8-Azabicyclo[3.2.1]oct-2-ene-8-carboxylic acid,4-[1-[[(1,1-dimethylethyl)dimethylsilyl]oxy]ethyl]-3-[[(trifluoromethyl)sulfonyl]oxy]-, 1,1-dimethylethyl ester, (1R,4S,5S)-