β-Hydroxynorbornane amino acid derivatives: valuable synthons for the diastereoselective preparation of substituted cyclopentylglycine derivatives

The behaviour towards the retro-aldol or retro-Dieckmann reactions of several norbornene and norbornane amino acids functionalized with an oxygen atom at C-β and characterized by different features, such as the substitution pattern and the constraints, was investigated. By C2–C3 disconnection new differently functionalized cyclopentenyl- and cyclopentylglycines were prepared. This synthetic approach allows to control the stereochemistry from two to four stereocentres depending on the starting norbornane derivative and affords, for each derivative, a couple of epimeric compounds at amino acid stereocentre. Depending on the features of the starting reagent and of the reaction conditions, a partial control of the stereochemistry of the amino acid carbon atom is also possible.