Synthesis and cytotoxic properties of some cyclic acetals of diols and their dichlorocyclopropyl derivatives

Article abstract of DOI:10.1007/s11172-021-3111-9

Cyclic acetals of ethylene glycol, cis-but-2-ene-1,4-diol and their dichlorocyclopropyl derivatives were synthesized. Compounds simultaneously containing the gem-dichlorocyclopropane and 1,3-dioxacycloalkane cycles are shown to exhibit cytotoxic activity against the HEK293, SH-SY5Y, HepG2, MCF-7, A549, and Jurkat cell lines. The obtained results open up prospects for further studies of antitumor activity of 2-(2,2-dichlorocyclopropyl)-2-ethyl-1,3-dioxolane.

Full text of DOI:10.1007/s11172-021-3111-9

Russian Chemical Bulletin, International Edition, Vol. 70, No. 3, pp. 475—478, March, 2021
475
Synthesis and cytotoxic properties of some cyclic acetals of diols
and their dichlorocyclopropyl derivatives*
G. Z. Raskil´dina,a U. Sh. Kuzmina,b Sh. Sh. Dzhumaev,a Yu. G. Borisova,a D. V. Ishmetova,b
Yu. V. Vakhitova,b and S. S. Zlotskiia
aUfa State Petroleum Technological University,
1 ul. Kosmonavtov, 450064 Ufa, Russian Federation.
E-mail: graskildina444@mail.ru
bInstitute of Biochemistry and Genetics of the Ufa Federal Research Centre of the Russian Academy of Sciences,
71 prosp. Octyabrya, 450054 Ufa, Russian Federation.
E-mail: ukuzmina87@gmail.com
Cyclic acetals of ethylene glycol, cis-but-2-ene-1,4-diol and their dichlorocyclopropyl
derivatives were synthesized. Compounds simultaneously containing the gem-dichlorocyclo-
propane and 1,3-dioxacycloalkane cycles are shown to exhibit cytotoxic activity against the
HEK293, SH-SY5Y, HepG2, MCF-7, A549, and Jurkat cell lines. The obtained results open
up prospects for further studies of antitumor activity of 2-(2,2-dichlorocyclopropyl)-2-ethyl-
1,3-dioxolane.
Key words: acetals, 1,4-butenediol, cinnamaldehyde, substituted gem-dichlorocyclopropanes,
cytotoxicity in vitro.
Currently, an active search for new biologically active
substances among compounds of plant and synthetic origin
takes place.1—4 Compounds that can be prepared from
basic compounds such as ethylene glycol and cis-but-2-
ene-1,4-diol are attracting attention due to their potential
for use in medicine.5,6 These compounds have a fairly wide
spectrum of biological activity, their herbicidal, antioxi-
dant, antimicrobial and antiviral properties are known.7—11
The present study is aimed at the synthesis of cyclic
acetals of diols and their dichlorocyclopropyl deriva-
tives and investigation of their cytotoxic characteristics
in vitro.
Results and Discussion
Condensation of ethylene glycol (1a) with cinnamal-
dehyde (2а) and ethyl vinyl ketone (2b) in the presence of
sulfuric acid in boiling benzene in accordance with a known
method6 produces cyclic unsaturated acetals 3а,b with
quantitative yields. Their subsequent dichlorocarbenation
by the Makosza method gave corresponding new cyclic
derivatives 4а,b in yields exceeding 90% (Scheme 1).
Bicyclic compound 4с was previously prepared (in yield
exceeding 90%) by acetalization of isobutanal (2с) with
cis-but-2-en-1,4-diol (1b) in the presence of cationite
Scheme 1
* Based on the materials of VI Interdisciplinary Conference "Molecular and Biological Aspects of Chemistry, Pharmaceuticals and
Pharmacology" (September 27—30, 2020, Nizhny Novgorod, Russia).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 475—478, March, 2021.
1066-5285/21/7003-0475 © 2021 Springer Science+Business Media LLC

Raskil´dina et al.
