Highly enantioselective elimination of meso-compounds

Abstract

Useful chiral synthons for the synthesis of natural products, consisting of derivatives of the fixed five-membered ring system bicyclo[3.3.0]oct-2-ene, were obtained in high optical purity (87–99% e.e.) by asymmetric elimination of the corresponding achiral (meso) trifluoromethanesulphonates with chiral N,N-dimethyl-1-phenylethylamine. However, asymmetric elimination of the chiral (+)-camphor-10-sulphonates with an achiral base resulted in low optical purity. In this enantioselective asymmetric elimination, the concave side of bicyclic ring system seems to play an important role. Asymmetric elimination of the monotriflate of cis-cyclohexane-1,4-diol resulted in a product with unsatisfactory optical purity.