Synthesis of 1,2-azole derivatives on the basis of α,β-unsaturated triterpene aldehydes

Article abstract of DOI:10.1007/s10593-020-02817-y

[Figure not available: see fulltext.] α,β-Unsaturated lupane and 19β,28-epoxy-18α-oleanane aldehydes were used in the synthesis of triterpenoids bearing substituted 1,2-azole moieties (1-acetyl-3-methyl-4,5-dihydro-1H-pyrazole and 3-methyl-4,5-dihydroisoxazole) at the rings А and Е. The route of synthesis for these 1,2-azole derivatives of triterpenes included an aldol condensation of α,β-unsaturated aldehydes with acetone, the products of which (α,β-unsaturated methyl ketone and β-hydroxy ketone) underwent a further cycloaddition reaction with acetylhydrazide and hydroxylamine. Cytotoxic activity studies of the synthesized compounds against seven cancer cell lines (Hep-2, HCT116, MS, RD TE32, A549, MCF-7, and PC-3) showed that the highest cytotoxicity (IC₅₀ 0.66–11.97 μM) against all tested cell lines was exihbited by 19β,28-epoxy-18α-oleanane aldehyde and the products of its condensation reactions with acetone and acetylhydrazide.

Full text of DOI:10.1007/s10593-020-02817-y

DOI 10.1007/s10593-020-02817-y
Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
Synthesis of 1,2-azole derivatives on the basis of α,β-unsaturated
triterpene aldehydes
Mikhail A. Nazarov1, Irina A. Tolmacheva1*, Daria V. Eroshenko1,
Olga A. Maiorova1, Maksim V. Dmitriev2, Victoria V. Grishko1
1 Institute of Technical Chemistry, Ural Branch of the Russian Academy of Sciences,
3 Akademika Koroleva St., Perm 614013, Russia; е-mail: tolmair@gmail.com
2 Perm State National Research University,
15 Bukireva St., Perm 614990, Russia
Submitted December 15, 2019
Accepted after revision June 26, 2020
Translated from Khimiya Geterotsiklicheskikh Soedinenii,
2020, 56(10), 1321–1328
α,β-Unsaturated lupane and 19β,28-epoxy-18α-oleanane aldehydes were used in the synthesis of triterpenoids bearing substituted
1,2-azole moieties (1-acetyl-3-methyl-4,5-dihydro-1H-pyrazole and 3-methyl-4,5-dihydroisoxazole) at the rings А and Е. The route of
synthesis for these 1,2-azole derivatives of triterpenes included an aldol condensation of α,β-unsaturated aldehydes with acetone, the
products of which (α,β-unsaturated methyl ketone and β-hydroxy ketone) underwent a further cycloaddition reaction with
acetylhydrazide and hydroxylamine. Cytotoxic activity studies of the synthesized compounds against seven cancer cell lines (Hep-2,
HCT116, MS, RD TE32, A549, MCF-7, and PC-3) showed that the highest cytotoxicity (IC50 0.66–11.97 µM) against all tested cell lines
was exihbited by 19β,28-epoxy-18α-oleanane aldehyde and the products of its condensation reactions with acetone and acetylhydrazide.
Keywords: 1,2-azoles, betulin, oxazoline, pyrazoline, triterpenoids, α,β-unsaturated aldehydes, aldol condensation, cytotoxic activity.
Pentacyclic triterpenoids offer a great therapeutic
potential and synthetic utility, and have been used for a
long time by medicinal chemistry researchers as promising
structural motifs for the design of compounds with high
biological activity.1–5 The introduction of nitrogen-, sulfur-
or oxygen-containing heterocyclic substituents into the
triterpene ring system can increase its biological activity
and improve bioavailability.6–10 Heterocyclic modifications
of triterpenoids are often accomplished via classical
synthetic reactions and reactive functional groups can be
easily used for the purpose of adding a heterocyclic
substituent to a triterpenoid molecule (for example, ОН,
>С=О, СООН, С=С etc.),10–15 or else new reactive sites
can be created in order to achieve heterocyclization.16–21
Despite the great number of semisynthetic triterpenoids
featuring various heterocyclic modifications of their
molecular framework, it is still important to continue the
development of new, practical, and effective methods for
the synthesis of heterocycles on the basis of natural
compounds.
Triterpene oxo derivatives, in particular aldehydes, are
readily available, reactive substrates for the preparation of
carbo- and heterocyclic structures with antiviral and cyto-
toxic activity, which we have demonstrated repeatedly with
the examples of А-secotriterpene compounds bearing
aldehyde and methyl ketone functionalities in the А-seco
moiety.22–26 Thus, by heterocyclization of the intermediate
compound – the acetylhydrazone of 1-cyano-2,3-secolupane
aldehyde, the cytotoxic (R)-1,3,4-oxadiazoline was obtained,
which showed a proapoptotic effect against tumor cells.22
The goal of the current work was to study the possibility
of synthesizing triterpene derivatives decorated with
pyrazoline and isoxazoline rings by starting from α,β-un-
saturated lupane and 18α-oleanane aldehydes.
0009-3122/20/56(10)-1321©2020 Springer Science+Business Media, LLC
1321

Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
Scheme 1
30Me Me29
CH2
H
Me Me
O
20
21
19
18
Me
O
H
12
28
H
1. HCOOH
H
HCO2Et
NaH
22
11
25
26
2. KOH, EtOH
13
14
17
OH
Me Me
H
9
31
Me Me
H
Me Me
1
16
2
3. CrO3, H2SO4
Me2CO
1
PhH,
52%
10H
8 Me15
2
3
HO
5
H
H
Me
H
Me
27
3
4
7
O
75%
6
HO
O
H
H
Me
Me
Me
Me Me
Me
2
23
1
24
3
Me
Me
Me
Me
O
O
H
H
O
OH
Me2CO, NaOH
H2SeO3
31
Me Me
1
Me Me
1
H
H
2
2
PhH, H2O, rt
40%
1,4-dioxane
, 4 h
Me
31
O
33
32
H
Me
Me
3
3
H
34
80%
O
O
H
H
Me
4
Me
Me
Me
NaOH
6
Me2CO, H2O
rt, 6 h
1. NH2NHAc
– H2O
AcOH, EtOH,
2. Py, (Ac)2O, rt
or
40%
92%
Me
Me
NH2NHAc
AcOH,
O
H
Me
Me
O
O
1
Me Me
H
H
2
3
Me
31
33
32
H
Me
31
34
H
1
Me Me
H
2
Me
N
O
N
H
H
Me
3
Me
Me
O
O
7
H
Me
Me
5
Allobetulone 2 was obtained on the basis of betulin 1
and further converted into 2-hydroxymethylidene-19β,28-
epoxy-18α-oleanane derivative 3,27 the oxidation of which
with Н2SeO3 in 1,4-dioxane medium led to our previously
described product – 2-formyl-19β,28-epoxy-18α-olean-1(2)-en-
3-one (4)28 (Scheme 1). The structure of aldehyde 4 was
additionally confirmed by the X-ray structural analysis
(Fig. 1).
