Effective Biomimetic Route to D(+)-Pantothenate Using Asymmetric Hydrogenation Catalyzed by a Chiral Rhodium Complex in the Key Step

Asymmetric synthesis of D(+)-pantothenate from ketopantoyl lactone following a biomimetic route using asymmetric hydrogenation in the key step is described. The asymmetric hydrogenation of ketopantoyl lactone was effectively catalyzed by a rhodium complex with BPPM as chiral ligand to afford D(-)-pantoyl lactone with 86.7% optical purity under optimum conditions. This was further recrystallized to give the pure lactone in good yield. The pure D(—)-pantoyl lactone thus obtained was converted to ethyl D(+).pantothenate by reacting with β-alanine ethyl ester.