Accepted Manuscript Chalcone based azacarboline analogues as novel antitubulin agents: Design, synthesis, biological evaluation and molecular modelling studies Sahil Sharma, Charanjeet Kaur, Abhishek Budhiraja, Dr. Kunal Nepali, Assistant Professor Manish K. Gupta, A.K. Saxena, P.M.S. Bedi PII:

S0223-5234(14)00732-6

DOI:

10.1016/j.ejmech.2014.08.005

Reference:

EJMECH 7238

To appear in:

European Journal of Medicinal Chemistry

Received Date: 9 March 2014 Revised Date:

27 July 2014

Accepted Date: 4 August 2014

Please cite this article as: S. Sharma, C. Kaur, A. Budhiraja, K. Nepali, M.K Gupta, A.K Saxena, P. Bedi, Chalcone based azacarboline analogues as novel antitubulin agents: Design, synthesis, biological evaluation and molecular modelling studies, European Journal of Medicinal Chemistry (2014), doi: 10.1016/j.ejmech.2014.08.005. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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GRAPHICAL ABSTRACT Chalcone based azacarboline analogues as novel antitubulin agents: Design, synthesis, biological evaluation and molecular modelling studies. Sahil Sharmaa, Charanjeet Kaura, Abhishek Budhirajab, Kunal Nepalia*, Manish K Guptac, A.K Saxenad, PMS Bedia

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3-CARBON BRIDGE

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CHALCONE FRAMEWORK

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MOLECULAR HYBRIDIZATION

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AZACARBOLINE- CHALCONE HYBRIDS AS CONSTRAINED CHALCONE ANALOGUES.

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Highlights

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Synthesis of chalcone based Azacarboline analogues In-vitro cytotoxicity study against a panel of human cancer cell line In-vitro tubulin polymerization assay Microtubule assembly disruption by immunoflorescence technique Molecular modelling studies

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PRELIMINARY COMMUNICATION Chalcone based azacarboline analogues as novel antitubulin agents: Design, synthesis, biological evaluation and molecular modelling studies.

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Sahil Sharmaa, Charanjeet Kaura, Abhishek Budhirajab, Kunal Nepalia*, Manish K Guptac, A.K Saxenad, PMS Bedia

Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar-143005, Punjab

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Faculty of Pharmaceutical Sciences, Shoolini University, Solan, Himachal Pradesh, India

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Molecular Modeling and Pharmacoinformatics Lab, Department of Pharmaceutical chemistry,

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ISF College of Pharmacy, Moga, Punjab-143005, India

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Indian Insitute of Integrative Medicine, Jammu, India

Corresponding author: Dr. Kunal Nepali

Assistant Professor, Department of Pharmaceutical Sciences

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Guru Nanak Dev University, Amritsar, Punjab-143005, India

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Email: [email protected]

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Abstract: The present study involves the design of a series of 3-aryl-9-acetyl-pyridazino[3,4b]indoles as constrained chalcone analogs. A retrosynthetic route was proposed for the synthesis of target compounds. All the synthesised compounds were evaluated for in-vitro cytotoxicity against THP-1, COLO-205, HCT-116 and A-549 human cancer cell lines . The results indicated

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2a, 3a, 5a and 6a possesed significant cytotoxic potential with an IC50 value ranging from 1.13 5.76 µM. Structure activity relationship revealed that the nature of both Ring A and Ring B influences the activity. Substitution of methoxy groups on the phenyl ring (Ring A) and unsubstituted phenyl ring (Ring B) were found to be the preferred structural features. The most

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potent compound 2a was further tested for tubulin inhibition. Compound 2a was found to significantly inhibit the tubulin polymerization (IC50 value – 2.41 µM against THP-1). 2a also

caused

disruption

of microtubule

assembly as evidenced

by

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Compound

Immunoflourescence technique. The significant cytotoxicity and tubulin inhibtion by 2a was rationalized by molecular modelling studies. The most potent structure was docked at colchicine binding site (PDB ID-1SA0) and was found to be stabilized in the cavity via various hydrophobic and hydrogen bonding interactions.

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modelling studies

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Keywords: Carboline, Chalcone, Cytotoxic, Cell line, Tubulin, Constrained, Molecular

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1. Introduction

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Microtubules, key cytoskeletal filaments, are extremely important in the process of mitosis and cell division which makes them an important target for anticancer drugs. Inhibiting tubulin polymerization or interfering with microtubule disassembly ultimately leads to cell cycle arrest or cell apoptosis induction. [1-4].

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Chalcones are well known to inhibit microtubule polymerization and have been most extensively

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explored among the various classes of tubulin inhibitors. Chalcones are precursors of flavonoids and isoflavones and possess diverse array of biological activities, such as anti-cancer [5–7] antiinflammatory [8, 9], anti-tuberculosis [10] and anti-fungal activities [11]. Chemically, chalcones (1,3-diaryl-2-propen-1-ones) possess an enone bridge between two aromatic rings [12]. The extensive investigation on chalcones can be attributed to the ease of synthesis and their relatively

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simpler chemical architecture. Recently the tubulin inhibitory potential of boronic acid chalcone analogs [13], cinnamic acyl sulfonamide derivatives [14], guanidine derivatives of chalcones [4] and antiproliferative effects of flavonoids based novel tetrahydropyran conjugates, chalcone

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based sulfones and bisulfones [15] has been reported. Thus the recent literature clearly indicates

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that chalcones are an area of focus at present. The well established structure activity relationship for chalcones reveals that the rigid arrangement of the two aryl rings remarkably enhances the anticancer potential which tempted us to focus on constrained analogues [16, 17]. The rigid arrangement of chalcones is usually obtained by the incorporation of heterocyclic rings as constraints in place of the enone bridge linking the two aromatic rings.

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Carboline skeleton belongs to the group of indole alkaloids and consist of pyridine ring fused to an indole skeleton. Both α and β carboline skeleton have been extensively reported to exert anticancer

potential

via

varied

mechanisms

[18-24].

Recent

reports

about

the

cytotoxic/anticancer effects of ruthenium(II)-β-carboline complex [18], β-carboline amino acid

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ester conjugates [19], 3-Benzylamino-β-carboline derivatives [20], 1,6,8,9-substituted αcarboline derivatives [21] and β-Carboline-3-(4-benzylidene)-4H-oxazol-5-one [22] highlights the cell killing potential of this alkaloid.

With this background, 3-aryl-9-acetyl-pyridazino[3,4-b]indoles as Chalcone based Azacarboline

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analogues were designed in the present study. The incorporation of azacarboline skeleton within the chalcone framework provides a rigid arrangement of the two aryl rings (Fig. 1). The chemical

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architecture of the designed analogues provides a similar arrangement of two aromatic rings ( two aryl rings separated by a three carbon linker) as in chalcones. The design strategy for the synthesis of the target tubulin inhibitors is shown in Fig. 1. The reason for the inclusion of azacarboline rather than α or β-carboline was primarily due to its bioisosterism to both the carbolines. The retro synthetic path for the designed hybrids is shown in Fig. 2.

2.1. Chemistry

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2. Results

Target compounds were synthesised via a sequence of reactions (Scheme 1) starting from base catalysed condensation of isatin and differently substituted acetophenones. The attack of

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generated carbanions from acetophenones at C-3 of isatins yielded 3-hydroxy-3-(2-oxo-2aryl/heteroaryl-ethyl)-1,3-dihydro-indol-2-ones (1). The condensed product of isatin and

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acetophenonoes (1) were characterized by the appearance of two doublets for the non equivalent geminal protons at 3.65 and 3.95 with a J value of 17.5 Hz. The reaction worked smoothly with electronically and sterically diverse acetophenones i.e acetophenones substituted with electron withdrawing and electron donating groups, acetyl naphthalenes as well as heteroaryl ketones, however only halogenated isatins were tolerated by the reaction as the condensation of acetophenones with methoxy substituted isatin did not proceed. The reason for this is being dealt seperately. The condensed product (1) was then refluxed with a drop of sulphuric acid in glacial acetic acid to yield the dehydrated product (2). The dehydrated product was then refluxed with 4

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hydrazine hydrate in methanol to obtain the target compound. However, only the undesired hydrazone was afforded. The hydrazone was charaterized by the appearance of a doublet band for NH2 stretch at 3350-3340 cm-1 in Infra red spectrum. This could be attributed to weak reactivity of the carbonyl of the isatin ring (2nd position). Thus a different route was followed and

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acetylation of the dehydrated product (2) was carried out to yield 3. The acetylated product was characterized by the appearance of the singlet with an integration of three methyl protons at 2.7 ppm. Acetylation of the NH of isatin ring was done to increase the reactivity of the carbonyl group (2nd position) of isatin ring. Grinding of the acetylated product with hydrazine hydrate

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ultimately yielded the cyclized hybrid (1a). The proton resonances of the charaterstic compound i.e 1a are represented in the Fig. 3.

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2.2. Biological Evaluation

All the synthetics were assayed for in vitro cytotoxicity against THP-1, COLO-205, HCT-116 and A-549 human cancer cell lines using sulforhodamine B19 [25]. The cells were allowed to proliferate in the presence of test material for 48 h. All the synthetics were screened against the cell lines at 50 µM. The molecules displaying percentage inhibition (Table 1) of greater than 60

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% at least against one cell line were only evaluated at different concentrations and IC50 values (Table 2) were calculated. From Table 1 and Table 2, it is clear that the THP-1 cell lines were the most sensitive towards the designed compounds whereas A-549 cell line were the most resistant. Compound 2a, 3a, 5a and 6a displayed significant cytotoxicity with IC50 value ranging from

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1.13 – 4.15 µM, 2.33 – 5.69 µM, 2.41 – 5.76 µM and 2.39 – 5.74 µM against THP-1, COLO-205 and HCT-116. The most active hybrid 2a with trimethoxy phenyl ring as Ring A (IC50 = 1.13

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µM) was almost two folds more active than 3a (dimethoxy phenyl ring as Ring A, IC50 = 2.33 µM), the second most potent hybrid against THP-1 cell line. Careful observation of Table 1 and 2 revealed that the substitution of methoxy groups on the phenyl ring (Ring A) remarkably enhances the cytotoxic potential (compare 1a with 2a, 3a and 4a) whereas the placement of halo and nitro groups diminishes the effect (compare 1a with 11a, 12a, 13a and 14a). Placement of a heteroaryl ring in place of unsubstituted phenyl ring (Ring A) such as pyrrole and thiophene improved the activity profile (compare 1a with 7a and 8a). Both 7a and 8a displayed a similar cytotoxic profile.

