Carbohydrates as chiral templates: asymmetric ugi-synthesis of alpha-amino acids using galactosylamines as the chiral matrices
作者:Horst Kunz、Waldemar Pfrengle
DOI:10.1016/s0040-4020(01)86054-3
日期:1988.1
recrystallisation pure (R)-amino acid derivatives 5 are obtained in yields of 80–95%. In addition to the high yields and stereoselectivity the amino acid synthesis discribed here has the further advantage that it neither requires organometallic reagents and intermediates nor exclusion of oxygen and moisture. Two step acid hydrolysis of the N-galactosylamino acid amide derivatives 5 delivers the enantiomerically
Catalytic Asymmetric Allenylation of Malonates with the Generation of Central Chirality
作者:Qiankun Li、Chunling Fu、Shengming Ma
DOI:10.1002/anie.201204346
日期:2012.11.19
Water plays an important role in a palladium‐catalyzed allenylation of diethyl malonate with 2,3‐allenyl acetates to yield centrallychiral allenyl malonates bearing synthetically useful functional groups (see scheme). The products were formed with 92–96 % ee in the presence of a bulky, electron‐rich biphenyl ligand at room temperature.
propargylic position resemble the sidechain present at the Cα of amino acids. Whereas propargylamines with (cyclo)alkyl substituents can be prepared in a direct manner, residues with polar functional groups require suitable protective groups. The presence of particular functional groups in the sidechain in some cases leads to remarkable side reactions of the alkyne moiety. Thus, electron-withdrawing substituents
A newseries of sulfonated triarylphosphines with a strong π-acceptor character were synthesized by direct sulfonation of trifluoromethylated neutral phosphines. Due to the deactivating character of the trifluoromethyl group, high oleum concentration and the use of boric acid to prevent phosphine oxidation were required for the sulfonation step. The new sulfonated phosphines are water-soluble and more