8-(3,5-Dimethyl-2,4-dioxo(1,3-dihydropyrimidinyl))-1,7-dioxa-9-(1,1,2,2-tetramethyl-1-silapropoxy)-6-[(1,1,2,2-tetramethyl-1-silapropoxy)methyl]-2-thiaspiro[4.4]non-3-ene-2,2-dione AIDS-112336 AIDS112336