Access to β²-Amino Acids via Enantioselective 1,4-Arylation of β-Nitroacrylates Catalyzed by Chiral Rhodium Catalysts

The highly enantioselective conjugate addition of a variety of arylboronic acids to β-nitroacrylates is reported to provide optically active α-aryl β-nitropropionates in up to 70% yields and >99.5% ee's, which are useful building blocks for preparing chiral β²-amino acids. The applicability of this transformation is demonstrated by converting 3aa into the β²-amino acid 5 and transforming 3ap to β-amino ester 7 via reduction and reductive N-alkylation. The latter compound is a precursor for preparing ent-ipatasertib.