合成路线1

A further procedure utilized the (S)-keto ester (XXXI) as the chiral starting material. Baeyer-Villiger oxidation of cyclohexanone (XXXI) with m-CPBA in the presence of a phosphate buffer at pH 8 provided two regioisomeric chiral lactones (XXXII) and (XXXIII), which were separated by column chromatography. The major isomer (XXXII) was subsequently reduced with LiAlH4 to furnish triol (XXXIV). The 1,3-dihydroxy moiety of (XXXIV) was then protected as the acetonide derivative (XXXV) employing 2,2-dimethoxypropane. The requisite ester (XXXVII) was prepared by stepwise oxidation of the primary alcohol (XXXV) to the aldehyde (XXXVI) using pyridinium dichromate, and then to the corresponding carboxylic acid with m-CPBA, followed by esterification with ethereal diazomethane to (XXXVII). Hydrolysis of the acetonide (XXXVII) by means of p-toluenesulfonic acid in methanol led to the target intermediate, the dihydroxy ester (XIII).