Original Article STEREO SELECTIVE SYNTHESIS OF NOVEL PYRAZOLE AND COUMARIN APPENDED BRIDGED PYRANS AS ANTIMICROBIAL AGENTS N. RENUKA, K. AJAY KUMAR * Post Graduate Department of Chemistry, Yuvaraja’s College, University of Mysore, Mysore 570005, India Email: ajaykumar@ycm.uni-mysore.ac.in Received: 19 Jun 2015 Revised and Accepted: 08 Aug 2015 ABSTRACT Objectives: The aim of the present study was to synthesize a series of novel bridged pyrans as antimicrobial agents. Methods: An isomeric mixture of 3-(4-ethoxy-10-methyl-8-oxo-2-phenyl-4,8-dihydro-2H-pyrano[3',2':6,7]chromeno[4,3-c]pyrazol-6-yl)-1-phenyl- 1H-pyrazole-4-carbaldehydes, 2(a-f) and 3-(4-ethoxy-8-methyl-10-oxo-2-phenyl-4,10-dihydro-2H-pyrano[2',3':5,6]chromeno[4,3-c]pyrazol-6-yl)- 1-phenyl-1H-pyrazole-4-carbaldehydes, 3(a-f) were synthesized by the reaction of 3,3'-(7-hydroxy-4-methyl-2-oxo-2H-chromene-6,8-diyl)bis(1- phenyl-1H-pyrazole-4-carbaldehyde) 1(a-f) and ethyl alcohol in the presence of conc. H2SO4. The synthesized compounds were evaluated for their antimicrobial activity. Results: The structures of the new bridged pyran analogues 3-(4-ethoxy-10-methyl-8-oxo-2-phenyl-4,8-dihydro-2H-pyrano [3',2':6,7] chromeno [4,3-c]pyrazol-6-yl)-1-phenyl-1H-pyrazole-4-carbaldehydes, 2(a-f) and 3-(4-ethoxy-8-methyl-10-oxo-2-phenyl-4,10-dihydro-2H-pyrano [2',3':5,6] chromeno[4,3-c]pyrazol-6-yl)-1-phenyl-1H-pyrazole-4-carbaldehydes, 3(a-f) were confirmed by spectral studies and elemental analysis. The compounds 2e and 3e were having-CONH2 substitution and 2f and 3f were having-CSNH2 substitutions in the pyrazole rings showed antibacterial at minimum concentrations against all the tested organisms. Conclusions: Results of the antimicrobial activity reveal that some of the synthesized compounds act as potential antimicrobial agents against different fungal and bacterial organisms. Keywords: Antibacterial, Antifungal, Cyclisation, Formyl pyrazoles, Inhibitory. INTRODUCTION The construction of complex molecular architectures that exhibit greater biological potency in a facile and efficient manner remains an overarching goal for the chemists. In recent years coumarin libraries have attracted great attention because of their synthetic utility as building blocks for the construction of bioactive molecules. Coumarin derivatives are known to a wide range of activities; such as an antioxidant, antimicrobial, anti-HIV, antibiotic, anticancer, muscle relaxant, anti-inflammatory and anticoagulant properties [1]. An efficient synthesis of poly functionalized 4H-pyrans is carried out in one pot synthesis from an aldehyde, malononitrile and an active methylene diketo compound using a heterogeneous Mg/la mixed oxide catalyst [2]. A facile one-pot expeditious synthesis of 2-amino-4H-pyrans and 2- amino-5-oxo-5, 6, 7, 8-tetrahydro-4H-chromenes under solvent-free conditions using magnesium oxide as a catalyst is reported [3]. Pyrazole scaffolds drew a great deal of attention due to its contribution in biological and pharmacological fields [4]. The pyrazole nucleus has pronounced pharmacological applications such as anti-inflammatory [5], antimicrobial [6], antioxidant [7] and analgesic activity [8]. They have a long history of applications in agrochemicals and pharmaceutical industry as herbicides and active pharmaceuticals. In search of new antimicrobial agents and in continuation of our work on coumarin analogues we herein report the synthesis of a series of isomeric bridged pyrans tagged to pyrazole and coumarin skeleton and their antimicrobial activities. Experimental In a typical procedure, a series of isomeric bridged pyrans tagged to pyrazole and coumarin moiety 2(a-f) and 3(a-f) were synthesized by the condensation reaction of 3,3'-(7-hydroxy-4-methyl-2-oxo-2H- chromene-6,8-diyl)bis(1-aryl-1H-pyrazole-4-carbaldehyde), 1(a-f) in ethyl alcohol (10 ml) in the presence of conc. H2SO4 (5 ml) under reflux conditions (Scheme-1). International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 7, Issue 10, 2015 Innovare Academic Sciences