Green synthesis of tryptanthrin appended 4-spiropiperidines and their anti-bacterial evaluation

Abstract

Synthesis of 14 tryptanthrin appended 4-spiropiperidines and their detailed antibacterial evaluation are described. The synthesis was achieved by a green route employing ammonium acetate as a catalyst in the three-component reaction of tryptanthrin, malononitrile and m-phenylene diamine. The in vitro antibacterial activities of compounds were evaluated against ESKAPE pathogens and against clinical multidrug-resistant MRSA and VRSA isolates, from which the bromo- and chloro-substituted spiropiperidines 4b and 4c (MIC 4 μg/mL) was found to be most potent against S. aureus ATCC 29213 and 4c exhibited good selectivity index.