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Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives
Chinese Chemical Letters 18 (2007) 1179–1181 www.elsevier.com/locate/cclet
Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives Sheng Biao Wan a, Zhe Lin Liu a, Di Chen b, Qing Ping Dou b, Tao Jiang a,* a
Key Laboratory of Marine Drug, Ministry of Education, Medical College, Ocean University of China, Qingdao 266003, China b The Prevention Program, Barbara Ann Karmanos Cancer Institute, and Department of Pathology, School of Medicine, Wayne State University, Detroit, MI, USA Received 25 April 2007
Abstract 11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid was obtained specifically by polyphosphorous acid catalyzed cyclization with optimal reaction conditions. Biological assays showed that it potentially inhibits the proteasomal chymotrypsin-like activity in vitro and suppresses breast cancer cell growth. # 2007 Tao Jiang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Cryptolepine; Trioligomer; Synthesis; Proteasome
Cryptolepine is an indoloquinoline alkaloid isolated from the west African climbing shrub Cryptolepis sanguinolenta [1]. It has been shown to have anti-tumor [2], anti-bacterial [3], anti-thrombotic [4], and anti-malarial [5] activities. In order to improve its bioavailability and find more potential anti-tumor compounds, several synthetic methods were developed to construct the indolequinoline scandold [6]. A facile strategy is polyphosphorous catalyzed cyclization. Modifications of cryptolepine at D ring with methyl or halo substitutes were performed with this synthetic tactic. However, there are no more study of cryptolepine analogs with electron withdrawing group at D ring. In this paper we report the successful synthesis of a cryptolepine analog with a carboxyl group at D ring (compound 1). Its inhibition of breast cancer cell growth and inhibition of a related molecular target proteasome were also tested. The synthetic route is shown in Scheme 1. Acylation of 2-aminobenzoic acid 3 by chloroacetyl chloride gave intermediate 4 with 90% yield. In literature, compound 4 usually condensed well with aniline which has methyl or halo substitutes in benzene. however, when condensed with 4-aminobenzoic acid which has a strong electron withdrawing group, the conversion was too low to obtain the desired compound 5 in benzene or even in DMF. Alternatively compound 4 reacted with 4-aminobenzoic acid in Na2CO3 aq. at 100 8C to afford the corresponding compound 5 with 78.9% yield. We have tried the cyclization of 5 in polyphosphoric acid (PPA) at 100–130 8C. Little conversion of intermediate 5 was observed from TLC at 100–110 8C. Compound 1 with 45% of yield was obtained at 110–120 8C because of the incompletely conversion, and an 18 member ring trioligomer 2 was dramatically isolated with 6% yield
* Corresponding author. E-mail address: [email protected] (T. Jiang). 1001-8417/$ – see front matter # 2007 Tao Jiang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2007.08.014
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Scheme 1. Synthetic route of compound 1. (a) Chloroacetyl chloride, DMF/dioxane, ice bath, 4 h, 90%; (b) Na2CO3, H2O, 90 8C, 3 h, 78.9%; (c) PPA, 110–120 8C, 1 h, 1 (45%), 2 (6%); (d) PPA, 130 8C, 2 h, 1 (67%).
