ERROR opening https://cactus.nci.nih.gov/chemical/structure/O%3DC2N%28c1ncnc1C%28%3DO%29N2C%29CC%28C%29C/file?format=sdf&get3d=True  -- O%3DC2N%28c1ncnc1C%28%3DO%29N2C%29CC%28C%29C could not be loaded.