ERROR opening https://cactus.nci.nih.gov/chemical/structure/O%3DC1NC%28%3DO%29N/C2%3DN/C%28%3DO%29NC12O/file?format=sdf&get3d=True -- O%3DC1NC%28%3DO%29N/C2%3DN/C%28%3DO%29NC12O could not be loaded.