9-((tert-Butyl(dimethyl)silyl)oxy)-6-(((tert-butyl(dimethyl)silyl)oxy)methyl)-8-(2,4-dioxo-3,4-dihydro-1(2H)-pyrimidinyl)-7-oxa-1-thia-4-azaspiro[4.4]nonane-3-carboxamide 1-oxide AIDS-152705 AIDS152705 NSC697596