Asymmetric syntheses of N-substituted α-amino esters via dynamic kinetic resolution of α-haloacyl diacetone-d-glucose
作者:Hyun Jung Kim、Yongtae Kim、Eui Ta Choi、Min Hee Lee、Eun Sun No、Yong Sun Park
DOI:10.1016/j.tet.2006.04.045
日期:2006.6
Diacetone-d-glucose or d-allose mediated dynamic kinetic resolution of α-halo esters in nucleophilic substitution reaction has been investigated. Reactions with various amine nucleophiles in the presence of TBAI and DIEA can provide the N-substituted α-amino esters up to 99:1 dr. Stereochemical models of transition states, taking into account a hydrogen bonding, are proposed on the basis of the observed results. Also
2-chloro-alkanoic acids 6 and 7 have been obtained the diastereoselective halogenation of chiralsilylketeneacetals 3a-f, and subsequent saponification of the resulting crude esters. Examples characterized by e.e. values up to 95% are reported. The diastereoface selectivity is independent of the silylketeneacetal configuration.