Synthesis and antiviral activity of maleopimaric and quinopimaric acids' derivatives

Article abstract of DOI:10.1016/j.bmc.2015.09.006

A series of maleopimaric and quinopimaric acids' derivatives modified in the E-ring, at the carbonyl- and carboxyl-groups were synthesized and evaluated for their activity in vitro against respiratory viruses (influenza; rhinovirus; adenovirus; and SARS), papilloma virus, and hepatitis B and C viruses. The antiviral screening of levopimaric acid diene adducts derivatives was carried out with minimal effect on SARS and influenza type B viruses. Excellent antiviral activity of the ozonolysis product of maleopimaric acid and dihydroquinopimaric methyl-(2-methoxycarbonyl)ethylene amide was found toward papilloma virus (HPV-11 strain) with the selectivity index of SI 30 and 20, respectively. Methyl (2-methoxycarbonyl)ethylene-, 1β-hydroxy-5′-kaprolaktamo- and 4β-hydroxy-4α,14α-epoxy-13(15)-ene-dihydroquinopimaric acid derivatives have also shown activity against replication of HCV nucleic acid and low toxicity.

Full text of DOI:10.1016/j.bmc.2015.09.006

Bioorganic & Medicinal Chemistry xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Review article
Synthesis and antiviral activity of maleopimaric and quinopimaric
acids’ derivatives
b
a
a
Elena V. Tretyakova a, , Irina E. Smirnova , Elena V. Salimova , Victor N. Odinokov
⇑
a Institute of Petrochemistry and Catalysis of the Russian Academy of Sciences, 141 Prospect Oktyabrya, 450075 Ufa, Russian Federation
b Ufa Institute of Chemistry of the Russian Academy of Science, 71 Prospect Oktyabrya, 450054 Ufa, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of maleopimaric and quinopimaric acids’ derivatives modified in the E-ring, at the carbonyl- and
carboxyl-groups were synthesized and evaluated for their activity in vitro against respiratory viruses
(influenza; rhinovirus; adenovirus; and SARS), papilloma virus, and hepatitis B and C viruses. The antiviral
screening of levopimaric acid diene adducts derivatives was carried out with minimal effect on SARS and
influenza type B viruses. Excellent antiviral activity of the ozonolysis product of maleopimaric acid and
dihydroquinopimaric methyl-(2-methoxycarbonyl)ethylene amide was found toward papilloma virus
(HPV-11 strain) with the selectivity index of SI 30 and 20, respectively. Methyl (2-methoxycarbonyl)ethy-
Received 15 June 2015
Revised 1 September 2015
Accepted 3 September 2015
Available online xxxx
Keywords:
Synthesis
Diterpenes
Levopimaric acid
Maleopimaric acid
Quinopimaric acid
Antiviral activity
lene-, 1b-hydroxy-50-kaprolaktamo- and 4b-hydroxy-4
a,14a-epoxy-13(15)-ene-dihydroquinopimaric
acid derivatives have also shown activity against replication of HCV nucleic acid and low toxicity.
Ó 2015 Elsevier Ltd. All rights reserved.
Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
2. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
2.1. Chemistry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
2.2. Evaluation of antiviral activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
3. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4. Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.1. Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2. Chemistry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2.1. Dimethyl 15-hydroxy-18-isopropyl-4,10-dimethyltetradecahydro-8,12-ethenocyclopenta[a]phenanthrene-4,13
(1H)-dicarboxylate (dimethyl 15-hydroxy-cyclopentanonepimarate) 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2.2. Methyl 1-(2-cyanoethoxy)-13-isopropyl-7,10a-dimethyl-4-oxohexadecahydro-1H-4b,12-ethenochrysene-7-carboxylate
(methyl 1-cyanoethyl-dihydroquinopimarate) 21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2.3. Methyl 13-isopropyl-7,10a-dimethyl-1-{[(2E)-3-phenylprop-2-enoyl]oxy}-4-{[(2Z)-3-phenylprop-2-enoyl]oxy}
hexadecahydro-1H-4b,12-ethenochrysene-7-carboxylate (methyl 1,4–dicynnamoyl-dihydroquinopimarate) 27 . . . . . . . . . . . . . 00
4.2.4. 13-Isopropyl-7,10a-dimethyl-7-({[(2E)-3-phenylprop-2-enoyl]oxy}methyl)hexa-decahydro-1H-4b,12-ethenochrysene-1,
4-diyl (2E,20Z)bis(3-phenylacrylate) (1,4,20-tricynnamoyl-dihydroquinopimarate) 28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2.5. Methyl (4E)-4-(hydroxyimino)-13-isopropyl-7,10a-dimethyl-1-oxohexadecahydro-1H-4b,12-ethenochrysene-
7-carboxylate (methyl 4-oxime-dihydroquinopimarate) 31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2.6. Methyl 1-(acetyloxy)-5-isopropyl-6b,10-dimethyloctadecahydro-5,12a-methanochryseno[1,12-bc]furan-10-carboxylate
(methyl 1,13-epoxy-4-acetoxy-dihydroquinopimarate) 35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.3. Evaluation of antiviral activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
⇑
Corresponding author. Fax: +7 (347) 2842750.
E-mail address: tretyakovaelv@gmail.com (E.V. Tretyakova).
http://dx.doi.org/10.1016/j.bmc.2015.09.006
0968-0896/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006

2
E. V. Tretyakova et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
Supplementary data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
References and notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
1. Introduction
trivial product of dimethyldioxirane oxidation proved to be effec-
tive inhibitors of papillomavirus (HPV).28
Tricyclic diterpenoids of abietane series is one of the important
groups of the secondary metabolites, which are widespread in
nature.1 Their natural and synthetic derivatives exhibit a broad
spectrum of biological activities for example, antimicrobial,2
antiviral,3,4 antimalaria,5 antiulcer,6 antileishmaniasis,7 antioxi-
dant,8,9 and others. Abietane diterpenoids exhibited the antitumor
promoting activity10,11 and they are inhibitors of viruses
The present work is an extension of our ongoing efforts toward
developing promising biologically active agents among the
levopimaric acid diene adducts derivatives.20–24,26,28–30 We have
realized the chemical transformations of levopimaric acid diene
adducts with maleic anhydride and p-benzoquinone, resulting in
more than thirty derivatives of maleopimaric and quinopimaric
acids’ modified in the E-ring, at the carbonyl- and carboxyl-groups
were synthesized and their in vitro antiviral activity was evaluated.
reproduction12,13 such as the herpes simplex virus type
1
(HSV-1),14 cytomegalovirus (CMV),15 varicella-zoster virus
(VZV)15 and Epstein-Barr virus.16
2. Results and discussion
2.1. Chemistry
Abietane acids’, such as abietic and levopimaric acids’, readily
available from an oleoresin produced by Pinus or commercial dis-
proportionate rosin and easily reacts with dienophiles giving the
Diels–Alder adducts in high yields.17–19 Diterpene derivatives
obtained by the diene synthesis and their synthetic derivatives
have diverse pharmacological activity, including anti-inflamma-
tory,20–22 antiulcer,23 anticancer24 and antitumor.25 Despite the
variety of biological properties of this compounds family, there
are few data on the antiviral activity study of their derivatives.
