Eerberis buxifolia Lam. (Berberidaceae) has yielded the new bisbenzylisoquinolines chillanamine (3) and (-)-osornine (4), as well as the new secobisbenzylisoquinolines (- )-curacautine (10) and (-)-takamine (11). Cleavage of (-)-0-methylosornine (5) with sodium in liquid ammonia led to tetrahydrobenzylisoquinolines (+)-6 and (-)-7. A close relative of (-)-osornine is the known calafatine (l), now reisolated from E. buxifolia. This alkaloid is levo- rather than dextro-rotatory, and its sodium-in-liquid-ammonia cleavage provided (+)-8 and (-)-9. Potassium permanganate oxidation of 1 gave rise to 10. Biogenetic considerations imply that two N-methylcoclaurines first combine in tail-to-tail fashion. The resulting dimer is then oxidized enzymically ortho to the diary1 ether bridge to supply the C-10 oxygenated function. 0-Methylation at an appropriate stage furnishes 3. Alkaloid 3 is the likely precursor of 4 and 1. The latter suffers oxidative cleavage to (-)-curacautine, which can then be transformed into (-)-takamine.