Synthesis and Estimation of Radical Scavenging Activity of Tetra(meso-aryl)porphyrins Containing 2,6-Dimethoxyphenol Unit

Article abstract of DOI:10.1134/S1070363218080145

Tetra(meso-aryl)porphyrins containing 2,6-dimethoxyphenol unit distant from the macrocycle and adjacent to it have been prepared. Radical scavenging activity of the obtained compounds has been estimated in the model reaction of ethylbenzene oxidation initiated by azobisisobutyronitrile. It has been shown that the phenol hydroxy group ability to inhibit ethylbenzene oxidation depends on the environment of phenol group.

Full text of DOI:10.1134/S1070363218080145

ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 8, pp. 1635–1640. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © T.K. Rocheva, L.I. Mazaletskaya, N.I. Sheludchenko, D.V. Belykh, 2018, published in Zhurnal Obshchei Khimii, 2018, Vol. 88,
No. 8, pp. 1314–1319.
Synthesis and Estimation of Radical Scavenging Activity
of Tetra(meso-aryl)porphyrins
Containing 2,6-Dimethoxyphenol Unit
T. K. Rochevaa*, L. I. Mazaletskayab, N. I. Sheludchenkob, and D. V. Belykha
a Institute of Chemistry, Komi Scientific Center, Ural Branch, Russian Academy of Sciences,
ul. Pervomaiskaya 48, Syktyvkar, 167000 Russia
*e-mail: tatyanrocheva@yandex.ru
b Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
Received April 5, 2018
Abstract―Tetra(meso-aryl)porphyrins containing 2,6-dimethoxyphenol unit distant from the macrocycle and
adjacent to it have been prepared. Radical scavenging activity of the obtained compounds has been estimated
in the model reaction of ethylbenzene oxidation initiated by azobisisobutyronitrile. It has been shown that the
phenol hydroxy group ability to inhibit ethylbenzene oxidation depends on the environment of phenol group.
Keywords: tetra(meso-aryl)porphyrins, substituted phenols, radical scavenging activity, stoichiometric
inhibition coefficients, inhibited oxidation of ethylbenzene
DOI: 10.1134/S1070363218080145
Free radical oxidation as a controlled process and
indispensable part of living organisms functioning
[1–6] includes many reactions involving different
radicals and so-called reactive oxygen species. Free
radicals play an important part in normal cell
metabolism, being involved in oxidative phosphoryla-
tion, biosynthesis of prostaglandins and nucleic acids,
regulation of lipid metabolism, and mythos processes.
The formation of free radicals in excessive
concentrations results in disorganization of all cellular
structures, disorder of their functional activity, and cell
death [7, 8]. In living organisms, complex antioxidant
system exists which protects from radical damage; it
includes enzymes (catalase, glutathione peroxidase,
and superoxide dismutase), chelators for transition
metals (albumin, ferritin, and ceruloplasmin), melatonin,
amino acids, glutathione, peptides, certain vitamins
and hormones [2, 9–12]. Disorders in antioxidant
system may be compensated by the introduction of
exogenic antioxidants [1].
sites which can inhibit oxidation processes via diverse
ways and exhibit intramolecular synergic effect [1, 13,
14]. Tetra(meso-aryl)porphyrins which contain substi-
tuents enhancing the radical scavenging activity (RSA)
form a prospective class of such compounds [15–22].
Sub-stituted phenols are widely used antioxidants;
their efficiency increases with the increase in the
number of electron-donor substitutes in ortho- or para-
positions with respect to ОН-group.
We have earlier obtained a series of tetra(meso-
aryl)porphyrins containing a phenol hydroxy group at
one of aromatic substitutes and analogous compounds
containing a methoxy group [15]. Their investigation
has shown that compounds containing a phenol hyd-
roxy group in para-position with respect to the
macrocycle exhibit high RSA. The presence of 2,6-
dimethoxyphenol unit in a hybrid macromolecule
provides significant RSA; the +М-effect of two
methoxy groups increases the activity of phenol
hydroxy group despite its involvement in
intramolecular hydrogen bond [15]. Hence, the
investigation of the influence of the porphyrin part
structure of the hybrid molecule on the RSA is
important.