Compound 4 crystallized in a noncentrosymmetric space
group of monoclinic syngony. Molecular geometry
verification using Mercury Mogul Geometry Check soft-
ware29 showed that all bond lengths and valence angles had
values characteristic for the respective functionalities. The
cyclohexenone ring А contains the C(4) and C(5) atoms in
a twist boat conformation, which deviate from the plane
defined by C(10)C(1)C(2)C(3) atoms by 0.59 and 0.98 Å,
respectively. Despite the fact that the formyl substituent
and the ketone carbonyl group are rotated at small angles
relative to the C(1)=C(2) multiple bond (the torsion
angles are the following: O(3)C(31)C(2)C(1) 10.7(5)°,
O(2)C(3)C(2)C(1) 151.6(3)°), the conjugation between
them is not strong. The 1.330(4) Å length of the C(1)=C(2)
bond is characteristic for a regular localized double bond,
Figure 1. The molecular structure of compound 4 with atoms
represented by thermal vibration ellipsoids of 50% probability.
localized ordinary C–C bond. There is no specific
shortened contacts in the crystal structure.
The cycloaddition reactions between α,β-unsaturated
carbonyl compounds and hydrazines have been widely
used for the preparation of substituted 2-pyrazolines.30 For
example, various pyrazoline derivatives of steroids were
obtained via a cycloaddition reaction of α,β-unsaturated
ketones and acetic hydrazide in AcOH.31,32 Two schemes
have been proposed for the synthesis of pyrazoline
derivatives of steroids. A two-step synthesis including
1) condensation of α,β-unsaturated steroid ketone with
acetic hydrazide in EtOH under the conditions of acidic
catalysis and 2) further cyclization of the formed
while
the
lengths
of
the
C(2)–C(3)
and
C(2)–C(31) bonds (1.478(4) and 1.483(5) Å, respectively)
are insignificantly shortened compared to the length of a
1322

Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
hydrazone, resulting in the formation of a pyrazoline ring,
selection of compound 6 or 7 as starting material, was
formed as a 7:3 mixture of diastereomers according to its
1Н NMR spectral data, and this mixture could not be
was performed at room temperature in a pyridine – acetic
anhydride mixture.31 In addition, a heterocyclization
reaction of α,β-unsaturated ketone in АсОН was performed
without isolation of the intermediate hydrazone.32
1
separated chromatographically. Н NMR spectrum of the
isomer mixture 8 contained signals that were assigned to
the pyrazoline ring protons: the signals of 4'-CН2 protons in
the range of 2.41–2.58 ppm, 4'-CН2 proton signals in the
range of 3.11–3.19 ppm, and 5'-CН proton signals in the
range of 5.00–5.01 ppm.
It was expected that the use of the aforementioned
reaction conditions for the treatment of 19β,28-epoxy-18α-
oleanane aldehyde 4 with acetic hydrazides should lead to
the formation of pyrazoline that would be annulated at the
С(1)–С(2) bond. However, under all of our explored
reaction conditions, only the formation of the
corresponding acetylhydrazone 528 was observed, without
its heterocyclization into pyrazoline (Scheme 1).
Scheme 3
Since aldehyde 4 did not contain protons at the α-carbon
atom relative to the aldehyde group, we used it in the aldol
condensation reaction in the role of a carbonyl component
for the introduction of an α,β-unsaturated methyl ketone
moiety in the triterpene molecule. The condensation of
aldehyde 4 with Me2CO proceeded at room temperature in
2:1 PhH–Me2CO mixture in the presence of NaOH, leading
to the formation of β-hydroxy ketone 6 in 40% yield. The
reaction progress was controlled by performing TLC
analysis. The aldol reaction was stopped at the first signs of
the presence of crotonic derivative 7. The use of only
Ме2СО as solvent led directly to α,β-unsaturated methyl
ketone 7. Aldol 6 was formed as a 7:3 diastereomer
Heating β-hydroxy ketone 6 with hydroxylamine
hydrochloride and AcONa at reflux temperature in EtOH
provided isoxazoline 9 in 82% yield as a 7:3 mixture of
diastereomers. 1Н NMR spectrum of product 9 contained a
singlet signal of methyl group protons (at 1.90 ppm) and
the signals of epimeric protons belonging to the
heterocyclic moiety: 4'-СН2 protons (2.32–2.34 and 2.47–
2.61 ppm), as well as the 5'-СН protons (4.59–4.77 ppm).
Taking into account the observation that pyrazoline 8
was formed in the highest yield from β-hydroxy ketone 6,
the targeted aldol condensation reaction of lupane aldehyde
1133 (prepared from betulin 3,28-diacetate 1033) with
Ме2СО was performed under the optimal conditions for the
synthesis of β-hydroxy ketone 6 (Scheme 4). Aldol 12 thus
obtained was a 6:4 mixture of diastereomers, the ratio of
1
mixture, as indicated by the proton signal integrals in H
NMR spectrum: 1-СН (7.18 and 7.20 ppm), 31-СН (4.73
and 4.89 ppm), and 34-СН3 (2.17 and 2.18 ppm).
1H NMR spectrum of α,β-unsaturated methyl ketone 7
showed that the 33-CH3 protons of the methyl ketone
moiety appeared as a singlet signal at 2.29 ppm, while two
doublets in the region of 6.68 and 7.20 ppm were assigned
to the olefinic protons of the С(31)−С(32) bond, with
16 Hz spin-spin coupling constant pointing to the E-confi-
guration of double bond. 13С NMR spectrum of compound
7 showed the signals of sp2-hybridized carbon atoms in the
range of 128.8–161.2 ppm, as well as the C-3 and C-33
carbonyl carbon atoms at 203.6 and 198.8 ppm,
respectively.
1
which was determined from the ratio of H NMR signal
integrals for the 29-CН2 group in the range of 4.91–
5.09 ppm. During the synthesis of lupane pyrazoline
derivative, compound 12 was refluxed with acetic hydrazide
in AcOH for 4 h. TLC analysis indicated that the reaction
mixture contained two products 13a and 13b (64% yield)
with very close Rf values in a 6:4 ratio, which was
In contrast to aldehyde 4, the use of α,β-unsaturated
methyl ketone 7 in the reaction with acetic hydrazide was
found to be more successful and led to pyrazoline 8, albeit
in rather low yields – 15% or 30% (Scheme 2). At the same
time, heating β-hydroxy ketone 6 at reflux temperature in
АсОН with acetic hydrazide allowed to obtain pyrazoline 8
in 76% yield (Scheme 3). Pyrazoline 8, regardless of the
1
determined on the basis of H NMR spectrum (Scheme 4).
