【作者】 邱建超；

【导师】 毕彩丰； 范玉华；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2008， 硕士

【摘要】 本文研究了头孢菌素类抗生素医药中间体AE-活性酯的合成工艺,通过实验确定了最优反应条件,提高了产品质量和收率;通过量子化学计算对AE-活性酯进行密度泛函理论研究,确定其平衡几何构型,分析电荷分布、前沿轨道成分、振动频率等,为头孢菌素类抗生素的定量构效关系等相关理论研究提供有价值的参考。1、本文针对AE-活性酯合成工艺的两种方法——亚磷酸三乙酯合成法和三苯基磷回收法,通过正交设计优化确定了最佳反应条件,结果如下:1)亚磷酸三乙酯合成法:以亚磷酸三乙酯、氨噻肟酸和二苯并噻唑硫醚为原料,用二氯甲烷和乙腈的混合溶剂为反应的溶媒体系,用吡啶和三乙胺为催化剂合成AE活性酯。实验表明:温度和催化剂是影响反应收率和产品质量的的主要因素,还有原料的配比、加料顺序、混合溶剂的体积比、反应时间等也是重要影响因素。通过正交优化确定的最佳反应条件为:反应温度5~10℃,二氯甲烷与乙腈的体积比为1:2,反应时间2 h,氨噻肟酸与二苯并噻唑硫醚的摩尔比为1:1.4。产品收率可达90.8%,纯度≥98.5%(LC)。2)三苯基磷回收法:以三苯基磷、氨噻肟酸和二苯并噻唑硫醚为原料制备AE-活性酯,是经典的传统合成方法,采用文献报道合成条件,收率可达88%。本法由于三苯基磷价格昂贵,故成本较高,但是如果能够将原料回收将大大降低成本。本文主要工作是在制备产品后的残液中加入双三氯甲基碳酸酯(三光气),以三乙胺为引发剂,经两步反应回收三苯基磷和二苯并噻唑硫醚,达到原料回收重复利用的目的。通过实验,确定的最佳回收反应条件为:反应温度30℃,反应时间4 h,三光气加入量8.9 g(与理论用量摩尔比为1.5 : 1),三乙胺用量2 mL(与三光气用量成正比)。二苯并噻唑硫醚收率可达64.2%,三苯基磷收率可达63.1%。纯度均大于98%(LC),可以作为合成AE-活性酯的原料,达到循环利用、降低成本的目的。通过平行实验验证了所确定实验条件的可靠性,并对所合成产品进行了纯度测试液相色谱分析(HPLC)、红外吸收光谱分析(IR)、质谱分析(MS)和核磁共振氢谱分析(1H-NMR)。探讨了反应机理:氨噻肟酸在三乙胺作用下脱去羧酸的氢得羧酸根氧负离子,此氧负离子进攻亚磷酸三乙酯的磷原子空轨道,成氧磷单键,二苯并噻唑硫醚中的硫原子的孤对电子进攻羰基碳正离子成过渡态,氧负离子重新成羰基,由于比较容易形成磷氧双键,使碳氧键断裂,最终脱去磷酸三乙酯得目标产物AE-活性酯。2、借助Gaussian 03计算软件,采用密度泛函理论(DFT)B3LYP方法,选取6-31g、6-31g(d, p)两种不同基组,对所合成头孢菌素中间体AE-活性酯进行了量子化学计算和密度泛函理论研究。通过40步全优化计算确定了化合物的稳定平衡几何构型,并在优化构型基础上进行了频率计算,对比两种不同基组,结合相关实验数据分析了NBO电荷分布和转移、前沿分子轨道成分、自然键轨道、红外光谱等,联系药物合成反应和药效作用机理探讨了分子结构与活性的关系。AE-活性酯由氨噻肟酸(AT)和二苯并噻唑硫醚(DM)经硫酯化反应缩合而成,所得稳定几何构型为AT分子片平面与M(2-苯并噻唑硫醇)分子片平面的垂直交接,交接处是通过AT羧基上的C与M硫醇基上的S缩合成酯基相连。零点能校正分子总能量为-5.619×104 eV,有较好的稳定性。前沿分子轨道分析显示分子的主要活性部位集中在AT分子片,尤其是与噻唑环相连的氨基活性较高,与其他生物分子作用时易发生反应。对照比较产品的实验测试红外光谱谱图与计算模拟红外光谱谱图,特征吸收峰数据一致,相似性较好,说明通过计算模拟研究化合物分子的振动频率分析具有很好的可靠性。在合成头孢类抗生素药物时,活性酯分子酯键断裂脱掉M分子片,与7-ACA中β-内酰胺上的氨基发生作用,羰基C原子作为电子受体接受—NH2提供的电子。理论计算可以很好的解释反应机理。更多还原