So, for dihydroquinopimaric acid amides26 and some frame deriva-
tives of quinopimaric acid27 was set a moderately antiviral activity
against influenza A virus. Dihydroquinopimaric acid and its non-
For the synthesis of maleopimaric acid 131 and quinopimaric
acid 332 pine resin Pinus silvestris containing about 25% levopimaric
acid was used. Dihydroquinopimaric acid 5,33 trimethyl fumaropi-
marate 2,34 and methyl 2,3-epoxyquinopimarate 6,33 as well as
dimethyl cyclopentenonepimarate 733 and dimethyl cyclopen-
tanonepimarate 8,33 were obtained by procedures described before
(Scheme 1).
The reaction of the diester 7 with sodium borohydride in reflux-
ing methanol showed recovery not only of the carbonyl group, but
19
12
O
18
17
H
H
COOCH3
COOCH3
24
23
11
9
16
15
20
13
O
14
iii, iv
1
i
2
10
8
H
H
H
H
3
5
7
O
4
6
H
H
2
1
COOCH3
COOH
21
22
O
O
17
O
1
H
H
H
16
15
H
12
11
2
3
1a
4a
18
13
14
H
ii
v
10b
COOH
4
10
7
10a
4b
9
8
levopimaric acid
H
H
H
6b
vi, iv
5
O
6
H
H
3 R = H
COOH
5
iv
4 R = CH3
COOR
19
20
O
O
22
12
26
H
H
20
21
COOCH3
COOCH3
11
23
13
14
17
16
18
19
O
vii, iv
9
viii
15
1
2
3
10
8
H
H
H
H
H
5
7
O
O
4
6
H
H
H
7
8
24
6
COOCH3
COOCH3
COOCH3
25
COOCH3
ix
H
H
OH
H
9
COOCH3
Scheme 1. Reagents and conditions: (i) maleic anhydride, 200 °C (ii) 1,4-benzoquinone, CHCl3–CH3CN (1:4), 7 days, rt (iii) 15% KOH/MeOH, reflux, 2 h. (iv) CH2N2/Et2O, EtOH,
0 °C (v) Zn/AcOH, 100 °C (vi) 35% H2O2, 6 M NaOH/MeOH, Et2O, 0 °C (vii) 10% NaOH, EtOH, rt (viii) H2, 20% Ni/Raney, MeOH (ix) NaBH4, MeOH, reflux.
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006

E. V. Tretyakova et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
3
O
O
O
H
H
H
COOCH3
COOCH3
i for 10
O
H
ii, iii for 11,12
iv
O
H
H
H
H
COOCH3
O
O
O
H
H
H
COOCH3
C
R
COOH
1
13
10 R= OCH3
O
11 R = NHCH(CH3)CO2CH3
12 R = NHCH(CO2CH3)(CH2)2SCH3
O
O
O
H
H
H
H
H
i for 14
15
ii,iii for
iv
H
H
H
H
OH
O
O
H
H
5
H
COOCH3
COOH
16
C
R
14 R= OCH3
O
15 R = NHCH(CH3)CO2CH3
Scheme 2. Reagents and conditions: (i) CH2N2/Et2O, 0 °C (ii) (COCl)2, CHCl3, rt (iii) NH2CH(CH3)CO2CH3 or NH2CH(CO2CH3)(CH2)2SCH3, Et3N, CHCl3, reflux (iv) O3, CH2Cl2, 0 °C.
OR
OH
H
H
H
20, 22,
iv for
v for
21
vi for 23,24
i
H
H
H
O
O
H
H
20-24
17
COOCH3
COOCH3
O
O
OH
OR
H
H
H
iv for 25
ii
vi for 26, 27
H
H
H
H
H
OH
OH
OR
OR
H
H
H
18
25-27
14
COOCH3
COOCH3
COOCH3
H
H
H
vi
iii
H
H
H
OH
OR
H
H
19
28
CH2OH
CH2OR
O
C
O
C
20 R = COCH3, 21 R = (CH2)2CN, 22, 25 R = CO(CH2)2CO2H, 23, 26 R =
24, 27, 28 R = HC
C
H
N
Scheme 3. Reagents and conditions: (i) NaBH4, MeOH, rt (ii) NaBH4, EtOH, reflux (iii) LiAlH4, THF, rt (iv) (CH3CO)2O or (CH2CO)2O, Py, 115 °C (v) H2C@CHCN, dioxane, BTEAC,
30% KOH, rt, 2 h (vi) cinnamoyl chloride or nicotinic chloride, Py, 115 °C.
a double bond in the cyclopentane ring too. Compound 9 was
obtained in 76% yield after recrystallization from methanol.
Methyl esters of quinopimaric acid 4,32 maleopimaric acid 1031
and dihydroquinopimaric acid 1433 were prepared by methylation
of the corresponding acid with an ethereal solution of dia-
zomethane. Functionalization of the carboxylic group of maleopi-
maric 122 and dihydroquinopimaric 526 acids with the
introduction into the molecule of bioactive amino acids fragments
was performed by chloride method. By reacting amides with frag-
Ozonolysis of the methyl esters 10 and 14 at 0 °C in methylene
chloride led to the secoacid 1322 and hemiacetal 16,30 respectively
(Scheme 2).