from the crude products. The trioligomer 2 was purified by Chromatograph with Sephadex G-10, for it is more soluble in water than compound 1. The optimal condition is that the cyclization worked in PPA at 130 8C for 2 h to afford 67% of desired compounds 1, and no trioligomer 2 was isolated. The target molecular 1 and byproduct trioligomer 2 were determined by HRMS and NMR [12]. HRMS of compound 2 showed that it is a trioligomer of the condensation of intermediate 5, and 1H NMR disclosed that it is a symmetric 18 member macro ring, for the chemical shifts of D ring protons changed much more than that of A ring protons. The ubiquitin/proteasome pathway has been considered as an important target for anticancer drug development. The proteasome inhibitor Bortezomib (Velcade, PS-341) has been used in clinical trials and its anti-tumor activity has been reported in a variety of tumor models [7–9]. To examine whether compound 1 is capable of inhibiting the proteasome activity, we incubated compound 1 at various concentrations with extracted proteins from human breast cancer MDA-MB-231 cells containing 26S proteasome and a fluorogenic peptide substrate for 2 h at 37 8C. After incubation, the fluorescent production of hydrolyzed AMC groups was measured. The results showed that the proteasomal chymotrypsin-like activity was inhibited by 25.7, 47.3 and 63.2%, respectively, when compound 1 was used at 1, 10 and 50 mmol/L. It has been shown that inhibition of the proteasomal chymotrypsin-like activity is associated with induction of tumor cell growth arrest and/or apoptosis [10,11]. To determine whether proteasome inhibition by compound 1 causes suppression of cell proliferation, human breast cancer MDA-MB-231 cells were treated with indicated concentrations of compound 1 or equal volume of the vehicle DMSO for 24 h, followed by MTT assy. We found that compound 1 inhibited proliferation of MDA-MB-231 cells in a dose-dependent manner: by 21.0, 31.0 and 47.2%, respectively, when used at 1, 10 and 50 mmol/L. Acknowledgment This work was supported by National Basic Research Program of China (973 Program) (No. 2003CB71640). References [1] [2] [3] [4] [5] [6] [7] [8]
D.E. Bierer, S.R. King, et al. J. Med. Chem. 41 (1998) 894. K. Bonjean, L. Angenot, et al. Biochemistry 37 (1998) 5136. A. Paulo, M. Pimentel, S. Viegas, et al. J. Ethnopharmacol. 44 (1994) 73. A.O. Oyekan, S.Y. Ablordeppey, et al. Gen. Pharmacol. 24 (1993) 461. K. Cimanga, et al. J. Nat. Prod. 60 (1997) 688. J. Luo, D.M. Fort, G.M. Reaven, et al. Diabetic Med. 15 (1998) 367. Q.P. Dou, R.H. Goldfarb, IDrugs 5 (2002) 828. C.N. Papandreou, C.J. Logothetis, Cancer Res. 64 (2004) 5036.
S.B. Wan et al. / Chinese Chemical Letters 18 (2007) 1179–1181 [9] [10] [11] [12]
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R.C. Kane, A.T. Farrell, R. Sridhara, R. Pazdur, Clin. Cancer Res. 12 (2006) 2955. B. An, R.H. Goldfarb, R. Siman, Q.P. Dou, Cell Death Differ. 5 (1998) 1062. U.G. Lopes, P. Erhardt, R. Yao, J. Biol. Chem. 272 (1997) 12893. Melt point and spectral data of 11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid 1: m.p. > 300 8C; 1H NMR (DMSO-d6, 600 MHz) d 12.72 (bs, 1 H), 12.64 (s, 1 H), 12.13 (s, 1 H), 8.98 (s, 1 H), 8.35 (d, J = 8.0 Hz, 1 H), 8.04 (d, J = 8.8 Hz, 1 H), 7.74 (m, 2 H), 7.55 (d, J = 14.4 Hz, 1 H), 7.32 (m, 1 H); 13C NMR (DMSO-d6, 600 MHz) d 168.0, 167.7, 140.8, 139.3, 131.3, 129.9, 128.4, 125.4, 124.3, 123.9, 123.2, 121.6, 121.3, 118.1, 115.9, 114.9, 112.6; HRMS (ESI) calcd for C16H11N2O3 [M+H] 279.0769, found 279.0734. 2,8,14-triazatetracyclo[142,24,7,210, 3]tetracosa-4,6,10,12,18,19,21,23-nonaene-3,9,15-trione-2, 8,14-tri(2-acetyl-aminobenzoic acid) 2-[2-[4-carboxyl -(phenylamino)acetyl]amino]benzoic acid 2: m.p. 232–234 8C; 1H NMR (DMSO-d6, 600 MHz) d 12.03 (s, 3 H), 8.59 (d, J = 8.0 Hz, 3 H), 8.03 (dd, J = 8.0, 1.4 Hz, 3 H), 7.59 (t, J = 8.5 Hz, 3 H), 7.30(d, J = 8.5 Hz, 6 H), 7.24 (d, J = 8.5 Hz, 6 H), 7.17 (t, J = 8.0 Hz, 3 H), 4.56 (s, 6 H); 13C NMR (DMSO-d6, 600 MHz) d 170.8, 170.0, 166.9, 143.3, 140.5, 135.0, 134.0, 131.2, 128.1, 127.9, 122.9, 119.5, 116.7, 54.1; HRMS (ESI): calcd for C48H37N6O12 [M+H] 889.2469, found 889.2502. 