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Russ. Chem. Bull., Int. Ed., Vol. 70, No. 3, March, 2021
KU-2 (Н+) as a catalyst and subsequent dichlorocarbena-
tion of the obtained 2-isopropyl-4,7-dihydro-1,3-dioxepin
(3с) under the phase-transfer catalysis conditions using
a 50% alkali solution and chloroform6 (Scheme 2).
Scheme 3
Scheme 2
against the HEK293, SH-SY5Y, Jurkat, HepG2, MCF-7,
and A549 cell lines. It is important to note that 2-(2,2-di-
chlorocyclopropyl)-2-ethyl-1,3-dioxolane (4b) has a negative
effect only on cell lines of tumor origin (SH-SY5Y,
HepG2, MCF-7, and A549) and does not affect the cell
viability of the conventionally normal HEK293 cell line
(IC50 100 μmol L–1). No effect was revealed for other
prepared compounds (3а—с and 4d,e) in the concentration
To increase the number of compounds involved in the
study of cytotoxic activity, we synthesized6 compounds
4d and 4e from bicyclic derivative 4с in yields >90%
(Scheme 3).
range of 1—100 μmol L–1
.
The structures of the obtained unsaturated acetals
3а—с, their dichlorocyclopropyl derivatives 4а—с, and
dichlorocyclopropyl derivatives 4d,e were proven using
1Н and 13С NMR spectroscopy and gas chromatography—
mass spectrometry.
The study of cytotoxicity was carried out in vitro using
cell lines of normal (HEK293) and tumor (SH-SY5Y,
HepG2, MCF-7, A549 and Jurkat) origin. The results are
given in Table 1.
Studying the effect of the prepared compounds on the
cell viability showed cytotoxic activity of 2-(2,2-dichloro-
3-phenylcyclopropyl)-1,3-dioxolane (4а) and 8,8-di-
chloro-4-isopropyl-3,5-dioxabicyclo[5.1.0]octane (4с)
The degree of selectivity of the negative effect, the
selectivity index (SI), was calculated for compounds ex-
hibiting toxicity (Table 2). This index is important to assess
the prospects of studying the antitumor activity of com-
pounds. It should be noted that the selectivity indices of
modern antitumor chemotherapeutic drugs are in the range
from 4 to 8.12,13 According to the obtained data, com-
pound 4b exhibit selective cytotoxicity against the SH-SY5Y
(SI = 4.28), Jurkat (SI = 5.14), MCF-7 (SI = 3.19), and
A549 (SI = 2.02) tumor cells. Compound 4с has selective
cytotoxicity against the tumor MCF-7 cells (SI = 3.47).
The analysis of the relationship between the chemical
structure and cytotoxicity of new compounds, viz., cyclic
Table 1. Effect of compounds on cell viability (48 h, M m)
Compound
IC50/μmol L–1
HEK293
SH-SY5Y
HepG2
Jurkat
MCF-7
A549
3a
4a
>100
>100
58.67 3.67
(p = 0.01)*
>100
28.19 1.31
(p = 0.00001)*
>100
>100
59.95 3.68
(p = 0.0006)*
>100
74.75 4.21
(p = 0.000006)*
>100
>100
32.65 3.16
(p = 0.00007)*
>100
23.49 0.88
(p = 0.000005)*
>100
>100
27.62 0.77
(p = 0.00001)*
>100
38.29 5.65
(p = 0.000005)*
>100
>100
33.79 2.80
(p = 0.0001)*
>100
59.59 0.42
(p = 0.000005)*
>100
48.08 3.13
3b
4b
>100
>100
3c
4c
>100
73.01 5.71
93.27 9.68
(p = 0.04)*
>100
49.91 7.63
(p = 0.0003)*
>100
37.05 0.88
(p = 0.00001)*
>100
21.06 1.83
(p = 0.000006)*
>100
56.03 4.24
(p = 0.003)*
>100
4d
4e
>100
>100
>100
>100
>100
>100
>100
Note. The results are presented as the arithmetic mean of three independent experiments (M) with indication of the standard error of
*
the mean ( m). Statistically significant differences in the IC50 values for cells of the tumor origin relative to the IC50 values for
HEK293 cells of normal origin (ANOVA, Dunnett's test).

