WO2012110959A1 - 2-phenyl benzothiazole linked imidazole compounds as potential anticancer agents and process for the preparation thereof - Google Patents

2-phenyl benzothiazole linked imidazole compounds as potential anticancer agents and process for the preparation thereof Download PDF

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WO2012110959A1
WO2012110959A1 PCT/IB2012/050678 IB2012050678W WO2012110959A1 WO 2012110959 A1 WO2012110959 A1 WO 2012110959A1 IB 2012050678 W IB2012050678 W IB 2012050678W WO 2012110959 A1 WO2012110959 A1 WO 2012110959A1
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phenyl
imidazol
thiazole
cell line
compounds
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PCT/IB2012/050678
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French (fr)
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Kamal Ahmed
Ratna Reddy CHALLA
Prabhakar SINGARABOINA
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Council Of Scientific & Industrial Research
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Priority to US13/696,549 priority Critical patent/US9187467B2/en
Priority to EP12709964.6A priority patent/EP2556072B1/en
Publication of WO2012110959A1 publication Critical patent/WO2012110959A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D417/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00
    • C07D417/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00 containing two hetero rings
    • C07D417/10—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00 containing two hetero rings linked by a carbon chain containing aromatic rings
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P35/00—Antineoplastic agents
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P35/00—Antineoplastic agents
    • A61P35/02—Antineoplastic agents specific for leukemia
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P35/00—Antineoplastic agents
    • A61P35/04—Antineoplastic agents specific for metastasis
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D417/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00
    • C07D417/14—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and sulfur atoms as the only ring hetero atoms, not provided for by group C07D415/00 containing three or more hetero rings

Definitions

  • the present invention relates to 2-phenyl benzothiazole linked imidazole compounds of general formula A as potential anticancer agents and a process for the preparation thereof.
  • R H or OCH 3 ;
  • Ri H, F or OCH 3 ;
  • R 2 H or OCH 3 ;
  • R 3 H, NH 2 , F or OCH 3;
  • R4 H , NH 2 or OCH 3 ;
  • R 5 H, NH 2 , F, CF 3 or OCH 3 ;
  • R 7 H or OCH 3 ;
  • R 8 H or OCH 3 .
  • Microtubules are composed of dynamic polymers of tubulin which are involved in various cellular processes such as cell division and cell shape, especially in induction of apoptosis. Rapidly dividing cells are more susceptible to tubulin polymerization inhibitors than non- dividing cells and impair microtubule dynamics and consequently arrest cells during mitosis (Jordan, M. A.; Hadfield, J. A.;. Lawrence, N. J.; McGown, A. T. Med. Res. Rev., 1998, 18, 259-296). The mode of action of tubulin inhibitors is that they bind to the tubulin binding sites thereby stabilizing or destabilizing microtubule assembly. Disruption of microtubule leads to cell cycle arrest at G2/M phase followed by apoptotic cell death (Pasquier , E.;. Kavallaris, M. IUBMB Life., 2008, 60, 165-170).
  • Combretastatins are a class of naturally occurring compounds isolated from the African willow tree combretum caffrum has shown considerable interest and shown to be potent tubulin inhibitor and attracted the medicinal chemists in the design of various combretastatins analogs (Pettit, G. R.; Singh, S. B.; Hamel, E.; Lin, C. M.; Alberts, D. S.; Garcia Kendall, D. Experientia 1989, 45, 209).
  • Combretastatin A-4 (1) a simple cis stilbene has been reported to exhibit potent cytotoxicity against various cancer cell lines including multi drug resistant cells exhibiting excellent anticancer activity and found to be inhibit polymerization of tubulin by binding to the colchicine site.
  • CA-4 failed to show in vivo efficacy due to its poor water solubility and its pro drug of CA-4 disodium phosphate derivative (CA-4P) exhibiting promising results and presently in clinical trails (Buolamwini, J. K. Curr. Opin. Chem. Biol., 1999, 3, 500-509).
  • SAR structure-activity relationship
  • Benzothiazoles are a class of compounds comprising various activities including anticancer activity wherein 2-(4-Aminophenyl) benzothiazoles (3) and 2-(4-hydroxyphenyl) benzothiazoles are novel class of potent and selective antitumor agents and found to exhibit antitumor activity particularly against certain breast carcinoma cell lines MCF-7, MDA 468 with IC 50 ⁇ 1 nM to be promising anticancer activity both in vitro and invivo also (Shi, D. F.; Bradshaw, T. D.; Wrigley, S.; McCall, C. J.; Lelieveld, P.; Fichtner, I.; Stevens, M. F. J. Med. Chem. 1996, 39, 3375-3384).
  • 2-phenyl benzothiazole linked imidazole compound were designed and synthesized comprising of 2-phenyl benzothiazoles and imidazole moiety by forming 1, 5 oriented 2-phenyl benzothiazole and various phenyl ring and also various hetero aromatic ring systems maintaining cis conformation which are expected to possess promising anticancer activity. Additionally, these are structurally simple small molecules.
  • R 7 is comprising of imidazole ring with different functional groups like hydroxy, hydroxy alkyl, acyl, acetamide, carboxyl, cyano, carboxamide, sulfonamide, sulfone, oxide, alkoxy and nitro.
  • the structure is comprising of imidazole ring with aryl and heteroaryl ring systems which are present on position-5. These are not included in the cited patent US 7384966 (shown in below figure).
  • R hydroxy, hydroxy alkyl, acyl
  • R substituted aryl, heteroaryl acetamide, carboxyl, cyano, carboxamide,
  • the main objective of the present invention is to provide 2-phenyl benzothiazole linked imidazole compounds of general formula A useful as anticancer agent.
  • Another objective of the present invention is to provide process for the preparation of 2- phenyl benzothiazole linked imidazole compounds of general formula A.
  • R H or OCH 3 ;
  • Ri H, F or OCH 3 ;
  • R 2 H or OCH 3 ;
  • R 3 H, NH 2 , F or OCH 3;
  • R4 H , NH 2 or OCH 3 ;
  • R 5 H, NH 2 , F, CF 3 or OCH 3 ;
  • R 7 H or OCH 3 ;
  • R 8 H or OCH 3 .
  • representative group of 2-phenyl benzothiazole linked imidazole compounds are:
  • representative compounds are:
  • said 2-phenyl benzothiazole linked imidazole compounds are useful as anticancer agent.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against sixty human cancer cell lines, derived from nine cancer cell types leukemia cell line, non small cell lung cell line, colon cell line, CNS cell line, renal cell line, prostate cell line, ovarian cell line, breast and melanoma cell line.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against six leukemia cancer cell lines (CCRF-CEM, HL-60, K-562, MOLT-4, SR and RPMI-8226) for GI 50 are in the range of 2.50 to 6.92, 3.22 to 3.30, 3.03 to 5.88, 3.24 to 5.39, 2.43 to 7.14, 0.989 to 1.40, and 2.20 to 4.00 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against nine Non-small cell lung cancer cell line (A549/ATCC, EKVX, HOP-62, HOP-92, NCI-H226, NCI-H23, NCI- H322M, NCI-H460 and NCI-H522) for GI 50 are in the range of 5.47 to 49.3, 2.49 to 18.5, 5.26 to 41.8, 3.27 to 75.9, 1.87 to 86.5, 0.446 to 5.13, and 3.37 to 25.7 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against seven colon cancer cell line (COLO 205, HCC-2998, HCT-116, HCT-15, HT29, KM12 and SW-620) for GI 50 are in the range of 4.36 to 82.3, 4.52 to 4.93, 5.48 to 7.13, 3.92 to 5.96, 3.76 to 13.7 , 2.79 to 3.81, and 2.94 to 6.21 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against six CNS cancer cell line (SF-268, SF-295, SF-539, SNB-19, SNB-75 and U251) for GI 50 are in the range of 12.6 to 75.9, 2.40 to 11.3, 7.00 to 9.96, 4.15 to 8.59, 3.64 to 22.1, 1.53 to 12.3, and 4.44 to 52.3 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against eight renal cancer cell line (786-0, A498, ACHN, CAKI-1, SN12C, TK-10 UO-31 and RXF 393) for GI 50 are in the range of 0.0432 to 38.8, 2.13 to 16.8, 2.15 to 3.17, 1.83 to 9.40, 1.94 to 31.9, 1.41 to 8.95, and 1.99 to 9.44 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against two prostate cancer cell line (PC-3, DU-145) for GI 50 are 3.47 to 14.3, 3.66 to 27.9, 2.54, 3.17 to 31.1, 3.02 to 7.25, and 2.59 to 6.38 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against seven ovarian cancer cell line (IGROV1, OVCAR-3, OVCAR-4, OVCAR-5, OVCAR-8, NCI/ADR-RES and SK- OV-3) for GI 50 are in the range of 5.71 to 30.6, 2.87 to 14.5, 3.85 to 56.1, 3.25 to 5.87, 6.07 to 49.9, 1.61 to 34.3, and 3.12 to 6.29 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against six breast cancer cell line (MCF7, MDA-MB-231/ATCC, HS 578T, BT-549JD-47D and MDA-MB-468) for GI 50 are in the range of 7.98 to 32.2, 3.09 to 9.01, 3.78 to 28.4, 3.27 to 5.23, 4.02 to 20.9, 1.59 to 5.36, and 3.02 to 28.3 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against nine melanoma cancer cell line (LOX IMVI, MALME-3M, M14, MDA-MB-435, SK-MEL-2, SK-MEL-28, SK- MEL-5, UACC-257 and UACC-62) for GI 50 are in the range of 4.11 to 39.7, 1.53 to 9.69, 3.61 to 59.8, 2.46 to 7.91, 2.85 to 31.6, 0.710 to 6.40, and 1.73 to 13.7 ⁇ respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting mean graph midpoint values (MG MID) of logioGIso to all the cell lines are in the range of -5.38 to -4.52,-5.48 to -4.0,-5.13 to -4.39,-5.42 to -4.78,-5.43 to -4.82,-5.92 to -5.24 and-5.49 to-4.53 respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting mean graph midpoint values (MG MID) of logioLCso to all the cell lines are in the range of -4.00 to -4.03, -4.00, -4.00, -4.00, - 4.00to -4.18, -4.00 to -4.09, -4.00 respectively at an exposure period of at least 48 h.
  • compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting mean graph midpoint values (MG MID) of logioTGI to all the cell lines are in the range of -4.00 to -4.41, -4.00 to -4.19, -4.00 to -4.06, -4.00, -4.00 to - 4.54, -4.00 to to -4.26 and -4.00 to -4.11 respectively at an exposure period of at least 48 h.
  • R hydrogen or methoxy
  • R hydrogen or methoxy
  • Ri hydrogen, methoxy or fiuoro
  • Ri hydrogen, methoxy or fluoro
  • step (iii) treating thioamides (19a-d) as obtained in step (ii) with potassium ferricyanide (1 :4) in aqueous sodium hydroxide solution under reflux conditions for 2 to 3h to obtain the substituted 2-(4-nitro phenyl benzothiazole) of formula 20a-d; iv. reducing substituted 2-(4-nitro phenyl benzothiazole) of formula 20a-d with SnCl 2 .2H 2 0 to obtain amine compounds (21a-d);
  • step (iv) treating amine compounds (21a-d) as obtained in step (iv) with substituted aldehydes in the presence of catalytic amount of acetic acid (2-3 drops) in 15 to 20 mL of ethanol solution under reflux conditions to obtain imine compounds followed by treatment with /?-toulenesulfonyl methy isocyanide to obtain nitro intermediates (25a-l) and compound of formula 4a-g to 7a-g and 8a-b to 15a-b; vi. reducing nitro intermediate as obtained in step (v) with SnCl 2 .2H 2 0 in ethanol to obtain compound of formula 4h-j to 7h-j.
