Systematical NMR analysis of swainsonine,a mycotoxin from endophytic fungus Alternaria oxytropis

Swainsonine (SW, 1 ), a unique indolizine with poly‐hydroxyl groups, was re‐isolated from the plant endophytic fungus Alternaria oxytropis. The structure (including planar structure and relative configuration) was systematically elucidated by NMR spectra (including ¹H, ¹³C, ¹H‐¹H COSY, HMQC, HMBC, and NOESY spectra in DMSO‐d₆ and in CD₃OD); ¹H NMR spectra of the modified Mosher's products were first used to determine the absolute configuration of SW. More importantly, the complex coupled features of H‐7α, H‐7β, and H‐6α in the ¹H NMR spectrum of ( 1 ) were analyzed in details, which will provide aids for the planar and relative configuration determination of analogs.