Only isomer 13a was successfully isolated from the mixture
of products 13a,b and characterized as an individual
compound.
1
The analysis of H NMR spectrum of compound 13а
Scheme 2
allowed to assign two double doublet signals at 2.56 and
3.06 ppm to the 4'-СH2 group protons, a double doublet at
4.78 ppm was assigned to the 5'-СH proton, while the two
singlet signals at 2.00 and 2.25 ppm belonged to the methyl
group at the С-3' carbon atom and the N-acetyl group. The
characteristic 13С NMR signals of the pyrazoline ring in
compound 13а were observed at 43.8 (C-4'), 61.0 (C-5'),
155.2 (C-3'), and 168.4 ppm (C-6'). The structural features
of the heterocyclic system in compound 13а were proved
conclusively on the basis of two-dimensional COSY,
1
1H–13C HMBC, H–13C HSQC, and NOESY experiments.
1323

Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
Scheme 4
The proton signal assignments for compound 13а were
confirmed by using its COSY spectrum that showed
coupling between the 4'-СН2 and 5'-СН protons in the
pyrazoline ring. The most informative cross peaks in
1H–13C HMBC spectrum (Fig. 2) were the following:
between the proton signals of 29-СН2 group and the signals
of С-19 and С-5' carbon atoms, between the signals of
4'-СН and 5'-СН protons and the signals of С-20 and С-3'
carbon atoms, between the signal of 7'-СН3 protons and the
signal of С-6' carbon atom, and between the signal of
8'-СН3 protons and the signal of С-3' carbon atom. A
NOESY experiment was used for determining the relative
configuration of the С-5' carbon atom. The correlation
between the 19-СH and 5'-СH protons in NOESY spectrum
indicated that the product consisted of (5'S)-isomer (Fig. 2).
The in vitro cytotoxic activity of compounds 4–9, 12,
13а,b was studied by using the cancer cell lines A549,
Hep-2, HCT116, MS, PC-3, MCF-7, RD TE32, and the
noncancer cell line HEK293 (Table 1). DMSO solutions
were prepared using camptothecin as a positive control
Figure 2. Key correlations in 1H–13C HMBC and NOESY spectra
of compound 13а.
compound, the study compounds 4–9, 12, 13а, and the
mixture of epimers 13а,b. The DMSO solutions were
subsequently diluted with the culture medium. Control
cells were treated with the culture medium containing 1%
DMSO.
According to the obtained data (Table 1), the hetero-
cyclic derivatives 8, 9, 13а, 13а,b were less cytotoxic than
the starting compounds 4–7, 12, which exhibited cyto-
Table 1. Cytotoxic activity (IC50, µM) of compounds 4–9, 12, 13а, 13а,b
Cell lines
Compound
HEK293
1.84 0.095
4.75 0.34
13.36 0.56
5.09 0.24
82.61 4.44
82.61 4.44
26.23 4.76
>100
Hep-2
HCT116
0.74 0.06
1.99 0.2
5.08 0.23
7.02 0.23
55.89 5.07
55.89 5.07
11.84 0.16
>100
MS
RD TE32
A549
MCF-7
PC-3
2.23 0.20
2.35 0.78
2.24 0.30
4.68 0.37
9.45 0.13
>100
0.66 0.05
1.32 0.09
1.07 0.12
2.35 0.16
8.09 0.32
8.69 1.33
52.71 1.91
52.71 1.91
12.41 0.18
>100
1.32 0.51
4
5
1.36 0.39
3.85 1.63
2.37 0.02
1.08 0.1
7.74 1.13
2.22 0.34
5.91 0.09
5.59 0.31
6
11.97 1.83
4.93 0.74
8.56 1.12
7.10 0.43
7
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
8
>100
−
9
20.84 1.65
97.70 3.22
64.08 14.93
−
12
13а
13а,b
−
−
26.92 2.12
1.61 1.075
37.31 6.76
22.18 2.15
Camptothecin 3.007 0.166 1.883 0.094 0.772 0.337 1.716 0.336 1.308 0.025 0.036 0.009
1.92 0.06
1324

Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
toxicity (IC50 0.66–26.23 µM) against all tested cell lines.
(3H, s, CH3); 0.97 (3H, s, CH3); 1.10 (3H, s, CH3); 1.12
(3H, s, CH3); 1.17 (3H, s, CH3); 1.18 (3H, s, CH3); 3.48
(1H, d, J = 8.3) and 3.79 (1H, d, J = 8.3, 28-СH2); 3.57
(1H, s, 19-СН); 7.90 (1H, s, 1-СH); 10.00 (1H, s, 31-СH).
13C NMR spectrum, δ, ppm (J, Hz): 12.8; 13.5; 15.8; 18.3;
18.6; 20.7; 21.1; 24.0; 25.7; 25.9; 27.5; 28.3; 32.2; 32.6;
33.9; 35.8; 36.2; 39.4; 40.6; 41.0; 41.4; 44.0; 44.6; 46.2;
52.4; 70.7 (C-28); 87.4 (C-19); 131.0 (C-2); 165.2 (C-1);
189.8 (C-31); 203.1 (C-3).
3β,28-Diacetoxylup-20(29)-en-30-al (11). Yield 1.08 g
(50%), mp 244–250°С (mp 246–248°C31). 1H NMR
spectrum, δ, ppm (J, Hz): 0.74–2.18 (24Н, m, 4СН,
10СН2); 0.82 (3H, s, CH3); 0.83 (6H, s, 2CH3); 0.93 (3H, s,
CH3); 1.02 (3H, s, CH3); 2.02 (3H, s, 32(34)-CH3); 2.05
(3H, s, 34(32)-CH3); 2.80 (1Н, td, J = 11.3, J = 5.3,
19-СН); 3.86 (1H, d, J = 11.1) and 4.27 (1H, d, J = 11.1,
28-CH2); 4.44 (1Н, dd, J = 10.8, J = 5.5, 3-СН); 5.91 (1H,
s) and 6.25 (1Н, s, 29-СН2); 9.50 (1Н, s, 30-СН). 13C NMR
spectrum, δ, ppm (J, Hz): 14.6; 16.0; 16.1 (2С); 16.4; 18.1;
20.8; 20.9; 21.2; 23.7; 27.0 (2С); 27.4; 27.9; 29.8; 34.1;
34.5; 37.0; 37.3; 37.8; 38.4; 40.9; 42.6; 46.6 (2С); 50.1;
55.4; 62.4 (C-28); 80.9 (C-3); 133.1 (C-29); 156.5 (C-20);
170.9; 171.3; 194.6 (C-30).