Hydroxy derivatives 17 and 18 were obtained by reducing dihy-
droquinopimaric acid methyl ester 14 with sodium borohydride,35
and triol 19—in the reduction of lithium aluminum hydride35
(Scheme 3). The alcohol 17 is also characterized as the acetate
20.35 Cyanethylation of the 1b-hydroxy derivative 17 with acryloni-
trile in dioxane in the presence of alkali and a phase transfer catalyst
benzyltriethylammonium chloride (BTEAC) leads to compound 21,
isolated in 40% yield after column chromatography (Scheme 3).
ments of
L-alanine 11, 15 and L-methionine 12 was obtained
(Scheme 2).
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006

4
E. V. Tretyakova et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
O
O
O
H
H
H
O
H
H
O
O
O
i
iii
ii
H
H
H
H
H
H
H
NOH
OH
O
NOH
H
H
H
H
COOCH3
COOCH3
COOCH3
30
OH
31
COOCH3
29
13
OH
O
H
H
H
H
v
ii
iv
N
H
H
H
H
H
O
H
H
H
H
NOH
33
O
O
H
H
H
H
COOCH3
COOCH3
34
32
COOCH3
17
COOCH3
vii
OCOCH3
vi, vii
O
H
H
H
H
H
H
NOCOCH3
OCOCH3
H
H
COOCH3
36
35
COOCH3
Scheme 4. Reagents and conditions: (i) HO(CH2)2OH, benzene, 80 °C (ii) NH2OH.HCl, Py, 115 °C (iii) HCl, acetone, 53 °C (iv) HCl, MeOH, reflux (v) PCl5, Et2O, reflux (vi) NaBH4,
MeOH, rt (vii) (CH3CO)2O, Py, 115 °C.
Table 1
In vitro activities of compounds 1–15, 17–36 against the respiratory viruses (concentration in lM)
Compound
Virus Flu A (H1N1), strain
California/07/2009 cell line
MDCK
Virus Flu A (H3N2), strain
Brisbane/10/2007 cell line
MDCK
Virus Flu A (H5N1), strain
Vietnam/1203/2004H cell line
MDCK
Virus Flu B, strain Florida/4/
2006 cell line MDCK
EC50
CC50
SI
EC50
CC50
SI
EC50
CC50
SI
EC50
CC50
SI
1
2
3
4
5
6
7
8
9
31
3.8
32
>5.5
—
29
3.1
31
32
31
32
31
32
>100
—
>100
48
>11
>100
>100
>100
32
31
—
29
>17
31
27
>2.9
31
>100
3.2
32
3.2
>4.8
48
9.4
33
5.5
—
34
3.8
34
35
35
34
34
33
>100
—
>100
93
1.5
2.5
1
0
—
1.2
1.2
1.1
1,1
1.1
1.1
1.1
1
0
—
0
1.9
0
0
0
0
1.1
1.1
—
1,1
0
1.1
1.3
0
1
0
1.1
1
1.1
0
37
44
7.6
27
3.9
36
23
3.9
33
24
33
33
30
33
>100
—
>100
64
33
>100
68
>100
33
17
—
4.9
4
33
26
3.3
13
>100
1.6
28
1.2
0
0
1.2
1.1
0
1.2
1
0
1
1
0
1
0
—
0
0
1
0
2
0
1
0
—
0
0
1,1
0
1
0
0
32
—
>30
>2.9
—
3.2
>13
32
3.2
21
32
32
3.2
>100
31
>100
>100
>29
>100
>31
88
35
—
30
2.9
—
3.3
13
32
3.2
32
33
1.1
—
0
0
—
1
0
1
1
1.5
1
1
1
0
1.1
0
0
0
0
0
>1.1
1
0
1
0
0
0
0
1
0
0
0
0
0
0
27
—
>20
>2.9
8.6
36
—
20
2.9
34
3.3
25
31
3.1
8.7
33
1.3
—
0
0
4
1
0
0
0
0
1
1
1.1
>3.1
1.5
0
0
0
0
0
0
1
2.4
1.1
0
0
0
0
1
0
0
0
1.5
0
>7.6
>27
3.2
32
>23
3.2
32
>24
32
32
>30
32
>100
—
>100
>64
32
>100
34
>100
32
>17
—
>4.9
>4
31
>26
3.2
>13
>100
>1.6
>28
>5
3.2
>25
>31
>3.1
>8.7
32
32
3.2
32
22
>100
>100
>31
>100
>52
>100
3.2
10
11
12
13
14
15
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
32
32
3.3
>100
33
>100
>100
29
>100
31
>100
3.2
9
3.2
8.5
8.2
>100
24
3.3
1,7
>100
1.2
28
3.5
>100
33
>100
>100
31
>100
52
>100
3.2
24
11
>100
>100
>100
35
35
—
32
17
35
34
2.9
31
>100
3.5
33
3.2
>9
3.2
10
3.1
3.4
11
9.3
46
>8.5
>8.2
>100
>24
3.2
>1.7
>100
>1.2
>28
>12
>2.5
>11
>9.3
>46
>27
3.2
>2.4
>100
>1.2
24
27
3.2
2.4
>100
1.2
35
0
0
0
1.1
3.5
4.8
5
3.3
12
2.5
>10
>2.8
10
2.8
3.1
0
EC50, virus inhibitory concentration, 50% endpoint; CC50, cell inhibitory concentration 50% endpoint; SI: CC50/EC50
.
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006

E. V. Tretyakova et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
5
Table 2
In vitro activities of compounds 13, 15, 25, 30, 34 against other viruses (concentration in
l
M)
Compound
Virus rhinovirus type 2 strain
HGP cell line MDCK
Virus adeno strain 65089/
Chicago cell line A-549
Virus SARS strain Urbani cell
line vero 76
Virus HPV strain HPV-11
EC50
CC50
SI
EC50
CC50
SI
EC50
CC50
SI
EC50
CC50
SI
13
15
25
30
34
32
>25
31
3.2
>28
32
25
33
3.2
28
1
0
1.1
1
0
32
32
47
10
9.8
29
1
0
0
0
0
>30
30
3.2
>2.4
6.3
30
32
3.6
2.4
32
0
>50
<25
>50
>50
<50
<50
<25
<50
<50
<50
30a
>47
>10
>9.8
>29
1.1
1.1
0
20a
N/Ab
N/Ab
N/Ab
5.1
EC50, virus inhibitory concentration, 50% endpoint; CC50, cell inhibitory concentration 50% endpoint.
SI: CC50/EC50
.
a
Excellent anti-viral activity at single dose tested; some cellular cytotoxicity.
