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List of Publications

� Shailja Singh, Manvendra K. Singh, Firasat Hussain, Alka Agarwal, Satish Kumar Awasthi, 1-(4’-aminophenyl)-3-(2,4-dichlorophenyl)-propenone, Acta Crystallographica, E67 (2011)01616-01617.

� Shailja Singh, Manvendra K. Singh, Alka Agarwal, Satish Kumar Awasthi, 2-(4-chloro-phenyl)-chromen-4-one, Acta Crystallographica, E67 (2011) 3163.

� Sandeep Kumar Dixit, Nidhi Mishra, Manish, Shailja Singh, Alka Agarwal, S. K. Awasthi. Synthesis and in vitro antiplasmodial activities of fluoroquinolone analogs, European Journal of Medicinal Chemistry, 51, (2012) 52-59.

� Neesha Yadav, Shailja Singh, Sandeep Kumar Dixit, Satish Kumar Awasthi, Structure elucidation and photochromic studies of 7-(prop-2-yn-1-yloxy)-2H-chromen-2-one, 2012 (communicated).

� Meenakshi Pandey, Shailja Singh, Satish K. Awasthi, Interaction studies of naturally occurring flavonoids with bovine serum albumin, 2013. (communicated)

� Shailja Singh, Satish K. Awasthi, Interaction mode of 4-aminoquinoline derivatives with calf thymus DNA, 2013. (communicated)

� Shailja Singh, Satish K. Awasthi, A steady-state fluorescence and circular dichroism study on the binding of (7-chloroquinolin-4-yl)-(2,5-dimethoxyphenyl)-amine hydrochloride dihydrate to bovine and human serum albumin, 2013. (communicated)

electronic reprintActa Crystallographica Section E

Structure ReportsOnline

ISSN 1600-5368

Editors: W.T.A. Harrison, J. Simpson and M.Weil

(2E)-1-(4-Aminophenyl)-3-(2,4-dichlorophenyl)prop-2-en-1-one

Shailja Singh, Manavendra K. Singh, Alka Agarwal, Firasat Hussain andSatish K. Awasthi

Acta Cryst. (2011). E67, o1616–o1617

This open-access article is distributed under the terms of the Creative Commons Attribution Licencehttp://creativecommons.org/licenses/by/2.0/uk/legalcode, which permits unrestricted use, distribution, andreproduction in any medium, provided the original authors and source are cited.

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Structure ReportsOnlineEditors: W. Clegg and D. G. Watson

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International Union of Crystallography * Chester

ISSN 1600-5368

Volume 61

Part 11

November 2005

Inorganic compounds

Metal-organic compounds

Organic compounds

Acta Crystallographica Section E: Structure Reports Online is the IUCr’s highly popu-lar open-access structural journal. It provides a simple and easily accessible publicationmechanism for the growing number of inorganic, metal-organic and organic crystal struc-ture determinations. The electronic submission, validation, refereeing and publicationfacilities of the journal ensure very rapid and high-quality publication, whilst key indica-tors and validation reports provide measures of structural reliability. The journal publishesover 4000 structures per year. The average publication time is less than one month.

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Acta Cryst. (2011). E67, o1616–o1617 Singh et al. · C15H11Cl2NO

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http://dx.doi.org/10.1107/S1600536811020460

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(2E)-1-(4-Aminophenyl)-3-(2,4-dichloro-phenyl)prop-2-en-1-one

Shailja Singh,a Manavendra K. Singh,b Alka Agarwal,b

Firasat Hussainc and Satish K. Awasthia*

aChemical Biology Laboratory, Department of Chemistry, University of Delhi, Delhi

110 007, India, bDepartment of Medicinal Chemistry, Institute of Medical Sciences,

Banaras Hindu University, Varanasi 225 001, Uttar Pradesh, India, andcNanoscience and Nanotechnology, Department of Chemistry, University of Delhi,

Delhi 110 007, India

Correspondence e-mail: [email protected]

Received 22 April 2011; accepted 28 May 2011

Key indicators: single-crystal X-ray study; T = 293 K; mean �(C–C) = 0.004 A;

R factor = 0.057; wR factor = 0.159; data-to-parameter ratio = 12.2.

The title compound, C15H11Cl2NO, is approximately planar

(r.m.s. deviation = 0.062 A) and contains a single C C double

bond in a trans (E) configuration. The crystal packing is

stabilized by intermolecular N—H� � �N and N—H� � �O inter-

molecular hydrogen bonding.

Related literature

For related flavonoids, see: Bargellini & Marini-Bettolo

(1940). For isoflavonoids, see: Nogradi & Szollosy (1996). For

the biological activities of chalcones, see: Go et al. (2005);

Hans et al. (2010); Trivedi et al. (2007); Nielsen et al. (2004).

For antimalarial activity, see: Mishra et al. (2008). For anti-

filarial activity, see: Awasthi, Mishra, Dixit et al. (2009). For

other chalcone crystal structures and small molecules, see: Fun

et al. (2008); Li et al. (2009); Singh et al. (2011). For the

synthesis, see: Migrdichian (1957); Awasthi, Mishra, Kumar et

al. (2009). For intermolecular N—H� � �N and N—H� � �Ohydrogen bonding, see: Fonar et al. (2001).

Experimental

Crystal data

C15H11Cl2NOMr = 292.15Monoclinic, P21=ca = 22.771 (2) Ab = 3.9889 (5) Ac = 14.7848 (18) A� = 92.401 (12)�

V = 1341.7 (3) A3

Z = 4Mo K� radiation� = 0.47 mm�1

T = 293 K0.23 � 0.11 � 0.08 mm

Data collection

Oxford Diffraction XcaliburSapphire3 diffractometer

Absorption correction: multi-scan(CrysAlis PRO; OxfordDiffraction, 2009)Tmin = 0.597, Tmax = 1.000

5765 measured reflections2625 independent reflections1733 reflections with I > 2�(I)Rint = 0.047Standard reflections: 0

Refinement

R[F 2 > 2�(F 2)] = 0.057wR(F 2) = 0.159S = 0.982625 reflections

216 parametersAll H-atom parameters refined��max = 0.33 e A�3

��min = �0.29 e A�3

Table 1Hydrogen-bond geometry (A, �).

D—H� � �A D—H H� � �A D� � �A D—H� � �A

N1—H1N1� � �O1i 0.78 (3) 2.210 2.977 (4) 171 (3)N1—H2N1� � �N1ii 0.76 (4) 2.469 3.134 (5) 147 (4)

Symmetry codes: (i) x;�y � 12; z þ 1

2; (ii) �x þ 1; y � 12;�z þ 1

2.

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell

refinement: CrysAlis PRO; data reduction: CrysAlis PRO;

program(s) used to solve structure: SHELXS97 (Sheldrick, 2008);

program(s) used to refine structure: SHELXL97 (Sheldrick, 2008);

molecular graphics: Mercury (Macrae et al., 2006); software used to

prepare material for publication: publCIF (Westrip, 2010).

SKA is thankful to the University Grants Commission

(UGC) [scheme F. No. 37-410/2009(SR)] and the University of

Delhi, India, for financial assistance. The authors are highly

thankful to the University Sophisticated Instrument Center

(USIC), University of Delhi, India, for providing the single-

crystal X-ray diffractometer facility.

Supplementary data and figures for this paper are available from theIUCr electronic archives (Reference: ZJ2011).

References

Awasthi, S. K., Mishra, N., Dixit, S. K., Singh, A., Yadav, M., Yadav, S. S. &Rathaur, S. (2009). Am. J. Trop. Med. Hyg. 80, 764–768.

Awasthi, S. K., Mishra, N., Kumar, B., Sharma, M., Bhattacharya, A., Mishra,L. C. & Bhasin, V. K. (2009). Med. Chem. Res. 18, 407–420.

Bargellini, G. & Marini-Bettolo, G. B. (1940). Gazz. Chim. Ital. 70, 170–178.Fonar, M. S., Simonov, Yu. A., Kravtsov, V. H., Lipkowski, J., Javolowski, A. A.

& Ganin, E. V. (2001). J. Struct. Chem. 42, 459–469.Fun, H.-K., Patil, P. S., Dharmaprakash, S. M. & Chantrapromma, S. (2008).

Acta Cryst. E64, o1464.Go, M. L., Wu, X. & Liu, X. L. (2005). Curr. Med. Chem. 12, 483–499.Hans, R. H., Guantai, E. M., Lategan, C., Smith, P. J., Wan, B., Franzblau, S. G.,

Gut, J., Rosenthal, P. J. & Chibale, K. (2010). Bioorg. Med. Chem. Lett. 20,942–944.

Li, H., Kamath, K. P., Narayana, B., Yathirajan, H. S. & Harrison, W. T. A.(2009). Acta Cryst. E65, o1915.

Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor,R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453–457.

Migrdichian, V. (1957). Organic Synthesis, Vol. 1, pp.171–173. New York:Reinhold Publishing Co.

Mishra, N., Arora, P., Kumar, B., Mishra, L. C., Bhattacharya, A., Awasthi, S. K.& Bhasin, V. K. (2008). Eur. J. Med. Chem. 43, 1530–1535.

Nielsen, S. F., Bosen, T., Larsen, M., Schonning, K. & Kromann, H. (2004).Bioorg. Med. Chem. 12, 3047–3054.

Nogradi, M. & Szollosy, A. (1996). Liebigs Ann. Chem. 10, 1651–1652.

organic compounds

o1616 Singh et al. doi:10.1107/S1600536811020460 Acta Cryst. (2011). E67, o1616–o1617



ISSN 1600-5368

electronic reprint

Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton,Oxfordshire, England.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.Singh, M. K., Agarwal, A., Mahawar, C. & Awasthi, S. K. (2011). Acta Cryst.

E67, o1382.

Trivedi, J. C., Bariwal, J. B., Upadhyay, K. D., Naliapara, Y. T., Soshi, S. K.,Pannecouque, C. C., De Clercq, E. & Shah, A. K. (2007). Tetrahedron Lett.48, 8472–8474.

Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.

organic compounds

Acta Cryst. (2011). E67, o1616–o1617 Singh et al. � C15H11Cl2NO o1617electronic reprint

electronic reprint

2-(4-Chlorophenyl)chromen-4-one

Shailja Singh,a Manavendra K. Singh,b Alka Agarwalb and

Satish K. Awasthia*

aChemical Biology Laboratory, Department of Chemistry, University of Delhi 110

007, India, and bDepartment of Medicinal Chemistry, Institute of Medical Sciences,

Banaras Hindu University, Varanasi 225 001 UP, India

Correspondence e-mail: [email protected]

Received 16 August 2011; accepted 21 October 2011

Key indicators: single-crystal X-ray study; T = 293 K; mean �(C–C) = 0.003 A;

R factor = 0.049; wR factor = 0.119; data-to-parameter ratio = 13.8.

The title compound, C15H9ClO2, is a synthetic flavonoid

obtained by the cyclization of 3-(4-chlorophenyl)-1-(2-hy-

droxyphenyl)prop-2-en-1-one. The 4-chlorophenyl ring is

twisted at an angle of 11.54� with respect to the chromen-4-

one skeleton. In the crystal, pairs of molecules are inter-

connected by weak Cl� � �Cl interactions [3.3089 (10) A]

forming dimmers which are further peripherally connected

through intermolecular C—H� � �O hydrogen bonds.

Related literature

For general features and crystal structures of flavanoids, see:

Tim Cushnie & Lamb (2005); Wera et al. (2011). For crystal

structures of small molecules, see: Singh, Agarwal & Awasthi

(2011); Singh, Singh et al. (2011). For the synthesis, see:

Migrdichian (1957); Awasthi et al. (2009); Shah et al. (1955).

For intermolecular interactions and bond lengths and angles,

see: Reddy et al. (2006); Wang et al. (2010); Desiraju & Steiner

(1999); Waller et al. (2003); Allen et al. (1987).

Experimental

Crystal data

C15H9ClO2

Mr = 256.67Monoclinic, C2=ca = 22.1564 (16) Ab = 3.8745 (2) Ac = 26.7728 (18) A� = 95.524 (6)�

V = 2287.6 (3) A3

Z = 8Mo K� radiation� = 0.32 mm�1

T = 293 K0.40 � 0.39 � 0.38 mm

Data collection

Oxford Xcalibur Eos diffractometerAbsorption correction: multi-scan

(CrysAlis PRO; OxfordDiffraction, 2009)Tmin = 0.938, Tmax = 0.941

8152 measured reflections2249 independent reflections1910 reflections with I > 2�(I)Rint = 0.037Standard reflections: 0

Refinement

R[F 2 > 2�(F 2)] = 0.049wR(F 2) = 0.119S = 1.102249 reflections

163 parametersH-atom parameters constrained��max = 0.20 e A�3

��min = �0.24 e A�3

Table 1Hydrogen-bond geometry (A, �).

D—H� � �A D—H H� � �A D� � �A D—H� � �A

C11—H11� � �O2i 0.93 2.64 3.345 (3) 134 (1)

Symmetry code: (i) �x þ 1; y � 1;�z þ 12.

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell

refinement: CrysAlis PRO; data reduction: CrysAlis PRO;

program(s) used to solve structure: SHELXS97 (Sheldrick, 2008);

program(s) used to refine structure: SHELXL97 (Sheldrick, 2008);

molecular graphics: Mercury (Macrae et al., 2008); software used to

prepare material for publication: publCIF (Westrip, 2010).

SKA is grateful to the Department of Science and Tech-

nology (Scheme No. SR/SO BB-65/2003 ) and the University

of Delhi, India, for financial assistance. The authors are very

grateful to the University Sophisticated Instrument Center

(USIC), University of Delhi, India, for providing the single-

crystal X-ray diffractometer facility.

Supplementary data and figures for this paper are available from theIUCr electronic archives (Reference: ZJ2023).

References

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor,R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.

Awasthi, S. K., Mishra, N., Kumar, B., Sharma, M., Bhattacharya, A., Mishra,L. C. & Bhasin, V. K. (2009). Med. Chem. Res. 18, 407–420.

Desiraju, G. R. & Steiner, T. (1999). In The Weak Hydrogen Bond in StructuralChemistry and Biology. Oxford University Press.

Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P.,Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood,P. A. (2008). J. Appl. Cryst. 41, 466–470.

Migrdichian, V. (1957). Organic Synthesis, Vol. 1, pp. 171–173. New York:Reinhold Publishing.

Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton,Oxfordshire, England.

Reddy, C. M., Kirchner, M. T., Gundakaram, R. C., Padmanabhan, K. A. &Desiraju, G. R. (2006). Chem. Eur. J. 12, 2222–2234.

Shah, D. N., Parikh, S. K. & Shah, N. M. (1955). J. Am. Chem. Soc. 77, 2223–2224.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.Singh, M. K., Agarwal, A. & Awasthi, S. K. (2011). Acta Cryst. E67, o1137.Singh, S., Singh, M. K., Agarwal, A., Hussain, F. & Awasthi, S. K. (2011). Acta

Cryst. E67, o1616–o1617.Tim Cushnie, T. P. & Lamb, A. J. (2005). Int. J. Antimicrob. Agents, 26, 343–

356.Waller, M. P., Hibbs, D. E., Overgaard, J., Hanrahan, J. R. & Hambley, T. W.

(2003). Acta Cryst. E59, o767–o768.Wang, Y., Wan, C.-Q., Zheng, T. & Cao, S.-L. (2010). Acta Cryst. E66, o2858.Wera, M., Serdiuk, I. E., Roshal, A. D. & Błazejowski, J. (2011). Acta Cryst.

E67, o440.Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.

organic compounds

Acta Cryst. (2011). E67, o3163 doi:10.1107/S1600536811043832 Singh et al. o3163



ISSN 1600-5368

http://scripts.iucr.org/cgi-bin/cr.cgi?rm=pdfbb&cnor=zj2023&bbid=BB1





























supplementary materials


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Acta Cryst. (2011). E67, o3163 [ doi:10.1107/S1600536811043832 ]


S. Singh, M. K. Singh, A. Agarwal and S. K. Awasthi

Comment

The term flavonoid generally includes a group of natural products containing a C6—C3—C6 carbon skeleton or morespecifically phenylbenzopyran functionality in the molecule. Flavones (flavus = yellow), a class of the flavonoids mainlyfound in cereals and herbs. Flavanoids exhibit a wide range of biological activities such as antibacterial, anti-inflammatory,antioxidants, antifungal, antitumour and antimalarial (Tim Cushnie & Lamb 2005). Recently, few flavanoids have also beencharacterized in solid state (Wera et al., 2011). Continuing our ongoing work on antimalarials (Awasthi et al., 2009) andcrystal structure of small molecules (Singh, Agarwal & Awasthi, 2011; Singh, Singh et al., 2011), here we wish to reportthe crystal structure of 2-(4-chlorophenyl)chromen-4-one.

In the title compound (Fig. 1),the bond lengths and bond angles are usual and are comparable with the analogues structureof 2-phenyl-4H-chromen-4-one (flavone) reported earlier (Allen et al., 1987; Waller et al., 2003). The 4-chlorophenyl ringin the molecule is twisted at an angle of 11.54° relative to the chromen-4-one skeleton confirming nearly planner structure.The centroid–centroid distance between two parallel chromone ring in the molecule is 3.87 Å. Further, it is evident fromthe crystal packing structure (Fig. 2) that 8 molecules are present in a unit cell and adjacent chromone units are parallelin a given column, thus forming a herringbone type pattern. Moreover,crystal packing in the molecule is stabilized byweaker intermolecular hydrogen bonding C11—H11—O2 [D = 3.34 (3) Å] which is very well supported by earlier findings(Desiraju & Steiner, 1999). Further, weak interaction among atoms in molecule such as Cl1—Cl1 (x, -1 + y, 1/2 - z) [3.30Å] (Reddy et al.,2006) and C8—H8—H8—C8 [2.26 Å](Wang et al., 2010) are also responsible for stability in the crystalpacking. Further, intermolecular Cl1—Cl1 short interaction forms a dimeric unit which are further peripherically links tosix other molecules through C—H—O and C—H—H—C interactions.

Experimental

The synthesis of the title compound was carried out in two steps according to the published procedure. (Migrdichian 1957;Awasthi et al., 2009). In the first step, an aqueous solution of sodium hydroxide (10% w/v, 10 ml) was added to a solutionof 2-hydroxyacetophenone (1.77 g m, 10 mmol) and 4-chlorobenzaldehyde (1.73 g m, 10 mmol) in minimum amount ofmethanol (3–5 ml) at ice cooled flask. The reaction mixture was allowed to draw closer to room temperature and stirred for18–20 h yielded a yellow solid. The completion of the reaction was monitored by thin layer chromatography. After com-pletion of the reaction, the mixture was neutralized with 10% hydrochloric acid in water. The compound was characterized

by 1H NMR, 13C NMR, FT–IR and EI–MS.

In second step, the cyclization was carried out according to published procedure (Shah et al., 1955). Briefly, 3-(4-chlorophenyl)-1-(2-hydroxyphenyl)propenone (40 mg, 0.12 mmol) & SeO2 (39 mg, 0.35 mmol) were added to dry amyl

alcohol (30 ml) and the mixture was heated in an oil bath at 140–150 °C so that the entire compound was completely dis-solved in the solvent. The reaction mixture was refluxed for 12 h and completion of the reaction was monitored by TLC.The reaction mixture was then filtered and dried in vacuum and purified by silica gel column using (Pet. ether: EtOAc, 2:3)

http://dx.doi.org/10.1107/S1600536811043832

http://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=Singh,%20S.

http://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=Singh,%20M.K.

http://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=Agarwal,%20A.

http://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=Awasthi,%20S.K.


