7-Azabicyclo[2.2.1]heptane-7-carboxylic acid,2-[4-[2-[[(1,1-dimethylethyl)dimethylsilyl]oxy]ethyl]-6-methoxy-3-pyridinyl]-2-hydroxy-, 1,1-dimethylethyl ester, (1R,2S,4S)-rel-