THE X-RAY ANALYSIS OF AN ENAMINONE WITH A BULKY SUBSTITUENT. María Jesús Diánez, María Dolores Estrada, Amparo López-Castro and Simeón Pérez-Garrido. Instituto de Ciencias de Materiales de Sevilla y Departamento de Física de la Materia Condensada, C.S.I.C.-Universidad de Sevilla. Apartado 1065, 41080 Sevilla, Spain
The structure of 2,3,4-tri-O-benzoyl-N-(2,2-diethoxycarbonylvinyl)-(-L-ramno-pyranosylamine has been studied to determine its conformation, which has aroused interest as an "enaminone" as well as for the bulky substituent. X-ray crystallography results on a few other polarized ethylenes and related compounds have been reported (Diánez et al., 1985 and 1988). Crystal data are: C35H34NO11, Mr=644.7, orthorhombic, P212121, a=12.300(2), b=29.422(5), c=9.736(2)Å, V=3523.4Å3, Z=4, Dm=1.21 Dx=1.22Mgm-3, ((MoK()=0.7169Å, u=0.085mm-1, F(000)=1356, T=293K. The structure was solved by direct methods and isotropic refinement by full-matrix least squares methods for non-H atoms (H atoms were included with Uiso but not refined) to a final R(F)=0.10 and R(F2)=0.08 for 1589 observed reflections with I(2((I0). The resonance system, with distances 1.374 for N-C, 1.386 for C=C, 1.443 and 1.449 for C-C bonds , 1.198 and 1.200 for the two C=O and 1.342 and 1.346Å for the C-O bonds, revealed a limited electron delocalization in the carbonylvinylamino group. This group has the Z configuration and is planar (maximum deviation 0.093Å) and one of the ethoxycarbonyl group is tilted -0.7[[ordmasculine]]. The C-C distances in the pyranose ring are in the range 1.486-1.546Å and the glycosid C-O linkage are C5-O1=1.428 and O1-C1=1.442Å. The exocyclic C-O lengths have a mean value of 1.427Å, C-CH3, 1.514 and C-N, 1.459Å. The interior and exterior ring angles are consistent with the expected high degree of tetrahedrality. The molecular conformation of the pyranose ring is a chair 1C4 with puckering parameters (=10[[ordmasculine]], (=91[[ordmasculine]], Q=0.57Å. The substituents confirms the (-L configuration. Packing of the molecule is governed by van der Waals forces. There is one intramolecular H-bond [N1-H...O11'=2.546Å] which reflects the chelated structure.