Crystal structures of N-parabromobenzoyl-α-aminoisobutyric acid and two derivatives

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Abstract
The crystal structures of N-para-bromobenzoyl-α-aminoisobutyric acid (1), and its 5(4H)-oxazolone (2) and methyl ester (3) derivatives have been determined by X-ray diffraction techniques. The compounds possess the following parameters: (1) monoclinic, space group P21/a, a = 10.057(4), b = 12.733(4), c = 9.706(4) Å, β = 99.8(3)°, and Z = 4; (2) monoclinic, P21/a, a = 12.637(4), b = 7.818(3), c = 12.241(4) Å, β = 110.7(2)°, and Z = 4;(3) orthorhombic Pcab, a = 17.615(5), b = 14.357(5), c = 10.251(4) Å, Z = 8. The crystal structures were solved by direct methods. The least-squares refinements led to R values of 0.067, 0.047 and 0.048 for 1205, 1510 and 734 reflections with I > 3 σ(I) for 1 – 3, respectively. The conformation of compounds (1) and (3) is remarkably similar, with a trans amide bond and folding about the N – αC bond. The C = N bond of the oxazolone group of compound (2) is not conjugated with the ester moiety.

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