Chiral gas chromatographic separation of 2-oxabicyclo[3.3.0]octane derivatives and their synthetic precursors

Chiral GC separation of (+/-)-2-allyl-2-carboethoxycyclopentanone (9) and t he alcohols (+/-)-3-(hydroxymethyl)-5-carboethoxy-2-oxabicyclo[3.3.0]octane (7), (+/-)-2-allyl-2-carboethoxycyclopentanol (8), and their acetylated an d trifluoroacetylated derivatives were investigated on three derivatized be ta-cyclodextrins (CDs) diluted in SE-54 or 1701-OH: 2,3,6-tri-O-methyl-beta -CD (PMCD); 2,3-di-O-methyl-6-O-(tert-butyldimethylsilyl) -beta-CD (DIMETBC D); 2,3-di-O-acetyl-6-O-(tert-butyldimethyl)-beta-CD (DIACTBCD). The unders tanding of these chiral separations is extremelly relevant, since cyclopent anic and bicyclic cyclopentanic rings are common structural features of man y important natural products and new pharmaceutical drugs. In general DIMET BCD diluted in SE-54 showed the best chiral resolution to alcohols 7 and 8 and only DIACTBCD showed enantioselectivity to 9. Hydrogen bonds prediction and dipole moments data were obtained by molecular modeling calculations f or 7ab and 8ab and Ac and TFA derivatives. Comparison of these data with th e chromatographic parameters for the related compounds were used to explain the differences of their elution orders and diastereo- and enantiomeric se parations on the above chiral stationary phases (CSPs), The results suggest that the CSPs enantioselectivities are not affected by the carboethoxy-fun ctionalized cyclopentanic and bicyclic cyclopentanic rings themselves but m ainly by the functional group on the other stereogenic center.