SYNTHESIS AND CYTOTOXICITY OF DIBENZO[(γ-ARYL)PYRIDINO]AZA-17-CROWN-5 ETHERS Текст научной статьи по специальности «Биотехнологии в медицине»

Crown Ethers

Краун-эфиры

Макрогэтероцмклы

http://macroheterocycles.isuct.ru

Paper

Статья

DOI: 10.6060/mhc170406a

Synthesis and Cytotoxicity of Dibenzo[(y-aryl)pyridino]aza-17-crown-5 Ethers

Le Tuan Anh,@a Nguyen T. Thanh Phuong,a Truong Hong Hieu,b Anatoly T. Soldatenkov,c Bui T. Van,a Tran T. Thanh Van,a Dao T. Nhung,a Leonid G. Voskressensky,c To Hai Tung,a and Victor N. Khrustalevcd

aDepartment of Pharmaceutical Chemistry, Faculty of Chemistry, VNU University of Science, 100000 Hanoi, Vietnam

bDepartment of Biotechnology, Vietnam-Russia Tropical Centre, 100000 Hanoi, Vietnam

cFaculty of Science, Peoples' Friendship University of Russia, 117198 Moscow, Russian Federation

dX-Ray Structural Centre, A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991

Moscow, Russian Federation

@Corresponding author E-mail: huschemical.lab@gmail.com

For the development of new anticancer agents, dibenzo[(y-aryl)pyridino]aza-17-crown-5 ethers containing 2,4,6-triarylpyridine were synthesized successfully by one-step domino-condensation of 1,8-bis(2-acetylphenoxy)-3,6-dioxaoctane, arylaldehydes and ammonium acetate according to the conditions of Hantzsch reactions. The synthesized y-arylpyridine derivatives show high cytotoxic activity against human cancer cell lines: Hep-G2, RD, FL, Lu1. Compounds (3b,c) showed significant cytotoxicity against all four human cell lines whereas the similar synthesized compound (3d) possessed cytotoxicity against HepG2, Lu1 and RD cell lines. Meantime, both compounds (3f,g) containing y-heteroaryl only exhibited cytotoxicity against RD and FL cell lines. Azacrown ethers (3b-d) exhibited low activity on the Vero cell line, meaning that they can be evaluated for their potential as promising anticancer agents. X-Ray structure study was performed to determine the structure of the representative compound 3a.

Keywords: Arylpyridine, azacrown ethers, cytotoxicity, anticancer agent, Hantzsch reaction, X-ray analysis.

Синтез и цитотоксичность дибензо[(у-арил)пиридино]аза-17-краун-5-эфиров

Л. Т. Ань®* Н. Т. Т. Фыонг,а Т. Х. Хиеу,ъ А. Т. Солдатенков,с Б. Т. Ван,а Т. Т. Т. Ван,а Д. Т. Нунг,а Л. Г. Воскресенский,с Т. Х. Тунг,а В. Н. Хрусталев^

^Кафедра фармацевтической химии, Факультет химии, Университет науки, Вьетнамский национальный университет, 100000 Ханой, Вьетнам

ъФакультет биотехнологии, Российско-Вьетнамский Тропический центр, 100000 Ханой, Вьетнам °Российский университет дружбы народов, 117198 Москва, Российская Федерация

АЦентр рентгеноструктурных исследований, Институт элементоорганических соединений им. А.Н. Несмеянова РАН, 119991 Москва, Российская Федерация ®Е-таИ: huschemical.lab@gmail.com

Для разработки новых противоопухолевых агентов одностадийной доминоконденсацией 1,8-бис(2-ацетилфенокси)-3,6-диоксооктана, арилальдегидов и ацетата аммония по реакции Ганча были успешно синтезированы дибензо[(у-арил)пиридино]аза-17-краун-5-эфиры, содержащие 2,4,6-триарилпиридин. Синтезированные производные у-арилпиридина показали высокую цитотоксическую активность против линий раковых клеток человека: Hep-G2, RD, FL, Lu1. Соединения (3b, c) показали значительную цитотоксическую активность против всех четырех линий раковых клеток, а соединение (3d) - против линий HepG2, Lu1 и RD. Между тем, оба соединения (3f,g), содержащие у-гетероарил, проявили цитотоксичность только против линий RD и FL. Азакраун-эфиры (3b-d) проявили низкую активность на клеточной линии Vero, что позволяет оценить

их потенциал для использования в качестве перспективных противораковых агентов. Для определения структуры соединения 3a были проведены рентгеноструктурные исследования.

