Mulberrofuran G (1) and isomulberrofuran G (2), a pair of isomeric Diels-Alder-type adducts, were isolated from the root bark of Morus alba L. Isomulberrofuran G (2) as a new IIB-type Diels-Alder-type adduct, was elucidated by extensive (1)H, (13)C, and two-dimensional (2D) nuclear magnetic