ERROR opening https://cactus.nci.nih.gov/chemical/structure/CN1C%3DNC2%3DC1C%28%3DO%29N%28C%28%3DO%29N2C%29C/file?format=sdf&get3d=True  -- CN1C%3DNC2%3DC1C%28%3DO%29N%28C%28%3DO%29N2C%29C could not be loaded.