Asymmetric transformation of meso-epoxides by chiral lithium amides

Asymmetric reactions by the use of chiral lithium amide have become one of efficient methods for the preparation of chiral compounds for these ten years. We examined enantioselective deprotonation of meso-epoxides by chiral lithium amide, prepared from chiral diamine, e.g., (S)-2-(pyrrolidin-1-yl) methylpyrrolidine. Chiral allylic alcohols were obtained by the reaction, and especially in the cases of 4-substituted cyclopentene oxides high selectivity was achieved to afford synthetically useful cyclopentenol derivatives in high enantiomeric excesses. Both enantiomers of 4-hydroxy-2-cyclopentenone, (-)-carbovir, (-)-aristeromycin, and (-)-untenone A were synthesized by applying the reaction. The reaction was extended to a catalytic asymmetric reaction by the use of a catalytic amount of the chiral lithium amide and excess of lithium diisopropylamide. The chiral lithium amide was also found to be effective for kinetic resolution of racemic epoxides.