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