Cellular cytotoxicity at dilution point tested—retest needed.
b
Table 3
occurs. Hemiketal 32 is readily formed from compound 17 by
refluxing in acidic conditions,37 its reaction with sodium borohy-
dride and subsequent acylation with acetic anhydride resulting
in a yield of 79% to the compound 35. Caprolactam 34 was synthe-
sized by reacting the E-oxime 33 with PCl5 in ether.22 Acetate 36
was synthesized by reacting compound 33 with acetic anhydride.22
Thus, we have performed chemical modifications of the
quinopimaric acid comprising of double bond reduction at C-2
and C-3 and double bond epoxidation with the subsequent con-
traction of cycle E to pentacyclic. The reaction of dimethyl
cyclopentenonepimarate 7 and sodium borohydride proceeds with
the reduction of the keto group and double bond in the pentacyclic
cycle. The functionalization of carboxyl-groups of levopimaric acid
diene adducts (maleopimaric and dihyroquinopimaric acids) by
chloride method led to amides with fragments of the biogenic
amino acids. By acylation of the dihydroquinonopimaric acid
hydroxyderivatives mono-, di- and tri-acylates were prepared.
The synthesis of nitrogen-containing diterpenoids was carried out.
In vitro primary anti-HBV activity of compounds 5, 13, 15, 16, 25, 30, 34
(concentration in
lM)
Compound
Virus HBV, VIR assay
EC50
CC50
EC90
5
13
15
16
25
30
34
62
189
86
59
21
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
20
58
Control drug 3TC, EC50 2399
EC50, virus inhibitory concentration, 50% endpoint; EC90, virus inhibitory concen-
tration, 90% endpoint.
CC50, cell inhibitory concentration 50% endpoint; VIR data are based on extracel-
lular virion HBV DNA.
Functionalization of the hydroxyl groups of the compounds 17–
19 was also carried out by introducing into the diterpenoids struc-
ture of succinic anhydride (hemisuccinates 22, 25),35 and nicotinic
acid chloride (nicotinates 23, 26)35 and cinnamoyl chloride (cinna-
mates 24,35 27, 28) (Scheme 3). Acylation of compounds 18 and 19
was carried by the acid chloride, the compounds 27 b 28 were
obtained after purification by column chromatography in a 61%
and 45% yield respectively.
To get nitrogen-containing derivatives and dihydroquinopi-
maric acid derivatives modifications of the carbonyl function at
position C-4 we used the reaction of ketones 1735 and 2932 with
hydroxylamine hydrochloride (Scheme 4). Individual E-oximes 30
and 33 were obtained by recrystallization of the mixture of E/Z iso-
mers from MeOH.22,36 Under acidic conditions, the removal
ethyleneketal protection of the compound 30 to form the E-oxime
31 in 80% yield after purification by column chromatography
2.2. Evaluation of antiviral activity
The synthesized compounds 1–36 were evaluated in vitro for
their inhibitory activity against respiratory viruses (influenza type
A strains (H1N1), (H3N2), (H5N1); influenza type B; rhinovirus;
adenovirus; and SARS), papilloma virus (HPV), and hepatitis B virus
(HBV) and C (HCV) according to the agreement with National
Institute of Allergy and Infectious Diseases (NIAID), using standard
protocols, published on the website NIAID-AACF.38
The results of evaluation of the antiviral activity of compounds
1–15, 17–36 against influenza viruses types A and B are shown in
Table 1. The results of the antiviral activity of compounds 13, 15,
25, 30, 34 against rhinovirus type 2, adenovirus, SARS and papillo-
mavirus HPV-11 are presented in Table 2. Compounds 1–15, 17–36
Table 4
In vitro primary anti-HCV activity of compounds 5, 13, 15, 16, 25, 30, 34 (concentration in
l
M)
Compound
HCV dose–response assay, cell line Huh7 ET
Antiviral activity HCV RNA % control
Toxicity b-actin RNA % control
Selectivity index (SI) toxicity/antiviral activity
5
13
15
16
25
30
34
0
0.6
88
88.1
54
151.2
6.4
0.2
<1a
<1b
>1a
>1b
<1c
<1c
>1d
>1
60.8
68.4
96.6
97.9
97.3
96.7
102.2
99.1
Positive control Interferon-a (2 IU/mL)
a
b
c
Not active against HCV replicon.
Weakly active against replicon.
Cytotoxic.
d
Active against replicon.
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006

6
E. V. Tretyakova et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
showed a minimal inhibitory effect against four strains of influenza
virus with selectivity index from 0 to 4. Compound 5 shown only
minor activity against influenza type B strain with a 50% effective
4.2. Chemistry
4.2.1. Dimethyl 15-hydroxy-18-isopropyl-4,10-dimethyltetradec-
ahydro-8,12-ethenocyclopenta[a]phenanthrene-4,13(1H)-dicar-
boxylate (dimethyl 15-hydroxy-cyclopentanonepimarate) 9
A solution of 1 mmol (0.45 g) of the compound 7 in 10 ml MeOH
was added portionwise 5 mmol (0.2 g) NaBH4. The reaction mass
was refluxed for 2 h, poured into 20 ml of 5% HCl and the precipi-
concentration (EC50) 8.6
lM and the selectivity index (SI) 4.0 and
the compound 34—against strain SARS (EC50 = 6.3
lM, SI = 5.1).
At the same time, the compounds 13 and 15 showed excellent
activity against papillomavirus (HPV-11 strain). For the compound
13 the selectivity index SI was 30, for the compound 15 SI = 20
(Table 2).
