A Catalytic Asymmetric Protecting-Group-Free Total Synthesis of (4S,5S)-4,8-Dihydroxy-3,4-dihydrovernoniyne and Its Enantiomer.

A catalytic asymmetric second generation synthesis of (4S,5S)-4,8-dihydroxy-3,4-dihydrovernoniyne has been completed employing the asymmetric dihydroxylation strategy. Further, a four-step protecting-group-free synthesis of the natural product and its enantiomer has been achieved through the modified Knoevenagel reaction, asymmetric dihydroxylation, and Cadiot-Chodkiewicz coupling. The protecting-group-free synthesis is completed in four steps and 41% overall yield.