A new conformationally restricted aspartic acid analogue with a bicyclo[2.2.2]octane skeleton

Abstract

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-C[alpha]([varphi]) and C[alpha]-CO([psi]) 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.