A Versatile Route to syn‐ and anti‐α‐Amino β‐Hydroxy Esters from β‐Keto Esters by Dynamic Kinetic Resolution with Ru‐SYNPHOS® Catalyst
A general and practical synthesis of both syn- and anti-α-amino β-hydroxy esters with high levels of selectivity by the use of Ru-SYNPHOS® catalysts is reported. The key transformations include asymmetric hydrogenations of α-N-substituted β-keto esters protected as α-amido or α-amino hydrochloride derivatives, respectively. The RuII-catalyzed hydrogenation of α-amino β-keto ester hydrochlorides affords the corresponding anti-α-amino β-hydroxy esters with high diastereoselectivities (up to 99%) and enantioselectivities (up to 97%) through dynamic kinetic resolution (DKR). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)