Synthesis of (1S)-(+)-camphor-10-sulfonic acid derivatives and investigations in vitro and in silico of their antiviral activity as the inhibitors of fi lovirus infections

Article abstract of DOI:10.1007/s11172-019-2517-0

N-Heterocycle-containing (1S)-(+)-camphor-10-sulfonamide derivatives were synthesized. Their antiviral activity against the Ebola and Marburg viruses was estimated using a pseudovirus system based on the vesicular stomatitis virus. The derivatives bearing morpholine and triazole moieties demonstrated the highest inhibitory activity towards the Ebola virus glycoprotein. A moderate activity against the Marburg virus was found for a compound containing the piperidine moiety. A molecular modeling of the interaction between the synthesized derivatives and the binding site of glycoprotein of the Ebola virus was performed.

Full text of DOI:10.1007/s11172-019-2517-0

Russian Chemical Bulletin, International Edition, Vol. 68, No. 5, pp. 1041—1046, May, 2019
1041
Synthesis of (1S)-(+)-camphor-10-sulfonic acid derivatives and
investigations in vitro and in silico of their antiviral activity
as the inhibitors of filovirus infections*
A. S. Sokolova,a D. V. Baranova,a,b O. I. Yarovaya,a,b D. S. Baev,a,b O. A. Polezhaeva,c
A. V. Zybkina,c D. N. Shcherbakov,c T. G. Tolstikova,a,b and N. F. Salakhutdinova,b
aN. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences,
9 prosp. Akad. Lavrent´eva, 630090 Novosibirsk, Russian Federation.
E-mail: asokolova@nioch.nsc.ru
bNovosibirsk State University,
2 ul. Pirogova, 630090 Novosibirsk, Russian Federation
cState Research Center of Virology and Biotechnology "Vector",
630559 Koltsovo, Novosibirsk Region, Russian Federation
N-Heterocycle-containing (1S)-(+)-camphor-10-sulfonamide derivatives were synthesized.
Their antiviral activity against the Ebola and Marburg viruses was estimated using a pseudovirus
system based on the vesicular stomatitis virus. The derivatives bearing morpholine and triazole
moieties demonstrated the highest inhibitory activity towards the Ebola virus glycoprotein.
A moderate activity against the Marburg virus was found for a compound containing the pi-
peridine moiety. A molecular modeling of the interaction between the synthesized derivatives
and the binding site of glycoprotein of the Ebola virus was performed.
Key words: Marburg virus, Ebola virus, pseudotyped viruses, (1S)-(+)-camphor-10-sulfonic
acid, N-heterocycles, molecular docking.
The Marburg and Ebola viruses belonging to the filo-
viruses family cause severe hemorrhagic fevers in humans
and nonhuman primates, which are characterized by a high
viremia and multiple organ failure with the mortality rate
of up to 90%. To date, there are neither officially approved
vaccines nor a standard therapy, although some experi-
mental vaccines and treatment methods have demonstrated
promising results on nonhuman primates.1
against the influenza virus. A pronounced inhibitory activ-
ity against the influenza virus was also observed3—5 for
heterocyclic derivatives of (–)-borneol.6,7 We have found
that camphor and borneol heterocyclic derivatives are
promising inhibitors of vaccinia virus, which is a typical
member of the family Orthopoxvirus that includes Variola
Virus.8,9 The antiviral activity of camphor and borneol
derivatives was also investigated against the Marburg virus.
Borneol esters containing six-membered heterocycles were
found promising among the studied derivatives.10 These
compounds possess also an antiulcer activity.11 Thus, the
camphor and borneol moieties are promising for designing
the inhibitors of various viral infections.
In the present work, (1S)-(+)-camphor-10-sulfonic
acid (1) was selected as the starting compound containing
a desired skeleton. It should be noted that some of its
derivatives were previously synthesized in order to evaluate
their biological activity. Potential anti-tuberculosis agents12
and antagonists of chemokine CXCR313 and oxytocin14
receptors have been found among those derivatives, but
the antiviral activity of this class of agents has not been
previously estimated.
Our previous work2 revealed that derivatives of camphor
and borneol (bicyclic monoterpenoids of the 1,7,7-tri-
methylbicyclo[2.2.1]heptane family) exhibit a broad range
of the antiviral activity. Camphor and borneol are used as
pharmaceuticals. Camphor is a component of various
ointments used to control the symptoms of a cold. An oil
solution of camphor administered parenterally causes
analeptic and cardiotonic effects, while its topical applica-
tion has antimicrobial, irritant, analgesic, and anti-inflam-
matory effects. Borneol has been used in traditional
Chinese and Japanese medicine in the cases of uncon-
sciousness and convulsions.
