ERROR opening https://cactus.nci.nih.gov/chemical/structure/C1%3DC2C%28%3DNC%28%3DO%29NC2%3DO%29NN1/file?format=sdf&get3d=True  -- C1%3DC2C%28%3DNC%28%3DO%29NC2%3DO%29NN1 could not be loaded.