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as eluent. The recrystalliation of an isolated compound from PE/ethylacetate to afford 2-(4-chlorophenyl)chromen-4-one

(10 mg, 20.1%) as white solid, m.p 177–178°C. Rf 0.6 (PE; EtOAc, 2:3). FT–IR νmax (KBr) cm-1: 1651 (C═O), 1606 and

1510 (C═C aromatic), 1263 (C—O); 1H NMR (300 Mz, CDCl3) p.p.m.: δ 6.63 (1H, s, H-3, pyrone ring), δ 7.32–7.48 (4H,

m, Ar-H, H'-5, H'-6, H'-7, H'-8), 7.20 (2H, dd, J = 2.4 Hz, H'-5, H'-3), 7.28 (2H, dd, J = 2.1 Hz, H'-2, H'-6), 13C NMR (300Mz, CDCl3) ppm: EI–MS: m/z 255 [M+].

For crystallization 5 mg of compound dissolved in 5 ml mixture of Petroleum ether/ethylacetate (80:20) and left forseveral days at ambient temperature which yielded fine needle shape crystals.

Refinement

All H atoms were located from Fourier map (range of C—H = 0.93 Å) allowed to refine freely.

Figures

Fig. 1. ORTEP diagram of the molecule with thermal ellipsoids drawn at 50% probabilitylevel Color code: White: C; red: O; green: Cl; white: H.

Fig. 2. Packing diagram of molecule showing centroid–centroid distance between two parallellying cromone ring and intermolecular hydrogen bonding.


Crystal data

C15H9ClO2 F(000) = 528

Mr = 256.67 Dx = 1.490 Mg m−3

Monoclinic, C2/c Mo Kα radiation, λ = 0.71073 ÅHall symbol: -C 2yc Cell parameters from 3949 reflectionsa = 22.1564 (16) Å θ = 3.1–32.6°b = 3.8745 (2) Å µ = 0.32 mm−1

c = 26.7728 (18) Å T = 293 Kβ = 95.524 (6)° Needle, colourless

V = 2287.6 (3) Å3 0.40 × 0.39 × 0.38 mmZ = 8


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Data collection

Oxford Xcalibur Eosdiffractometer 2249 independent reflections

Radiation source: fine-focus sealed tube 1910 reflections with I > 2σ(I)graphite Rint = 0.037

ω scans θmax = 26.0°, θmin = 3.4°Absorption correction: multi-scan(CrysAlis PRO; Oxford Diffraction, 2009) h = −26→26

Tmin = 0.938, Tmax = 0.941 k = −4→48152 measured reflections l = −33→33

Refinement

Refinement on F2 Primary atom site location: structure-invariant directmethods

Least-squares matrix: full Secondary atom site location: difference Fourier map

R[F2 > 2σ(F2)] = 0.049Hydrogen site location: inferred from neighbouringsites

wR(F2) = 0.119 H-atom parameters constrained

S = 1.10w = 1/[σ2(Fo

2) + (0.0483P)2 + 1.836P]where P = (Fo

2 + 2Fc2)/3

2249 reflections (Δ/σ)max = 0.009

163 parameters Δρmax = 0.20 e Å−3

0 restraints Δρmin = −0.24 e Å−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance mat-rix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlationsbetween e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment ofcell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, convention-

al R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-

factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as largeas those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

x y z Uiso*/Ueq

Cl1 0.31934 (3) 0.85487 (18) 0.02358 (2) 0.0570 (2)C9 0.53822 (9) 1.4266 (6) 0.14239 (7) 0.0337 (5)C6 0.64493 (9) 1.7175 (6) 0.18541 (7) 0.0354 (5)C10 0.48486 (9) 1.2780 (6) 0.11311 (7) 0.0337 (5)C1 0.63679 (9) 1.6341 (5) 0.13486 (7) 0.0339 (5)C13 0.38335 (9) 1.0144 (6) 0.05827 (8) 0.0397 (5)


sup-4

C15 0.48053 (10) 1.2743 (6) 0.06106 (8) 0.0400 (5)H15 0.5123 1.3606 0.0445 0.048*C8 0.54262 (10) 1.5012 (7) 0.19128 (8) 0.0461 (6)H8 0.5095 1.4573 0.2092 0.055*C5 0.70028 (10) 1.8653 (6) 0.20370 (8) 0.0428 (5)H5 0.7069 1.9248 0.2374 0.051*C2 0.68118 (10) 1.6940 (6) 0.10315 (8) 0.0431 (5)H2 0.6748 1.6370 0.0693 0.052*C14 0.42994 (10) 1.1448 (6) 0.03366 (8) 0.0436 (6)H14 0.4273 1.1455 −0.0012 0.052*C11 0.43729 (10) 1.1410 (6) 0.13715 (8) 0.0416 (5)H11 0.4397 1.1385 0.1720 0.050*C12 0.38674 (10) 1.0092 (6) 0.10974 (8) 0.0431 (5)H12 0.3551 0.9172 0.1260 0.052*C7 0.59653 (11) 1.6468 (6) 0.21751 (8) 0.0445 (6)O2 0.60167 (9) 1.7078 (6) 0.26277 (6) 0.0690 (6)C3 0.73488 (10) 1.8388 (6) 0.12232 (9) 0.0472 (6)H3 0.7651 1.8809 0.1013 0.057*C4 0.74463 (11) 1.9233 (6) 0.17286 (9) 0.0475 (6)H4 0.7814 2.0193 0.1856 0.057*O1 0.58414 (6) 1.4868 (4) 0.11337 (5) 0.0382 (4)

Atomic displacement parameters (Å2)

U11 U22 U33 U12 U13 U23

Cl1 0.0454 (4) 0.0656 (5) 0.0582 (4) −0.0157 (3) −0.0049 (3) −0.0043 (3)C9 0.0323 (10) 0.0380 (12) 0.0317 (10) 0.0045 (9) 0.0076 (8) 0.0045 (9)C6 0.0365 (11) 0.0363 (12) 0.0332 (11) 0.0054 (9) 0.0013 (9) 0.0023 (9)C10 0.0323 (11) 0.0353 (11) 0.0337 (10) 0.0045 (9) 0.0033 (8) 0.0035 (9)C1 0.0319 (10) 0.0358 (12) 0.0336 (10) 0.0005 (9) 0.0011 (8) 0.0027 (9)C13 0.0326 (11) 0.0390 (12) 0.0466 (12) −0.0030 (10) −0.0011 (9) −0.0010 (10)C15 0.0375 (11) 0.0492 (13) 0.0342 (11) −0.0041 (10) 0.0082 (9) 0.0025 (10)C8 0.0389 (12) 0.0672 (16) 0.0331 (11) −0.0059 (11) 0.0085 (9) 0.0006 (11)C5 0.0437 (12) 0.0432 (13) 0.0398 (12) 0.0003 (11) −0.0045 (10) −0.0018 (10)C2 0.0408 (12) 0.0529 (14) 0.0361 (11) −0.0015 (11) 0.0060 (9) −0.0002 (10)C14 0.0444 (13) 0.0533 (15) 0.0331 (11) −0.0050 (11) 0.0038 (10) −0.0002 (10)C11 0.0393 (12) 0.0529 (14) 0.0334 (11) −0.0009 (11) 0.0076 (9) 0.0040 (10)C12 0.0347 (11) 0.0496 (14) 0.0461 (12) −0.0054 (10) 0.0103 (10) 0.0052 (11)C7 0.0451 (13) 0.0563 (15) 0.0321 (11) 0.0007 (12) 0.0038 (9) −0.0031 (10)O2 0.0648 (12) 0.1114 (17) 0.0314 (9) −0.0159 (11) 0.0068 (8) −0.0149 (10)C3 0.0379 (12) 0.0508 (15) 0.0539 (14) −0.0036 (11) 0.0105 (10) 0.0053 (12)C4 0.0382 (12) 0.0450 (14) 0.0574 (14) −0.0045 (11) −0.0045 (11) 0.0018 (12)O1 0.0326 (7) 0.0541 (10) 0.0282 (7) −0.0041 (7) 0.0045 (6) −0.0028 (7)

Geometric parameters (Å, °)

Cl1—C13 1.733 (2) C8—C7 1.441 (3)C9—C8 1.335 (3) C8—H8 0.9300C9—O1 1.358 (2) C5—C4 1.362 (3)


sup-5

C9—C10 1.471 (3) C5—H5 0.9300C6—C1 1.386 (3) C2—C3 1.370 (3)C6—C5 1.399 (3) C2—H2 0.9300C6—C7 1.463 (3) C14—H14 0.9300C10—C15 1.388 (3) C11—C12 1.377 (3)C10—C11 1.392 (3) C11—H11 0.9300C1—O1 1.374 (2) C12—H12 0.9300C1—C2 1.379 (3) C7—O2 1.229 (3)C13—C14 1.373 (3) C3—C4 1.389 (3)C13—C12 1.373 (3) C3—H3 0.9300C15—C14 1.374 (3) C4—H4 0.9300C15—H15 0.9300

C8—C9—O1 122.4 (2) C6—C5—H5 119.5C8—C9—C10 125.9 (2) C3—C2—C1 118.9 (2)O1—C9—C10 111.72 (17) C3—C2—H2 120.5C1—C6—C5 117.7 (2) C1—C2—H2 120.5C1—C6—C7 119.74 (19) C13—C14—C15 119.4 (2)C5—C6—C7 122.57 (19) C13—C14—H14 120.3C15—C10—C11 118.6 (2) C15—C14—H14 120.3C15—C10—C9 120.89 (19) C12—C11—C10 120.5 (2)C11—C10—C9 120.54 (18) C12—C11—H11 119.7O1—C1—C2 116.05 (18) C10—C11—H11 119.7O1—C1—C6 122.07 (18) C13—C12—C11 119.5 (2)C2—C1—C6 121.9 (2) C13—C12—H12 120.2C14—C13—C12 121.1 (2) C11—C12—H12 120.2C14—C13—Cl1 119.24 (17) O2—C7—C8 123.3 (2)C12—C13—Cl1 119.70 (17) O2—C7—C6 122.7 (2)C14—C15—C10 120.9 (2) C8—C7—C6 114.01 (18)C14—C15—H15 119.5 C2—C3—C4 120.6 (2)C10—C15—H15 119.5 C2—C3—H3 119.7C9—C8—C7 122.8 (2) C4—C3—H3 119.7C9—C8—H8 118.6 C5—C4—C3 119.9 (2)C7—C8—H8 118.6 C5—C4—H4 120.1C4—C5—C6 121.0 (2) C3—C4—H4 120.1C4—C5—H5 119.5 C9—O1—C1 118.96 (15)

C8—C9—C10—C15 167.0 (2) C15—C10—C11—C12 −0.9 (3)O1—C9—C10—C15 −12.2 (3) C9—C10—C11—C12 178.5 (2)C8—C9—C10—C11 −12.3 (4) C14—C13—C12—C11 0.9 (4)O1—C9—C10—C11 168.48 (19) Cl1—C13—C12—C11 −179.02 (18)C5—C6—C1—O1 179.74 (19) C10—C11—C12—C13 −0.2 (4)C7—C6—C1—O1 0.3 (3) C9—C8—C7—O2 −178.0 (3)C5—C6—C1—C2 −0.2 (3) C9—C8—C7—C6 2.2 (4)C7—C6—C1—C2 −179.6 (2) C1—C6—C7—O2 178.3 (2)C11—C10—C15—C14 1.3 (4) C5—C6—C7—O2 −1.1 (4)C9—C10—C15—C14 −178.1 (2) C1—C6—C7—C8 −1.9 (3)O1—C9—C8—C7 −0.9 (4) C5—C6—C7—C8 178.7 (2)C10—C9—C8—C7 180.0 (2) C1—C2—C3—C4 0.2 (4)C1—C6—C5—C4 −0.3 (3) C6—C5—C4—C3 0.7 (4)


sup-6

C7—C6—C5—C4 179.1 (2) C2—C3—C4—C5 −0.7 (4)O1—C1—C2—C3 −179.7 (2) C8—C9—O1—C1 −0.9 (3)C6—C1—C2—C3 0.3 (3) C10—C9—O1—C1 178.32 (17)C12—C13—C14—C15 −0.5 (4) C2—C1—O1—C9 −178.86 (19)Cl1—C13—C14—C15 179.43 (18) C6—C1—O1—C9 1.2 (3)C10—C15—C14—C13 −0.6 (4)

Hydrogen-bond geometry (Å, °)

D—H···A D—H H···A D···A D—H···A

C11—H11···O2i 0.93 2.64 3.345 (3) 134.(1)Symmetry codes: (i) −x+1, y−1, −z+1/2.


sup-7

Fig. 1


sup-8

Fig. 2

Original article

Synthesis and in vitro antiplasmodial activities of fluoroquinolone analogs

Sandeep K. Dixit a, Nidhi Mishra a, Manish Sharma b, Shailja Singh a, Alka Agarwal c, Satish K. Awasthi a,*,V.K. Bhasin b

aChemical Biology Laboratory, Department of Chemistry, University of Delhi, Mall Road, Delhi 110007, IndiabDepartment of Zoology, University of Delhi, Delhi 110007, IndiacDepartment of Medicinal Chemistry, Institute of Medical Sciences, BHU, Varanasi, UP, India

a r t i c l e i n f o

Article history:Received 17 October 2011Received in revised form4 January 2012Accepted 3 February 2012Available online xxx

Keywords:FluoroquinolonesAntimalarial activityPlasmodium falciparumIn vitro

a b s t r a c t

Fluoroquinolone analogs were synthesized by simple alkylation followed by click chemistry and evalu-ated for their antimalarial in vitro against chloroquine sensitive strain of Plasmodium falciparum whileciprofloxacin was used as standard. Our results showed that the compound 12 was found most activewith IC50 value of 1.33 mg/mL while ciprofloxacin showed IC50 ¼ 8.81 mg/mL. Therefore, screening ofeither known or unknown quinolone/fluoroquinolone analogs are worthwhile to find more potentantimalarial drugs which might prove useful in the treatment of mild or severe malaria in human eitheralone or in combination with existing antimalarial drugs.

� 2012 Elsevier Masson SAS. All rights reserved.

1. Introduction

Malaria remains one of the forefront disease affecting approxi-mately 400e500 million people worldwide that results in nearlyone million deaths each year more especially young children andwoman [1,2]. The widely used first and second generation anti-malarial drugs such as chloroquine, quinine, pyrimethamine, etcare losing their effectiveness due to the development of drugresistance in malaria parasite [3]. In order to overcome drugresistance, constant efforts are being made by chemist to findnewer and cheaper drugs to cure malaria. At present, only arte-misinin, an extract isolated from Chinese worm wood Artemisiaannua and its semi-synthetic derivatives such as artemether,arteether, and artesunic acid, successfully treat chloroquine sensi-tive and chloroquine resistant malaria and are the only availabledrugs to treat multi-drug resistant malaria [4]. Till now, artemisininand its derivatives have not shown development of resistance inparasite so far [5]. However, the paucity of natural artemisinin andcomplex synthesis of its semi-synthetic derivatives have forcedchemists worldwide to find simple, cheap and efficient leadmolecules so as to check malaria infection, as this disease iscommon in mainly poor countries (Fig. 1). Moreover, WHO has

advocated combination therapy with artemisinin to further delaythe drug resistance in the parasites [6]. Therefore, there is an urgentneed to find new drugs that can have different mode of actionagainst parasites Plasmodium falciparum.

It is well established that certain antibiotics such as tetracycline[7], rifampin [8] clindamycin [9] erythromycin [10], chloramphen-icol [11] show antimalarial activity in vivo either alone or incombination with other more commonly used antimalarial drugs[12] (Fig. 1). Despite of slow antimalarial activity against malariaparasite, antibiotic such as doxycycline are frequently used forantimalarial prophylaxis along with more efficient antimalarialdrugs [13]. Fluoroquinolone derivatives are best known drugs totreat various infectious diseases. Some of them such as enoxacin,grepafloxacin, clinafloxacin and ciprofloxacinwere also found to beactive against chloroquine resistant strain of P. falciparum [14].However, the exact mode of action of these antibiotics on malarialparasite is still elusive [15]. Recent research on P. falciparumrevealed that parasite mitochondria is the main target of theseantibiotics [16e20]. Further, recent research findings suggest thatthese antibiotics affect the apicoplast of Plasmodium which in turnaffects the parasite viability at the second or later generation[21e24]. However, the main draw back in use is the relatively slowantimalarial action of fluoroquinolones and the enhanced activityafter prolonged contact limits their clinical application in treatingmalarial parasite. Thus, more efficient compounds arewarranted. Infact, quinolones as part of combination therapy could be used when

* Corresponding author. Tel.: þ91 11 27666646; fax: þ91 11 27666605.E-mail addresses: [email protected], [email protected]

(S.K. Awasthi).

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administered in conjunctionwith a rapidly acting antimalarial drug[25]. However, studies of antimalarial activity of quinolones arelimited to some of the well known antibiotic such as ciprofloxacin,nalidixic acid and pefloxacin, etc [26e29]. Therefore, there is stillscope to screen fluoroquinolones against malaria parasite irre-spective of their activity against bacteria to find an agent withpromising antimalarial activity. Recently, we have reported severalsynthetic molecules which showed antimalarial activities in vitro[30,31] as well as combination approach. To further extend ourwork, we synthesized fluoroquinolones having various alkyl (1e11)and substituted triazolyl (12e21) groups at position-1.

2. Chemistry

The fluoroquinolones (1e11) were synthesized by reportedprocedure [32] and is outlined in Scheme 1. Briefly, the condensationof 3-chloro-4-fluoroaniline with diethylethoxymethylene malonateester at 100 �C followed by cyclization in diphenyl ether at 250 �Cyielded 7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylicacid ethyl ester (1) in good yield. Subsequently, compound 1 wasalkylatedwithvarious alkyl halidesusingeither K2CO3 orNaH inDMFto gave the correspondingN-alkylatedproducts3e11. The compound7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acidethyl ester (1) was hydrolyzed into corresponding acid 7-chloro-6-fluoro-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (2) using 2 NNaOH solution. Further, 1,2,3-triazole compounds (12e21) weresynthesized by click chemistry [33e35] as shown in Scheme 2. Ina general approach, the compound 7-chloro-6-fluoro-4-oxo-1-(2-propynyl)-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (8)was treated with various alkyl or aryl azides in DMF/H2O (1:1, v/v)using copper sulfate pentahydrate (CuSO4.5H2O) and sodium ascor-bate to yielded 7-chloro-6-fluoro-4-oxo-1-(1-alkyl/aryl [1,2,3] tri-azol-4-ylmethyl)-quinoline-3-carboxylic acid ethyl ester (12e21). Allsynthesized compoundswere characterized by FT-IR, ESI-MS, 1H and13C NMR.

2.1. The X-ray crystal structure

The molecular structure of compound 8 was also confirmed byX-ray crystallography (Fig. 2). X-ray intensity datawere collected on

CrysAlis PRO (Oxford Diffraction, 2009) with graphite mono-chromated Mo Ka radiation (l ¼ 0.71073 Å) at 293 (2) K. Thestructure was solved by direct method using SHELXL-97 andrefined by full matrix least-squares method on F2 (SHELXL-97). Theunit cell parameters obtained for the single crystal; a¼ 4.6888(5) Å,a ¼ 90�; b ¼ 19.2740 (19) Å, b ¼ 93.960 (10)�; c ¼ 15.5464 (17) Å,g¼ 90� and volume¼ 1401.6 (3) (Å3), which clearly indicates that itexhibits monoclinic crystal system with the space group of P21/n1.The detailed structural data have been deposited with CCDC-834819. Crystallographic data collection, crystal data and therefinement details are summarized in Table 1.

