合成路线1

Lithiation of dihydrofuran (VIII), followed by the addition of tributylstannyllithium, gave an intermediate (IX) that was quenched with methyl iodide to produce alcohol (X). Silylation of alcohol (X) with tert-butyl dimethylsilyl chloride then gave silyl ether (XI). Copper-catalyzed conjugate addition of the organolithium reagent derived from (XI) to the intermediate enone (VII), with subsequent enolate trapping with triethylsilyl chloride, afforded adduct (XII) as the major diastereoisomer. Epoxidation of the silyl enol ether (XII) with m-chloroperbenzoic acid, followed by selective desilylation using tetrabutylammonium fluoride/ammonium chloride, gave rise to hydroxy ketone (XIII). Methylation of (XIII) in the presence of silver oxide yielded methyl ether (XIV). Then, the keto group of (XIV) was stereoselectively reduced to (XV) employing L-selectride. After protection of the hydroxyl group of (XV) as the benzoate ester, simultaneous deprotection of the ketal and silyl ether functions under acidic conditions provided triol (XVI). Oxidative cleavage of the 1,2-diol moiety of (XVI) with NaIO4 gave ketone (XVII). This was converted to epoxide (XVIII) by stereoselective addition of in situ generated trimethylsulfoxonium ylide.