合成路线1

Commercially available aldehyde (I) was reduced to alcohol (II) with NaBH4. After protection of the hydroxyl group of (II) as the tert-butyldiphenylsilyl ether (III), hydrolysis of the benzoate ester of (III) using K2CO3 in MeOH afforded the 11R alcohol (IV). Displacement of the hydroxyl group of (IV), with inversion of the configuration, by means of (diethylamino)sulfur trifluoride generated the 11S fluoride (V), along with minor amounts of olefin (VI). Separation was achieved by dihydroxylation of the olefin (VI) with N-methylmorpholine-N-oxide and OsO4, followed by column chromatography. Reduction of the lactone group of (V) with diisobutylaluminum hydride at -78 C yielded lactol (VIII). Wittig condensation with the phosphorane resulting from phosphonium salt (IX) and t-BuOK furnished the Z-olefin (X). The carboxylate group was then converted to isopropyl ester (XI) by treatment with isopropyl iodide and DBU.