4-Amino-8-[3-(3-{3-[5-(hydroxymethyl)(2-2,5-dihydrofuryl)]-2,6-dioxo(1,3-dihydropyrimidin-4-yl)}prop-2-ynyl)-5-methyl-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-122977 AIDS122977