Molecular Recognition of Acyclic Stereoisomer Using a Simple High Performance Liquid Chromatography. I

Abstract

Separation of stereoisomer such as diastereomer on silica gels was carried out using high performance liquid chromatography (HPLC) in a normal phase mode to investigate a correlation between the configuration of diastereomers and their elution order. Relatively flexible acyclic alcohols including a variety of functional groups such as amide, nitro, ester, sulfone, or sulfoxide are employed as solutes diastereomers because of their synthetic importance and analytical interest. The diastereomers can be easily resolved on various types of silica gels under a typical normal phase condition but unexpectedly, their elution order tends to be classified into two different types mainlv based on a substituent group. Silica particles containing various metals were also utilized to increase the interaction between adsorbents and solutes through a chelating effect and the metals seem to affect not only elution time but also resolution of diastereomer based on the type of a substituent group. Through experiments to change the conformation of diastereomer through preventing intramolecular hydrogen bonding by a bulky protective group for the hydroxy group, the elution order of diastereomer is found out to be affected mainly by both sterical bulkiness of diastereomers derived from their stabilized conformation and the retention selectivity of the substituent group therein in the employed mobile phase. Finally a certain prediction for the determination of configurational information of acyclic alcohol diastereomers can be made from their chromatographic information. The results may be useful in developing further the theory and/or rules of selectivity in separation of stereoisomer using a simple chromatographic method.