3. Biological results and discussion

Quinolone scaffolds possess wide range of biological propertiesranging from cytotoxic [26], antibacterial [27] to anti-HIV [28].However, their inhibitory role against the malaria parasites has notyet been explored thoroughly except few known drugs. Keepingthese facts in mind, we designed and synthesized two series offluoroquinolone analogs. In the first series, substituted fluo-roquinolone 1was alkylated with normal and branched chain alkylgroups as well as some polar groups such aseOH,eCN andeC^CHetc. at position-1 and generated 3e11 compounds. Again, thecompound 8 containing propargyl group was used as a substrate tofurther generate small quinolone libraries of compounds 12e21 byexploiting click chemistry. Various substituted fluoroquinoloneswere tested in vitro against chloroquine sensitive 3D7 strain of P.falciparum using ciprofloxacin as a standard. The compound 2showed IC50 value 4.32 mg/mL while compounds 3 and 4 in whichposition-1 was substituted by methyl and ethyl groups respectivelyshowed very weak activity with 11.8 mg/mL and 15.2 mg/mLrespectively. Further, increase in carbon length by one more carbonsuch as propyl group suddenly enhanced antimalarial activity withIC50 4.86 mg/mL as seen in compound 5. Interestingly, furtherincrease in carbon length by one carbon atom such as in n-butyl asin compound 6 or branching of alkyl chain such as in case of iso-propyl had decreased activity slightly with IC50 6.96 mg/mL as seenin compound 7. Similar decrease in activity was also observedwhenbenzyl group was introduced at position-1 (compound 11with IC506.8 mg/mL). Interestingly, the insertion of an alkyl chain, having

O

O

CH3

NH

O

O

CH3

OH

OH

H3COOCCH3

H3C

H3C

CH N N N CH3H3CO

H3C

OH OH

OHCH3

N

O

OH

N

O

F

HNOH OH

NH2

O O

NH2

O

CH3 NCH3H3C

O

O

O

O

H

O

H

Artemisinin Tetracyclin Ciprofloxacin

Refampin

Fig. 1. Chemical structure of artemisinin, tetracycline, ciprofloxacin and refampin.

S.K. Dixit et al. / European Journal of Medicinal Chemistry xxx (2012) 1e82


polar group such as 2-hydroxyethyl (compound 9, IC50 ¼ 4.26 mg/mL), 2-cyanoethyl (compound 10, IC50 ¼ 2.56 mg/mL) and eC^CH(compound 8, IC50 ¼ 3.46 mg/mL) showed very good and enhancedactivity. These results clearly indicate that the substitution atposition-1 of fluoroquinolone scaffold with medium size alkylchain such as propyl or polar group may exhibit promising anti-malarial activity. Further, we also noticed that methyl and ethylsubstituted fluoroquinolone were found least active in this series.We presume that small carbon chain alkyl groups are not suitablefor activity. The overall activities data are tabulated in Table 2.

We further extended our work and synthesized a second seriesof fluoroquinolones by exploiting click chemistry on propargylgroup present at position-1 in compound 8 and generated tenanalogs. The activity data are given in Table 3. We observed thatcompounds with different substituent’s on position-1 of 1,2,3-triazole ring showed different activities. The compounds 13, 15,18,19, 20 and 21which bears propyl, methyl acetate, 3-chloropheyl,4-fluorophenyl, 3-chloro-4-fluorophenyl and 7-chloroquinolinylgroups showed very good activity. On the other hand, thecompound 14, 16 and 17 having 2-hydroxyethyl, benzyl, 4-chlorophenyl groups respectively found to be least active. It isinteresting to note that the presence of Cl at the position-3 of thephenyl ring appears to be significant. Thus, we can speculate thatcompounds having electron withdrawing substituents such ascyano (compound 11) and chloro (mainly at position-3 of phenylring in triazolyl series) were crucial for inhibitory activity. Further,

the substitution on position-1 of the fluoroquionolone with variousgroups markedly affects the antimalarial activity suggests that thisposition makes a specific contribution to the binding with targetedsite. Interestingly, the compound 12 in which the position-1 oftriazole ring was left unsubstituted found the most active(IC50 ¼ 1.33 mg/mL) antimalarial agent among both series, sug-gesting that hydrogen of triazole ring might be forming hydrogenbond with the target site, thus interfering with the normal functionof parasite life.

Fluoroquinolones inhibit the A subunit of DNA gyrase, anenzyme responsible for various reactions including the productionof negative superhelical twists within circular double-strandedDNA. This enzyme is commonly found in bacteria. P. falciparumcontains a functional mitochondrion which is sensitive to a wide

N

F

Cl

OCH2CH3

OO

R2N3, CuSO4.5H2O,sodium ascorbate

DMF/H2O (1/1),60 °C, 6 h8

12-21

N

F

Cl

OCH2CH3

OO

N

NN

R2

Scheme 2. Schematic representation of synthesis of N-1 triazolyl substituted fluo-roquinolone analogs.

Fig. 2. Ortep diagram of the compound 8 drawn in 30% thermal probability ellipsoidsshowing atomic numbering schemes. Only one part of the disordered component(C1B) has been shown.

NH2

CO2C2H5

CO2C2H5

C2H5O

NH

NH

O

NH

O

N

O

R1

2 N NaOH, reflux, 2 h

R1X, K2CO3,DMF, 90 oC, 10 h

21

CO2C2H5

CO2C2H5

(C6H5)2O, 250 oC, 1 h

N

O

R1

R1X, NaH,DMF, RT, 36 h

100 oC, 1.5 h

F

Cl

F

Cl

F

Cl

F

Cl

F

Cl

F

Cl

OH

OC2H5

OC2H5

OC2H5

OO

O

O

8 and 10

3-7, 9 and 11

Scheme 1. Schematic representation of synthesis of N-1 alkylated fluoroquinolone analogs.

S.K. Dixit et al. / European Journal of Medicinal Chemistry xxx (2012) 1e8 3


range of inhibitors [36]. Mitochondrial inhibitors, including theantibiotics which are specific for 70S ribosome are also lethal tomalaria parasite [37]. This is most satisfactory explanation for theinhibitory activity of fluoroquinolones against parasite. However,the exact mode of action of fluoroquinolones against malariaparasites are still elusive.

Our results are in good agreement with previously publisheddata for trovafloxacin, ciprofloxacin, pefloxacin and temafloxacintested against chloroquine sensitive and resistant strains ofP. falciparum [26e29]. Moreover, these in vitro results are encour-aging and therefore, these results could be taken as a starting pointfor further design of antimalarial compounds and also for drugcombinations. In light of the above results, it is worthwhile tofurther screening of large number of quinolones or fluo-roquinolones from known or unknown libraries for antimalarialactivity to find more potent and lead analogs.

3.1. In vitro cytotoxicity

The cytotoxicity of some of these compounds were evaluated inhuman embryonic kidney cells (HEK-293) using MTT assay and IC50values were calculated. In alkyl series, compound 2 (antimalarial

activity, 4.32 mg/mL) was found non-toxic while in triazole series,compounds 19 and 20 (antimalarial activities, 4.3 mg/mL and 3.4 mg/mL respectively) exhibited IC50 value of 63.79 mM and 41.87 mMrespectively. The compound 21(antimalarial activity 4.06 mg/mL)was found non-toxic. The most potent compound 12 withIC50 ¼ 1.33 mg/mL was found to be least toxic among screenedcompounds. In general, the compounds with better antimalarialactivity were showed negligible or very low toxicity profile. Thus,these results are further support the significance of this study.

4. Conclusion

We successfully synthesized small fluoroquinolone libraries byalkylation at position-1 by simple alkylation as well as by clickchemistry and screened against malaria parasites. The majority ofcompounds showed very good activities with IC50 ranging from1.33 mg/mL to 6.96 mg/ml as compared to ciprofloxacin (IC50 8.82 mg/mL). Out of twenty one compounds, sixteen compounds showedbetter activity than ciprofloxacin while the compound 12 showedhighest activity among all studied compounds with IC50 1.33 mg/mL.This study provides newwindow and to rethink about screening ofeither existing or new libraries of quinolone derivatives to findmore potent as well as synergistic partner in the combinationtherapy along with existing drug to cure malaria. Further,structureeactivity relationship (SAR) and mechanistic approachshould be taken into account while considering designing andscreening of compounds. More research in this direction is underprogress and results will be published in due course of times.

5. Experimental

Various chemicals and solvents used in this study werepurchased from E. Merck (India) and SigmaeAldrich chemicals.Melting points were determined by using open capillary methodand are uncorrected. 1H NMR spectral data were recorded onBrucker Avance spectrometer at 300 MHz and Jeol JNM ECX spec-trometer at 400 MHz, respectively, using TMS as an internal stan-dard. The chemical shifts values were recorded on d scale and the

Table 1Summary of crystal data of compound 8.

CCDC deposit No. 834819Identification code ShelxlEmpirical formula C15 H11 Cl F N O3

Formula weight 307.70Temperature (K) 293(2)Crystal system, space group Monoclinic, P21/n1

Unit cell dimensions a ¼ 4.6888(5) Å, a ¼ 90� .b ¼ 19.2740(19) Å, b ¼ 93.960(10)�

c ¼ 15.5464(17) Å, g ¼ 90�

Volume (Å3) 1401.6(3)Z, calculated density (Mg/m3) 4, 1.458Absorption coefficient (mm�1) 0.293F(000) 632Theta range for data collection 3.37e29.11�

h, k, l 5, 23, 19Data completeness 0.998Goodness-of-fit on F2 0.799WR2 0.1978 (2750)Extinction coefficient 0.0000(17)

Table 2Comparison of IC50 values of N-1 alkylated fluoroquinolones 1e11 withciprofloxacin.

N

F

Cl

OR

R1

OO

S. No. R R1 IC50 concentration (mg/mL � SE)

1 eCH2CH3 eH 5.81 � 0.072 eH eH 4.32 � 0.443 eCH2CH3 eCH3 11.83 � 0.674 eCH2CH3 eCH2CH3 15.20 � 0.125 eCH2CH3 e(CH2)2CH3 4.86 � 0.056 eCH2CH3 e(CH2)3CH3 6.96 � 0.157 eCH2CH3 eCH(CH3)2 6.966 � 1.0978 eCH2CH3 eCH2C^CH 3.46 � 0.609 eCH2CH3 e(CH2)2OH 4.26 � 0.409610 eCH2CH3 eCH2CN 2.56 � 0.3011 eCH2CH3 eCH2Ph 6.83 � 0.20

Table 3Comparison of IC50 values of N-1 (1-alkyl/aryl [1,2,3] triazol-4-yl-methyl) fluo-roquinolones 12e21 with ciprofloxacin.

