合成路线1

The title compound was prepared starting from the known bicyclic lactone (VI). Oxidation of the primary alcohol function of (VI) to the corresponding aldehyde (VII) was accomplished by either following the Pfitzner-Moffat method or by means of Dess-Martin perodinane reagent. Aldehyde (VII) was then converted to enone (IX) by Wittig reaction with the phosphonium salt (VIII) or, in a related method, by Wadsworth-Emmons condensation of (VII) with phosphonate (IV). Stereoselective reduction of enone (IX) with either L-selectride or (-)-B-chlorodiisopinocampheylborane produced the (15S)-allylic alcohol (X) as the major diastereoisomer, which was isolated by flash chromatography. Then, catalytic hydrogenation of the double bond of (X) gave the saturated alcohol (XI). Reduction of the lactone function employing DIBAL led to the protected lactol (XII). Subsequent removal of the phenylbenzoyl group of (XII) with K2CO3 in methanol furnished dihydroxy lactol (XIII). In a variation of this sequence, the phenylbenzoyl group of (XI) was first removed by methanolysis, and the resultant dihydroxy lactone (XIV) was then reduced with DIBAL to lactol (XIII).