A positive effect was observed with the increased number of methoxy 5

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substituents on Ring A such as trimethoxy > dimethoxy > methoxy (compare 2a and 3a with 4a). However placement of naphthyl ring as Ring A also proved to be a good surrogate for methoxy substituted phenyl rings as their IC50 values were similar to the compounds bearing dimethoxy phenyl rings (compare 3a with 5a and 6a). No competition was observed between cytotoxic

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effects of 5a (1-naphthyl) and 6a (2-naphthyl). Overall the preference order of Ring A is as follows: trimethoxy phenyl ring > dimethoxy phenyl ring = 1-naphthyl = 2-naphthyl > methoxy phenyl > heteroaryl > phenyl > phenyl with halo and nitro groups. Any substitution on Ring B significantly decreased the cytotoxic profile of the compounds (compare 2a with 2b, 2c, 2d and

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2e). The influence of the size of the halogens on ring B was also observed. The preference order for substituents at Ring B is as follows H > chloro > bromo > Iodo = dibromo. The structure

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activity relationship has been depicted in Fig. 4.

The most active compounds (2a, 3a, 5a and 6a) were evaluated for their inhibitory effects on tubulin polymerization as per the reoprted assay using a cytoskeleton tubulin polymerization assay kit [26, 27]. Compound 2a (most potent hybrid) with a trimethoxy ring (Ring A) also displayed the most potent antitubulin activity with IC50 value of 2.41 µM. 3a also exhibited significant inhibition of tubulin polymerization with an IC50 value of 4.92 µM. 5a and 6a with

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naphthyl ring (Ring A) which displayed similar cytotoxic profile as that to 3a were found to be endowed with weak inhibitory potential for tubulin polymerization. The results of the in-vitro tubulin polymerization assay clearly indicate that both 2a and 3a exert their cytotoxic effects

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through tubulin inhibition.

The immunofluorenscence technique was used to evaluate the effect of 2a on microtubules. The In this study,

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effect on microtubule structure was determined using confocal microscopy.

untreated THP-1 cell lines showed the normal distribution of microtubules. However, cells treated with compound 2a showed the disrupted microtubule organization at 5µM concentration. The standard compound paclitaxel disrupted the microtubule assembly at 1µM (Fig. 5). 2.3 Molecular modelling studies In order to investigate the recognition process of azacarboline based constrained chalcone analogues at the colchicine-binding site of tubulin, a flexible docking study was performed with 6

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most potent tubulin inhibitor (2a) using GOLD software [28]. The natural tubulin inhibitor ‘colchicine’ binds at the interface of α and β subunits of tubulin (PDB entry: 1SA0) [29]. Compound 2a was docked at the colchicine binding site of tubulin and the best fit conformation was selected on the basis of Gold score and visual inspection. The Fig. 6 shows the binding

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conformation of 2a at the colchicine-binding site of tubulin. The docking study showed that the 2a gets stabilized in tubulin by various hydrogen bonding and hydrophobic interactions. Ring A of 2a is situated in a polar cavity formed by Asn101A, Thr179A, Lys254B and Asn258B. The oxygen atom of para-methoxy group of ring A acts as hydrogen bond acceptor and involved in

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H-bond interactions with side chain NH2 of Asn101A (d=2.28Å). An additional but weak Hbond was also observed between methoxy function at meta-position (CH: H-bond donor) and

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main chain carbonyl function of Thr179A (C=O: H-bond acceptor; d= 2.23 Å).3 The ring B, C and D of 2a are extended towards the β subunits of tubulinand positioned in a hydrophobic cavity formed by Leu242B, Leu248B, Leu255B, Ala316B, Ala317B, Val318B and Ile378B. The ring B is sandwiched between Leu248B and Leu255B. This may be suggested that the aliphatic site chain of Leu248B is involved in alkyl-aryl interactions with ring B. [29] The similar interaction was also observed between ring A and aliphatic side chain Lys254B. Rind D is

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situated in a hydrophobic cleft formed by Ala316B, Ala317B, Val318B and Ile378B (Fig. 6) [30]. 3. Conclusions

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Chalcone based Azacarboline analogues were designed, synthesised and evaluated for cytotoxicty against a panel of human cancer cell lines in the present study. The nature of both

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Ring A and Ring B was found to have significant influence on the cytotoxic potential. Tubulin inhibitory potential of the most potent compound 2a (with a trimethoxy phenyl ring as Ring A and unsubstituted Ring B) was confirmed by in vitro tubulin assay and Immunoflourescence technique The significant inhibition of tubulin by compound 2a was also rationalized by molecular modelling studies. Detailed investigation of compound 2a is under progress.

Experimental section 7

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4.1. Chemistry The reagents were purchased from Sigma–aldrich, Loba and CDH, India and used without further purification. All yields refer to isolated products after purification. Products were NMR). 1H-NMR and

13

13

C

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characterized by comparison with authentic samples and by spectroscopic data (1H and

C-NMR Spectra were recorded on a 300 MHz FT-NMR and 75 or 125

MHz respectively. The spectra were measured in CDCl3 and DMSO-d6 relative to TMS (0.00 ppm). In 1H-NMR chemical shifts were reported in δ values using tetramethylsilane as internal

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standard with number of protons, multiplicities (s-singlet, d-doublet, t-triplet, q-quartet, mmultiplet, dd-double doublet) and coupling constants (J) in Hz (Hertz) in the solvent indicated.

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Melting points were determined in open capillaries and were uncorrected.

4.2. Experimental procedure for the synthesis of substituted 2-(3-hydroxy-2-oxoindolin-3-yl)1-arylethanone (1):

An aqueous solution of sodium hydroxide (5%, 10 mL) was added slowly to the stirring solution of isatin (1 mmol) and appropriate aryl acetophenone (1 mmol) in ethanol (20 mL) in 100 mL

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conical flask. The stirring was continued for 2 hours and the completion of reaction was monitored by TLC. The reaction on completion was poured onto ice, solid obtained after filtration was crystallized from ethanol. The physical data for the characteristic compound is

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shown below:

4.2.1. 2-(3-hydroxy-2-oxoindolin-3-yl)-1-phenylethanone (1) White solid, yield 92%; mp: 132◦133◦C; 1H NMR (300 MHz, CDCl3): δ = 10.21 (s, 1H), 7.86 (d, J = 7.8 Hz, 2H), 7.56 (t, J = 7.2

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Hz, 1H), 7.42-7.46 (2H, m), 7.24 (d, J = 7.2 Hz, 1H), 7.16 (t, J = 7.2 Hz, 1H), 6.87 (m, 2H), 6.08 (s, 1H), 3.95 (d, J = 17.5 Hz, 1H), 3.65 (d, J = 17.5 Hz, 1H). Anal. Calcd. For C16H13NO3: C, 71.90; H, 4.90; N, 5.24. Found: C, 72.28; H, 5.13; N, 5.01.

4.3. Experimental procedure for the synthesis of (Z)-3-(2-oxo-2-arylethylidene)indolin-2-one (2): 8

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A mixture of 2-(3-hydroxy-2-oxoindolin-3-yl)-1-phenylethanone (1 mmol) and 10 mL of acetic acid and a drop of sulfuric acid was refluxed for 1 hour. The completion of reaction was monitored by TLC. The reaction mixture on completion was poured onto ice and the precipitates were collected and crystallized from ethanol. The physical data for the characteristic compound

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is shown below:

4.3.1. (Z)-3-(2-oxo-2-phenylethylidene)indolin-2-one (2) Orange red solid; yield 90%; mp:187◦188◦C; 1H NMR (300 MHz, CDCl3); δ = 10.15 (s, 1H, D2O exchangeable proton); 8.26 (d, J =

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7.8 Hz, 1H); 8.10 (d, J = 7.5 Hz, 2H); 7.80 (s, 1H); 7.62 (t, J = 7.5 Hz, 1H); 7.52 (t, J = 7.5 Hz, 2H); 7.26 (t, J = 7.5 Hz, 1H); 6.93 (t, J = 7.8 Hz, 1H); 6.85 (d, J = 7.8 Hz, 1H). Anal. Calcd. For

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C16H11NO2: C, 77.10; H, 4.45; N, 5.62. Found: C, 77.32; H, 4.18; N, 5.73.

4.4. Experimental procedure for the synthesis of (Z)-1-acetyl-3-(2-oxo-2-arylethylidene) indolin-2-one (3):

A mixture of (Z)-3-(2-oxo-2-arylethylidene)indolin-2-one (1 mmol) and acetic anhydride was stirred in the presence of DMAP (0.1 mmol) for 2 hours under anhydrous condition. The completion of reaction was monitored by TLC. The reaction mixture on completion was poured

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onto ice and the precipitates were collected and crystallized from ethanol. The physical data for the characteristic compound is shown below:

4.4.1. (Z)-1-acetyl-3-(2-oxo-2-phenylethylidene)indolin-2-one (3) Yellow solid; yield 85%; mp:

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155◦-156◦C; 1H NMR (300 MHz, CDCl3); δ = 8.32 (d, J = 8.4 Hz, 1H), 8.10 (s, J = 7.5 Hz, 2H), 7.88 (s, 1H), 7.66 (t, J = 7.5 Hz, 1H), 7. 56 (d, J = 7.2 Hz, 2H), 7.45 (t, J = 8.4 Hz, 1H), 7.19 (t, J = 7.2 Hz, 1H), 7.00 (d, J = 7.8 Hz, 1H), 2.77 (s, 3H). Anal. Calcd. For C18H13NO3: C, 74.22; H,

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4.50; N, 4.81. Found: C, 74.05; H, 4.64; N, 4.77. 4.5. Experimental procedure for the synthesis of 3-Aryl-9-acetyl-pyridazino[3,4-b]indoles: A mixture of (Z)-1-acetyl-3-(2-oxo-2-phenylethylidene)indolin-2-one (1 mmol) and hydrazine monohydrate 80% (1 mmol) was ground in china dish for 15 mins. The completion of reaction was monitored by TLC. The reaction mixture on completion was poured onto ice and the precipitates were collected and crystallized from ethanol. The physical data for the characteristic compound is shown below: 9

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4.5.1. 3-Phenyl-9-acetyl-pyridazino[3,4-b]indole (1a) Pale yellow fluffy powder; yield 90%; Mp 125◦-126◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.40 (d, J = 8.4 Hz, 1H); 8.24 (d, J = 6.9 Hz, 2H); 8.13 (d, J = 8.4 Hz, 1H); 8.10 (s, 1H); 7.73-7.78 (m, 2H); 7.45-7.61 (m, 3H); 2.08 (s, 3H). 13

C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.48, 116.78, 123.33, 125.31, 127.18, 128.88,

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129.42, 129.86, 130.32, 138.00, 141.16, 147.77, 155.62, 165.67, 167.87, 168.46. IR (KBr, cm-1) 3030, 2998, 1665, 1565, 1552, 1130. MS: M+ at m/z 287. Anal. Calcd. For C18H13N3O: C, 75.25; H, 4.56; N, 14.63. Found: C, 75.19; H, 4.73; N, 14.81.

