致病细菌的耐药性问题已成为公众健康最严重的威胁之一，不但威胁人类健康，还会影响社会经济的发展。2017年2月，世界卫生组织根据对新型抗生素的迫切需求程度将耐药菌分为三个类别，其中程度最为严重的一类包括不动杆菌属、假单胞菌属和各种肠杆菌科（包括克雷伯氏菌属、大肠杆菌、沙雷氏菌属和变形杆菌属），均为多重耐药的革兰阴性菌。然而，目前的抗菌药物主要针对革兰阳性菌，对革兰阴性菌作用较小。

细胞外膜是革兰阴性菌特有的结构，脂多糖（LPS）是组成外膜的主要成分，而类脂A是细胞合成LPS的必经底物。因此，抑制类脂A的生物合成，可阻断LPS的正常装配，最终破坏革兰阴性菌的外膜，导致细菌裂解死亡。UDP-3-O-(R-羟基癸酰基) -N-乙酰葡糖胺脱乙酰酶（LpxC）是类脂A生物合成中的限速酶，且在革兰阴性菌中具有较高的同源性，与哺乳动物（包括人）的各种酶没有共同序列。因此，LpxC成为抗革兰阴性菌药物研发的全新靶标，目前不存在已有的耐药性。已有多种LpxC抑制剂先后被报道，一些化合物具有很好的抗菌活性，其中ACHN-975是目前唯一一个进入临床研究的LpxC抑制剂，除可用于治疗多种革兰阴性菌感染外，对于敏感型和耐药型铜绿假单胞菌的抑制活性MIC (P. aeruginosa ATCC27853 =0.25 μg/mL）也明显优于临床上常用的一、二线抗菌药物。但由于注射部位的局部炎症反应，终止于临床II期研究。

目前，仅Achaogen公司在2013年公布的专利(专利号:WO2013039947A1)中报道了ACHN-975的合成路线，但该路线存在氧化剂用量多、毒性大、条件苛刻、路线长、收率低等问题。为了实现ACHN-975的合成以及以ACHN-975为先导化合物对其结构优化和修饰，以期得到活性相当或更强，毒副作用更低的化合物。本论文的主要研究工作是对ACHN-975的合成工艺路线进行优化，研究工作分为以下三个部分：

一、ACHN-975的合成与活性测试

按原专利路线，通过12步反应合成终产物ACHN-975，并进行抗菌活性测试，活性结果与原专利报道一致。

二、ACHN-975的合成工艺优化

1在醇氧化为醛的反应中，用Dess-Martin氧化剂代替二氧化锰，减少了氧化剂用量，缩短反应时间，提高反应收率且对环境更加友好。②在缩醛的酯化反应中，采用毒性较小的溶剂甲苯代替苯，反应可正常进行且收率提高。③在1,1-二溴-1-烯烃与末端炔烃的偶联反应中，将催化剂和配体更换为三(二亚苄基丙酮)二钯[Pd₂(dba)₃]及三(4-甲氧苯基)膦[(4-MeOPh)₃P]并在80 ℃催化反应，顺利得到目标产物。总之，优化后的工艺氧化剂用量少，反应时间短，避免了一类溶剂苯的使用，总收率也由文献的2.6 ‰提高至6.6 ‰，是原专利的2.5倍。

三、ACHN-975的新合成工艺研究

原专利通过4步反应制得环丙基化合物[(1R,2R)-2-甲酰基环丙基]甲基乙酸酯，新合成工艺利用新型不对称手性助剂丁基硼酸酯，通过不对称Simmons-Smith反应1步反应制得与原专利手性一致的环丙基化合物。新合成工艺缩短三步反应，避免了危险试剂硝酸铵和一类溶剂苯的使用，操作安全，总收率也由文献的2.6 ‰提高至29 ‰，是原专利的11.1倍。