Сyclic acetals of diols and their derivatives
Russ. Chem. Bull., Int. Ed., Vol. 70, No. 3, March, 2021
477
Table 2. Selectivity indices for compounds 4a—c
solvent was removed using a rotary evaporator. The products
were distilled under reduced pressure.
2-(2-Phenylvinyl)-1,3-dioxolane (3a). Yield 90%. B.p. 134 °C
(8 Torr). A colorless liquid. 1Н NMR (CDCl3), δ: 3.45 (d, 2 Н,
2 С(4,5)На, J = 7.0 Hz); 3.54 (t, 2 Н, 2 С(4,5)Нb, J = 7.2 Hz);
5.19 (t, 1 Н, С(6)Н, J = 6.0 Hz); 5.58 (d, 1 Н, С(2)Н, J = 6.9 Hz);
6.55 (d, 1 Н, С(7)Н, J = 6.5 Hz); 7.20—7.30 (m, 5 Н, Ph).
13С NMR (CDCl3), δ: 66.41 (С(4,5)Н2); 101.05 (С(2)Н); 121.70
(С(6)Н); 126.54 (С(7)Н); 127.82 (C(8)); 129.04 (С(9,13));
131.55 (С(10,12)); 139.04 (С(11)). MS (EI), m/z (Irel (%)): 176
[М]+ (60), 131 [М – С3Н5О]+ (30), 115 [М – 2 СН2О]+ (40),
104 [C8H8]+ (100), 77 [C6H5]+ (25).
Com-
pound
SI*
SH-SY5Y HepG2 Jurkat MCF-7
A549
4a
4b
4c
0.82
4.28
1.88
0.80
1.62
1.48
1.47
5.14
1.97
1.74
3.19
3.47
1.42
2.02
1.30
* Selectivity index (SI) of the test compound is the ratio
of IC50 obtained using the HEK293 control cells to IC50
obtained using tumor cells.
2-Ethyl-2-vinyl-1,3-dioxolane (3b). Yield 92%. B.p. 40 °C
(20 Torr). A colorless liquid. 1Н NMR (CDCl3), δ: 0.91 (t, 3 Н,
С(7)Н3, J = 8.0 Hz); 1.63—1.75 (m, 2 Н, С(6)Н2); 3.97 (d, 2 Н,
2 С(4,5)На, J = 7 Hz); 4.02 (t, 2 Н, 2 С(4,5)Нb, J = 6.4 Hz);
5.31 (dd, 1 Н, С(9)Н, J = 7 Hz, J = 11 Hz); 5.38 (dd, 1 Н, С(8)Н,
J = 6.9 Hz, J = 10.8 Hz); 5.56—5.63 (m, 1 Н, СН). 13С NMR
(CDCl3), δ: 9.01 (С(7)Н3); 31.03 (С(6)Н2); 65.39 (С(4,5)Н2);
109.60 (С(2)); 115.98 (С(9)Н2); 141.04 (С(8)Н). MS (EI),
m/z (Irel (%)): 128 [М]+ (10), 99 [М – C2H5]+ (100), 67
[М – 2 СН2О – H]+ (15), 55 [C2H3CO]+ (80).
acetals and their dichlorocyclopropyl derivatives, revealed
the following. Compounds 3а—с and 4d,e containing only
1,3-dioxolane or 1,1-dichlorocyclopropane cycle exhibit
no meaningful toxicity, whereas compounds 4а—с con-
taining both cycles showed strong cytotoxic activity.
2-(2,2-Dichlorocyclopropyl)-2-ethyl-1,3-dioxolane (4b)
is particularly noteworthy because it has pronounced
tumor-specific cytotoxicity combined with low overall
toxicity to cells of normal origin.
In conclusion, we synthesized cyclic acetals of diols and
their dichlorocyclopropyl derivatives. It is found that the
simultaneous presence of dioxacycloalkane and dichlorocyclo-
propane moieties in the structure of the prepared com-
pounds is required for the compound to exhibit cytotoxic
activity. Among the studied compounds, those having selec-
tive cytotoxic activity against cells of the tumor origin were
found. According to the data obtained, compound 4b is
a potential antineoplastic agent. The synthesis of new com-
pounds on its basis in order to improve its characteristics,
as well as further study of the biological activity of the
series of compounds based on it are very promising tasks.
