(±)-Bicoryanhunine A, dimeric benzylisoquinoline alkaloid atropo-enantiomers from Corydalis yanhusuo

Bicoryanhunine A (1), isolated from the dried tubers of Corydalis yanhusuo, is the first novel dimeric benzylisoquinoline alkaloid with a 4,7′-coupled biaryl axis. This novel C-4-C-7′ linkage lead to the highest steric hindrance at the biaryl axis, giving rise to a pair of atropo-enantiomers that are well resolved into the anticipated enantiomers, (+)-bicoryanhunine A (1) and (−)-bicoryanhunine A (1), with the help of chiral-phase HPLC. Their structures including the axial configurations were elucidated by spectroscopic methods and experimental and calculated ECD investigations. Bicoryanhunine A (1) was a moderate PD-1/PD-L1 interaction inhibitor with an IC50 value of 14.3 ± 0.67 μM.