SYNTHESIS AND BIOLOGICAL EVALUATION OF SPIRO (INDOLE-THIAZOLIDINE) DERIVATIVES AS ANTIMICROBIAL AGENTS

Methods: The reaction sequence involves microwave-induced preparation of N-(2-oxo-1,2-dihydro-3’H-indol-3-ylidene)pyridine-4-carbohydrazide [3] from isoniazid [1] and isatin [2] followed by the cyclo condensation of [3] and mercaptoacetic acid under microwave condition to achieve the synthesis of spiro-[indole-thiazolidine] derivatives [4]. The resulting compounds were then allowed to react with various aromatic and heterocyclic aromatic aldehydes to afford arylidene derivatives [5a-l].


INTRODUCTION
Heterocyclic compounds containing nitrogen have been described for their biological activity against various microorganisms. Small ring heterocycles containing nitrogen, sulfur, and oxygen have been under investigation for a long time because for their important properties and also contributed to the society from the biological and industrial point are helps to understand life processes [1].
The heterocyclic compound holds a special place among pharmaceutically important natural and synthetic materials. The remarkable ability of heterocyclic nuclei to serve as reactive pharmacophores has largely contributed to their unique values as traditional key elements of numerous drugs. By far the most important heterocyclic system used in pharmaceuticals are those having five and six-membered rings. Over the past decade, chemists have reported some exciting synthetic strategies for the synthesis of this exclusive class of compounds. Consequently, there is an increased interest in technologies and concepts that facilitates more rapid synthesis and screening of chemical substance to identify compounds with appropriate qualities. One such high-speed technology is microwave Assisted Organic Synthesis [MAOS].
Spirocyclic system containing one carbon atom common to two rings are structurally interesting [2]. Spiro compounds represent an important class of naturally occurring substances and their characteristics is the highly biological properties [3,4]. 1-H-indole-2,3-dione,[isatin]derivatives possess a broad range of biological and pharmacological properties and are widely used as starting materials for the synthesis of broad range of heterocyclic compounds and substrates for drug synthesis [5]. Spiro compounds are well known to possess varied pharmacological activities [6]. Spiro pyrans are biologically interesting compounds, with antibacterial [7], antioxidant [8], antifungal [9], A microwave-assisted three-component regioselective one-pot cyclo condensation method has been developed for the synthesis of a series of novel Spiro [indole-thiazolidinones] [13], in high yields as compared to a conventional two-step procedure. A green chemical synthesis of novel Spiro [indole-pyrido-thiazines] was carried out under microwave conditions [14], which was reluctant to be formed under thermal conditions. Spiro-fused heterocycles under solvent-free conditions have also been carried out by Shaabani and Bazgir [15], Byk et al. [16]. In the present investigation, isoniazid is condensed with isatin using green pathway (i.e. microwave radiation) to synthesize some new spiro-[indole-thiazolidine] compounds.

MATERIALS AND METHODS
All chemicals were supplied by Merck and SD fine chemicals (India). All reactions were carried out in a domestic microwave oven. The melting point was taken in open capillary tube and is therefore uncorrected. The purity of the compounds was checked on silica gel G TLC plates of 2 mm thickness using ethyl acetate: n-hexane (7:3) as solvent system and was detected by iodine vapors. IR spectra (KBr pellets) were recorded on Jasco 4100 (FTIR) spectrophotometer. 1
The reaction mixture of equimolar (0.01 mole) quantities of isoniazid (1) and isatin (2) in alcohol and a catalytic amount of glacial acetic acid was heated for 3 min in a microwave oven. The mixture was then allowed to cool; yellow-colored solid separated out, which was filtered, dried and recrystallized from CH2Cl2
To a mixture of (3) (0.01 mole) and mercaptoacetic acid (0.01 mole) in DMF, a pinch of anhydrous ZnCl2 was added and the mixture was irradiated for 10 min. It was cooled to room temperature and then poured into crushed ice. The solid separated was filtered, washed and recrystallized from alcohol.

Biological activity
Antimicrobial activity [16] Beef extract, Sodium Chloride and Peptone were dissolved in 250 ml of distilled water. P H The plates were inoculated by specific microorganisms by spread plate technique and allowed to dry. Then bores were made in the solidified agar plate by using a sterile borer. The test solution and standard solution of the specified concentration were added in the bore by using sterile pipette. The plates were then kept in freeze for 1 hour for diffusion and then incubated at 37 °C for 24 h. of the medium was adjusted to 7.0 by using NaOH. Agar powder was added and medium was heated to dissolve the agar to form a clear liquid, the final volume was made by distilled water. Sterilized it in autoclave at 121 °C, 15 lb pressure for 15 min. The medium was allowed to cool up to 50 °C, and poured quickly into sterile petri plates under aseptic conditions.

CONCLUSION
The preparation procedure followed in this work for the synthesis of title compounds offers a reduction in the reaction time, operation simplicity and easy work-up. All spectroscopic analysis confirmed the proposed structures for these compounds. Antimicrobial data have shown that synthesized compounds 5a,5b,5d,5e,5g,5h,5i,5j showed significant activity against gram-positive micro-organism and synthesized compounds 5c,5f,5k,5l showed significant activity against gram-negative microorganism.

ACKNOWLEDGMENT
Authors are thankful to the principal,Dr. V. V. P. F's College of Pharmacy, Vilad ghat, Ahmednagar for providing research facilities.