4-Amino-8-(3,5-dimethyl-2,4-dioxo(1,3-diazinyl))-6-methylene-1,7-dioxa-9-(1,1,2,2-tetramethyl-1-silapropoxy)-2-thiaspiro[4.4]non-3-ene-2,2-dione AIDS-057901 AIDS057901 TSAO deriv.