ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C4H4O2/c5-4-2-1-3-6-4/h1-2H,3H2/file?format=sdf&get3d=True  -- InChI=1S/C4H4O2/c5-4-2-1-3-6-4/h1-2H,3H2 could not be loaded.