α-Amino Acid Derivatives by Enantioselective Decarboxylation
作者:Henri Brunner、Markus A. Baur
DOI:10.1002/ejoc.200300206
日期:2003.8
The methodology of enantioselective decarboxylation was applied to 2-aminomalonic acidderivatives in order to obtain enantio-enriched amino acidderivatives. Full conversion was achieved stirring racemic N-acetylated 2-aminomalonic hemiesters in THF at 70 °C with 10 mol % of a chiral base for 24 h. The catalyst may be recycled. Whereas the commercially available cinchona alkaloids gave poor results
Enantioenriched pipecolic esters were prepared in good yields in the decarboxylation, at room temperature, of N-protected piperidinohemimalonates catalyzed by cinchona alkaloids. Enantiomeric excesses as high as 72% were obtained when using 9-epi-cinchonine and the N-benzoyl substituted piperidinohemimalonate. A detailed study of the different reaction parameters revealed that the selectivity of this
A novel amino-thiocarbamate-catalyzed bromolactonization of unsaturated carboxylic acids has been developed. The scope of the reaction is evidenced by 22 examples of gamma-lactones with up to 99% yield and 93% ee. The protocol was applied in the enantioselective synthesis of the key intermediates of VLA-4 antagonists.
Ultra‐Fast Continuous‐Flow Photo‐Thiol‐Ene Functionalization of Conformation‐Controlled Cinchona Alkaloids
作者:Kouakou Eric Konan、Abollé Abollé、François‐Xavier Felpin
DOI:10.1002/ejoc.202201055
日期:2023.1.2
Ultra-fast continuous-flow photo-thiol-ene reactions on cinchonaalkaloids are possible through a fine control of the reactive conformation in solution. Switching the hydroxyl group at C9 by a phenyl carbamate allows thiol-ene functionalization of cinchonaalkaloids in less than 2.5 minutes with organic thiols at 32 °C ant under light irradiation at 365 nm.