4.5.2. 3-(3,4,5-Trimethoxyphenyl)-9-acetyl-pyridazino[3,4-b]indole (2a) Pale yellow fluffy

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powder; yield 90%; Mp 197◦-198◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.46 (bs, 1H), 8.218.34 (m, 2H), 7.96 (d, J = 8.7 Hz, 1H), 7.83 (dd, J = 1.8 and 9.0 Hz, 1H), 7.55 (s, 2H), 3.91 (s,

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6H), 3.76 (s, 3H), 2.05 (s, 3H). 13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 19.58, 56.59, 60.63, 105.31, 118.34, 124.82, 131.33, 131.98, 133.71, 139.94, 146.61, 153.77, 156.38, 166.00, 169.13. IR (KBr, cm-1) 3045, 2943, 1667, 1561, 1545, 1211, 1137. MS: M+ at m/z 287. MS: M+ at m/z 377. Anal. Calcd. For C21H19N3O4: C, 66.83; H, 5.07; N, 11.13. Found: C, 66.84; H, 5.17; N, 11.45.

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4.5.3. 3-(3,4-Dimethoxyphenyl)-9-acetyl-pyridazino[3,4-b]indole (3a) Light yellow solid; yield 75%; Mp 180◦-181◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.38 (d, J = 7.8 Hz, 1H); 8.12 (d, J = 8.1 Hz, 1H); 8.07 (s, 1H); 7.93 (s, 1H); 7.72-7.79 (m, 2H); 7.58 (t, J = 7.2 Hz, 1H); 7.03 (d, J = 8.4 Hz, 1H); 3.92 (s, 6H); 2.01 (s, 3H).

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C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 19.53,

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56.02, 110.60, 112.12, 116.98, 120.81, 123.54, 125.78, 127.30, 129.71, 130.78, 131.09, 141.46, 148.19, 149.48, 151.07, 155.84, 166.36, 168.20. MS: M+ at m/z 347. Anal. Calcd. For

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C20H17N3O3: C, 69.15; H, 4.93; N, 12.10. Found: C, 69.45; H, 5.28; N, 12.43. 4.5.4. 3-(4-Methoxyphenyl)-9-acetyl-pyridazino[3,4-b]indole (4a) Cream colored solid; yield 78%; Mp 157◦-158◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.33 (d, J = 8.4 Hz,1H); 8.27 (d, J = 8.8 Hz, 2H); 8.10 (d, J = 8.4 Hz, 1H); 8.09 (s, 1H); 7.82 (t, J = 7.2 Hz, 1H); 7.62 (t, J = 7.6 Hz, 1H); 7.13 (d, J = 8.8 Hz, 2H); 3.86 (s, 3H); 1.99 (s, 3H). 13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.89, 55.79, 114.80, 116.85, 123.56, 125.87, 127.27, 128.45, 129.22, 129.74, 130.76, 130.97, 141.62, 148.32, 155.79, 161.35, 166.29, 168.54, 169.00. MS: M+ at m/z 317. Anal. Calcd. For C19H15N3O2: C, 71.91; H, 4.76; N, 13.24. Found: C, 71.83; H, 4.47; N, 13.44. 10

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4.5.5. 3-Naphth-2-yl-9-acetyl-pyridazino[3,4-b]indole (5a) Creamish white solid; yield 70%; Mp 251-252◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.88 (s, 1H); 8.51 (dd, J = 1.2 and 8.4 Hz, 1H); 8.37 (d, J = 8.8 Hz, 1H); 8.33 (s, 1H) ; 8.20 (d, J = 8.8 Hz, 1H); 8.11-8.16 (m, 2H); 8.01 (dd, J = 3.2 and 6.04 Hz, 1H); 7.88 (t, J = 8.8 Hz, 1H); 7.69 (t, J = 7.6 Hz, 1H); 7.60-7.62 (m, 13

C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 21.08, 117.48, 123.95, 125.00,

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2H); 2.05 (s, 3H).

125.93, 127.17, 127.53, 127.71, 127.84, 128.10, 129.00, 129.31, 130.00, 130.97, 133.51, 134.09, 135.91, 141.87, 148.38, 155.98, 166.27, 169.05. MS: M+ at m/z 337. Anal. Calcd. For

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C22H15N3O: C, 78.32; H, 4.48; N, 12.46. Found: C, 78.22; H, 4.19; N, 12.74.

4.5.6. 3-Naphth-1-yl-9-acetyl-pyridazino[3,4-b]indole (6a) Creamish white solid; yield 70%; Mp 245◦-246◦C; 1H NMR (300 MHz, CDCl3): δ = 8.44 (dd, J = 1.2 and 8.4 Hz, 1H); 8.38 (d, J =

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8.8 Hz, 1H); 8.35 (s, 1H) ; 8.22 (d, J = 8.8 Hz, 1H); 8.11-8.16 (m, 2H); 8.01 (dd, J = 3.2 and 6.04 Hz, 1H); 7.88 (t, J = 8.8 Hz, 1H); 7.69 (t, J = 7.6 Hz, 1H); 7.60-7.62 (m, 3H); 2.05 (s, 3H).13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.98, 122.44, 124.31, 124.71, 125.67, 125.94, 126.72, 127.47, 128.75, 128.96, 130.07, 130.82, 131.52, 132.14, 132.71, 133.95. 137.41, 140.33, 146.66, 159.21, 165.73, 169.18. MS: M+ at m/z 337. Anal. Calcd. For C22H15N3O: C, 78.32; H, 4.48; N,

TE D

12.46. Found: C, 78.58; H, 4.66; N, 12.15.

4.5.7. 3-(1H)-Pyrrol-2-yl-9-acetyl-pyridazino[3,4-b]indole (7a) Pale brown solid; yield 56%; Mp 232◦-233◦C; 1H NMR (300 MHz, CDCl3): δ = 6.18 (s, 1H, D2O exchangeable proton); 8.48 (d, J = 8.4 Hz, 1H); 7.99 (d, J = 7.8 Hz, 1H) ; 7.84 (s, 1H); 7.48-7.53 (m, 1H), 7.12-7.27 (m, 2H),

EP

6.90 (t, J = 7.2 Hz, 2H), 2.06 (s, 3H). 13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.90, 110.35, 111.14, 116.20, 123.04, 125.97, 126.26, 128.80, 130.69, 131.33, 141.43, 148.19, 150.41, 166.36,

AC C

169.02. MS: M+ at m/z 276. Anal. Calcd. For C16H12N4O: C, 69.55; H, 4.38; N, 20.28. Found: C, 66.89; H, 4.08; N, 19.89.

4.5.8. 3-Thiophen-2-yl-9-acetyl-pyridazino[3,4-b]indole (8a) Pale brown solid; yield 56%; Mp 202◦-203◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.29 (d, J = 8.4 Hz, 1H); 8.00-8.10 (m, 3H), 7.76-7.82 (m, 2H), 7.61 (m, 1H), 7.23 (m, 1H), 1.98 (s, 3H).13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.90, 116.11, 123.85, 126.00, 127.44, 128.19, 129.17, 130.66, 131.11, 141.97, 144.52, 148.01, 151.93, 166.05, 168.48, 169.04. MS: M+ at m/z 293. Anal. Calcd. For C16H11N3OS: C, 65.51; H, 3.78; N, 14.32; S, 10.93. Found: C, 65.82; H, 4.05; N, 14.66; S, 10.58. 11

ACCEPTED MANUSCRIPT

4.5.9. 3-(2-Aminoacetylphenyl)-9-acetyl-pyridazino[3,4-b]indole (9a) Yellow coloured solid; yield 85%; Mp 185◦-186◦C; 1H NMR (300 MHz, DMSO-d6): δ = 10.44 (s, 1H, D2O exchangeable proton); 8.40 (d, J = 8.4 Hz, 1H); 8.20 (d, J = 8.0 Hz, 1H); 8.00-8.03 (m, 2H); 7.92 (t, J = 7.6 Hz, 1H); 7.75 (t, J = 7.6 Hz, 1H); 7.48-7.52 (m, 3H); 2.35 (s, 3H); 2.01 (s, 3H). 13C

RI PT

NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 19.55, 24.48, 114.24, 117.29, 117.96, 121.00, 122.44, 124.00, 125.55, 126.92, 130.06, 131.00, 139.11, 141.22, 141.92, 148.66, 150.88, 155.99, 166.232, 169.87. Anal. Calcd. For C20H16N4O2: 69.76; H, 4.68; N, 16.27. MS: M+ at m/z 344.

SC

Anal. Calcd. For C20H16N4O2: C, 69.76; H, 4.68; N, 16.27. Found: C, 70.03; H, 4.38; N, 16.26. 4.5.10. 3-(3-Aminoacetylphenyl)-9-acetyl-pyridazino[3,4-b]indole (10a) Yellow colored solid; yield 70%; Mp 130◦-131◦C; 1H NMR (300 MHz, DMSO-d6): δ =

10.20

(s, 1H, D2O

M AN U

exchangeable proton); 8.44 (s, 1H); 8.33 (d, J = 8.0 Hz, 1H); 8.13 (d, J = 8.4 Hz, 1H); 8.09 (s, 1H); 7.96 (d, J = 7.8 Hz, 1H); 7.83-7.88 (m, 2H); 7.68 (t, J = 7.2 Hz, 1H); 7.55 (t, J = 8.0 Hz, 1H); 2.35 (s, 3H); 2.02 (s, 3H).