One of the interesting modern directions is syn-
thesis of hybrid antioxidants – molecules which exhibit
antioxidant activity and are at the same time capable of
targeted delivery and structural interactions with the
biosystem [2], or molecules containing several reaction
1635

1636
ROCHEVA et al.
Scheme 1.
X
OH
MeO
OMe
+
+
N
H
CHO
CHO
OMe
HO
X
3'
X
4''
5''
X
4'
2'
6''
MeO
3''
5'
1'
5
10
6'
1''
2''
N
H
N
H
α
β
а, b
N
+
N
N
N
H
N
H
N
20
15
X
X
X
X
1, 2
3, 4
X = OCH3 (1, 3), H (2, 4).
a, EtCOOH, reflux, 1 h; b, air oxidation, 5 days.
Herein we report the synthesis of tetra(meso-aryl)
porphyrins with a 2,6-dimethoxyphenol unit directly
bonded with porphyrin macrocycle and connected to it
via a spacer; RSA of the prepared compounds has been
estimated.
starting porphyrin 7 conversion 73%. Compound 9
was obtained as a side product. According to data from
[23, 24], analogous product is formed in the reaction of
DMF, acyl chlorides (acting as a dehydrating agent),
and aromatic amines.
The structure of porphyrins 1, 2, 8, and 9 was con-
firmed by means of IR, electronic, and NMR spec-
troscopy as well as mass spectrometry. The mass
spectra of the prepared compounds contained peaks
with m/z corresponding to the protonated molecular
ions [М + Н]+. The Soret band and the absorption band
characteristic of tetra-meso-substituted porphyrin
chromophore were observed in the electron absorption
Asymmetrically substituted porphyrins 1 and 2
were synthesized via mixed-aldehyde–tetrapyrrole
condensation of 4-hydroxy-3,5-dimethoxybenzalde-
hyde with 4-methoxybenzaldehyde (compound 1) and
benzaldehyde (compound 2) during refluxing in
propionic acid followed by oxidation with air (Scheme 1).
Symmetrically substituted tetra(meso-aryl)porphyrins
3 and 4 were isolated as well as target products 1 and 2.
1
spectra. The Н NMR spectra of compounds 1, 2, 8
Compound 8 containing a phenol antioxidant
moiety distant from the macrocycle was prepared via
the reaction of 5-(4'-aminophenyl)-10,15,20-triphenyl-
porphin 7 with 4-hydroxy-3,5-dimethoxybenzoyl chlo-
ride 6 (prepared via the reaction between thionyl
chloride and acid 5) (Scheme 2). To optimize the
conditions of the synthesis of compound 8, we varied
the molar ratio of compounds 6 and 7. The use of three-
fold excess of the acylation agent 6 was found optimal.
The yield of the acylation product 8 was 43% at the
and 9 contained proton signals of the porphyrin macro-
cycle (Hβ-pyrrole and transannular NH-protons) and of
1
the aromatic substitutes. The H NMR spectrum of
compound 9 contained the signals of methyl groups
(δH 3.25 ppm) and of the proton at carbon atom of
imine group (δH 7.99 ppm) of the formamide unit. The
13C NMR spectrum contained carbon signals of
syringic acid unit methoxy groups at δС 55.61, 56.61,
and 56.74 ppm for porphyrins 1, 2, and 8, respectively.
The IR spectra of porphyrins 1, 2, and 8 contained the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 8 2018

SYNTHESIS AND ESTIMATION OF RADICAL SCAVENGING ACTIVITY
1637
Scheme 2.
