Total synthesis of pinellic acid, a potent oral adjuvant for nasal influenza vaccine. Determination of the relative and absolute configuration

Pinellic acid (1), isolated from a medicinal plant Pinelliae tuber, has potent adjuvant activity. The absolute configuration of pinellic acid was expected by derivatization of this compound and CD exciton chirality method. A convergent synthetic route to pinellic acid has been developed via regioselective asymmetric dihydroxylation and stereoselective reduction. The absolute configuration of pinellic acid was determined to be 9S,12S,13S, by comparing with the spectra data of natural and synthetic compounds.