5-(3-methylphenyl)-2H-
tetrazole (4c). Yield 2.559 g (87%), white crystals,
1
mp 83–85°C. H NMR spectrum (DMSO-d6), δ, ppm:
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 4 2018

SYNTHESIS, STRUCTURE, AND ANTI-INFLUENZA ACTIVITY
637
130.92 (C3′), 162.67 (C5). Mass spectrum:
m/z 371.1447 [M + Na]+. C18H19F3N4. Calculated:
M 348.3732.
109.070(3), β = 97.826(3), γ = 96.119(3)°; V =
802.31(5) Å3; Z = 2; μ(Cu Kα) = 0.951 mm–1; dcalc
=
1.442 g/cm3; –8 ≤ h ≤ 7, –12 ≤ k ≤ 12, –15 ≤ l ≤ 15.
Total of 13842 reflection intensities were measured in
the range 7.508 ≤ 2θ ≤ 152.652°, including 3306 inde-
pendent reflections (Rint = 0.0291, Rσ = 0.0185). Final
divergence factors: R1 = 0.0335, wR2 = 0.1171 [reflec-
tions with I > 2σ(I)]; R1 = 0.0362, wR2 = 0.1211 (all
independent reflections). Residual electron density
ρmin/ρmax = 0.35/–0.20 ē/Å3. CCDC entry no. 1839190.
2-(Adamantan-1-yl)-5-(2-chlorophenyl)-2H-
tetrazole (4h). Yield 2.469 g (78%), white crystals,
1
mp 101–103°C. H NMR spectrum (DMSO-d6), δ,
ppm: 1.78 q (6H, Ad, J = 2.3 Hz), 2.22–2.28 m (3H,
Ad), 2.34 d (6H, Ad, J = 3.0 Hz), 7.55 d.t.d (2H, Harom
,
J = 19.2, 7.4, 1.6 Hz), 7.67 d.d (1H, Harom, J = 7.9,
1.4 Hz), 7.89 d.d (1H, Harom, J = 7.5, 2.0 Hz).
13C NMR spectrum (DMSO-d6), δC, ppm: 29.31,
35.60, 42.10, 64.35 (Ad); 126.86, 128.04, 131.12,
131.82, 132.20, 132.36 (Carom); 162.14 (C5). Mass
spectrum: m/z 337.1199 [M + Na]+. C17H19ClN4. Cal-
culated: M 314.8170.
A single crystal of 4j was obtained by crystalliza-
tion from methanol; C17H19N5O2, M 325.37. Triclinic
crystal system, space group P-1; unit cell parameters:
a = 6.7879(9), b = 8.4931(11), c = 13.935(4) Å; α =
104.165(17), β = 101.222(17), γ = 90.121(10)°; V =
763.0(3) Å3; Z = 2; μ(Mo Kα) = 0.097 mm–1; dcalc
=
2-(Adamantan-1-yl)-5-(4-chlorophenyl)-2H-
tetrazole (4i). Yield 2.965 g (94%), white crystals,
1.416 g/cm3; –8 ≤ h ≤ 6, –11 ≤ k ≤ 11, –18 ≤ l ≤ 18.
Total of 3701 reflection intensities were measured in
the range 6.128 ≤ 2θ ≤ 54.99°, all of which were
independent (Rσ = 0.0568). Final divergence factors:
R1 = 0.0530, wR2 0.1158 [reflections with I > 2σ(I)];
R1 = 0.0675, wR2 = 0.1216 (all independent
1
mp 131–133°C. H NMR spectrum (DMSO-d6), δ,
ppm: 1.79 t (6H, Ad, J = 3.1 Hz), 2.23–2.36 m (9H,
Ad), 7.49–7.57 m (2H, Harom), 8.01–8.09 m (2H, Harom).
13C NMR spectrum (DMSO-d6), δC, ppm: 29.32, 35.71,
42.18, 64.13 (Ad); 126.61, 128.33, 129.48, 135.55
(Carom); 162.97 (C5). Mass spectrum: m/z 337.1191
[M + Na]+. C17H19ClN4. Calculated: M 314.8170.
reflections). Residual electron density ρmin/ρmax
=
0.33/–0.24 ē/Å3. CCDC entry no. 1839189.
