Synthesis of 3-Azabicyclo[3.2.0]heptane Derivatives as γ-Aminobutyric Acid Analogues through Intermolecular [2+2] Photocycloaddition

The synthesis of 3-azabicyclo[3.2.0]heptane-6-carboxylic acid and 7-substituted derivatives was developed as bicyclic analogues of -aminobutyric acid. A sensitized, intermolecular [2+2] photocycloaddition of maleic anhydride with N-protected 3-pyrroline served as the key step in these syntheses. Upon transformation of the anhydride function of the primary cycloaddition product, 6-monosubstituted and 6,7-disubstituted 3-azabicyclo[3.2.0]heptane derivatives were obtained.