We have already demonstrated that compounds con-
taining a camphor moiety, imino groups and/or tertiary
charged nitrogen atoms exhibit a high antiviral activity
Results and Discussion
* Based on the materials of the V All-Russian Organic Chemistry
Conference (ROCC-V) (September 10—14, 2018, Vladikavkaz,
Russia).
The target compounds were synthesized according to
Scheme 1. At the first step, (1S)-(+)-camphor-10-sulfonyl
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1041—1046, May, 2019.
1066-5285/19/6805-1041 © 2019 Springer Science+Business Media, Inc.

1042 Russ. Chem. Bull., Int. Ed., Vol. 68, No. 5, May, 2019
Sokolova et al.
chloride (2) was prepared. A library of (1S)-(+)-camphor-
10-sulfonamides bearing a heterocyclic moiety was ob-
tained at the second step by the reaction of sulfonyl
chloride 2 with various N-nucleophiles in the presence
of Et3N under stirring at room temperature. The struc-
one cycle. Operations with Marburg and Ebola viruses can
only be performed in laboratories equipped at the highest
biosafety level (BSL-4), which makes the large-scale
screening of various low-molecular compounds difficult.
The usage of pseudovirus systems allows one to screen the
inhibitors of highly pathogenic infections in laboratories
of BSL-2 level. This technology is safe and highly efficient.
According to this procedure, pseudovirus particles that
mimic the molecular features of the surface of a natural
virus are prepared. Since pseudoviruses are not capable of
replication, a high degree of safety in the working environ-
ment is maintained.
1
ture of obtained compounds was determined by H and
13C NMR spectroscopy and high-resolution mass spec-
trometry (HRMS).
Scheme 1
The values of half maximal inhibition concentrations
(IC50) and half maximal cytotoxic concentrations (CC50)
were determined for all the investigated compounds.
According to the acquired experimental data, camphor-
10-sulfonamide derivatives 3a—h inhibit the glycoprotein
of the Ebola virus (GP EBOV) more efficiently than the
glycoprotein of the Marburg virus (GP MARV). This fact
was revealed by a comparison of the IC50 values for the Ebola
pseudovirus, which varied from 0.9 to 540 mol L–1, while
these values for the Marburg virus were in the range of
231—450 mol L–1. The most efficient GP EBOV in-
hibitors were derivatives 3a and 3g bearing moieties of
morpholine and triazole, respectively (IC50 = 0.9 0.5 (3a)
and 1.0 0.4 mol L–1 (3g)). Moreover, these compounds
exhibited a low toxicity, which led to high values of the
selectivity index (SIEBOV) of compounds 3a and 3g
(921 and 1764, respectively). Derivative 3h containing an
aliphatic linker between the sulfamide group and morpho-
line moiety has also demonstrated the high inhibitory
activity, its SIEBOV value was 232. A high SIEBOV value
(134) was also found for piperazine derivative 3d bearing
a N-ethoxycarbonyl substituent at the piperazine ring.
Compounds 3b,c containing the piperazine ring with
an alkyl substituent at the position 4 caused a significantly
lower effect on the ability of Ebola virus to enter into the
host cell (IC50 = 91 4 (3b) and 540 20 mol L–1 (3c)).
Piperidine derivatives 3e—f exhibited a moderate ability
to inhibit the GP EBOV. A well-known antidepressant,
sertraline, was chosen as the reference drug since there are
reported data15 confirming the efficient binding of this
drug to GP EBOV.
Het =
(3a),
(3b),
(3c),
(3d),
(3e),
(3h)
(3f),
(3g),
Currently, the majority of researches on the discovery
of antiviral compounds are aimed at inhibitors of the
specific enzyme of RNA-containing viruses, RNA-de-
pendent RNA polymerase. The replication carried out by
this enzyme is the most important step in the life cycle of
a virus, but its occurrence means that the virus has already
been introduced into the cell. In order to minimize the
virus effect on the body, it is necessary to block it during
its entering into the cell.
Filoviruses and, in particular, the Ebola and Marburg
viruses, contain on their surface only the one glycoprotein
(GP) that ensures the pathogen penetration into the cell.
