143615-00-3Relevant articles and documents
Utilization of (18-Crown-6)-2,3,11,12-tetracarboxylic Acid as a Chiral NMR Solvating Agent for Diamines and β-Amino Acids
Rodriguez, Yolanda C.,Duarte, Tayla M.,Szakonyi, Zsolt,Forr?, Eniko,Fül?p, Ferenc,Wenzel, Thomas J.
, p. 708 - 715 (2015/10/12)
The compound (18-crown-6)-2,3,11,12-tetracarboxylic acid was evaluated as a chiral nuclear magnetic resonance (NMR) solvating agent for a series of diamines and bicyclic β-amino acids. The amine must be protonated for strong association with the crown ether. An advantage of (18-crown-6)-2,3,11,12-tetracarboxylic acid over many other crown ethers is that it undergoes a neutralization reaction with neutral amines to form the protonated species needed for binding. Twelve primary diamines in neutral and protonated forms were evaluated. Diamines with aryl and aliphatic groups were examined. Some are atropisomers with equivalent amine groups. Others have two nonequivalent amine groups. Association equilibria for these systems are complex, given the potential formation of 2:1, 1:1, and 1:2 crown-amine complexes and given the various charged species in solution for mixtures of the crown ether with the neutral amine. The crown ether produced enantiomeric differentiation in the 1H NMR spectrum of one or more resonances for every diamine substrate. Also, a series of five bicyclic β-amino acids were examined and (18-crown-6)-2,3,11,12-tetracarboxylic acid caused enantiomeric differentiation in the 1H NMR spectrum of three or more resonances of each compound. Chirality 27:708-715, 2015.
Rhodium-catalyzed enantioseletive hydrogenation of tetrasubstituted α-acetoxy β-enamido esters: A new approach to chiral α-hydroxyl-β-amino acid derivatives
Wang, Qingli,Huang, Wenhua,Yuan, Haoquan,Cai, Qin,Chen, Liming,Lv, Hui,Zhang, Xumu
, p. 16120 - 16123 (2015/02/18)
Asymmetric hydrogenation of tetrasubtitued α-acetoxy β-enamido esters with rhodium catalysts based on chiral diphosphine ligands provides an efficient and concise route to the synthesis of chiral α-hydroxyl-β-amino acid derivatives in excellent enantioselectivities. The products are valuable chiral building blocks in many biologically active compounds and have important applications in organic synthesis.
Highly diastereoselective and enantioselective synthesis of α-hydroxy β-amino acid derivatives: Lewis base catalyzed hydrosilylation of α-acetoxy β-enamino esters
Jiang, Yan,Chen, Xing,Zheng, Yongsheng,Xue, Zhouyang,Shu, Chang,Yuan, Weicheng,Zhang, Xiaomei
, p. 7304 - 7307 (2011/09/16)
By design: A series of α-acetoxy-β-enamino esters 1 were synthesized and then subjected to catalytic asymmetric hydrosilylation. In the presence of a chiral Lewis base catalyst, the reactions proceeded smoothly to provide a wide range of chiral α-acetoxy β-amino acid derivatives in high yields with good diastereoselectivities and enantioselectivities. Copyright