ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C4H8O2/c5-4-1-2-6-3-4/h4-5H,1-3H2/file?format=sdf&get3d=True  -- InChI=1S/C4H8O2/c5-4-1-2-6-3-4/h4-5H,1-3H2 could not be loaded.