An efficient synthesis and biological study of substituted 8-chloro-5-methoxy/8-chloro-4H-1,4-benzothiazines, their sulp
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An efficient synthesis and biological study of substituted 8-chloro-5-methoxy/8-chloro-4H-1,4-benzothiazines, their sulphones and ribofuranosides NISHIDHA KHANDELWAL∗, ABHILASHA, NAVEEN GAUTAM and D C GAUTAM Department of Chemistry, University of Rajasthan, Jawahar LaL Nehru Marg, Jaipur 302 004, India e-mail: [email protected]; [email protected]; [email protected]; [email protected] MS received 29 December 2011; revised 29 May 2012; accepted 20 July 2012
Abstract. 8-Chloro-5-methoxy/8-chloro-4H-1,4-benzothiazines were synthesized by condensation followed by oxidative cyclisation of 2-amino-6-chloro-3-methoxy/2-amino-3-chlorobenzenethiol with β–diketones/β– ketoesters in the presence of dimethyl sulphoxide. By treating 4H-1,4-benzothiazines with 30% hydrogen peroxide in glacial acetic acid, 4H-1,4-benzothiazine-1,1-dioxides (sulphones) were synthesized. The 4H-1,4benzothiazines have also been used as a base to prepare ribofuranosides by the reaction with β–D-ribofuranose1-acetate-2,3,5-tribenzoate. All the synthesized compounds have been characterized by spectral and elemental analysis and have been examined for antimicrobial and anthelmintic activity. Keywords.
4H-1,4-benzothiazines; sulphones; ribofuranosides; antimicrobial activity; anthelmintic activity.
1. Introduction
2. Materials and methods
Six-membered heterocyclic compounds have occupied a prominent place among various classes of organic compounds for their diverse biological activities. Among a wide variety of heterocycles that have been explored developing pharmaceutically important molecules, 4H-1,4-benzothiazines, 1–8 their sulphones and rifuranosides have played an important role in medicinal chemistry. Benzothiazines possess a fold along nitrogen–sulphur axis which is one of the structural specificities responsible for pharmacological activities. 9–15 It has stimulated our interest to convert benzothiazines to sulphones to understand oxidation behaviour of 4H-1,4-benzothiazines and to investigate changes in infrared and nuclear magnetic resonance spectra caused by the conversion of sulphide linkage to sulphones. 4H-1,4-benzothiazines serve as heterocyclic base for the formation of ribofuranosides on treatment with sugar (β-D-ribofuranosyl-1-acetate2,3,5-tribenzoate). All these compounds are extensively used as sedatives, anthelmintic, antiulcer, anticancer, antibacterial, antifungal, etc. A slight change in the substitution pattern in the benzothiazine nucleus cause distinguishable difference in their biological activities. The newly synthesized compounds have been screened for antimicrobial and anthelmintic activity.
2.1 Experimental
∗ For
correspondence
All the melting points were determined in an open capillary tubes and are uncorrected. 1 H NMR and 13 C NMR spectra (by broad band proton decoupling technique) were recorded on JEOL AL-300 spectrometer at frequencies of (300.40 MHz and 75.45 MHz) respectively, in dimethylsulphoxide-d6 using TMS (tetramethyl silane) as an internal standard. IR spectra were recorded
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