ERROR opening https://cactus.nci.nih.gov/chemical/structure/CC1%3DNC2%3DC%28C%28%3DN1%29N%29NC%3DN2/file?format=sdf&get3d=True  -- CC1%3DNC2%3DC%28C%28%3DN1%29N%29NC%3DN2 could not be loaded.