ERROR opening https://cactus.nci.nih.gov/chemical/structure/O%3DC%28O%29C%28NCCNC%28c1ccccc1O%29C%28%3DO%29O%29c2ccccc2O/file?format=sdf&get3d=True -- O%3DC%28O%29C%28NCCNC%28c1ccccc1O%29C%28%3DO%29O%29c2ccccc2O could not be loaded.