N

F

Cl

OCH2CH3

OO

NN

N

R2

S. No. R2 IC50 concentration (mg/mL � SE)

12 eH 1.33 � 0.6713 e(CH2)2CH3 5.4 � 0.9214 e(CH2)2OH 14.33 � 0.7315 eCH2COOCH3 5.26 � 0.8716 eCH2Ph 12.2 � 0.4017 4-Chlorophenyl 13.0 � 2.0518 3-Chlorophenyl 2.73 � 0.2319 4-Fluorophenyl 4.3 � 0.5420 3-Chloro-4-fluorophenyl 3.4 � 0.7221 7-Chloroquinolinyl 4.06 � 0.19Ciprofloxacin 8.82 � 0.06



coupling constants (J) in hertz. The following abbreviations wereused in reporting spectra: s ¼ singlet, d ¼ doublet, t ¼ triplet,q ¼ quartet, m ¼ multiple. IR spectra were obtained on a PerkinElmer Fourier-transform infrared (FT-IR) Spectrophotometer(Spectrum 2000) in potassium bromide disk. ESI-MS spectra wereobtained on aWaters micromass LCTMass spectrometer. Elementalanalysis was done on Elementar GmbH VarioEl analyzer.

5.1. General procedure for the synthesis of 7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline 3-carboxylic acid ethyl ester (1)

Step (1): The synthesis of 7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline 3-carboxylic acid ethyl ester was achieved accord-ing to published procedure [32]. Briefly, 3-chloro-4-fluoroaniline(50.0mmol, 7.2g) anddiethyl ethoxymethylenemalonate (55.0mmol,11.1mL)were heated at 100 �C for 1.5 h. After this period, the reactionmixture was cooled at room temperature and ethanol formed duringreaction was removed under vacuo to yield crude product and waspurified by recrystallization with n-hexane to give correspondingmalonate ester (17.2 g). Yield: 94%; m.p. 58 �C; ESI-MS (m/z): 338[M þ Na]þ; 1H NMR (300 MHz, CDCl3): d 1.3e1.4 (m, 6H, 2CH3 ofOCH2CH3), 4.2e4.3 (m, 4H, 2CH2 of OCH2CH3), 6.9e7.2 (m, 3H, ArH),8.3 (d, 1H, Vinylic, JHeH ¼ 13 Hz), 10.9 (d, 1H, NH, JHeH ¼ 13 Hz); IR(KBr): 1722, 1658, 1622 cm�1. Elemental analysis: calcd. ForC14H15ClFNO4: C, 53.26; H, 4.79; N, 4.44: found: C, 53.27: H, 4.74: N,4.43%.

Step (2): The cyclization of malonate ester was achieved byheating diphenyl ether (50 mL) in an oil bath at 250 �C and theabove malonate ester (20 mmol, 6.3 g) was added slowly. Thereaction mixture was refluxed for 1 h with stirring, a white solidwas formed on cooling. Solid was filtered, washed with hexane andpurified through recrystallization from DMF to give 1 (4.4 g). Yield:70%; m.p.: 300 �C; ESI-MS (m/z): 292 [MþNa]þ; 1H NMR (300MHzCF3COOD): d 1.01 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 4.1 (q, 2H,CH2 of OCH2CH3, JHeH ¼ 7.5 Hz), 7.4 (d, 1H, ArH, JHeF ¼ 9 Hz), 7.8 (d,1H, ArH, JHeF ¼ 6 Hz), 8.8 (s, 1H, 2-H); IR (KBr): 3103, 1699,1618 cm�1; Elemental analysis calcd. for C12H9ClFNO3: C, 53.45; H,3.36; N, 5.19%; found: C, 53.29; H, 3.54; N, 5.08%.

5.2. 7-Chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylicacid (2)

The compound 1 (2.7 g, 10.0 mmol) was refluxed with 2 N NaOH(25.0 mL) for 2 h. The mixture was allowed to cool at roomtemperature and acidified with acetic acid. Solid was filtered,washed with water and dried under vacuum. The solid wasrecrystallized with DMF to give 2 (2.30 g).

Yield: 85%; m.p. 285 �C; ESI-MS (m/z): 283 [M þ K]þ; 1H NMR(300 MHz, DMSO-D6): d 8.03 (d, 1H, ArH, JHeF ¼ 6.6 Hz), 8.09 (d, 1H,ArH, JHeF ¼ 9.1 Hz), 8.8 (s, 1H, 2-H), 13.5 (s, 1H, NH)), 14.8 (s, 1H,COOH); IR (KBr): 3071, 2918, 1698, 1625, 1474 cm�1; Elementalanalysis calcd. for C10H5ClFNO3: C, 49.71; H, 2.09; N, 5.80%; found:C, 48.15; H, 2.65; N, 5.62%.

5.3. General procedure for the synthesis various N-1 substitutedquinolones (3e9)

A mixture of compound 1 (1.0 mmol, 0.27 g), K2CO3 (5.0 mmol,0.69 g), alkyl halide (5.0 mmol, 0.810 g), in 20 mL DMF was heatedat 90 �C. After 10e15 h, the mixture was evaporated to dryness,dissolved in water and extracted with chloroform. The combinedorganic layer was dried over Na2SO4 and evaporated to dryness. Thecrude products were purified by column chromatography usingCHCl3/MeOH (95/5) as eluent to afford corresponding N-1substituted quinolones (3e9).

5.3.1. 7-Chloro-6-fluoro-1-methyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (3)

Yield: 70%; mp. 218 �C; ESI-MS (m/z): 306 [M þ Na]þ; 1H NMR(300 MHz, CDCl3): d 1.37 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz), 3.8(s, 3H, CH3 of eNCH3), 4.3 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz),7.5 (d, 1H, ArH, JHeF ¼ 5.4 Hz), 8.1 (1H, d, ArH, JHeF ¼ 9 Hz), 8.41 (s,1H, 2-H); IR (KBr): 3069,1721,1677 cm�1; Elemental analysis: calcd.for C13H11ClFNO3: C, 55.04; H, 3.91; N, 4.94%; found: C, 54.70; H,3.93; N, 4.88%.

5.3.2. 7-Chloro-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (4)

Yield: 90%; m.p. 135 �C; ESI-MS (m/z): 320 [M þ Na]þ; 1H NMR(300MHz, CDCl3): d 1.3 (t, 3H, CH3 of NCH2CH3, JHeH¼ 7.2 Hz),1.5 (t,3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 4.2 (q, 2H, CH2 of NCH2CH3,JHeH ¼ 7.2 Hz), 4.4 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 7.54 (d,1H, ArH, JHeF ¼ 5.7 Hz), 8.2 (d, 1H, JHeF ¼ 9 Hz), 8.4 (s, 1H, 2-H); IR(KBr): 3422, 2684, 1719, 1615 cm�1; Elemental analysis: calcd. forC14H13ClFNO3: C, 56.48; H, 4.40; N, 4.70%; found: C, 53.44; H, 3.7; N,4.5%.

5.3.3. 7-Chloro-6-fluoro-4-oxo-1-propyl-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (5)

Yield: 60%; m.p. 156 �C; ESI-MS (m/z): 334 [M þ Na]þ; 1H NMR(300 MHz, CDCl3): d 1.03 (t, 3H, CH3 of NCH2CH2CH3, JHeH ¼ 7.3 Hz),1.3 (t, 3H, CH3 of CH2CH2CH3, JHeH ¼ 7 Hz), 1.8 (m, 2H, CH2 ofNCH2CH2CH3), 4.1 (t, 2H, CH2 of NCH2CH2CH3, JHeH ¼ 7.3 Hz), 4.5 (q,2H, CH2 of OCH2CH3, JHeH ¼ 7 Hz), 7.5 (d, 1H, ArH, JHeF ¼ 5.6 Hz), 8.2(d, 1H, ArH, JHeF ¼ 9 Hz), 8.4 (s, 1H, 2-H); 13C NMR (300 MHz,CDCl3 þ DMSO-d6): d 10.47, 13.93, 21.36, 55.28, 60.31, 109.90, 113.24,118.11, 126.34, 128.78, 135.12, 148.90, 153.15, 164.43, 172.20; IR (KBr):3045, 1728, 1613 cm�1; Elemental analysis: calcd. for C15H15ClFNO3:C, 57.79; H, 4.85; N, 4.49%; found: C, 57.39; H, 4.83; N, 4.43%.

5.3.4. 1-Butyl-7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (6)

Yield: 75%; m.p. 140 �C; ESI-MS (m/z): 348 [M þ Na]þ; 1H NMR(300 MHz, CDCl3): d 0.9 (t, 3H, CH3 of CH2CH2CH2CH3,JHeH¼ 7.2 Hz), 1.3 (t, 3H, CH3 of OCH2CH3, JHeH¼ 7.2 Hz), 1.8 (m, 4H,2 CH2 of CH2CH2CH2CH3), 4.1 (t, 2H, CH2 of CH2CH2CH2CH3,JHeH ¼ 7.2 Hz), 4.3 (q, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 7.52 (d, 1H,ArH, JHeF¼ 5.4 Hz), 8.2 (d,1H, ArH, JHeF¼ 9.3 Hz), 8.4 (s,1H, 2-H); IR(KBr): 2957, 1721, 1612 cm�1; Elemental analysis: calcd. forC16H17ClFNO3: C, 58.99; H, 5.26; N, 4.30%; found: C, 45.14; H, 3.68;N, 3.52%.

