2-Amino-9-[(2R,3R,3aR,7aR,9R,10S,10aR,14aR)-2-(6-amino-9H-purin-9-yl)-10-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-3-fluorododecahydro-5-hydroxy-5,12,12-trioxidocyclopenta[k]furo[2,3-e][1,7,9,2,3,8]trioxathiaazaphosphacyclododecin-9-yl]-1,9-dihydro-6H-purin-6-one