Stereodivergent synthesis of two novel -aminophosphonic acids characterized by a cis-fused octahydroindole system

The synthesis of two new -aminophosphonic acids, namely (2S*,3aS*,7aS*)and (2R*,3aS*,7aS*)-octahydroindole-2phosphonic acids, is described. They are analogues of phosphoproline bearing a cyclohexane ring fused to the pyrrolidine moiety. The ring junction presents a cis stereochemistry in both cases, whereas the two compounds differ in the relative orientation of the cyclohexane and phosphonate moieties. The two amino acids have been prepared from a common starting material following stereodivergent routes that provide the desired stereoisomer with complete stereocontrol. The relative configuration of the compounds synthesised has been confirmed by X-ray diffraction analysis.