synthesis of a series of α-fluorinated β²- and β³-amino acid derivatives is described. Stereoselective fluorination at the α-carbon of the β³-amino acids was achieved by deprotonation with lithium diisopropylamide followed by treatment with N-fluorobenzenesulfonimide. Fluorination of β²-amino acids employed the chiral auxiliary (4R)-4-benzyl-2-oxazolidinone. The α-fluorinated amino acids and their non-fluorinated
Aminomethylation of Enals through Carbene and Acid Cooperative Catalysis: Concise Access to β<sup>2</sup>-Amino Acids
作者:Jianfeng Xu、Xingkuan Chen、Ming Wang、Pengcheng Zheng、Bao-An Song、Yonggui Robin Chi
DOI:10.1002/anie.201412132
日期:2015.4.20
organocatalytic asymmetric aminomethylation of α,β‐unsaturated aldehydes by N‐heterocyclic carbene (NHC) and (in situ generated) Brønsted acid cooperative catalysis is disclosed. The catalytically generated conjugated acid from the base plays dual roles in promoting the formation of azolium enolate intermediate, formaldehyde‐derived iminium ion (as an electrophilic reactant), and methanol (as a nucleophilic