Four new ionophoric resin-glycosides have been isolated from the tuber of Merremia mammosa (Convolvulaceae), an Indonesian folk medicine ("Bidara upas"). The structures of two major resin-glycosides, named mammosides B (1__∼) and H1 (2__∼), have been determined on the basis of chemical and physicochemical evidence including a synthesis of the glycosidic acid designated as mammoside I (3__∼).