合成路线1

Preparation of the allyl alcohol precursor (XXX) was further reported by an alternative method described in the two following schemes: The symmetrical epoxide (XXXV) was cleaved by 1,3-propanediol (II) in the presence of potassium tert-butoxide to give the diol (XXXVI). After protection of the primary alcohol of (XXXVI) as the pivalate ester (XXXVII), the benzyl ether groups of (XXXVII) were removed by hydrogenation in the presence of palladium hydroxide to provide (XXXVIII). Protection of the vicinal diol moiety of (XXXVII) as the corresponding acetonide (XXXIX) was achieved by treatment with 2,2-dimethoxypropane and p-TsOH. Subsequent Swern oxidation of the primary alcohol function of (XXXIX) gave aldehyde (XL). Addition of vinylmagnesium bromide to aldehyde (XL) afforded the allylic alcohol (XLI) as a diastereomeric mixture. Esterification of (XLI) with pivaloyl chloride provided dipivalate ester (XLII). Epoxide (XLIII) was then prepared by acidic acetonide (XLII) hydrolysis, followed by cyclization of the resultant vicinal diol under Mitsunobu conditions to afford epoxide (XLIII). Addition of the O-protected lithium acetylide (XLIV) to epoxide (XLIII) furnished the acetylene adduct (XLV)