1-Pyrrolidinecarboxylic acid,3-[(S)-[(4R)-2,2-dimethyl-1,3-dioxolan-4-yl]hydroxymethyl]-5-[(S)-[(4R)-2,2-dimethyl-1,3-dioxolan-4-yl][(trimethylsilyl)oxy]methyl]-2-oxo-,1,1-dimethylethyl ester, (3S,5R)-