13

C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 19.56, 24.47,

114.20, 117.23, 118.16, 121.04, 122.49, 123.90, 125.85, 127.12, 129.86, 131.00, 139.01, 140.42, 141.84, 148.33, 150.83, 155.95, 166.26, 169.07. MS: M+ at m/z 344. Anal. Calcd. For

TE D

C20H16N4O2: 69.76; H, 4.68; N, 16.27. Found: C, 69.43; H, 4.83; N, 16.65. 4.5.11. 3-(4-Fluorophenyl)-9-acetyl-pyridazino[3,4-b]indole (11a) Yellow powder; yield 92% ; Mp 235◦-236◦C; ; 1H NMR (300 MHz, DMSO-d6); δ = 8.41 (d, J = 8.1 Hz, 1H); 8.29-8.32 (m, 2H); 8.12 (d, J = 8.4 Hz, 1H); 8.09 (s, 1H); 7.77 (t, J = 7.8 Hz, 1H); 7.59 (t, J = 7.8 Hz, 1H);

EP

7.26 (m, 2H); 2.08 (s, 3H). 13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.90, 116. 22, 116.50, 117.18, 123.78, 125.78, 127.82, 129.91, 130.01, 130.12, 130.98, 135.03, 141.79, 148.23, 155.11,

AC C

162.24, 166.18, 169.07. MS: M+ at m/z 305. Anal. Calcd. For C18H12FN3O: C, 70.81; H, 3.96; N, 13.76. Found: C, 71.00; H, 3.65; N, 13.77. 4.5.12. 3-(4-Chlorophenyl)-9-acetyl-pyridazino[3,4-b]indole (12a) White solid; yield 85%; Mp 260-261◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.33-8.37 (m, 2H); 8.15 (d, J = 8.8 Hz, 2H); 8.16 (s, 1H); 7.87 (t, J = 7.2 Hz, 1H); 7.69 (t, J = 7.6 Hz, 1H); 7.66 (d, J = 8.8 Hz, 2H); 1.99 (s, 3H). 13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.90, 117.17, 123.95, 125.89, 128.00, 129.50, 129.97, 131.05, 135.38, 137.30, 141.86, 148.23, 154.89, 166.12, 168.48, 169.04. MS: M+ at m/z

12

ACCEPTED MANUSCRIPT

321. Anal. Calcd. For C18H12ClN3O: C, 67.19; H, 3.76; N, 13.06. Found: C, 67.42; H, 3.57; N, 11.09. 4.5.13. 3-(4-Bromophenyl)-9-acetyl-pyridazino[3,4-b]indole (13a) White coloured powder;

RI PT

yield 89%; Mp 269-270◦C; 1H NMR (300 MHZ, DMSO-d6): δ = 8.33-8.37 (m, 2H); 8.25 (d, J = 8.8 Hz, 2H); 8.16 (s,1H); 7.87 (t, J = 7.2 Hz, 1H); 7.69 (t, J = 7.6 Hz, 1H); 7.81 (d, J = 8.8 Hz, 2H); 1.99 (s, 3H).

13

C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.41, 116.63, 123.51, 123.73,

125.41, 127.50, 129.28, 129.48, 130.54, 131.92, 137.20, 141.41, 147.79, 154.52, 165.60, 167.94,

SC

168.51. MS: M+ at m/z 365. Anal. Calcd. For C18H12BrN3O: C, 59.03; H, 3.30; N, 11.47. Found: C, 59.14; H, 3.68; N, 11.69.

4.5.14. 3-(4-Nitrophenyl)-9-acetyl-pyridazino[3,4-b]indole (14a) Yellowish powder; yield 85%;

M AN U

Mp 255-256◦C; 1H NMR (300 MHz, DMSO-d6); δ = 8.56 (d, J = 9.0 Hz, 2H); 8.38-8.45 (m, 3H); 8.26 (s, 1H); 8.18 (d, J = 8.1 Hz, 1H); 7.83 (t, J = 7.0 Hz, 1H); 7.67 (d, J = 7.5 Hz, 1H); 1.99 (s, 3H). 13C NMR (DMSO-d6, 75 MHz, δ, TMS = 0): 20.90, 117.75, 124.32, 124.59, 125.96, 128.68, 129.01, 130.22, 131.33, 142.18, 144.38, 148.28, 148.69, 153.94, 165.93, 168.44, 169.02. MS: M+ at m/z 332. Anal. Calcd. For C18H12N4O3: C, 65.06; H, 3.64; N, 16.86. Found: C, 65.43; H, 3.86;

TE D

N, 16.51.

4.5.15. 3-Phenyl-5-chloro-9-acetyl-pyridazino[3,4-b]indole (1b) Pale yellow fluffy powder; yield 90%; Mp 255-256◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.45 (s, 1H), 8.29 (m, 2H), 8.148.21 (m, 2H), 7.86 (d, J = 9.00 Hz, 1H), 7.56-7.58 (m, 3H), 2.05 (s, 3H). 13C NMR (DMSO-d6,

EP

125 MHz, δ, TMS = 0): 25.71, 123.13, 123.24, 129.35, 129.46, 129.55, 132.36, 132.47, 133.89, 135.78, 137.26, 143.07, 144.85, 151.69, 161.35, 170.47, 173.73. MS: M+ at m/z 321. Anal.

AC C

Calcd. For C18H12ClN3O: C, 67.19; H, 3.76; N, 13.06. Found: C, 66.94; H, 3.81; N, 12.99. 4.5.16. 3-(3,4,5-Trimethoxyphenyl)-5-chloro-9-acetyl-pyridazino[3,4-b]indole (2b) Pale yellow fluffy powder; yield 90%; Mp 280-281◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.47 (s, 1H), 8.10-8.15 (m, 2H), 7.65 (d, J = 9.0 Hz, 1H), 7.52 (s, 2H), 3.94 (s, 6H), 3.77 (s, 3H), 2.04 (s, 3H). 13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.36, 55.71, 59.78, 109.05, 118.14, 126.24,

131.83, 131.98, 133.64, 139.89, 146.79, 153.28, 156.97, 165.34, 169.71. MS: M+ at m/z 411. Anal. Calcd. For C21H18ClN3O4: C, 61.24; H, 4.41; N, 10.20. Found: C, 61.48; H, 4.49; N, 10.01. 13

ACCEPTED MANUSCRIPT

4.5.17. 3-(3,4-Dimethoxyphenyl)-5-chloro-9-acetyl-pyridazino[3,4-b]indole (3b) Light yellow solid; yield 75%; Mp 268-269◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.44 (d, J = 2.1 Hz, 1H), 8.08-8.15 (m, 2H), 8.00 (s, 1H), 7.69-7.92 (m, 2H), 7.06 (d, J = 8.4 Hz, 1H), 3.99 (s, 3H), 3.92 (s, 3H), 2.07 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.93, 56.10, 110.53, 111.42,

RI PT

118.15, 120.71, 124.26, 124.66, 130.73, 131.15, 131.37, 132.20, 139.50, 146.88, 149.41, 150.96, 156.71, 165.71, 169.12. MS: M+ at m/z 381. Anal. Calcd. For C20H16ClN3O3: C, 62.91; H, 4.22; N, 11.01. Found: C, 63.06; H, 4.35; N, 10.88.

4.5.18. 3-(4-Methoxyphenyl)-5-chloro-9-acetyl-pyridazino[3,4-b]indole (4b) Cream colored

SC

solid; yield 78%; Mp 275-276◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.41 (s, 1H), 8.22-8.28 (d, J = 8.7 Hz, 2H), 8.08-8.15 (m, 2H), 7.77 (d, J = 9.00 Hz, 1H), 7.10 (d, J = 8.7 Hz, 2H), 3.83 (s, 13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.93, 55.51, 114.43, 117.99,

M AN U

3H), 2.02 (s, 3H).

124.21, 124.67, 129.06, 130.79, 131.44, 132.04, 139.73, 146.93, 156.22, 161.36, 165.77, 169.19. MS: M+ at m/z 351. Anal. Calcd. For C19H14ClN3O2: C, 64.87; H, 4.01; N, 11.94.. Found: C, 64.76; H, 3.89; N, 12.08.

4.5.19. 3-Naphth-2-yl-5-chloro-9-acetyl-pyridazino[3,4-b]indole (5b) Creamish white solid;

TE D

yield 70%; Mp 288-289◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.86 (s, 1H), 8.47 (s, 1H), 8.39 (s, 1H), 8.18-8.24 (m, 2H), 8.06-8.09 (m, 2H), 7.85 (m, 1H), 7.82 (m, 1H), 7.60 (m, 2H), 2.01 (s, 3H).

13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 21.38, 118.88, 123.97, 125.98, 126.83,

127.13, 127.81, 127.07, 127.55, 128.99, 129.50, 129.23, 130.39, 131.05, 133.15, 134.44, 135.75,

EP

141.21, 148.66, 156.77, 165.28, 169.17. MS: M+ at m/z 371. Anal. Calcd. For C22H14ClN3O: C, 71.07; H, 3.80; N, 11.30. Found: C, 70.85; H, 4.02; N, 11.44.

AC C

4.5.20. 3-Naphth-1-yl-5-chloro-9-acetyl-pyridazino[3,4-b]indole (6b) Creamish white solid; yield 70%; Mp 285-286◦C; 1H NMR (300 MHz, CDCl3): δ = 8.48 (s, 1H), 8.09-8.28 (m, 5H), 7.69-7.91 (m, 2H), 7.43-7.58 (m, 3H), 1.98 (s, 3H).

13

C NMR (DMSO-d6, 125 MHz, δ, TMS =

0): 20.99, 122.24, 124.32, 124.72, 125.68, 125.94, 126.72, 127.47, 128.75, 128.96, 130.07, 130.83, 131.52, 132.15, 132.71, 133.95, 137.42, 140.34, 146.67, 159.21, 165.71, 169.20. MS: M+ at m/z 371. Anal. Calcd. For C22H14ClN3O: C, 71.07; H, 3.80; N, 11.30. Found: C, 71.12; H, 3.99; N, 11.03.

14

ACCEPTED MANUSCRIPT

4.5.21. 3-(1H)-Pyrrol-2-yl-5-chloro-9-acetyl-pyridazino[3,4-b]indole (7b) Pale brown solid; yield 56%; Mp 272-273◦C; 1H NMR (300 MHz, CDCl3): δ = 6.24 (s, 1H, D2O exchangeable proton); 8.32 (d, J = 2.1 Hz, 1H), 7.94-7.99 (m, 2H), 7.77 (dd, J = 1.8 and 8.7 Hz, 1H), 6.93-7.40 (m, 2H), 6.24 (d, J = 2.1 Hz, 1H), 1.99 (s, 3H).

13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0):

RI PT

21.01, 110.50, 111.75, 117.17, 120.51, 122.10, 123.48, 123.82, 124.85, 130.64, 130.83, 140.50, 146.75, 150.86, 165.86, 169.13. MS: M+ at m/z 310. Anal. Calcd. For C16H11ClN4O: C, 61.84; H, 3.57; N, 18.03. Found: C, 62.01; H, 3.63; N, 17.95.

4.5.22. 3-(4-Chlorophenyl)-5-chloro-9-acetyl-pyridazino[3,4-b]indole (8b) White solid; yield

SC

85%; Mp 276-277◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.46 (s, 1H), 8.34 (d, J = 7.5 Hz, 2H), 8.25 (s, 1H), 8.16 (d, J = 9.0 Hz, 1H), 7.88 (d, J = 7.8 Hz, 1H), 7.65 (d, J = 7.5 Hz, 2H), 2.01 (s, 13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 21.00, 118.43, 123.59, 126.87, 128.12,

M AN U

3H).

129.45, 129.95, 131.33, 135.47, 137.56, 141.22, 147.32, 156.11, 165.28, 169.16. MS: M+ at m/z 355. Anal. Calcd. For C18H11Cl2N3O: C, 60.69; H, 3.11; N, 11.80. Found: C, 60.91; H, 2.93; N, 12.04.