The results of biological screening for compounds 5, 13, 15, 16,
25, 30, 34 against hepatitis B and C are shown in Tables 3 and 4,
tate was filtered off, washed with water, dried and recrystallized
from methanol. Yield 0.35 g (76%), mp 204–205 °C, [
20
a]
+31 (c
D
0.04, CHCl3). 1H NMR (300 MHz, CDCl3): 0.53 (s, 3H, CH3), 0.92
and 0.93 (both d, 6H, J = 6.8 Hz, 2CH3), 1.00–1.10 (m, 3H), 1.15 (s,
3H, CH3), 1.30–1.59 (m, 6H), 1.78–1.90 (m, 6H), 2.11 (sept, 1H,
J = 6.8 Hz, J = 1.2 Hz, H-20), 2.30–2.51 (m, 3H), 2.55 (br s, 1H, H-
12), 2.61 (br s, 1H, H-14), 3.42 (br s, 1H, OH), 3.60 and 3.65 (both
s, 6H, 2CH3), 4.20 (br s, 1H, H-15), 5.69 (br s, 1H, H-19). 13C NMR
(75.5 MHz, CDCl3): 15.3, 16.6, 16.9, 20.2, 20.8, 21.7, 26.3, 33.4,
33.6, 34.2 (C-17), 34.3 (C-16), 36.6, 37.1, 37.9, 39.8, 40.6, 47.0,
49.3, 51.7, 52.0, 53.4, 60.0, 60.1, 74.9 (C-15), 127.2 (C-19), 147.7
(C-18), 177.48 (C-26), 179.2 (C-25). Anal. calcd for: C28H42O5 C,
73.3; H, 9.2. Found: C, 73.1; H, 9.7.
respectively. It is established that the test compounds at 10
concentration have no effect on DNA replication of hepatitis B virus
(HBV), but the compound 13 has low toxicity (CC50 P100 M).
lM
l
Compounds 25, 30 showed activity on the replication of the nucleic
acid HCV, but were proved toxic in the investigated concentration.
Percent at inhibition of nucleic acid replication of hepatitis C virus
(HCV) for these compounds in a concentration of 20 lM was 96.6%
and 97.9%, and the cytotoxicity (percentage of live cells)—6.4% and
0.2%, the selectivity index was SI < 1. Compounds 15, 16 b 34
showed a low toxicity and a pronounced inhibitory effect on the
replication of the nucleic acid HCV (60.8, 68.4, 97.3% respectively,
SI > 1), and can be recommended for further study of the activity
of different compounds concentrations.
4.2.2. Methyl 1-(2-cyanoethoxy)-13-isopropyl-7,10a-dimethyl-
4-oxohexadecahydro-1H-4b,12-ethenochrysene-7-carboxylate
(methyl 1-cyanoethyl-dihydroquinopimarate) 21
A mixture of 1 mmol (0.43 g) of the compound 17, 21.5 mmol
(1.4 ml) of acrylonitrile, 0.5 mmol (0.11 g) of BTEAC, and 0.5 ml
of 30% KOH in 15 mL of dioxane was stirred for 2 h at room tem-
perature. The mixture was poured into a mixture of ice with HCl,
the precipitate was filtered off, washed with water until neutral
washings, air dried, and extracted with methylene chloride
(3 ꢀ 80 mL) with heating, the solution was filtered, and the filtrate
was evaporated. The residue was purified by Al2O3 column chro-
3. Conclusions
Thus, a number of maleopimaric and quinopimaric derivatives
modified in carboxyl and carbonyl groups and ring E are synthesized
and evaluated as potential antiviral agents. We observed the follow-
ing structure–activity relationship: the modifications of levopimaric
acid diene adducts does not give rise to activity against viral
respiratory infections. Only dihydroquinopimaric acid and
50-caprolactam—a product of Beckmann rearrangement of 1b-dihy-
droquinopimaric acid monooxime—have minimal activity against
influenza virus type B and SARS respectively. At the same time, the
functionalization of the carboxyl group at C-20 dihydroquinopi-
matography with methylene chloride as the eluent. Yield 0.19 g
20
(40%), mp 180–182 °C,
[
a]
+75 (c 0.01, CHCl3). 1H NMR
D
(300 MHz, CDCl3): 0.55 (s, 3H, CH3), 0.81–0.95 (m, 2H), 1.07 and
1.12 (both d, 6H, J = 6.9 Hz, 2CH3), 1.15 (s, 3H, CH3), 1.35–1.90
(m, 15H), 2.20–2.39 (m, 6H), 2.78–3.09 (m, 2H), 3.51 (m, 2H,
CH2), 3.69 (s, 1H, H-21), 3.80 (m, 2H, CH2), 5.51 (br s, 1H, H-14).
13C NMR (75.5 MHz, CDCl3): 15.9, 16.8, 17.0, 19.3 (CH2), 19.6,
21.4, 21.8, 23.9, 29.9, 32.9, 34.4, 35.2, 36.3, 36.6, 37.9, 38.1, 40.5,
44.9, 47.2, 49.4, 51.9, 55.3, 62.2 (CH2), 63.1, 76.2 (C-1), 117.8
(CN), 123.5 (C-14), 148.4 (C-13), 179.3 (C-20), 212.9 (C-4). Anal.
calcd for: C30H43NO4 C, 74.8; H, 9.0; N, 2.9. Found: C, 75.1; H,
9.5; N, 2.8.
maric acid with introduction in diterpenoid structure of L-alanine
fragment leads to high activity against papilloma virus and hepatitis
C virus. The functionalization of the maleopimaric acid derivatives
carboxyl group does not have an antiviral effect. The products of
maleopimaric and dihydroquinopimaric acids oxidation reactions
and the mentioned 1b-hydroxy-50-caprolactam has also show activ-
ity against papilloma and hepatitis C viruses. The received results
encourage us to continue research on the synthesis of new deriva-
tives levopimaric acid to obtain new biologically active compounds.
4.2.3. Methyl 13-isopropyl-7,10a-dimethyl-1-{[(2E)-3-phenylpr-
op-2-enoyl]oxy}-4-{[(2Z)-3-phenylprop-2-enoyl]oxy}hexadeca-
hydro-1H-4b,12-ethenochrysene-7-carboxylate (methyl 1,4–di-
cynnamoyl-dihydroquinopimarate) 27
4. Experimental
4.1. Materials and methods
A solution of 1 mmol (0.43 g) of compound 18 in 15 ml of anhy-
drous pyridine was added 4 mmol (0.67 g) of cinnamoyl chloride
and refluxed for 6 h. The mixture was poured into 20 ml of a 5%
solution of HCl, and the precipitate was filtered, washed and air
dried. The residue was purified by Al2O3 column chromatography
The 1H and 13C NMR spectra (d, ppm; J, Hz) were recorded on a
Bruker AM-300 (Germany) spectrometer (300.13 and 75.5 MHz,
respectively) in a CDCl3 solution using tetramethylsilane as the
internal standard. Melting points were determined on a Boetius
apparatus. Optical rotations were measured on a Perkin Elmer
MC polarimeter (Switzerland) in a 1 dm tube. TLC analysis was car-
ried out on Sorbfil plates (Sorbpolimer, Russia) using chloroform–
ethyl acetate (40:3) as the solvent system, detection with a 10%
solution of sulfuric acid (2–3 min at 100–120 °C).
