Novel Disaccharide Chiral Ligands Derived from α,α-Trehalose and Their Applications to Asymmetric Hydrogenation of Enamides

Abstract

Abstract New chiral diphosphinite ligands such as 4,6 : 2′,3′ : 4′,6′-tri-O-cyclohexylidene-2,3-di-O-diphenylphosphino-α,α-trehalose (1), 3,3′-di-O-benzyl-4,6 : 4′,6′-di-O-benzylidene-2,2′-di-O-diphenylphosphino-α,α-trehalose (2), 4,6 : 4′,6′-di-O-benzylidene-2,2′-di-O-diphenylphosphino-3,3′-di-O-methyl-α,α-trehalose (3), and 2,2′-di-O-benzyl-4,6 : 4′,6′-di-O-benzylidene-3,3′-di-O-diphenylphosphino-α,α-trehalose (4) were prepared from α,α-trehalose which is an inexpensive natural reserve sugar. These ligands work as chiral ligands for Rh-catalyzed hydrogenation of α-acetamidoacrylic and cinnamic acid derivatives to afford both enantiomers of amino acids up to 84%ee (S) and 72%ee (R).