Chiral preparation of polyoxygenated cyclopentanoids

A series of polyoxygenated cyclopentanoids, including 2,2-dimethyl-3a,6a-di hydro-4H-cyclopenta[d][1,3]dioxol-4-one, has been prepared in both enantiom eric forms from cyclopentadiene by employing lipase-mediated kinetic resolu tion as the key step. Thus, cyclopentadiene is first transformed into racem ic cis-4-cumyloxycyclopent-2-en-1-ol which is resolved under transesterific ation conditions in the presence of lipase PS. After transformation into th e corresponding tert-butyldimethylsilyl (TBS) ethers, each of the enantiome rs is cis-dihydroxylated diastereoselectively from the less hindered face w hich is transformed into the 2,3-O-isopropy-lidene-1,4-di-O-protected (tran s-1-2:cis-2,3:trans-3,4)-1,2,3,4-cyclopentanetetraol. Selective removal of the 1,4-protecting group gives the corresponding 2,3,4-O-protected cyclopen tanols which are further transformed into the 2,3,4-0-protected cyclopentan ones on oxidation without suffering p-elimination. Exposure of the cyclopen tanones to warm acetic acid allows beta-elimination to give rise to the deh ydration product 2,2,-dimethyl-3a,6a-dihydro-4H-cyclo-penta[d][1,3]dioxol-4 -one having the corresponding chirality without losing their original chira l integrity.