CHEN Xiu-Wen JIA Guo-Kai WANG Zong-Cheng

?

Synthesis, Crystal Structure and Antitumor Activities of (14S)-2,14-diphenyl-6,6a,11,12-tetrahydro-5H,10H,14H-[1,8]naphthyridino[1,2-c]pyrido[3,2,1-ij] quinazoline-3-carbonitrile①

CHEN Xiu-Wen JIA Guo-Kai WANG Zong-Cheng②

a(425199)b(425199)

naphthyridine, tetrahydroquinazolines, synthesis, crystal structure, antitumor activity;

1 INTRODUCTION

1,2,3,4-Tetrahydro-1,8-naphthyridine moieties (THNs) are present in numerous molecules with important biological activities, as represented by a potent antagonist of thev3receptor (structure-A)[1-3],cholesterol ester transfer protein inhibitor (structure-B)[4], antioxidants in lipid membranes and low-density lipoproteins (structure-C)[5], and antibac- terial agents (structure-D)[6, 7].Moreover, THNs serve as interesting building blocks that have been extensively applied for various synthetic purposes[8].Additionally,tetrahydroquinazolines skeleton cons- titutes the core structure of numerous products exhibiting interesting bioactivities including DNA- intercalation[9]and inhibition of butyrylcholine- sterase[10].However, the synthesis of tetrahydroquina- zolines derivatives is rare.Hence, the development of efficient and accurate reliabile methods to synthesize tetrahydroquinazolines has been of great interest and the subject of several recent reviews.In order to studythe synthesis and activities of tetrahydroquina- zolines derivatives, the title compound (14S)-2,14-diphenyl-6,6a,11,12-tetrahydro-5H,10H,14H-[1,8]naphthyridino[1,2-c]pyrido[3,2,1-ij]quinazoline-3-carbonitrile was prepared from low-cost 2-amino- nicotinaldehyde, and further characterized by1H-NMR and ESI spectrum.And its crystal structure was also determined by single-crystal X-ray diffrac- tion.

2 EXPERIMENTAL

2.1 Synthesis of the title compound

All analytical grade chemicals and solvents were purchased commercially and used without further purification.

The1H-NMR spectrum of the title compound was tested on a Mercury Plus-500 spectrometer by using TMS as the internal standard and CDCl3as the solvent.Mass spectra were recorded on a thermo Finnigan LCQ Advantage LC/Mass detector instrument.

The synthetic route of the title compound 6 was outlined in Scheme 1.

Scheme 1. Procedure for the preparation of compound 6

The title compound 6 was prepared as follows:

The preparation of 2-phenyl-1,8-naphthyridine-3- carbonitrile 3 was similar to the literature proce- dures[11].2-Aminonicotinaldehyde 1 (5 mmol), 3- oxo-3-phenylpropanenitrile 2 (5 mmol),-BuOK (20 mol %), and ethanol (10 mL) were introduced in a flask (50 mL).Then, it was stirred at 50oC under atmosphere for 2 h.After cooling down to room temperature, the reaction mixture was concentrated by removing the solvent under vacuum, and the residue was purified by column chromatography and eluted with petroleum ether/ethyl acetate (4:1, v/v) to give a yellow solid 3 with the yield of 82%.1H NMR (400 MHz, CDCl3):9.27 (s, 1H), 8.75 (s, 1H), 8.30 (d,= 7.9 Hz, 1H), 8.13 (s, 2H), 7.68～7.50 (m, 4H).13C NMR (101 MHz, CDCl3):161.27, 156.98, 155.94, 145.63, 137.03, 136.84, 130.75, 129.51, 128.68, 123.47, 119.96, 117.33, 106.70.MS (EI, m/z): 231.1 [M]+.

