In part XI12 we reported the isolation of four unknown alkeloids together with several alkaloids from Stephania sasakii HAYATA (Menispermaceae) collected in Formosa. This paper describes the characterization and structural establishment of two alkaloids (tentatively named Base A and Base D) out of the four unknown alkaloids. Base A was established as 4-hydroxycrebanine (1), a new 4-hydroxyaporphine alkaloid, via elemental analyses, spectral data (UV, IR, PMR, MS) and stereoselective hydroxylation of crebanine. Base D was established as (R)-roemeroline (3), identified as N-methylanolobine through N-methylation of anolobine, with (R)-configuration confirmed by ORD and CD data, named (R)-roemeroline to avoid confusion.