Me
N
Me _H2O
O
H
OMe
HO
4''
Me
2''
1''
Me N
O
MeO
H
H2N
HN
N
3'
5''
4''
3''
2'
1'
2'
1'
6''
10
3'''
Ph
Ph
5
5
10
N
15
1''
6'
1'''
OH
2'''
2''
N
H
N
H
N
H
α
α
MeO
OMe
β
β
b
N
+
N
N
N
+
N
H
N
H
N
H
N
COCl
20
20
15
Ph
Ph
Ph
Ph
Ph
6
7
8
9
a
OH
MeO
OMe
COOH
5
a, CH2Cl2, SOCl2, reflux, 1 h; b, CH2Cl2, DMF, reflux, 1 h.
w0/w – w/w0 = fkinh·c0/kr0.5·wi0.5
,
(2)
absorbance bands corresponding to the stretching of
phenol О–Н bond as well as of the porphyrin macro-
cycle N–H bond.
where w0 and w are the rate constants in the absence
and in the presence of antioxidant addition, respect-
tively; kr is the rate constant of bimolecular peroxy
radicals recombination.
The inhibiting activity of phenol-substituted por-
phyrins was investigated using a model reaction of
oxidation of ethylbenzene initiated by azobisisobutyro-
nitrile. The initial rate of oxygen absorption (w) in the
presence of an antioxidant was determined from the
kinetic curves. The stoichiometric inhibition coef-
ficient (f) was determined from the induction period
value (τ) using Eq. (1):
According to data listed in the table, RSA (f and
kinh) of the studied compounds depended on the
substitution of the porphyrin cycle and phenol unit.
Compound 1 containing additional methoxy sub-
stituents at the phenyl groups, in contrast to compound
2, showed the higher rate constant of the reaction with
free radicals. The fkinh values for compounds 1 and 2
differed by 1.2 times at equal f = 2 values.
f = τ·wi/c0,
(1)
where wi is the initiation rate, c0 is the antioxidant
concentration.
Similar increase in the kinh constant caused by the
introduction of additional alkoxy groups at the phenyl
moiety has been previously observed in our studies of
porphyrin derivatives containing phenol unit with the
The rate constants of the reaction of antioxidant
with peroxy radicals (kinh) was determined by plotting
the kinetic data in coordinates of Eq. (2):
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 8 2018

1638
ROCHEVA et al.
Stoichiometric inhibition coefficients (f) and inhibition
parameters (fkinh) at 333 K
initiator of free radicals, the initiation rate wi was
5×10–8 mol L–1 s–1. Ethylbenzene with a dissolved
antioxidant was pre-thermostated. After that an initiator
additive was added. The oxygen absorption kinetics
was measured with a volumetric unit .
Inhibitor
f
fkinh×10–4, L mol–1 s–1
1
2
8
2.0
2.0
1.6
9.4
7.7
2.6
5-(4'-Hydroxy-3',5'-dimethoxyphenyl)-10,15,20-
tri(4''-methoxyphenyl)porphin (1). A solution of 4-hyd-
roxy-3,5-dimethoxybenzaldehyde (0.20 g, 1.10 mmol),
4-methoxybenzaldehyde (0.79 mL, 6.50 mmol), and
pyrrole (0.52 mL, 7.50 mmol) in 20 mL of propionic
acid was added to 15 mL of boiling propionic acid.
The reaction mixture was refluxed for 0.5 h, kept at
room temperature for 5 days in air, and diluted with
chloroform (50 mL). Propionic acid and other water-
soluble impurities were washed out with water to
neutral reaction of the washings. The solution was
dried over anhydrous sodium sulfate; the solvent was
distilled off under reduced pressure. The obtained
mixture of porphyrins 1 and 3 was separated using
column chromatography on alumina. Yield 0.017 g
(2%), purple crystal powder, Rf 0.76 (eluent―
chloroform). IR spectrum (KBr), ν, cm–1: 3537 (OH),
3318 (NH), 2837 (OCH3), 2933, 1607 (С=С), 1508,
OH-group in meta-position with respect to porphyrin
cycle, other substituents being absent [15].