Procedure for the synthesis of 5: Under N2atmosphere, tetrahydroquinoline 4 (0.3 mmol), 2-phenyl-1,8-naphthyridine-3-carbonitrile 3 (0.2 mmol), [Cp*IrCl2]2(1 mol %), and-amyl alcohol (1.0 mL) were introduced into a Schlenk tube (25 mL) successively.Then, the Schlenk tube was closed and the resulting mixture was stirred at 130 °C for 18 h.After cooling down to room temperature, the reaction mixture was concentrated by removing the solvent under vacuum, and the residue was purified by preparative TLC on silica, eluting with petroleum ether (60～90 °C): ethyl acetate (5:1) to give 5.Yellow solid (52.7 mg, 0.144 mmol, 72% yield), m.p: 189～191 °C.1H NMR (400 MHz, CDCl3):7.86～7.80 (m, 2H), 7.49～7.43 (m, 4H), 6.94 (dd,= 11.3, 7.6 Hz, 2H), 6.60 (t,= 7.5 Hz, 1H), 5.85 (s, 1H), 4.61～4.47 (m, 1H), 3.38～3.27 (m, 2H), 2.85～2.71 (m, 4H), 2.20～2.03 (m, 2H), 1.93～1.85 (m, 2H).13C NMR (101 MHz, CDCl3):159.65, 157.72, 141.51, 139.85, 137.93, 129.53, 129.18, 128.67, 128.43, 124.62, 122.25, 119.85, 116.56, 114.71, 94.25, 51.86, 42.16, 27.64, 24.90, 24.47, 21.76.IR (KBr): 3407, 3057, 2940, 2844, 2211, 1602, 1507, 1435, 1279, 1188, 1123, 918 cm-1.HRMS (ESI): calcd.for C24H23N4[M+H]+: 367.1917; found: 367.1922.

Procedure for the synthesis of 6: Compounds 5 was treated with benzaldehyde in acetic acid at 70oC for 5 h, which underwent effective intermolecular condensation to afford the cyclization products 6.Brownish solid (32.7 mg, 0.072 mmol, 72% yield); m.p: 101～103 °C;1H NMR (400 MHz, CDCl3):7.98 (d,= 6.8 Hz, 2H), 7.57～7.47 (m, 4H), 7.45 (s, 1H), 7.37 (d,= 6.8 Hz, 2H), 7.35～7.27 (m, 3H), 6.94 (d,= 7.3 Hz, 1H), 6.89 (d,= 7.6 Hz, 1H), 6.61 (t,= 7.5 Hz, 1H), 4.54 (t,= 5.0 Hz, 1H), 3.51～3.35 (m, 2H), 2.93～2.72 (m, 4H), 2.35～2.22 (m, 2H), 2.13～1.96 (m, 2H).13C NMR (101 MHz, CDCl3):158.67, 155.60, 140.39, 140.21, 139.90, 138.24, 129.55, 128.73, 128.70, 128.42, 128.08, 127.91, 126.99, 122.27, 121.55, 120.76, 119.74, 116.62, 115.86, 94.84, 69.05, 50.03, 48.34, 27.69, 24.70, 23.92, 21.55.IR (KBr): 3059, 2924, 2336, 2213, 1598, 1493, 1314, 1270, 1016, 699 cm-1.HRMS (ESI): Calcd.for C31H27N4[M+H]+: 455.2230; found: 455.2233.

2.2 Crystal data and structure determination

The crystals of the title compound suitable for X-ray structure determination were obtained by slowly evaporating an ethanol solution for about a week at room temperature.A yellow single crystal of the title compound 6 with dimensions of 0.21mm × 0.2mm × 0.19mm was put on a Bruker P4 diffrac- tometer equipped with a graphite-monochromatized Moradiation (= 0.71073 ?).Intensity data were collected at 296(2) K by using anscan mode in the range of1.417≤≤25.208o with the following index ranges: –10≤≤10, –10≤≤14 and –17≤≤17.A total of 9249 reflections were collected and 5041 were independent (int= 0.0261), of which 5041 were observed (> 2()).The structure was refined on2by full-matrix least-squares procedure with SHELXL-97[12]package.All non-hydrogen atoms were refined with anisotropic thermal parameters.The hydrogen atoms were located from difference Fourier map, added theoretically, and then refined isotropically with riding model position parameters.The final cycle of refinement gave= 0.0484 and= 0.1388 (= 1/[2(F2) + (0.0708)2], where= (F2+ 2F2)/3) with 316 parameters.= 0.966, (Δ)max= 0.186, (Δ)min= –0.229 e/?3and (Δ/)max= 0.001.

2.3 Antitumor activity evaluation

Two samples, 5-fluorouracil and docetaxol, were dissolved in DMSO to prepare the DMSO solution, respectively.These solutions were subjected to MTT assay.5-Fluorouracil and docetaxol were used as positive control and DMSO as the blank control.The assay was run in triplicate on human cancer K562, HL-60, HeLa and BGC-823 cell lines by the method that we have previously reported[13].

3 RESULTS AND DISCUSSION

The structure of the title compound 6 wastestified by1H-NMR,13C NMR, IR,HRMS (ESI) and single-crystal X-ray analysis.The molecular struc- ture of the title compound 6 is shown in Fig.1 and the selected bond lengths and bond angles are listed in Table 1.