5.3.5. 7-Chloro-6-fluoro-1-isopropyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (7)

Yield: 50%; m.p. 128e130 �C; ESI-MS (m/z): 334 [M þ Na]þ; 1HNMR (300MHz, CDCl3): d 1.3 (t, 3H, CH3 of OCH2CH3, JHeH¼ 7.2 Hz),1.5e1.6 (d, 6H, 2 CH3 of (CH3)2CH, JHeH ¼ 7.2 Hz), 4.3 (q, 2H, CH2 ofOCH2CH3, JHeH ¼ 6.9 Hz), 4.7 (m, 1H, CH of (CH3)2CH), 7.6 (d, 1H,ArH, JHeF¼ 5.7 Hz), d 8.2 (d,1H, ArH, JHeF¼ 9 Hz), 8.6 (s, 1H, 2-H); IR(KBr): 2365, 1672, 1574 cm�1; Elemental analysis calcd. forC15H15ClFNO3: C, 57.79; H, 4.85; N, 4.95%; found: C, 62.15; H, 4.1; N,4.90%.

5.3.6. 7-Chloro-6-fluoro-4-oxo-1-(-2propynyl)-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (8)

Sodium hydride (0.2 g, 60% oil suspension) was washed with n-hexane and added to a stirred suspension of 1 (1.35 g, 5.0 mmol) inDMFand stirred at room temperature for 50min to dissolve all solidsubsequently propargyl bromide (0.53 mL, 6.0 mmol) was added toit portion wise and reaction mixture was stirred for 36 h. Thesolution was concentrated in vacuo and, dissolved in water,



extracted with chloroform (3 � 25 mL) and the combined organiclayer was dried over sodium sulfate, evaporated in vacuo to affordcrude compound (8). The crude product was purified by columnchromatography using CHCl3/MeOH (93/7) as eluent.

Yield: 75%; m.p. 216e218 �C; ESI-MS (m/z): 307 [M]þ; 1H NMR(300 MHz, DMSO-d6): d 1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz),2.7 (s, 1H, CH of CH2C^CH), 4.3 (q, 2H, CH2, of OCH2CH,JHeH ¼ 7.2 Hz), 4.9 (s, 2H, CH2 of NCH2C^CH), 7.7 (d, 1H, ArH,JHeF¼ 5.7 Hz), 8.1 (d, 1H, ArH, JHeF¼ 9 Hz), 8.6 (s, 1H, 2-H); 13C NMR(300 MHz, 300 MHz, CDCl3 þ DMSO-d6): d 13.75, 42.98, 60.10,74.67, 110.33, 112.85, 118.50, 126.11, 128.32, 134.74, 148.42, 153.16,163.87, 172.12; IR (KBr): 3065, 2987, 2928, 1719, 1613 cm�1;Elemental analysis calcd. for C14H11ClFNO3: C, 58.55; H, 3.60; N,4.55%; found: C, 58.50; H, 3.55; N, 4.50%.

5.3.7. 7-Chloro-6-fluoro-1-(2-hydroxy-ethyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (9)

Yield: 78%; m.p. 210 �C; ESI-MS (m/z): 335 [M þ Na]þ; 1H NMR(300 MHz, CDCl3): d 1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 2.0(s, 1H, eOH) 4.1e4.2 (m, 6H, 3CH2, two CH2 of CH2CH2OH and oneCH2 of OCH2CH3), 7.3 (d, 1H, ArH, JHeF ¼ 9.3 Hz), 7.4 (d, 1H, ArH,JHeF ¼ 5.7 Hz), 8.5 (s, 1H, 2-H); IR (KBr): 2928, 1721, 1614 cm�1;Elemental analysis: calcd. for C14H13ClFNO4: C, 53.60; H, 4.18; N,4.46%; found: C, 51.40; H, 4.14; N, 4.35%.

5.4. 7-Chloro-1-cyanomethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (10)

Sodium hydride (0.2 g, 60% oil suspension) was added to a stirredsuspension of 1 (1.35 g, 5.0mmol) inDMF (30mL) and stirred at roomtemperature for 50 min to dissolve all solid followed by addition ofbromo acetonitrile (0.42mL, 6.0 mmol) into it and continued stirringfor additional for 36 h. After this period, the reaction mixture wasconcentrated in vacuo, redissolved into water and extracted withchloroform (3 � 25 mL). The combined organic layer was dried onanhydrous sodium sulfate and evaporated in vacuum to give titledcompound (1.1 g). The crude product was purified by column chro-matography using CHCl3/MeOH (94/6) as eluent.

Yield: 88%; m.p. 222e224 �C; ESI-MS (m/z): 308 [M]þ; 1H NMR(400 MHz, CDCl3): d 1.0 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 3 Hz), 4.0 (q,2H, CH2 of OCH2CH3 JHeH ¼ 7 Hz), 5.2 (s, 2H, CH2 of NCH2CN), 7.6 (d,1H, ArH, JHeF¼ 4 Hz), 7.7 (d,1H, ArH, JHeF¼ 4 Hz), 8.4 (s,1H, 2-H); IR(KBr): 3048, 2117, 1672, 1654 cm�1; Elemental analysis calcd. forC14H10ClFN2O3: C, 54.47; H, 3.27; N, 9.07%.; found: C, 54.40; H, 3.2;N, 8.9%.

5.5. 1-Benzyl-7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (11)

Yield: 55%, m.p. 142 �C; ESI-MS (m/z): 384 [M þ Na]þ; 1H NMR(300 MHz, CDCl3): d 1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 4.3(d, 2H, CH2 of NCH2Ar, JHeH ¼ 6.9 Hz), 5.3 (s, 2H, CH2 of NCH2Ar),7.1e7.4 (m, 6H, ArH), 8.1 (d, 1H, ArH, JHeF ¼ 9 Hz), 8.5 (s, 1H, 2-H); IR(KBr): 3057, 2370, 1720, 1615 cm�1; Elemental analysis calcd. forC19H15ClFNO3: C, 6343; H, 4.20; N, 3.89%; found: C, 61.48; H, 4.07;N, 3.85%.

5.6. 7-Chloro-6-fluoro-4-oxo-1-(1H-[1,2,3]triazol-4-ylmethyl)-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (12)

The compound 7-chloro-6-fluoro-4-oxo-1-(2-propynyl)-1,4-dihydroquinoline-3-carboxylic acid ethyl ester 11 (0.153 g,0.5 mmol) and sodium azide (0.065 g, 1.0 mmol) was dissolved ina mixture of DMF and water (1:1, 10 mL). Sodium ascorbate (0.04 g.0.2 mmol, in 500 ml of water) was added to reaction mixture

followed by the addition of CuSO4$5H2O (0.02 g, 0.09 mmol in200 mL of water). The reactionmixturewas stirred vigorously for 6 hat 60 �C. After completion of the reaction, ice-cold water was addedin to the reaction mixture. The precipitate thus obtained wascollected by filtration andwashedwithwater. Again this precipitatewas dissolved in 3 N HCl (10 mL) and stirred for 30 min at roomtemperature, and extracted with ethyl acetate (25 mL � 3).Combined organic layer was dried over sodium sulfate and solventwas evaporated in vacuum to give compound (12).

Yield: 50%; m.p. >300 �C, ESI-MS (m/z): 350 [M]þ; 1H NMR(400 MHz, DMSO-d6): d 1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz),4.2 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz), 5.8 (s, 2H, CH2 of NCH2-triazole), 8.0 (m, 2H, ArH), 8.2 (d, 1H, ArH, JHeF ¼ 6.6 Hz), 8.9 (s, 1H,2-H); 13C NMR (300 MHz, 300 MHz, DMSO-d6): d 14.27, 47.88,60.03, 110.12, 112.34, 120.49, 125.11, 128.53, 135.99, 140.94, 150.28,152.78, 156.06, 164.20, 171.51; IR (KBr): 2982, 1718, 1612 cm�1;Elemental analysis calcd. for C15H12ClFN4O3: C, 51.37; H, 3.45; N,15.97%.; found: C, 51.32; H, 3.43; N, 15.90%.

5.7. General procedure for the synthesis of various N-(1-substituted-[1,2,3]triazol-4-ylmethyl)-1,4 substituted quinolones (13e21)

An equimolar ratio of alkyne, 7-chloro-6-fluoro-4-oxo-1-(2-propynyl)-1,4-dihydro-quinoline-3-carboxylic acid ethyl ester 11(0.153 g, 0.5 mmol) and azide, 13e21 (0.5 mmol) was dissolved ina mixture of DMF and water (1:1, 10 mL). Sodium ascorbate (0.04 g.0.2 mmol, in 500 ml of water) was added to above suspension fol-lowed by the addition of CuSO4$5H2O (0.02 g, 0.09 mmol in 200 mLof water). The reaction mixture was stirred vigorously for 6 h at60 �C. After the completion of reaction, reaction mixture wasdiluted with ice-cold water added and precipitate thus obtainedwas collected by filtration, washed with water and dried undervacuum. The crude product was purified by column chromatog-raphy using chloroform and methanol as eluent.

5.7.1. 7-Chloro-6-fluoro-4-oxo-1-(1-propyl-1H-[1,2,3]triazol-4-ylmethyl)-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (13)

Yield: 60%; m.p. >300 �C; ESI-MS (m/z): 392 [M]þ; 1H NMR(400 MHz, DMSO-d6): d 0.6e0.8 (m, 6H, 2CH3), 2.0 (m, 2H, CH2 ofNCH2CH2CH3), 3.7 (t, 2H, CH2 of CH2CH2CH3, JHeH ¼ 6 Hz), 4.6 (q,2H, CH2 of OCH2CH3, JHeH ¼ 6 Hz), 4.7 (s, 2H, CH2 of NCH2), 7.2 (s,1H, C]CH of triazole), 7.3 (d, 1H, ArH, JHeF ¼ 6 Hz), 7.5 (d, 1H, ArH,JHeF ¼ 9 Hz), 8.1 (s, 1H, 2-H); IR (KBr): 3047, 2928, 1695, 1614 cm�1;Elemental analysis: calcd. for C18H18ClFN4O3: C, 55.04; H, 4.62; N,14.26%; found: 55.01; H, 4.60; N, 14.22%.