4.5.23. 3-(4-Bromophenyl)-5-chloro-9-acetyl-pyridazino[3,4-b]indole (9b) White coloured

TE D

powder; yield 89%; Mp 280-281◦C; 1H NMR (300 MHZ, DMSO-d6): δ = 8.48 (s, 1H), 8.20 (d, J = 9.0 Hz, 2H), 8.11 (d, J = 9.0 Hz, 1H), 7.94 (bs, 2H), 7.69 (d, J = 9.0 Hz, 2H), 2.08 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.98, 118.11, 124.55, 124.68, 124.76, 129.84, 131.63, 132.11, 132.47, 132.63, 137.27, 141.00, 146.74, 155.58, 165.68, 169.27. MS: M+ at m/z

10.54.

EP

399. Anal. Calcd. For C18H11ClBrN3O: C, 53.96; H, 2.77; N, 10.49. Found: C, 54.16; H, 2.56; N,

AC C

4.5.24. 3-(4-Nitrophenyl)-5-chloro-9-acetyl-pyridazino[3,4-b]indole (10b) Yellowish powder; yield 85%; Mp 268-269◦C; 1H NMR (300 MHz, DMSO-d6); δ = 8.51-8.57 (m, 3H), 8.34-8.41 (m, 3H), 8.14 (m, 1H), 7.82 (d, J = 9.0 Hz, 1H), 2.05 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.93, 118.74, 124.18, 124.82, 125.01, 128.78, 131.42, 132.01, 133.90, 140.11, 144.15, 146.89, 148.63, 154.20, 165.33, 169.19. MS: M+ at m/z 366. Anal. Calcd. For C18H11ClN4O3: C, 58.95; H, 3.02; N, 15.28. Found: C, 59.11; H, 2.87; N, 15.33.

15

ACCEPTED MANUSCRIPT

4.5.25. 3-Phenyl-5-bromo-9-acetyl-pyridazino[3,4-b]indole (1c) Pale yellow fluffy powder; yield 90%; Mp 258-259◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.42-8.64 (m, 2H), 8.39-8.42 (m, 2H), 8.09 (d, J = , 8.7 Hz, 1H), 7.97 (d, J = 9.0 Hz, 1H), 7.45-7.61 (m, 3H), 2.00 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 21.01, 118.25, 121.05, 125.08, 127.83, 127.99,

RI PT

129.49, 129.99, 130.72, 132.16, 134.00, 136.55, 138.15, 140.71, 146.97, 156.76, 165.74, 169.11. MS: M+ at m/z 365. Anal. Calcd. For C18H12BrN3O: C, 59.03; H, 3.30; N, 11.47. Found: C, 58.84; H, 3.49; N, 11.29.

fluffy powder; yield 90%; Mp 290-291◦C;

1

SC

4.5.26. 3-(3,4,5-Trimethoxyphenyl)-5-bromo-9-acetyl-pyridazino[3,4-b]indole (2c) Pale yellow H NMR (300 MHz, DMSO-d6): δ = 8.42 (s, 1H),

8.09-8.15 (m, 2H), 7.66 (d, J = 9.0 Hz, 1H), 7.50 (s, 2H), 3.99 (s, 6H), 3.77 (s, 3H), 2.01 (s, 3H). 13

M AN U

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.78, 55.98, 59.88, 109.93, 119.31, 124.97,

131.39, 131.48, 133.92, 139.83, 146.67, 153.61, 156.88, 161.82, 166.55, 169.32. MS: M+ at m/z 455. Anal. Calcd. For C21H18BrN3O4: C, 55.28; H, 3.98; N, 9.21. Found: C, 55.43; H, 4.25; N, 8.91.

4.5.27. 3-(3,4-Dimethoxyphenyl)-5-bromo-9-acetyl-pyridazino[3,4-b]indole (3c) Light yellow

TE D

solid; yield 75%; Mp 285-286◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.72 (s, 1H), 8.14 (s, 1H), 8.05 (d, J = 8.4 Hz, 1H), 7.85-7.88 (m, 3H), 7.12 (d, J = 8.1 Hz, 1H), 3.89 (s, 3H), 3.83 (s, 3H), 1.98 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.47, 56.88, 58.01, 111.36, 113.82, 118.98, 121.43, 123.48, 125.36, 127.38, 129.72, 130.71, 131.95, 141.98, 148.99, 149.66, 155.61,

EP

151.07, 161.41, 165.47, 169.74. MS: M+ at m/z 425. Anal. Calcd. For C20H16BrN3O3: C, 56.35; H, 3.78; N, 9.86. Found: C, 56.71; H, 3.92; N, 9.99.

AC C

4.5.28. 3-(4-Methoxyphenyl)-5-bromo-9-acetyl-pyridazino[3,4-b]indole (4c) Cream colored solid; yield 78%; Mp 278-279◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.58 (s, 1H), 8.25-8.37 (m, 5H), 7.13-7.16 (m, 2H), 3.89 (s, 3H), 1.99 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.97, 55.89, 114.99, 118.34, 119.85, 125.61, 126.32, 128.05, 129.60, 130.09, 136.37, 141.53, 143.78, 156.82, 161.93, 165.41, 169.19. MS: M+ at m/z 395. Anal. Calcd. For C19H14BrN3O2: C, 57.59; H, 3.56; N, 10.60;. Found: C, 57.41; H, 3.72; N, 10.42;.

16

ACCEPTED MANUSCRIPT

4.5.29. 3-Naphth-2-yl-5-bromo-9-acetyl-pyridazino[3,4-b]indole (5c) Creamish white solid; yield 70%; Mp 295-296◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.89 (s, 1H), 8.61 (s, 1H), 8.378.50 (m, 2H), 8.09-8.14 (m, 3H), 7.79 (m, 2H), 7.59 (m, 2H), 2.01 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 21.04, 118.40, 121.10, 124.90, 125.14, 127.22, 127.80, 127.85, 128.06,

RI PT

128.12, 129.05, 129.36, 132.16, 133.48, 134.05, 134.20, 135.49, 140.86, 147.03, 156.60, 165.79, 169.16. MS: M+ at m/z 415. Anal. Calcd. For C22H14BrN3O: C, 63.48; H, 3.39; N, 10.09. Found: C, 63.56; H, 3.42; N, 9.89.

4.5.30. 3-Naphth-1-yl-5-bromo-9-acetyl-pyridazino[3,4-b]indole (6c) Creamish white solid;

SC

yield 70%; Mp 288-289◦C; 1H NMR (300 MHz, CDCl3): δ = 8.42 (s, 1H), 8.03-8.18 (m, 5H), 7.78-7.92 (m, 2H), 7.56-7.69 (m, 3H), 1.96 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS =

M AN U

0): 20.67, 117.27, 122.86, 124.24, 124.69, 125.34, 125.47, 126.82, 127.75, 128.66, 130.38, 130.84, 131.25, 132.36, 132.84, 133.89, 137.52, 141.87, 146.53, 159.44, 165.31, 169.79. MS: M+ at m/z 415. Anal. Calcd. For C22H14BrN3O: C, 63.48; H, 3.39; N, 10.09. Found: C, 63.65; H, 3.48; N, 9.81.

4.5.31. 3-(4-Chlorophenyl)-5-bromo-9-acetyl-pyridazino[3,4-b]indole (7c) White solid; yield

TE D

85%; Mp 282-283◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.64 (d, J = 2.4 Hz, 1H), 8.42 (d, J = 8.7 Hz, 2H), 8.24 (s, 1H), 8.08 (d, J = 9.00 Hz, 1H), 8.00 (d, J = 1.8 Hz, 1H), 7.64 (d, J = 8.4 Hz, 2H), 2.00 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 21.02, 116.87, 118.98, 123.76, 125.68, 128.42, 129.82, 130.64, 131.45, 135.78, 137.21, 141.86, 147.12, 155.33, 165.21, 168.11,

EP

169.22. MS: M+ at m/z 399. Anal. Calcd. For C18H11ClBrN3O: C, 53.96; H, 2.77; N, 10.49. Found: C, 53.77; H, 2.94; N, 10.58.

AC C

4.5.32. 3-(4-Bromophenyl)-5-bromo-9-acetyl-pyridazino[3,4-b]indole (8c) White coloured powder; yield 89%; Mp 285-286◦C; 1H NMR (300 MHZ, DMSO-d6): δ = 8.36 (s, 1H), 8.15-8.18 (m, 3H), 8.06-8.09 (m, 1H), 7.74 (d, J = 8.4 Hz, 1H), 7.67 (d, J = 8.4 Hz, 2H), 1.85 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 19.99, 116.77, 118.23, 123.81, 124.62, 125.97, 127.63, 128.72, 129.84, 131.42, 131.97, 137.78, 141.94, 147.27, 155.55, 165.76, 167.12, 168.22. MS: M+ at m/z 443. Anal. Calcd. For C18H11Br2N3O: C, 48.57; H, 2.49; N, 9.44. Found: C, 48.76; H, 2.59; N, 9.22.

17

ACCEPTED MANUSCRIPT

4.5.33. 3-(4-Nitrophenyl)-5-bromo-9-acetyl-pyridazino[3,4-b]indole (9c) Yellowish powder; yield 85%; Mp 268-269◦C; 1H NMR (300 MHz, DMSO-d6); δ = 8.62-8.68 (d, J = 8.4 Hz, 2H), 8.42-8.48 (m, 2H), 8.32 (m, 2H), 8.15 (d, J = 8.4 Hz, 2H), 2.03 (s, 3H).