This protein is a suitable target since it is absent in mam-
malian cells same as the RNA-dependent RNA poly-
merase. The compounds synthesized in the present work
were evaluated as inhibitors of the uptake of filovirus
pathogens into the host cell. The evaluation of inhibitory
activity was performed using pseudotyped viruses of the
To simulate a possible mechanism of GP EBOV block-
ing by the synthesized compounds, we performed the
molecular docking of these compounds into the active
binding site of known inhibitors using an XP (extra preci-
sion) docking algorithm implemented in the Glide program
(Schrödinger Suite16 2016-1). Models (PDB IDs: 6F6S,
6F6N, 6F6I, and 6F5U)17 representing the envelope gly-
coprotein (GP1) of the Ebola virus (Zaire ebolavirus, strain
Mayinga-76) were selected in combination with pharma-
cologically significant inhibitors (resolution of 2.07 Å).
Table 1 shows values of the minimum binding energy
obtained from the calculated docking function. The dock-

Camphor-10-sulfonamide derivatives
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 5, May, 2019
1043
Table 1. Inhibitory activity of the synthesized derivatives against Marburg and Ebola pseudoviruses
b
c
d
Compound
IC50a/mol L–1
CC50
SIEBOV
–Ebind
/mol L–1
/kcal mol–1
GP MARV
GP EBOV
3a
3b
3c
3d
3e
3f
3g
3h
331 11
—
365 9
268 14
231 9
450 20
—
0.9 0.5
540 20
91 4
5 1
829 24
795 25
761 32
671 18
835 40
797 19
1764 59
697 21
—11
921
1.5
8
134
14
16
5.118
4.074
3.601
4.073
5.436
5.398
4.007
3.758
7.835
5.200
6.245
8.387
6.966
8.240
60 8
49 7
1 0.4
3 1
1764
232
—
359 12
—
Benztropine
Bepridil
Ibuprofen
Paroxetine
Toremifene
Sertraline
—
—
—
—11
—
—
—
—11
—
—
—
—11
—
—
—
—11
—
e
—
0.7 0.3
408 26
543
a
IC50 is the concentration that causes death of 50% of cells infected with pseudovirus particles, which display GP belonging to the
Marburg (MARV) or Ebola (EBOV) virus on their surface.
b CC50 is the concentration that causes death of 50% of uninfected cells.
c SIEBOV is the therapeutic index, the ratio of CC50 to IC50(EBOV).
d It is not the true binding energy and should be considered as an estimated value.
e Not determined.
ing was performed in comparison with pharmacologically
significant inhibitors of the Ebola virus glycoprotein:
Benztropine, Bepridil, Paroxetine, Sertraline, Ibuprofen,
and Toremifene. There was a correlation of antiviral activ-
ity observed in vitro and in silico for derivative 3a among
the synthesized compounds. Thus, for compound 3a, the
lowest IC50 was obtained, and the modeling of blocking
of GP EBOV revealed one of the lowest binding energies
comparable to that of Bepridil. Figure 1 shows the non-
covalent interactions of derivative 3a and the reference
drug (Sertraline) with the amino acid residues at the GP
EBOV binding site. The Sertraline configuration is char-
acterized by the penetration of one of the aromatic cycles
into the deep pocket B of the binding site, while the most
of its molecule occupies the central hydrophobic part of
that binding site and the larger pocket A. According to the
docking data, Sertraline does not form any hydrogen bonds
with amino acid residues of the binding site, while in the
ARG64
a
b
LEU184
VAL66
LEU43
ALA101
LEU558
3.00
2.00
3.00
2.00
1.00
0
LEU554
TYR517
1.00
0
–1.00
–2.00
–3.00
–1.00
TYR517
LEU515
–2.00
–3.00
MET548
Fig. 1. Non-covalent interactions of derivative 3a (a) and the reference drug Sertraline (b), with amino acid residues of the binding
site of the glycoprotein of Ebola virus. The interactions are indicated by dashed lines: green lines correspond to the hydrogen bonds
and pink lines represent the hydrophobic interactions.
Note. Figure 1 is available in full color on the web page of the journal (http://link.springer.com/journal/11172).

1044 Russ. Chem. Bull., Int. Ed., Vol. 68, No. 5, May, 2019
Sokolova et al.
quently added to a solution of (1S)-(+)-camphor-10-sulfonyl
chloride (2) (0.5 g, 2.0 mmol) in dichcloromethane. The reaction
mixture was stirred at room temperature for 12 h, washed with
brine, and extracted with chloroform (3×10 mL). The combined
organic layer was dried over calcined Na2SO4, and the solvent
was removed in vacuo. The product was purified by column
chromatography on SiO2 (the eluent was hexane—ethyl acetate
(100 : 00 : 100) + methanol (1%)).
case of derivative 3a, a hydrogen bond between its carbonyl
group and the Arg64 residue of GP EBOV was observed.