【Abstract】 AE-active ester [S-2-Benzothiazolyl 2-amino-alpha-(methoxyimino)-4-thiazolethiol acetate] is an important intermediate of many third and fourth generation cephalosporin antibiotics. In this paper, AE-active ester’s synthesis process has been studied. The optimum reaction conditions are found and the yield is increased by designing rational experimental project. Density functional theory (DFT) is also used and AE-active ester is studied by quantum chemistry calculation. The equilibrium molecular geometry of AE-active ester is determined. In addition, the components and energies of molecular orbital, NBO charge distribution and transfer, vibration frequency and IR spectra of the compound have been analyzed. These works can offer valuable reference to the QSAR (quantitative structure-activity relationship) and other relevant theoretical research of cephalosporin antibiotics.1. There are two synthesis processes of AE-active ester, triethyl phosphate synthesis method and triphenyl phosphine recovery method. Both of them are optimized by orthogonal experiment design in this paper. The optimum reaction conditions result are as follows: 1) Triethyl phosphate synthesis method.In this method, the materials are AT(Ethyl-aminothiazoly Loximate) and DM(bisbenzothiazole sulfide) and the cheap triethyl phosphate is used to instead of the expensive triphenyl phosphine. The mixed solvent of dichloromethane and acetonitrile is used as the reaction’s solvent system. Catalysts are pyridine and triethylamine. The whole reaction is under low temperature environment. Except temperature and catalyst, the main influence factors to reaction yield are the proportion of the materials, the volume ratio of the mixed solvent and reaction time. The optimum reaction conditions optimized by orthogonal experiment design are: the reaction temperature is 5~10℃, the volume ratio of dichloromethane and acetonitrile is 1:2, the reaction time is 2 hours and the proportion of AT and DM is 1:1.4. Then the production yield is 90.8% and the purity≥98.5 % (LC).2) Triphenyl phosphine recovery method.In this method, AT, DM and triphenyl phosphine are used as materials to synthesize AE-active ester. This method is classic and traditional. The product yield can reach to 88%. This paper’s main work is to recover the expensive triphenyl phosphine and DM. For this aim, bis (trichloromethyl) carbonate is added into the residual liquid of AE-active ester’s synthesis reaction above. Triethylamine is used as the initiator. Finally, triphenyl phosphine and DM are recovered by two reactions and the aim of the materials’recovery and reuse is realized. The optimum reaction conditions are: the reaction temperature is 30℃, the reaction time is 4 hours, the addition of bis (trichloromethyl) carbonate is 8.9 g(the molar ratio with the theoretical dose is 1.5:1) and the dosage of triethylamine is 2 mL(be proportional to the dose of bis (trichloromethyl) carbonate). Then the recovery yield of DM is 64.2% and the recovery yield of triphenyl phosphine is 63.1%. Both of their purity is beyond 98 % (LC). The DM and triphenyl phosphine recovered can be used to synthesize AE-active ester.Parallel experiments are taken for verification on the base of the optimum reaction condition. The synthetic product is characterized by HPLC, IR spectroscopy, MS analysis and 1H-NMR analysis. The reaction mechanism has been discussed. The carboxylic H of AT is deleted under the action of triethylamine, and the carboxylic acid oxygenic negative ion is formed which attacks the P atom’s empty orbit in triethyl phosphate to form O&P single bond. The lone pair electronic of S atom in DM attacks the carbonyl carbocation to form transition state, and then the oxygenic negative ion converts to carbonyl again. Because it’s easy to form P & O double bond, the C-O bond breaks, triethyl phosphate is removed finally and the target product AE-active ester is obtained.2. A quantum chemistry calculation study and density functional theory study on AE-active ester are carried out by Gaussian 03 calculation software and DFT B3LYP method. Two different basis sets 6-31g and 6-31g (d, p) are selected. The equilibrium molecular geometry of AE-active ester is determined after 40 steps optimizing calculation. According to the equilibrium molecular geometry, the components and energies of molecular orbital, NBO charge distribution and transfer, vibration frequency and IR spectra of the compound have been analyzed. The relationship of molecular structure and activity is also discussed combined with the pharmaceutical synthesis reaction and medical effect mechanism.AE-active ester is obtained by the thio-esterification condensation reaction of AT and DM. The equilibrium molecular geometry is the vertical connection of AT molecular fragment and M (2-mercapto benzothiazole) molecular fragment. At the connection place, the carboxyl C atom of AT connected with the thiol group S atom of M.The zero-point energy corrections molecular total energy is -5.619×104 eV, and the compound has better stability. The frontier molecular orbital analysis shows that the main active part centralizes at the AT molecular fragment, especially at the amido connected with the thiazole ring and it is easy to react while acting with other bio-molecule.Compare with the experiment test IR spectroscopy and the calculation simulation IR spectroscopy of AE-active ester. The result shows that the data of the characteristic absorption peak is consistent and comparability is better. So that it’s reliable to study the compound molecular vibration frequency analysis by calculation simulation.When to synthesize cephalosporin antibiotics, the ester bond of active ester molecule breaks and the M molecular fragment is removed. And then active with amido connected with theβ– lactam in the 7-ACA molecule. The C atom accepts the electrons offered by -NH2 as electron acceptor. In conclusion the theory calculation can explain the reaction mechanism well.更多还原