ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C6H18N4/c7-1-4-10(5-2-8)6-3-9/h1-9H2/file?format=sdf&get3d=True -- InChI=1S/C6H18N4/c7-1-4-10(5-2-8)6-3-9/h1-9H2 could not be loaded.