Ключевые слова: Арилпиридин, азакраун-эфиры, цитотоксичность, противораковый агент, реакция Ганча, рештеноструктурный анализ.

Introduction

Multi-substituted pyridine derivatives occupy a central position in modern heterocyclic chemistry, particularly in pharmaceutical, bioorganic and medicinal chemistry.[1-5] Due to these interesting biological properties, the synthesis of functionalized heterocycles containing y-arylpyridine fragment is one of the major objectives for various laboratories.^ In addition, several prepared (y-aryl)pyridinoaza-14-crown-4 ethers (1a-d) were evaluated as to their cytotoxicity to human cancer cell lines: Hepatocellular carcinoma (HepG2), Rhabdosarcoma (RD), Human Uterine (FL), Human Breast adenocarcinoma (MCF7), Human Prostate Cancer (PC3).[10-12] Base on these results of previous studies, it would be very interesting to evaluate the cytotoxicity of system aza-17-crown-5 ether. Due to its ability to form metal complexes and its status as an anticancer agent, azacrown ether has valuable applications.

In the past, a similar system containing a polyether bridge was also reported.[1314] The main drawbacks of these methods were multi-step synthesis, the amount of time spent for reactions, separation and purification. Here, in connection with published studies,[1011] we present a simple, one-pot domino Hantzsch-type reaction to obtain the desired compounds, namely dibenzo[(y-aryl)pyridino]aza-17-crown-5 ethers from arylaldehyde, 1,8-6/'s(2-acetylphenoxy)-3,6-dioxaoctane and ammonium acetate. The combination of y-arylpyridines and crown ether promises to bring a novel class of bioactive compounds.

Experimental

Reagents were purchased from commercial sources (Sigma-Aldrich) and were used without any additional purification. 'H and 13C NMR spectra were recorded in CDCl3 solutions at 25 °C, using a 500 MHz NMR spectrometer; chemical shifts are given

in parts per million (5) and referenced to the appropriate solvent residual peak. Mass spectra were recorded on LTQ Orbitrap XL using electrospray ionization source. IR spectra were recorded in FTIR Affinity - 1S SHIMADZU.

General method for synthesis of bis(benzo)(y-arylpyridino) aza-17-crown-5 ethers (3a-g). Equimolar amounts of 1,8-bis(2-acetylphenoxy)-3,6-dioxaoctane 2 (1.71 g, 5.00 mmol), aromatic aldehyde (5.00 mmol) and ammonium acetate (10 g, 13 mmol) were refluxed in acetic acid (50 ml). The reaction was monitored by TLC and was complete in 3h. The mixture was allowed to cool to room temperature and neutralized with sodium carbonate solution; then, the product was extracted with ethyl acetate (3x50 ml), drying over Na2SO4. After filtration, the solvent was evaporated in vacuo; the residue was first purified by column chromatography with a gradient elution of ethyl acetate/n-hexane affording the white solid which was then recrystallized from ethanol to obtain the pure azacrown ether product.

