ERROR opening https://cactus.nci.nih.gov/chemical/structure/OC%28CN%28C%29C%28N%29%3DNP%28O%29%28O%29%3DO%29%3DO/file?format=sdf&get3d=True  -- OC%28CN%28C%29C%28N%29%3DNP%28O%29%28O%29%3DO%29%3DO could not be loaded.