Asymmetric synthesis of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740)

The asymmetric synthesis of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740) 1, a potent and selective group 2 mGluR agonist, has been accomplished starting from the readily available enantiomerically pure cyclopentenone 4. Thus, cyclopropanation with ethyl(dimethylsulfuranylidene)acetate generated in situ with DBU, followed by deketalization gave rise to the dihydroxy bicyclic ketone 9. After protecting the ketone as 1,3-dioxolane and its transformation to the orthoformate 11, this was pyrolytically deoxygenated in a sealed tube to the bicyclic enone 13. The synthesis was completed after hydrogenation, stereoselective Bucherer-Bergs reaction and hydantoin hydrolysis, yielding LY354740 (+)-1 with an e.e. ≥98%.