LL-Z1220 is an antibiotic with the structure 2-(3,8-dioxabicyclo[5.1.0.0^~^~]oct-5-en-5-yl)-4H-pyran-4-one. It is reportedly the first naturally occurring compound to contain a benzo-1,2-dioxepin group. This antibiotic easily undergoes valence tautomerization to form 1,4-dioxo bridge octane. The compound's chemical and spectroscopic properties indicate that the benzo-1,2-dioxepin has a cis configuration.