Moderate cytotoxicity against the MCF-7 cell line was
shown by (5'S,R)-pyrazoline 13а,b, while its (5'S)-isomer
13а was not active, pointing to the (5'R)-epimer as the main
contributor to the cytotoxic activity of (5'S,R)-isomer
mixture.
Thus, we have developed an approach for the synthesis
of triterpenoids bearing 1-acetyl-3-methyl-4,5-dihydro-1H-
pyrazole and 3-methyl-4,5-dihydroisoxazole moieties, on
the basis of a cycloaddition reaction between acetic
hydrazide or hydroxylamine and the aldol condensation
products obtained from α,β-unsaturated lupane and 19β,28-
epoxy-18α-oleanane aldehydes with acetone.
Experimental
IR spectra were recorded on a Bruker IFS 66/S FT-IR
1
spectrometer for solutions in CНCl3. Н and 13С NMR
spectra (400 and 100 MHz, respectively), as well as two-
1
1
dimensional COSY, NOESY, H–13C HSQC, and H–13C
HMBC spectra were acquired on a Bruker Avance II
spectrometer for samples in CDCl3 solutions, using HMDS
1
as internal standard for Н NMR spectra (δ 0.06 ppm) and
the CDCl3 signal as internal standard for 13C NMR spectra
(δ 77.2 ppm). Chromato-mass spectroscopy analysis was
performed on an Agilent Technologies 6890N instrument
equipped with an HP-5ms capillary column, 15000 × 0.25 mm,
evaporator temperature 240°С with temperature program in
the range of 20–40°C/min, carrier gas – helium, EI
ionization. High-resolution mass spectra for solutions of
compounds 13а and 13а,b in MeCN were recorded on a
Bruker maXis Impact HD instrument with electrospray
ionization in positive ion mode, nitrogen flow 3.0 l/min,
nebulizer pressure 0.3 bar, probe voltage 4.5 kV. Elemental
analysis was performed using a vario EL cube elemental
analyzer. Melting points were determined at a heating rate
of 1°C/min on an OptiMelt MPA100 apparatus. The
specific optical rotation values were measured for solutions
in CНCl3 on a PerkinElmer 341 polarimeter at 589 nm
wavelength. Merck silica gel (60–200 µm) was used for
column chromatography. Thin-layer chromatography was
performed on Sorbfil plates, eluting with hexane–EtOAc
system, visualization by treatment with 10% H2SO4
followed by heating at 95–100°С for 2–3 min.
Preparation of compounds 6 and 12 (General
method). A solution of aldehyde 4 (0.93 g, 2 mmol) or
aldehyde 11 (1.08 g, 2 mmol) in a mixture of Ме2СО
(5 ml) and PhH (10 ml) was treated by a dropwise addition
of aqueous 10% NaOH solution (0.1 ml). The reaction
mixture was stirred at room temperature, the reaction
progress was controled by TLC. The reaction mixture was
then washed with 10% HCl solution, extracted with PhH
(2×10 ml), and washed with H2O (2×10 ml). The organic
layer was separated, dried over anhydrous MgSO4,
evaporated at reduced pressure, and the residue was
purified by silica gel column chromatography. Eluent
petroleum ether – EtOAc, 5:1 (for compound 6) or 10:1
(for compound 12).
2-((S,R)-4-Hydroxy-2-oxobutyl)-19β,28-epoxy-18α-olean-
1(2)-en-3-one (6). Yield 0.42 g (40%), mp 136–139°С,
21
[α]D –9.00° (с 1.0, CНCl3). IR spectrum, ν, cm–1: 1712
1
(С=O), 3412 (ОН). H NMR spectrum, δ, ppm (J, Hz):
0.82 (3H, s, CH3); 0.87–1.83 (20Н, m, 4СН, 8СН2); 0.93
(0.9H, s) and 0.94 (2.1Н, s, CH3); 0.95 (3H, s, CH3); 1.05
(3H, s, CH3); 1.06 (3H, s, CH3); 1.10 (1.8Н, s) and 1.11
(4.2Н, s, 2CH3); 2.17 (2.1Н, s) and 2.18 (0.9Н, s, 34-СH3);
2.58 (0.3Н, dd, J = 17.1, J = 8.9), 2.59 (0.7Н, dd, J = 17.1,
J = 8.9), 2.78 (0.7Н, dd, J = 17.1, J = 4.0) and 2.95 (0.3Н,
dd, J = 17.1, J = 4.0, 32-СН2); 3.47 (1H, d, J = 7.8) and
3.79 (1H, d, J = 7.8, 28-СH2); 3.56 (1H, s, 19-СН); 4.73
(0.3Н, dd, J = 8.8, J = 3.4) and 4.89 (0.7Н, dd, J = 8.8,
J = 3.4, 31-СН); 7.18 (0.7Н, s) and 7.20 (0.3Н, s, 1-СН).
Mass spectrum, m/z (Irel, %): 506 [M−Н2О]+ (100). Found,
%: C 78.02; H 9.81. C34H52O4. Calculated, %: C 77.82;
H 9.99.
Preparation of compounds 4 and 11 (General
method). A solution of compound 3 (1.82 g, 4.0 mmol) or
compound 10 (2.09 g, 4.0 mmol) in 1,4-dioxane (20 ml)
was treated by the addition of H2SeO3 (0.9 g, 7 mmol). The
reaction mixture was refluxed for 4 h, then washed with
H2O (50 ml) and extracted with EtOAc (2×50 ml). The
organic layer was separated and dried over anhydrous
MgSO4, then the solvent was removed by distillation. The
residue was purified by silica gel column chromatography.
Eluent petroleum ether – EtOAc, 7:1 (for compound 4) or
10:1 (for compound 11).
2-Formyl-19β,28-epoxy-18α-olean-1(2)-en-3-one (4).
Yield 1.50 g (80%), mp 172–176°С (mp 173.9°С26),
[α]D21–9.6° (с 0.6, CНCl3). IR spectrum, ν, cm–1: 1701,
30-((S,R)-4-Hydroxy-2-oxobutyl)lup-20(29)-ene-3β,28-
diyl diacetate (12). Yield 0.45 g (40%), mp 152–154°С,
21
[α]D –9.2° (с 0.6, CНCl3). IR spectrum, ν, cm–1: 1733
1
1
1720 (С=O, HС=O). H NMR spectrum, δ, ppm (J, Hz):
(С=О), 3488 (ОН). H NMR spectrum, δ, ppm (J, Hz):
0.81–1.84 (20Н, m, 4СН, 8СН2); 0.84 (3H, s, CH3); 0.94
0.76–1.87 and 2.01–2.35 (25Н, 2m, 5СН, 10СН2); 0.82
1325

Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
(3H, s, CH3); 0.84 (6H, br. s, 2CH3); 0.95 (1.8H, s), 0.98
reduced pressure, the residue was purified by silica gel
column chromatography, eluent petroleum ether – EtOAc,
1:1. Yield 67 mg (30%).
