Synthesis, Characterization and X-ray Crystal Structure of 2-Benzyl-7-butoxyl-9-isobutyl-1- methyl-β-carboline Bromide 1

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1 34 卷 7 期 结构化学 (JIEGOU HUAXUE) Vol. 34, o Chinese J. Struct. Chem Synthesis, Characterization and X-ray Crystal Structure of 2-Benzyl-7-butoxyl-9-isobutyl-1- methyl-β-carboline Bromide 1 GA Zi-Yun a CAO Ri-Hui b MA Qin a GUO Liang a2 a (Xinjiang Huashidan Pharmaceutical Research Co., Ltd., Urumqi , China) b (School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou , China) ABSTRACT 2-Benzyl-7-butoxyl-9-isobutyl-1-methyl-β-carboline bromide (H-2-65) was synthesized by the reaction of Harmine with 1-iodobutane via 9 -alkylation, demethyl and 2 -quaternarization to obtain the new compound. The results demonstrate that H-2-65 has more remarkable anticancer activities in vitro. The results of 1 H MR, 13 C MR, DEPT, gcosy, ghsqc, ghmbc, MS, single-crystal X-ray diffraction and elemental analysis showed that the title compound crystallizes in the triclinic system, space group P1 with a = 9.545(5), b = (5), c = (6) Å, α = (6), β = (6), γ = (5) o, Z = 2, V = (10) Å 3, D c = g cm -3, F(000) = 504, the final R = , wr = and S = Keywords: 2-benzyl-7-butoxyl-9-isobutyl-1-methyl-β-carboline bromide, synthesis, crystal structure; DOI: /j.cnki ITRODUCTIO Peganum harmala L., distributed in Uyghur nationality in Xinjiang, China, has been regarded as a traditional herb for medicinal or psychoactive therapy in water shortage deserts and grasslands for hundreds of years [1]. Moreover, it has been reported to possess a wide spectrum of pharmacological actions in different kinds of applications, including antibacterial, antifungal, antitumor treatments and effectiveness in the treatment of dermatosis [2-4]. Harmine (Fig. 1) was originally isolated from P. harmala, and subsequent investigation confirmed that it was the most important active ingredients [5, 6]. H 3 CO H A B Br - 27 O + 26 (2) CH 5 (1) Fig. 1. Structure of Harmine (A) and the title compound (B) Previous investigations [7-14] were focused on the neuropharmacological effects of harmine on the Received 4 January 2015; accepted 21 May 2015 (CCDC ) 1 Supported by the ational Key Technology Research and Development Program of the Ministry of Science and Technology of China (o. 2012BAI30B00) 2 Corresponding author. Guo Liang, born in 1980, M.S., majoring in medicinal chemistry. guoliang_xj@163.com

