2-Pyrrolidinone,3,4-bis[[(1,1-dimethylethyl)dimethylsilyl]oxy]-5-[(4R,5S)-5-[(1S)-2-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-1-[(methylsulfonyl)oxy]ethyl]-2,2-dimethyl-1,3-dioxolan-4-yl]-, (3R,4S,5S)-