26-(4-Methoxyphenyl)-8,11,14,17-tetraoxa-28-azatetra-cyclo[22.3.1. 02 7.01823]pentacosa-2,4,6,18(23),20,22,24,2 7,1 (28)-nonaene (3a). Yield: 0.72 g (30 %), white crystals. M.p. 198199 °C (from EtOH). Rf=0.43 (n-hexane:ethylacetate=1:1). m/z (HRMS) Calc. for C30H30NO5+: 484.2118, found 484.2105 [M+H]+. IR (KBr) v cm-1: 160(5 (CN .H. ), 1545, 1514, 1492 (aromatic),

v ' max v pyridine-" ? ? v n

1182, 1120, 1058, 1029 (COC). 'H NMR (500 MHz, CDCl3, Me4Si) 5H ppm: 3.89 (s, 3H, Me), 3.19 (s, 4H, OCH2CH2), 3.62 (m, 4H, OCH2CH2), 4.10 (m, 4H, OCH2CH2), 6.98-7.02 (m, 4HAr), 7.12 (t, 2HAr, J=7.5 Hz), 7.35 (td, 2HAr, J= 7.5 Hz, 2 Hz), 7.64-7.68 (m, 4HJ, 7.72 (s, 2Hpyridiiie). 13C NMR (125 MHz, CDCy 5c ppm: 55.51, 69.56, 70.58, 71.16, 114.52, 114.62, 121.63, 121.95, 128.47, 129.67, 130.76, 131.35, 132.60, 146.77, 156.40, 156.94, 160.43.

26-(4-Methylphenyl)-8,11,14,17-tetraoxa-28-azatetracyclo [22.3.1.02,7.01823]pentacosa-2,4,6,18(23),20,22,24,27,1(28)-nonaene (3b). Yield: 0.9 g (40 %), white crystals. M.p. 156-156 °C (from EtOH). Rf=0.62 (n-hexane:ethylacetate=1:1). m/z (HRMS) Calc. for C30H30NO4+: 468.2175, found 468.2166 [M+H]+. IR (KBr) v cm-1: 1606 (CN .h. ), 1543, 1514, 1493 (aromatic), 1159,

max v pyridine-" 55 v 5

1122, 1056 (COC). 'H NMR (500 MHz, CDCl3, Me4Si) 5H ppm: 2.42 (s, 3H, Me), 3.18 (s, 4H, OCH2CH2), 3.62 (m, 4H, OCH2CH2), 4.10 (m, 4H, OCH2CH2), 6.99 (d, 2HAi, J=8.5 Hz), 7.11 (td, 2HAi, J=7.5 Hz, 1 Hz), 7.29 (d, 2HAr, J=8.5 Hz), 7.35 (td, 2HAi, J=8.0 Hz, 2 Hz), 7.62 (d, 2HAi, J=8.5 Hz), 7.65 (dd, 2HAi, J=7.5 Hz, 1.5 Hz),

CI

О (la)

RD (IC50 1.89 ng/ml)

О (lb)

HepG2 (IC50 2.79 |Jg/ml) MCF7 (IC50 4.56 (ig/ml) RD (IC50 1.46 (ig/ml) FL(IC501.51 ng/ml)

О (lc)

HepG2 (IC50 4.367 ng/ml) MCF7 (IC50 1.977 (jg/ml) PC3 (IC50 4.063 (J.g/ml) RD(IC5o 4.113 ng/ml)

О (Id)

MCF7 (IC50 4.78 ng/ml)

7.75 (s, 2Hpyridine). 13C NMR (125 MHz, CDCl3) 5C ppm: 14.4, 19.4,

33.7, 55.8, T0L6, 113.0, 115.9, 116.5, 119.0, 119.6, 128.0, 145.0, 146.3, 156.0.

26-(4-Hydroxyphenyl)-8,11,14,17-tetraoxa-28-azatetracyclo [22.3.1.027.01823]pentacosa-2,4,6,18(23),20,22,24,27,1(28)-nonaene (3c). Yield: 0.58 g (25 %), white crystals. M.p. 140-141oC (from EtOH). Rf=0.40 (hexane:ethylacetate=1:1). m/z (HRMS) Calc. for C29H28NO5+: 470.1967, found 470.1950 [M+H]+. IR (KBr) v cm-1: 3240 (OH), 1608 (CN ... ), 1593, 1547, 1493 (aromatic),

max v v pyridine-" 5 5 v

1159, 1122, 1056 (COC). 'H NMR (500 MHz, CDCl3, Me4Si) 5H ppm: 3.19 (s, 4H, OCH2CH2), 3.62 (m, 4H, OCH2CH2), 4.10 (m, 4H, OCH2CH2), 6.93 (d, 2HAr, J=8.5 Hz), 6.98 (d, ^HAr, J=8.0 Hz),