4: m.p. 194–195 8C; 1H NMR (DMSO-d6, 600 MHz) d 13.76 (bs, 1 H), 11.82 (s, 1 H), 8.54 (d, J = 7.8 Hz, 1 H), 8.02 (dd, J = 7.8, 1.3 Hz, 1 H), 7.63 (t, J = 8.7 Hz, 1 H), 7.22 (t, J = 7.8 Hz, 1 H), 4.46 (s, 2 H); HRMS (ESI): calcd for C9H9ClNO3 [M+H] 214.0271, found 214.0246. 5: m.p. 268–270 8C; 1H NMR (DMSO-d6, 600 MHz) d 13.57 (bs, 1 H), 12.17 (bs, 1 H), 11.92 (s, 1 H), 8.70 (d, J = 8.2 Hz, 1 H), 7.94 (dd, J = 8.2, 1.8 Hz, 1 H), 7.70 (d, J = 9.1 Hz, 2 H), 7.60 (d, J = 8.7 Hz, 1 H), 7.23 (t, J = 5.9 Hz, 1 H), 7.13 (t, J = 8.2 Hz, 1 H), 6.63 (d, J = 8.7 Hz, 2 H), 3.96 (d, J = 5.9 Hz, 2 H); 13C NMR (DMSO-d6, 600 MHz) d 169.9, 169.1, 167.3, 151.9, 140.5, 134.2, 131.1, 122.7, 119.4, 118.5, 115.9, 111.5, 48.0; HRMS (ESI): calcd for C16H15N2O5 [M+H] 315.0981, found 315.0999.
Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives Sheng Biao Wan a, Zhe Lin Liu a, Di Chen b, Qing Ping Dou b, Tao Jiang a,* a
Key Laboratory of Marine Drug, Ministry of Education, Medical College, Ocean University of China, Qingdao 266003, China b The Prevention Program, Barbara Ann Karmanos Cancer Institute, and Department of Pathology, School of Medicine, Wayne State University, Detroit, MI, USA Received 25 April 2007
Abstract 11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid was obtained specifically by polyphosphorous acid catalyzed cyclization with optimal reaction conditions. Biological assays showed that it potentially inhibits the proteasomal chymotrypsin-like activity in vitro and suppresses breast cancer cell growth. # 2007 Tao Jiang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Cryptolepine; Trioligomer; Synthesis; Proteasome
Cryptolepine is an indoloquinoline alkaloid isolated from the west African climbing shrub Cryptolepis sanguinolenta [1]. It has been shown to have anti-tumor [2], anti-bacterial [3], anti-thrombotic [4], and anti-malarial [5] activities. In order to improve its bioavailability and find more potential anti-tumor compounds, several synthetic methods were developed to construct the indolequinoline scandold [6]. A facile strategy is polyphosphorous catalyzed cyclization. Modifications of cryptolepine at D ring with methyl or halo substitutes were performed with this synthetic tactic. However, there are no more study of cryptolepine analogs with electron withdrawing group at D ring. In this paper we report the successful synthesis of a cryptolepine analog with a carboxyl group at D ring (compound 1). Its inhibition of breast cancer cell growth and inhibition of a related molecular target proteasome were also tested. The synthetic route is shown in Scheme 1. Acylation of 2-aminobenzoic acid 3 by chloroacetyl chloride gave intermediate 4 with 90% yield. In literature, compound 4 usually condensed well with aniline which has methyl or halo substitutes in benzene. however, when condensed with 4-aminobenzoic acid which has a strong electron withdrawing group, the conversion was too low to obtain the desired compound 5 in benzene or even in DMF. Alternatively compound 4 reacted with 4-aminobenzoic acid in Na2CO3 aq. at 100 8C to afford the corresponding compound 5 with 78.9% yield. We have tried the cyclization of 5 in polyphosphoric acid (PPA) at 100–130 8C. Little conversion of intermediate 5 was observed from TLC at 100–110 8C. Compound 1 with 45% of yield was obtained at 110–120 8C because of the incompletely conversion, and an 18 member ring trioligomer 2 was dramatically isolated with 6% yield
* Corresponding author. E-mail address: [email protected] (T. Jiang). 1001-8417/$ – see front matter # 2007 Tao Jiang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2007.08.014
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S.B. Wan et al. / Chinese Chemical Letters 18 (2007) 1179–1181
Scheme 1. Synthetic route of compound 1. (a) Chloroacetyl chloride, DMF/dioxane, ice bath, 4 h, 90%; (b) Na2CO3, H2O, 90 8C, 3 h, 78.9%; (c) PPA, 110–120 8C, 1 h, 1 (45%), 2 (6%); (d) PPA, 130 8C, 2 h, 1 (67%).