2-Isopropyl-4,7-dihydro-1,3-dioxepin (3c). Yield 90%. B.p.
62 °C (10 Torr). A colorless liquid. The spectral data corresponds
to reported ones.6
Synthesis of acetals 4a—c (general procedure). Compounds
4a—c were synthesized according to a published procedure.6
A mixture containing one of compounds 3а—с (0.05 mol),
chloroform (150 mL), and a 50% solution of NaOH (160 g) was
stirred at 5—7 °С until complete conversion of the starting com-
pound. The mixture was heated to ~20 °C, washed with water
until neutral, dried with calcium chloride; the salt was filtered
out; solvent was removed using a rotary evaporator. The products
were distilled under reduced pressure.
2-(2,2-Dichloro-3-phenylcyclopropyl)-1,3-dioxolane (4а).
1
Yield 90%. B.p. 40 °C (20 Torr). A colorless liquid. Н NMR
(CDCl3), δ: 2.30 (t, 1 Н, С(6)Н, J = 7.0 Hz); 2.70 (d, 1 Н, С(7)
Н, J = 7.9 Hz); 3.84 (d, 2 Н, 2 С(4,5)На, J = 6.7 Hz); 4.02
(t, 2 Н, 2 С(4,5)Нb, J = 6.4 Hz); 5.28 (d, 1 Н, С(2)Н, J = 8.5 Hz);
7.03—7.13 (m , 5 Н, Ph). 13С NMR (CDCl3), δ: 39.01 (С(7)Н);
44.38 (С(6)Н); 66.59 (С(8)); 68.34 (2 С(4,5)Н2); 101.06 (С(2)Н);
126.01 (C(8)); 129.77 (С(9,13)); 131.39 (С(10,12)); 133.61
(С(11)). MS (EI), m/z (Iотн (%)): 259 (10), 261 (7), 263 (4)
[М]+; 135 (50), 137 (30), 139 (10) [М – H2O – СН2О – C6H5]+;
109 (65), 111 (40), 113 (19) [C3H4Cl2]+; 77 [C6H5]+ (55).
2-(2,2-Dichlorocyclopropyl)-2-ethyl-1,3-dioxolane (4b).
Experimental
Reaction products were analyzed using a HRGС 5300 Mega
Series (Carlo Erba) gas chromatograph equipped with a flame
ionization detector and a column of 25 m in length; the tem-
perature was varied within 50—280 °C by heating the column
with a rate of 8 deg min–1; helium was used as a carrier gas with
a flow rate of 30 mL min–1. Mass spectra were obtained using
a Crystal-5000 М mass spectrometer under the following condi-
tions: a 30 m capillary column, temperature increase from 80 to
280 °C with a rate of 20 deg min–1, helium as a carrier gas, the
transition line and ion source temperatures were 300 °C. 1H and
13C NMR spectra were recorded using a Bruker Avance-500
NMR spectrometer (500 MHz, 1H; 125 MHz, 13C) in CDCl3.
Synthesis of acetals 3a—c (general procedure). Acetals 3a—c
were prepared according to a published method.6 A mixture
containing one of alcohols 1а,b (0.1 mol), the corresponding
carbonyl compound of 2а—с (0.3 mol), benzene (80 mL) and
KU-2 (Н+) (3 g) were stirred at 80 °С until the calculated amount
of water (1.8 mL) was collected in the Dean—Stark head. At the
end of the reaction, the mixture was washed with water until
neutral, dried with calcium chloride; the salt was filtered out;
1
Yield 9%. B.p. 40 °C (20 Torr). A colorless liquid. Н NMR
(CDCl3), δ: 0.87 (t, 3 Н, С(3)Н3, J = 7.0 Hz); 1.37 (d, 2 Н,
2 С(9)На, J = 8.0 Hz); 1.45 (t, 2 Н, 2 С(9)Нb, J = 7.0 Hz);
1.60—1.66 (m, 2 Н, С(6)Н2); 1.72 (dd, 1 Н, С(8)Н, J = 6.0 Hz,
J = 7.0 Hz); 3.95 (d, 2 Н, 2 С(4,5)На, J = 7 Hz); 4.04 (t, 2 Н,
С(4,5)Нb, J = 6.4 Hz). 13С NMR (CDCl3), δ: 9.45 (С(3)H3);
27.49 (С(6)Н2); 30.11 (С(9)Н2); 39.56 (С(8)Н); 66.49 (С(10));
69.29 (С(4,5)Н2); 109.00 (С(11)). MS (EI), m/z (Iотн (%)): 211 (5),
213 (3), 215 (2) [М]+; 109 (15), 111 (7), 113 (5) [C3H4Cl2]+;
123(30), 125(18), 127(7)[M–C2H5–2CH2O]+;73[C3H5O2]+ (100).