2-(Adamantan-1-yl)-5-(4-nitrophenyl)-2H-tetra-
zole (4j). Yield 2.537 g (78%), white crystals, mp 184–
186°C. H NMR spectrum (DMSO-d6), δ, ppm: 1.77–
1.84 m (6H, Ad), 2.25–2.32 m (3H, Ad), 2.36 d
(6H, Ad, J = 3.0 Hz), 8.32 d (2H, Harom, J = 8.9 Hz),
8.39 d (2H, Harom, J = 8.6 Hz). 13C NMR spectrum
(DMSO-d6), δC, ppm: 29.33, 35.66, 42.16, 64.62 (Ad);
124.76, 127.90, 133.65, 148.83 (Carom); 162.27 (C5).
Mass spectrum: m/z 348.1427 [M + Na]+. C17H19N5O2.
Calculated: M 325.3720.
In vitro MTT cytotoxicity assay. The cytotoxicity
of the synthesized compounds was evaluated on
MDCK cell culture which was incubated for 48 h at
36°C in a 5% CO2 atmosphere. Triple dilution series
with concentrations of 300 to 4 μg/mL were prepared
from the compounds on Eagle’s minimal essential
medium (MEM), and MTT assay was performed in
96-well microplates [23, 24]. The cells were washed
twice with saline (0.9% NaCl), and 100 μL of an MTT
[3-(4,5-dimethyl-1,3-thiazol-2-yl)-2,5-diphenyltetrazo-
lium bromide] solution (0.5 μg/mL) in phosphate-buf-
fered saline was added to each well. The microplates
were incubated for 1 h at 36°C, the liquid phase was
removed from the wells, and 0.1 mL of dimethyl
sulfoxide was added to each well. The optical density
was measured at a wavelength of λ 535 nm with
a Victor 2 1440 spectrophotometer, and the compound
concentration resulting in 50% cell death (CC50) was
calculated.
1
The X-ray diffraction data for compounds 4f and 4j
were obtained at 100(2) K on SuperNova and Xcalibur
diffractometers (monochromatized Cu Kα and Mo Kα
radiation, respectively). The structures were solved by
the direct method and by the charge flipping method
using SHELXS [19] and Superflip [20], respectively,
and were refined by the least-squares method in
anisotropic approximation for non-hydrogen atoms
(SHELXL [21] implemented in Olex2 [22]). Mecha-
nical twinning in the crystal structure of 4j was taken
into account using CrysAlisPro (Agilent Tech-
nologies).
In vitro antiviral activity assay. A solution of a
compound to be tested in MEM, 100 μL per well, was
added to MDCK cell monolayer, and the plates were
incubated for 1 h at 36°C in a 5% CO2 atmosphere.
Influenza viruses A/Puerto Rico/8/34 (H1N1), 100 μL
(MOI 0.01), were then added to each well, and the
plates were incubated for 24 h at 36°C in a 5%
A single crystal of 4f was obtained by crystalliza-
tion from methanol; C18H19F3N4, M 348.37. Triclinic
crystal system, space group P-1; unit cell parameters:
a = 6.6619(2), b = 10.2870(4), c = 12.6694(4) Å; α =
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 4 2018

SELIVERSTOVA et al.
638
7. Trifonov, R.E., Saraev, V.V., Ostrovskii, V.A., Zaruba-
ev, V.V., and Kukushkin, V.Yu., RU Patent no. 2553987,
2015; Byull. Izobret., 2015, no. 17.
8. Gaonkar, S.L., Rai, K.M.L., and Prabhuswamy, B., Eur.
J. Med. Chem., 2006, vol. 41, p. 841.
CO2 atmosphere. The virus titer was determined after
24 h on MDCK cells. Ten-fold dilution series were
prepared from the culture liquid, added to the cells,
and incubated for 48 h at 36°C in a 5% CO2 atmo-
sphere. A 100-μL portion of culture liquid from each
well was transferred to a round-bottom well and hem-
agglutination assay was performed. For this purpose,
an equal amount of 1% suspension of chicken erythro-
cytes in saline was added to each well and incubated
for 40 min at room temperature. The infectious titer
was considered as reciprocal to the maximum dilution
that caused complete agglutination of erythrocytes.
The antiviral activity was evaluated by the reduction of
the infectious titer. Based on the obtained data, the
50% effective concentration or the concentration of
a compound at which the virus titer decreased twofold
(IC50) was calculated, and the selectivity index (SI)
was then calculated as the ratio CC50/IC50.