from the crude products. The trioligomer 2 was purified by Chromatograph with Sephadex G-10, for it is more soluble in water than compound 1. The optimal condition is that the cyclization worked in PPA at 130 8C for 2 h to afford 67% of desired compounds 1, and no trioligomer 2 was isolated. The target molecular 1 and byproduct trioligomer 2 were determined by HRMS and NMR [12]. HRMS of compound 2 showed that it is a trioligomer of the condensation of intermediate 5, and 1H NMR disclosed that it is a symmetric 18 member macro ring, for the chemical shifts of D ring protons changed much more than that of A ring protons. The ubiquitin/proteasome pathway has been considered as an important target for anticancer drug development. The proteasome inhibitor Bortezomib (Velcade, PS-341) has been used in clinical trials and its anti-tumor activity has been reported in a variety of tumor models [7–9]. To examine whether compound 1 is capable of inhibiting the proteasome activity, we incubated compound 1 at various concentrations with extracted proteins from human breast cancer MDA-MB-231 cells containing 26S proteasome and a fluorogenic peptide substrate for 2 h at 37 8C. After incubation, the fluorescent production of hydrolyzed AMC groups was measured. The results showed that the proteasomal chymotrypsin-like activity was inhibited by 25.7, 47.3 and 63.2%, respectively, when compound 1 was used at 1, 10 and 50 mmol/L. It has been shown that inhibition of the proteasomal chymotrypsin-like activity is associated with induction of tumor cell growth arrest and/or apoptosis [10,11]. To determine whether proteasome inhibition by compound 1 causes suppression of cell proliferation, human breast cancer MDA-MB-231 cells were treated with indicated concentrations of compound 1 or equal volume of the vehicle DMSO for 24 h, followed by MTT assy. We found that compound 1 inhibited proliferation of MDA-MB-231 cells in a dose-dependent manner: by 21.0, 31.0 and 47.2%, respectively, when used at 1, 10 and 50 mmol/L. Acknowledgment This work was supported by National Basic Research Program of China (973 Program) (No. 2003CB71640). References [1] [2] [3] [4] [5] [6] [7] [8]
D.E. Bierer, S.R. King, et al. J. Med. Chem. 41 (1998) 894. K. Bonjean, L. Angenot, et al. Biochemistry 37 (1998) 5136. A. Paulo, M. Pimentel, S. Viegas, et al. J. Ethnopharmacol. 44 (1994) 73. A.O. Oyekan, S.Y. Ablordeppey, et al. Gen. Pharmacol. 24 (1993) 461. K. Cimanga, et al. J. Nat. Prod. 60 (1997) 688. J. Luo, D.M. Fort, G.M. Reaven, et al. Diabetic Med. 15 (1998) 367. Q.P. Dou, R.H. Goldfarb, IDrugs 5 (2002) 828. C.N. Papandreou, C.J. Logothetis, Cancer Res. 64 (2004) 5036.
