STEREOSELECTIVE SYNTHESIS OF (+ -)-LITSEN OLIDE C-2/

The lithium (alpha-carbalkoxyvinyl) (2-thienyl) mixed higher order cya nocuprate, derived from ethyl propargylic ester with (n-C13H27) (2-thi enyl) CuCNLi2, reacted with cis-1-bromo-1-propylene under Pd(PPh3)(4) catalysis to give a diene ester ethyl 1-(Z-propylidene)-1-E-hexadecena te. Then the target product (+/-)-litsenolide C-2 was stereoselectivel y synthesized by employing cis-dihydroxylation of the diene ester usin g a NMO-OsO4 system as the oxidant and stereospecific lactonation by a cidic 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.