. Can. J. Chem. 55, 2336 (1977). Studies on the biodegradation of (+)-usnic acid (1) by a Pseudomonas species have revealed a novel aromatic deacylation process. The isolated metabolite, (+)-6-desacetylusnic acid (2) is crystalline and its structure is established by means of spectroscopic and chemical methods. The synthesis of 2 from usnic acid (1) is also reported and provides conclusive evidence for the structure of this metabolite.