Design, Synthesis And Biological Evaluation Of2,5-diaryl-1,3,4-oxadiazole Derivatives As Fbpase Inhibitors

Fructose-1,6-bisphosphatase (FBPase), an important gluconeogenic enzyme, catalyzes the hydrolysis of fructose1,6-bisphosphate to fructose6-phosphate. By inhibition of FBPase, GNG was controlled resulting in the decrease of the glucose output in hepatocyte and the concentration of blood glucose. In the dissertation, a series of2,5-diaryl-1,3,4-oxadiazole derivatives were synthesized and evaluated based on the lead compound2-1(IC50=15.45μM), which was identified as a potential FBPase inhibitor by high-throughput screening (HTS). We hope that one or more compounds would be explored as FBPase inhibitors for further drug development.At first, in order to search for optimized substituents on phenyl A and side chain (G) used for the further modification of the scaffold, a class of compounds were synthesized. As a result, compounds2-5and2-13with4-Me on phenyl A were obtained with a3-fold and2-fold FBPase more activity than2-1respectively.On be basis of compounds2-5and2-13, more modifications of the scaffold were carried out and the SAR (structure-activity relationship) was concluded as follows:(1) Introduction of a group (vinyl, alkyl or carbonyl) into the conjugated phenyl A,1,3,4-oxadiazole B and phenyl C led to the loss of the activity;(2) Modification of amide F (including transposition, N-methylation, replacement with other isosteres) led to the loss of the activity;(3) A fused heterocycle on phenyl B caused the decrease or loss of the activity. Those SAR results clarified the irreplaceable scaffold key for the FBPase inhibitory activity.The substitution effect on phenyl A and C was studied systematically by keeping ring A, B, C and amide F. The results showed that modifications on phenyl C led to the decrease or loss of the activity. A hydrophobic group with moderate electron-withdrawing property (CI, Br,-COOMe) at C-3or a hydrophobic group with electron-donating property (-NMe2,-OMe) was benefit to the activity. The compound6-17(4-NMe2, IC50=1.35μM) showed a10-fold more activity than2-1.An effort to simplify the side chain G to be an alkyl chain with a hydrogen bond receptor (carbonyl, hydroxyl, tertiary amine, carboxyl, phosphate and amide) was made and most of the resulted compounds showed good FBPase inhibitory activity. Among them, compound9-4(IC50=1.19μM) had a12-fold more activity than2-1.Hepatocyte glucose output experiments were carried out for10compounds with good FBPase inhibitory activity. As a result,9-22showed a remarkable inhibition (EC50=167.9μM) against glucose output. The good membrane permeability of9-22would be used for further FBPase inhibitor development.Enzyme kinetics experiments disclosed that2.5-diaryl-1,3,4-oxadiazole derivatives were reversible mixed-type inhibitors against FBPase. A preferable binding mode of substrate and FBPase was calculated by Discovery Studio and verified by the SAR results.In this work,1342,5-diaryl-1,3,4-oxadiazole derivatives were designed, synthesized and characterized and their FBPase inhibitory activities were evaluated. Despite the moderate activities, some of the compounds with good membrane permeability showed a remarkable inhibition against hepatocyte glucose output, which would be used as a lead compound for the further development of FBPase inhibitors.