Mucroniferanines A–G, Isoquinoline Alkaloids from Corydalis mucronifera

Five pairs of isoquinoline alkaloid enantiomers, mucroniferanines A–E (1–5), two inseparable epimeric pairs, mucroniferanines F and G (6, 7), and 10 known isoquinoline alkaloids (8–17) were obtained from Corydalis mucronifera. The structures were characterized using spectroscopic data analysis, and the absolute configurations were established by ECD and X-ray data analysis. The new compounds except for 3 possess a rare 9-methyl group in the isoquinoline alkaloids, and compounds 2 and 3 possess rare benzo­[1,2-d:3,4-d]­bis­[1,3]­dioxole moieties. It is the first report of stereoisomerism involving the 9-methyl phthalideisoquinoline alkaloids. Compounds (−)-4, 6, and 7 exhibited acetylcholinesterase inhibitory activities with IC50 values of 28.3, 12.2, and 11.3 μM, respectively.