7.11 (t, 2HAr, J=8.5 Hz), 7.35 (td, 2HAr, J=8.5 Hz, 1.5 Hz), 7.62 (d, 2HAr, J=8.5 Hz), 7.64 (dd, 2HAr, J=8.5 Hz, 1.5 Hz), 7.71 (s, 2Hpyridine). 13C NMR (125 MHz, CDCl3) 5C ppm: 14.4, 19.4, 33.7,

55.8, ' 101.6, 113.0, 115.9, 116.5, 119.0, 119.6, 128.0, 145.0, 146.3, 156.0.

26-(2-Methoxyphenyl)-8,11,14,17-tetraoxa-28-azatetracyclo [22.3.1.027.01823]pentacosa-2,4,6,18(23),20,22,24,27,1(28)-nonaene (3d). Yield: 0.65 g (27 %), white crystals. M.p. 180-182 oC (from EtOH). R=0.48 (hexane:ethylacetate=1:1). m/z (HRMS) Calc. for C30H30NO5+: 484.2118, found 484.2100 [M+H]+. IR (KBr) v cm-1: 1610 (CN ... ), 1581, 1547, 1491 (aromatic), 1168, 1126,

max v pyridine-'5 55 v /555

1047, 1026 (COC). 'H NMR (500 MHz, CDCl3, Me4Si) 5H ppm: 3.85 (s, 3H, Me), 3.25 (s, 4H, OCH2CH2), 3.65 (m, 4H, OCH2CH2),

4.12 (m, 4H, OCH2CH2), 6.98 (d, 2HAr, J=8.0 Hz), 7.02 (d, 1HAr, J=8.5 Hz), 7.11 (m, 3HJ, 7.35 (td, 2HAr, J=8.5 Hz, 2 Hz), 7.40 (td, 2HAr, J=8.0 Hz, 1.5 Hz), 7.47 (dd, 1HAr,J=7.5 Hz, 1.5 Hz), 7.66 (dd, 2Ha, J=7.5 Hz, 1.5 Hz), 7.71 (s, 2H.„. ). 13C NMR (125 MHz,

Ar' ' 7' v ' pyridine7 v

CDCl3) 5C ppm: 14.4, 19.4, 33.7, 55.8, 101.6, 113.0, 115.9, 116.5, 119.0, 119.6, 128.0, 145.0, 146.3, 156.0.

26-(2-Thienyl)-8,11,14,17-tetraoxa-28-azatetracyclo [22.3.1.027.01823]pentacosa-2,4,6,18(23),20,22,24,27,1(28)-nonaene (3e). Yield: 0.96 g (42 %), white crystals. M.p. 147-148 oC (from EtOH). R=0.50 (hexane:ethylacetate=1:1). m/z (HRMS) Calc. for C27H26NO4S+: 460.1577, found 460.1606 [M+H]+. IR (KBr) v cm-1: 1604 (CN ... ), 839 (R-thiophen), 1548, 1493

v ' max v pyridine7' vr r 77

(aromatic), 1132, 1057 (COC). 'H NMR (500 MHz, CDCl3, Me4Si) 5H ppm: 3.22 (s, 4H, OCH2CH2), 3.63 (m, 4H, OCH2CH2), 4.12 (m, 4H, OCH2CH2), 6.99 (d, 2HAr, J=8.0 Hz), 7.11 (t, 2Ha., J=7.5 Hz), 7.14 (t, 1HAr, J=5.0 Hz), 7.36 (td, 2Ha., J=8.0 Hz, 1.5 Hz), 7.40 (d, 2HAr, J=5.5 Hz), 7.53 (d, 1HAr, J=3.5 Hz), 7.63 (dd, 2Ha., J=7.5 Hz, 1.5 Hz), 7.73 (s, 2H e). 13C NMR (125 MHz, CDCl3) 5C ppm: 14.4, 19.4, 33.7, 55py!, T01.6, 113.0, 115.9, 116.5, 1193.0, 119.6, 128.0, 145.0, 146.3, 156.0.