Introduction of an electron acceptor group at the p-
position of the phenol unit (compound 8) resulted in
the increase in the fkinh parameter by about 3 times
compared with compound 2 and by 3.6 times com-
pared with compound 1. At the same time, the
decrease in the stoichiometric coefficient to f = 1.6 was
observed.
In summary, tetra(meso-aryl)porphyrins containing
2,6-dimethoxyphenol unit distant from the macrocycle
(compound 8) and directly bonded to it (compounds 1
and 2) were prepared, and their RSA was determined
using a model reaction of ethylbenzene oxidation
initiated by azobisisobutyronitrile at 333 K in air. The
prepared porphyrins exhibited RSA depending on the
substitution at the porphyrin macrocycle and phenol
unit. Introduction of methoxy groups at the phenyl
substituents of porphyrin accelerated its reaction with
free radicals; the presence of electron acceptor group
in the para-position of the phenol unit gave the
opposite effect. In the latter case, the stoichiometric
inhibition coefficient was reduced.
1
1468, 1350, 1213, 1111, 972, 802, 735, 700. Н NMR
spectrum (CDCl3), δH, ppm: –2.71 br.s (2H, NH), 4.05
s (6H, 5-ArOCH3), 4.14 s (9H, 10,15,20-ArOCH3),
5.91 s (1H, 5-ArOH), 7.33 d (6H, 10,15,20-ArH3'',5''
,
JHH = 8.2 Hz), 7.52 s (2H, 5-ArH2',6'), 8.16 d (6H,
10,15,20-ArH2'',6'', JHH = 8.3 Hz), 8.91 br.s (6Н,
H2,8,12,13,17,18), 8.96 d (2Н, H3,7, JHH = 4.6 Hz). 13С
NMR spectrum (CDCl3), δC, ppm: 55.61 (10,15,20-
ArOCH3), 56.60 (5-ArOCH3), 112.24 (10,15,20-
ArC3'',5''), 112.42 (5-ArC2',6'), 119.73, 119.84, 119.96
(С5,10,15,20), 129.89–131.75 (Cα,β), 133.48 (5-ArC3',5'),
134.61 (10,15,20-ArC2'',6'',-ArC4'), 135.56 (10,15,20-
ArC4''), 145.36 (5-ArC1'), 159.46 (10,15,20-ArC1'').
EAS (CH2Cl2), λmax, nm (I, %): 649.5(1), 593.0(1),
555.0(2), 517.5(3), 422.5(100). Mass spectrum (ESI),
m/z: 781.4 [M + H]+ (calculated for C49H41N4O6:
781.3).
EXPERIMENTAL
The IR spectra were recorded using an IR Prestige
21 FTIR spectrometer in KBr pellets. The electronic
absorption spectra were registered using a Shimadzu
UV-1700 spectrometer in 10 mm quartz cells with
1
chloroform or dichloromethane as referrence. The Н
and 13C NMR spectra were recorded using a Bruker
Avance II spectrometer (300 and 75 MHz) in CDCl3.
Mass spectra (ESI) were registered using a Thermo
Finnigan LCQ Fleet device. The reaction course was
monitored by thin layer chromatography on Sorbfil
plates. Aluminum oxide (40/200 µm, “pure” grade)
was used for column chromatography.
5-(4'-Hydroxy-3',5'-dimethoxyphenyl)-10,15,20-
triphenylporphin (2) was prepared as described in
[15]. Purple crystal powder, Rf 0.33 (eluent―tetra-
chloromethane–acetone, 10 : 1).
5,10,15,20-Tetra(meso-methoxyphenyl)porphin (3).
Yield 0.035 g (3%), purple crystal powder, Rf 0.32
(eluent―tetrachloromethane–acetone, 100
Spectral characteristics were identical to those reported
in [25].
:
1).
