7‐Bromocavernicolenone, a New α‐Bromoenone from the Mediterranean Sponge Aplysina (= Verongia) cavernicola. Implied, Unprecedented Involvement of a Halogenated Dopa in the Biogenesis of a Natural Product

Abstract

<jats:title>Abstract</jats:title><jats:p>A novel, mildly antibacterial, α‐bromoenone (7‐bromocavernicolenone) has been isolated from the Mediterranean sponge <jats:italic>Aplysina</jats:italic> (= <jats:italic>Verongia</jats:italic>) <jats:italic>cavernicola</jats:italic>. Its structure, 7‐bromo‐1,5‐dihydroxy‐2‐azabicyclo[3.3.1]non‐6‐en‐3,8‐dione (<jats:bold>3</jats:bold>), is based on X‐ray and NMR analysis and on the observation that acetylation of <jats:bold>3</jats:bold> affords two monoacetates. An unprecedented phenol oxidative biogenetic pathway is suggested leading to 7‐bromocavernicolenone <jats:italic>via</jats:italic> 3‐bromotyrosine and 5‐bromodopa.