将使用原工艺、优化工艺和新工艺得到的三批终产物进行抗菌活性测试，

对大肠埃希菌ATCC 25922和铜绿假单胞菌ATCC 27853 的抑菌活性相同(MIC分别为0.125 mg•mL^-1 和0.25 mg•mL^-1 )，且与原专利报道一致(MIC分别为0.125mg•mL^-1 和0.2 mg•mL^-1)。

本研究论文探索了ACHN-975的合成工艺优化及关键手性中心的构建新方法，为后续以ACHN-975为先导化合物，设计合成N-芳基-L-苏氨酸异羟肟酸类LpxC抑制剂的研究奠定了实验基础。

The problem of antimicrobial resistance has become one of the most serious threats to public health. The World Health Organization classified resistant bacteria into three categories based on the urgent need for new antibiotics, and the most serious are all multi-drug resistant Gram-negative bacteria, including Acinetobacter, Pseudomonas and various Enterobacteriaceae. However, the current antibacterial drugs are mainly directed against Gram-positive bacteria, and have little effect on Gram-negative bacteria.

The extracellular membrane is the unique structure to Gram-negative bacteria. Lipopolysaccharide (LPS) is the main component of extracellular membrane, and lipid A is the essential substrate for the biosynthesis of LPS. Therefore, inhibits the biosynthesis of lipid A can block the normal synthesis of LPS, eventually destroying the extracellular membrane and leading to bacterial lysis and death. UDP-3-O-(R-hydroxydecanoyl)-N-acetylglucosamine deacetylase (LpxC) is the rate-limiting enzyme in lipid A biosynthesis and has a higher homology in Gram-negative bacteria. LpxC has become a new target for the development of anti-gram-negative bacteria, and there is no existing drug resistance. At present , a variety of LpxC inhibitors have been reported, some compounds have good antibacterial activity, of which ACHN-975 is the only one to enter clinical studies, the inhibitory activity of sensitive and resistant P. aeruginosa MIC (P. aeruginosa ATCC27853 = 0.25 μg/mL) is significantly better. However, the clinical phase II study was terminated due to the inflammatory at the injection site.

At present, only Achaogen's patent published in 2013 reported the synthetic route of ACHN-975, but this route has some obstacle such as high dosage of oxidant, high toxicity, harsh conditions, long route and low yield. In order to synthesize ACHN-975 and derivatives, it is expected to obtain a compound having a relatively active and a lower toxic. The main research work of this thesis is to optimize the synthetic process route of ACHN-975. The research work is divided into the following three parts:

I. Synthesis ACHN-975 and antibacterial activity test

According to the original patent route, the final product ACHN-975 was synthesized through 12 steps of reaction, and the antibacterial activity test was carried out. The activity results were consistent with the original patent report.

II. The synthesis process optimization of ACHN-975

The synthetic route of LpxC inhibitor ACHN-975 was improved as follows: In the oxidation reaction, Dess-Martin is used instead of manganese, which reduces the amount of oxidant, shortens the time, improves the yield,and more friendly to the environment. In the esterification reaction, the less toxic solvent toluene is used instead of benzene, and the yield is also improved. In the Sonogashira coupling reaction ,using tris(dibenzylideneacetone)dipalladium and tris(4-methoxyphenyl)phosphine at 80 °C, the target product was obtained. In short, the optimized process reduces the amount of oxidant, shortens the reaction time, and avoids the use of benzene. The target compound was obtained in an overall yield of 6.6‰, which was 1.5 times higher than that reported in the literature(2.6‰).

III. The new synthetic process of ACHN-975

The new synthesis process uses a novel chiral compound to build a chiral center. It shortens three-step reaction and avoids the use of ammonium nitrate and benzene. The operation is safe and the total yield is also increased from 2.6‰ to 29‰ .

Three batches of final products obtained using the original process, optimized process and new process were tested for antibacterial activity.The activity against Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 was same, and was consistent with the original patent report .

In summary, this research explores the optimization of the synthesis process of ACHN-975 and the construction of chiral centers, and laid the foundation for the subsequent research of N-aryl-L-threonine hydroxamic acid LpxC inhibitor with ACHN-975 as the lead compound