S.B. Wan et al. / Chinese Chemical Letters 18 (2007) 1179–1181 [9] [10] [11] [12]
1181
R.C. Kane, A.T. Farrell, R. Sridhara, R. Pazdur, Clin. Cancer Res. 12 (2006) 2955. B. An, R.H. Goldfarb, R. Siman, Q.P. Dou, Cell Death Differ. 5 (1998) 1062. U.G. Lopes, P. Erhardt, R. Yao, J. Biol. Chem. 272 (1997) 12893. Melt point and spectral data of 11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid 1: m.p. > 300 8C; 1H NMR (DMSO-d6, 600 MHz) d 12.72 (bs, 1 H), 12.64 (s, 1 H), 12.13 (s, 1 H), 8.98 (s, 1 H), 8.35 (d, J = 8.0 Hz, 1 H), 8.04 (d, J = 8.8 Hz, 1 H), 7.74 (m, 2 H), 7.55 (d, J = 14.4 Hz, 1 H), 7.32 (m, 1 H); 13C NMR (DMSO-d6, 600 MHz) d 168.0, 167.7, 140.8, 139.3, 131.3, 129.9, 128.4, 125.4, 124.3, 123.9, 123.2, 121.6, 121.3, 118.1, 115.9, 114.9, 112.6; HRMS (ESI) calcd for C16H11N2O3 [M+H] 279.0769, found 279.0734. 2,8,14-triazatetracyclo[142,24,7,210, 3]tetracosa-4,6,10,12,18,19,21,23-nonaene-3,9,15-trione-2, 8,14-tri(2-acetyl-aminobenzoic acid) 2-[2-[4-carboxyl -(phenylamino)acetyl]amino]benzoic acid 2: m.p. 232–234 8C; 1H NMR (DMSO-d6, 600 MHz) d 12.03 (s, 3 H), 8.59 (d, J = 8.0 Hz, 3 H), 8.03 (dd, J = 8.0, 1.4 Hz, 3 H), 7.59 (t, J = 8.5 Hz, 3 H), 7.30(d, J = 8.5 Hz, 6 H), 7.24 (d, J = 8.5 Hz, 6 H), 7.17 (t, J = 8.0 Hz, 3 H), 4.56 (s, 6 H); 13C NMR (DMSO-d6, 600 MHz) d 170.8, 170.0, 166.9, 143.3, 140.5, 135.0, 134.0, 131.2, 128.1, 127.9, 122.9, 119.5, 116.7, 54.1; HRMS (ESI): calcd for C48H37N6O12 [M+H] 889.2469, found 889.2502. 4: m.p. 194–195 8C; 1H NMR (DMSO-d6, 600 MHz) d 13.76 (bs, 1 H), 11.82 (s, 1 H), 8.54 (d, J = 7.8 Hz, 1 H), 8.02 (dd, J = 7.8, 1.3 Hz, 1 H), 7.63 (t, J = 8.7 Hz, 1 H), 7.22 (t, J = 7.8 Hz, 1 H), 4.46 (s, 2 H); HRMS (ESI): calcd for C9H9ClNO3 [M+H] 214.0271, found 214.0246. 5: m.p. 268–270 8C; 1H NMR (DMSO-d6, 600 MHz) d 13.57 (bs, 1 H), 12.17 (bs, 1 H), 11.92 (s, 1 H), 8.70 (d, J = 8.2 Hz, 1 H), 7.94 (dd, J = 8.2, 1.8 Hz, 1 H), 7.70 (d, J = 9.1 Hz, 2 H), 7.60 (d, J = 8.7 Hz, 1 H), 7.23 (t, J = 5.9 Hz, 1 H), 7.13 (t, J = 8.2 Hz, 1 H), 6.63 (d, J = 8.7 Hz, 2 H), 3.96 (d, J = 5.9 Hz, 2 H); 13C NMR (DMSO-d6, 600 MHz) d 169.9, 169.1, 167.3, 151.9, 140.5, 134.2, 131.1, 122.7, 119.4, 118.5, 115.9, 111.5, 48.0; HRMS (ESI): calcd for C16H15N2O5 [M+H] 315.0981, found 315.0999.