The dioxo-lignans of the arylnaphthalene-type named justicidone (2) and elenodione (3) were obtained from elenoside (1) through a short and efficient semisynthetic process. Justicidone (2), one of its synthetic precursors, 4-(benzo[d][1,3]dioxol-5-yl)-5,6,8-trimethoxy-3a,4-dihydronaphtho[2,3-c]furan-1(3H)-one (9), and the aglycone of elenoside (5) showed cytotoxic activity towards the HL-60 cell line (IC50 = 7.25 miroM, 5.41 microM and 2.06 miroM, respectively).