26-(2-Furanyl)-8,11,14,17-tetraoxa-28-azatetracyclo [22.3.1.027.01823]pentacosa-2,4,6,18(23),20,22,24,27,1(28)-nonaene (3f). Yield: 0.89 g (40 %), white crystals. M.p. 182-183 oC (from EtOH). R=0.63 (hexane:ethylacetate=1:1). m/z (HRMS) Calc. for C27H26NO5+: 444.1805, found 444.1805 [M+H]+. IR (KBr) v cm-1: 1610 (CN .„. ), 750 (b-furan), 1577, 1546, 1489, 1446

max v pyridine7' vr 7'

(aromatic), 1114, 1058 (COC). 'H NMR (500 MHz, CDCl3, Me4Si) SH ppm: 3.22 (br s, 4H, OCH2CH2), 3.63 (m, 4H, OCH2CH2), 44.11 (m, 4H, OCH2CH2), 6.53 (m, 1HJ, 6.89 (br s, 1HJ, 6.98 (d, 2HAr, J=8 Hz), 7.10 (td, 3Ha., J=7.5 Hz, 1.0 Hz), 7.35 (td, 2Ha., J=8.5 Hz, 1.5 Hz), 7.55 (br s, 1HJ, 7.61 (dd, 2Ha., J=7.5 Hz, 2.0 Hz), 7.76 (s, 2H idine). 13C NMR (125 MHz, CDCl3) i5C ppm: 69.41, 70.55, 70.88, 108iy3^",e 111.99, 114.14, 118.11, 121.70, 129.63, 130.56, 132.10, 136.55, 143.55, 152.08, 156.22, 157.05.

26-(2-Pyrrolyl)-8,11,14,17-tetraoxa-28-azatetracyclo [22.3.1.02'7.01823]pentacosa-2,4,6,18(23),20,22,24,27,1(28)-nonaene (3g). Yield: 1.06 g (48 %), white crystals. M.p. 185-186 oC (from EtOH). Rf=0.40 (hexane:ethylacetate=1:1). m/z (HRMS) Calc. for C27H27N2O4+: 443.1965, found 443.1947 [M+H]+. IR (KBr) v cm-1: 1608 (CN ... ), 747 (b-pyrrol), 1548, 1493

v ' max v pyridine7' \r rj /■>

(aromatic), 1128, 1043 (COC). 'H NMR (500 MHz, CDCl3, Me4Si) 5H ppm: 3.20 (br s, 4H, OCH2CH2), 3.62 (m, 4H, OCH2CH2), 4.10 (m, 4H, OCH2CH2), 6.33 (dt, J=6.0 Hz, 2.0 Hz), 6.73 (d,

1Ha., J=3.5 Hz), 6.94 (d, 1HAr, J=1.5 Hz), 6.98 (d, 2Ha., J=8.0 Hz), 7.11 (t, 2Ha., J=7.0 Hz), 7.34 (td, 2Ha., J=8.0 Hz, 1.5 Hz), 7.59 (s, 2H ... ), 7.63 (dd, 2H, J=7.5 Hz, 1.5Hz), 8.88 (br s, 1H, NH). 13C

pyridine7' v ' Ar' ' 7' v ' ' '

NMR (125 MHz, CDCl3) 5C ppm: 14.20, 21.05, 60.41, 60.43, 70.37, 71.05, 108.48, 110.60, 114.58, 118.40, 120.53, 121.92, 129.61, 129.98, 130.61, 132.37, 138.55, 156.20, 156.86.

