2,4(1H,3H)-Pyrimidinedione,1-[(6S,8R,9R)-4-amino-9-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-1-methyl-2,2-dioxido-6-[(phenylmethoxy)methyl]-7-oxa-2-thia-1-azaspiro[4.4]non-3-en-8-yl]-3,5-dimethyl-