Synthesis of some potential antimicrobial carbocyclic compounds

Abstract

Some naturally occurring compounds containing the naphtho [2,3 - c] pyran ring system have been found to be useful antibiotic agents and thus the laboratory synthesis ofthese compounds and their derivatives are of importance in the medical field. Their antibiotic and even antineoplastic activities are attributed to their potential to act as alkylating agents, via a bioreductive process. This thesis deals with studies directed towards the synthesis of some benzo [c] pyrans as these compounds also possess the correct structural configuration to undergo the bioreductive process, and act as alkylating agents to cellular nucleic acids. Chapter Two describes the synthesis 00,4 dihydro - 1,3 - dimethyl- IH - benzo - [cl pyran - 5,8 - quinone (13) by employing a base induced cyclization with potassium tertiary butoxide. This compound was proven to be biologically active against both Gram positive and Gram negative organisms. (±) (1R, 3R, 4R) - 3,4 - Dihydro - 4 - hyroxy -1,3 - dimethyl- 1H - benzo [e] pyran - 5,8quinone (17) and its 4 S diastereomer (18) were synthesized with cerium (IV) ammonium nitrate as the cyclizing reagent. Antimicrobial evaluation ofcompound (17) displayed inhibitory activity against both Gram positive and Gram negative organism growth. This is discussed in Chapter Three. In Chapter Four, the synthesis ofthe benzo analogue ofthe naturally occurring naphthopyran antibiotic, hongconin, is discussed. The synthetic route used for this synthesis could well be applied to synthesise hongconin.