RSA was estimated in a model reaction of the ethyl-
benzene initiated oxidation at 333 K in an air atmo-
sphere. Dinitrile of azoisobutyric acid was used as the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 8 2018

SYNTHESIS AND ESTIMATION OF RADICAL SCAVENGING ACTIVITY
1639
5-(4'-Aminophenyl)-10,15,20-triphenylporphin (7)
was prepared as described in [26]. Purple crystal
powder, Rf 0.53 (eluent―tetrachloromethane–acetone,
5 : 1).
1697, 1636 (С=N), 1074 (H3C–N), 1518, 1469, 1350,
1180, 1026, 968, 800, 731. 1Н NMR spectrum
(CDCl3), δH, ppm: –2.71 br.s (2H, NH), 3.25 s [6H,
N(CH3)2], 7.52 d (2Н, 5-ArH3',5', JHH = 8.2 Hz), 7.80
br.s (9H, 10,15,20-PhH3'', 4'',5''), 7.99 s (1H, N=CHN),
8.17 d (2Н, 5-ArH2',6', JHH = 8.2 Hz), 8.26 d (6H,
10,15,20-PhH2'',6'', JHH = 5.5 Hz), 8.88 br.s (6Н,
H2,8,12,13,17,18), 8.93 d (2H, H3,7, JHH = 4.6 Hz). 13С
NMR spectrum (CDCl3), δC, ppm: 38.25 (CH3), 119.48
(5-ArC3',5'), 120.02 and 120.86 (С5,10,15,20), 126.67
(10,15,20-PhC3'',5''), 127.68 (10,15,20-PhC4''), 130.47–
131.83 (Cα,β), 134.58 (10,15,20-PhC2'',6''), 135.53 (5-
ArC2',6', 5-ArC4'), 138.65 (5-ArC1'), 142.30 (10,15,20-
PhC1''), 151.52 (N=CH). EAS (CH2Cl2), λmax, nm (I,
%): 647.0(1), 590.0(1), 551.5(1), 515.5(4), 419.0(100).
Mass spectrum (ESI), m/z: 685.8 [M + H]+ (calculated
for C47H37N6: 685.3).
Acylation of porphyrin 7. A mixture of 4-hydroxy-
3,5-dimethoxybenzoic acid (0.03 g, 0.15 mmol) and
thionyl chloride (0.04 mL, 0.61 mmol) in di-
chloromethane was refluxed for 1 h. The solvent and
volatile components were removed under reduced
pressure. Dichloromethane (7 mL), dimethylform-
amide (0.1 mL), and a solution of porphyrin (0.03 g,
0.05 mmol) in dichloromethane (20 mL) were added to
the obtained acyl chloride. The reaction mixture was
refluxed for 1 h and then cooled down. Dilute
hydrochloric acid (1 : 10) was added. The mixture was
washed with water to neutral reaction of the washings.
The obtained solution was dried over anhydrous
sodium sulfate; the solvent was removed under
reduced pressure. The reaction products were separated
using column chromatography on alumina (eluent―
tetrachloromethane, chloroform, chloroform–ethanol,
10 : 1). Porphyrins 7 (0.008 g, conversion 73%), 8
(0.012 g, 43%), and 9 (0.010 g, 42%) were isolated.
ACKNOWLEDGMENTS
This study was financially supported by the Russian
Foundation for Basic Research (project no. 16-33-
00309mol_a) and performed using the equipment of
Center for Collective Usage “Chemistry” of Institute
of Chemistry, Komi Scientific Center, Ural Branch,
Russian Academy of Sciences.