X-Ray diffraction experiment

The crystal of 3a (C30H29NO5, M=483.54) is monoclinic, space group P2/c, at T=120 K: a=10.239(4) A, b=10.344(4) A, c=23.413(8) A, b=98.648(6)°, 7=2451.5(15) A3, Z=4, dcalc=1.310 g/cm3, F(000)=1024, ,«=0.089 mm-1. 21314 total reflections (5116 unique reflections, Rint=0.082) were measured on a three-circle Bruker APEX-II CCD diffractometer (l(MoKa)-radiation, graphite monochromator, j and w scan mode, 20 =54.0°) and corrected

' J ' max '

for absorption (T . =0.975; T =0.980).[15] The structure was der v min ' max '

termined by direct methods and refined by full-matrix least squares technique on F2 with anisotropic displacement parameters for non-hydrogen atoms. The hydrogen atoms were placed in calculated positions and refined within riding model with fixed isotropic displacement parameters [Uiso(H)=1.5Ueq(C) for the methyl group and 1.2Ueq(C) for the other groups]. The final divergence factors were Rj=0.116 for 3809 independent reflections with I > 2s(I) and wR2=0.242 for all independent reflections, S=1.031. All calculations were carried out using the SHELXTL program.[16]

Crystallographic data for 3a have been deposited with the Cambridge Crystallographic Data Center, CCDC 1532287. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk).

Cytotoxicity assay

Four human cancer cell lines were obtained from the American Type Culture Collection (Manassas, VA) ATCC as FL (human cervix carcinoma), RD (human rhabdomyosarcoma), Lu1 (human lung adenocarcinoma), HepG2 (human hepatocellular carcinoma). The Vero cell line was initiated from the kidney of a normal adult African green monkey. They were grown in DMEM (Dulbecco's Modified Eagle Medium) (Thermo Fisher Scientific, My) supplemented with L-glutamine, Sodium piruvat, Na, PSF (Penicillin-Streptomycin sulfate - Fungizone), NAA (Non-Essential Amino Acids), 10 % BCS (Bovine Calf Serum). All incubations were performed at 37 °C for 72 hours in a CO2 (5 %) incubator with the plates capped in the normal fashion.

The MTT is based on the protocol described by Skehan & CS (1990)[17] and Likhiwitayawuid & CS (1993).[18] This method has worldwide application and is recommended by National Cancer Institute (NCI) and College of Medicine, University of Illinois at Chicago for routine drug screening.

Results and Discussion

The starting compound (2) was prepared in a similar way using the reported method.[19] The expected dibenzo[(y-aryl)pyridino]aza-17-crown-5 ethers (3) were prepared by condensation of diketone (2) with arylaldehyde derivatives and ammonium acetate in acetic acid (Scheme 1).

The structures of compounds (3a-g) were determined by 'H NMR, 13C NMR, IR, HRMS and X-ray analyses. For example, the 'H NMR spectrum of the product (3a) showed a singlet signal at 5=3.87 ppm which is assigned to the three protons of methoxy group (-OCH3). There are three signals at 5=3.19 ppm (s, 4H), 3.17 ppm (t, 4H), 4.10 ppm (t, 4H) for twelve methylene protons of the polyether moiety -

Me

CI CI

-o o

OH

/f^

K2co3/DMF

Me Me /=■

^ //

o o

Q o" + ArCHO + NH4OAc

O O

AcOH, 3h,

e, J

-o^_o-

3 a-g

^ ^ H

a bed

Scheme 1. Synthetic pathway for the dibenzo[(y-aryl)pyridino]aza-17-crown-5 ethers.

(OCH2CH2O)-. Twelve protons of three benzene rings showed four signals at 7.64 (4H, m), 7.33 (2H, m), 7.10 (2H, q) and 6.98 (4H, m). Two ¿^-protons belonging to the pyridine subunit (H-25, H-27) gave a singlet signal at 7.72 ppm.

To further understand of the structure of these compounds and also to deeper study of the 3D structure-activity relationship, a substance (3a) was chosen as a model for acquiring 2D-spectra (HSQC and HMBC) and X-ray structure analysis, which gave valuable information to establish its structure.

HHHHHHHHHHHH

Figure 1. *H-13C HMBC connectivity of 3a.