2 GA Z. Y. et al.: Synthesis, Characterization and X-ray Crystal 1036 Structure of 2-Benzyl-7-butoxyl-9-isobutyl-1-methyl-β-carboline Bromide o. 7 central nervous system (CS). Structure-activity relationship analysis demonstrated that the methoxy group at position-7 of harmine might play a very crucial role in determining their remarkable neurotoxic effects; 9 -alkylated harmine derivatives exhibited strong cytotoxic effects; 2 -alkylated harmine derivatives displayed specific cytotoxic activities. Herein, we report the synthesis and single-crystal structure of 2-benzyl-7-butoxyl-9- isobutyl-1-methyl-β-carboline bromide (Fig. 1). 2 EXPERIMETAL 2. 1 Materials and characterization Melting points were determined in capillary tubes on an electrothermal WRS-3 apparatus without correction. 1 H MR and 13 C MR spectra were recorded on a Varian IOVA 400 spectrometer. Elemental analyses (C, H and ) were carried out on an Elementar Vario EL III Elemental Analyzer. ESI-MS spectra were obtained from Micromass ZQ4000 spectrometer. Crystal structure was determined on a Bruker SMART CCD. All reagents purchased from commercial suppliers were dried and purified when necessary Synthesis of the target compound As shown in Scheme 1, a mixture of harmine (4.24 g, 20 mmol) and anhydrous DMF (80 ml) was stirred at room temperature, and then 95% ah (0.75 g, 30 mmol) and isobutyl bromide (6.4 ml, 50 mmol) were added. The mixture was continued to stir at room temperature. After completion of the reaction, the solution was poured into H 2 O (200 ml), and extracted with ethyl acetate. After filtration and evaporation, the resulting product was crystallized from ethyl ether. Compound 2 (m. p ~113.5 ) was obtained as white solid. Then acetic acid (100 ml) and 40% hydrobromic acid (50 ml) were added, and the mixture was refluxed for 8~12 h to obtain compound 3. Compound 4 was afforded as the method of 2. At last, the mixture of compound 4 (2 mmol) and benzyl bromide (5~10 mmol) in ethyl acetate (50 ml) was refluxed for 5 h. After completion of the reaction, the solution was cooled and filtered to afford yellow solid and recrystallized from ethanol to give the pure solid compound 5: Yellow crystals, yield: 89%, m. p.: 245.3~ The structure was characterized by MR (Figs. 2 ~ 4), ESI-MS and elemental analysis. Anal. Calcd. (%) for C 27 H 33 Br 2 O: C, 67.35; H, 6.91;, Found (%): C, 67.24; H, 6.96;, H MR (DMSO-d 6, 400 MHz) δ: 8.87 (1H, d, J = 6.8 Hz, H-14), 8.68 (1H, d, J = 6.4 Hz, H-15), 8.40 (1H, d, J = 8.8 Hz, H-9), 7.48 (1H, d, J = 2.0 Hz, H-6), 7.36~7.45 (2H, m, H-24, H-26), 7.19~7.21 (2H, m, H-23, H-27), 7.10 (1H, dd, J = 8.8, 2.0 Hz, H-10), 6.07 (2H, s, H-21), 4.55 (2H, d, J = 7.2 Hz, H-17), 4.20 (2H, t, J = 6.4 Hz, H-4), 3.06 (3H, s, H-16), 2.04~2.07 (1H, m, H-18), 1.76~1.83(2H, m, H-3), 1.48~1.54(2H, m, H-2), 0.96 (3H, t, J = 7.2 Hz, H-1), 0.83 (6H, d, J = 6.8 Hz, H-19, H-20). 13 C MR (DMSO-d 6, 100 MHz) δ: (C-5), (C-7), (C-13), (C-14), (C-22), (C-12), (C-11), (C-24, C-26), (C-25), (C-23, C-27), (C-9), (C-15), (C-10), (C-8), 94.9 (C-6), 68.1 (C-4), 59.6 (C-21), 51.2 (C-17), 30.5 (C-3), 30.3 (C-18), 19.3 (C-19, C-20), 18.6 (C-2), 16.1 (C-16), 13.6 (C-1). ESI-MS m/e 401 [M-Br] Single-crystal X-ray structure determination A single crystal of compound 5 suitable for X-ray diffraction study was obtained from the mix solution of ethanol/acetone (V:V = 2:1) by slow evaporation at room temperature. A crystal with dimensions of 0.30mm 0.25mm 0.20mm was used. The crystal is of triclinic system, M r = X-ray diffraction intensity data were collected with a graphite-monochromatic MoKα (λ = Å) radiation at 298(2) K. A total of 7587 reflections with 5473 independent ones (R int = ) were collected in the range of 2.28 θ o by using an ω-2θ scan mode, in which 4304 were observed (I > 2σ(I)) in the succeeding refinements with 12 h 12, 14 k 15 and 15 l 12. The structure

3 2015 Vol. 34 结构化学 (JIEGOU HUAXUE)Chinese J. Struct. Chem was solved by direct methods and refined by using difference Fourier techniques with SHELXS-97 [15] and refinements on F 2 were performed with SHELXL-97 program by full-matrix least-squares techniques with anisotropic thermal parameters for the non-hydrogen atoms. The positions of hydrogen atoms were located by the geometric calculation method. The final R = and wr = (w = 1/[σ 2 (F 2 o ) + (0.0828P) P], where P = (F o + 2F 2 c )/3). S = 1.044, (Δρ) min = and (Δρ) max = e Å -3. H 3 CO H ( ) 2 CHCH 2 I DMF/aH H 3 CO HBr/HAc HO C 4 H 9 I DMF/aH O CH 2 Br ethyl acetate O + Br - CH 2 4 Scheme 1. Synthetic route of the target compound 5 5 Fig. 2. A section of the gradient correlated ( 1 H- 1 H COSY) spectrum of the title compound Fig. 3. A section of heteronuclear single-quantum coherence (HSQC) spectrum of the title compound