13

C NMR (DMSO-d6,

125 MHz, δ, TMS = 0): 21.01, 117.72, 119.48, 123.43, 124.79, 125.76, 128.17, 129.51, 130.43,

RI PT

131.82, 142.57, 144.85, 148.71, 148.96, 153.59, 165.69, 168.79, 169.03. MS: M+ at m/z 410. Anal. Calcd. For C18H11BrN4O3: C, 52.57; H, 2.70; N, 13.62. Found: C, 52.81; H, 2.89; N, 13.39. 4.5.34. 3-Phenyl-5-iodo-9-acetyl-pyridazino[3,4-b]indole (1d) Pale yellow fluffy powder; yield 90%; Mp 264-265◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.29 (d, J = 8.4 Hz, 1H), 8.00-8.10

SC

(m, 3H), 7.76-7.89 (m, 3H), 7.59 (m, 1H), 7.23 (m, 1H), 2.05 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.78, 93.33, 118.33, 125.50, 127.58, 128.99, 130.12, 131.59, 134.43,

M AN U

138.37, 138.70, 139.40, 147.44, 156.81, 165.59, 168.46. MS: M+ at m/z 413. Anal. Calcd. For C18H12IN3O: C, 52.32; H, 2.93; N, 10.17. Found: C, 52.43; H, 3.03; N, 10.02. 4.5.35. 3-(3,4,5-Trimethoxyphenyl)-5-iodo-9-acetyl-pyridazino[3,4-b]indole (2d) Pale yellow fluffy powder; yield 90%; Mp > 300◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.48 (s, 1H), 8.268.38 (m, 2H), 7.84 (d, J = 9.3 Hz, 1H), 7.57 (s, 2H), 3.93 (s, 6H), 3.72 (s, 3H), 2.04 (s, 3H). 13C

TE D

NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.26, 55.84, 59.28, 93.47, 109.12, 119.41, 124.42, 131.16, 131.83, 133.25, 139.91, 146.78, 153.65, 155.81, 165.93, 169.39. MS: M+ at m/z 503. Anal. Calcd. For C21H18IN3O4: C, 50.12; H, 3.60; N, 8.35. Found: C, 49.98; H, 3.78; N, 8.44. 4.5.36. 3-(3,4-Dimethoxyphenyl)-5-iodo-9-acetyl-pyridazino[3,4-b]indole (3d) Light yellow

EP

solid; yield 75%; Mp 288-289◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.74 (s, 1H), 8.15 (s, 1H), 8.07 (d, J = 9.00 Hz, 1H), 7.87-7.90 (m, 3H), 7.14 (d, J = 8.4 Hz, 1H), 3.91 (s, 3H), 3.85 (s, 3H),

AC C

2.04 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.21, 55.83, 93.78, 110.42, 114.56, 118.48, 121.20, 123.73, 125.69, 127.43, 129.10, 130.97, 131.44, 141.64, 147.67, 149.85, 151.13, 155.45, 165.63, 169.28. MS: M+ at m/z 473. Anal. Calcd. For C20H16IN3O3: C, 50.76; H, 3.41;, 8.88. Found: C, 50.67; H, 3.55; N, 8.99. 4.5.37. 3-(4-Methoxyphenyl)-5-iodo-9-acetyl-pyridazino[3,4-b]indole (4d) Cream colored solid; yield 78%; Mp 281-282◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.58 (s, 1H), 8.35-8.38 (m, 4H), 8.25 (s, 1H), 7.12 (d, J = 7.8 Hz, 2H), 3.85 (s, 3H), 1.99 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, 18

ACCEPTED MANUSCRIPT

δ, TMS = 0): 21.03, 56.76, 93.38, 115.85, 118.23, 123.67, 125.83, 127.21, 128.56, 129.48, 129.89, 130.46, 130.88, 141.93, 147.31, 155.57, 161.33, 165.80, 167.66, 169.82. MS: M+ at m/z 443. Anal. Calcd. For C19H14IN3O2: C, 51.49; H, 3.18; N, 9.48. Found: C, 51.66; H, 3.04; N,

RI PT

9.58. 4.5.38. 3-Naphth-2-yl-5-iodo-9-acetyl-pyridazino[3,4-b]indole (5d) Creamish white solid; yield 70%; Mp > 300◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.67 (s, 1H), 8.01-8.12 (m, 5H), 7.747.75 (m, 2H), 7.41-7.64 (m, 3H), 2.01 (s, 3H).

13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0):

20.68, 93.12, 118.18, 123.21, 125.46, 125.97, 127.93, 127.36, 127.57, 127.86, 128.51, 129.92,

SC

129.66, 130.53, 130.99, 133.59, 134.39, 135.41, 141.97, 147.31, 155.75, 165.53, 169.70. MS: M+ at m/z 463. Anal. Calcd. For C22H14IN3O: C, 57.04; H, 3.05; N, 9.07. Found: C, 56.77; H, 2.83;

M AN U

N, 9.41.

4.5.39. 3-Naphth-1-yl-5-iodo-9-acetyl-pyridazino[3,4-b]indole (6d) Creamish white solid; yield 70%; Mp 295-296◦C; 1H NMR (300 MHz, CDCl3): δ = 8.53 (s, 1H), 8.06-8.49 (m, 4H), 7.827.99 (m, 2H), 7.43-7.82 (4H, m), 2.01 (s, 3H).

13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0):

21.03, 93.83, 122.14, 124.43, 124.79, 125.66, 125.95, 126.24, 127.93, 128.31, 128.85, 130.42,

TE D

130.65, 131.26, 132.74, 132.98, 133.96, 137.34, 141.11, 147.86, 161.22, 165.64, 169.31. MS: M+ at m/z 463. Anal. Calcd. For C22H14IN3O: C, 57.04; H, 3.05; N, 9.07. Found: C, 57.32; H, 3.31; N, 8.79.

4.5.40. 3-(4-Chlorophenyl)-5-iodo-9-acetyl-pyridazino[3,4-b]indole (7d) White solid; yield

EP

85%; Mp 287-288◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.59 (s, 1H), 8.32 (d, J = 6.9 Hz, 2H), 8.22 (s, 1H), 8.06 (d, J = 7.5 Hz, 1H), 7.96 (d, J = 7.5 Hz, 1H), 7.62 (d, J = 6.9 Hz, 2H),

AC C

1.99 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.88, 93.78, 118.91, 123.46, 125.83, 128.92, 129.05, 129.67, 131.75, 135.86, 137.23, 141.42, 147.34, 155.66, 165.76, 167.41, 169.19. MS: M+ at m/z 447. Anal. Calcd. For C18H11ClIN3O: C, 48.29; H, 2.48; N, 9.39. Found: C, 48.38; H, 2.37; N, 9.39. 4.5.41.

3-(4-Bromophenyl)-5-iodo-9-acetyl-pyridazino[3,4-b]indole

(8d)

White

coloured

powder; yield 89%; Mp > 300◦C; 1H NMR (300 MHZ, DMSO-d6): δ = 8.78 (s, 1H), 8.26 (d, J = 8.1 Hz, 2H), 8.19 (s, 1H), 8.11 (d, J = 8.4 Hz, 1H), 7.91 (d, J = 9.3 Hz, 1H), 7.78 (d, J = 8.0 Hz, 19

ACCEPTED MANUSCRIPT

2H), 2.00 (s, 3H).

13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.83, 93.47, 118.35, 123.46,

123.76, 125.48, 127.64, 129.30, 129.72, 130.32, 131.44, 137.94, 141.15, 147.77, 155.11, 165.17, 167.49, 169.85. MS: M+ at m/z 491. Anal. Calcd. For C18H11BrIN3O: C, 43.93; H, 2.25; N, 8.54.

RI PT

Found: C, 44.08; H, 2.43; N, 8.67. 4.5.42. 3-(4-Nitrophenyl)-5-iodo-9-acetyl-pyridazino[3,4-b]indole (9d) Yellowish powder; yield 85%; Mp 283-284◦C; 1H NMR (300 MHz, DMSO-d6); δ = 8.82 (d, J = 1.8 Hz, 1H), 8.57 (d, J = 8.7 Hz, 2H), 8.40 (d, J = 8.7 Hz, 2H), 8.31 (s, 1H), 8.15 (dd, J = 1.8 and 9.0 Hz, 1H), 7.95 (d, J = 13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.21, 93.66, 118.22,

SC

9.0 Hz, 1H), 2.08 (s, 3H).

124.32, 124.86, 125.69, 128.21, 129.92, 130.82, 131.13, 142.88, 144.22, 147.23, 149.61, 155.12, 165.60, 167.91, 169.90. MS: M+ at m/z 458. Anal. Calcd. For C18H11IN4O3: C, 47.18; H, 2.42; N,

M AN U

12.23. Found: C, 47.28; H, 2.49; N, 12.02.

4.5.43. 3-Phenyl-5,7-dibromo-9-acetyl-pyridazino[3,4-b]indole (1e) Pale yellow fluffy powder; yield 90%; Mp 284-285◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.61 (d, J = 1.5 Hz, 1H), 8.39 (d, J = 7.5 Hz, 2H), 8.34 (d, J = 1.8 Hz, 1H), 8.31 (s, 1H), 7.58 (bs, 3H), 2.03 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 21.01, 115.96, 117.23, 118.87, 120.13, 127.71, 128.89,

TE D

129.47, 129.96, 130.48, 138.91, 141.82, 147.92, 156.71, 165.76, 169.74. MS: M+ at m/z 443. Anal. Calcd. For C18H11Br2N3O: C, 48.57; H, 2.49; N, 9.44. Found: C, 48.39; H, 2.62; N, 9.28. 4.5.44. 3-Naphth-2-yl-5,7-dibromo-9-acetyl-pyridazino[3,4-b]indole (2e) Creamish white solid; yield 70%; Mp > 300◦C; 1H NMR (300 MHz, DMSO-d6): δ = 8.96 (s, 1H), 8.58-8.65 (m, 2H),

EP

8.50 (s, 1H), 8.43 (d, J = 2.1 Hz, 1H), 7.99-8.14 (m, 3H), 7.63 (m, 2H), 2.01 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.88, 115.68, 117.56, 119.63, 125.37, 127.83, 127.57,

AC C

127.78, 127.94, 128.18, 129.81, 129.99, 130.13, 130.79, 133.15, 134.91, 135.90, 141.97, 147.48, 156.64, 165.68, 169.25. MS: M+ at m/z 493. Anal. Calcd. For C22H13Br2N3O: C, 53.36; H, 2.65; N, 8.49. Found: C, 53.36; H, 2.65; N, 8.49. 4.5.45. 3-Naphth-1-yl-5,7-dibromo-9-acetyl-pyridazino[3,4-b]indole (3e) Creamish white solid; yield 70%; Mp > 300◦C; 1H NMR (300 MHz, CDCl3): δ = 8.96 (s, 1H), 8.58-8.64 (m, 2H), 8.438.49 (m, 2H), 8.11 (d, J = 7.8 Hz, 2H), 7.99 (d, J = 7.2 Hz, 1H), 7.61 (m, 2H), 2.00 (s, 3H).

13

C

NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 19.99, 115.44, 117.13, 119.74, 124.89, 125.63, 20

ACCEPTED MANUSCRIPT

126.81, 127.41, 128.78, 128.31, 130.86, 130.98, 131.39, 132.40, 132.48, 133.79, 137.67, 141.85, 147.16, 156.61, 165.59, 169.96. MS: M+ at m/z 493. Anal. Calcd. For C22H13Br2N3O: C, 53.36; H, 2.65; N, 8.49. Found: C, 53.36; H, 2.65; N, 8.49.

RI PT

4.5.46. 3-(4-Fluorophenyl)-5,7-dibromo-9-acetyl-pyridazino[3,4-b]indole (4e) Yellow powder; yield 92% ; Mp 298-299◦C; 1H NMR (300 MHz, DMSO-d6); δ = 8.62 (d, J = 1.8 Hz, 1H), 8.318.48 (m, 4H), 7.40-7.46 (m, 2H), 2.02 (s, 3H).

