It appears safe to say that NMR and X-ray NMR Practice Problems meric Natural Product Stru But steady state conformation can be addressed in the solid state by X-ray crystallography and in solution by NMR. 基于3J值的构型分析 3-H,dd.J-10.5Hz J=3.8 分 1.How to distinguish following two structures? Ha c-c CI COOC2Hs COOCzHs NOE:Irradiate CH,Ha峰面积增加16% CC=C c-c Ha Hac NOE:Irradiate CH Ha峰面积不变 66 430 It appears safe to say that NMR and X-ray crystallography are now the two most important tools of non-polymeric Natural Product Structure analysis. But steady state conformation can be addressed in the solid state by X-ray crystallography and in solution by NMR. 431 NMR Practice Problems School of Pharmaceutical Sciences Hebei Medical University 432 HO H 1 2 3 4 5 基于3J值的构型分析 433 CH3 H H H CH3 H HO CH3 CH3 H OH H CH3 H H CH3 1 2 3 J = 10 Hz J = 5 Hz J = 3.8 Hz J = 3.8 Hz HO H 3-H, dd, J = 10, 5 Hz 3-H, dd, J = 3.8, 3.8 Hz 1 2 3 4 5 434 C C H COOC2H5 H3C Cl C C H H COOC2H5 3C Cl 1. How to distinguish following two structures? 435 C C Ha COOC2H5 H3C Cl NOE：Irradiate CH3, Ha峰面积增加16% C C Ha H COOC2H5 3C Cl NOE：Irradiate CH3, Ha峰面积不变