The hydrophobic moiety of camphor is located in the
central part of the binding site.
The analysis of inhibitory activity towards GP MARV
for compounds 3a—h revealed that the minimum value of
IC50 is characteristic of derivative 3e bearing the piperidine
moiety. These data are consistent with the results reported
previously,10 whereby a borneol derivative containing both
heterocyclic moiety and ester group linked to a piperidine
ring has proved to be a good inhibitor of Marburg virus
penetration into the cell. The other derivatives either
demonstrated a low inhibitory activity or did not affect the
virus ability to enter into the cell.
Therefore, the present work reports on the synthesis
of new N-heterocycle-containing (1S)-(+)-camphor-10-
sulfonamide derivatives possessing an inhibitory activity
against filoviruses. It should be noted that derivatives 3a
and 3g bearing morpholine and triazole moieties, respec-
tively, exhibited the inhibitory activity against GP EBOV
comparable to that of the reference drug. The acquired
data suggest new approaches for the transformation of
bicyclic terpenoids, camphor and borneol, to synthesize
more efficient inhibitors of especially dangerous viral in-
fections.
7,7-Dimethyl-1-(morpholinosulfonylmethyl)bicyclo[2.2.1]-
heptan-2-one (3a). The yield was 0.45 g (75%), light yellow
crystals. 1H NMR (CDCl3),: 0.85 (s, 3 H, C(9)H3); 1.1 (s, 3 H,
C(8)H3); 1.37—1.44 (m, 1 H, H(4)endo); 1.57—1.65 (m, 1 H,
H(5)endo); 1.92 (d, 1 H, H(2)endo, JH(2)endo,H(2)exo = 18.4 Hz);
1.97—2.06 (m, 1 H, H(4)exo); 2.09 (t, 1 H, H(3), J = 4.5 Hz);
2.36 (dt, 1 H, H(2)exo, JH(2)exo H(2)endo = 18.4 Hz, JH(2)exo,H(3) =
,
= 4.5 Hz); 2.44—2.53 (m, 1 H, H(5)exo); 2.72 (d, 1 H, H(10),
J = 14.5 Hz); 3.25—3.30 (m, 4 H, 2 H(11), 2 H(12)); 3.31 (d, 1 H,
H(10), J = 14.5 Hz); 3.75 (m, 4 H, 2 H(13), 2 H(14)). 13C NMR
(CDCl3),: 19.84 and 19.63 (C(8) and C(9)), 25.0 (C(4)), 26.8
(C(5)), 42.4 (C(2)), 42.7 (C(3)), 44.3 (C(10)), 45.5 (C(11),
C(12)), 47.7 (C(7)), 58.0 (C(6)), 66.4 (C(13), C(14)), 215.2
(C=O). The spectral characteristics are in agreement with those
reported previously.19
7,7-Dimethyl-1-[(4-methylpiperazin-1-ylsulfonyl)methyl]bi-
cyclo[2.2.1]heptan-2-one (3b). The yield was 0.31 g (49%), light
brown crystals, m.p. 132 C. 1H NMR (CDCl3),: 0.85 (s, 3 H,
C(9)H3); 1.10 (s, 3 H, C(8)H3); 1.35—1.47 (m, 1 H, H(4)endo);
1.58—1.68 (m, 1 H, H(5)endo); 1.91 (d, 1 H, H(2)endo
JH(2)endo,H(2)exo = 18.4 Hz); 1.96—2.13 (m, 2 H, H(4)exo, H(3));
2.31 (s, 3 H, H(15)); 2.35—2.61 (m, 6 H, H(2)exo, H(5)exo
,
,
Experimental
2 H(13), 2 H(14)); 2.71 (d, 1 H, H(10), J = 14.5 Hz); 3.08—3.52
(m, 5 H, H(10), 2 H(11), 2 H(12)). 13C NMR (CDCl3),: 19.89
and 19.64 (C(8) and C(9)), 25.0 (C(4)), 26.8 (C(5)), 42.4 (C(2)),
42.7 (C(3)), 44.4 (C(10)), 45.5 (C(11), C(12)), 45.8 (C(15)), 47.8
(C(7)), 54.4 (C(13), C(14)), 58.1 (C(6)), 215.1 (C=O). HRMS,
found: m/z 314.1661 [M]+. Calculated for C15H26N2O3S: 314.1659.
