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—H⋯O and N—H⋯O) involving the carboxylic acid, the benzamido and the methyl ester groups.
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Buñuel et al. (1996) studied this question.