合成路线1

The olefinic diester (XXXVIII) was subjected to OsO4-catalyzed asymmetric dihydroxylation using hydroquinidine 1,4-phthalazinediyl diether [(DHQD)2-PHAL] as chiral ligand to afford diol (XXXIX). This was converted to the cyclic sulfate (XL) by treatment with SOCl2, followed by RuCl3-catalyzed NaIO4 oxidation of the intermediate sulfite. Regioselective reduction of sulfate (XL) at the alpha position with NaBH4 in DMA led to the (3S)-alcohol (XLI). Further selective reduction of the ethyl ester group of (XLI) was achieved by treatment with NaBH4-Et3N in MeOH-DMF, yielding the target intermediate dihydroxy ester (XIII).