13

C NMR (DMSO-d6, 125 MHz, δ, TMS = 0):

20.92, 116.47, 116.64, 118.72, 120.52, 125.89, 126.51, 128.10, 130.34, 130.41, 134.17, 136.58,

SC

141.81, 143.71, 156.09, 163.32, 165.32, 169.16. MS: M+ at m/z 461. Anal. Calcd. For C18H10Br2FN3O: C, 46.68; H, 2.18; N, 9.07. Found: C, 46.68; H, 2.18; N, 9.07. 4.5.47. 3-(4-Bromophenyl)-5,7-dibromo-9-acetyl-pyridazino[3,4-b]indole (5e) White coloured

M AN U

powder; yield 89%; Mp > 300◦C; 1H NMR (300 MHZ, DMSO-d6): δ = 8.64 (d, J = 1.5 Hz, 1H), 8.43 (s, 1H), 8.34-8.36 (s, 3H), 7.81 (d, J = 8.4 Hz, 2H), 2.00 (s, 3H). 13C NMR (DMSO-d6, 125 MHz, δ, TMS = 0): 20.85, 115.79, 119.71, 123.93, 126.58, 127.39, 129.82, 129.44, 131.04, 131.92, 136.21, 142.45, 148.28, 155.66, 164.99, 169.15. MS: M+ at m/z 521. Anal. Calcd. For C18H10Br3N3O: C, 41.26; H, 1.92; N, 8.02. Found: C, 41.26; H, 1.92; N, 8.02.

TE D

4.6. In-vitro cytotoxic assay

In vitro cytotoxicity against four human cancer cell lines was determined using 96-well tissue culture plate. The cells were allowed to grow in carbon dioxide incubator (37°C) for 24 h. Test

EP

materials in complete growth medium (100µl) were added after 24 h of incubation to the wells containing cell suspension. The plates were further incubated for 48 h in a carbon dioxide incubator. The cell growth was stopped by gentle layering trichloroacetic acid (50%, 50 µl) on

AC C

top of the medium in all the wells. The plates were incubated at 4°C for 1 h to fix the cells attached to the bottom of the wells. The liquid of all the wells was gently pipetted out and discarded. The plates were washed five times with distilled water to remove trichloroacetic acid, growth medium low-molecular weight metabolites, serum on a mechanical stirrer. The optical density (OD) was recorded on ELISA reader at 540 nm. The cell growth was determined by subtracting the mean OD value of respective blank from the mean OD value of the experimental set. Percent growth in presence of test material was calculated considering the growth in the 21

ACCEPTED MANUSCRIPT

absence of any test material as 100%, and in turn, percent growth inhibition in presence of test material was calculated proteins, etc. and air-dried. The plates were stained with sulforhodamine B dye (0.4% in 1% acetic acid, 100 µl) for 30 min. The plates were washed five times with 1% trichloroacetic acid and then air-dried . The adsorbed dye was dissolved in Tris–HCl buffer

4.7. In-vitro tubulin polymerization assay

RI PT

(100µL, 0.01 M, pH 10.4), and the plates were gently stirred for 10 min [25].

A Cytoskeleton tubulin polymerization assay kit was purchased from Labex India. For assessing

SC

the tubulin polymerization inhibition potential, 100µM stock solution of each compound was made in molecular biology grade DMSO. Further dilutions (50 µM, 25 µM, 10 µM) of each

M AN U

compound were made by diluting the stock solution. General tubulin buffer was prepared by reconstituting the constituents (available in kit) in 10 mL distilled water. General Tubulin Buffer (1 mL) was supplemented with 10 µL of 100mM GTP solution and 10 mg Tubulin was suspended in it and mixture was stored at 4˚C until used. Before starting the experiment 96 well plate and Elisa plate reader were warmed at 37˚C as this temperature is required to achieve the proper polymerization of tubulin. Tubulin polymerization buffer was prepared by mixing

TE D

General tubulin buffer (750 µL), Tubulin glycerol buffer (250 µL) and 100mM GTP (10 µL). 10 µL General tubulin buffer was added in the wells, where first two wells were kept as control (without any test compound), and different concentrations of compounds were subsequently added in previously marked wells and plate was kept in plate reader for 2 minutes at 37˚C.

EP

Meanwhile tubulin suspension was diluted with Tubulin polymerization buffer and 100 µL of diluted tubulin was added in each well. Plate was again kept in plate reader at 37˚C for 1 hr. and

AC C

absorbance was measured at 340 nm (Lee and Timasheff, 1977). Percentage inhibition and IC50 values were calculated according to the absorbance values obtained after 1 hr. [26, 27] 4.8 Molecular modelling study The 3D coordinates of tubulin was obtained from protein data bank (PDB entry: 1sa0) [29]. The structure of 2a was drawn in ChemDraw and subjected to energy minimization in the MOPAC module, using the AM1 procedure for closed shell systems, implemented in the CS Chem3D Ultra [31]. The ligands were docked at the colchicine-binding site of tubulin using the GOLD 5.0.1. [28]. Gold performs genetic algorithm based ligand docking to optimize the conformation 22

ACCEPTED MANUSCRIPT

of ligand at the receptor binding site. It utilizes Gold Score fitness function to evaluate the various conformations of ligand at the binding site and comprises of four components: protein– ligand hydrogen bond energy, protein–ligand van der Waals (vdw) energy, ligand internal vdw energy, and ligand torsional strain energy [28]. 2a was docked 10 times and each pose was

RI PT

ranked according to its GoldScore fitness function. The conformation with highest score was selected for discussion.

Acknowledgement

SC

The authors are grateful to the DST for providing the financial support under DST Purse scheme

M AN U

necessary for the present study.

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EP

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AC C

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tethered Chalcones, Med. Chem. Res. 21 (2012) 2990-2997.

[17] B. A. Bhat, K. L. Dhar, S. C. Puri, A. K. Saxena, M. Shanmugavel, G. N. Qazi, Synthesis and biological evaluation of chalcones and their derived pyrazoles as potential cytotoxic agents,

EP

Bioorg. Med. Chem. Lett. 15 (2005) 3177-3180.

AC C

[18] Y. Chen, M. Y. Qin, J. H. Wu, L. Wang, H. Chao, L. N. Ji, A. L. Xu, Synthesis, characterization, and anticancer activity of ruthenium(II)-β-carboline complex. Eur. J. Med. Chem. 70 (2013) 120-129.

[19]

M. Zhao, L. Bi, W. Wang, C. Wang, M. Baudy-Floc’h, J. Ju, S. Peng, Synthesis and

cytotoxic activities of beta-carboline amino acid ester conjugates, Bioorg. Med. Chem. 14 (2006) 6998-7010.

25

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[20] R. Ikeda, T. Iwaki, T. Iida, T. Okabayashi, E. Nishi, M. Kurosawa, N. Sakai, T. Konakahara, 3-Benzylamino-β-carboline derivatives induce apoptosis through G2/M arrest in human carcinoma cells HeLa S-3, Eur. J. Med. Chem. 46 (2011) 636-646.

RI PT

[21] J. Y. Tsai, Y. C. Lin, M. H. Hsu, S. C. Kuo, L. J. Huang, J. Kao. Synthesis and cytotoxicity of 1,6,8,9-substituted α-carboline derivatives. J. Med. Sci. 26 (2010) 593-602.

[22] J. Wieczorek, W. Peczyńska-Czoch, M. Mordarski, L. Kaczmarek, P. Nantka-Namirski,

SC

Antineoplastic activity of azacarbazoles. I. Synthesis and antitumor properties of alpha-carboline

M AN U

and its selected derivatives, Arch. Immunol. Ther. Exp. (Warsz). 34 (1986) 315-21.

[23] E. Meyer, M. H. Sarragiotto, Synthesis and Evaluation of New β-Carboline-3-(4benzylidene)-4H-oxazol-5-one Derivatives as Antitumor Agents, Molecules. 17 (2012) 61006113.

[24] S. Ahmed, P. G. Goekjian, D. Gueyrard, F. Popowycz, B. Joseph, C. Schneider, P. Garcia,

TE D

P. C. Gambacorti, L. Mologni, Alpha-carboline inhibitors of NMP-ALK, RET and Bcr-Abl, European Patent Application. EP 2161271 A1.

[25] a) A. Monks, A. D. Scudiero, P. Skehan, R. Shoemaker, K. Paull, D. Vistica, C. Hose, J. Langley, P. Cronise, A. Vaigro-Wolff, M. Gray-Goodrich, H. Campbell, J. Mayo, M.

EP

Boyd, Feasibility of a high-flux anticancer drug screen utilizing a diverse panel of human tumor cell lines in culture, J. Natl. Cancer Inst. 83 (1991) 757-766; b) P. Skehan, R. Storeng,

AC C

D. Scudiero, A. Monks, J. Mc Mohan, D. Vistica, J. T. Warren, H. Bokesch, S. Kenney, M.R. Boyd, New colorimetric cytotoxicity assay for anticancer-drug screening, J. Natl. Cancer Inst. 82 (1990) 1107-1112.

[26] M. L. Shelanski, F. Gaskin, C. R. Cantor, Microtubule assembly in the absence of added nucleotides, Proc. Nat. Acad. Sci. 70 (1973) 765-768. [27] J. C. Lee, S. N. Timassheff, In vitro reconstitution of calf brain microtubules: effects of solution variables, Biochemistry. 16 (1977) 1754. 26

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[28] GOLD ver. 5.0.1 Cambridge Crystallographic. Data Centre, Cambridge. [29] R. B. Ravelli, B. Gigant, P. A. Curmi, I. Jourdain, S. Lachkar, A. Sobel, M. Knossow, Insight into tubulin regulation from a complex with colchicine and a stathmin-like domain, Nature. 428 (2004) 198–202.

Interactions, J. Med. Chem. 53 (2010) 5061–5084.

RI PT

[30] C. Bissantz, B. Kuhn, M. Stahl, A Medicinal Chemist’s Guide to Molecular

[31] ChemDraw Ultra 6.0 and Chem3D Ultra (2000) Cambridge Soft Corporation,

SC

Cambridge.

M AN U

Captions Fig. 1 Design strategy Fig. 2 Retrosynthetic route

Scheme 1: a) 5% NaOH, ethanol, stirring, rt, 2 hr b) a drop of H2SO4, CH3COOH, reflux, 1 hr; c) NH2NH2.H2O, methanol, reflux, 1 hr d) (CH3CO)2O, DMAP, stirring, 2 hr e) NH2.NH2.H2O, grinding, 15 min.

TE D

Fig. 3 Proton resonances of 1a

Fig. 4 Structure activity relationship

Fig. 5 Effect of compound on the microtubule network of THP-1 cells untreated (control), 1µM

EP

Paclitaxel and 5 µM 2a for 48 h. Microtubules and unassembled tubulin are shown in green. DNA, stained with 4,6-diamidino-2-phenylindole (DAPI) shown in blue.

