Pyrazole Derivatives: Diversity-oriented Synthesis And Bioactivity Evaluation

Chemical genetics has emerged in the past ten years as a research method that uses small molecules to change the way proteins work directly in real time rather than indirectly by manipulating their genes. The term chemical genetics indicates that the approach uses chemistry to generate small molecules and that it is based on principles that are similar to classical genetic screens. It is used to identify which proteins regulate different biological processes, to understand in molecular detail how proteins perform their biological functions, and to identify small molecules that may be of medical value. There are two kinds of genetic approaches, forward and reverse, depending on the starting point of the investigation. In a forward chemical genetic screen, scientists start with an outward physical characteristic of interest and end with the identification of the target proteins that are responsible for it.The success of "chemical genetics" approach is dependent on rapid access to structurally diverse and complex small molecules. Structural complexity is important because many of the small molecules known to disrupt protein-protein interactions are structurally complex natural products. Increasing the size and number of rigidifying elements (macrocycles, polycycles, olefins, etc.) in small molecules is essential for these compounds to bind to sites of protein-protein interactions. The generation of structurally diverse compounds is equally important, as the eventual target of a compound in phenotypic screens can be any one of the cell's or organism's entire collection of proteins. In contrast to target-oriented synthesis, which aims to prepare a specific target compound, the goal of diversity-oriented synthesis is the facile preparation of collections of structurally complex and diverse compounds from simple starting materials.Pyrazoles form an important class of heterocyclic compounds, which occupy a special role in the research of chemistry and pharmacology. They have been found to exhibit a variety of biological activities, usually associated with low toxicity and have raised considerable interest because of their potential beneficial effects on human health. They have attracted intense interest for decades because of their diverse pharmacological properties like anticancer, antimicrobial, antiviral, antidepressant, antioxidant, analgetic, anti-inflammatory, anti-angiogenic and antiglaucoma.Based on the backgrounds mentioned above, the guide line of this study was as follows: According to the forward chemical genetics and diversity-oriented synthesis, we had established a library of pyrazole based small molecules. The diversity-oriented synthesis and biological activities of the pyrazole based library were studied.RESULTS:1. A series of novel 1H-pyrazole-5-carbohydrazide hydrazone derivatives I were synthesized and the effects of all the compounds on lung cancer A549 cell growth were investigated. The results showed that all compounds had inhibitory effects on the growth of lung cancer A549 cells and compound 3e possessed the highest growth inhibitory effect and induced apoptosis of A549 lung cancer cells.2. Novel oxime-containing pyrazole derivatives II were synthesized and determined by IR,1H NMR, HRMS, and X-ray analysis. Isomeric intermediates,6a and 6a', were unambiguously confirmed by X-ray crystal structure analysis and successfully differentiated with 1H NMR chemical shifts of methylene bonded to pyrazole ring. A dose- and time-dependent inhibition of proliferation was observed in lung cancer A549 cell after compound treatment. Inhibition of growth was mainly attributed to the autophagy induction.3.2-(5-(Hydroxymethyl)-3-phenyl-1H-pyrazol-1-yl)-1-phenylethanol derivatives III were synthesized from the reduction reaction of ethyl 1-(2-oxo-2-phenylethyl)-3-phenyl-1H-pyrazole-5-carboxylate and the structures were characterized by means of IR,1H NMR,13C NMR, HRMS and X-ray crystal diffraction. Preliminary biological evaluation showed that compounds 7d and 7e could suppress lung cancer A549 cell growth through cell cycle arrest and autophagy.4. Pyrazolo[1,5-a]pyrazin-4(5H)-ones IV and oxazolo[3,2-d]pyrazolo[1,5-a]pyrazin-5(3H)-ones V were synthesized under the condition of microwave-assisted one-step and solvent-free in a good yield. The structures of the compounds were determined by IR,1H NMR and mass spectroscopy. In addition, a representative single-crystal structure was characterized by using X-ray diffraction analysis. Preliminary biological evaluation showed that the compounds could inhibit the growth of A549 and H322 cells in dosage-dependent manners.5. A ring enlargement reaction of VI is described, which generates the 2,7-diphenyl-5,8-dihydro-4H-pyrazolo[5,1-d][1,2,5]triazepin-4-ones VII in good yields. Currently, investigations are underway to elucidate the bioactivity of these pyrazole-fused heterocycles and the results will be reported in due course.6. A series of fluorescent compounds VIII, containing pyrazolo[1,5-a]pyrazin-4(5H)-one moiety, were designed and synthesized. Structural features have been confirmed by IR, H NMR, HRMS and X-ray crystal diffraction, and the optical properties were investigated by UV-vis absorption and fluorescence spectroscopy. The effect of pH on the UV-vis absorption of compound 13a in methanol-H2O solutions was investigated and interpreted by calculative point of view. pKa value of compound 13a was also determined by a spectrophotometric method from the absorption spectra.In summary, we have diversity-oriented synthesized several pyrazole-fused heterocycle system and evaluated the compounds library. Our study paves the way for studying the mechanism of cell death induced by small organic compounds and builds up basis for finding out potent new anticancer agents.