Conformational switching caused by biphenyl substitution at the Calpha position: ethyl 2-benzyl-2-(formylamino)-3-phenylpropionate and ethyl 3-(1,1'-biphenyl-4-yl)-2-(formylamino)-2-(4-phenylbenzyl)propionate.

The title compounds, C19H21NO3 and C31H29NO3, are derivatives of alpha-aminoisobutyric acid, with benzyl and dibenzyl substitution. The pseudo-peptide formed by the N-formyl and ethyl ester substitution at the Calpha position switches from a trans-trans to a trans-cis configuration as a result of biphenyl substitution. The packing of the compounds is stabilized by N-H...O and C-H...O hydrogen bonds.