4-Amino-8-(2,4-dioxo(1,3-diazaperhydroinyl))-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-057904 AIDS057904 TSAO deriv.