ERROR opening https://cactus.nci.nih.gov/chemical/structure/CNC1%3DNC%28%3DO%29C2%3DC%28N1%29N%3DCN2/file?format=sdf&get3d=True  -- CNC1%3DNC%28%3DO%29C2%3DC%28N1%29N%3DCN2 could not be loaded.