Synthesis of the Bioherbicidal Fungus Metabolite Macrocidin A.

The second total synthesis of macrocidin A afforded the bioherbicidal fungal metabolite in 16 steps starting from doubly protected l-tyrosine. The 3-octanoyl side chain with the α-methyl group and an ω-bromo epoxide already in place was attached to the tetramic acid via a Yoshii-Yoda acylation, and the macrocycle was eventually closed in 55% yield by a Williamson etherification between the phenolate and the epoxy bromide.