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Open AccessArticle

Synthesis and Antimicrobial Activity of 1,2-Benzothiazine Derivatives

School of Life and Medical Sciences, University of Hertfordshire, Hatfield AL10 9AB, UK
EPSRC UK National Mass Spectrometry Facility, Institute of Mass Spectrometry, Swansea University Medical School, Swansea SA2 8PP, UK
School of Science and Technology, Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8NS, UK
Authors to whom correspondence should be addressed.
Academic Editor: Derek J. McPhee
Molecules 2016, 21(7), 861;
Received: 25 April 2016 / Revised: 22 June 2016 / Accepted: 23 June 2016 / Published: 30 June 2016
(This article belongs to the Section Medicinal Chemistry)
A number of 1,2-benzothiazines have been synthesized in a three-step process. Nine chalcones 19 bearing methyl, fluoro, chloro and bromo substituents were chlorosulfonated with chlorosulfonic acid to generate the chalcone sulfonyl chlorides 1018. These were converted to the dibromo compounds 1927 through reaction with bromine in glacial acetic acid. Compounds 1927 were reacted with ammonia, methylamine, ethylamine, aniline and benzylamine to generate a library of 45 1,2-benzothiazines 2872. Compounds 2872 were evaluated for their antimicrobial activity using broth microdilution techniques against two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative bacteria (Proteus vulgaris and Salmonella typhimurium). The results demonstrated that none of the compounds showed any activity against Gram-negative bacteria P. vulgaris and S. typhimurium; however, compounds 31, 33, 38, 43, 45, 50, 53, 55, 58, 60, 63 and 68 showed activity against Gram-positive bacteria Bacillus subtilis and Staphylococcous aureus. The range of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was 25–600 µg/mL, though some of the MIC and MBC concentrations were high, indicating weak activity. Structure activity relationship studies revealed that the compounds with a hydrogen atom or an ethyl group on the nitrogen of the thiazine ring exerted antibacterial activity against Gram-positive bacteria. The results also showed that the compounds where the benzene ring of the benzoyl moiety contained a methyl group or a chlorine or bromine atom in the para position showed higher antimicrobial activity. Similar influences were identified where either a bromine or chlorine atom was in the meta position. View Full-Text
Keywords: 1,2-benzothiazines; chalcones; Bacillus subtilis; Staphylococcous aureus; Proteus vulgaris; Salmonella typhimurium 1,2-benzothiazines; chalcones; Bacillus subtilis; Staphylococcous aureus; Proteus vulgaris; Salmonella typhimurium
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MDPI and ACS Style

Patel, C.; Bassin, J.P.; Scott, M.; Flye, J.; Hunter, A.P.; Martin, L.; Goyal, M. Synthesis and Antimicrobial Activity of 1,2-Benzothiazine Derivatives. Molecules 2016, 21, 861.

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