Stereocontrolled approach to δ- and γ-lactones and 1,3-diols. The role of X− ion in the selenolactonization

Two complementary approaches have been realized for the stereoselective synthesis of 4,6-disubstituted δ-lactones and 1,3-anti and syn diols. In the 6-endo selenolactonization the role of the X− ion on the stereoselectivity is shown. Moreover, the highly stereoselective transformation of the 6-endo δ-lactone to the 5-exo γ-lactone is reported.