Pt-Al₂O₃ Catalyzed Diastereoselective Hydrogenation Of β-dehydroamino Esters Induced By A Chiral Prosthetic Group

A chiral prosthetic group induced heterogeneous diastereoselective asymmetric hydrogenation ofβ-dehydroamino esters,catalyzed by Pt-Al₂O_3,has been developed.A series ofβ-dehydroamino esters were successfully hydrogenated in high yields with good diastereoselectivities.This method provided a convenient and efficient synthetic way for the preparation of chiralβ-amino acid derivatives,which are key intermediates for bioactive compounds and pharmaceuticals.Diastereoselective hydrogenation ofβ-dehydroamino esters with a chiral prosthetic group was catalyzed by an achiral heterogeneous catalyst,Pt/Al₂O_3,to afford chiral pureβ-amino ester.We researched the effect of the support material of metal catalyst,the structure of ester group,the solvent on the heterogeneous hydrogenation ofβ-dehydroamino esters with a chiral benzyl as the easy-removing the prosthetic group.A series of tert-butylβ-dehydroamino esters were successfully hydrogenated catalyzed by Pt/Al₂O₃（5%,K0343）to affordβ-amino acid in high yields with good diastereoselectivities（dr up to 5.2:94.8）.Furthermore,quantitative conversion could be achieved when gram-scale reaction was conducted.The hydrogenation product could be easily separated by adding maleic acid（1 eq）so that pure single configuration product could be had with>99%de value.