A New Conformationally Restricted Aspartic Acid Analogue with a Cyclohexanone Skeleton

In the compound (1R,2S)-2-benzamido-2-methoxycarbonyl-5-oxocyclohexane-1-carboxylic acid, C 16 H 17 NO 6 , the cyclohexanone ring adopts a distorted chair conformation. The carboxylic acid and the methyl ester groups occupy the axial positions, while the benzamido group is equatorial. The values determined for the torsion angles about the N-C α (φ) and Cα-CO(ψ) bonds correspond to a semi-extended conformation for the amino acid residue. The crystal structure is stabilized by two intermolecular hydrogen bonds (O-H...O and N-H...O) involving the carboxylic acid, the benzamido and the methyl ester groups.