合成路线1

The diastereomeric mixture of tetrahydropyranyl-protected compounds (VI) was hydrolyzed with pyridinium p-toluenesulfonate to furnish the epoxyalcohols (VII). From this mixture, the target isomer (IX) was obtained by two alternative procedures. Condensation of (VII) with 3,5-dinitrobenzoic acid under Mitsunobu conditions proceeded with inversion of configuration. Further recrystallization of the resulting diastereomeric esters from EtOAc provided isomer (VIII). This was hydrolyzed with NaOH to yield the S,R-epoxyalcohol (IX). Alternatively, the diasteremeric epoxyalcohols (VII) were coupled with 3,5-dinitrobenzoyl chloride with retention of configuration. Recrystallization furnished isomer (X), which was subsequently hydrolyzed to the R,R-epoxyalcohol (XI). Inversion of configuration was then achieved by Mitsunobu coupling with benzoic acid, followed by hydrolysis of the resulting benzoate ester (XII).