The structure of dibenzo[(y-aryl)pyridino]aza-17-crown-5 ether (3a) was exactly confirmed by X-ray crystallography. The general shape of the molecule (3a) and the packing of its molecules in the crystal are shown in Figures 2, 3. The two intramolecular C-H—O hydrogen bonds at positions 12 and 13 explained the lowest chemical shift of protons of -(OCH2CH2O)- group in the 'H NMR

Figure 2. Molecular structure of 3a. The dashed and dotted lines indicate the intramolecular C-H—O hydrogen bonds.

spectrum.

Figure 3. Crystal packing of 3a. The dashed and dotted lines indicate the intramolecular C-H—O and intermolecular C-H-and C-H—O hydrogen bonds.

•N

The molecule of (3a) comprises a fused tetracyclic system containing the aza-17-crown-5 ether macrocycle, pyridine and two benzene rings (Figure 2). The aza-17-crown-5 ether ring adopts a bowl conformation which is stabilized by two intramolecular C-H—O hydrogen bonds (Table 1, Figure 2). The configuration of the C7-08-C9-C10-O11-C12-C13-O14-C15-C16-O17-C18 polyether chain is t-g+-g--g--g--t-g+-g--g-- (t=trans, 180°, g=gauche, ±60°). The central pyridine ring is twisted by 45.99(16), 56.32(16) and 29.06(18)° relative to the two benzene rings, fused to the aza-17-crown-5 ether moiety, and phenyl substituent, respectively. The methoxy group lies almost within the phenyl ring plane (the C33-C32-O32-35 dihedral angle is 8.9(7)°). In the crystal, the molecules of (3a) form centrosymmetrical dimers by two weak intermolecular C-H—N hydrogen bonds (Table 1). Further, the dimers are linked by weak intermolecular C-H—O hydrogen bonds into a three-dimensional framework (Table 1, Figure 3).

Table 1. Hydrogen bonds for 3a [Â and °].

D*-H-"A* d(D-H d(H--A) d(D-A) ZDHA

C9-H9a---N28a 0.99 2.59 3.491(7) 151.9

cu-Hm-on6 0.99 2.56 3.335(7) 135.1

C12-H12b-O8 0.99 2.39 3.013(6) 119.9

C13-H13b—O17 0.99 2.55 2.958(6) 104.8

C35-H35a-O11c 0.98 2.55 3.465(7) 156.1

* D - proton donor; A - proton acceptor;

Symmetry transformations used to generate equivalent atoms:

° -X, -y+1, -z;b -x,y+0.5, -z+0.5; c x+1, -y+1.5, z+0.5

Deep understanding the structure of dibenzo[(y-aryl)pyridino]aza-17-crown-5 ethers is very useful for further study of the structure-activity relationship. All factors - steric, electrostatic, the intramolecular C-H—O and intermolecular C-H—N and C-H—O hydrogen bonds influence the cytotoxicity of these compounds.

All of the synthesized compounds (3a-g) were evaluated in vitro for their biological activity against four human tumor cell lines: FL (human cervix carcinoma), RD (human rhabdomyosarcoma), Lu1 (human lung adenocarcinoma), HepG2 (human hepatocellular carcinoma). The bioactivities of synthesized compounds toward human cancer cell lines were shown in Table 2. Azacrown ethers (3b,c) showed significant activity against all four cell lines with cell survival (CS) value as 0 (%). Compound (3d) had positive results on cytotoxicity in tests against the HepG2, Lu1, RD cell lines. In addition, analogues (3f,g) have inhibited RD and FL cell lines. Based on these results, dibenzo[(y-aryl)pyridino]aza-17-crown-5 ethers (3b-d,f,g) were selected for further evaluation.

To continuously investigate the effectiveness of (3b-d,f,g) in inhibiting cancer cell lines, an inhibitory test (IC50) was conducted. Azacrown ether (3b) showed the highest activity against all of four human cell lines with an IC50 value below 3.0 ^g/ml whereas the similar synthesized compound (3c) exhibited potent cytotoxicity against those cell lines with an IC50 value in the 6.7-8.0 ^g/ml. Compound (3d) possessed cytotoxicity against HepG2, Lu1 and RD cell lines. In contrast, both compounds (3f,g) containing y-heteroaryl only exhibited cytotoxicity against RD and FL cell lines with an IC50 value in the 8.3-10.0 ^g/ml. These results were shown in Table 3.