with methylene chloride as the eluent. Yield 0.42 g (61%), mp
20
105–107 °C, [
a]
+25 (c 0.01, CHCl3). 1H NMR (300 MHz, CDCl3):
D
0.63 (s, 3H, CH3), 0.89–1.08 (m, 2H), 1.09 and 1.13 (both d, 6H,
J = 6.9 Hz, 2CH3), 1.15 (s, 3H, CH3), 1.19–1.79 (m, 12H), 1.91–2.50
(m, 6H), 2.78 (dt, 1H, J1 = 4.4 Hz, J2 = 3.7 Hz, J3 = 13.4 Hz, H-1a),
3.20 (br s, 1H, H-12), 3.67 (s, 3H, H-21), 5.10 (m, 2H, H-1, H-4),
5.61 (br s, 1H, H-14), 6.41 and 6.83 (both d, 2H, J = 15.9 Hz, 2CH),
7.26–7.81 (m, 12H, H-Ar). 13C NMR (75.5 MHz, CDCl3): 15.7, 16.8,
17.0, 19.6, 20.0, 21.3, 30.2, 31.9, 32.9, 35.2, 35.5, 35.9, 36.6, 37.8,
38.2, 40.2, 45.1, 47.1, 49.4, 51.8, 54.6, 61.8, 74.3 (C-4), 77.6 (C-1),
117.9 (CH), 118.7 (CH), 124.3 (C-14), 127.6 (C-Ar), 128.0 (C-Ar),
For the synthesis of maleopimaric acid 131 and quinopimaric
acid 332 pine resin Pinus silvestris containing about 25% levopimaric
acid was used. Compounds 2,34 4,32 5–8,33 10,31 11,22 12,26 13,22
14,33 15,22 16,30 17–20,35 22–26,35 29,32 30,36 32,37 33,22 34,37
3622 were obtained according to the methods described previously.
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006

E. V. Tretyakova et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
7
128.1 (C-Ar), 128.3 (C-Ar), 128.6 (C-Ar), 128.9 (C-Ar), 129.3
(C-Ar), 129.9 (C-Ar), 130.3 (C-Ar), 131.0 (C-Ar), 142.1 (C-Ar),
142.9 (C-Ar), 145.2 (CH), 145.6 (CH), 147.8 (C-13), 170.0 (OC@O),
171.9 (OC@O), 179.2 (C-20). Anal. calcd for: C45H54O6 C, 78.2; H,
7.9. Found: C, 77.8; H, 7.6.
(m, 17H), 2.01 (s, 3H, OCH3), 2.10–2.24 (m, 6H), 3.05 (br s, 1H, H-
12), 3.65 (s, 3H, H-21), 4.05 (br s, 1H, H-1), 4. 50 (br s, 1H, H-4).
13C NMR (75.5 MHz, CDCl3): 15.5, 16.6, 16.9, 17.0, 19.2, 20.7, 21.4
(CH3), 21.8, 26.7, 33.7, 35.0, 36.0, 36.7, 37.3, 38.5, 38.8, 39.2, 41.0
(C-14), 41.1, 47.1, 50.0, 51.1 (C-21), 51.6, 55.1, 70.9 (C-4), 75.8
(C-1), 86.6 (C-13), 170.4 (OAc), 177.8 (C-20). Anal. calcd for:
4.2.4. 13-Isopropyl-7,10a-dimethyl-7-({[(2E)-3-phenylprop-2-
enoyl]oxy}methyl)hexa-decahydro-1H-4b,12-ethenochrysene-
1,4-diyl (2E,20Z)bis(3-phenylacrylate) (1,4,20-tricynnamoyl-
dihydroquinopimarate) 28
C29H44O5 C, 73.7; H, 9.4. Found: C, 73.3; H, 8.6.
4.3. Evaluation of antiviral activity
A solution of 1 mmol (0.40 g) of compound 19 in 15 ml of anhy-
drous pyridine was added 6 mmol (1.00 g) of cinnamoyl chloride
and refluxed for 12 h. The mixture was poured into 20 ml of a 5%
solution of HCl, and the precipitate was filtered, washed and air
dried. The residue was purified by Al2O3 column chromatography
The National Institute of Allergy and Infectious Diseases (NIAID)
established the AACF under a contract with Southern Research
Institute. The NIAID, through the AACF, provides free and
confidential services for suppliers, who are interested in submit-
ting compounds to be evaluated for antiviral activity. Tested com-
pounds were delivered in standard DMSO solutions. The methods
applied for the different assays can be found at the URL via the
internet at http://niaid-aacf.org.
with methylene chloride as the eluent. Yield 0.36 g (45%), mp
20
125–127 °C, [
a]
+15 (c 0.01, CHCl3). 1H NMR (300 MHz, CDCl3):
D
0.63 (s, 3H, CH3), 0.89–1.08 (m, 2H), 1.09 and 1.13 (both d, 6H,
J = 6.9 Hz, 2CH3), 1.15 (s, 3H, CH3), 1.19–1.79 (m, 12H), 1.91–2.50
(m, 7H), 3.20 (br s, 1H, H-12), 5.03 (m, 2H, CH2), 5.10 (m, 2H,
H-1, H-4), 5.61 (br s, 1H, H-14), 6.41 and 6.53 and 6.82 (all d, 3H,
J = 15.9 Hz, 3CH), 7.26–7.81 (m, 18H, H-Ar). 13C NMR (75.5 MHz,
CDCl3): 15.0, 16.8, 17.0, 19.3, 20.0, 22.9, 30.7, 31.9, 32.5, 35.2,
35.8, 36.1, 37.8, 38.1, 40.7, 45.1, 47.1, 49.3, 51.8, 54.2, 61.8, 73.1
(C-20), 74.3 (C-4), 77.6 (C-1), 117.6 (CH), 117.9 (CH), 118.7 (CH),
124.3 (C-14), 127.5 (C-Ar), 127.8 (C-Ar), 127.9 (C-Ar), 128.0
(C-Ar), 128.1 (C-Ar), 128.3 (C-Ar), 128.4 (C-Ar), 128.6 (C-Ar),
128.9 (C-Ar), 129.2 (C-Ar), 129.5 (C-Ar), 129.8 (C-Ar), 130.0
(C-Ar), 130.5 (C-Ar), 131.0 (C-Ar), 142.1 (C-Ar), 142.5 (C-Ar),
142.9 (C-Ar), 145.0 (CH), 145.2 (CH), 145.6 (CH), 147.8 (C-13),
170.0 (OC@O), 170.2 (OC@O), 171.9 (OC@O). Anal. calcd for:
Primary antiviral assay was performed on a respiratory viruses
panel (Flu A (H1N1), Flu A (H3N2), Flu A (H5N1), Flu B, rhinovirus
type 2, adenovirus and SARS).39
Primary anti-HPV assay was determined using standard AACF
screening assay protocols.40
Primary Anti-HBV assay and toxicity against confluent 2.2.15 cells
were determined by the published procedure of Korba and Gerin.41
Primary HCV RNA replicon assay was examined by the effect of
drugs added in triplicate at a single high-test concentration of
20 l
M on HCV RNA-derived LUC activity and cytotoxicity.42
Acknowledgments
C
53H60O6 C, 80.3; H, 7.6. Found: C, 79.8; H, 7.6.
