Toward the Macrocidins: Macrocyclization via Williamson Etherification of a Phenolate

The synthesis of macrocyclic 3-acyltetramic acids which are immediate precursors of the fungal herbicide macrocidin A (1) is reported. The crucial closure of the macrocycle was achieved in excellent yield by an unprecedented Williamson etherification of an ω-bromo phenolate generated in situ by a Pd-mediated O-deallylation.