(1.2H, s), 1.02 (1.8H, s) and 1.03 (1.2H, s, 2CH3); 2.02
(3Н, s, 32(34)-СН3); 2.05 (3Н, s, 34(32)-СН3); 2.19 (3Н, s,
37-СН3); 2.54–2.72 (2Н, m, 19-СН, 35-СН2); 2.86–2.94
(1H, m, 35-СH2); 3.83 (0.6H, d, J = 11.0), 3.85 (0.4H, d,
J = 11.0), 4.20 (0.6H, d, J = 11.0) and 4.23 (0.4H, d,
J = 11.0, 28-СH2); 4.43–4.50 (2H, m, 3-СH, 30-СН); 4.91
(0.4Н, s), 4.95 (0.6Н, s) 5.00 (0.4Н, s), and 5.09 (0.6Н, s,
29-СН2). Mass spectrum, m/z (Irel, %): 540 [M–(CН3)2CО]+
(100). Found, %: C 74.47; H 9.93. C37H58O6. Calculated,
%: C 74.21; H 9.76.
Method III. A solution of compound 6 (0.21 g (0.4 mmol)
in AcOH (25 ml) was treated by the addition of acetic
hydrazide (0.37 g, 5 mmol). The reaction mixture was
heated at reflux for 4 h. The reaction mixture was worked
up in accordance with the method II. Yield 0.17 g (76%),
21
mp 182–183°С, [α]D +118.2° (с 0.7, CНCl3). IR spect-
rum, ν, cm–1: 1664 (С=O, С=N). 1H NMR spectrum, δ, ppm
(J, Hz): 0.80 (3H, s, СН3); 0.82–1.73 (20Н, m, 4СН,
8СН2); 0.90 (2.1H, s) and 0.92 (0.9H, s, СН3); 0.93 (3H, s,
СН3); 1.01 (3H, s, СН3); 1.02 (3H, s, СН3); 1.06 (2.1H, s)
and 1.09 (0.9Н, s, CH3); 1.13 (3H, s, СН3); 2.00 (2.1Н, s)
and 2.03 (0.9Н, s, 8'-СН3); 2.24 (0.9Н, s) and 2.26 (2.1Н, s,
7'-СН3); 2.41 (0.7Н, dd, J = 18.3, J = 5.3), 2.58 (0.3Н, dd,
J = 18.3, J = 5.3), 3.11 (0.3Н, dd, J = 18.3, J = 11.6) and
3.19 (0.7Н, dd, J = 18.3, J = 11.6, 4'-CН2); 3.45 (1H, d,
J = 7.8) and 3.77 (1H, d, J = 7.8, 28-CH2); 3.54 (1H, s,
19-CН); 5.00 (0.3Н, dd, J = 11.6, J = 5.3) and 5.01 (0.7Н,
dd, J = 5.3, J = 11.6, 5'-CН); 6.78 (0.7H, s) and 6.82 (0.3H,
s, 1-CH). Mass spectrum, m/z (Irel, %): 562 [M]+ (100).
Found, %: C 76.88; H 9.63; N 4.94. C36H54N2O3.
Calculated, %: C 76.82; H 9.67; N 4.98.
2-((Е)-2-Oxobut-3-enyl)-19β,28-epoxy-18α-olean-1(2)-
en-3-one (7). Aqueous 10% NaOH solution (0.1 ml) was
added to a solution of aldehyde 4 (0.93 g, 2 mmol) in
Ме2СО (10 ml), then the reaction mixture was stirred for
6 h at room temperature. After diluting with 10% HCl
solution, the reaction mixture was extracted with EtOAc
(2×30 ml). The organic layer was separated, washed with
H2O, dried over MgSO4, filtered, and evaporated to
dryness. The residue was purified by silica gel column
chromatography, eluent petroleum ether – EtOAc, 7:1.
21
Yield 0.40 g (40%), mp 124–128°С, [α]D +4.53° (с 0.8,
CНCl3). IR spectrum, ν, cm–1: 1675 (С=O). 1H NMR
spectrum, δ, ppm (J, Hz): 0.79–1.79 (20Н, m, 4СН,
8СН2,); 0.82 (3H, s, CH3); 0.93 (3H, s, CH3); 0.94 (3H, s,
CH3); 1.06 (6H, s, 2CH3); 1.11 (3H, s, CH3); 1.15 (3H, s,
CH3); 2.29 (3Н, s, 34-СН3); 3.46 (1H, d, J = 7.8) and 3.77
(1H, d, J = 7.8, 28-СH2); 3.55 (1H, s, 19-СН); 6.68 (1Н, d,
J = 16.3, 32-СН); 7.20 (1Н, d, J = 16.3, 31-СН); 7.33 (1Н,
s, 1-СН). 13C NMR spectrum, δ, ppm: 13.3; 16.2; 19.2;
19.3; 21.3; 21.7; 24.5; 26.2; 26.3; 26.4; 27.6; 28.5; 28.8;
32.7; 33.1; 34.5; 36.3; 36.7; 39.7; 41.1; 41.5; 41.6; 45.0;
45.3; 46.7; 52.6; 71.2 (C-28); 87.9 (C-19); 128.8; 130.9
(C-2); 138.8; 161.2 (C-1); 198.8 (C-33); 203.6 (C-3). Mass
spectrum, m/z (Irel, %): 506 [M]+ (100). Found, %: C 80.70;
H 10.01. C34H50O3. Calculated, %: C 80.58; H 9.94.
2-((S,R)-3-Methyl-4,5-dihydroisoxazol-5-yl)-19β,28-
epoxy-18α-olean-1(2)-en-3-one (9).
A
solution of
compound 6 (0.21 g, 0.4 mmol) in EtOH (25 ml) was
treated by the addition of AcONa (0.04 g, 0.5 mmol) and
NH2OH·HCl (0.035 g, 0.5 mmol). The reaction mixture
was heated at reflux for 4 h. The reaction mixture was
extracted with EtOAc and washed with H2O (2×10 ml).
The organic layer was separated, dried over anhydrous
MgSO4, evaporated at reduced pressure, the residue was
purified by silica gel column chromatography, eluent petro-
leum ether – EtOAc, 7:3. Yield 0.19 g (82%), mp 131–
21
133°С, [α]D +69.6° (с 0.6, CНCl3). IR spectrum, ν, cm–1:
1
2-((S,R)-1-Acetyl-3-methyl-4,5-dihydro-1H-pyrazol-
5-yl)-19β,28-epoxy-18α-olean-1(2)en-3-one (8). Method I.
