(±)-Melicolones A and B, Rearranged PrenylatedAcetophenone Stereoisomers with an Unusual 9-Oxatricyclo[3.2.1.13,8]nonane Core from the Leaves of Melicope ptelefolia.

MelicolonesA (1) and B (2), a pair ofrearranged prenylated acetophenone epimers with an unusual 9-oxatricyclo[3.2.1.13,8]nonane core, were isolated from the leaves of Melicopeptelefolia.Further chiral high-performance liquid chromatographyresolution gave enantiomers (+)- and (−)-1, aswell as (+)- and (−)-2, respectively. The structuresand absolute configurations of the pure enantiomers were determinedby extensive spectroscopic data and single crystal X-ray diffraction.All the isolated enantiomers exhibited potent cell protecting activitiesagainst high glucose-induced oxidative stress in human vein endothelialcells. [ABSTRACT FROM AUTHOR]