In solution at room temperature N-(tert-butoxy-carbonyl)-2-phenylglyci
ne, C13H17NO4, shows the presence of two confomers, Z and E in the rat
io 1:3, as a result of restricted rotation about the N-CO bond. In the
solid state, however, only the Z isomer was observed [HN-N-C2-O4 173.
1(4)degrees] with the N-CO bond showing considerable double-bond chara
cter [N-C2 1.357(3) Angstrom].