Cyclohexanoid protoflavanones from the stem-bark and roots of Ongokea gore

Four novel protoflavanones with hydrogenated B-ring were isolated from Ongokea gore (Olacaceae) and named as (2S)-ongokein-4′-one (1), (2S)-4′,4′-dimethoxy-ongokein (2), (2S)-cis-4′-hydroxy-ongokein (3), and (2S)-trans-4′-hydroxy-ongokein (4).