  • substituted aldehydes used is selected from the group consisting of 22a-j, 23a-b and 24a-b.
  • R7— H; R4— Rg— OCH3 24a: X NH;
  • solvent used are selected from ethyl acetate, hexane, chloroform or methanol.
  • Figure 1 represents FACS analysis of cell cycle distribution of MCF-7 cells after treatment with compounds CA-4, 21a, 2 Id, 4c, 6d, 6e, 6f, 7d, 7h and 7j at 2 ⁇ concentration for 24h and control cells are the cells treated with DMSO (0.25%).
  • Figure 2 represents effect of compound 7d, the effective compound on the microtubule network of MCF-7 cells untreated cells (Con), nocodazole (Noc) and 7d at 2 ⁇ concentration. Microtubules and unassembled tubulin are shown in green and DNA was was stained with nuclear dye DAPI( 4,6-diamidino-2-phenylindole) is shown in blue colour.
  • Figure 3 represents effect of compound 7d and 7h on p21 and caspase-9.
  • MCF-7 cells were treated with 2 ⁇ concentration of compounds 7d and 7h for 24h. The cell lysates were collected and probed with anti-bodies against p21 and caspase-9. beta-actin was used as loading control.
  • Con Control (untreated).
  • Scheme 1 represent schematic diagram for the preparation of compound of general formula A wherein reagent and conditions are (i) Pyridine, reflux, 2h; (ii) Lawessons reagent, toluene, reflux, 8h; (iii) K3[FeCN) 6 ], Aq.NaOH, 2H; (IV) SnCl 2 .2H 2 0, ethanol, reflux, 2h; (v)ethanol, AcOH (Cat), reflux; (vi)p-toluene sulfonyl methyl isocyanide, K 2 CO 3 , DME:MEOH (1 :2) reflux, 12h; (vii) SnCl 2 .2H 2 0, ethanol, reflux, 2h.
  • reagent and conditions are (i) Pyridine, reflux, 2h; (ii) Lawessons reagent, toluene, reflux, 8h; (iii) K3[FeCN) 6 ], Aq.NaOH, 2H; (IV) S
  • Benzothiazole ring cyclization takes place in the presence of K 3 [Fe(CN)6] and in aqueous NaOH for 2 to 3h under reflux conditions;
  • NCI National Cancer Institute
  • the compounds were evaluated for anticancer activity against sixty human cancer cells derived from nine cancer types (leukemia cell line, non-small-cell lung cell line, colon cell line, CNS cell line, melanoma cell line, ovarian cell line, prostate cell line, renal cancer cell line and breast cancer cell line) as shown in Table 1.
  • leukemia cell line non-small-cell lung cell line, colon cell line, CNS cell line, melanoma cell line, ovarian cell line, prostate cell line, renal cancer cell line and breast cancer cell line
  • SRB sulforho damine B
  • Table 1 The GI 50 ( ⁇ ) values for compounds 3a, 3b 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines.
  • OVCAR-8 15.2 14.5 21.2 a 13.4 4.23 6.19
  • Table 2 The mean graph midpoint values (MG MID) of Logio GI 50 (log values of concentration in mol/L causing 50% inhibition of net cell growth) values for compounds 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines. Cancer cell lines Logio GI 7d 7h 7j
  • Table 3 The mean graph midpoint values (MG MID) of Logio LC 50 values (log value of the concentration of compounds leading to 50% net cell death) for compounds 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines.
  • Table 4 The mean graph midpoint values (MG MID) of logioTGI (log value of concentration of the compound resulting in total inhibition of net cell growth) for compounds 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines.
  • MCF-7 cells were treated with 7d, 7h (the effective compounds of cell cycle arrest) 21a, 21d and CA-4 at 2 ⁇ concentration.
  • Western blot analysis revealed that treatment of MCF-7 cells with compounds caused increase in p21 and caspase-9 protein (Figure 3).
  • the present invention provides 2-phenyl benzothiazole linked imidazole compounds of general formula A.

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Abstract

The present invention provides 2-phenyl benzothiazole linked imidazole compounds of formula A as anti cancer agent against fifty three human cancer cell lines. (General formula A) wherein (II) R=H or OCH3; R1=H, F or OCH3; R2=H or OCH3; R3=H, NH2, F or OCH3; R4=H, NH2 or OCH3; R5=H, NH2, F, CF3 or OCH3; R6=H or OCH3; R7=H or OCH3; R8=H or OCH3.

Description

2-PHENYL BENZOTHIAZOLE LINKED IMIDAZOLE COMPOUNDS AS POTENTIAL ANTICANCER AGENTS AND PROCESS FOR THE PREPARATION THEREOF FIELD OF THE INVENTION
The present invention relates to 2-phenyl benzothiazole linked imidazole compounds of general formula A as potential anticancer agents and a process for the preparation thereof.
Figure imgf000002_0001
General formula A
wherein
Figure imgf000002_0002
R=H or OCH3;
Ri=H, F or OCH3;
R2=H or OCH3;
R3=H, NH2, F or OCH3;
R4=H , NH2 or OCH3;
R5=H, NH2, F, CF3 or OCH3;
Rs=H or OCH3;
R7=H or OCH3;
R8=H or OCH3.
The structural formula of the representative group of 2-phenyl benzothiazole linked imidazole c m ounds are given below:
Figure imgf000002_0003
BACKGROUND OF THE INVENTION
Microtubules are composed of dynamic polymers of tubulin which are involved in various cellular processes such as cell division and cell shape, especially in induction of apoptosis. Rapidly dividing cells are more susceptible to tubulin polymerization inhibitors than non- dividing cells and impair microtubule dynamics and consequently arrest cells during mitosis (Jordan, M. A.; Hadfield, J. A.;. Lawrence, N. J.; McGown, A. T. Med. Res. Rev., 1998, 18, 259-296). The mode of action of tubulin inhibitors is that they bind to the tubulin binding sites thereby stabilizing or destabilizing microtubule assembly. Disruption of microtubule leads to cell cycle arrest at G2/M phase followed by apoptotic cell death (Pasquier , E.;. Kavallaris, M. IUBMB Life., 2008, 60, 165-170).
Combretastatins are a class of naturally occurring compounds isolated from the African willow tree combretum caffrum has shown considerable interest and shown to be potent tubulin inhibitor and attracted the medicinal chemists in the design of various combretastatins analogs (Pettit, G. R.; Singh, S. B.; Hamel, E.; Lin, C. M.; Alberts, D. S.; Garcia Kendall, D. Experientia 1989, 45, 209). Combretastatin A-4 (1) a simple cis stilbene has been reported to exhibit potent cytotoxicity against various cancer cell lines including multi drug resistant cells exhibiting excellent anticancer activity and found to be inhibit polymerization of tubulin by binding to the colchicine site. But CA-4 failed to show in vivo efficacy due to its poor water solubility and its pro drug of CA-4 disodium phosphate derivative (CA-4P) exhibiting promising results and presently in clinical trails (Buolamwini, J. K. Curr. Opin. Chem. Biol., 1999, 3, 500-509). The structure-activity relationship (SAR) information confirmed the importance of cis-stereochemistry and trimethoxy substituents in the A-ring and a new combretastatin derivatives with B-ring modifications by replacement of phenyl group with benzo[b]thiophene and benzofuran combretastatin analogues (ST2151) and (ST2179) and their phosphate prodrugs were synthesized and exhibiting high antitumor activityin both in vitro and in vivo models (Simoni, D.; Romagnoli, R.; Baruchello, R.; Rondanin, R.; Rizzi, M.; Pavani, M. G; Alloatti, D.; Giannini, G; Marcellini, M.; Riccioni, T.; Castorina, M.; Guglielmi, M. B.; Bucci, F.; Carminati, P.; Pisano, C. J. Med. Chem. 2006, 49, 3143-3152). Various series of compounds with heterocycles in place of the cis double bond in combretastatin A-4 (CA-4) furnished various novel heterocyclic CA-4 analogues. These compound showing anticancer activity and also antitubulin activity in a variety of tumor models while retaining the characteristics of CA-4. These compounds include where tetrazole ring could replace the cis double bond to maintain potent cytotoxicity. All these compounds showed excellent antitumor activities against the colon 26 murine tumors when given intravenously (Ohsumi, K.; Hatanaka, T.; Fujita, K.; Nakagawa, R.; Fukuda, Y.; Nihei, Y.; Suga, Y.; Morinaga, Y.; Akiyama, Y.; Tsuji, T. Bioorg. Med. Chem. Lett. 1998, 8, 3153). Moreover a novel series of compounds consisting of 1,2- and 1,5 substituted five-membered aromatic heterocycles such as imidazole, oxazole, and pyrazole to mimic the cis double bond in CA-4 were synthesized particularly based on 1,5 diphenylsubstituted imidazoles (2) these compounds exhibited significant anticancer activity compared to that CA-4 (Wang, L.; Woods, K.W.; Li, Q.' Barr, K. J.; McCroskey, R. W.; Hannick, S. M.; Gherke, L.; Credo, R. B.; Hui, Y. H.; Marsh, K.; Warner, R.; Lee, J. Y.; Zielinski-Mozng, N.; Frost, D.; Rosenberg, S. H.; Sham, H. L. J. Med. Chem. 2002, 45, 1697-1711).
Benzothiazoles are a class of compounds comprising various activities including anticancer activity wherein 2-(4-Aminophenyl) benzothiazoles (3) and 2-(4-hydroxyphenyl) benzothiazoles are novel class of potent and selective antitumor agents and found to exhibit antitumor activity particularly against certain breast carcinoma cell lines MCF-7, MDA 468 with IC50 <1 nM to be promising anticancer activity both in vitro and invivo also (Shi, D. F.; Bradshaw, T. D.; Wrigley, S.; McCall, C. J.; Lelieveld, P.; Fichtner, I.; Stevens, M. F. J. Med. Chem. 1996, 39, 3375-3384). Various fluorinated and 2-(3,4-dimethoxyphenyl)-5- fluorobenzothiazole were reported to be anticancer agents and these compounds shown to exhibit potent and selective inhibitory activity against lung, colon, and breast cancer cell lines. (Hutchinson, A.; Chua, M.; Browne, H. L.; Trapani, V.; Bradshaw, T. D; Westwell, A. D; Stevens, M. F. J. Med. Chem. 2001, 44, 1446-1455" and "Mortimer, C. G.; Wells, G.; Crochard, J. P.; Stone, E. L.; Bradshaw, T. D.; Stevens, M. F.; Westwell, A. D. J. Med. Chem. 2006, 49, 179-185).
Keeping this aspect in mind, 2-phenyl benzothiazole linked imidazole compound were designed and synthesized comprising of 2-phenyl benzothiazoles and imidazole moiety by forming 1, 5 oriented 2-phenyl benzothiazole and various phenyl ring and also various hetero aromatic ring systems maintaining cis conformation which are expected to possess promising anticancer activity. Additionally, these are structurally simple small molecules.
Figure imgf000005_0001
1 Combretastatin 2 Imidazo Combretastatin
Figure imgf000005_0002
4-amino phenyl benzothiazoles 2-phenyl benzothiazole linked imidazoles (general formula V)
References may be made to Patent US 7384966, wherein compound of formula X has been reported.
Figure imgf000005_0003
General formula X
The structures of patent proposal are different with the compounds of general formula X. In general formula X, R7 is comprising of imidazole ring with different functional groups like hydroxy, hydroxy alkyl, acyl, acetamide, carboxyl, cyano, carboxamide, sulfonamide, sulfone, oxide, alkoxy and nitro. Where as in subject patent proposal, the structure is comprising of imidazole ring with aryl and heteroaryl ring systems which are present on position-5. These are not included in the cited patent US 7384966 (shown in below figure).
