An Expeditious Synthesis of (±)-Desepoxy-4,5-didehydromethylenomycin A Methyl Ester

A total synthesis of the racemic methyl ester of desepoxy-4,5-didehydromethylenomycin A has been achieved in six steps with an overall yield of 31% starting from diethyl methanephosphonate. The key steps include the Nazarov cyclization of the dienone 7 leading to the α-phosphoryl cyclopentenone 8 and the Horner−Wittig reaction of the latter employed for the introduction of the exocyclic methylene moiety.