Biomimetic synthesis of acid-sensitive (−)- and (+)-caparrapi oxides, (−)- and (+)-8-epicaparrapi oxides, and (+)-dysifragin induced by artificial cyclases
Asymmetric total syntheses of acid-sensitive (-)- and (+)-caparrapi oxides (1) and (+)-8-epicaparrapi oxide (2) from farnesol (10) are achieved using Sharpless-Katsuki epoxidation and Lewis acid-assisted chiral Bronsted acid (chiral LBA)-induced polyene cyclization as key steps. The relative configuration of (+)-dysifragin (4) is determined by a single-crystal X-ray diffraction and its totalsynthesis is accomplished