1-[(4-Ethylpiperazin-1-ylsulfonyl)methyl]-7,7-dimethylbi-
cyclo[2.2.1]heptan-2-one (3c). The yield was 0.53 g (81%), light
yellow crystals, m.p. 105 C. 1H NMR (CDCl3),: 0.85 (s, 3 H,
C(9)H3); 1.07 (t, 3 H, C(16)H3, J = 7.2 Hz); 1.11 (s, 3 H, C(8)H3);
1.35—1.45 (m, 1 H, H(4)endo); 1.54—1.69 (m, 1 H, H(5)endo);
1.91 (d, 1 H, H(2)endo, J = 18.4 Hz); 1.97—2.05 (m, 1 H, H(4)exo);
1H and 13C NMR spectra were recorded on Bruker AV-300
(operating frequencies of 300.13 and 75.47 MHz for 1H and 13C,
respectively) and Bruker AV-400 (400.13 and 100.78 MHz, re-
spectively) spectrometers. The residual signals of CDCl3 (H 7.24
and C 76.90) were used as the internal standards. High-resolution
mass spectra (HRMS) were recorded on DFS ThermoScientific
and Agilent 7200 Accurate Mass Q-TOF spectrometers operating
in the full scan mode for the m/z range of 0—500 using electron
impact ionization (70 eV) during the direct sample injection. The
reaction progress and purity of compounds were monitored by
gas chromatography-mass spectrometry (GC-MS) on an Agilent
7890 A gas chromatograph equipped with an Agilent 5975C
quadrupole mass spectrometer as the detector using HP-5MS
quartz column (300000.25 mm) and nebulizer gas (helium).
Melting points were measured on a Mettler Toledo FP900 instru-
ment. The reaction products were isolated using column chrom-
atography on a silica gel (60—200 m, Masherey-Nagel). Freshly
distilled solvents and reagents of the pure grade were used. The
atom numbering in compounds (see Scheme 1) is given for the
assignment of the NMR signals and does not match with that re-
commended by IUPAC. The values of specific rotation []589
were determined on a PolAAr 3005 spectrometer. The specific
rotation is expressed in (deg mL) (g dm)–1, and the concentration
2.06—2.1 (m, 1 H, H(3)); 2.35 (dt, 1 H, H(2)exo, JH(2)exo,H(2)endo
=
= 18.4 Hz, JH(2)exo,H(3) = 3.9 Hz); 2.44 (q, 2 H, 2 H(15),
J = 7.0 Hz); 2.48—2.55 (m, 5 H, 2 H(13), 2 H(14), H(5)exo);
2.70 (d, 1 H, H(10), J = 14.5 Hz); 3.22—3.39 (m, 5 H, H(10),
2 H(11), 2 H(12)). 13C NMR (CDCl3),: 11.85 (C(16)), 19.61
(C(9)), 19.91 (C(8)), 24.96 (C(4)), 26.80 (C(5)), 42.45 (C(2)),
42.65 (C(3)), 44.05 (C(10)), 45.6 (C(11), C(12)), 47.8 (C(7)),
51.91 (C(15)), 52.1 (C(13), C(14)), 57.8 (C(6)), 215.0 (C=O).
HRMS, found: m/z 328.1813 [M]+. Calculated for C16H28N2O3S:
328.1815.
Ethyl 4-[(7,7-dimethyl-2-oxobicyclo[2.2.1]heptan-1-yl)methyl-
sulfonyl]piperazine-1-carboxylate (3d). The yield was 0.45 g
1
(61%), yellow crystals, m.p. 90 C. H NMR (CDCl3),: 0.85
of the solution is in (g) (100 mL)–1
.
