Highly regioselective epoxide hydrogenolysis aiming at the bulgecinine synthesis

The epoxide 4 was submitted to hydrogenolytic conditions cleaving exclusively the C-O bond closer to the phenyl ring (table 1). Along with the desired pyrrolidine 5, the product 6, (C-N benzylic bond cleavage) was isolated (entries 1, 2). Palladium catalyst loading higher than 25mol% (entries 3, 4) resulted in a complete selectivity favoring compound 5. The structures of aminoalcohols 5 and 6 were confirmed by X-ray analysis. After diol protection of 5, the phenyl ring was converted into the acid 7 using Lemieux-von Rudloff Table 1. Hydrogenolysis of epoxypyrrolidine 4