Ethyl 1-formamido-4-oxo-2,6-diphenylcyclohexanecarboxylate

In the title compound, C22H23NO4, the central six-membered ring is in a twist-boat conformation, the two aryl groups are in equatorial positions and the dihedral angle between the two aromatic rings is 75.98 (12)°.

In the title compound, C 22 H 23 NO 4 , the central six-membered ring is in a twist-boat conformation, the two aryl groups are in equatorial positions and the dihedral angle between the two aromatic rings is 75.98 (12) .
Financial support of this research by the NNSFC (20872015), the Science Foundation for Young Teachers of NENU (20090404) and the Young Scientific Research Foundation of Jilin Province (20090149) is gratefully acknowledged.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NC2214).

Comment
The cyclic constrained analogues of phenylalanine (Phe) are of particular interest in the construction of peptide analogues with controlled fold in the backbone, because they play an important role in both restricting torsional angle χ1 and peptide receptor recognition processes (Cativiela et al. 1998;Cativiela et al. 2000. Cativiela et al. 2007Cativiela et al. 2009;Lasa et al. 2006). The crystal structure of title compound, a phenyl substituted highly constrained cyclohexane analogue of Phe, is reported in this paper.
In the crystal structure the central six-membered ring is in a twist conformation which can presumably traced back due to steric hindrance of the ethoxyl carbonyl, the amide and the two aryl groups (Fig. 1). The two aryl groups are located in equatorial positions and the dihedral angle between two aromatic rings amount to 75.98 (12)°.

Refinement
The N-bound H atom was located in a difference map, fixed at this position and refined as riding with Uiso(H) = 1.2Ueq(N).
The remaining hydrogen atoms were placed in ideal positions (C-H = 0.93-0.98 Å) and refined as riding with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C). The methyl groups were allowed to rotate, but not to tip. Fig. 1. View of the molecular structure of the title compound with labeling and displacement ellipsoids drawn at the 30% probability level.