In this paper, we report on the occurrence of dioncophylline B (2), which is also present in the roots (3), and on the isolation and structure elucidation of a further unusual 4 methoxylated naphthylisoquinoline alkaloid 3 from the leaves of this interesting plant. Compound 3 was isolated from the freeze-dried plant material by extraction and subsequent chromatography on silica gel. The new compound shows the presence of a 1,3-dimethyl-8-methoxyisoquinoline ring, with an additional methoxy group at C-4 that should not directly arise from the biogenetic acetate precursors. By contrast, as all other known Dioncophyllaceae alkaloids, the new compound lacks an oxygen function at C-6. From the "normal" (i.e. not high-field shifted) 1H-NMR signal for the methyl group on the naphthalene ring (δ = 2.50ppm) and from extensive NOE-experiments (see Fig. 1), the biaryl axis must be located between C-7 and C-6', like in 2. With this coupling site ("B" type) and the 4-methoxy substituent ("-acme" type), the new compound 3 was named dioncophyllacine B. As reported for 2 (3), 3 is not split up into stable atropisomers at room temperature, due to the low number and small size of the substituents next to the axis. Dioncophyllacine B (3) seems to be accompanied by further closely related alkaloids of the "-acme" type, but with other coupling positions. Their isolation and structure elucidation is in progress. The first species to "violate" the hitherto clear chemotaxonomic borderline between the Ancistrocladaceae (alkaloids with S-configuration at C-3 and an oxygen function at C-6, as in 1) and the Dioncophyllaceae (alkaloids with R-configuration at C-3 and no oxygen function at C-6, as in 3a and b), is Ancistrocladus abbreviatus Airy-Shaw, which produced both types of alkaloids (1, 2). More recently, even a "hybrid type" naphthylisoquinoline alkaloid, ancistrobrevine C (2), with an oxygen function at C-6, but 3R-configurated, was isolated from this interesting plant (3). In this paper, we describe the first isolation of the complementary, "inverse hybrid type", alkaloids, dioncoline A (4a) and 7-epi-dioncoline A (4b), with S-configuration at C-3, but lacking an oxygen function at C-6. The new alkaloids 4a and 4b were isolated from freeze-dried stem bark, by extraction with CH3Cl3 and subsequent column and preparative thin layer chromatography on silica gel. Subsequent separation of the two atropisomers was achieved by HPLC on Chiralcel OD (petrol — isopropanol, 90: 10). The 1H-NMR spectra of 4a and 4b are closely related to those of 3a/b, except for the typical downfield shift of the 1-H and 3-H signals, indicating a relative cis-configuration at C-1 vs. C-3. For the determination of the absolute configuration at these stereocenters, we extended our oxidative degradation of 1,3-dimethyltetrahydroisoquinolines (5), now leading to N-methyl-D-alanine (6) and (S)-3-(N-methylamino)butyric acid (5), analyzed by GC, after Mosher-type derivatization. By this method, we could clearly show 4a and 4b to have 1R,3S-configuration, hence 4a and 4b are C-3 epimers of 3a and 3b. The joint occurrence of Ancistrocladaceae- and Dioncophyllaceae-type alkaloids, as well as both imaginable combinations thereof, demonstrates the unconventional synthetic capacities of A. abbreviatus and again underlines its possible chemotaxonomic position between the two families. Ancistrocladus abbreviatus Airy-Shaw is a chemotaxonomically most challenging West-African medicinal plant since it does not only contain typical Ancistrocladaceae-, but also Dioncophyllaceae-type alkaloids (1, 2), and even the mixed, hybrid-type alkaloids ancistrobrevine C (1) (3), which has R-configuration at C-3 and an oxygen function at C-6, and its "inverse counterpart" dioncoline A (2), which is S-configurated at C-3 and lacks an O-functionality at C-6 (4). In this paper, we describe the isolation and structure elucidation of ancistrobrevine D (3a), an additional novel alkaloid from this plant, by spectroscopic and chiroptical methods, by partial and by total synthesis. 1H-NMR spectroscopy, especially NOE-experiments, as well as mass spectrometry, revealed ancistrobrevine D to have a constitution closely related to 1, but with a cis-configurated tetrahydroisoquinoline system and an additional N-methyl substituent. However, its attempted partial synthesis from 1 by reduction and N-methylation gave 3b, a compound diastereomeric to the new alkaloid. The close analogy of the CD-spectra of 3b and ancistrobrevine D gave a first hint at the fact that both compounds do not differ by the configuration at the axis, but at the stereocenters at C-1 (and thus C-3). This was furthermore confirmed by applying our oxidative degradation procedure recently extended to N-methylated tetrahydroisoquinolines (4), showing ancistrobrevine D to be S-configurated at C-3. As a consequence of the very similar chromatographic and spectroscopic behavior of the two diastereomers, and in order to assign the structure of ancistrobrevine D unambiguously, all the four possible cis-configurated stereoisomers 3a—d were prepared by stereoselective total synthesis. By careful comparison of ancistrobrevine D with 3a—3d, by its physical constants {m.p. 172°C, [α]D: +24.9° (CHCl3, c 0.37)}, by 1H-NMR, and by chromatography on a chiral phase (Chiralcel OD), the new alkaloid could clearly be identified as 3a.