9. Zou, X.J., Lai, L.H., Jin, G.Y., and Zhang, Z.X.,
J. Agric. Food Chem., 2002, vol. 50, p. 3757.
10. Husain, A. and Ajmal, M., Acta Pharm. (Zagreb,
Croatia), 2009, vol. 59, p. 223.
11. Bala, S., Saini, V., Kamboj, S., and Prasad, D.N., Int. J.
Pharm. Sci. Rev. Res., 2012, vol. 17, p. 84.
12. Pinaki, S., Dash, D.K., Yeligar, V.C., Murugesh, K.,
Rajalingam, D., Singh, J., and Maity, T.K., Indian J.
Chem., 2008, vol. 47, p. 460.
13. Ostrovskii, V.A., Popova, E.A., and Trifonov, R.E., Adv.
Heterocycl. Chem., 2017, vol. 123, p. 1.
14. Ostrovskii, V.A., Koldobskii, G.I., and Trifonov, R.E.,
Comprehensive. Heterocyclic. Chemistry III, Kat-
ritzky, A.R., Ramsden, C.A., Scriven, E.F.V.,
Taylor, R.J.K., and Zhdankin, V.V., Eds., Oxford:
Elsevier, 2008, vol. 6, p. 257.
15. Ostrovskii, V.A., Trifonov, R.E., and Popova, E.A.,
Russ. Chem. Bull., Int. Ed., 2012, vol. 61, p. 768.
16. Popova, E.A. and Trifonov, R.E., Russ. Chem. Rev.,
Physicochemical studies were performed at the
Magnetic Resonance Research Center, Chemical
Analysis and Materials Research Center, and Center
for X-Ray Diffraction Studies of the St. Petersburg
State University.
2015, vol. 84, p. 891.
This study was performed under financial support
by the Russian Science Foundation (project no. 17-13-
01124).
17. Yu, W., Huang, G., Zhang, Y., Liu, H., Dong, L., Yu, X.,
Li, Y., and Chang, J., J. Org. Chem., 2013, vol. 78,
p. 10337.
18. Lisakova, A.D., Ryabukhin, D.S., Trifonov, R.E.,
Ostrovskii, V.A., and Vasilyev, A.V., Tetrahedron Lett.,
2015, vol. 56, p. 7020.
REFERENCES
1. Oxford, J.S. and Galbraith, A., Pharmacol. Ther., 1980,
vol. 11, p. 181.
19. Sheldrick, G.M., Acta Crystallogr., Sect. A, 2008,
vol. 64, p. 112.
2. Dolin, R., Reichman, R.C., Madore, H.P., Maynard, R.,
Linton, P.N., and Webber-Jones, J., New Engl. J. Med.,
1982, vol. 307, p. 580.
20. Palatinus, L., Prathapa, S.J., and Van Smaalen, S.,
J. Appl. Crystallogr., 2012, vol. 45, p. 575.
3. Sugrue, R.J. and Hay, A.J., Virology, 1991, vol. 180,
21. Sheldrick, G.M., Acta Crystallogr., Sect. C, 2015,
p. 617.
vol. 71, p. 3.
4. Hay, A.J., Semin. Virol., 1992, vol. 3, p. 21.
22. Dolomanov, O.V., Bourhis, L.J., Gildea, R.J.,
Howard, J.A.K., and Puschmann, H., J. Appl.
Crystallogr., 2009, vol. 42, p. 339.
23. Baltina, Lidia A., Zarubaev, V.V., Baltina, Lia A.,
Orshanskaya, I.A., Fairushina, A.I., Kiselev, O.I., and
Yunusov, M.S., Bioorg. Med. Chem. Lett., 2015, vol. 25,
p. 1742.
5. Zarubaev, V.V., Golod, E.L., Anfimov, P.M., Shtro, A.A.,
Saraev, V.V., Gavrilov, A.S., Logvinov, A.V., and Kise-
lev, O.I., Bioorg. Med. Chem., 2010, vol. 18, p. 839.
6. Trifonov, R.E., Saraev, V.V., Zarubaev, V.V., Anfi-
mov, P.M., Kiselev, O.N., Ostrovskii, V.A., Bokach, N.A.,
and Kukushkin, V.Yu., RU Patent no. 2526263, 2014;
Byull. Izobret., 2014, no. 23.
24. Mosmann, T., J. Immunol. Methods, 1983, vol. 65, p. 55.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 4 2018