Design, Synthesis And Activity Evaluation Of Novel Benzoheterocyclic Derivatives As Acrosin Inhibitors

Environmental pollution, population growth and resource depletion are seriousproblems, which threaten human survival and economic development in the newcentury. The large population, weak economic foundation and per capita relativeshortage of resources are the key problems restricting China’s social and economicdevelopment, and so, the research to new contraceptive methods, reasonableregulationthe rate of population growth in our country is that we are faced with adaunting task. Now, there are clinical contraceptive methods including steroidalcontraceptive drugs, contraceptive devices, surgical blocked fallopian tubes or vasdeferens, topical contraceptives. Over several years, hormonal contraceptives whichwomen used to use have some side effects, interfering with women’s normalphysiological function. While only few contraceptive methods like condoms andvasectomy surgery are available for male. Therefore safe, efficient, reversible,low-toxicity male contraceptives not only allow men to assume the responsibility forcontraception, also injects new vitality to control population growth.The epididymis is an important part of the male reproductive system and plays adecisive role in sperm maturation, storage and protection. Acrosome is the corestructure of the sperm and acts as a specialized lysosome, it contains a variety ofenzymes associated with fertilization. Acrosin not only affects sperm motility,promotes sperm motility but also disperses acrosome matrix in the process offertilization and hydrolyzes the zona pellucida, which helps sperm enter and fusion toovum. Therefore acrosin has become the research hotspot target in recent years.Acrosin inhibitors are few and mostly obtained by random screening. Most ofthem have the drawbacks of toxicity, poor specificity and stability and so on. Inaddition, due to the information lack of binding mode of the inhibitor and targetenzyme, the progress of acrosin inhibitor research and development based on thestructure of the target enzyme is relatively slow.The structure of human sperm beta-acrosin has not been reported. In previousstudies, we have built the homologous3D model of human acrosin on the crystalcoordinates of ram and boar acrosin, and analyzed the properties of the activity site ofhuman acrosin by the method of multiple copy simultaneous search （MCSS） method,its reliability through the Ramachandran map and profile₃D Figure verification. It was found that active cavity can be divided into three parts: P1pocket is deep, but asmall opening for the polar region, and the hydrophobic of P1side could target theligand to the active site. P1is also an important area to form hydrogen bonds withenzyme inhibitors, including important residues T216, C217, Q218, S221, W243. P2pocket is light, with a larger opening, in which several important residues formhydrogen-binding interactions and electrostatic interactions.G-cavity is on the right anarrow, hydrophobic interaction in G groove takes the leading position.Based on the pre-human acrosin obtained three-dimensional structure and usedcomputer-aided drug design approach, based on the existing acrosin inhibitorsubstituted isoxazolecarbaldehydes as basic scaffold, we designed the benzimidazolenucleus, benzothiazole nucleus and benzopyran nucleus by scaffold hopping. Andmeanwhile, we extended the three nucleuses in order that the target compound caninteract with the P2cavity or G groove. We designed and synthesized45novelcompounds as human acrosin inhibitors which are reported for the first time,including N-substituted2-（3-substituted urea）-1-H-benzimidazole, N-5-bromophenylthiazol-2-N-substituted-acetamides,2-N-substituted-N-（4-oxo-3-（1H-tetrazole）-4Hbenzopyran-8-acetamide）. All intermediates and target compounds was confirmed by1HNMR and MS. In vitro inhibitory activity studies found that all target compoundshave much good inhibitory enzyme activity and were superior to the positive controldrug TLCK. And the IC50value of benzimidazole derivatives, benzothiazolederivatives and benzopyran derivatives were0.05⁷.32,0.02³2.10and0.09⁵.00μmol/mL, respectively. The study provides a new structure type for malecontroceptives research, and if further structural optimization, is expected to getefficient low toxicity male controceptives.