合成路线1

The enzymatic resolution of the tricyclic carboxylate (XXIX) with chiralzyme L-2 and vinyl acetate gives the monoacetate (XXX) and the dihydroxy compound (XXXI) that are easily separated. The monosilylation of the less hindered OH group of (XXXI) with TBDMS-Cl and imidazole in DMF gives the monosilylated compound (XXXII), which is acylated with acetyl chloride, TEA and DMAP in dichloromethane yielding the monoacetate (XXXIII). The desilylation of (XXXIII) with TBAF in THF affords the secondary alcohol (XXXIV), which is oxidized with ammonium formate and PdCl2(PPh3)2 in acetonitrile to give the unsaturated ketone (XXXV). The epoxidation of the double bond of (XXXV) with H2O2 and Triton B in THF yields the ketoepoxide (XXXVI), which is reduced with NaBH4 in methanol to the epoxy alcohol (XXXVII). The esterification of (XXXVII) with benzoyl chloride affords the benzoate (XXXVIII), which is submitted to thermolysis at 300 C in diphenyl ether to provide the cyclohexenecarboxylate (XXXIX).The reaction of (XXXIX) with BF3 ethearate in toluene gives, through the nonisolable oxonium intermediate (XL), the monobenzoate (XLI), which is debenzoylated with K2CO3 in methanol to provide the methyl ester (XLII) of the target compound. Finally, this compound is hydrolyzed with KOH in THF.