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.