Fig.1. Molecular structure of the title compound 6

Table 1. Selected Bond Lengths (?) and Bond Angles (°) for the Title Compound 6

The title molecule consists of seven six-membered rings (rings a, b, c, d, e, f and g).The first benzene ring (ring a) consisting of the C(1), C(2), C(3), C(4), C(5) and C(6) atoms, the second benzene ring (ring c), composed of the C(11), C(12), C(13), C(14), C(15) and C(16) atoms, the third benzene ring (ring g), built by the C(25), C(26), C(27), C(28), C(29) and C(30) atoms, and the pyridine ring (ring f) made up of the C(20), C(21), C(22), C(24), N(3) and C(31) atoms, are coplanar.The dihedral angles between the three benzene rings are 82.66° (ring a and c), 86.34° (ring a and g) and 59.47° (ring c and g), respectively, and those between the pyridine ring and three benzene rings are 83.37° (ring a and f), 25.80° (ring c and f) and 33.67° (ring g and f), respectively.Three noncoplanar rings (ring b, d and e) display half-chair conformation[14].As shown in Table 1, for the title compound 6, the bond lengths of N(1)–C(16) (1.394(2) ?) and N(2)–C(31) (1.366(2) ?) are shorter than the typical C–N (1.47 ?) and longer than the typical C=N (1.35 ?), which confirm these bonds have some characters of a double or conjugated bond[15].The bond length of N(4)–C(23) is 1.144(3) ?, which confirms it is the typical C≡N (1.15 ?).The bond angles of four coplanar rings are close to 120o, but many bond angles in the other rings are 110o.

Theantitumor activities of the title com- pound were evaluated against human cancers K562, HL-60, HeLa and BGC-823 cell lines by the MTT assay.As described in Table 2, it displays different inhibition activities against human cancer K562, HL-60, HeLa and BGC-823.The title compound 6 has a better antitumor activity against K562 than against HeLa.Although it is weaker than 5-fluo- rouracil and Docetaxol in 100 μg·mL-1, the title compound 6 has a better antitumor activity than compound 3.So, the target derivative is expected to be developed as a novel antitumor agent though further structural optimization.

Table 2. Antitumor Activities of Compounds 6 against Human Cancer K562, HL-60, HeLa and BGC-823 Cell Lines

(1) Hutchinson, J.H.; Halczenko, W.; Brashear, K.M.; Breslin, M.J.; Coleman, P.J.; Duong, L.T.; Fernandez-Metzler, C.; Gentile, M.A.; Fisher, J.E.; Hartman, G.D.; Huff, J.R.; Kimmel, D.B.; Leu, C.T.; Meissner, R.S.; Merkle, K.; Nagy, R.; Pennypacker, B.; Perkins, J.J.; Prueksaritanont, T.; Rodan, G.A.; Varga, S.L.; Wesolowski, G.A.; Zartman, A.E.; Rodan, S.B.; Duggan, M.E.Nonpeptide alphavbeta3 antagonists.8.In vitro and in vivo evaluation of a potent alphavbeta3 antagonist for the prevention and treatment of osteoporosis.2003, 46, 4790–4798.

(2) Hartner, F.W.; Hsiao, Y.; Eng, K.K.; Rivera, N.R.; Palucki, M.; Tan, L.; Yasuda, N.; Hughes, D.L.; Weissman, S.; Zewge, D.; King, T.; Tschaen, D.; Volante, R.P.Methods for the synthesis of 5,6,7,8-tetrahydro-1,8-naphthyridine fragments forV3integrin antagonists.2004, 69, 8723–8730.

(3) Breslin, M.J.; Duggan, M.E.; Halczenko, W.; Hartman, G.D.; Duong, L.T.; Fernandez-Metzler, C.; Gentile, M.A.; Kimmel, D.B.; Leu, C.T.; Merkle, K.; Prueksaritanont, T.; Rodan, G.A.; Rodan, S.B.; Hutchinson, J.H.Nonpeptidev3antagonists.Part 10: In vitro and in vivo evaluation of a potent 7-methyl substituted tetrahydro-[1,8]naphthyridine derivative.2004, 14, 4515–4518.

(4) Fernandez, M.C.; Escribano, A.; Mateo, A.I.; Parthasarathy, S.; Martin de la Nava, E.M.; Wang, X.; Cockerham, S.L.; Beyer, T.P.; Schmidt, R.J.; Cao, G.; Zhang, Y.; Jones, T.M.; Borel, A.; Sweetana, S.A.; Cannady, E.A.; Stephenson, G.; Frank, S.; Mantlo, N.B.Design, synthesis and structure-activity-relationship of 1,5-tetrahydronaphthyridines as CETP inhibitors.2012, 22, 3056–3062.