This work was supported by the Russian Foundation for Basic
Research (Project No. 14-03-97046 r_Povolgye_a) and in part by
a Grant of the President of the Russian Federation for State Support
of Leading Scientific Schools (NSH-2625.2014.3). We thank
National Institute of Allergy and Infectious Diseases (NIAID, USA)
for screening of antiviral activities of compounds 1–36.
4.2.5. Methyl (4E)-4-(hydroxyimino)-13-isopropyl-7,10a-dimeth-
yl-1-oxohexadecahydro-1H-4b,12-ethenochrysene-7-carboxyla-
te (methyl 4-oxime-dihydroquinopimarate) 31
A solution of 1 mmol (0.47 g) of the compound 30 in 20 ml of
acetone was added 1 mL HCl and the reaction mixture was refluxed
for 3 h. The mixture was poured into a 20 ml of a 5% solution of
NaHCO3, the precipitate was filtered, washed with water and air
dried. The residue was purified by Al2O3 column chromatography
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmc.2015.09.006.
with chloroform as the eluent. Yield 0.38 g (80%), mp 121–
123 °C, [
a]
+45.5° (c 1.0, CHCl3). 1H NMR (300 MHz, CDCl3):
20
D
0.56 (s, 3H, CH3), 0.95 and 0.99 (both d, 6H, J = 6.9 Hz, 2CH3),
1.13 (s, 3H, CH3), 1.30–1.79 (m, 12H), 1.80–2.78 (m, 9H), 3.05 (br
s, 1H, H-12), 3.65 (s, 3H, H-21), 5.51 (br s, 1H, H-14), 6.05 (d, 1H,
J = 4.2 Hz, NOH). 13C NMR (75.5 MHz, CDCl3): 16.1, 16.5, 16.9,
18.6, 19.6, 20.6, 21.8, 27.3, 32.6, 35.4, 36.6, 37.4, 37.8, 38.5, 39.3,
40.9, 47.1, 49.6, 51.6, 52.1, 54.6, 56.4, 126.0 (C-14), 147.9 (C-13),
158.5 (C-4), 179.1 (C-20), 211.6 (C-1). Anal. calcd for: C27H39NO4
C, 73.4; H, 8.9; N, 3.2. Found: C, 73.0; H, 7.6; N, 2.8.
References and notes
1. Martin, D.; Tholl, D.; Gershenzon, J.; Bohlmann, J. Plant. Physiol. 2002, 129, 1003.
2. Ulubelen, A.; Sonmez, U.; Topcu, G.; Bozok-Johansson, C. Phytochemistry 1996,
42, 145.
3. Batista, O.; Simoes, M. F.; Duarte, A.; Valdivia, M. L.; De La Torre, M. C.;
Rodriguez, B. Phytochemistry 1995, 38, 167.
4. Gonzaalez, M. A.; Zaragoza, R. J. J. Nat. Prod. 2014, 9, 2114.
5. Achenbach, H.; Walbel, R.; Nkunya, M. H. H.; Weenen, H. Phytochemistry 1992,
31, 3781.
6. Ito, Y.; Shibata, K.; Hongo, A.; Kinoshita, M. Eur. J. Pharm. 1998, 345, 193.
7. Machumi, F.; Samoylenko, V.; Yenesew, A.; Derese, S.; Midiwo, J. O.; Wiggers, F.
T.; Jacob, M. R.; Tekwani, B. L.; Khan, S. I.; Walker, L. A.; Muhammad, I. Nat. Prod.
Commun. 2010, 6, 853.
8. Nakatani, N.; Inatani, R. Agric. Biol. Chem. 1984, 48, 2081.
9. Marrero, J. G.; Andres, L. S.; Luis, J. G. J. Nat. Prod. 2002, 65, 986.
10. Lin, Ch.-H.; Chuang, H.-Sh. US patent 2004/0063788A1, 2004.
11. Iwamoto, M.; Ohtsu, H.; Tokuda, H.; Nishino, H.; Matsunago, Sh.; Tanaka, R.
Bioorg. Med. Chem. 1911, 2001, 9.
12. Mauldin, S. C.; Monroe, J. E. US patent 6,180,815 B1, 2001.
13. Gigante, B.; Santos, C.; Silva, A. M.; Curto, M. J. M.; Nascimento, M. S. J.; Pinto,
E.; Duarte, M. P.; Laires, A.; Rueff, J.; Goncalves, J.; Pegado, M. I.; Valdeira, M. L.
Bioorg. Med. Chem. 2003, 11, 1631.
14. Gonzales, M. A.; Correa-Royero, J.; Agudelo, L.; Mesa, A.; Betancur-Galvis, L. Eur.
J. Med. Chem. 2009, 44, 2468.
4.2.6. Methyl 1-(acetyloxy)-5-isopropyl-6b,10-dimethyloctade-
cahydro-5,12a-methanochryseno[1,12-bc]furan-10-carboxylate
(methyl 1,13-epoxy-4-acetoxy-dihydroquinopimarate) 35
A solution of 1 mmol (0.45 g) of the compound 7 in 10 ml MeOH
was added portionwise 5 mmol (0.2 g) NaBH4. The reaction mass
was refluxed for 2 h, poured into 20 ml of 5% HCl and the precipi-
tate was filtered off, washed with water and air dried. The residue
was dissolved in 10 ml of pyridine was added 0.3 ml of acetic anhy-
dride and allowed to stand for 15 h. The reaction mixture was
poured into 50 mL of 5% HCl solution, cooled to 0 °C, the precipitate
was filtered off, washed with water, dried and recrystallized from
20
15. Fonseca, T.; Gigante, B.; Marques, M. M.; Gilchrist, T. L.; De Clercq, E. Bioorg.
Med. Chem. 2004, 12, 103.
