Synthesis and antimicrobial screening of some C-4- hydroxybenzo[c]pyranquinones

Abstract

Many naturally occurring antibiotics have been identified and their synthesis successfully carried out in laboratories. It was envisaged by our group that by preparing a variety of, for example, quinoid compounds and then comparing their biological properties and activities, a better insight would be gained into a molecular structure - activity relationship. Chapter 1 deals with the attempted synthesis of 2-(1 '-hydroxyethyl)-3-(prop-2'enyl)- 1,4-benzoquinone (17) which may be converted by known methods into benzopyran derivatives. The second chapter describes a synthetic route to (±)(3R, 4R)-3,4-dihydro-3methyl- 4-hydroxy-l H-benzo[c]pyran-5,8-dione (42) and its (±)(45) diastereomer (43), both of which were found to be active against Gram negative and Gram positive organisms. The trans-l,3-dimethyl-4-hydroxypyranquinones (45) and (46) were also successfully synthesised. A different route of synthesis for the compounds (53), (54), (55) and (56) was also investigated. Several compounds were evaluated for biological activity. It was found that the quinones synthesised during this study were active against Gram negative and Gram positive bacteria, with the exception of compound (25) which had an acetate group in place of a hydroxy group. It was found that this trend was carried through all of the quinone derivatives tested.