Structure of present propasal Structure of patent US 7384966
Figure imgf000005_0004
R = hydroxy, hydroxy alkyl, acyl,
R = substituted aryl, heteroaryl acetamide, carboxyl, cyano, carboxamide,
sulfonamide, sulfone, oxide, alkoxy, nitro
Figure imgf000005_0005
Ri = different substitutions OBJECTIVES OF THE INVENTION
The main objective of the present invention is to provide 2-phenyl benzothiazole linked imidazole compounds of general formula A useful as anticancer agent.
Another objective of the present invention is to provide process for the preparation of 2- phenyl benzothiazole linked imidazole compounds of general formula A.
SUMMARY OF THE INVENTION
Accordingly, present invention provides compounds of general formula A
Figure imgf000006_0001
General formula A
wherein
Figure imgf000006_0002
R=H or OCH3;
Ri=H, F or OCH3;
R2=H or OCH3;
R3=H, NH2, F or OCH3;
R4=H , NH2 or OCH3;
R5=H, NH2, F, CF3 or OCH3;
Rs=H or OCH3;
R7=H or OCH3;
R8=H or OCH3.
In an embodiment of the present invention, representative group of 2-phenyl benzothiazole linked imidazole compounds are:
Figure imgf000006_0003
In yet another embodiment of the present invention, representative compounds are:
6-Fluoro-2-(4-(5-phenyl- lH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (4a); 6-Fluoro-2-(4-(5-(4-(trifluoromethyl)phenyl)-lH-imidazol-lyl)phenyl)benzo[(i] thiazole (4b); 6-Fluoro-2-(4-(5-(4-fluoro-3-methoxyphenyl)- IH-imidazol- 1 - yl)phenyl)benzo[<i]thiazole(4c);
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-fluorobenzo[(i]thiazole (4d); 2-(4-(5-(3,4-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-fluorobenzo[(i]thiazole (4e); 6-Fluoro-2-(4-(5-(3,4,5-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (4f); 6-Fluoro-2-(4-(5-(2,4,6-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[ ]thiazole (4g);
4- (l-(4-(6-Fluorobenzo[<i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (4h);
2-( 1 -(4-(6-Fluorobenzo [ djthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)-5 -methoxybenzeneamine (41)
5- (l-(4-(6-Fluorobenzo[<i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)-2-methoxy benzenamine
(4j);
6- Methoxy-2-(4-(5 -phenyl- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (5a);
6-Methoxy-2-(4-(5 -(4-(trifluoromethyl)phenyl)- lH-imidazo 1- 1 -yl)phenyl)benzo [ Jthiazo le (5b);
2-(4-(5-(4-Fluoro-3-methoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i]thiazole (5c);
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i]thiazole (5d); 2-(4-(5-(3,4-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i]thiazole (5e) ; 6-Methoxy-2-(4-(5-(3,4,5-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (5f); 6-Methoxy-2-(4-(5-(2,4,6-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole
(5g);
4- (l-(4-(6-Methoxybenzo[<i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (5h)
5 - Methoxy-2-( 1 -(4-(6-methoxybenzo [ Jthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)benzene amine (5i);
2-Methoxy-5 -( 1 -(4-(6-methoxybenzo [ Jthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)benzene amine (5j);
5,7-Dimethoxy-2-(4-(5-phenyl-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (6a);
5,7-Dimethoxy-2-(4-(5-(4-(trifluoromethyl)phenyl)-lH-imidazol-l-yl)phenyl)benzo[(i] thiazole (6b);
2-(4-(5-(4-Fluoro-3-methoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i] thiazole (6c)
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i]thiazole 2-(4-(5-(3,4-Dimethoxyphenyl)-lH-m
(6e);
5,7-Dimethoxy-2-(4-(5-(3,4,5-trimethoxyphenyl)- lH-imidazol-l-yl)phenyl)benz
5,7-Dimethoxy-2-(4-(5-(2,4,6-trimethoxyphenyl)- lH-imidazol-l-yl)phenyl)benzo
(6g);
4- (l-(4-(5,7-Dimethoxybenzo[ ]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (6h); 2-(l-(4-(5,7-Dimethoxybenzo[(i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)-5- methoxybenzenamine (6i);
5- (l-(4-(5,7-Dimethoxybenzo[ ]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)-2-methoxy benzenamine (6j);
5,6,7-Trimethoxy-2-(4-(5-phenyl-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (7a);
5,6,7-Trimethoxy-2-(4-(5-(4-(trifluoromethyl)phenyl)-lH-imidazol-l-yl)phe
thiazole (7b);
2-(4-(5-(4-Fluoro-3-methoxyphenyl)-lH-imidaz
[djthiazole (7c);
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imid^
(7d);
2-(4-(5-(3,4-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,6,7-trimethoxybenzo[^
(7e);
5,6,7-Trimethoxy-2-(4-(5-(3,4,5-trime
thiazole (If);
5,6,7-Trimethoxy-2-(4-(5-(2,4,6-trimem^
thiazole (7g);
4-(l-(4-(5,6,7-Trimethoxybenzo[d]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (7h); 2-( 1 -(4-(5 ,7-Dimethoxybenzo [ Jthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)-5 -methoxy benzenamine (7i);
2-Methoxy-5-(l-(4-(5,6,7-trimethoxybenzo[(i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl) benzeneamine (7j);
2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-6-fluorobenzo[ ]thiazole (8a);
6- Fluoro-2-(4-(5-(5-methoxy- lH-indol-3-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (8b); 2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i]thiazole (9a);
6-Methoxy-2-(4-(5-(5-methoxy- lH-indol-3-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (9b); 2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i]thiazole (10a); 5,7-Dimethoxy-2-(4-(5-(5-methoxy- lH-indol-3-yl)- lH-imidazol- 1 -yl)phenyl)benzo[<i] thiazole (10b);
2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-5,6,7-trimethoxybenzo[(i]thiazole (11a); 5 ,6,7-Trimethoxy-2-(4-(5 -(5 -methoxy- 1 H-indo 1-3 -yl)- IH-imidazo 1- 1 -yl)phenyl)benzo [d] thiazole (lib);
6-Fluoro-2-(4-(5-(5-nitro- lH-pyrrol-2-yl)- lH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (12a); 6-Fluoro-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (12b); 6-Methoxy-2-(4-(5-(5-nitro- lH-pyrrol-2-yl)- lH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole
(13a);
6-Methoxy-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (13b);
5,7-Dimethoxy-2-(4-(5-(5-nitro-lH-pyrrol-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (14a);
5,7-Dimethoxy-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (14b);
5,6,7-Trimethoxy-2-(4-(5-(5-nitro- lH-pyrrol-2-yl)- lH-imidazol- 1 -yl)phenyl)benzo[<i] thiazole (15a);
5,6,7-Trimethoxy-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i Jthiazole (15b).
In yet another embodiment of the resent invention, structural formulae of the representative compounds are:
Figure imgf000010_0001
Figure imgf000011_0001
Figure imgf000012_0001
In yet another embodiment of the present invention, said 2-phenyl benzothiazole linked imidazole compounds are useful as anticancer agent. In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against sixty human cancer cell lines, derived from nine cancer cell types leukemia cell line, non small cell lung cell line, colon cell line, CNS cell line, renal cell line, prostate cell line, ovarian cell line, breast and melanoma cell line.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against six leukemia cancer cell lines (CCRF-CEM, HL-60, K-562, MOLT-4, SR and RPMI-8226) for GI50 are in the range of 2.50 to 6.92, 3.22 to 3.30, 3.03 to 5.88, 3.24 to 5.39, 2.43 to 7.14, 0.989 to 1.40, and 2.20 to 4.00 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against nine Non-small cell lung cancer cell line (A549/ATCC, EKVX, HOP-62, HOP-92, NCI-H226, NCI-H23, NCI- H322M, NCI-H460 and NCI-H522) for GI50 are in the range of 5.47 to 49.3, 2.49 to 18.5, 5.26 to 41.8, 3.27 to 75.9, 1.87 to 86.5, 0.446 to 5.13, and 3.37 to 25.7 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against seven colon cancer cell line (COLO 205, HCC-2998, HCT-116, HCT-15, HT29, KM12 and SW-620) for GI50 are in the range of 4.36 to 82.3, 4.52 to 4.93, 5.48 to 7.13, 3.92 to 5.96, 3.76 to 13.7 , 2.79 to 3.81, and 2.94 to 6.21 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against six CNS cancer cell line (SF-268, SF-295, SF-539, SNB-19, SNB-75 and U251) for GI50 are in the range of 12.6 to 75.9, 2.40 to 11.3, 7.00 to 9.96, 4.15 to 8.59, 3.64 to 22.1, 1.53 to 12.3, and 4.44 to 52.3 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against eight renal cancer cell line (786-0, A498, ACHN, CAKI-1, SN12C, TK-10 UO-31 and RXF 393) for GI50 are in the range of 0.0432 to 38.8, 2.13 to 16.8, 2.15 to 3.17, 1.83 to 9.40, 1.94 to 31.9, 1.41 to 8.95, and 1.99 to 9.44 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against two prostate cancer cell line (PC-3, DU-145) for GI50 are 3.47 to 14.3, 3.66 to 27.9, 2.54, 3.17 to 31.1, 3.02 to 7.25, and 2.59 to 6.38 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against seven ovarian cancer cell line (IGROV1, OVCAR-3, OVCAR-4, OVCAR-5, OVCAR-8, NCI/ADR-RES and SK- OV-3) for GI50 are in the range of 5.71 to 30.6, 2.87 to 14.5, 3.85 to 56.1, 3.25 to 5.87, 6.07 to 49.9, 1.61 to 34.3, and 3.12 to 6.29 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against six breast cancer cell line (MCF7, MDA-MB-231/ATCC, HS 578T, BT-549JD-47D and MDA-MB-468) for GI50 are in the range of 7.98 to 32.2, 3.09 to 9.01, 3.78 to 28.4, 3.27 to 5.23, 4.02 to 20.9, 1.59 to 5.36, and 3.02 to 28.3 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting an in vitro anticancer activity against nine melanoma cancer cell line (LOX IMVI, MALME-3M, M14, MDA-MB-435, SK-MEL-2, SK-MEL-28, SK- MEL-5, UACC-257 and UACC-62) for GI50 are in the range of 4.11 to 39.7, 1.53 to 9.69, 3.61 to 59.8, 2.46 to 7.91, 2.85 to 31.6, 0.710 to 6.40, and 1.73 to 13.7 μΜ respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting mean graph midpoint values (MG MID) of logioGIso to all the cell lines are in the range of -5.38 to -4.52,-5.48 to -4.0,-5.13 to -4.39,-5.42 to -4.78,-5.43 to -4.82,-5.92 to -5.24 and-5.49 to-4.53 respectively at an exposure period of at least 48 h. In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting mean graph midpoint values (MG MID) of logioLCso to all the cell lines are in the range of -4.00 to -4.03, -4.00, -4.00, -4.00, - 4.00to -4.18, -4.00 to -4.09, -4.00 respectively at an exposure period of at least 48 h.
In yet another embodiment of the present invention, compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j exhibiting mean graph midpoint values (MG MID) of logioTGI to all the cell lines are in the range of -4.00 to -4.41, -4.00 to -4.19, -4.00 to -4.06, -4.00, -4.00 to - 4.54, -4.00 to to -4.26 and -4.00 to -4.11 respectively at an exposure period of at least 48 h.
