Short communication Synthesis, structure elucidation and antibacterial evaluation of new steroidal -5-en-7-thiazoloquinoxaline derivatives Salman Ahmad Khan, Kishwar Saleem * , Zaheer Khan Department of Chemistry, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India Received 16 February 2007; received in revised form 23 September 2007; accepted 27 September 2007 Available online 4 October 2007 Abstract Some heterocyclic systems namely cholest-5-en-7-thiazolo[4,5-b]quinoxaline-2-yl-hydrazone] were synthesized by the reaction of cholest-5- en-7-one-thiosemicarbazone with 2,3-dichloroquinoxaline at 80  C in high yield. The thiosemicarbazone derivatives were obtained by the con- densation of the thiosemicarbazide with steroidal ketones. All the compounds have been characterized by means of elemental analyses, IR, 1 H NMR and mass spectroscopic data. The in vitro antibacterial activity was evaluated by disk diffusion method and then the minimum inhibitory concentration (MIC) of compounds was determined against the culture of Escherichia coli. The results were compared with the standard drug chloramphenicol. The results showed that compounds 7 and 8 are better antibacterial agents as compared to chloramphenicol. Ó 2007 Elsevier Masson SAS. All rights reserved. Keywords: Thiosemicarbazone; Thiazoloquinoxalines; Antibacterial activity 1. Introduction Diarrhea is a serious health problem; moreover drug resis- tance in diarrhea and dysentery can be attributed to the use of drug (amoxicillin, norfloxacin, ciprofloxacin and chloram- phenicol) for treatment and to the adaptation of the bacterial parasite by developing alternate pathways for survival. Hence, the present strategy for new drug development is directed to- wards developing new steroidal molecules to inhibit the growth of parasite [1,2]. The importance of heterocyclic compounds has long been recognized in the field of synthetic organic chemistry. It is well known that a number of heterocyclic compounds containing nitrogen and sulphur exhibited a wide variety of biological activities. Quinoxaline derivatives are important moieties of several pharmacologically active com- pounds [3e8]. Although rarely described in nature, synthetic quinoxaline ring is a part of a number of antibiotics such as echinomycin and actinomycin, which are known to inhibit the growth of Gram-positive bacteria and are active against var- ious transplantable tumors [9e11]. There are many examples of biologically active quinoxalines, which showed very interesting pharmacological properties such as antibacterial, antiviral, anticancer, antifungal, antihelmintic and insecticidal [12e15]. Thiazoloquinoxaline ring dramatically increases the diversity of certain biological properties such as antibacterial, antiviral and antiamoebic activities [16e19]. Recently, the compounds obtained from thiosemicarbazone have been re- ported as antibacterial, antitumor, antiviral and antimalarial agents [20e24]. Steroidal thiosemicarbazones dramatically increase the diversity of certain biological properties [25e27]. The present work is aimed towards developing novel mol- ecules with improved potential for treating bacterial infection (Escherichia coli). It is proposed to achieve this by generating a common pharmacophore from the structures of potent anti- bacterial belonging to different classes by synthesizing novel molecules and evaluating them for antibacterial activity. In this paper the steroidal thiazoloquinoxaline derivatives have been synthesized by the condensation of the steroidal thi- osemicarbazone with 2,3-dichloroquinoxaline. The activities of these compounds were screened in vitro against E. coli. * Corresponding author. Tel.: þ91 11 26981717/3253, fax: þ91 11 26980229/1232. E-mail address: kishwarsaleem2003@yahoo.co.in (K. Saleem). 0223-5234/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ejmech.2007.09.022 Available online at www.sciencedirect.com European Journal of Medicinal Chemistry 43 (2008) 2257e2261 http://www.elsevier.com/locate/ejmech