Synthesis and Bioactivity of a Macrocidin B Stereoisomer.

A stereoisomer of macrocidin B, a presumed metabolite of the fungus , was synthesized in 18 steps and 2.7% yield from protected l-tyrosine that was -β-ketoacylated with a fully functionalized octanoyl Meldrum's acid. Dieckmann condensation gave a 3-acyltetramic acid, which was macrocyclized via Williamson etherification between the phenol and -bromohydrin termini. This macrocidin B stereoisomer showed a weaker herbicidal effect than macrocidin A and no similar inhibitory effect on biofilms of .