合成路线1

The transesterification of ketoester (XI) with the menthol derivative (XII) gives the chiral ester (XIII), which is cyclized by means of manganic acetate and ytterbium trifluoromethanesulfonate in trifluoroethanol yielding the octahydrophenanthrene (XIV). The enolization of (XIV) with KHMDS and N,N-bis(trifluoromethylsulfonyl)aniline in THF affords the enol triflate (XV), which is reduced at the ester group with DIBAL in dichloromethane giving the hydroxymethyl derivative (XVI). The cyclization of (XVI) with CO by means of Pd(PPh3)4 and tributylamine in acetonitrile yields the cyclic lactone (XVII), which is oxidized with CrO3 in acetic acid affording the furophenanthrenedione (XVIII). Demethylation of (XVIII) with BBr3 in dichloromethane gives the phenolic intermediate (XIX), which is reduced with NaBH4 in methanol to yield the diol (XX). The selective epoxidation of (XX) with NaIO4 in methanol/water gives the ketoepoxide (XXI), which by a new epoxidation with trifluoroacetone and oxone in aqueous acetonitrile affords the diepoxide (XXII). A further new epoxidation of (XXII) with H2O2 and NaOH in methanol gives the keto-triepoxide (XXIII), which is finally reduced to (-)-triptolide with NaBH4 and Eu(FOD)3 in methanol.