1. Development of a rapid, room-temperature dynamic kinetic resolution for efficient asymmetric synthesis of alpha-aryl amino acids
Jianfeng Hang, Hongming Li, Li Deng Org Lett. 2002 Sep 19;4(19):3321-4. doi: 10.1021/ol026660l.
[reaction: see text] A rapid, highly efficient and general dynamic kinetic resolution (DKR) of racemic alpha-aryl UNCAs with the dual-function catalysis of modified cinchona alkaloid was accomplished at room temperature. This DKR led to the development of a highly enantioselective catalytic method for the practical synthesis of a wide range of alpha-aryl and alpha-heteroaryl amino acids in 89-92% ee and 86-95% yield from racemic UNCAs.
2. A highly diastereoselective and enantioselective synthesis of polysubstituted pyrrolidines via an organocatalytic dynamic kinetic resolution cascade
Tao Cheng, Sixuan Meng, Yong Huang Org Lett. 2013 Apr 19;15(8):1958-61. doi: 10.1021/ol4006129. Epub 2013 Apr 8.
Highly functionalized pyrrolidine and piperidine analogues, with up to three stereogenic centers, were synthesized in good yield (50-95%), excellent dr (single isomer), and high ee (>90%) using a Cinchona alkaloid-derived carbamate organocatalyst. High stereoselective synergy was achieved by combining a reversible aza-Henry reaction with a dynamic kinetic resolution (DKR)-driven aza-Michael cyclization. Whereas both reactions proceed with moderate enantioselectivities (50-60% for each step), high enantioselectivities are obtained for the overall products devoid of dr sacrifice.
3. Diastereo- and enantioselective anti-selective hydrogenation of α-amino-β-keto ester hydrochlorides and related compounds using transition-metal-chiral-bisphosphine catalysts
Yasumasa Hamada Chem Rec. 2014 Apr;14(2):235-50. doi: 10.1002/tcr.201300032. Epub 2014 Feb 18.
This review describes our recent works on the diastereo- and enantioselective synthesis of anti-β-hydroxy-α-amino acid esters using transition-metal-chiral-bisphosphine catalysts. A variety of transition metals, namely ruthenium (Ru), rhodium (Rh), iridium (Ir), and nickel (Ni), in combination with chiral bisphosphines, worked well as catalysts for the direct anti-selective asymmetric hydrogenation of α-amino-β-keto ester hydrochlorides, yielding anti-β-hydroxy-α-amino acid esters via dynamic kinetic resolution (DKR) in excellent yields and diastereo- and enantioselectivities. The Ru-catalyzed asymmetric hydrogenation of α-amino-β-ketoesters via DKR is the first example of generating anti-β-hydroxy-α-amino acids. Complexes of iridium and axially chiral bisphosphines catalyze an efficient asymmetric hydrogenation of α-amino-β-keto ester hydrochlorides via dynamic kinetic resolution. A homogeneous Ni-chiral-bisphosphine complex also catalyzes an efficient asymmetric hydrogenation of α-amino-β-keto ester hydrochlorides in an anti-selective manner. As a related process, the asymmetric hydrogenation of the configurationally stable substituted α-aminoketones using a Ni catalyst via DKR is also described.
