[4+2] Cycloaddition Mediated Stereoselective Synthesis of Tetrahydro-1H-Isobenzofuro Chromene Dione Derivatives: Antibacterial Evaluation and Molecular Docking Investigation

An efficient stereoselective synthesis of tetrahydro-1H-isobenzofuro[4,5-c]chromene-1,3(3aH)-dione derivatives were achieved through a novel [4+2] cycloaddition reaction of 4-styryl-2H-chromenes with cheaply available maleic anhydride. A series of new tetrahydro-1H-isobenzofuro[4,5-c]chromene-1,3(3aH)-dione derivatives 21(a–p) were synthesized in good to excellent yield under mild reaction condition with no chromatographic purification. In this reaction, the generation of four new consecutive stereogenic centers were determined by single crystal X-ray analysis. All the synthesized compounds were investigated further in silico and in vitro for antibacterial activities using two bacterial strain of DNA gyrase. Compounds 21 b and 21 j showed excellent docking score −9.3 kCal/mol and −8.6 kCal/mol with gram negative bacterial strain Escherichia coli (E. coli) with protein data bank (PDB ID) 3G7E. Out of all the tested molecules, 21 b and 21 j displayed good results with minimum inhibitory concentration 10 μg/ml, 10 μg/ml against the bacterial strain Escherichia coli(E. coli) and 10 μg/ml, 20 μg/ml against Staphylococcus aureus (S. aureus) respectively.