16. Ohtsu, H.; Tanak, R.; In, Y.; Matsunaga, S.; Tokuda, H.; Nishino, H. Planta Med.
2001, 67, 55.
methanol. Yield 0.37 g (79%), mp 125–128 °C, [
a]
D
+25.5° (c 0.01,
CHCl3). 1H NMR (300 MHz, CDCl3): 0.84 (s, 3H, CH3), 1.02 and
1.07 (both d, 6H, J = 7.1 Hz, 2CH3), 1.28 (s, 3H, CH3), 1.32–1.76
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006

8
E. V. Tretyakova et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
17. Halbrook, N. J.; Lawrence, R. V. J. Am. Chem. Soc. 1958, 80, 368.
18. Ayer, W. A.; McDonald, C. E.; Stothers, J. B. Can. J. Chem. 1963, 41, 1113.
19. Halbrook, N. J.; Lawrence, R. V.; Dressler, R. L.; Blackstone, R. C.; Herz, W. J. Org.
Chem. 1964, 29, 1017.
29. Kazakova, O. B.; Smirnova, I. E.; Tkhi Tkhu, H. Do.; Nguen, Tkhankh Tra;
Apryshko, G. N.; Zhukova, O. S.; Medvedeva, N.; Nazyrov, T. I.; Tret’yakova, E.
V.; Chudov, I. V.; Ismagilova, A. F.; Suponitsky, K. Yu.; Kazakov, D. V.; Safarov, F.
E.; Tolstikov, G. A. Russ. J. Bioorg. Chem. 2013, 39, 202.
20. Flekhter, O. B.; Tret’yakova, E. V.; Galin, F. Z.; Karachurina, L. T.; Spirikhin, L. V.;
Zarudii, F. S.; Tolstikov, G. A. Russ. Pharm. Chem. J. 2002, 8, 428.
21. Kazakova, O. B.; Tret’yakova, E. V.; Smirnova, I. E.; Spirikhin, L. V.; Tolstikov, G. A.;
Chudov, I. V.; Bazekin, G. V.; Ismagilova, A. F. Russ. J. Bioorg. Chem. 2010, 36, 257.
22. Kazakova, O. B.; Tret’yakova, E. V.; Kukovinets, O. S.; Tolstikov, G. A.; Nazyrov,
T. I.; Chudov, I. V.; Ismagilova, A. F. Russ. J. Bioorg. Chem. 2010, 36, 762.
23. Flekhter, O. B.; Tret’yakova, E. V.; Makara, N. S.; Gabdrakhmanova, S. F.;
Baschenko, N. Zh.; Galin, F. Z.; Zarudii, F. S.; Tolstikov, G. A. Russ. Pharm. Chem. J.
2003, 37, 142.
30. Kazakova, O. B.; Tret’yakova, E. V.; Smirnova, I. E.; Nazyrov, T. I.; Kukovinets, O.
S.; Tolstikov, G. A.; Suponitsky, K. Yu. Nat. Prod. Commun. 2013, 3, 293.
31. Zalkov, L. U.; Ford, R. A.; Cutney, J. P. J. Org. Chem. 1962, 27, 3535.
32. Herz, W.; Blackstone, R. C.; Nair, M. G. J. Org. Chem. 1967, 32, 2992.
33. Herz, W.; Nair, M. G. J. Org. Chem. 1969, 34, 4016.
34. Ayer, W. A.; McDonald, C. E. Can. J. Chem. 1965, 5, 1429.
35. Smirnova, I. E.; Tret’yakova, E. V.; Flekhter, O. B.; Spirikhin, L. V.; Galin, F. Z.;
Tolstikov, G. A.; Starikova, Z. A.; Korlyukov, A. A. Russ. J. Org. Chem. 2008, 44,
1598.
24. Tret’yakova, E. V.; Smirnova, I. E.; Kazakova, O. B.; Tolstikov, G. A.; Yavorskaya,
N. P.; Golubeva, I. S.; Pugacheva, R. B.; Apryshko, G. N.; Poroikov, V. V. Bioorg.
Med. Chem. 2014, 22, 6481.
25. Yao, G.; Ye, M.; Huang, R.; Li, Y.; Zhu, Y.; Pan, Y.; Liao, Zh.; Wang, H. Bioorg. Med.
Chem. Lett. 2013, 23, 6755.
36. Smirnova, I. E.; Tret’yakova, E. V.; Kazakova, O. B.; Starikova, Z. A.; Fedyanin, I.
V. J. Struct. Chem. 2009, 50, 378.
37. Smirnova, I. E.; Tret’yakova, E. V.; Kazakova, O. B.; Starikova, Z. A. J. Struct.
Chem. 2009, 50, 381.
38. http://niaid.nih.gov.
26. Flekhter, O. B.; Smirnova, I. E.; Tret’yakova, E. V.; Tolstikov, G. A.; Savinov, O. V.;
Boreko, E. I. Russ. J. Bioorg. Chem. 2009, 35, 385.
27. Vafina, G. F.; Uzbekov, A. R.; Zarubaev, V. V.; Karpinskaya, L. A.; Shtro, A. A.;
Yunusov, M. S. Chem. Nat. Comp. 2015, 1, 103.
39. Sidwell, R. W.; Smee, D. F. Antiviral Res. 2000, 48, 1.
40. Chow, L. T.; Broker, T. R. Clin. Dermatol. 1997, 15, 217.
41. Korba, B. E.; Gerin, J. L. Antiviral Res. 1992, 19, 55.
42. Krieger, N.; Lohmann, V.; Bartenschlager, R. J. Virol. 2001, 75, 4614.
28. Kazakova, O. B.; Tret’yakova, E. V.; Kukovinets, O. S.; Abdrakhmanova, A. R.;
Kabalnova, N. N.; Kazakov, D. V.; Tolstikov, G. A.; Gubaidullin, A. T. Tetrahedron
Lett. 1832, 2010, 51.
Please cite this article in press as: Tretyakova, E. V.; et al. Bioorg. Med. Chem. (2015), http://dx.doi.org/10.1016/j.bmc.2015.09.006