Synthesis And Biological Activity Of 1,3-indandione-5-carboxylic Acid Derivatives

Caspase family representing a class of proteases system in cells, is a series of high homology of cysteine protease having strict requirements for substrate specificity. They play an important role in mediating apoptosis and inflammation. Apoptosis, also programmed cell death, distincting from necrosis, is an active cell death and a process of active aging and death self-regulated by gene. It is a very complex pathophysiological process which is common controlled by a variety of factors, and is essential to body homeostasis. It is the caspase family plays the role of the regulation of apoptosis including caspase-3 which is the final performer playing the key role in apoptosis. For this reason, in many diseases caused by dysfunction or cell abnormal apoptosis which is due to improper regulation (such as AIDS, immune deficiency, reperfusion injury, cancer and nervous system diseases), caspase-3 is often as a drug target in the study.Many caspase-3 inhibitors synthesised are peptide or peptidomimetics inhibitors. Although these caspase-3 inhibitors can inhibit the activity of caspase-3 and apoptosis to some extent, there are many obvious deficiencies in inhibiting apoptosis, they are easy to be hydrolyzed by protease, metabolic instable,poor cell membrane permeable, poor bioavailable and pharmacological, and expensive. Therefore, more and more researchers will focus on non-peptide inhibitors of the caspase-3.Based on the structure of 5-nitro-isatin structurein which is internationally recognized as a non-peptide caspase-3 inhibitor, we refined the structure of isatin. In the process of screening compounds what we known, we found that ninhydrin has a similar structure with isatin. In in-vitro enzyme activity assay, we found that the IC50 value of ninhydrin was 1.2μM. Ninhydrin with high inhibition activity can be used as the skeleton of inhibitors. In order to increase the hydrophilicity of compounds, benzene ring in the ninhydrin was connected to the carboxyl polar groups. Ultimately, we measured IC50 value of ninhydrin-5-carboxylic acid was 1.32μM, and known ninhydrin-5-carboxylic acid had a higher inhibitory activity. In addition, because carboxylic ninhydrin have many advantages, such as the ketone active level, easy to reaction with many compounds to occurr various types of chemical reactions, the molecular weight is not heavy, and have much room for modification. So, we will use ninhydrin-5-carboxylic acid as the preferred framework of the new inhibitors.Because we can not synthesis carboxylic ninhydrin from ninhydrin directly, so we used the commercial 1, 2, 4-benzene anhydride as the starting material, and reaction with acetic anhydride and triethylamine get the ester, and then got 1, 3-indandione-5-carboxylic acid by decarboxylation of TFA. The current internationally method of ninhydrin synthesized by indanedione is using the substitution of 2-position bromides, but we found this method was a failure. Mainly due to two bromide method is suitable for the structure containing electron donor groups, and the skeleton of 1,3-indanedione-5-carboxylic acid containing carboxyl group which is one of electron-withdrawing groups , it is difficult to react. So we tried a variety of methods, and ultimately we synthesised 5-carboxylic ninhydrin through the method of oximation and de-oximation.In order to obtain more effective inhibitors, we modified the structure of carboxyl ninhydrin,designed and synthesized 2-formyl amino-2-hydroxy -1,3-dioxo -2,3 - dihydro-1H-inden -5- acid, and IC50 was 0.16μM; 2 - (carboxy (nitro) methyl) -2-hydroxy -1,3 - dioxo -2,3 - dihydro-1H-inden -5- carboxylic acid, which IC50 was 0.20μM. The above have the same level inhibitory activity comparaed with the non-peptide inhibitors of caspase-3 which internationally recognized.In summary, in this thesis, first of all, we determined structure of ninhydrin-5-carboxylic acid as a new skeleton of non-peptide caspase-3 inhibitor, and then synthesized and modified it to get a series of non-peptide caspase-3 inhibitors. In in-vitro enzyme activity assay, we confirmed that the new compounds with high inhibitory activity and potential prospects of drug application. It provided the inspiration and to find more effective non-peptide inhibitors of caspase-3 for the future.