(s, 3 H, C(9)H3); 1.10 (s, 3 H, C(8)H3); 1.25 (t, 3 H, C(17)H3,
J = 7.7 Hz); 1.36—1.47 (m, 1 H, H(4)endo); 1.54—1.67 (m, 1 H,
H(5)endo); 1.92 (d, 1H, H(2)endo, J = 18.2 Hz); 1.97—2.07
(m, 1 H, H(4)exo); 2.09 (t, 1 H, H(3), J = 4.8 Hz); 2.36 (dt, 1 H,
H(2)exo, JH(2)exo,H(2)endo = 18.2, JH(2)exo,H(3) = 3.8 Hz);
2.43—2.54 (m, 1 H, H(5)exo); 2.71 (d, 1 H, H(10), J = 14.4 Hz);
(1S)-(+)-Camphor-10-sulfonyl chloride (2) was prepared
according to the known procedure.18
Synthesis of heterocyclic derivatives of (1S)-(+)-camphor-10-
sulfonamide (general procedure). The corresponding N-nucleophile
(5.0 mmol) and triethylamine (0.3 mL, 9.9 mmol) were subse-

Camphor-10-sulfonamide derivatives
Russ. Chem. Bull., Int. Ed., Vol. 68, No. 5, May, 2019
1045
3.2—3.3 (m, 5 H, 2 H(11), 2 H(12), H(10)); 3.55 (br.s, 4 H,
2 H(13), 2 H(14)); 4.13 (q, 2 H, 2 H(16), J = 7.7 Hz). 13C NMR
(CDCl3),: 14.48 (C(17)), 19.61 and 19.84 (C(8), C(9)), 25.0
(C(4)), 26.8 (C(5)), 42.4 (C(2)), 42.6 (C(3)), 43.5 (C(10)), 45.05
(C(11), C(12)), 45.4 (C(13), C(14)), 47.9 (C(7)), 58.1 (C(6)),
61.7 (C(16)), 155.1 (C=O), 215.1 (C=O). HRMS, found:
m/z 372.1715 [M]+. Calculated for C17H28N2O5S: 372.1713.
7,7-Dimethyl-1-[(piperidin-1-ylsulfonyl)methyl]bicyclo[2.2.1]-
heptan-2-one (3e). The yield was 0.35 g (58%), brown viscous
J = 4.7 Hz); 5.83 (br.s, 1 H, NH). 13C NMR (CDCl3),: 19.73
and 19.50 (C(8)), (C(9)), 25.12 (C(16)), 25.75 (C(4)), 26.90
(C(5)), 42.60 (C(3)), 42.76 (C(2)), 43.10 (C(10)), 48.43 (C(15)),
48.6 (C(7)), 53.33 (C(11), C(12)), 57.17 (C(17), 58.74 (C(6)),
66.58 (C(13), C(14)), 216.3 (C=O). HRMS, found: m/z 357.1849
[M]+. Calculated for C17H30N2O4S: 358.1921.
Estimation of the cytotoxicity of compounds 3a—h against
293FT cells. Standardized solutions of the compounds in DMSO
(at the concentration of 100 mmol L–1) were added to a growth
medium containing the target cells of the 293FT line at concen-
trations from 10 to 500 mol L–1. The cells were incubated for
48 h, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo-
lium bromide) was added to the cell cultures to the final concen-
tration of 0.5 mg mL–1, and cells were incubated for additional
4 h. The resulting precipitate of formazan was dissolved by
addition of sodium dodecyl sulfate solution (10%) in 0.01 M
hydrochloric acid to the growth medium. The amount of forma-
zan (proportional to the number of viable cells) was determined
spectrophotometrically measuring the absorption at  = 570 nm.
The 293FT cells incubated in the growth medium containing
DMSO without the tested compounds was used as the reference.
The percentage of viable cells in cultures containing the tested
compounds at different concentrations was estimated according
to the following equation:
1
substance. H NMR (CDCl3), : 0.86 (s, 3 H, C(9)H3); 1.12
(s, 3 H, C(8)H3); 1.34—1.44 (m, 1 H, H(4)endo); 1.49—1.68
(m, 7 H, H(5)endo, 2 H(13), 2 H(14), 2 H(15)); 1.90 (d, 1 H,
H(2)endo, JH(2)endo,H(2)exo = 18.5 Hz); 1.97—2.04 (m, 1 H,
H(4)exo); 2.07 (t, 1 H, H(3), J = 4.5 Hz); 2.36 (dt, 1 H, H(2)exo
,
JH(2)exo,H(2)endo = 18.5 Hz, JH(2)exo,H(3) = 3.8 Hz); 2.50—2.60
(m, 1 H, H(5)exo); 2.69 (d, 1 H, H(10), J = 14.5 Hz); 3.19—3.26
(m, 4 H, 2 H(11), 2 H(12)); 3.3 (d, 1 H, H(10), J = 14.5 Hz).
13C NMR (CDCl3),: 19.84 and 19.63 (C(8) and C(9)), 23.7
(C(15)), 25.0 (C(4)), 25.5 (C(13), C(14)), 26.8 (C(5)), 42.5
(C(2)), 42.7 (C(3)), 44.3 (C(10)), 46.5 (C(11), C(12)), 47.8
(C(7)), 58.2 (C(6)), 215.4 (C=O). HRMS, found: m/z 299.1541
[M]+. Calculated for C15H25NO3S: 299.1550.