AC C

Fig. 6 a) Importantbinding site residues around 2a (pink: polar; blue:hydrophobic); b) binding conformation of 2a (green) in tubulin Table 1 represents the structures and % age inhibition of the designed analogues Table 2 represents IC50 values of selected analogues Table 3 represents tubulin polymerization inhibitory activity of selected compounds

27

ACCEPTED MANUSCRIPT

Table 1 represents the structures and % age inhibition of the designed analogues O

O

X1 X2

N

X1

CH3

N

X2

N

N

A A

X3

X3

B

N

X1

N

X2 A

B

X3

X5 X4

X5 X4

c

O N

X2

N

A

X1

N

X2

A

B X5

X4

X3

I

AC C

EP

TE D

d

N

N

CH3

N

Br B

X5

M AN U

X3

SC

X1

O

CH3

N

CH3 N

X4

e

B

X5

X4

Cl b

a

N

RI PT

O

CH3

Br

Br

ACCEPTED MANUSCRIPT

___________________________________________________________________________________________ Percentage growth inhibition (50 µM) ___________________________________________ THP-1 (Leukemia)

COLO-205 (Colon)

HCT-116 (Colon)

A549 (Lung)

X1

X2

X3

X4

X5

1a

H

H

H

H

H

71

64

66

10

2a

H

OCH3

OCH3

OCH3

H

99

89

86

20

3a

H

OCH3

OCH3

H

H

90

82

80

12

4a

H

H

OCH3

H

H

81

75

10

Code

6a

O NN

7a

NN

13a 14a

89

N

82

81

NA

89

83

80

NA

78

68

72

12

76

69

71

10

CH3

CH3

H

H

H

51

50

49

NA

H NHCOCH3

H

H

H

49

47

48

NA

H

H

F

H

H

42

40

36

NA

H

H

Cl

H

H

39

35

35

NA

H

H

Br

H

H

25

20

24

NA

H

H

NO2

H

H

19

17

19

NA

AC C

12a

CH3

EP

S

11a

N

O

NHCOCH3 H

CH3

TE D

NN

8a

10a

N

O H N

9a

N

SC

NN

72

M AN U

O 5a

RI PT

____________________________________________________________________________

ACCEPTED MANUSCRIPT

H

H

H

H

H

50

22

29

NA

2b

H

OCH3

OCH3

OCH3

H

77

59

66

NA

3b

H

OCH3

OCH3

H

H

71

54

49

NA

4b

H

H

OCH3

H

H

60

39

36

14

NN

N

CH3

5b

68

NN

6b

N

O

7b H N

NN

N

Cl CH3

Cl CH3

Cl H

H

Cl

H

9b

H

H

Br

H

10b

H

H

NO2

H

1c

H

H

H

H

2c

H

OCH3

OCH3

3c

H

OCH3

4c

H

H

9c

40

44

18

37

16

34

12

17

05

H

15

10

NA

NA

H

14

NA

NA

NA

H

27

NA

NA

NA

OCH3

H

59

36

43

17

OCH3

H

H

51

21

23

11

OCH3

H

H

35

10

17

07

40

14

18

08

44

12

18

09

NN

N

CH3

EP NN

AC C

8c

19

19

O

7c

45

H

O

6c

53

TE D

8b

5c

65

M AN U

O

41

SC

O

RI PT

1b

N

Br CH3

Br

H

H

Cl

H

H

NA

NA

NA

NA

H

H

Br

H

H

NA

NA

NA

NA

H

H

NO2

H

H

NA

NA

NA

NA

ACCEPTED MANUSCRIPT

H

H

H

H

H

20

NA

NA

NA

2d

H

OCH3

OCH3

OCH3

H

40

24

23

19

3d

H

OCH3

OCH3

H

H

33

14

13

11

4d

H

H

OCH3

H

H

22

09

NA

NA

25

NA

NA

NA

29

NA

NA

NA

NA

NA

NA

NA

NA

NA

5d

N

O NN

6d

H

H

Cl

8d

H

H

9d

H

1e

H

I CH3

I

H

H

NA

Br

H

H

NA

H

NO2

H

H

NA

NA

NA

NA

H

H

H

H

21

NA

NA

NA

26

NA

NA

NA

24

NA

NA

NA

O N

CH3 Br

TE D

NN

2e

M AN U

7d

N

CH3

SC

O NN

RI PT

1d

Br

O

3e

NN

H

H

5e

H

H

Br

AC C

Paclitaxel (1 µM)

F

Adriamycin (1 µM)

CH3 Br

Br

H

H

NA

NA

NA

NA

H

H

NA

NA

NA

NA

_

_

_

70

71

72

66

_

EP

4e

N

____________________________________________________________________________________________

NA- Not active

ACCEPTED MANUSCRIPT

Table 2 represents IC50 values of selected analogues ______________________________________________

Code

THP-1 (Leukemia)

COLO-205 (Colon)

RI PT

IC50 (µM) _____________________________________ HCT-116 (Colon)

______________________________________ 5.75

8.11

7.77

2a

1.13

4.15

2.89

3a

2.33

5.69

4a

3.45

6.63

5a

2.41

5.76

4.44

6a

2.39

5.74

4.36

7a

4.28

7.23

6.14

8a

4.31

7.15

6.17

2b

13.44

17.00

15.70

13.79

17.24

15.81

14.88

18.24

16.89

14.01

17.59

16.22

4b

4.40 5.23

M AN U

EP

5b

TE D

3b

SC

1a

AC C

6b 14.12 18.03 15.66 _____________________________________________

ACCEPTED MANUSCRIPT

Table 3 represents tubulin polymerization inhibitory activity of selected compounds

Compound

RI PT

_______________________________________________ Inhibition of tubulin polymerization IC50 (µM) 2.41

SC

2a

5a 6a

EP

Literature values [32]

AC C

a

TE D

CA-4

4.92 8.91

M AN U

3a

8.97 1.2a

ACCEPTED MANUSCRIPT

R'

SITES FOR PLACING CONSTRAINTS

N

O R

A

1

2

3

B

R

R

A

1

R' N

N

2

3

3-CARBON BRIDGE

3-CARBON BRIDGE

R' = -COCH3

CHALCONE FRAMEWORK

B

R

MOLECULAR HYBRIDIZATION

O

R

SC

AZACARBOLINE- CHALCONE HYBRIDS AS CONSTRAINED CHALCONE ANALOGUES.

AC C

EP

TE D

M AN U

Fig. 1 Design strategy

AZACARBOLINE

RI PT

N

N N

A

B

CHALCONE FRAMEWORK

R

ACCEPTED MANUSCRIPT

R' N

O R

R

O

R' N

N

R

R

R'

O O R

RI PT

N

N

O

TARGET COMPOUNDS NH2-NH2

RETROSYNTHETIC ROUTE

AC C

EP

TE D

M AN U

Fig. 2 Retrosynthetic route

SC

ACETOPHENONE

ISATIN

R

ACCEPTED MANUSCRIPT

X2

X5

O X3

+

O

a

N H

X5

NH

OH

X3

X4

O

O

X4

X1

RI PT

X1

O

X2

1

b X5

O O

O

N

X4

X4 d X3

NH

SC

X5

CH3

O

O

X1

X2

X1

3

X2 e

O X5

N

N

N

X2

X5

c

N

O

X4

X3

TE D

X1

2

H2N

CH3

X4 X3

M AN U

X3

NH

X1 X2

1a-5e

NOT DESIRED

EP

Scheme 1: a) 5% NaOH, ethanol, stirring, rt, 2 hr b) a drop of H2SO4, CH3COOH, reflux, 1 hr; c) NH2NH2.H2O, methanol, reflux, 1 hr d) (CH3CO)2O, DMAP, stirring, 2 hr e) NH2.NH2.H2O,

AC C

grinding, 15 min.

ACCEPTED MANUSCRIPT

2.08 (s, 3H) 8.24 (d, J = 6.9 Hz, 2H) N

N

O CH3 N

7.45-7.61 (m, 3H)

7.73-7.78 (m, 2H)

8.10 (s, 1H) 8.40 (d, J = 8.4 Hz, 1H)

AC C

EP

TE D

M AN U

SC

Fig. 3 Proton Resonances of 1a

RI PT

8.13 (d, J = 8.4 Hz, 1H)

ACCEPTED MANUSCRIPT

STRUCTURE ACTIVITY RELATIONSHIP O N

N B

A

H3CO

H3CO

Ring A =

X

> H3CO

RI PT

N

=

= H3CO

>

>

> H3CO

X = NH, S

Br

Cl Ring B =

>

>

5-chloro

I >

Br

=

5-bromo

5-iodo

Br

5,7 -dibromo

M AN U

O

CH3

N H3CO H3CO OCH3

N

N

MOST POTENT COMPOUND IC50 = 1.13 µM (THP-1)

AC C

EP

TE D

Fig. 4 Structure activity relationship

DNA

α-tubulin

R

R = Nitro or halo

SC

OCH3

>

Overlay

ACCEPTED MANUSCRIPT

SC

RI PT

Untreated

M AN U

2a

EP AC C

Paclitaxel 1 µM

TE D

5 µM

Fig. 5 Effect of compound on the microtubule network of THP-1 cells untreated (control), 1µM Paclitaxel and 5 µM 2a for 48 h. Microtubules and unassembled tubulin are shown in green. DNA, stained with 4,6-diamidino-2-phenylindole (DAPI) shown in blue.

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 6 a) Important binding site residues around 2a (pink: polar; blue:hydrophobic); b) binding

AC C

EP

TE D

conformation of 2a (green) in tubulin

ACCEPTED MANUSCRIPT O H N

N

CH3 N

EP

TE D

M AN U

SC

RI PT

H NMR:

AC C

1

N

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

EP

TE D

M AN U

SC

RI PT

C NMR:

AC C

13

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT O N

N

CH3 N

S

EP

TE D

M AN U

SC

RI PT

H NMR:

AC C

1

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

EP

TE D

M AN U

SC

RI PT

C NMR:

AC C

13

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT O N

N

CH3 N

O2N

EP

TE D

M AN U

SC

RI PT

H NMR:

AC C

1

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

EP

TE D

M AN U

SC

RI PT

C NMR:

AC C

13

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT O N

N

CH3 N

H3CO Cl

EP

TE D

M AN U

SC

RI PT

H NMR:

AC C

1

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT O H3CO

N

N

CH3 N

H3CO Cl

EP

TE D

M AN U

SC

RI PT

H NMR:

AC C

1

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT O N

N

CH3 N

O2N Cl

EP

TE D

M AN U

SC

RI PT

H NMR:

AC C

1

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT