Crystal structure and conformational flexibility of 2-(acetylamino)prop-2-enoic acid (N-acetyldehydroalanine)

The molecular structure of N-acetyldehydroalanine (2-acetylaminoprop-2-enoic acid) has been determined from three-dimensional X-ray data. C5H7NO3 is monoclinic, space group P21/n, with Z= 4 in a cell of dimensions a= 14.904(7), b= 10.162(6), c= 3.943(3)Å, β= 91.7(1)°. The structure was solved by direct methods and refined by full-matrix least-squares to R 0.060 for 1 350 observed reflections. The molecules exhibit a fully planar conformation and are linked by OH ⋯ O hydrogen bonds to form one-dimensional chains. The conformational flexibility is discussed on the basis of ab initio and empirical calculations.