In an embodiment, a process for the preparation of 2-phenyl benzothiazole linked imidazole compounds of general formula A comprising the steps of:
i. adding 4-nitrobenzoyl chloride (17) to a stirred solution of substituted anilines (16a-d) in the ratio ranging between 1.5: 1 to 1 : 1 in pyridine and reflux for 2 to 3h to obtain coupled amide of formula 18a-d
Figure imgf000015_0001
R = hydrogen or methoxy; R = hydrogen or methoxy;
Ri = hydrogen, methoxy or fiuoro; Ri= hydrogen, methoxy or fluoro;
R2 = hydrogen or methoxy; R2 = hydrogen or methoxy. ii. treating the amide of formula (18a-d) as obtained in step (i) with Lawesson's reagent, in toluene under reflux conditions for 6 to 8 fir to obtain the corresponding thioamides (19a-d);
Figure imgf000015_0002
iii. treating thioamides (19a-d) as obtained in step (ii) with potassium ferricyanide (1 :4) in aqueous sodium hydroxide solution under reflux conditions for 2 to 3h to obtain the substituted 2-(4-nitro phenyl benzothiazole) of formula 20a-d; iv. reducing substituted 2-(4-nitro phenyl benzothiazole) of formula 20a-d with SnCl2.2H20 to obtain amine compounds (21a-d);
Figure imgf000016_0001
v. treating amine compounds (21a-d) as obtained in step (iv) with substituted aldehydes in the presence of catalytic amount of acetic acid (2-3 drops) in 15 to 20 mL of ethanol solution under reflux conditions to obtain imine compounds followed by treatment with /?-toulenesulfonyl methy isocyanide to obtain nitro intermediates (25a-l) and compound of formula 4a-g to 7a-g and 8a-b to 15a-b; vi. reducing nitro intermediate as obtained in step (v) with SnCl2.2H20 in ethanol to obtain compound of formula 4h-j to 7h-j.
Figure imgf000016_0002
25 a-l
25a R3 = R4 = R6 =R7 = H; R5=N02 ;R= R2 =H; R-i = F
25b:R4 = R6 = R7 = H; R3 = N02;R5 = OCH3;R= R2 =H; R-i = F
25c:R3 = R6 = R7 = H; R4 =N02; R5 = OCH3 ;R= R2 =H; R-, = F
25d: R3 = R4 = R6 =R7 = H; R5=N02 ;R= R2 =H; R-i = OCH3
25e:R4 = R6 = R7 = H; R3 = N02;R5 = OCH3;R= R2 =H; R-i = OCH3
25f:R3 = R6 = R7 = H; R4 =N02; R5 = OCH3 ;R= R2 =H; R-i = OCH3
25g: R3 = R4 = R6 =R7 = H; R5=N02 ; R= R2 =OCH3; R1 = H
25h:R4 = R6 = R7 = H; R3 = N02;R5 = OCH3;R= R2 =OCH3; R-, = H3
25i:R3 = R6 = R7 = H; R4 =N02; R5 = OCH3 ;R= R2 =OCH3; R1 = H
25j R3 = R4 = R6 =R7 = H; R5=N02 ; R=R-, = R2 =OCH3;
25k:R4 = R6 = R7 = H; R3 = N02;R5 = OCH3;R= R-,= R2 =OCH3;
25I:R3 = R6 = R7 = H; R4 =N02; R5 = OCH3 ;R = R-,= R2 =OCH3;
vii. purifying compound of formula 4a-g to 7a-g and 8a-b to 15a-b as obtained in step (v) and 4h-j to 7h-j as obtained in step (vi) by column chromatography using solvent to obtain final compounds of general formula 1. In yet another embodiment of the present invention, substituted aldehydes used is selected from the group consisting of 22a-j, 23a-b and 24a-b.
Figure imgf000017_0001
-R5 - R6 -R7 - H;
23a: R8 = H;
R5 = Re = R5— CF3
R7 = H; R4 =OCH3 R5 = F 23b: R8 = OCH3
R7— H; R4— Rg— OCH3 24a: X = NH;
R7 = H; R4 = R5 = OCH3 24b: X = S
H; R4 R — Rg— OCH3
H; R3 R5— R7 OCH3
R6 =R7 = H; R5=N02
R7 = H; R3 = N02;R2 = OCH3
R7 = H; R4 =N02; R5 = OCH3
In yet another embodiment of the present invention, solvent used are selected from ethyl acetate, hexane, chloroform or methanol.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 represents FACS analysis of cell cycle distribution of MCF-7 cells after treatment with compounds CA-4, 21a, 2 Id, 4c, 6d, 6e, 6f, 7d, 7h and 7j at 2 μΜ concentration for 24h and control cells are the cells treated with DMSO (0.25%).
Figure 2 represents effect of compound 7d, the effective compound on the microtubule network of MCF-7 cells untreated cells (Con), nocodazole (Noc) and 7d at 2 μΜ concentration. Microtubules and unassembled tubulin are shown in green and DNA was was stained with nuclear dye DAPI( 4,6-diamidino-2-phenylindole) is shown in blue colour.
Figure 3 represents effect of compound 7d and 7h on p21 and caspase-9. MCF-7 cells were treated with 2 μΜ concentration of compounds 7d and 7h for 24h. The cell lysates were collected and probed with anti-bodies against p21 and caspase-9. beta-actin was used as loading control. Con: Control (untreated).
Scheme 1 represent schematic diagram for the preparation of compound of general formula A wherein reagent and conditions are (i) Pyridine, reflux, 2h; (ii) Lawessons reagent, toluene, reflux, 8h; (iii) K3[FeCN)6], Aq.NaOH, 2H; (IV) SnCl2.2H20, ethanol, reflux, 2h; (v)ethanol, AcOH (Cat), reflux; (vi)p-toluene sulfonyl methyl isocyanide, K2CO3, DME:MEOH (1 :2) reflux, 12h; (vii) SnCl2.2H20, ethanol, reflux, 2h.
DETAILED DESCRIPTION OF THE INVENTION
2-phenyl benzothiazole linked imidazole compounds have shown promising anticancer activity in various cell lines. The molecules synthesized are of immense biological significance with potential inhibition of tubulin polymerization. This resulted in design and synthesis of new congeners as illustrated in Scheme- 1, which comprise:
. Coupling reaction between substituted anilines and 4-nitro benzoyl chloride;
. Conversion of amide compound into corresponding thioamide using lawessons reagent in toluene at reflux conditions for 6 to 8h;
. Benzothiazole ring cyclization takes place in the presence of K3[Fe(CN)6] and in aqueous NaOH for 2 to 3h under reflux conditions;
. Reduction of nitro group of 4-nitro 2-phenyl benzothiazole by SnCl2.2H20 to form amine compounds;
. Reaction of amines with substituted aldehydes in the presence of catalytic amount of acetic acid in ethanol solution under reflux conditions afforded imine formation with on reaction with /?-toulenesulfonyl methyl isocyanide (Tosmic) and base K2C03 using solvents DME:MeOH (1 :4) under reflux condtions for 12 h yielded the corresponding 2- phenyl benzothiazole linked imidazole compounds and also some nitro intermediates which obtained by the reaction of nitro substituted aldehydes under above conditions further on reduction with with SnCl2.2H20 to obtain final compounds containing amine functionality which exhibiting promising anticancer activity in various cell lines;
. Purification by column chromatography using different solvents like ethyl acetate, hexane, chloroform and methanol.
EXAMPLES
Following examples are given by way of illustration therefore should not construed to limit the scope of the invention.
Example 1
6-fluoro-2-(4-(5-(4-fluoro-3-methoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (4c) To a stirred solution of 4-fluoro aniline (16a, 4g, 32.7 mmol) in pyridine as solvent and base to this 4-nitrobenzoyl chloride (17, 6.69 g, 36.0 mmol) is added slowly and reflux for 2h, after completion of the reaction, reaction mixture is poured in water, filter and washed with dil HC1 to afford compound N-(4-fluorophenyl)-4-nitrobenzamide (18a). To a stirred solution of amide (18a, 8g, 30. 7 mmol) taken in toluene lawessons reagent (2,4-bis(4- methoxyphenyl)-l,3,2,4-dithiadiphosphetane-2,4-disulfide) (10.18 g, 25.2 mmol) is added and refluxed at 110°C for 7h. After completion of the reaction toluene is evaporated under vaccum and water is added and extracted into chloroform finally purification by column chromatography to afford pure compound N-(4-fluorophenyl)-4-nitrobenzothioamide (19a). Treating the thioamide product (19a, 4g, 14.49 mmol) with potassium ferricyanide (4eq) in aqueous sodium hydroxide (8eq) solution at 90°C for 3h cyclization takes place to obtain the 6-fluoro-2-(4-nitrophenyl)benzo[<i]thiazole (20a) solid is precipitated from the reaction mixture filtered and washed with water to get 20a. Reduction of the nitro compound (20a, lg, 3.64 mmol) is proceeded with SnCl2.2H20 in ethanol and reflux at 80°C for 2h. After completion of reaction ethanol is evaporated under vaccum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered in celite bed and purified in silica column (60-120) to afforded pure compound (21a) The compound 4-(6-fluorobenzo[d]thiazol-2-yl)benzenamine (21a, 244 mg, lmmol) on reaction with 4-fluoro 3-methoxy benzaldehyde (22c, 152 mg, lmmol) in ethanol using catalytic amount of acetic acid and refluxed for 2h after completion reaction mixture is cooled to 0°C solid is precipitated from the reaction mixture it is filtered and washed with ethanol to gave the enamine product,and immediately proceeded for the next reaction with using (p-tolylsulfonyl) methyl isocyanide (tosmic) (1.5eq), and potassium carbonate (2eq) as base, in 10 mL of methanol and 5 mL of DME was heated under reflux for 12 h after completion of reaction as monitored by TLC. It was cooled to room temperature (27 °C); the solution was concentrated in vacuo and partitioned between EtOAc and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with EtOAc and Hexane to gave compound 4c as a light yellow solid (68%).
1H NMR (CDCls, 300 MHz): δ 8.11 (d, 2H, J = 8.3 Hz), 8.02 (q, 1H, J = 4.5 Hz), 7.76 (s, 1H), 7.58 (dd,lH, J = 6.0, 2.2 Hz), 7.29 (d, 2H, J = 8.3 Hz), 7.25 (m, 2H), 6.98 (q, 1H, J = 8.3, 3.0 Hz), 6.73 (dd, 1H, J = 2.2 Hz, 6.0 Hz), 6.68 (m, 1H), 3.70 (s, 3H), ESI-MS: m/z 420 [M+l]+.