4 GA Z. Y. et al.: Synthesis, Characterization and X-ray Crystal 1038 Structure of 2-Benzyl-7-butoxyl-9-isobutyl-1-methyl-β-carboline Bromide o. 7 Fig. 4. A section of heteronuclear multiple-bond coherence (HMBC) spectrum of the title compound 3 RESULTS AD DISCUSSIO The MR and X-ray diffraction data for the product are in good agreement with the structure of the title compound. The selected bond lengths, bond angles and torsion angles are listed in Tables 1 and 2, respectively. The molecular structure of compound 5 with atomic numbering scheme is shown in Figs. 5 and 6. Table 1. Selected Bond Lengths (Å) and Bond Angles ( ) Bond Dist. Bond Dist. Bond Dist. C(1) C(2) 1.413(8) C(7) (1) 1.388(3) C(13) (2) 1.368(3) C(3) C(4) 1.503(6) C(7) C(8) 1.406(3) C(14) (2) 1.370(4) C(4) O(1) 1.454(4) C(9) C(10) 1.368(4) C(17) (1) 1.467(3) C(5) C(6) 1.384(4) C(11) C(15) 1.396(4) C(18) C(19) 1.499(5) C(5) C(10) 1.411(4) C(12) (1) 1.392(3) C(21) (2) 1.486(4) Angle ( ) Angle ( ) Angle ( ) C(7) (1) C(12) 107.7(2) C(6) C(7) C(8) 122.2(2) (2) C(13) C(16) 118.3(2) C(7) (1) C(17) 123.3(2) C(9) C(10) C(5) 121.2(2) C(15) C(14) (2) 121.4(2) O(1) C(5) C(6) 124.1(3) C(12) (1) C(17) 128.9(2) (1) C(17) C(18) 114.0(2) C(6) C(5) C(10) 122.2(3) (1) C(12) C(13) 131.1(2) C(19) C(18) C(20) 112.3(4) (1) C(7) C(6) 128.0(2) C(14) (2) C(21) 115.6(2) (2) C(21) C(22) 112.6(2) Table 2. Selected Torsion Angles ( ) Angle ( ) Angle ( ) C(10) C(5) O(1) C(4) 179.3(2) (1) C(12) C(13) (2) 178.9(2) O(1) C(5) C(6) C(7) 179.8(2) C(15) C(11) C(12) C(13) 2.0(3) C(10) C(5) C(6) C(7) 0.1(4) (1) C(12) C(13) C(16) 0.2(4) C(5) C(6) C(7) (1) 178.9(2) (2) C(14) C(15) C(11) 1.0(4) C(5) C(6) C(7) C(8) 1.6(4) (1) C(17) C(18) C(19) 62.9(4) C(7) C(8) C(9) C(10) 0.6(4) (1) C(17) C(18) C(20) 171.9(3) C(9) C(8) C(11) C(15) 3.1(5) C(24) C(25) C(26) C(27) 0.6(9)

5 2015 Vol. 34 结构化学 (JIEGOU HUAXUE)Chinese J. Struct. Chem Fig. 5. Crystal structure of the title compound Fig. 6. Packing diagram of the title compound The compound 5 crystallizes in the triclinic space group P1. In this molecule, there are two crystallographically independent but conformationally almost identical molecules in the asymmetric unit. Moreover, in each molecule, the β-carboline moiety appears to be fully planar, but forms a dihedral angle of 76.0 with the benzyl phenyl ring. Consequently, the whole compound is not a planar molecule. According to Fig. 5 and Table 1, the bond angles of C(6) C(5) C(10), C(15) C(11) C(12) and (2) C(13) C(16) are close to the ideal 120. In the crystal structure, the sum of C(7) (1) C(12), C(7) (1) C(17) and C(12) (1) C(17) is 359.9, which indicates sp 2 hybridization state of the (1) atom. The C(7) (1), C(12) (1), C(13) (2) and C(14) (2) bond lengths are 1.388(3), 1.392(3), 1.368(3) and 1.370(4) Å, respectively, which is obviously shorter than the typical C bond (1.470 Å) [16], but close to the C= double bond (1.38 Å) [17] due to the conjugative effect, which suggests that π electrons are broadly distributed in the β-carboline ring. The distance between the bromide anion and the β-carboline ring centroid is Å, and the sum of van der Waals radii of bromine and carbon is 3.55 Å, indicating the existence of π bromide anion interactions. Continuously sandwiched structures are formed owing to these interactions between β-carboline rings and bromide anion (Fig. 6). These interactions contribute to the stability of the structure. The sum of these interactions results in the formation of a three-dimensional framework. The introduction of substituents onto β-carboline ring is considered to change the crystal structure

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