Table 2. Cytotoxicity tests performed on compounds 3a-g in human cancer cell lines.

№ Entry Concentration (pg/ml) Cell line, cell survival (%) Conclusion

HepG2 Lu1 RD FL

DMSO - 100 100 100 100

Taxol(+) 5 1.34±0.80 3.66±0.90 0.68 ±0.30 3.87±1.10 +

1 3a 10 100 99.06±1.50 100 100 -

2 3b 10 0 0 0 0 + (04 cell lines)

3 3c 10 0 0 0 0 + (04 cell lines)

4 3d 10 20.07±0.80 38.25±0.40 39.26±0.70 64.09±0.8 + (03 cell lines)

5 3e 10 67.61±1.40 64.44±1.50 83.27±1.20 59.3±2.30 -

6 3f 10 58.45±0.80 72.89±2.80 44.83±1.10 13.46±1.60 + (RD, FL)

7 3g 10 60.85±1.40 69.47±2.60 50.09±2.80 41.71±3.10 + (RD, FL)

Table 3. Results of IC„ test.

№ Entry Cell lines IC50 (Pg/ml) Conclusion

HepG2 Lu1 RD FL

Taxol(+) 0.290 0.310 0.250 0.330 +

1 3b 2.607 2.664 2.560 1.392 + (04 cell lines)

2 3c 7.957 6.946 6.887 6.742 + (04 cell lines)

3 3d 6.586 7.904 7.528 - + (03 cell lines)

4 3f - - 8.881 8.346 + (RD, FL)

5 3g - - 10.00 9.505 + (RD, FL)

Table 4. Cytotoxicity tests performed on compounds 3b-d in Vero cell line.

Entry Entry Concentration Og/ml) Vero cell line, _ ,, wn/N Conclusion cell survival (%)

DMSO - 100

Taxol(+) 5 32.24 ±1.70

10 71.60 ±2.30

1 3b

5 86.55 ±0.70

10 65.86 ±0.80

2 3c

5 92.22 ±1.50

3 3d 10 80.92 ±1.30 -

In the continuing evaluation of potential anticancer agents, compounds (3b-d) were tested for cytotoxicity on the normal African green monkey kidney cell line (Vero cell line). The results are shown in Table 4, and these compounds are not active on the Vero cell line.

None of the new azacrown ethers (3b-d) had significant activity against the Vero cell line achieving an CS value in the 65.86 to 92.22 (%). Therefore, compounds (3b-d) could be considered as promising anticancer agents due to their low cytotoxicity on the Vero cell line and their high cytotoxic effect on the cancer cells. The results are shown in Table 4.

Thus, according to the results of the in vitro tests, compounds (3b,c) containing [y-(4-R-aryl)] have an outstanding effect in treating HepG2, Lu1, RD and FL cell lines. Compound (3d) showed high cytotoxic effect on HepG2, Lu1 and RD cell lines. At the same time, both azacrown ethers (3f,g) containing (y-heteroaryl) had weaker cytotoxicity against the RD and FL cell lines.

Conclusions

We have demonstrated good prospects for synthesis and discovery of new potential anticancer agents in the group of azacrown ethers. Seven new dibenzo[(y-aryl)pyridino] aza-17-crown-5 ethers containing 2,4,6-triarylpyridine were synthesized successfully using Hantzsch type multicom-ponent reaction. Some of the obtained compounds showed high cytotoxic activity against human tumor cells (HepG2, Lu1, RD, FL), and they were not active on the Vero cell line. These findings are interesting for further studies on active azacrown ethers (3b-d) for the proper assessment of their chemotherapeutic properties as well as for the development of promising anticancer drugs.

Acknowledgements. This research was funded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.01-2015.27 and supported by the Ministry of Education and Science of the Russian Federation (the Agreement number 02.a03.21.0008).

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Received 24.04.2017 Accepted 22.09.2017