合成路线1

A stereoselective synthesis of beta-elemene has been reported: Reaction of 2-allylpropane-1,3-diol (I) with tosyl chloride and pyridine gives the ditosylate (II), which is treated with NaCN in refluxing DMF to yield the dinitrile (III). The methanolysis of (III) with TsOH and refluxing methanol affords the dicarboxylic acid (IV), which is reduced with LiAlH4 in THF providing 3-allyl-1,5-pentanediol (V). The reaction of (V) with CBr4 and PPh3 in dichloromethane gives the dibromide (VI), which is ozonolyzed with ozone and PPh3 in dichloromethane to yield the aldehyde (VII). Condensation of (VII) with the phosphorane (VIII) in dichloromethane affords the unsaturated ester (IX), which is reduced with DIBAL in toluene to afford alcohol (X). Condensation of (X) with triethyl orthopropionate (XI) in refluxing phenol/toluene gives the anti-dibromoester (XII), along with some syn-isomer that is easily separated. Cyclization of (XII) with LDA in THF yields the cyclohexanecarboxylate (XIII), which is treated with t-BuOK in THF to afford the divinylcylohexanecarboxylate (XIV). Reduction of (XV) with DIBAL in toluene provides the carbinol (XV), which is treated with CuCl, PdCl2 and O2 in DMF/water giving the acetyl derivative (XVI). Oxidation of (XVI) with PCC and AcONa in dichloromethane gives keto-aldehyde (XVII), which is finally submitted to a double Wittig methylenation with methylenetriphenylphosphorane (XVIII) in THF.