Determination of the Absolute Configuration of Khellactone Esters from Peucedanum japonicum Roots

Sixteen new angular dihydropyranocoumarins (1–16) and 24 known compounds were isolated from the roots of Peucedanum japonicum Thunb. The absolute configuration of diacylkhellactone was established by partial hydrolysis, the Mosher method, and X-ray crystallography. In addition, ECD spectroscopy was used to assign the absolute configurations of several of the angular dihydropyranocoumarins. Enantiomers were detected by RP-HPLC using MTPA esters while acyl migration of the substituents was observed in cis-monoacylkhellactones.