5-[4'-(N-4''-Hydroxy-3'',5''-dimethoxy)benzoyl-
amino]phenyl-10,15,20-triphenylporphin (8). Purple
crystal powder, Rf 0.15 (eluent―tetrachloromethane–
acetone, 5 : 1). IR spectrum (KBr), ν, cm–1: 3502
(OH), 3318 (NH), 2870 (CH3), 2955, 1597 (С=С),
1498, 1467, 1333, 1240, 1182, 1030, 966, 800, 733. 1Н
NMR spectrum (CDCl3), δH, ppm: –2.73 br.s (2H,
NH), 4.10 s (6H, OCH3), 5.96 s (1H, 5-ArOH), 7.33 s
(2H, ArH2'',6''), 7.81 br.s (9H, 10,15,20-PhH3''',4''',5'''),
8.08 d (2Н, 5-ArH3',5', JHH = 8.2 Hz), 8.12 s (1Н, NH),
8.25–8.29 m (8H, 5-ArH2',6',10,15,20-PhH2''',6'''), 8.89
br.s (6Н, H2,8,12,13,17,18), 8.93 d (2Н, H3,7, JHH = 4.6 Hz).
13С NMR spectrum (CDCl3), δC, ppm: 56.74 (OCH3),
104.54 (ArС2'',6''), 118.41(5-ArC3',5'), 120.20(С5,10,15,20),
126.70(10,15,20-PhC3''',5'''),.74 (10,15,20-PhC4'''),
CONFLICT OF INTERESTS
Autor declare no conflict of interest.
REFERENCES
1. Burlakova, E.B., Ross. Khim. Zh., 2007, vol. 51, no. 1,
p. 3.
2. Kuchin A.V. and Chukicheva, I.Yu., Vestn. Ural. Otd.
Ross. Akad. Nauk, 2011, vol. 37, no. 3, p. 43.
3. Milaeva, E.R., J. Inorg. Biochem., 2006, vol. 100,
p. 905. doi 10.1016/j.jinorgbio.2006.02.014
4. Fedorova, T.N., Boldyrev, A.A., and Gannushkina, I.V.,
Biokhim., 1999, vol. 64, no. 1, p. 94.
5. Black, H.S., Frontiers in Bioscience, 2002, no. 7, p. 1044.
130.51–131.93 (Cα,β), 134.57, 135.23 (5-ArC2',6'
,
10,15,20-PhC2''',6''', 5-ArC4'), 137.79 (5-ArC1'), 138.38 и
138.55 (ArС1'', ArС4''), 142.19 (10,15,20-PhC1'''),
147.18 (ArC3'',5''), 165.80 (NHCOAr). EAS (CH2Cl2),
6. Men’shchikova, E.B., Zenkov, N.K., Lankin, V.Z.,
Bondar’, I.A., Krugovykh, N.F., and Trufakin, V.A.,
λ
max, nm (I, %): 645.5(1), 591.0(1), 551.5(1), 516.0(3),
Okislitel’nyi stress. Prooksidanty
i
antioksidanty
419.5(100). Mass spectrum (ESI), m/z: 810.5 [M + H]+
(Oxidative Stress. Prooxidants and Antioxidants), Moscow:
Slovo, 2006.
(calculated for C53H40N5O4: 810.3).
5-[4'-(N,N-Dimethylformamidino)phenyl]-10,15,20-
triphenylporphin (9). Purple crystal powder, Rf 0.25
(eluent―tetrachloromethane–acetone, 5 : 1). IR spec-
trum (KBr), ν, cm–1: 3318 (N–H), 2924, 1595 (С=С),
7. Chesnokova, N.P., Ponukalina, E.V., and Bizenkova, M.N.,
Sovr. Naukoemk. Tehknol., 2006, no. 6, p. 28.
8. Chesnokova, N.P., Morrison, V.V., Ponukalina, E.V.,
Afanas’eva, G.A., Bizenkova, M.N., Barsukov, V.Yu.,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 8 2018

1640
ROCHEVA et al.
19. Gerasimova, O.G., Milaeva, E.R., Shpakovskii, D.B.,
Morozova, O.L., Polutova, N.V., and Zhevak, T.N.,
Semeikin, A.S., and Syrbu, S.A., Russ. Chem. Bull.,
2007, vol. 56, no. 4, p. 831. doi 10.1007/s11172-007-
0124-y
Fund. Issled., 2009, no. 5, p. 122.
