AbstractGuan‐fu base G is a new alkaloid isolated from root tuber ofAconitum coreanumLe'vl Raipaics. Guan‐fu base G methyliodide crystallizes in orthorhombic system, space groupD4/2‐P212121, with dimensions:a= 16.87Å,b= 16.93Å,c= 10.09Å;Z= 4. The three dimensional data were collected on a Phillips PW‐1100 four‐circle diffractometer with MoKaradiation.The structure was solved by heavy‐atom method and subsequently successive Fourier syntheses. The structure was refined by block‐diagonal matrix least squares methods toR= 0.0578 for 2848 reflexions. The absolute configuration was determined by computation of theRfactor for the two possible configurations using anomalous scat