Example 2 2-(4-(5-(3,5-dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i] thiazole (6d)
To a stirred solution of 3,5-dimethoxybenzenamine (16c, 4g, 26.1 mmol) in pyridine as solvent and base to this 4-nitrobenzoyl chloride (17, 5.3 g, 28.7 mmol) is added slowly and reflux for 2h, after completion of the reaction, reaction mixture is poured in water, filtered, washed with dil HC1 and dried to afford compound N-(3,5-dimethoxyphenyl)-4- nitrobenzamide (18c). To a stirred solution of amide (18c, 5g, 16.5 mmol) taken in toluene to this la wessons reagent (4.6 g, 11.5 mmol) is added and re fluxed at 110°C for 8h. After completion of the reaction toluene is evaporated under vaccum and water is added and extracted into chloroform and finally purified by column chromatography to afford pure compound N-(3,5-dimethoxyphenyl)-4-nitrobenzothioamide (19c). Treating the thioamide product (19c, 3g, 9.4mmol) with potassium ferricyanide(4 eq) in aqueous sodium hydroxide(8 eq) solution at 90°C for 2h cyclization takes place to obtain the 5,7- dimethoxy-2-(4-nitrophenyl)benzo[(i]thiazole (20c) solid is precipitated from the reaction mixture filtered and washed with water and and dried to afforded product 20c. Reduction of the nitro compound (20c, 500mg, 1.5mmol) is proceeded with SnCl2.2H20 in ethanol and reflux at 80°C for 2h, after completion of reaction ethanol is evaporated under vaccum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered in celite bed and purified in silica column (60-120) to afforded pure compound (21c). The compound 4-(5,7-dimethoxybenzo[<i]thiazol-2-yl)benzenamine (21c, 200 mg, 0.698mmol) on reaction with 3,5-dimethoxybenzaldehyde (22d, 116 mg, 0.698mmol) in ethanol using catalytic amount of acetic acid and ref uxed for 2h after completion reaction mixture is cooled to 0 °C solid is precipitated from the reaction mixture it is filtered and washed with ethanol to gave the enamine product, and immediately proceeded for the next reaction by using (p-tolylsulfonyl) methyl isocyanide (tosmic) (1.5eq), and potassium carbonate (2eq) as base, in 10 mL of methanol and 5 mL of DME was heated under reflux for 12 h after completion of reaction as monitored by TLC. It was cooled to room temperature (27°C); the solution was concentrated in vacuo and partitioned between EtOAc and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with EtOAc and Hexane to gave compound 6d as a brown solid (63%). 1H NMR (CDCI3, 500 MHz): δ 8.10 (d, 2H J = 8.2 Hz), 7.75 (d, 1H ) 7.30 (d, 2H, J = 8.2), 7.29 (s, 1H), 7.17 (d, 1H, J = 1.8 Hz), 6.51 (s, 1H), 6.37 (t, 1H), 6.30 (s, 2H ) 3.95 (s, 3H), 3.89 (s, 3H), 3.64 (s, 6H); ESI-MS: m/z 474 [M+l]+.
Example 3
2-(4-(5-(3,4-dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i] thiazole (6e)
To a stirred solution of 3,5-dimethoxybenzenamine (16c, 4g, 26.1 mmol) in pyridine as solvent and base to this 4-nitrobenzoyl chloride (17, 5.3g, 28.7 mmol) is added slowly and reflux for 2h, after completion of the reaction, reaction mixture is poured in water, filter and washed with dil HC1 and dried to afford compound N-(3,5-dimethoxyphenyl)-4- nitrobenzamide (18c). To a stirred solution of amide (18c, 5g, 16.5 mmol) taken in toluene add lawessons reagent (4.6 g, 11.5 mmol) and refluxed at 110°C for 6h. After completion of the reaction toluene is evaporated under vaccum and water is added and extracted into chloroform and finally purified by column chromatography to afford pure compound N- (3,5-dimethoxyphenyl)-4-nitrobenzothioamide (19c). Treating the thioamide product (19c, 3g, 9.4mmol) with potassium ferricyanide (4eq) in aqueous sodium hydroxide(8eq) solution at 90°C for 2h cyclization takes place to obtain the 5,7-dimethoxy-2-(4- nitrophenyl)benzo[(i]thiazole (20c) solid is precipitated from the reaction mixture filtered and washed with water and dried to afforded product 20c. Reduction of the nitro compound (20c, 500 mg, 1.5mmol) is proceeded with SnCl2.2H20 in ethanol and reflux at 80°C for 2h, after completion of reaction ethanol is evaporated under vaccum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered in celite bed and purified in silica column (60-120) to afforded pure compound (21c). The compound 4-(5,7-dimethoxybenzo[<i]thiazol-2-yl)benzenamine (21c, 200 mg, 0.698mmol) on reaction with 3,4-dimethoxybenzaldehyde (22e, 116 mg, 0.698mmol) in ethanol using catalytic amount of acetic acid and refluxed for 2h after completion reaction mixture is cooled to 0 °C solid is precipitated from the reaction mixture it is filtered and washed with ethanol to gave the enamine product,and immediately proceeded for the next reaction by using (p-tolylsulfonyl) methyl isocyanide (tosmic) (1.5 eq), and potassium carbonate (2 eq) as base, in 10 mL of methanol and 5 mL of DME was heated under reflux for 12 h after completion of reaction as monitored by TLC. It was cooled to room temperature (27 °C); the solution was concentrated in vacuo and partitioned between EtOAc and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with EtOAc and Hexane to gave compound 6e as a light yellow solid (69%).
1H NMR (CDCl3,500MHz): δ 8.09 (d, 2H J= 8.7 Hz), 7.73 (s, 1H), 7.29 (d, 2H, J = 8.7 Hz), 7.22 (s, 1H), 7.16 (s, 1H), 6.76 (d, 1H, J= 8.7 Hz), 6.72 (dd, 1H, J= 6.8, 1.9 Hz), 6.65 (d,lH, J = 1.9 Hz), 6.50 (s, 1H), 3.97 (s, 3H), 3.90 (s, 3H), 3.86 (s, 3H), 3.67 (s, 3H), ESI-MS: m/z 474 [M+l]+.
Example 4
5 ,7-dimethoxy-2-(4-(5 -(3 ,4,5 -trimethoxyphenyl)- 1 H-imidazo 1- 1 -yl)phenyl)benzo [d] thiazo le (6f)
To a stirred solution of 3,5-dimethoxybenzenamine (16c, 4g, 26.1 mmol) in pyridine as solvent and base to this 4-nitrobenzoyl chloride (17, 5.3 g, 28.7 mmol) is added slowly and reflux for 2h, after completion of the reaction, reaction mixture is poured in water, filter and washed with dil HC1 and dried to afford compound N-(3,5-dimethoxyphenyl)-4- nitrobenzamide (18c). To a stirred solution of amide (18c, 5g, 16.5 mmol) taken in toluene add lawessons reagent (4.6 g, 11.5 mmol) and refluxed at 110°C for 7h. After completion of the reaction toluene is evaporated under vaccum and water is added and extracted into chloroform and finally purified by column chromatography to afford pure compound N-(3,5- dimethoxyphenyl)-4-nitrobenzothioamide (19c). Treating the thioamide product (19c, 3g, 9.4mmol) with potassium ferricyanide (4 eq) in aqueous sodium hydroxide (8 eq) solution at 90°C for 2h cyclization takes place to obtain the 5,7-dimethoxy-2-(4- nitrophenyl)benzo[(i]thiazole (20c) solid is precipitated from the reaction mixture filtered and washed with water and dried to afforded product 20c. Reduction of the nitro compound (20c, 500 mg, 1.5mmol) is proceeded with SnCl2.2H20 in ethanol and reflux at 80°C for 2h, after completion of reaction ethanol is evaporated under vaccum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered in celite bed and purified in silica column (60-120) to afforded pure compound (21c). The compound 4- (5,7-dimethoxybenzo[d]thiazol-2-yl)benzenamine (21c, 200 mg, 0.698mmol) on reaction with 3,4,5-trimethoxybenzaldehyde (22f, 137 mg, leq) in ethanol using catalytic amount of acetic acid and refluxed for 2h after completion reaction mixture is cooled to 0 °C solid is precipitated from the reaction mixture it is filtered and washed with ethanol to gave the enamine product and immediately proceeded for the next reaction by using (p-tolylsulfonyl) methyl isocyanide (tosmic) (1.5 eq), and potassium carbonate (2 eq) as base, in 10 mL of methanol and 5 mL of DME was heated under reflux for 12 h after completion of reaction as monitored by TLC. It was cooled to room temperature (27 °C); the solution was concentrated in vacuo and partitioned between EtOAc and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with EtOAc and Hexane to gave compound 6f as a yellow solid (53%).
1H NMR (CDCl3,500MHz): δ 8.12 (d, 2H, J= 8.3 Hz), 7.69 (s, 1H), 7.32 (d, 2H, J= 8.3 Hz), 7.20 (s, 1H), 7.11 (d,lH, J = 2.0 Hz), 6.46 (s, 1H), 6.31 (s, 2H), 3.97 (s, 3H), 3.89 (s, 3H), 3.80 (s, 3H), 3.64 (s, 6H), ESI-MS: m/z 504 [M+l]+.
Example 5
2-(4-(5-(3,5-dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,6,7-trimethoxybenzo[(i] thiazole (7d)
To a stirred solution of 3,4,5-trimethoxybenzenamine (16d, 5g, 27.2mmol) in pyridine as solvent and base to this 4-nitrobenzoyl chloride (17, 5.5g, 29.9mmol) is added slowly and reflux for 3h, after completion of the reaction, reaction mixture is poured in water,filter and washed with dil HC1 and dried to afford compound 4-nitro-N-(3,4,5- trimethoxyphenyl)benzamide (18d). To a stirred solution of amide (18d, 6g, 18.0mmol) taken in toluene lawessons reagent (5.1g, 12.6mmol) is added and refluxed at 110°C for 6h. after completion of the reaction toluene is evaporated under vaccum and water is added and extracted into chloroform and finally purified by column chromatography to afford pure compound 4-nitro-N-(3,4,5-trimethoxyphenyl) benzothioamide (19d). Treating the thioamide product (19d, 4g, 11.4mmol) with potassium ferricyanide (4eq) in aqueous sodium hydroxide(8eq) solution at 90°C for 2h cyclization takes place to obtain the 5,6,7-trimethoxy- 2-(4-nitrophenyl) benzo[<i]thiazole (20d) solid is precipitated from the reaction mixture filtered and washed with water and dried to afforded product 20d. Reduction of the nitro compound (20d, lg, 2.8mmol) is proceeded with SnCl2.2H20 in ethanol and reflux at 80°C for 2h, after completion of reaction ethanol is evaporated under vaccum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered in celite bed and purified in silica column (60-120) to afforded pure compound (2 Id). The compound 4-(5,6,7-trimethoxybenzo[<i]thiazol-2-yl)benzenamine (21d, 250mg, 0.79 mmol) on reaction with 3,5-dimethoxybenzaldehyde (22d, 131mg, 0.79 mmol) in ethanol using catalytic amount of acetic acid and refluxed for 2h after completion reaction mixture is cooled to 0 °C solid is precipitated from the reaction mixture it is filtered and washed with ethanol to gave the enamine product,and immediately proceeded for the next reaction with using (p-tolylsulfonyl) methyl isocyanide (tosmic) (1.5eq), and potassium carbonate (2eq) as base, in 10 mL of methanol and 5 mL of DME was heated under reflux for 12 h after completion of reaction as monitored by TLC. It was cooled to room temperature (27 °C); the solution was concentrated in vacuo and partitioned between EtOAc and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with EtOAc and Hexane to gave compound 7d as a brown solid (62%).
1H NMR (CDCls, 400 MHz): δ 8.05 (d, 2H, J = 7.6 Hz), 7.71 (s, 1H), 7.29 (d, 2H, J = 7.6 Hz), 7.27 (brs, 2H), 6.29 (s, 1H), 6.24 (d, 2H, J= 1.5 Hz), 4.08 (s, 3H), 3.95 (s, 3H), 3.91 (s, 3H), 3.62 (s, 6H); ESI-MS: m/z 504 [M+l]+.
