An l-valine diamide chiral selector was attached to a polysiloxane through a long hydrocarbon spacer giving rise to a chiral stationary phase (CSP), Chirasil-Val-C11. The enantioselective properties of this readily accessible diamide CSP under gas chromatographic conditions were found to be similar to that of the commercially available Chirasil-Val CSP prepared by a polymer-analogous route. A new binary CSP, Chirasil-DexVal-C11, was synthesized by means of simultaneous attachment of both the l-valine diamide and permethylated β-cyclodextrin selectors to a polysiloxane using platinum-catalyzed hydrosilylation, thereby overcoming the immiscibility problem known for Chirasil-Val and Chirasil-Dex. This binary CSP retained both the enantioselectivity of Chirasil-Val-C11 toward α-amino acid derivatives and the unsurpassed enantioselectivity of Chirasil-Dex toward underivatized chiral alcohols, ketones, and hydrocarbons. Furthermore, it was shown that the presence of the cyclodextrin selector in Chirasil-Val-C11 significantly improved the enantioseparation of proline, which represented a problematic amino acid on diamide CSPs.
一种 l-缬
氨酸二酰胺手性选择器通过一个长的碳氢化合物间隔物连接到聚
硅氧烷上,从而产生了一种手性固定相(C
SP)--Chirasil-Val-C11。研究发现,在气相色谱条件下,这种容易获得的二酰胺手性固定相的对映体选择性与通过聚合物类似路线制备的市售 Chirasil-Val 手性固定相相似。通过
铂催化的氢
硅烷化作用,将 l-缬
氨酸二酰胺和过甲基化的 β-
环糊精选择剂同时附着在聚
硅氧烷上,合成了一种新的二元 C
SP,即 Chirasil-DexVal-C11,从而克服了 Chirasil-Val 和 Chirasil-Dex 的不溶性问题。这种二元 C
SP 既保留了 Chirasil-Val-C11 对 α-
氨基酸衍
生物的对映选择性,又保留了 Chirasil-Dex 对未充分活化的手性醇、酮和烃的无与伦比的对映选择性。此外,研究还表明,Chirasil-Val-C11 中
环糊精选择器的存在大大提高了脯
氨酸的对映体分离效果,而脯
氨酸是二酰胺 C
SP 上的问题
氨基酸。