合成路线1

The reaction of bromide (V) with Mg and then with CuBr and propyne gives a cuprate complex that is treated with 1-hexyne, yielding the nonisolated copper complex (VII). The reaction of the protected chiral epoxide (IX) (obtained by reaction of the epoxide (VIII) with Pmb-Br, NaH and TBAI in THF) with copper complex (VII) affords the (Z)-alkene (X), which is treated with Sem-Cl and DIEA to protect its OH group, providing (XI). Selective elimination of the Pmb protecting group of (XI) with DDQ furnishes the secondary alcohol (XII), which is oxidized under Swern protocol to the ketone (XIII) with (COCl)2 and TEA in dichloromethane. The Wadsworth-Emmons olefination of (XIII) with the known phosphonate (XIV) by means of BuLi in THF gives pure triene (XV), which is submitted to a diastereoselective hydroboration with bis(diisopinocampheyl)borane and oxidative workup to yield the primary alcohol (XVI). The Swern oxidation of (XVI) with (COCl)2 affords the aldehyde (XVII), which is submitted to an aldol condensation with the intermediate oxoacid (V) by means of LDA in THF to provide the aldol product (XVIII) as a (6R,7S)(6S,7R) diastereomeric mixture.