5.7.2. 7-Chloro-6-fluoro-1-[1-(2-hydroxy-ethyl)-1H-[1,2,3]triazol-4-ylmethyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethylester (14)

Yield: 70%; m.p. 222e224 �C; ESI-MS (m/z): 394 [M]þ; 1H NMR(400 MHz, DMSO-d6): d 1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.7 Hz),2.5 (s, 1H, eOH), 3.7 (t, 2H, CH2, of NCH2CH2OH, JHeH ¼ 5.3 Hz), 4.2(q, 2H, CH2, of OCH2CH3, JHeH ¼ 7 Hz), 4.3 (t, 2H, CH2 ofNCH2CH2OH, JHeH ¼ 5 Hz), 5.7 (s, 2H, CH2 of NCH2-triazole), 8.0 (d,1H, ArH, JHeF¼ 9.4 Hz), 8.2 (s, 1H, C]CH of triazole), 8.3 (d, 1H, ArH,JHeF ¼ 6 Hz), 8.9 (s, 1H, 2-H); IR (KBr): 3047, 2924, 1678, 1610 cm�1;Elemental analysis calcd. for C14H11ClFNO3: C, 51.72; H, 4.09; N,14.19%; found: C, 51.70; H, 4.06; N, 14.16%.

5.7.3. 7-Chloro-6-fluoro-1-(1-methoxycarbonylmethyl-1H-[1,2,3]triazol-4-ylmethyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acidethyl ester (15)

Yield: 65%; m.p 222 �C; ESI-MS (m/z): 422 [M]þ; 1H NMR(400MHz, DMSO-d6): d 1.2 (t, 3H, CH3 of OCH2CH3, JHeH¼ 6 Hz), 3.9(s, 3H, CH3 of OCH3), 4.2 (q, 2H, CH2 of OCH2CH, JHeH ¼ 6 Hz), 5.1 (s,



2H, CH2 of NCH2-triazole), 5.4 (s, 2H, CH2 of NCH2COOCH3), 7.7 (s,1H, C]CH of triazole), 7.8 (d, 1H, ArH, JHeF ¼ 6 Hz), 8.2 (d, 1H, ArH,JHeF ¼ 9 Hz), 8.6 (s, 1H, 2-H); IR (KBr): 3421, 2084, 1710, 1615 cm�1;Elemental analysis: calcd. for C18H61ClFN4O5: C, 51.13; H, 3.81; N,13.25%; found: C, 51.11; H, 3.80; N, 13.23%.

5.7.4. 1-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethyl)-7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (16)

Yield: 70%; m.p. 232e234 �C; ESI-MS (m/z): 440 [M]þ; 1H NMR(400 MHz, CDCl3): d 1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.3 Hz), 4.3(q, 2H, CH2, of OCH2CH3, JHeH ¼ 6.8 Hz), 5.2 (s, 2H, CH2 of NCH2-triazole), 5.4 (s, 2H, CH2 of NCH2Ar), 7.2e7.4 (m, 6H, aromatic), 7.7(1H, d, ArH, JHeF ¼ 5.9 Hz), 8.1 (d, 1H, ArH, JHeF ¼ 9.1 Hz), 8.5 (s, 1H,2-H); IR (KBr): 2989, 1715, 1611 cm�1; Elemental analysis calcd. forC22H18ClFN4O3: C, 59.94; H, 4.12; N, 12.71%.; found: C, 59.9.; H, 4.1;N, 12.69%.

5.7.5. 7-Chloro-1-[1-(4-chloro-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acidethyl ester (17)

Yield: 70%: m.p. 274e276 �C; ESI-MS (m/z): 460 [M]þ; 1H NMR(300 MHz, DMSO-d6): d 1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz),4.2 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 5.8 (s, 2H, CH2 of NCH2-triazole), 7.6 (d, 2H, ArH, JHeH ¼ 8.7 Hz), 7.8 (d, 2H, ArH,JHeH ¼ 8.7 Hz), 8.0 (d, 1H, ArH, JHeF ¼ 9.3 Hz), 8.2 (d, 1H, ArH,JHeH¼ 5.7 Hz), 8.9 (d, 2H, ArH, JHeF¼ 15.9 Hz); IR (KBr): 3073, 2926,1725, 1615 cm�1; Elemental analysis calcd. for C21H15Cl2FN4O3: C,54.68; H, 3.28; N, 12.15%; found: 54.62; H, 3.250; N, 12.1%.

5.7.6. 7-Chloro-1-[1-(3-chlorophenyl)-1H-[1,2,3]triazol-4-ylmethyl]-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acidethyl ester (18)

Yield: 60%; m.p.>206e208 �C; ESI-MS (m/z): 460 [M]þ; 1H NMR(400 MHz, CDCl3): d 1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz), 4.2(q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz), 5.8 (s, 2H, CH2 of NCH2-triazole), 7.2 (m, 2H, ArH), 7.8 (d, 1H, ArH, JHeF ¼ 8.1 Hz), 7.9 (m, 2H,ArH), 8.2 (d, 1H, ArH, JHeF ¼ 5.7 Hz), 8.93 (s, 1H, ArH), 8.95 (s, 1H, 2-H); 13C NMR (300 MHz, 300 MHz, DMSO-d6): d 14.29, 48.01, 60.04,110.33, 112.39, 112.68, 118.76, 119.95, 120.45, 122.30, 125.19 128.68,131.59, 134.15, 136.02, 137.39, 142.97, 150.39, 152.83, 164.22, 171.57;IR (KBr): 3196, 2925, 1672, 1616 cm�1; Elemental analysis: calcd. forC21H15Cl2FN4O3: C, 54.68; H, 3.28; N, 12.15%; found: C, 54.65; H,3.20; N, 12.10%.

5.7.7. 7-Chloro-6-fluoro-1-[1-(4-fluoro-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethylester (19)

Yield: 78%; m.p. 236e238 �C; ESI-MS (m/z): 444 [M]þ; 1H NMR(400 MHz, CDCl3): d 1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz), 4.2(q, 2H, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 5.4 (s, 2H, CH2 of NCH2-triazole), 7.4 (m, 2H, ArH), 7.7 (d, 1H, ArH, JHeF ¼ 7.2 Hz), 7.8 (m, 2H,ArH), 8.0 (d,1H, ArH, JHeF¼ 8.7 Hz), 8.4 (s,1H, C]CH of triazole), 8.6(s, 1H, 2-H); IR (KBr): 3080, 2928, 1726, 1612 cm�1; Elementalanalysis: calcd. for C21H15ClF2N4O3: C, 56.7.; H, 3.40; N, 12.6%;found: 56.68; H, 3.350; N, 12.52%.

5.7.8. 7-Chloro-1-[1-(3-chloro-4-fluorophenyl)-1H-[1,2,3]triazol-4-ylmethyl]-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acidethyl ester (20)

Yield: 80%; m.p. 238e240 �C; ESI-MS (m/z): 478 [M]þ; 1H NMR(400 MHz, CDCl3): d 1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6 Hz), 4.1 (q,2H, CH2 of OCH2CH3, JHeH ¼ 7 Hz), 5.2 (s, 2H, CH2 of NCH2-triazole),7.2 (m, 3H, ArH), 7.4 (d, 1H, ArH, JHeH ¼ 5 Hz), 8.2 (d, 1H, ArH,JHeF ¼ 9 Hz), 8.3 (s, 1H, C]CH of triazole), 8.5 (s, 1H, 2-H); IR (KBr):3080, 2926, 1725, 1613 cm�1; Elemental analysis: calcd. for

C21H14Cl2F2N4O3: C, 52.63; H, 2.94; N,11.69%; found: 52.50; H, 2.90;N, 11.65%.

5.7.9. 7-Chloro-6-fluoro-4-oxo-1-(1-quinolin-4-yl-1H-[1,2,3]triazol-4-ylmethyl)-1,4-dihydro-quinoline-3-carboxylic acid ethylester (21)

Yield: 75%; m.p. 238e240 �C; ESI-MS (m/z): 511 [M]þ; 1H NMR(300 MHz, DMSO-d6): d 1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz),4.2 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz), 5.9 (s, 2H, CH2 of NCH2-triazole), 7.7e7.8 (m, 2H, ArH), 7.9 (d, 1H, ArH, JHeH¼ 9.3 Hz), 8.0 (d,1H, ArH, JHeH ¼ 9.6 Hz), 8.2 (s, 1H, 2-H), 8.3 (d, 1H, ArH,JHeH ¼ 5.7 Hz), 8.9 (d, 2H, ArH, JHeF ¼ 15.6 Hz), 9.1 (d, 1H, ArH,JHeH ¼ 4.5 Hz); IR (KBr): 3048, 2129, 1667, 1613 cm�1; Elementalanalysis calcd. for C24H16Cl2FN5O3: C, 56.26; H, 3.15; N, 13.67%;found: C, 56.24; H, 3.13; N, 13.60%.

6. MTT assay for cell viability

Various human embryonic kidney cells (HEK-293) were main-tained as monolayer at 37 �C in 5% CO2 using DMEM medium.Approximately, 4000 cells/well were seeded in 96-well plate con-taining 200 mL of medium and incubated for 24 h. The culturemediumwas replaced by fresh medium containing 1, 10, 20, 30, 50and 100 mM concentration of compounds 2, 12, 19, 20 and 21respectively and incubated for 24, 48 and 72 h. The cell viability wasdetermined by the MTT assay following the procedure described byPrice and McMillan [38]. The light absorbance was measured at570 nm wave length using a microplate reader (Infinite M200;Tecan Group Ltd., Männedorf, Switzerland).

Acknowledgement

SKA is thankful to Department of Science and Technology (DST),New Delhi, India (scheme no. SR/S0/BB-65//2003) and University ofDelhi, Delhi, India for financial support. This work was partly sup-ported to VKB by the Department of Biotechnology, Ministry ofScience and Technology, Government of India. SKA is extremelythankful to Dr Vibha Tandon, Department of Chemistry, Universityof Delhi, Delhi, India for providing cytotoxicity data.

Appendix. Supplementary material

Supplementary data related to this article can be found online atdoi:10.1016/j.ejmech.2012.02.006.

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