Accepted Manuscript Synthesis and antimicrobial activity of novel Benzoxazine Sulfonamide Derivatives Saidulu Konda, Srujana Raparthi, K Bhaskar, Rajesh Kumar Munaganti, Vijayacharan Guguloth, Lingaiah Nagarapu, Dattatray. M. Akkewar PII: DOI: Reference:

S0960-894X(15)00038-4 http://dx.doi.org/10.1016/j.bmcl.2015.01.026 BMCL 22366

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Bioorganic & Medicinal Chemistry Letters

Received Date: Revised Date: Accepted Date:

4 September 2014 2 December 2014 13 January 2015

Please cite this article as: Konda, S., Raparthi, S., Bhaskar, K., Munaganti, R.K., Guguloth, V., Nagarapu, L., Akkewar, y.M., Synthesis and antimicrobial activity of novel Benzoxazine Sulfonamide Derivatives, Bioorganic & Medicinal Chemistry Letters (2015), doi: http://dx.doi.org/10.1016/j.bmcl.2015.01.026

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Graphical Abstract

Synthesis and antimicrobial activity of novel Benzoxazine Sulfonamide Derivatives

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Saidulu Konda, Srujana Raparthi, Bhaskar K, Rajesh Kumar Munaganti, Vijayacharan Guguloth, LingaiahNagarapu†, Dattatray. M. Akkewar*

Bioorganic & Medicinal Chemistry Letters j o u r n a l h o m e p a g e : w w w . e ls e v i e r . c o m

Synthesis and antimicrobial activity of novel Benzoxazine Sulfonamide Derivatives Saidulu Konda, Srujana Raparthi, Bhaskar K, Rajesh Kumar Munaganti, Vijayacharan Guguloth, Lingaiah Nagarapu†, Dattatray. M. Akkewar* Organic Chemistry Division-II (CPC), CSIR- Indian Institute of Chemical Technology, Hyderabad-500007,A.P, India. * Tel.: +91-40-27191443; Fax: +91-40-27193382; E-mail:[email protected], † +91-40-27191510; Fax: +91-40-27193382; E-mail:[email protected]

ARTICLE INFO

ABSTRACT

Article history: Received Revised Accepted Available online

A new series of benzoxazine-6-sulfonamide derivatives were synthesized in excellent yields and the resulting compounds were evaluated for their antimicrobial activities. All the synthesized compounds were assessed for their antibacterial and antifungal activities. Among them 1a, 1b, 1c, 1e, 1h, 2c, 2d, 2e, 2g, 2h, 2i, 2j, 2k and 2l showed low inhibitory concentration (MIC of 31.25 and 62.5 µg/mL) against Gram-positive bacteria, Gram-negative bacteria and fungi, which are comparable to the inhibitory effect of standard drugs. 2009 Elsevier Ltd. All rights reserved.

Keywords: Sulfonamide, Piperazine, Benzoxazine, Antibacterial activity, Antifungal activity.

The present treatments of bacterial and fungal infections are a bit unsatisfactory, owing to rapidly developing drug resistance and side effects. This effect has a negative impact on the usage of most antimicrobial agents.1-4 2,3-Dihydro-1,4benzoxazines have shown their significance as a part of biologically active and medicinally important compounds. It is evident by the several biological activities, such as antiinflammatory,5 antiulcer,6 antibacterial,7 shown by 1,4benzoxazin-3(4H)-one derivatives. Ofloxacin, (Fig.1) one of the antimicrobial agents, possess 1,4-benzoxazine ring system in its structure. Sulfonamides forms the basis for a large multiplicity of drugs and are known for antibacterial,8 antiviral,9 diuretic,10 antimalarial,11 anticonvulsant,12 hypoglycemic,13 anti-carbonic anhydrase14,15 and antithyroid16 activities. A marketable sulfonamide derivative, KCN1 was shown to display both in vitro and in vivo antitumor activity.17,18 Recently Walsh et al. evaluated benzoxazine-6-sulfonamides (e) as activators of the tumor cell specific M2 isoform of pyruvate kinase.19 Newly, certain benzoxazine and sulfonamides (Fig. 1), have been reported to exhibit interesting antibacterial(b&d)7,19 and anticancer activity.19 The piperazine-based heterocyclic nuclei are a varied class of chemical compounds, some of which demonstrate significant pharmacological properties. A small adjustment in the additional design in the piperazine core causes obvious distinction in their biological events. A few related arylsulfamides with a spacer to phenyl-piperazine were testified as active structure for 5-HT7 antagonist.20

