ABSTRACT
The Rh-catalyzed asymmetric hydrogenation of acetamidoacrylates 1 has become an important process for the preparation of natural and unnatural amino acid derivatives 2 (eq. 1). A plethora of useful chiral ligands including DIOP, DIP AMP, Chiraphos, BINAP, DuPHOS and others has been developed over the past quarter century which provide good to excellent enantioselectivities.1,2 The preparation of unnatural amino acids with high enantioselectivity continues to be important to the pharmaceutical industry as these species can serve as intermediates in the production of bulk drug substances. In addition, these unnatural amino acids are especially useful in combinatorial chemistry as more diversity is achievable and compounds which may provide better pharmacological stability can be prepared. Thus, the development of new and better methods for the preparation of unnatural amino acids will continue to be of importance from both an academic and industrial perspective.
