Dibromomethane as one-carbon source in organic synthesis: total synthesis of (±)- and (−)-methylenolactocin

A general method was developed to construct monocyclic α-methylene-γ-butyrolactone moiety. The key step is to introduce the α-methylene group by the ozonolysis of mono-substituted alkenes followed by reacting with a preheated mixture of CH2Br2–Et2NH. Application of this key step in the total synthesis of the (±)- and (−)-methylenolactocin was described.