(4-((Tert-butyl(dimethyl)silyl)oxy)-2-(((tert-butyl(dimethyl)silyl)oxy)methyl)-5-(2,4-dioxo-3,4-dihydro-1(2H)-pyrimidinyl)-4,5-dihydro-3-furanyl)acetonitrile AIDS-161520 AIDS161520 NSC697603