phenylalanine is used to make diketopiperazine (not shown). then enzymes epoxidate diketopiperazine to make the arene oxide. this undergoes a 6π disrotatory ring opening electrocyclization reaction to produce the uncyclized oxepine. after a second epoxidation of the ring, the nearby nucleophilic nitrogen attacks the electrophilic carbon, forming a five membered ring. the resulting ring system is a common ring system found in aranotin and its related compounds.