Stereoselective iodolactonization of 4-allenoic acids with efficient chirality transfer: development of a new electrophilic iodination reagent.

A highly stereoselective iodolactonization of 4-allenoic acids with a new sterically demanding electrophilic iodination reagent to afford optically active γ-butyrolactones has been developed. The reaction shows high efficiency of axial chirality transfer and excellent Z/E selectivity and has been applied to the synthesis of chiral cis-β,γ-disubstituted γ-butyrolactones to give very high diastereomeric and enantiomeric excess values. The reaction has been successfully utilized in the synthesis of naturally occurring compounds (+)-cis-whisky lactone and (+)-cis-3-methyl-4-decanolide.