Example 6
4-(l-(4-(5,6,7-trimethoxybenzo[(i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (7h) To a stirred solution of 3,4,5-trimethoxybenzenamine (16d, 5g, 27.2 mmol) in pyridine as solvent and base to this 4-nitrobenzoyl chloride (17, 5.5g, 29.9 mmol) is added slowly and reflux for 3h, after completion of the reaction, reaction mixture is poured in water, filter and washed with dil HC1 and dried to afford compound 4-nitro-N-(3,4,5- trimethoxyphenyl)benzamide (18d). To a stirred solution of amide (18d, 6g, 18.0 mmol) taken in toluene lawessons reagent (5.1g, 12.6 mmol) is added and refluxed at 110°C for 8h. After completion of the reaction toluene is evaporated under vaccum and water is added and extracted into chloroform and finally purified by column chromatography to afford pure compound 4-nitro-N-(3,4,5-trimethoxyphenyl)benzothioamide (19d,). Treating the thioamide product (19d, 4g, 11.4 mmol) with potassium ferricyanide (4eq) in aqueous sodium hydroxide (8eq) solution at 90°C for 2h cyclization takes place to obtain the 5,6,7- trimethoxy-2-(4-nitrophenyl)benzo[(i]thiazole (20d) solid is precipitated from the reaction mixture filtered and washed with water and dried to afforded product 20d. Reduction of the nitro compound (20d, lg, 2.8mmol) is proceeded with SnCl2.2H20 in ethanol and reflux at 80°C for 2h, after completion of reaction ethanol is evaporated under vaccum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered in celite bed and purified in silica column (60-120) to afforded pure compound (21d). The compound 4-(5,6,7-trimethoxybenzo[d]thiazol-2-yl) benzenamine (21d, 250 mg, 0.79mmol) on reaction with 4-nitrobenzaldehyde (22h, 119 mg, leq) in ethanol using catalytic amount of acetic acid and refluxed for 2h after completion reaction mixture is cooled to 0 °C solid is precipitated from the reaction mixture it is filtered and washed with ethanol to gave the enamine product, and immediately proceeded for the next reaction with using (p-tolylsulfonyl) methyl isocyanide (tosmic) (1.5 eq), and potassium carbonate (2 eq) as base, in 10 mL of methanol and 5 mL of DME was heated under reflux for 12 h after completion of reaction as monitored by TLC. It was cooled to room temperature(27°C); the solution was concentrated in vacuo and partitioned between EtOAc and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with EtOAc and Hexane to gave compound 5,6,7-trimethoxy-2-(4-(5-(4-nitrophenyl)-lH- imidazol-l-yl)phenyl)benzo[(i]thiazole (25j) as a yellow solid. Reduction of (25j, 150 mg) with SnCl2.2H20 in ethanol reflux for 2h, after which ethanol is evaporated and quench with bicarbonate solution and extracted into ethylacetate and finally purified by column chromatography using EtOAc and Hexane to gave compound 7h as pure compound (66%). 1H NMR (CDC13,400 MHz,): δ 8.05 (d, 2H J = 8.3 Hz,), 7.70 (s, 1H), 7.32 (s, 1H), 7.27 (d, 2H J = 8.3 Hz), 7.15 (s,lH), 6.94 (d, 2H, J = 8.3 Hz), 6.56 (d, 2H, J = 8.3 Hz ), 4.10 (s, 3H), 3.96 (s, 3H), 3.94 (s, 3H); ESI-MS: m/z 459 [M+l]+.
Example 7
2-methoxy-5-(l-(4-(5,6,7-trimethoxybenzo[(i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzene amine (7j)
To a stirred solution of 3,4,5-trimethoxybenzenamine (16d, 5g, 27.2 mmol) in pyridine as solvent and base 4-nitrobenzoyl chloride (17, 5.5g, 29.9 mmol) is added slowly and reflux for 2-3h, after completion of the reaction, reaction mixture is poured in water, filter and washed with dil HC1 and dried to afford compound 4-nitro-N-(3,4,5-trimethoxyphenyl)benzamide (18d). To a stirred solution of amide (18d, 6g, 18.0 mmol) taken in toluene lawessons reagent (5.1g, 12.6 mmol) is added and refluxed at 110°C for 6h. After completion of the reaction toluene is evaporated under vaccum and water is added and extracted into chloroform and finally purified by column chromatography to afford pure compound 4-nitro-N-(3,4,5- trimethoxyphenyl)benzothioamide (19d). Treating the thioamide product (19d, 4g, 11.4 mmol) with potassium ferricyanide(4eq) in aqueous sodium hydroxide(8eq) solution at 90°C for 2h cyclization takes place to obtain the 5,6,7-trimethoxy-2-(4- nitrophenyl)benzo[(i]thiazole (20d) solid is precipitated from the reaction mixture filtered and washed with water and dried to afforded product 20d. Reduction of the nitro compound (20d, lg, 2.8mmol) is proceeded with SnCl2.2H20 in ethanol and reflux at 80°C for 2h, after completion of reaction ethanol is evaporated under vaccum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered in celite bed and purified in silica column (60-120) to afforded pure compound (2 Id). The compound 4- (5,6,7-trimethoxybenzo[(i]thiazol-2-yl)benzenamine (21d, 250 mg, 0.79mmol) on reaction with 4-methoxy-3-nitrobenzaldehyde (22j, 143mg, 0.79mmol) in ethanol using catalytic amount of acetic acid and refluxed for 2h after completion reaction mixture is cooled to 0 °C solid is precipitated from the reaction mixture it is filtered and washed with ethanol to gave the enamine product,and immediately proceeded for the next reaction by using (p- tolylsulfonyl) methyl isocyanide (tosmic) (1.5eq), and potassium carbonate (2eq) as base, in 10 mL of methanol and 5 mL of DME was heated under reflux for 12 h after completion of reaction as monitored by TLC. It was cooled to room temperature (27°C); the solution was concentrated in vacuo and partitioned between EtOAc and water. The organic layer was separated, washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with EtOAc and Hexane to gave compound 5,6,7-trimethoxy-2-(4-(5-(4-methoxy-3-nitrophenyl)-lH- imidazol-l-yl) phenyl)benzo[<i]thiazole 251 as a yellow solid. Reduction of (251, 150mg) with SnCl2.2H20 in ethanol reflux for 2hr, after which ethanol is evaporated and quench with bicarbonate solution and extracted into ethylacetate and finally purified by column chromatography using EtOAc and Hexane to gave compound 7j as pure compound (63%). 1H NMR (CDC13300 MHz,): δ 8.03 (d, 2H J = 8.3 Hz), 7.75 (s, 1H), 7.32 (s, 1H), 7.27 (d, 2H, J= 8.3 Hz), 7.17 (s, 1H), 6.64 (d, 1H, J= 8.3), 6.55 (d, 1H, J= 2.2 Hz), 6.43 (dd, 1H, J = 8.3, 1.5 Hz), 4.10 (s, 3H), 3.96 (s, 3H), 3.94 (s, 3H) 3.83 (s, 3H), 3.51 (brs, 2H); ESI-MS: m/z 489 [M+l]+.
BIOLOGICAL ACTIVITY
Some of biological activity studies were carried out at the National Cancer Institute (NCI), Maryland, USA.
Anticancer Activity. The compounds were evaluated for anticancer activity against sixty human cancer cells derived from nine cancer types (leukemia cell line, non-small-cell lung cell line, colon cell line, CNS cell line, melanoma cell line, ovarian cell line, prostate cell line, renal cancer cell line and breast cancer cell line) as shown in Table 1. For each compound, dose response curves for each cell line were measured at a minimum of five concentrations at 10 fold dilutions. A protocol of 48 h continuous drug exposure was used and a sulforho damine B (SRB) protein assay was used to estimate cell viability or growth.
Table 1 : The GI50 (μΜ) values for compounds 3a, 3b 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines.
Cancer panel/cell line GI50 (μΜ)
3a 3b 4c 6(1 6e 6f 7d 7h 7j
Leukemia
CCRF-CEM 6.45 0.79 6.92 - a
3.95 - - 3.41
HL-60(TB) 8.71 - 2.50 - 3.09 3.30 2.43 0.989 2.20
K-562 6.02 36.31 3.93 3.22 5.88 3.83 3.57 - 3.38
MOLT-4 19.50 26.91 3.41 - - 4.24 4.11 - 4.00
SR 17.37 21.88 4.99 3.30 3.03 3.24 7.14 1.40 3.43
RPMI-8226 - - 4.11 - a
5.39 2.90 - -
Non-small lung
A549/ATCC 28.84 34.67 12.3 - 41.8 6.16 5.59 3.14 5.77
EKVX 34.67 4.07 - - - 5.09 1.87 2.49 7.54
HOP-62 a
30.91 40.7 6.65 35.5 75.9 26.4 - -
HOP-92 - a
5.47 - - - a
0.446 -
NCI-H226 0.35 60.27 49.3 18.5 6.44 - 21.7 4.73 6.70
a
NCI-H23 58.89 12.58 8.25 10.3 6.15 9.56 3.87 4.76
NCI-H322M 43.66 39.82 a a a
36.3 86.5 2.07 25.7
NCI-H460 53.70 38.91 5.70 4.41 6.06 4.67 7.46 5.13 4.69
NCI-H522 32.36 30.20 9.90 2.49 5.26 3.27 11.8 2.74 3.37
Colon
a
COLO 205 51.30 56.8 - - 4.51 3.85 - 2.94
a a a a a a
HCC-2998 0.25 - -
HCT-116 43.66 43.66 4.36 4.93 5.48 3.92 3.76 3.81 3.78
a a
HCT-15 47.86 82.3 - 5.48 5.72 - 4.02
HT29 29.51 37.16 10.8 - 7.13 4.88 8.33 2.79 3.87
KM12 a
57.57 6.40 4.52 6.80 4.62 5.54 - 3.80 a
SW-620 66.09 7.81 - a
5.96 13.7 - 6.21
CNS
a
SF-268 35.48 12.7 11.3 9.96 - 22.1 12.3 47.0
SF-295 64.59 31.62 75.9 2.40 7.00 4.42 3.64 1.53 4.44
a - a a
SF-539 5.76 8.59 22.0 7.14 a a a a
SNB-19 45.72 a a
20.6 19.7 12.3
SNB-75 33.12 15.85 12.6 3.28 7.21 6.47 15.0 5.94 52.3
U251 66.09 31.62 4.76 9.19 4.15 5.44 3.84 6.00 Ovarian
IGROV1 0.042 47.86 15.4 5.07 56.1 5.87 9.60 2.63 4.90
OVCAR-3 - 38.91 5.71 2.87 3.85 3.26 6.07 2.73 5.18
OVCAR-4 0.54 37.16 11.4 - 4.21 3.25 6.67 3.60 6.29
- a a a a a a
OVCAR-5 83.19 34.3
a a
OVCAR-8 15.2 14.5 21.2 a 13.4 4.23 6.19
NCI/ADR-RES - a
30.6 2.58 5.65 11.0 1.61 3.12 a a a a a
SK-OV-3 37.16 4.69 49.9 11.7
Renal
a a
786-0 29.51 36.1 7.60 7.38 10.3 6.26 5.73
A498 42.66 41.70 0.0432 a
3.15 2.15 1.83 2.13 4.83 a a
ACHN 51.30 53.70 29.1 6.67 11.5 8.56 5.59
CAKI-1 - 34.67 -a 2.13 - - 3.79 1.41 4.82
50.12 a a a
SN12C 38.91 31.9 31.9 8.95 9.44
a
TK-10 0.18 77.63 38.8 16.8 9.40 26.4 4.93 4.16
UO-31 6.45 21.38 16.5 - 31.7 2.27 1.94 1.55 1.99
RXF 393 70.57 30.20 13.5 6.58 - 2.80 30.2 4.41 5.98
Prostate
PC-3 31.62 50.12 3.47 - 3.66 2.54 3.17 3.02 2.59
a
DU-145 61.69 33.88 14.3 27.9 31.1 7.25 6.38
Breast
MCF7 0.03 56.24 23.5 3.82 5.36 3.88 4.02 3.02 4.07
MDA-MB- 66.09 44.68 32.2 9.01 28.4 3.51 19.2 a
3.65 a
231/ATCC 95.51 -a 5.02 - - 20.9 5.36 28.3
HS 578T 66.09 14.12 11.5 3.09 9.12 5.23 6.71 - 6.21
BT-549 0.10 22.39 7.98 5.77 3.78 3.35 4.74 1.59 3.02
T-47D 11.1 3.17 4.15 3.27 10.7 1.82 8.60
MDA-MB-468
Melanoma
a a
LOX IMVI 37.16 35.9 5.48 5.40 6.93 3.65 4.75
MALME-3M a
83.19 11.1 - 59.8 3.73 9.58 0.710 2.48
M14 57.57 33.12 33.4 - a
7.91 - 2.10 5.91
MDA-MB-435 79.49 89.12 17.1 1.53 - 3.41 6.07 - 3.13
SK-MEL-2 a a
39.7 9.69 41.4 6.09 6.16 - 6.04 a a a - a
SK-MEL-28 64.59 35.1 31.6 13.7
SK-MEL-5 21.88 52.49 12.1 3.29 3.61 2.46 2.85 2.74 1.73
a a a a a
UACC-257 74.18 4.11 20.5 6.40
UACC-62 70.82 57.57 8.67 4.75 8.14 4.14 a
13.8 5.45
- not done on that cell line; -a not active
Table 2: The mean graph midpoint values (MG MID) of Logio GI50 (log values of concentration in mol/L causing 50% inhibition of net cell growth) values for compounds 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines. Cancer cell lines Logio GI 7d 7h 7j
4c 6(1 6e 6f
50
Leukemia -5.38 -5.48 -4.79 -5.41 -5.43 -5.92 -5.49
Non-small cell lung -4.83 -4.98 -4.64 -4.95 -4.82 -5.59 -5.18
Colon -4.71 -4.88 -4.60 -5.13 -5.04 -5.48 -5.40
CNS -4.52 -5.10 -4.72 -4.80 -4.92 -5.24 -4.53
Melanoma -4.82 -4.98 -4.39 -5.18 -5.03 -5.32 -5.17
Ovarian -4.62 -5.10 -4.53 -4.78 -4.79 -5.30 -4.93
Renal -4.98 -4.89 -4.60 -5.18 -4.83 -5.41 -5.31
Prostate -5.16 >-4.0 -4.99 -4.79 -5.00 -5.33 -5.39
Breast -4.82 -5.34 -5.13 -5.42 -5.04 -5.55 -4.96
Table 3: The mean graph midpoint values (MG MID) of Logio LC50 values (log value of the concentration of compounds leading to 50% net cell death) for compounds 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines.
