A New Conformationally Restricted Aspartic Acid Analogue with a Bicyclo[2.2.2]octane Skeleton

The bicyclo[2.2.2] octane cage in (2R,3S)-3-benzamido-3-methoxycarbonylbicyclo­[2.2.2]octane-2-carboxylic acid, C₁₈H₂₁NO₅, has approximate D₃ symmetry and the three six-membered rings of this fragment all deviate slightly from ideal boat conformations. The values determined for the torsion angles about the N—Cα(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—HO and N—HO) involving the carboxylic acid, the benzamido and the methyl ester groups.