Stereoselective synthesis of (+/-)-litsenolide C-2

The lithium (alpha-carbalkoxyvinyl) (2-thienyl) mixed higher order cyanocuprate, derived from ethyl propargylic ester with (n-C13H27) (2-thienyl) CuCNLi2, reacted with cis-1-bromo-1-propylene under Pd(PPh3)(4) catalysis to give a diene ester ethyl 1-(Z-propylidene)-1-E-hexadecenate. Then the target product (+/-)-litsenolide C-2 was stereoselectively synthesized by employing cis-dihydroxylation of the diene ester using a NMO-OsO4 system as the oxidant and stereospecific lactonation by acidic catalyst. The ratio of E to Z carbon-carbon double bond is >98 : 2, and the ratio of trans- and cis-disubstituted lactones is >95 : 5.