A solution of compound 7 (0.20 g, 0.4 mmol) in EtOH
(25 ml) was treated by the addition of acetic hydrazide
(0.37 g, 5 mmol) and 5 drops of AcOH. The reaction
mixture was refluxed for 4 h. The solvent was removed
from the reaction mixture by evaporation at reduced
pressure. The dry residue was dissolved with stirring in
pyridine (5 ml) and acetic anhydride (5 ml), then left at
room temperature for 24 h. The obtained reaction mixture
was washed with 10% HCl solution until acidic pH, then
extracted with EtOAc (2×10 ml) and washed with H2O
(5×10 ml) until neutral pH was achieved. The organic layer
was separated, dried over anhydrous MgSO4, evaporated at
reduced pressure, the residue was purified by silica gel
column chromatography, eluent petroleum ether – EtOAc,
1:1. Yield 34 mg (15%).
1659 (С=N, С=O). H NMR spectrum, δ, ppm (J, Hz):
0.79–1.79 (20Н, m, 4СН, 8СН2); 0.81 (3H, s, СН3); 0.92
(0.9H, s, СН3); 0.93 (2.1H, s, СН3); 0.94 (3H, s, СН3); 1.03
(2.1H, s, СН3); 1.04 (0.9H, s, СН3); 1.05 (3H, s, СН3); 1.08
(3Н, s, CH3); 1.09 (2.1H, s, СН3); 1.11 (0.9H, s, СН3); 1.89
(2.1Н, s, 3'-СН3); 1.90 (0.9Н, s, 3'-СН3); 2.32 (0.3Н, dd,
J = 15.2, J = 8.0), 2.34 (0.7Н, dd, J = 15.2, J = 8.0), 2.47
(0.7Н, dd, J = 15.0, J = 4.0) and 2.61 (0.3Н, dd, J = 15.0,
J = 4.0, 4'-CН2); 3.46 and 3.78 (2H, 2d, J = 7.7, 28-CH2);
3.55 (1H, s, 19-CН); 4.59 (0.3Н, dd, J = 8.5, J = 4.0) and
4.77 (0.7Н, dd, J = 8.5, J = 4.0, 5'-CН); 7.14 (1H, br. s,
1-CH). Mass spectrum, m/z (Irel, %): 519 [M−Н2]+ (100).
Found, %: C 78.31; H 9.78; N 2.75. C39H51NO3.
Calculated, %: C 78.26; H 9.85; N 2.68.
3β,28-Diacetoxy-30-(1-acetyl-3-methyl-4,5-dihydro-
1H-pyrazol-5-yl)lup-20(29)-enes 13a,b (a mixture of
isomers). A solution of compound 12 (0.48 g, 0.8 mmol) in
AcOH (20 ml) was treated by the addition of acetic
hydrazide (0.74 g, 10 mmol) and heated at reflux for 4 h.
The reaction mixture was extracted with EtOAc and
washed with H2O (2×10 ml). The organic layer was
separated, dried over anhydrous MgSO4, evaporated at
reduced pressure, the residue was purified by silica gel
Method II. A solution of compound 7 (0.20 g,
0.4 mmol) in AcOH (25 ml) was treated by the addition of
acetic hydrazide (0.37 g, 5 mmol). The reaction mixture
was refluxed for 4 h, then extracted with EtOAc and
washed with H2O (5×10 ml). The organic layer was
separated, dried over anhydrous MgSO4, evaporated at
1326

Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
column chromatography, eluent petroleum ether – EtOAc,
using the riding model. The final parameters of refinement
21
5:1. Yield 0.33 g (64%), mp 140–144°С, [α]D +5.2° (с 0.5,
were the following: R1 0.0526 (for 5360 reflections with
I > 2σ(I)), wR2 0.1388 (for all 6052 independent reflec-
tions), S 1.028. The complete X-ray structural analysis
dataset for compound 4 was deposited at the Cambridge
Crystallographic Data Center (deposit CCDC 1970634).
Biological activity study. The following cancer cell
lines were selected for the study: human nonsmall cell lung
cancer cell line A549, laryngeal carcinoma cell line Hеp-2,
human colorectal cancer cell line HCT116, human
melanoma cell line MS, human prostate cancer cell line PC-3,
human breast adenocarcinoma cell line MCF-7, human
rhabdomyocarcoma cell line RD TE32, and the noncancer
cell line HEK293, obtained from the Institute of
Experimental Diagnostics and Therapy of Cancer at the
N. N. Blokhin Russian Cancer Research Center of the Russian
Academy of Medical Sciences (Moscow, Russia). The cells
were inoculated on 96-well microplates and cultured in
DMEM growth medium (for the cell lines RD TE32, A549,
HCT116, PC-3, Hеp-2, MCF-7, HEK293) or RPMI 1640
growth medium (in the case of the cell line MS) with the
addition of fetal bovine serum (10%) and glutamine (0.3%)
at 37°С under 5% СО2 atmosphere in a Barnstead Isotemp
CO2 incubator. The study compounds were added to the
microplate wells after 24 h as 100 µM solutions in DMSO,
followed by serial dilution to 1.56 µM. The concentration
of DMSO in the microplate wells did not exceed 1%. The
survival rate of cells was determined after 72 h incubation
of the cells with the study compounds by using MTT test38
with a FLUOstar OPTIMA microplate reader (BMG
Labtech GmbH, Germany). The IC50 values corresponding
to 50% cell death were used as a quantitative criterion for
the expression of cytotoxicity due to the test compounds.
The control was assumed as 100%, in the case of cells
incubated in the respective growth media with the addition
of 1% of DMSO. The experiments were performed in
triplicate.
CНCl3). IR spectrum, ν, cm–1: 1664 (С=O, С=N). 1H NMR
spectrum, δ, ppm (J, Hz): 0.76–2.17 (25Н, m, 5СН,
10СН2); 0.82 (3H, 3s, CH3); 0.83 (3H, s, CH3); 0.84 (3H, s,
CH3); 0.95 (1.8H, s) and 0.99 (1.2H, s, CH3); 1.03 (3H, s,
CH3); 1.99 (1.2Н, s) and 2.00 (1.8Н, s, 8'-СН3); 2.01 (3Н,
s, ОСОСН3); 2.04 (1.8Н, s) and 2.05 (1.2Н, s, ОСОСН3);
2.24 (1.8Н, s) and 2.25 (1.2Н, s, 7'-СН3); 2.45–2.59 (1Н, m)
and 3.03–3.10 (1Н, m, 4'-CН2); 3.79 (0.6H, d, J = 10.9),
3.81 (0.4H, d, J = 10.9) and 4.24 (1H, d, J = 10.9, 28-CH2);
4.45 (1Н, dd, J = 10.4, J = 6.3, 3-CН); 4.65 (0.4Н, s) and
4.74 (0.6Н, s, 29-CН2); 4.75–4.80 (1Н, m, 5'-CН); 4.77
(0.4Н, s) and 4.86 (0.6Н, s, 29-CН2). Found, m/z: 637.4569
[M+H]+. C39H61N2O5. Calculated, m/z: 637.4575. Found,
%: C 73.14; H 9.70; N 4.29. C39H60N2O5. Calculated, %:
C 73.55; H 9.50; N 4.40.
