2-Oxa-5-azabicyclo[2.2.1]heptane-5-carboxylic acid, 3-(3,4-dihydro-5-methyl-2,4-dioxo-1(2H)-pyrimidinyl)-7-(phenylmethoxy)-1-[(phenylmethoxy)methyl]-, phenylmethyl ester, (1R,3R,4R,7S)-