ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI%3DInChI%3D1S/C4H8O2/c1-2-6-4-3-5-1/h1-4H2/file?format=sdf&get3d=True  -- InChI%3DInChI%3D1S/C4H8O2/c1-2-6-4-3-5-1/h1-4H2 could not be loaded.