Analysis of Construction of Hapalosin Analogue Library by High Performance Liquid Chromatography

Abstract: Recently, there is a rapid increase in making natural product libraries by using combinatorial chemistry technologies. The construction, analytical characterization and screening strategies of combinatorial library were the main parts of combinatorial chemistry technologies.Hapalosin, a novel cyclic depsipeptide firstly separated from the blue-green alga in 1994, which shows mediated multidrug resistance(MDR)-reversing activity has potential use in the treatment of cancer patients undergoing chemotherapy. The group of Professor Peiqiang Huang put forward to construct hapalosin analogue library after total synthesis of hapalosin has been accomplished. The equality of each of components and efficiency of purified of organic libraries is most important for liquid-phase combinatorial synthesis. So the thesis is aimed at studying the applications of high performance liquid chromatography (HPLC) for analysis of the construction of hapalosin analogue library. The influence of polar modifier and column temperature on enantioseparation of benzoin on Chiralcel OD-RH systematically was also studied in the thesis.There are three parts in the dissertation:The first part simply introduced the background of the construction of hapalosin analogue library. Some correlative concepts of combinatorial chemistry were introduced briefly. Purification and analytical characterization methodologies of combinatorial libraries in solution-phase combinatorial synthesis was emphasized. At last, the content of the study was briefly shown.The second part expatiated on the applications of HPLC for analysis of the construction of hapalosin analogue library in detail. The construction of hapalosin analogue library involved two parallel syntheses and two combinatorial syntheses. Because the components of the compound libraries were homologous substances, HPLC could determine the equality and purity of organic libraries preferably. Each component of compound libraries which include double series of homologous substances could be identified using UV spectrum, the rule of carbon number and MS. It was found that most compound libraries were analysed well using HPLC method. 3-member hapalosin analogue library L3 and 9-member hapalosin analogue library L9 were both separated well and characterized successfully: contents of each compontent were equal approximately and the purity of compound library were 65% and 45% respectively. Although base line resolution of 27-member hapalosin analogue library L27 wasn’t achieved, the best resolution maybe considered when using CH3OH/H2O (75:25, v/v) as mobile phase. Based on the chromatogram and MS spectrum of L27, the construction of L27 was achieved successfully.The third part studied the influence of polar modifier and column temperature on enantioseparation of benzoin on Chiralcel OD-RH primarily.It was found that (R)-benzoin enantiomer eluted first than (S)-benzoin when using methanol as mobile phase while the order of elution was reversed when using ethanol and acetonitrile as mobile phase on Chiralcel OD-RH. Thermodynamic data showed that when using methanol as eluent the enantioselectivity was enthalpy dominated while entropically driven separation was observed when using ethanol as eluent. Additionally, enthalpy and entropy both contributed to enantioseparation when mobile phase was acetonitrile. The enantioseparation of benzoin were enthalpy dominated and (S)-benzoin enantiomer eluted first than (R)-benzoin when using n-hexane mixed with different amounts of ethanol as mobile phase on Chiralcel OD-H…
Key words: liquid-phase combinatorial synthesis; Hapalosin analogue library; HPLC; rule of carbon number; Chiralcel OD-RH; temperature effect

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