The chemistry of pseudomonic acid. Part 2. The conversion of pseudomonic acid A into monic acid A and its esters

Abstract

By suitable protection and deprotection, the 9-hydroxynonanoic acid side-chain of pseudomonic acid A (1a), a naturally occurring antibiotic, was cleaved in a highly efficient one-pot reaction to the allylic acid (3a), 4-[5S(2S,3S-epoxy-5S-hydroxy-4S-methylhexyl)-3R,4R-dihydroxytetrahydropyran-2S-yl]-3-methylbut-2(E)-enoic acid. We have ascribed the trivial name, monic acid A, to this allylic acid. Esters of monic acid A were readily prepared from the free acid (3a) and also from the ketone (2) which could be condensed with phosphonoacetates.