7,7-Dimethyl-1-[(4-methylpiperidin-1-ylsulfonyl)methyl]bi-
cyclo[2.2.1]heptan-2-one (3f). The yield was 0.62 g (84%), brown
1
crystals, m.p. 70 C followed by the decomposition. H NMR
(CDCl3), : 0.86 (s, 3 H, C(9)H3); 0.95 (d, 3 H, C(16)H3),
J = 6.6 Hz); 1.12 (s, 3 H, C(8)H3); 1.19—1.31 (m, 2 H, H(13)ax,
H(14)ax); 1.36—1.43 (m, 1 H, H(4)endo); 1.51—1.64 (m, 2 H,
H(5)endo, H(15)); 1.66—1.75 (br.m, 2 H, H(13)eq, H(14)eq); 1.92
Viable cells (%) = A/A0 • 100%,
wherein A and A0 are the absorption of experimental (in the
presence of the tested compound) and control samples, res-
pectively.
(d, 1 H, H(2)endo, J = 18.5 Hz); 1.97—2.09 (m, 2 H, H(4)exo
,
The concentration of a tested compound causing the 50%
survival of the cells as compared to the control sample was as-
sumed as the CC50 value.
H(3)); 2.36 (dt, 1 H, H(2)exo, J = 18.5 Hz, JH(2)exo,H(3) = 4.0 Hz);
2.49—2.58 (m, 1 H, H(5)exo); 2.70 (d, 1 H, H(10), J = 14.4 Hz);
2.73 (m, 2 H, H(11)ax, H(12)ax); 3.3 (d, 1 H, H(10), J = 14.4 Hz);
3.72—3.82 (br.m, 2 H, H(11)eq, H(12)eq). 13C NMR (CDCl3),
: 19.98 and 19.64 (C(8)), (C(9)), 21.50 (C(16)), 24.92 (C(4)),
26.77 (C(5)), 30.30 (C(15)), 33.63 (C(14), C(13)), 42.48 (C(2)),
42.65 (C(3)), 44.32 (C(10)), 46.03 and 45.9 (C(11), C(12)), 47.8
(C(7)), 58.1 (C(6)), 215.0 (C=O). HRMS, found: m/z 313.1699
[M]+. Calculated for C13H27NO3S: 313.1712.
Production of pseudoviruses based on the recombinant vesicular
stomatitis virus (VSV) exposing on their surface either Ebola or
Marburg virus glycoprotein. To obtain pseudoviruses exposing
either the Ebola virus glycoprotein (Mayinga strain) or Marburg
virus glycoprotein (Popp strain) on its surface, the production
cells of 293FT line were initially transfected with a plasmid
containing the gene sequence of this glycoprotein (ph-GPE or
ph-GPM) (5 g of plasmid per 60 mm plate with the production
cells). After 24 h from the transfection, the production cells were
infected with pVSV-G-G (5 L, ~106 of the transducing units).
Four hours after the infection, the infecting pseudovirus was
washed off, and the medium was replaced with the fresh one. The
pseudovirus preparation exposing either the Ebola virus glyco-
protein (pVSV-G-GPE) or the Marburg virus glycoprotein
(pVSV-G-GPM) was harvested 24 h after the infection. The
pseudovirus preparations were stored at –80 C.
Determination of half inhibitory concentrations of the com-
pounds against the pVSV-ΔG-GPE and pVSV-ΔG-GPM pseudo-
viruses and calculation of therapeutic index (SI) values. To estimate
the contagious ability of pseudoviruses, the targeting cells of
HEK293 line seeded into 96-well plates at a monolayer density
of 80–90% were used. The infectivity of pseudoviruses in the
presence of inhibitors and in the control (non-inhibited) samples
was determined according to the luminescence index measured
24 h after the infection. All the measurements were performed
three times determining the average value and standard deviation.
The half maximal inhibitory concentrations (IC50) against the
pVSV-G-GPE and pVSV-G-GPM pseudoviruses were deter-
7,7-Dimethyl-1-[(1H-1,2,4-triazol-1-ylsulfonyl)methyl]bi-
cyclo[2.2.1]heptan-2-one (3g). The yield was 0.17 g (30%), light
1
yellow crystals. H NMR (CDCl3),: 0.88 (s, 3 H, C(9)H3);
1.10 (s, 3 H, C(8)H3); 1.43—1.52 (m, 1 H, H(4)endo); 1.77—1.88
(m, 1 H, H(5)endo); 1.94 (d, 1 H, H(2)endo, J = 18.2 Hz);
2.02—2.12 (m, 1 H, H(4)exo); 2.15 (t, 1 H, H(3), J = 4.5 Hz);
2.23—2.33 (m, 1 H, H(2)exo); 2.38 (dt, 1 H, H(5)exo, J = 18.7 Hz,
J = 3.8 Hz); 3.45 (d, 1 H, H(10), J = 15.0 Hz); 3.89 (d, 1 H,
H(10), J = 15.0 Hz); 8.13 (s, 1 H, H(12)); 8.68 (s, 1 H, H(11)).