Considering the importance of benzoxazine-6sulfonamide, and in continuation of our research program to discover and develop novel biologically active compounds,21-24 we have planned to synthesize a new series of compounds having benzoxazine-6-sulfonamide moiety and screened them for their antimicrobial activities. The antibacterial and antifungal activities of all the newly synthesized compounds were evaluated in vitro against one Gram-positive bacterium, three Gram-negative bacteria and one fungus. O

O

F

O N

N N

O

R

O

OH O

N O

H N S O

O O

H2N Cl Sulfadoxine (c)

antibacterial agent(b)

Ofloxacin (a)

O O F H O N S O

H N

anticancer agent (d)

O R2 R3

R1

H N

O S N H O

O

anticancer activity (e)

O

O

S N

O

KCN1 (f)

Figure1.Structure of 1,4-benzoxazine ring system and sulfonamide derivatives with antibacterial, anticancer activity.

The synthetic pathways for the preparation of the target compounds are shown in Scheme 1, 2, 3 and 4. The intermediate3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6sulfonyl chloride 5a-b was attained by the two-step synthetic route. (Scheme 1)

Treatment of substituted o-amino phenol 3a-b with chloroacetyl chloride in presence of benzyl triethyl ammonium chloride (TEBA), afforded 2H-benzo[b][1,4]oxazin-3(4H)-one 4a-b, which was further subjected to chlorosulfonylation to give compounds 5a-b (Scheme 1). The synthesisof the intermediates 10a-g was achieved as per the scheme 2. Reaction of pthalimide (6) with 1,3-dibromo propane (7) in presence of potassium carbonate, in DMF furnished 2-(3-bromopropyl)isoindoline-1,3dione (8). Treatment of 8 with various piperazines and thiomorpholine in presence of potassium carbonate in DMF, resulted in the intermediates 9a-g, which were then treated with hydrazine hydrate in MeOH to give compounds 10a-g. Coupling of compounds 5a-b with 3-(4-phenylpiperazin-1-yl) propan-1amine derivatives 10a-g using diisopropylethylamine (DIPEA) in DMF furnished benzo[b][1,4]oxazine-6-sulfonamide derivatives 1a-m (Scheme 3). The additional series 2a-n (scheme 4)were synthesized from 5b. Compound 5b was treated with piperazines in the presence of DIPEA in DMF to give compounds 11a-b. Reaction of 11a-b with various phenacyl bromides in the presence of potassium carbonate in MeOH afforded 2a-n.

