摘要
手性是人类赖以生存的自然界的本质属性之一,也是一切生命的基础。在自然界,特别是在生物体中,手性化合物的两个对映体的存在量是不同的,有的仅以单一对映异构体存在。药物在生物体内的药理作用具有严格的主客体分子匹配和手性识别的特征。互为对映异构的药物会显示出不同的药理作用,在许多情况下,对映异构体在生物体内的药理活性、代谢过程、代谢速率及毒性等均存在显著的差异。
手性技术包括手性合成和手性拆分两个方面,均为手性化合物尤其是手性药物及其中间体原料制造中必不可少的方法和手段。将外消旋体通过一定的装置分离为光学纯对映体的过程即为手性拆分,是研制手性药物最便捷和低成本的方法。应用手性固定相色谱技术于手性化合物的拆分已日益受到人们的重视。探索新型手性吸附材料、研究吸附相结构与分离性能之间的关系以期获得具有良好普适性的手性固定相以及反相流动相条件下的拆分技术是当前该领域研究热点之一。
本文将手性噁唑啉基团引入丙烯酰胺母体,合成了新型的手性丙烯酰胺衍生物:N-邻(4-苯基噁唑啉)苯基丙烯酰胺(PhOPAM)和N-邻(4-甲基噁唑啉)苯基丙烯酰胺(MeOPAM),以相应的光学活性聚合物为吸附材料制备手性固定相,研究在水相条件下的高效液相色谱(HPLC)拆分性能。主要研究内容包括:
1、利用巯丙基三甲氧基硅烷偶联剂的自由基链转移作用合成了末端带有甲氧基的两种新型光学活性预聚物—poly(PhOPAM)和poly(MeOPAM);通过改变聚合条件(如:单体浓度、稀土金属三氟甲磺酸盐和偶联剂含量)来调控预聚物的结构;应用“grafting to”法制备了相应的高效液相色谱手性固定相(CSP);利用元素分析、热失重分析和傅立叶红外光谱等手段对上述CSP进行结构表征。
2、将上述聚合物基手性固定相分别装填成色谱柱,以D,L-苯丙氨酸(phenylalanine)、D,L-天冬氨酸(aspartic acid)、D,L-缬氨酸(valine)、D,L-丝氨酸(serine)、D,L-丙氨酸(alanine)、D,L-脯氨酸(proline)、D,L-赖氨酸(lysine)、R,S-苹果酸(malic acid)、R,S-扁桃酸(mandelic acid)等9种外消旋化合物作为拆分对象,考察在反相色谱条件下聚合物结构、接枝率等因素对手性拆分能力的影响。结果表明:七种CSP对DL-丙氨酸、DL-丝氨酸、DL-天冬氨酸、DL-缬氨酸都表现出一定的拆分效果,其中,poly(PhOPAM)柱的拆分性能较好。拆分效果与聚合物链节结构、光学活性和接枝率有关。对于poly(MeOPAM)手性柱,对映体拆分的最佳色谱条件为:流速0.5～1ml/min,水相。
3、在流动相里加入铜离子,利用手性配体交换色谱(chital ligand exchangechromatography,CLEC)法,考察poly(PhOPAM)手性固定相和poly(MeOPAM)手性固定相的拆分性能。具体考察了中心离子浓度、流动相pH值等因素对分离效果的影响,并通过光学纯异构体验证分离顺序。最佳色谱条件为:pH=7.0,中心离子浓度[Cu~(2+)1=0.1mmol/L,流速0.5～1.0ml/min。
Chirality is one of intrinsic properties of the nature.For a natural chiral compound, the enantiomers are usually different in quantity,in some cases a single isomer exists exclusively.Drug action is the result of pharmacological and pharmacokinetic processes,by which it enters,interacts and leaves the body.There is a broad range of examples where the stereoisomers of drugs show differences in terms of their bioavailability,distribution,metabolic and excretion behavior and where stereochemical parameters have a fundamental significance in their action and disposition in biological systems.This exquisite stereoselectivity which can occur in many of the metabolic routes of a given drug or xenobiotic has to be carefully consid ered when its development is envisaged or its safety is evaluated.
Chiral technologies include both asymmetric synthesis and optical resolution of racemates,which is very important to the development of chiral drugs.Optical resolution,especially,the high-performance liquid chromatography(HPLC) enantioseparation based on chiral stationary phase(CSP)is most easy and low-cost process for developing of chiral drugs.Therefore,in recent decades more and more attention has been paid to the investigation on new chiral materials for CSPs,the structure-property relationship and the chiral resolution technology with high efficiency.
In this present work,a new type of N-phenylacrylamide derivatives has been developed,in which a chiral oxazoline moiety substitutes at ortho-position of phenyl group(denoted as OPAMs).The corresponding pre-polymers were obtained by the radical polymerizations of OPAMs in the presence of(3-mercaptopropyl)trimethoxysilane (MPS).The poly(OPAM)-based CSPs have been prepared by the coupling reaction between the pre-polymers and macropore silica gel,and their resolution performance has been examined under the inverse HPLC conditions.This study covers mainly the following parts:
1.The synthesis of optically active pre-polymers and corresponding CSPs.By changing polymerization conditions,such as the monomer concentration,MPS concentration,and the content of Y(OTf)_3 in reaction media,a series of pre-polymers with different molecule weights and specific rotations have been synthesized.The corresponding polymer-bonded CSPs were prepared by "grafting to" method,and their structures were characterized by elemental analysis(EA),thermogravimetry analysis(TGA),and FT-IR.
2.The evaluation of chiral resolution ability.The chiral resolution ability was examined under the reverse phase chromatography conditions towards nine racemates including phenylalanine,aspartic acid,valine,serine,alanine,proline,lysine,malic acid,and mandelic acid.The results showed that racemic aspartic acid,valine,serine and alanine could be separated by these CSPs,and poly(PhOPAM)-based column exhibits a moderate resolution performance.The relationship between the structure of CSPs and optical resolution has been elucidated in some extent.The effects of flow rate,organic addition content were also studied.The optimum operation parameters for the effective separation of enantiomer covered the followings:flow rate=1ml/min, H_2O eluent.
3.The chiral separation performance of poly(OPAM)-bonded CSPs under a chiral ligand exchange chromatography(CLEC)mode.The effects of pH of the mobile phase and the concentration of the center ion Cu~(2+)were studied.The optimum operation parameters for the effective separation of enantiomer covered the followings:flow rate=1ml/min,pH=7.0,Cu(Oac)_2-H_2O eluent with[Cu~(2+)]of 0.1mmol/L.In addition,the elution order of enantiomers has been determined by comparison of the chromatogram of optically pure isomers.
引文
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