Ring-closing metathesis/fragmentation route to geometrically defined medium-ring cycloalkenes: total synthesis of (+/-)-periplanone C.

The combination of alkene metathesis and beta-fragmentation offers an efficient entry into (Z)-configured medium-ring cycloalkenes. The versatility of this method is demonstrated by the total synthesis of Periplanone C, a semiochemical of Periplaneta americana. [reaction: see text]