Figure imgf000029_0001
Table 4: The mean graph midpoint values (MG MID) of logioTGI (log value of concentration of the compound resulting in total inhibition of net cell growth) for compounds 4c, 6d, 6e, 6f, 7d, 7h and 7j in sixty cancer cell lines.
Cancer cell lines Logio TGI 4c 6(1 6e 6f 7d 7h 7j
Leukemia -4.19 >-4.0 >-4.0 >-4.0 >-4.0 >-4.0 -4.20 Non-small cell lung 4.41 -4.05 -4.01 >-4.0 >-4.0 -4.54 -4.11
Colon -4.06 >-4.0 >-4.0 >-4.0 >-4.0 >-4.0 -4.11
CNS -4.05 -4.19 -4.06 >-4.0 -4.11 -4.51 >-4.0
Melanoma >-4.0 >-4.0 >-4.0 >-4.0 -4.02 -4.13 -4.26
Ovarian -4.11 >-4.0 >-4.0 >-4.0 -4.08 -4.56 >-4.0
Renal -4.11 >-4.0 >-4.0 >-4.0 -4.03 -4.38 -4.14
Prostate -4.06 >-4.0 >-4.0 >-4.0 >-4.0 -4.15 >-4.0
Breast -4.02 >-4.0 >-4.0 >-4.0 >-4.0 -4.47 >-4.0
Table 5: Comparative data of present compounds (7h, 7j, 7d and 4c) with previous compounds (3c and 3d; US patent no. 7384966)
Figure imgf000030_0001
A498 -5.01 - -5.67 -5.32 >-4.0 -7.36
ACHN -5.17 >-4.0 -5.07 -5.25 -4.94 -4.54
CAKI-1 -4.63 >-4.0 -5.85 -5.32 -5.42 -
SN12C >-4.0 >-4.0 -5.05 -5.03 -4.50 -4.50
UO-31 >-4.0 >-4.0 -5.81 -5.70 -5.71 -4.78
RXF 393 - - -5.36 -5.22 -4.52 -4.87
Prostate
PC-3 >-4.0 >-4.0 -5.52 -5.59 -5.50 -5.46
DU-145 -4.06 >-4.0 -5.04 -5.20 -4.51 -4.85
Breast
MDA-MB- -4.26 >-4.0 -5.44 >-4.0 -4.72 -4.49
231/ATCC
HS 578T - >-4.0 -5.27 -4.55 -4.68 -
BT-549 -4.77 >-4.0 - -5.21 -5.17 -4.94
MDA-MB-468 - - -5.74 -5.07 -4.97 -4.96
Melanoma
LOX IMVI -4.19 >-4.0 -5.44 -5.32 -5.16 -4.44
MALME-3M >-4.0 >-4.0 -6.15 -5.61 -5.02 -4.95
M14 >-4.0 >-4.0 -5.68 -5.23 - -4.48
MDA-MB-435 - - - -5.50 -5.22 -4.77
SK-MEL-2 - - - -5.22 -5.21 -4.40
SK-MEL-28 - - >-4.0 -4.86 -4.50 -4.45
UACC-257 >-4.0 >-4.0 -5.19 >-4.0 -4.69 -5.39
UACC-62 -4.37 >-4.0 -5.26 -5.04 -4.86 -5.06
Effect of compounds on cell cycle distribution.
In order to investigate the mechanism underlying the anti-pro liferative effect of the compounds the cell cycle distribution was analyzed in K562 (Leukemia) and MCF-7 (Breast carcinoma) cell lines by flow cytometry. Compounds CA-4,21a, 2 Id, 4c, 6d, 6e, 6f, 7d, 7h and 7j have shown 1.72%, 14%, 12%, 14%, 12%, 14%, 14%, 16%, 16% &12% in K562 cells and 49.63%, 21%, 20%, 18%, 21%, 21%, 21%,24%, 23% and 23% in MCF-7 cell line respectively. Compound 7d treated cells showed highest G2/M phase with 16 and 24% of cells in K562 and MCF-7 cells. Thus compound 7d was considered for further studies (Figure 1).
Effect of compound 7d on the inhibition of tubulin polymerization activity
Inhibition of tubulin is associated with G2/M cell cycle arrest by interrupting chromosome segregation and affecting mitotic spindle formation. Since 7d is the most effective compound in causing G2/M cell cycle arrest in both the cell lines tested. It was considered of interest to understand the mechanism of anti-cancer activity of compound 7d with regard to interaction with microtubule system. MCF-7 breast cancer cells were treated with Nocodazole (Noc), 7d compounds at 2 μΜ concentration. We observed disrupted microtubulin organization in Nocadazole and 7d compound treated cells (Figure 2).
Effect of compounds on apoptosis.
Activation of tumor suppressor gene p21 was the important regulator of apoptotic pathway caused by various stimuli. In many instances the apoptotic cell death is mediated by caspases, thus the possible involvement of p21 and caspase protein and its role in apoptosis has been investigated. MCF-7 cells were treated with 7d, 7h (the effective compounds of cell cycle arrest) 21a, 21d and CA-4 at 2 μΜ concentration. Western blot analysis revealed that treatment of MCF-7 cells with compounds caused increase in p21 and caspase-9 protein (Figure 3).
ADVANTAGES OF THE PRESENT INVENTION
1. The present invention provides 2-phenyl benzothiazole linked imidazole compounds of general formula A.
2. It also provides a process for the preparation of 2-phenyl benzothiazole linked imidazole compounds of general formula A.

Claims

Claims:
1. A compound of general formula A
Figure imgf000033_0001
General formula A wherein
Figure imgf000033_0002
R=H or OCH3;
Ri=H, F or OCH3;
R2=H or OCH3;
R3=H, NH2, F or OCH3;
R4=H , NH2 or OCH3;
R5=H, NH2, F, CF3 or OCH3;
Rs=H or OCH3;
R7=H or OCH3;
R8=H or OCH3.
2. Compound of general formula A as claimed in claim 1, wherein representative compounds are:
6-Fluoro-2-(4-(5-phenyl- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (4a);
6-Fluoro-2-(4-(5-(4-(trifluoromethyl)phenyl)-lH-imidazol-lyl)phenyl)benzo[(i]thiazole
(4b);
6-Fluoro-2-(4-(5-(4-fluoro-3-methoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i] thiazo le (4c);
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-fluorobenzo[(i]thiazole (4d); 2-(4-(5-(3,4-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-fluorobenzo[(i]thiazole (4e); 6-Fluoro-2-(4-(5-(3,4,5-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole 6-Fluoro-2-(4-(5-(2,4,6-trimethoxyphenyl)-lH-m
(4g);
4- (l-(4-(6-Fluorobenzo[<i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (4h); 2-( 1 -(4-(6-Fluorobenzo [djthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)-5 -methoxybenzene amine (4i)
5 - ( 1 -(4-(6-Fluorobenzo [djthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)-2-methoxy benzenamine (4j);
6- Methoxy-2-(4-(5 -phenyl- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (5a);
6-Methoxy-2-(4-(5-(4-(trifluoromethyl)phenyl)- IH-imidazol- 1 - yl)phenyl)benzo[<i]thiazole (5b);
2-(4-(5-(4-Fluoro-3-methoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i] thiazole (5c);
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i]thiazole (5d);
2-(4-(5-(3,4-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i]thiazole (5e) ;
6-Methoxy-2-(4-(5-(3,4,5-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole
(50;
6-Methoxy-2-(4-(5-(2,4,6-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole
(5g);
4- (l-(4-(6-Methoxybenzo[<i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (5h)
5 - Methoxy-2-( 1 -(4-(6-methoxybenzo [ Jthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)benzene amine (5i);
2-Methoxy-5 -( 1 -(4-(6-methoxybenzo [ Jthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)benzene amine (5j);
5,7-Dimethoxy-2-(4-(5-phenyl-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (6a);
5,7-Dimethoxy-2-(4-(5-(4-(trifluoromethyl)phenyl)-lH-imidazol-l-yl)phenyl)benzo[(i] thiazole (6b);
2-(4-(5-(4-Fluoro-3-methoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i] thiazole (6c)
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i] thiazole (6d);
2-(4-(5-(3,4-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i] thiazole (6e); 5,7-Dimethoxy-2-(4-(5-(3,4,5-trimeth^
thiazole (6f);
5,7-Dimethoxy-2-(4-(5-(2,4,6-trimethoxyphenyl)- lH-imidazol-l-yl)phenyl)benzo[ ^ thiazole (6g);
4- (l-(4-(5,7-Dimethoxybenzo[ ]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (6h);
2-( 1 -(4-(5 ,7-Dimethoxybenzo [ Jthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)-5 -methoxy benzenamine (6i);
5 - ( 1 -(4-(5 ,7-Dimethoxybenzo [ djthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)-2-methoxy benzenamine (6j);
5,6,7-Trimethoxy-2-(4-(5-phenyl-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (7a);
5,6,7-Trimethoxy-2-(4-(5-(4-(trifluoromet^
thiazole (7b);
2-(4-(5-(4-Fluoro-3-methoxyphenyl)-lH-imidazol- l-yl)phenyl)-5,6,7-trimethoxybenzo [ Jthiazole (7c);
2-(4-(5-(3,5-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,6,7-trimethoxybenzo[(i] thiazole (7d);
2-(4-(5-(3,4-Dimethoxyphenyl)-lH-imidazol-l-yl)phenyl)-5,6,7-trimethoxybenzo[(i] thiazole (7e);
5,6,7-Trimethoxy-2-(4-(5-(3,4,5-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i] thiazole (If);
5,6,7-Trimethoxy-2-(4-(5-(2,4,6-trimethoxyphenyl)-lH-imidazol-l-yl)phenyl)benzo[(i] thiazole (7g);
4-(l-(4-(5,6,7-Trimethoxybenzo[d]thiazol-2-yl)phenyl)-lH-imidazol-5-yl)benzenamine (7h);
2-( 1 -(4-(5 ,7-Dimethoxybenzo [ Jthiazo l-2-yl)phenyl)- lH-imidazo 1-5 -yl)-5 -methoxy benzenamine (7i);
2-Methoxy-5-(l-(4-(5,6,7-trimethoxybenzo[(i]thiazol-2-yl)phenyl)-lH-imidazol-5-yl) benzeneamine (7j);
2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-6-fluorobenzo[ ]thiazole (8a);
6- Fluoro-2-(4-(5-(5-methoxy- lH-indol-3-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (8b);
2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-6-methoxybenzo[(i]thiazole (9a); 6-Methoxy-2-(4-(5-(5-methoxy- lH-indol-3-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i] thiazole (9b);
2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-5,7-dimethoxybenzo[(i]thiazole (10a); 5,7-Dimethoxy-2-(4-(5-(5-methoxy- lH-indol-3-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i] thiazole (10b);
2-(4-(5-(lH-Indol-3-yl)-lH-imidazol-l-yl)phenyl)-5,6,7-trimethoxybenzo[(i]thiazole (11a);
5 ,6,7-Trimethoxy-2-(4-(5 -(5 -methoxy- 1 H-indo 1-3 -yl)- IH-imidazo 1- 1 -yl)phenyl)benzo [d] thiazole (lib);
6-Fluoro-2-(4-(5-(5-nitro- lH-pyrrol-2-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (12a);
6-Fluoro-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (12b); 6-Methoxy-2-(4-(5-(5-nitro- lH-pyrrol-2-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i]thiazole (13a);
6-Methoxy-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (13b);
5,7-Dimethoxy-2-(4-(5-(5-nitro- lH-pyrrol-2-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i] thiazole (14a);
5,7-Dimethoxy-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i]thiazole (14b);
5,6,7-Trimethoxy-2-(4-(5-(5-nitro- lH-pyrrol-2-yl)- IH-imidazol- 1 -yl)phenyl)benzo[<i] thiazole (15a);
5,6,7-Trimethoxy-2-(4-(5-(5-nitrothiophen-2-yl)-lH-imidazol-l-yl)phenyl)benzo[(i Jthiazole (15b).