(5) Nam, T.G.; Rector, C.L.; Kim, H.Y.; Sonnen, A.F.P.; Meyer, R.; Nau, W.M.; Atkinson, J.; Rintoul, J.; Pratt, D.A.; Porter, N.A.Tetrahydro-1,8-naphthyridinol analogues of-tocopherol as antioxidants in lipid membranes and low-density lipoproteins.2007, 129, 10211–10219.

(6) Seefeld, M.A.; Miller, W.H.; Newlander, K.A.; Burgess, W.J.; DeWolf, W.E.; Elkins, P.A.; Head, M.S.; Jakas, D.R.; Janson, C.A.; Keller,P.M.;Manley, P.J.; Moore, T.D.; Payne, D.J.; Pearson, S.; Polizzi, B.J.; Qiu, X.; Rittenhouse, S.F.; Uzinskas, I.N.; Wallis, N.G.; Huffman, W.F.Indole naphthyridinones as inhibitors of bacterial Enoyl-ACP reductases FabI and FabK.2003, 46, 1627–1635.

(7) Olepu, S.; Suryadevara, P.K.; Rivas, K.; Yokoyama, K.; Verlinde, C.L.; Chakrabarti, D.; Voorhis, W.C.V.; Gelb, M.H. 2-Oxo-tetrahydro-1,8-naphthyridines as selective inhibitors of malarial protein farnesyltransferase and as anti-malarials.2008, 18, 494–497.

(8) Briones, J.F.; Basarab, G.S.Expedient synthesis of tetrahydroquinoline-3-spirohydantoin derivativesthe Lewis acid-catalyzed-amino effect reaction.2016, 52, 8541–8544.

(9) Malancona, S.; Donghi, M.; Ferrara, M.; Martin Hernando, J.I.; Pompei, M.; Pesci, S.; Ontoria, J.M.; Koch, U.; Rowley, M.; Summa, V.Allosteric inhibitors of hepatitis C virus NS5B polymerase thumb domain site II: Structure-based design and synthesis of new templates.2010, 18, 2836–2848.

(10) Sawatzky, E.; Wehle, S.; Kling, B.; Wendrich, J.; Bringmann, G.; Sotriffer, C.A.; Heilmann, J.; Decker, M.Discovery of highly selective and nanomolar carbamate-based butyrylcholinesterase inhibitors by rational investigation into their inhibition mode.2016, 59, 2067–2082.

(11) Moya, S.A.; Gajardo, J.; Araya, J.C.; Cornejo, J.J.; Guerchais, V.; Bozec, H.L.; Carles Bayón, J.; Pardey , A.J.; Aguirre, P.Y.Synthesis and characterization of new complexes of the type [Ru(CO)2Cl2(2-phenyl-1,8-naphthyridine-kN)(2-phenyl-1,8-naphthyridine-Kn)].Preliminary applications in homogeneous catalysis.2008, 22, 471–478.

(12) Sheldrick, G.M.A short history of SHELX..2008, A64, 112–122.

(13) Chen, X.W.; Li, C.W.; Cui, C.B.; Hua, W.; Zhu, T.J.; Gu, Q.Q.Nine new and five known polyketides derived from a deep sea-sourcedsp.16-02-1.2014, 12, 3116–3137.

(14) Chen, C.Y.; He, Q.T.; Sun, D.D.; Hu, J.S.Crystal structure and antiproliferative activity of ethyl 3,9-dihydroxy-9-methyl-7-phenyl-7,8,10- trihydro-6Hdibenzo [b,d]pyran-6-one-8-carboxylate.2016, 35, 199–204.

(15) Xu, Z.Y.; Zhong, Y.; Liu, Y.L.; Xu, Y.; Li, P.; Wu, B.Synthesis, crystal structure and neuroprotective activity of (E)-1-(4-(4-chlorobenzyl) piperazin-1-yl)- 3-(benzo[d][1,3]dioxol-5-yl)prop-2-en-1-one.2016, 35, 1348–1354.

24 January 2018;

11 April 2018 (CCDC 1831611)

①This work was supported by the Natural Science Foundation of Hunan Province (No.2018JJ3196), the opening project of key laboratory of comprehensive utilization of advantage plants resources in Hunan south, Hunan university of science and engineering (No.XNZW17C04, XNZW17C05), and aid program for science and technology innovative research team in higher educational institutions of Hunan province (No.2012-318)

Wang Zong-Cheng.E-mail: wangzongche@163.com

10.14102/j.cnki.0254-5861.2011-1958