Preparation Of Chiral Stationary Phase Based On Amino Acid Ligand

Amino acids are composed of the human proteins most basic structural unit. Themselvesand their derivatives are commonly used in drugs and health products raw materials. Inaddition to glycine, other amino acids have the chiral difference D-and L-type. The body canmetabolize the L-amino acids. But the D-amino acids, there may be some potential hazards.Therefore, it is significant to study amino acid chiral separation.The ligand exchange chiral stationary phase method is particularly suitable for the chiralseparation of amino acids. Chiral stationary phase plays a vital role to separate good and bad.It consists of three parts-the carrier, coupling and chiral selector. Currently, the carrier oftenuses silica gel, coupling agent often uses KH-560, while the chiral selector often usesL-amino acids, tartaric acids, propane diamine, ephedrine and so on. How to improve theselectivity of chiral stationary phase is a relentless pursuit of the goal.We select L-amino acids as chiral selector to study the conditions and rules ofpreparation chiral stationary phase by the order bonding and reverse bonding two ways. In theorder bonding, we study the influence of synthesis conditions to the coupling silica gel; themethoxy on the coupling agent involved in the extent of the bonding reaction; the influence ofamino acids acid-base properties to the synthesis of chiral stationary phase. In the reversebonding, we study L-histidine and coupling agent KH-560reaction mixture liquidchromatography separation conditions; detection analysis of the target product and byproducts;finally, preparation chiral stationary phase by above-mentioned two ways. Compared withnitrogen content confirm the pros and cons of two kinds of bond order. We draw the followingmain conclusions:1) Studies the synthesis conditions to the coupling silica gel have shown that: increasedthe amount of KH-560, ascended the reaction temperature and advanced the reaction time canpromote silica gel and KH-560to react. When the reaction temperature is higher than90℃,the KH-560will decompose. And ascended the reaction time will promote the decompositionof KH-560. In order to avoid the decomposition products of the KH-560breaking down thequality of coupling silica gel, the reaction conditions that suitable for silica gel and KH-560asfollows: silica gel: KH-560=1:2(mass ratio); reaction temperature65℃to80℃; reactiontime60h~84h. Within the framework of the reaction conditions, only one methoxy involvein the reaction on the KH-560molecules.2) Among the three types of amino acids, only alkaline amino acids (L-histidine) canreact with coupling silica gel directly to generate chiral stationary phase. Advanced the pH ofthe solution, not only promote the reaction of L-histidine and coupling silica gel, but alsoactivate the reaction of L-alanine and L-glutamic acid with coupling silica gel. Theconversion rate of L-histidine and L-alanine can reach80%. The conversion rate ofL-glutamic acid can reach75%. The reaction conditions that suitable for amino acids andcoupling silica gel as follows: room temperature; the reaction time is not less than48h;reaction solution pH=10~11.3) Studies the reverse bonding preparation chiral stationary phases have shown that: TheSi-OCH3on the KH-560molecules is hydrolysis to become Si-OH in the water solvent. Two molecules of the hydrolyzate further react to generate the dimer. The reaction of L-histidineand KH-560in aqueous solvent is essentially L-histidine and the hydrolyzate or the dimer.Increased the methanol content can help to inhibit hydrolysis of KH-560. When methanolcontent>15%(volume ratio), the inhibitory effect to hydrolysis of KH-560is not advance.The reverse bonding way preparation chiral stationary compared with the order bonding, theformer is more conducive to improve the content of chiral selector.