Compound of general formula A as claimed in claim 1, wherein the structural formulae the representative compounds are: 36
Figure imgf000037_0001
Figure imgf000038_0001
Figure imgf000039_0001
Figure imgf000039_0002
Compound of general formula 1 as claimed in claim 1, wherein said compounds are useful as anti cancer agent.
5. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against sixty human cancer cell lines, derived from nine cancer cell types leukemia cell line, non small cell lung cell line, colon cell line, CNS cell line, renal cell line, prostate cell line, ovarian cell line, breast and melanoma cell line.
6. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against six leukemia cancer cell lines (CCRF-CEM, HL-60, K-562, MOLT-4, SR and RPMI-8226) for GI50 are in the range of 2.50 to 6.92, 3.22 to 3.30, 3.03 to 5.88, 3.24 to 5.39, 2.43 to 7.14, 0.989 to 1.40, and 2.20 to 4.00 μΜ respectively at an exposure period of at least 48 h.
7. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against nine Non-small cell lung cancer cell line (A549/ATCC, EKVX, HOP-62, HOP-92, NCI-H226, NCI-H23, NCI- H322M, NCI-H460 and NCI-H522) for GI50 are in the range of 5.47 to 49.3, 2.49 to 18.5, 5.26 to 41.8, 3.27 to 75.9, 1.87 to 86.5, 0.446 to 5.13, and 3.37 to 25.7 μΜ respectively at an exposure period of at least 48 h.
8. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against seven colon cancer cell line (COLO 205, HCC-2998, HCT-116, HCT-15, HT29, KM12 and SW-620) for GI50 are in the range of 4.36 to 82.3, 4.52 to 4.93, 5.48 to 7.13, 3.92 to 5.96, 3.76 to 13.7 , 2.79 to 3.81, and 2.94 to 6.21 μΜ respectively at an exposure period of at least 48 h.
9. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against six CNS cancer cell line (SF-268, SF-295, SF-539, SNB-19, SNB-75 and U251) for GI50 are in the range of 12.6 to 75.9, 2.40 to 11.3, 7.00 to 9.96, 4.15 to 8.59, 3.64 to 22.1, 1.53 to 12.3, and 4.44 to 52.3 μΜ respectively at an exposure period of at least 48 h.
10. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against eight renal cancer cell line (786-0, A498, ACHN, CAKI-1, SN12C, TK-10 UO-31 and RXF 393) for GI50 are in the range of 0.0432 to 38.8, 2.13 to 16.8, 2.15 to 3.17, 1.83 to 9.40, 1.94 to 31.9, 1.41 to 8.95, and 1.99 to 9.44 μΜ respectively at an exposure period of at least 48 h.
11. Compounds of formula 4c, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against two prostate cancer cell line (PC-3, DU-145) for GI50 are 3.47 to 14.3, 3.66 to 27.9, 2.54, 3.17 to 31.1, 3.02 to 7.25, and 2.59 to 6.38 μΜ respectively at an exposure period of at least 48 h.
12. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against seven ovarian cancer cell line (IGROV1, OVCAR-3, OVCAR-4, OVCAR-5, OVCAR-8, NCI/ADR-RES and SK- OV-3) for GI50 are in the range of 5.71 to 30.6, 2.87 to 14.5, 3.85 to 56.1, 3.25 to 5.87, 6.07 to 49.9, 1.61 to 34.3, and 3.12 to 6.29 μΜ respectively at an exposure period of at least 48 h.
13. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against six breast cancer cell line (MCF7, MDA-MB-231/ATCC, HS 578T, BT-549JD-47D and MDA-MB-468) for GI50 are in the range of 7.98 to 32.2, 3.09 to 9.01, 3.78 to 28.4, 3.27 to 5.23, 4.02 to 20.9, 1.59 to 5.36, and 3.02 to 28.3 μΜ respectively at an exposure period of at least 48 h.
14. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting an in vitro anticancer activity against nine melanoma cancer cell line (LOX IMVI, MALME-3M, M14, MDA-MB-435, SK-MEL-2, SK-MEL-28, SK- MEL-5, UACC-257 and UACC-62) for GI50 are in the range of 4.11 to 39.7, 1.53 to 9.69, 3.61 to 59.8, 2.46 to 7.91, 2.85 to 31.6, 0.710 to 6.40, and 1.73 to 13.7 μΜ respectively at an exposure period of at least 48 h.
15. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting mean graph midpoint values (MG MID) of logioGIso to nine cancer cell lines (leukemia cell line, non small cell lung cell line, colon cell line, CNS cell line, renal cell line, prostate cell line, ovarian cell line, breast and melanoma cell line) in the range of -5.38 to -4.52,-5.48 to -4.0,-5.13 to -4.39,-5.42 to -4.78,-5.43 to - 4.82,-5.92 to -5.24 and-5.49 to-4.53 respectively at an exposure period of at least 48 h.
16. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting mean graph midpoint values (MG MID) of logioLCso to nine cancer cell lines (leukemia cell line, non small cell lung cell line, colon cell line, CNS cell line, renal cell line, prostate cell line, ovarian cell line, breast and melanoma cell line) in the range of -4.00 to -4.03, -4.00, -4.00, -4.00, - 4.00to -4.18, -4.00 to -4.09, - 4.00 respectively at an exposure period of at least 48 h.
17. Compounds of formula 4c, 6d, 6e, 6f, 7d, 7h and 7j as claimed in claim 2, wherein said compounds exhibiting mean graph midpoint values (MG MID) of logioTGI to nine cancer cell lines (leukemia cell line, non small cell lung cell line, colon cell line, CNS cell line, renal cell line, prostate cell line, ovarian cell line, breast and melanoma cell line) in the range of -4.00 to -4.41, -4.00 to -4.19, -4.00 to -4.06, -4.00, -4.00 to -4.54, - 4.00 to to -4.26 and -4.00 to -4.11 respectively at an exposure period of at least 48 h.
18. A process for the preparation of 2-phenyl benzothiazole linked imidazole compounds of general formula A as claimed in claim 1 and the said process comprising the steps of: i. adding 4-nitrobenzoyl chloride (17) (1.1 eq) to a stirred solution of substituted anilines (16a-d)(l eq) in pyridine and reflux for period in the range of 2 to 3h to tain coupled amide of formula 18a-d;
Figure imgf000042_0001
R = hydrogen or methoxy; R = hydrogen or methoxy;
Ri = hydrogen, methoxy or fluoro; Ri = hydrogen, methoxy or fluoro;
R2 = hydrogen or methoxy; R2 = hydrogen or methoxy.
ii. treating the amide of formula (18a-d) as obtained in step (i) with Lawesson's reagent, in toluene under reflux conditions for 6 to 8 fir at 110°C to obtain the corresponding thioamides (19a-d);
Figure imgf000043_0001
iii. treating thioamides (19a-d)(l eq) as obtained in step (ii) with potassium ferricyanide (4 eq) in aqueous sodium hydroxide solution at 90°C for 2 to 3h to obtain the substituted 2-(4-nitro phenyl benzothiazole) of formula 20a-d;
Figure imgf000043_0002
20a-d
iv. reducing substituted 2-(4-nitro phenyl benzothiazole) of formula 20a-d with SnCl2.2H20 to obtain amine compounds (21a-d);
Figure imgf000043_0003
treating amine compounds (21a-d) as obtained in step (iv) with substituted aldehydes in the presence of catalytic amount of 2 to 3 drops of acetic acid in ethanol solution reflux at 80°Cconditions to obtain imine compound followed by treatment with /?-toulenesulfonyl methy isocyanide and potassium carbonate to obtain nitro intermediates (25a-l) and compound of formula 4a-g to 7a-g and 8a-b to 15a-b;
reducing nitro intermediate 25a-l as obtained in step (v) with SnCl2.2H20 in ethanol to obtain compound of formula 4h-j to 7h-j.
Figure imgf000044_0001
purifying compound of formula 4a-g to 7a-g and 8a-b to 15a-b as obtained in step (v) and 4h-j to 7h-j as obtained in step (vi) by column chromatography using solvent to obtain final compounds of general formula 1.
19. Process as claimed in step (v) of claim 15, wherein substituted aldehydes used is selected from the group consisting of 22a-j, 23a-b and 24a-b.
Figure imgf000044_0002
22a;F — Rg— — Hj
22b:R3 = = R5 = R6 =R7 = H; R5=CF3 23a: R8 = H;
22c:R3 = R6 = R7 = H; R4 =OCH3 R5 = F 23b: R8 = OCH3
22d:R3 = R5 = R7 = H; R4 = R6 = OCH3 24a: X = NH;
22e:R3 = R6 = R7 = H; = R5 = OCH3 24b: X = S
22f:R3 = R7 = H; = R5 = R6 = OCH3
22g:F¾ = R6 = H; R3 = R5= R7 = OCH3
22h:R3 = R4 = R6 =R7 = H; R5=N02
22i: R4 = R6 = R7 = H; R3 = N02;R2 = OCH3
22j:R3 = R6 = R7 = H; R4 =N02; R5 = OCH3
20. Process as claimed in step (vii) of claim 15, wherein solvent used are selected from the group consisting of ethyl acetate, hexane, chloroform or methanol.
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