13C NMR (CDCl3),: 19.55 (C(8), C(9)), 25.07 (C(4)), 26.82
(C(5)), 42.22 (C(2)), 42.62 (C(3)), 48.30 (C(7)), 52.50 (C(10)),
58.67 (C(6)), 153.99 (C(11), C(12)), 213.1 (C=O). HRMS, found:
m/z 215.0731 [M – C2H2N3]+. Calculated for C10H15O3S: 215.0736.
1-(7,7-Dimethyl-2-oxobicyclo[2.2.1]heptan-1-yl)-N-(3-mor-
pholinopropyl)methanesulfonamide (3h). The yield was 0.54 g
(87%), brown crystals. 1H NMR (CDCl3), : 0.87 (s, 3 H,
C(9)H3); 1.02 (s, 3 H, C(8)H3); 1.36—1.45 (m, 1 H, H(4)endo);
1.64—1.85 (m, 3 H, 2 H(16), H(5)endo); 1.89 (d, 1 H, H(2)endo
,
J = 18.5 Hz); 1.95—2.07 (m, 1 H, H(4)exo); 2.10 (m, 1 H, H(3));
2.28—2.60 (m, 8 H, 2 H(17), 2 H(11), 2 H(12), H(5)exo, H(2)exo);
2.85 (d, 1 H, H(10), J = 15.2 Hz); 3.25 (t, 2 H, 2 H(15), J = 6.2 Hz);
3.39 (d, 1 H, H(10), J = 15.2 Hz); 3.69 (t, 4 H, 2 H(13), 2 H(14),

1046 Russ. Chem. Bull., Int. Ed., Vol. 68, No. 5, May, 2019
Sokolova et al.
mined for all the studied compounds. For the each compound,
the selectivity index (SI) was consequently calculated as the ratio
of cytotoxicity of the compound and its inhibitory activity against
the virus (CC50/IC50). Sertraline ((1S,4S)-4-(3,4-dichlorophenyl)-
N-methyl-1,2,3,4-tetrahydronaphthalen-1-amine) was selected as
the reference drug inhibiting the Ebola virus infection.
7. A. S. Sokolova, O. I. Yarovaya, A. A. Shtro, M. S. Borisova,
E. A. Morozova, T. G. Tolstikova, V. V. Zarubaev, N. F.
Salakhutdinov, Chem. Heterocycl. Compd., 2017, 53, 371—377.
8. A. S. Sokolova, O. I. Yarovaya, N. I. Bormotov, L. N.
Shishkina, N. F. Salakhutdinov, Med. Chem. Commun., 2018,
9, 1746—1753.
9. A. S. Sokolova, O. I. Yarovaya, N. I. Bormotov, L. N.
Shishkina, N. F. Salakhutdinov, Chem. Biodiversity, 2018, 15,
e1800153.
10. A. A. Kononova, A. S. Sokolova, S. V. Cheresiz, O. I.
Yarovaya, R. A. Nikitina, A. A. Chepurnov, A. G. Pokrovsky,
N. F. Salakhutdonov, Med. Chem. Commun., 2017, 8,
2233—2237.
11. M. S. Borisova, O. I. Yarovaya, M. D. Semenova, T. G.
Tolstikova, N. F. Salakhutdinov, Russ. Chem. Bull., 2018, 67,
558—561.
The authors are grateful to the Chemistry Service
Center for Collective Use of the Siberian Branch of the
Russian Academy of Sciences for carrying out spectral and
analytical measurements.
This work was financially supported by the Russian
Science Foundation (Project No. 17-73-10153; synthesis
of target derivatives 3a—g) and the Russian Foundation
for Basic Research (Project No. 18-04-00458 "Design of
Recombinant Plasmids for Assembly of Filoviral Virus-
Like Particles"; estimation of cytotoxicity of compounds
and production of pseudoviruses based on the recombinant
vesicular stomatitis virus (VSV)).
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Received November 1, 2018;
in revised form December 17, 2018;
accepted December 20, 2018