Linear Oligopeptides .245. Crystal and Molecular-structures of 2 N-carboxy Anhydrides of C-alpha,alpha-disubstituted Glycines

The crystal and molecular structures of 4,4-diethyl-oxazolidine-2,5-dione (1) and 3-(2'-nitrophenylsulfenyl)-4,4-di-n-propyl-oxazolidine-2,5-dione (2) have been determined by X-ray diffraction. The compounds possess the following parameters: (1) monoclinic, space group P2(1)/n (No. 14), a = 8.931(1) angstrom, b = 11.749(2) angstrom, c = 7.867(1) angstrom, beta = 98.0(2)-degrees, and Z = 4; (2) triclinic, space group P1BAR (No. 2), a = 12.187(2) angstrom, b = 9.588(1) angstrom, c = 7.681(1) angstrom, alpha = 72.9(2)-degrees, beta = 73.0(2)-degrees, gamma = 84.9(2)-degrees, Z = 2. The crystal structures were solved by direct methods. The least-squares refinements led to R values of 0.040 and 0.039 for 1144 and 2068 reflections with F greater-than-or-equal-to 7-sigma(F) for (1) and (2), respectively. The molecules of (1) are linked by intermolecular N1-H1...O2 = C2 hydrogen bonds along the y direction. The difference observed between the C1-O1 and C2-O1 distances within the heterocyclic moiety of (1) is not found in (2).