Benzoxazine-6-sulfonamides 1a-n, 2a-m and 11a-b were tested in vitro for antibacterial and antifungal activity. The results obtained showed that the majority of these compounds show activity against Gram-positive bacteria such as Bacillus megaterium, Gram-negative bacteria: Xanthomonas campestris, Pseudomonas aeruginosa, Escherichia coli by broth micro dilution method.25The anti-fungal activity was performed against Candida albicans (MTCC 183) in comparison with Fluconazole by employing Sabouraud’s dextrose broth.26 According to the obtained anti-bacterial data (Table 1), it is apparent that all the benzoxazine-6-sulfonamides showed promising activity. Compounds 1b, 1c, 2d, 2g, and 2l showed low inhibitory concentration (MIC) of 31.25 (µg/mL) and 1a, 1h, 2e, 2h, 2i, and 2k MIC of 62.5 (µg/mL) and were found to be very active against B.megaterium. Among the tested compounds for antibacterial activity against Gram-negative bacteria, 1c, 1h, 2i, and 2l exhibited significant activity against X.campestris. In particular, compounds 1c, 1e, 2c, 2d, 2g and 2l showed excellent activity against P.aeruginosa. The compounds 2c, 2d, 2j, and 2l showed low inhibitory concentration (MIC of 62.5 µg/mL) against E. coli, as compared to Rifampicin (MIC of 64 µg/mL).The compounds with piperazine substituted sulfonamide moiety 11a and 11b exhibited moderate anti-bacterial activity. However attachment of the phenacyl group to them significantly enhanced the anti-bacterial activity. The existence of strong electron-donating and withdrawing substituent's, in compounds1a, 1b, 1c, 1e, 1h, 2c, 2d, 2e, 2g, 2h, 2i, 2j, 2k, and 2l showed favorable antibacterial activity. Most of the tested compounds were found to be remarkably active against C. albicans. Compounds 1b, 2d, 2g, 2i, 2j and 2l had comparable activity with the reference drug fluconazole. The structure-activity relationship (SAR) study reveals that the change in substitution on piperazine attached aromatic ring is important for inducing anti-microbial activity against particular Gram-positive bacteria, Gram-negative bacteria and fungi (Table-1). The compounds with fluoro substitution on aromatic ring had higher anti-microbial activity as compared to electron donating and strong electron withdrawing groups. For example, compounds 1a, and 1h with no substitution and 1b and 1c with fluoro substitution showed higher anti-microbial activity.

Tabale1. Results of anti-bacterial and anti-fungal activities of compounds 1a-m, 2a-n and 11a-b MICs (µg/mL). Compounds

1a 1b 1c 1d 1e 1f 1g 1h 1i 1j 1k 1l 1m 2a 2b 2c 2d 2e 2f 2g 2h 2i 2j 2k 2l 2m 2n 11a 11b Rifampicin Fluconazole

Gram positive B.megaterium 62.5 31.25 31.25 250 250 NT NT 62.5 250 250 250 NT 125 125 250 125 31.25 62.5 250 31.25 62.5 62.5 125 62.5 31.25 250 500 250 250 64 -

X.campestris 125 125 62.5 500 125 NT NT 62.5 500 250 250 NT 250 125 250 125 125 250 500 125 125 62.5 125 125 62.5 125 250 500 500 32 -

Microorganisms Gram negative P.aeruginosa 125 125 62.5 500 62.5 NT NT 250 500 250 250 NT 500 125 250 31.25 31.25 125 500 31.25 250 125 62.5 250 31.25 250 250 250 500 32 -

E.coli 500 250 125 500 500 NT NT 250 500 250 250 NT 500 250 250 62.5 62.5 250 500 125 500 125 62.5 250 62.5 250 250 500 500 64 -

Fungi C.albicans 125 62.5 125 500 250 NT NT 125 250 250 250 NT 250 125 250 250 31.25 250 500 31.25 500 62.5 62.5 250 31.25 250 250 500 500 32

NT-not tested

While the compounds with piperazine substituted sulfonamide moiety 11a and 11b exhibited moderate antimicrobial activity. However attachment of the phenacyl group to them significantly enhanced the anti-microbial activity. The presence of electron donating and withdrawing substituents (CH3, -OCH3, -NO2 and Ph) on the phenacyl group increases the activity, as indicated by the low inhibitory concentration (MIC) of 31.25 and 62.5 (µg/mL) displayed by them. Thus suggesting that substitution on phenacyl group is important for inducing anti-microbial activity. In conclusion, we have synthesized two different series of novel benzoxazine-6-sulfonamides efficiently in excellent yields. All the synthesized compounds showed significant antimicrobial activity against Gram-positive bacteria, Gramnegative bacteria and fungi. Particularly, the compounds 1a, 1b, 1c, 1e, 1h, 2c, 2d, 2e, 2g, 2h, 2i, 2j, 2k, and 2l showed low inhibitory concentration (MIC of 31.25 and 62.5 µg/mL) as compared with standard drugs, Rifampicin and Fluconazole. Acknowledgments The authors gratefully acknowledge DSTSERB/EMEQ-078/2013 for financial assistance. S Konda & B K thanks CSIR, New Delhi for award of research fellowship.

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Supplementary data Experimental and copies of the 1H, 13C NMR and ESIMS spectra for some of the important compounds.