Solvent Effects in the Enantioselective Catalytic-Phase-Transfer Alkylation of Polymer-Supported Glycine–Iminetert-Butyl Ester: Asymmetric Solid-Phase Synthesis of (R)-α-Amino Acid Derivatives
作者:Mi-Jeong Kim、Sang-sup Jew、Hyeung-geun Park、Byeong-Seon Jeong
DOI:10.1002/ejoc.200700001
日期:2007.5
prepared from Merrifield- or Wang-resin and used in the enantioselective synthesis of (R)-α-amino acid derivatives by using (S,S)-3,4,5-trifluorophenyl-NAS bromide (5) as the chiral phase-transfer catalyst. The chemical yields and enantioselectivities were found to be dramatically dependent upon the ratio of water to organic solvent. The optimal solvent was a mixture of toluene/chloroform/water (9:1:0
聚合物负载的甘氨酸-亚胺叔丁酯 (3, 8) 由 Merrifield-或 Wang-树脂制备,并用于通过使用 (S,S)-3 对映选择性合成 (R)-α-氨基酸衍生物, 4,5-三氟苯基-NAS溴化物(5)作为手性相转移催化剂。发现化学产率和对映选择性显着取决于水与有机溶剂的比例。最佳溶剂为甲苯/氯仿/水(9:1:0.5)的混合物。在 0 °C 下,在最佳溶剂体系中使用 50% CsOH 水溶液对聚合物负载的甘氨酸-亚胺底物 3 与各种烷基卤化物进行催化对映选择性固相相转移烷基化,然后水解和苯甲酰化得到相应的 (R )-N-苯甲酰基-α-氨基酸叔丁酯 11,产率 60-80%,对映体比 (er) 为 96.5: