Hyun Myung Ho, Hun Kim Do
Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Pusan, Republic of Korea.
Chirality. 2004 May 15;16(5):294-301. doi: 10.1002/chir.20038.
A new chiral stationary phase (CSP) containing 11 methylene-unit spacer was prepared by bonding (+)-(18-crown-6)-2,3,11,12-carboxylic acid to aminoundecylsilica gel. The new CSP was superior to the one containing three methylene-unit spacer in the resolution of alpha-amino acids, beta-amino acids, amines, and amino alcohols in terms of both the separation (alpha) and the resolution factors (R(S)). In the resolution of alpha-amino acids on the new CSP containing a long spacer, the retention factors (k(1)) were quite small compared to those on the CSP containing a short spacer. However, in the resolution of relatively more lipophilic beta-amino acids, amines, and amino alcohols, the retention factors (k(1)) were generally greater on the CSP containing a long spacer than on the CSP containing a short spacer. All of these resolution behaviors have been rationalized by the effective competition of the ammonium ions (R-NH(3)(+)) generated by the residual undecylamino groups of the new CSP under acidic condition with the ammonium ions (R-NH(3)(+)) of analytes for the complexation inside the cavity of the crown ether ring of the CSP and the effective lipophilic interaction between the CSP and the relatively more lipophilic analytes.
通过将(+)-(18-冠-6)-2,3,11,12-羧酸键合到氨基十一烷基硅胶上，制备了一种含有11个亚甲基单元间隔基的新型手性固定相（CSP）。在α-氨基酸、β-氨基酸、胺和氨基醇的分离度方面，这种新型CSP在分离因子（α）和分离度（R(S)）上均优于含有3个亚甲基单元间隔基的CSP。在含有长间隔基的新型CSP上分离α-氨基酸时，保留因子（k(1)）与含有短间隔基的CSP相比相当小。然而，在分离相对亲脂性更强的β-氨基酸、胺和氨基醇时，含有长间隔基的CSP上的保留因子（k(1)）通常比含有短间隔基的CSP上的更大。所有这些分离行为都可以通过新型CSP在酸性条件下残留的十一烷基氨基产生的铵离子（R-NH(3)(+)）与分析物的铵离子（R-NH(3)(+)）在CSP冠醚环腔内络合的有效竞争以及CSP与相对亲脂性更强的分析物之间的有效亲脂相互作用来解释。
