Asymmetric [2,3]-Wittig rearrangement of the dienolates of chiral secondary alcohol-substituted β-pyrrolidinyl-γ-allyloxyl-α,β-unsaturated esters: total synthesis of (+)-eldanolide

The asymmetric 2,3]-Wittig rearrangement of the dienolates of various chiral β-pyrrolidinyl-γ-allyloxyl-α,β-unsaturated esters was investigated using different chiral secondary alcohol substitutions. When (1S,2R,4R)-2-hydroxy-7,7-dimethylbicyclo2,2,1]heptane-1-carboxylic acid diisopropylamide was used as chiral auxiliary, it provided the best enantioselectivity in the rearrangement. When various γ-allyloxy substitutions underwent temperature and additive studies, 1,1-dimethylpropenoxy substitution was found to give the best enantioselectivity. The methodology was applied to the total synthesis of (+)-eldanolide.