3β,28-Diacetoxy30-((5S)-1-acetyl-3-methyl-4,5-dihydro-
1H-pyrazol-5'-yl)-lup-20(29)-ene (13a). The mixture of
isomers 13a,b was purified by silica gel column chromato-
graphy, eluent petroleum ether – EtOAc, 5:1. Yield 0.13 g
21
(40%), mp 119–122°С, [α]D +26.2° (с 0.5, CНCl3).
1
IR spectrum, ν, cm–1: 1664 (С=O, С=N). H NMR spect-
rum, δ, ppm (J, Hz): 0.76–2.15 (25Н, m, 5СН, 10СН2);
0.82 (3H, s, CH3); 0.83 (3H, s, CH3); 0.84 (3H, s, CH3);
0.95 (3H, s, CH3); 1.02 (3H, s, CH3); 2.00 (3Н, s, 8'-СН3);
2.01 (3Н, s, 32(34)-СН3); 2.05 (3Н, s, 34(32)-СН3); 2.25
(3Н, s, 7'-СН3); 2.56 (1Н, dd, J = 17.9, J = 4.7) and 3.06
(1Н, dd, J = 17.9, J = 11.5, 4'-CН2); 3.79 (1H, d, J = 11.0)
and 4.24 (2H, d, J = 11.0, 28-CH2); 4.45 (1Н, dd, J = 9.4,
J = 6.4, 3-CН); 4.74 (1Н, 2s) and 4.86 (1Н, s, 29-CН2);
4.78 (1Н, dd, J = 11.5, J = 4.7, 5'-CН). 13C NMR spectrum,
δ, ppm (J, Hz): 14.8; 16.1 (3С); 16.5; 18.2; 21.0; 21.1;
21.2; 21.9; 23.7; 27.0; 27.6; 28.0; 29.7; 29.8; 32.7; 34.2;
34.6; 37.1; 37.7; 37.8; 38.5; 41.0; 42.8 (С-19); 43.8 (С-4');
46.2; 50.3; 51.5; 55.4; 61.0 (C-5'); 62.6 (C-28); 80.9 (C-3);
107.2 (C-29); 152.9 (C-20); 155.2 (C-3'); 168.4 (C-6');
170.9 (C-31); 171.5 (C-33). Found, m/z: 637.4580 [M+H]+.
C39H61N2O5. Calculated, m/z: 637.4575. Found, %:
C 73.10; H 9.69; N 4.33. C39H60N2O5. Calculated, %:
C 73.55; H 9.50; N 4.40.
1
Supplementary information file containing Н and 13С
NMR spectra and two-dimensional NMR spectra of the
synthesized compounds is available at the journal website
at http://link.springer.com/journal/10593.
X-ray structural analysis of compound 4. Crystals
suitable for X-ray structural analysis were obtained by slow
evaporation of a solution of compound 4 in 5:1 hexane–
EtOAc mixture. The X-ray structural analysis was
performed on an Xcalibur Ruby automatic four-circle
monocrystal diffractometer equipped with a ССD-detector
according to the standard procedure (MoKα radiation,
ω-scanning with a step of 1°) at 295(2) K. The absorption
was accounted for empirically, using the SCALE3
ABSPACK algorithm.34 The crystal (C31H46O3, M 466.68)
had monoclinic syngony, space group P21; a 8.7956(17),
b 9.9842(15), c 15.227(2) Å; β 100.632(17)°; V 1314.2(4) Å3;
Z 2; dcalc 1.179 g/cm3; μ 0.073 mm–1. The structure was
solved by using the Superflip software35 and refined by full-
matrix method of least squares by F2 in anisotropic
approximation for all non-hydrogen atoms with the
SHELXL program36 in combination with the OLEX2
graphical interface.37 The atom positions were refined by
This work was performed with financial support from the
Russian Foundation for Basic Research (grant 18-03-00050).
The authors would like to express their gratitude to the
Collective Use Center of Perm Federal Research Center of
the Ural Branch of the Russian Academy of Sciences
''Investigation of Materials and Compounds'' for the
spectral, analytic, and biological studies.
References
1. Csuk, R. Expert Opin. Ther. Pat. 2014, 24, 913.
2. Bednarczyk-Cwynar, B.; Günther, A. Curr. Med. Chem. 2017,
24, 2205.
3. Borkova, L.; Hodon, J.; Urban, M. Asian J. Org. Chem. 2018,
7, 1542.
4. Sousa, J. L. C.; Freire, C. S. R.; Silvestre, A. J. D.; Silva, A. M. S.
Molecules 2019, 24, 355.
1327

Chemistry of Heterocyclic Compounds 2020, 56(10), 1321–1328
5. Yamansarov, E. Yu.; Saltykova, I. V.; Kovalev, S. V.;
20. Khusnutdinova, E. F.; Kazakova, O. B.; Lobov, A. N.;
Kukovinets, O. S.; Suponitsky, K. Yu.; Meyers, C. B.;
Prichard, M. N. Org. Biomol. Chem. 2019, 17, 585.
21. Borková, L.; Frydrych, I.; Jakubcová, N.; Adámek, R.;
Lišková, B.; Gurská, S.; Medvedíková, M.; Hajdúch, M.;
Urban, M. Eur. J. Med. Chem. 2019, 185, 111806.
22. Grishko, V. V.; Galaiko, N. V.; Tolmacheva, I. A.; Kucherov, I. I.;
Eremin, V. F.; Boreko, E. I.; Savinova, O. V.; Slepukhin, P. A.
Eur. J. Med. Chem. 2014, 83, 601.
Petrov, R. A.; Shkil', D. O.; Seleznev, E. I.; Beloglazkina, E. K.;
Majouga, A. G. Russ. Chem. Bull., Int. Ed. 2019, 68, 855.
[Izv. Akad. Nauk, Ser. Khim. 2019, 855.]
6. Haavikko, R.; Nasereddin, A.; Sacerdoti-Sierra, N.;
Kopelyanskiy, D.; Alakurtti, S.; Tikka, M.; Jaffe, C. L.; Yli-
Kauhaluoma, J. Med. Chem. Commun. 2014, 5, 445.