8,8-Dichloro-4-isopropyl-3,5-dioxabicyclo[5.1.0]octane (4c).
Yield 98%. B.p. 113 °C (2 Torr). A colorless liquid. The spectral
data corresponds to reported ones.6
1,1-Dichloro-2,3-bis(hydroxymethyl)cyclopropane (4d). B.p.
144 °С (3 Torr). A colorless liquid gradually solidifying at room

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Russ. Chem. Bull., Int. Ed., Vol. 70, No. 3, March, 2021
temperature. Compound 4d was prepared according to a published
method.5 Compound 4с (0.05 mol) was stirred for 6 h in a 2.0 M solu-
tion of HCl (100 mL). The reaction was carried out until complete
conversion of the starting compound. The solvent was evaporated
in vacuo, the residue was dissolved in ethyl acetate and filtered
to remove insoluble components. The solvent was evaporated.
Crystallization of the oily residue from a CHCl3—petroleum
ether mixture gave the product. Physicochemical constants of
thus obtained compound 4d correspond to the published data.6
1,1-Dichloro-2,3-bis(chloromethyl)cyclopropane (4е). Yield
83%. B.p. 112 °С (5 Torr). A colorless liquid. Compound 4е was
prepared according to a known method.14 Thionyl chloride
(0.012 mol) was added to a mixture of compound 4d (0.008 mol)
and pyridine (0.008 mol) at 0 °С. The reaction mixture was stirred
at 10—12 °С until the sulfur dioxide release was finished (5 h). Then
chloroform (30 mL) was added, and the mixture was washed with water
with caution, avoiding effervescence due to hydrolysis of thionyl
chloride. The residue was distilled. Physicochemical constants
of thus obtained compound 4е correspond to the published data.6
Assessment of cytotoxic characteristics of the obtained com-
pounds in vitro. In the study of the cytotoxicity of the compounds,
the following tumor cell lines were used: HepG2 (human hepato-
cellular carcinoma), SH-SY5Y (human neuroblastoma), A549
(human lung adenocarcinoma), MCF-7 (adenocarcinoma of the
human breast duct), and Jurkat (T-lymphoblastic leukemia), as
well as the HEK293 cell culture of normal origin (immortalized
human embryonic kidney cells). All cell lines were obtained from
Russian cell culture collection (Institute of Cytology of the
Russian Academy of sciences, Saint Petersburg). Cells of lines
HEK293 (25•103 cells per well), HepG2 (15•103 cells per well),
SH-SY5Y (50•103 cells per well), MCF-7 (12•103 cells per well),
A549 (10•103 cells per well) were seeded in 96 well plates filled
with the DMEM cell culture medium (100 μL in a well) contain-
ing a 10% fetal bovine serum solution (FBS, Gibco, USA),
test was used to determine the significance of differences in the
IC50 values obtained for cells of normal and tumor origin using
the test compounds.
This work was carried out under financial support of
the Council for Grants of the President of the Russian
Federation (the Program of governmental support of young
scientists PhD and DSc, Project No. MK-1689.2020.3)
and within the framework of the state tasks of Institute of
Biochemistry and Genetics of the Ufa Federal Research
Centre of the Russian Academy of Sciences (Project
No. АААА-А16-116020350033-8).
This paper does not contain descriptions of studies on
animals or humans.
The authors declare no competing interests.
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Received November 27, 2020;
in revised form January 18, 2021;
accepted January 20, 2021