9. Tregubova, I.A., Kosolapov, V.A., and Spasov, A.A.,
Usp. Fiziol. Nauk, 2012, vol. 43, no. 1, p. 75.
20. Tyurin, V.Yu., Jingwei, Z., Moiseeva, A.A., Milaeva, E.R.,
Belykh, D.V., Buravlev, E.V., Rocheva, T.K.,
Chukicheva, I.Yu., and Kuchin, A.V., Doklady Chem.,
2013, vol. 450, no. 2, p. 152. doi 10.1134/
S0012500813060025
21. Rocheva, T., Tyurin, V., Belykh, D., Moiseeva А.,
Zhang, J., Buravlev Е., Chukicheva, I., Kutchin А., and
Milaeva, E., Am. J. Anal. Chem., 2014, vol. 5, no. 15,
p. 1028. doi 10.4236/ajac.2014. 515109
22. Rocheva, T.K., Buravlev, E.V., Mazaletskaya, L.I.,
Sheludchenko, N.I., Belykh, D.V., Chukicheva, I.Yu.,
and Kutchin, A.V., Macroheterocycles, 2014, no. 7(3),
p. 262. doi 10.6060/mhc140479b
23. Mekhalfia, A., Mutter, R., Heal, W., and Chen, B.,
Tetrahedron, 2006, vol. 62, p. 5617. doi 10.1016/
j.tet.2006.03.099.
10. Byshevskii, A.Sh. and Shapovalova, E.M., Vestn.
YuUrGU, Ser. Obrazovanie, Zdravookhran. Fiz.
Kul’tura, 2009, no. 27 (160), p. 77.
11. Tolpygina, O.A., Byull. Vostochno-Sibirskogo Nauch.
Tsentra SO RAMN, 2012, no. 2, p. 178.
12. Bessonova, L.O., Verlan, N.V., and Kolesnichenko, L.S.,
Sib. Med. Zh., 2008, vol. 81, no. 6, p. 19.
13. Burlakova, E.B., Molochkina, E.M., and Nikiforov, G.A.,
Oxid. Commun., 2008, vol. 31, no. 4, p. 739.
14. Zhang, H.Y., Yang, D.P., and Tang, G.Y., Drug
Discovery Today, 2006, vol. 11, no. 15 (16), p. 749.
15. Rocheva, T.K., Shevchenko, O.G., Mazaletskaya, L.I.,
Sheludchenko, N.I., and Belykh, D.V., Macro-
heterocycles, 2018, no. 11(1), p. 95. doi 10.6060/
mhc170302b
16. Antonova, N.A., Osipova, V.P., Kolyada, M.N.,
Movchan, N.O., Milaeva, E.R., and Pimenov, Yu.T.,
Macroheterocycles, 2010, no. 3(2–3), p. 139.
24. Delarue, S. and Sergheraert, C., Tetrahedron Lett.,
1999, vol. 40, p. 4587. doi 10.1016/S0040-4039(99)
01054-0
25. Momo, P.B., Bellete, B.S., Brocksom T, J., de Souza, O.M.A.,
and de Oliveir, K.T., RSC Adv., 2015, vol. 5, p. 84350.
doi 10.1039/C5RA16962C
26. Luguya, R., Jaquinod, L., Fronczek, F.R., Vicente, M.G.H.,
and Smith, K.M., Tetrahedron, 2004, vol. 60, p. 2757.
doi 10.1016/j.tet.2004.01.080
17. Mukhatova, E.M., Limonova, N.T., Kolyada, M.N.,
Osipova, V.P., Berberova, N.T., Pimenov, Yu.T., and
Milaeva, E.R., Macroheterocycles, 2011, no. 4(3),
p. 216.
18. Milaeva, E.R., Shpakovsky, D.B., and Petrosyan, V.S.,
Macromol. Symp., 2003, vol. 204, p. 191.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 8 2018