对映体和手性位移试剂的作用及其纯度测定的~1H-NMR研究——BETR法

THE STUDY OF THE INTERACTION BETWEEN THE ENANTIOMER AND CHIRAL SHIFT REAGENT IN THE DETERMINATION OF ENANTIOMERIC PURITY——BETR Method

BETR法是通过CPMG脉冲系列消除手性位移试剂的宽峰,用~1H-NMR测定对映体含量的一个新而简单的方法。用此法测定了2′-羟基-2-苄氧基-1,1′联萘对映体含量,并发现随着手性位移试剂Eu(hfc)_3/联萘的克分子浓度比的增加,R异构体的亚甲基的二个质子共振峰向低场移动得比S异构体快,但S异构体的亚甲基的二个质子共振峰向低场移动的化学位移差值比R异构体增加快,并提出了由于Bloch-Siegert效应,它们的值都和磁场强度有关。

A novel and simple 1H-NMR method for determination of enantiomeric purity, BETR, is studied. BETR ( Broad Peak Elimination by T2 Relaxation) method is one that eliminates the broad peak of chiral shift reagent by CPMG pulse sequence in the 1H-NMR determination. In the application of this technique to the determination of enantiomeric purity of 2-hydroxy-2-benzyIoxy-1.1binaphthyl (1), in the presence of Eu I hic)3, the results are as follows. Increasing the molar ratio of Eu(hic,L,the resonance peaks of methene in R iscmer shift to the lower rede faster than that in S isomers but the chemical shift difference between wo protons of methene in S isomer is greater than that in R isomer. Due to Bloch-Sicgcrt effect, their value: are dependent on the magnetic field strengrh.