Total synthesis of proposed elgonene C and its (4 R ,5 R )-diastereomer.

The total synthesis of the proposed elgonene C (1) and its (4 R ,5 R )-diastereomer (1a) has been achieved using a second-generation oxazaborolidinium ion-catalysed Diels-Alder reaction, Sharpless asymmetric dihydroxylation, and a Ni-catalysed cross-carboxyl coupling reaction via redox-active ester (RAE) formation as key reactions. The spectral and analytical data for our synthetic compounds 1 and 1a do not match the isolation data provided by Stadler et al . which indicates that structural revision is required for the proposed elgonene C.