7. Kvasnica, M.; Urban, M.; Dickinson, N. J.; Sarek, J. Nat.
Prod. Rep. 2015, 32, 1303.
8. Sidova, V.; Zoufaly, P.; Pokorny, J.; Dzubak, P.; Hajduch, M.;
Popa, I.; Urban, M. PLoS ONE 2017, 12, e0171621.
9. Uzenkova, N. V.; Petrenko, N. I.; Shakirov, M. M.; Shul'ts, E. E.;
Tolstikov, G. A. Chem. Nat. Compd. 2005, 41, 692. [Khim.
Prirod. Soedin. 2005, 571.]
10. Zorina, A. D.; Nikiforova, N. S.; Zarubaev, V. V.;
Marchenko, S. A.; Selivanov, S. I.; Starova, G. L.;
Mehtiev, A. R.; Rodionov, E. I.; Rodionova, A. A.; Trifonov, R. E.
Mendeleev Commun. 2019, 29, 500.
11. Santos, R. C.; Salvador, J. A. R.; Marín, S.; Cascante, M.
Bioorg. Med. Chem. 2009, 17, 6241.
12. Thi, T. A. D.; Tuyet, N. T. K.; The, C. P.; Nguyen, H. T.; Thi, C. B.;
Duy, T. D.; D'hooghe, M.; Nguyen, T. V. Bioorg. Med. Chem.
Lett. 2014, 24, 5190.
13. Cui, H.-W.; He, Y.; Wang, J.; Gao, W.; Liu, T.; Qin, M.;
Wang, X.; Gao, C.; Wang, Y.; Liu, M.-Y.; Yi, Z.; Qiu, W.-W.
Eur. J. Med. Chem. 2015, 95, 240.
23. Tolmacheva, I. A.; Galaiko, N. V.; Igosheva, E. V.; Konysheva,
A. V.; Nazarov, A. V.; Krainova, G. F.; Gorbunova, M. N.;
Boreko, E. I.; Eremin, V. F.; Grishko, V. V. In Chemistry and
Technology of Plant Substances. Chemical and Biochemical
Aspects; Kutchin, A. V.; Shishkina, L. N.; Weisfeld, L. I., Eds.;
Apple Academic Press: Oakville, 2017, p. 3.
24. Konysheva, A. V.; Nebogatikov, V. O.; Tolmacheva, I. A.;
Dmitriev, M. V.; Grishko, V. V. Eur. J. Med. Chem. 2017,
140, 74.
25. Tolmacheva, I. A.; Nazarov, A. V.; Eroshenko, D. V.;
Grishko, V. V. Steroids 2018, 140, 131.
26. Tolmacheva, I. A.; Eroshenko, D. V.; Grishko, V. V. Chem.
Nat. Compd. 2018, 54, 705. [Khim. Prirod. Soedin. 2018, 597.]
27. Klinot, J.; Světlý, J.; Kudlačková, D.; Buděšinský, M.;
Vystrčil, A. Collect. Czech. Chem. Commun. 1979, 44, 211.
28. Nazarov, M. A.; Zhikina, L. A.; Tolmacheva, I. A.; Grishko, V. V.
Bashk. Khim. Zhurn. [in Russian] 2017, 24(4), 28.
14. Babak, N. L.; Semenenko, A. N.; Gella, I. M.; Musatov, V. I.;
Shishkina, S. V.; Novikova, N. B.; Sofronov, D. S.;
Morina, D. A.; Lipson, V. V. Russ. J. Org. Chem. 2015, 51,
715. [Zh. Org. Khim. 2015, 51, 731.]
15. Khlebnicova, T. S.; Piven, Y. A.; Baranovsky, A. V.;
Lakhvich, F. A.; Shishkina, S. V.; Zicāne, D.; Tetere, Z.;
Rāviņa, I.; Kumpiņš, V.; Rijkure, I.; Mieriņa, I.; Peipiņš, U.;
Turks, M. Steroids 2017, 117, 77.
16. Galaiko, N. V.; Nazarov, A. V.; Tolmacheva, I. A.;
Slepukhin, P. A.; Vikharev, Yu. B.; Maiorova, O. A.;
Grishko, V. V. Chem. Heterocycl. Compd. 2014, 50, 65.
[Khim. Geterotsikl. Soedin. 2014, 72.]
17. Gubaidullin, R. R.; Yarmukhametova, D. S.; Nedopekina, D. A.;
Khalitova, R. R.; Spivak, A. Yu. ARKIVOC 2017, (v), 100.
18. Grishko, V. V.; Tolmacheva, I. A.; Nebogatikov, V. O.;
Galaiko, N. V.; Nazarov, A. V.; Dmitriev, M. V.; Ivshina, I. B.
Eur. J. Med. Chem. 2017, 125, 629.
29. Macrae, C. F.; Bruno, I. J.; Chisholm, J. A.; Edgington, P. R.;
McCabe, P.; Pidcock, E.; Rodriguez-Monge, L.; Taylor, R.;
van de Streek, J.; Wood, P. A. J. Appl. Crystallogr. 2008, 41, 466.
30. Lévai, A. J. Heterocycl. Chem. 2002, 39, 1.
31. Iványi, Z.; Szabó, N.; Huber, J.; Wölfling, J.; Zupkó, I.;
Szécsi, M.; Wittmann, T.; Schneider, G. Steroids 2012, 77,
566.
32. Romero-López, A.; Montiel-Smith, S.; Meza-Reyes, S.;
Merino-Montiel, P.; Vega-Baez, J. L. Steroids 2014, 87, 86.
33. Ghosh, P.; Mandal, A.; Ghosh, J.; Pal, C.; Nanda, A. K.
J. Asian Nat. Prod. Res. 2012, 14, 141.
34. CrysAlisPro, Version 1.171.37.33 (release 27-03-2014
CrysAlis171.NET); Agilent Technologies: Yarnton, 2014.
35. Palatinus, L.; Chapuis, G. J. Appl. Crystallogr. 2007, 40, 786.
36. Sheldrick, G. M. Acta Crystallogr., Sect. C: Struct. Chem.
2015, C71, 3.
37. Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;
Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339.
19. Zorina, A. D.; Nikiforova, N. S.; Zarubaev, V. V.;
Marchenko, S. A.; Selivanov, S. I.; Starova, G. L.;
Mehtiev, A. R.; Rodionov, E. I.; Rodionova A. A.;
Trifonov, R. E. Mendeleev Commun. 2019, 29, 500.
38. Scudiero, D. A.; Shoemaker, R. H.; Paull, K. D.; Monks, A.;
Tierney, S.; Notziger, T. H.; Currens, M. T.; Seniff, D.;
Boyd, M. K. Cancer Res. 1988, 48, 4827.
1328