Design, Synthesis And Biological Activities Of Novel Protein Tyrosine Phosphatase 1B Inhibitors

Protein tyrosine phosphatase 1B (PTP1B) has received much attention due to its pivotal role in type II diabetes and obesity as a negative regulator of the insulin and leptin-signaling pathway. Studies from two laboratories have shown that PTP1B knockout mice exhibit phenotypes of increased insulin sensitivity, improved glucose tolerance, and resistance to diet-induced obesity. In a more therapeutically relevant study, Zinker et al. have demonstrated that a PTP1B antisense oligonucleotide normalized blood glucose and improved insulin sensitivity in diabetic mice via a mechanism of lowering PTP1B protein expression. Thus, small molecule PTP1B inhibitors have considerable therapeutic potential for the treatment of TypeⅡdiabetes and obesity.Recent studies have provided important insights into the basic structural requirements for PTP IB-substrate and -inhibitor interactions and have suggested that identification of highly selective, catalytic site-directed PTP IB inhibitors is possible. Disappointingly, nearly all medicinal chemistry efforts to date have been severely hindered because of the lack of suitable druglike lead compounds for optimization to drug candidates. As is well documented in the literature, the majority of competitive inhibitors of PTP1B incorporate highly charged anions that mimic the pTyr substrateⅠ, such as difluoromethylphosphonates (DFMP), carboxymethylsalicyclic acids (CMS), and oxalylaminobenzoic acids (OBA). Compounds containing negatively-charged non-hydrolyzable pTyr mimetics have exhibited excellent potency (at nanomolar concentrations) in vitro, however, the low cell permeability and low bioavailability of these compounds have limited their application for the development of effective drugs. Therefore, we sought a new pTyr mimetic that would not only be a potent inhibitor of PTP1B, but one which would also avoid or minimize the polarity.In this dissertation, potent and specific PTP1B inhibitors were designed, synthesized and screened, and some results were obtained as follows:(1) Based on the structure of the pTyr substrate, we assumed that desired druglike lead compounds could be obtained if the monoacid based fragment was reserved and the phosphate group of pTyr was effectively replaced by hydrophobic groups, in which the carboxylic group mimics the interactions of the phosphate group of pTyr with residues in the PTP1B catalytic site and hydrophobic groups improve the stability of the enzyme/inhibitor complex through hydrophobic interactions with the active site and surrounding subpockets. As a starting point toward this goal, three series of 2-naphthol tyrosine analogues have been designed and synthesized using structure-based design programs. The bioassay showed that these compounds had good inhibition activity against PTP1B, and were identified as reversible and competitive PTP1B inhibitors. These compounds also displayed better selectivity for other PTPase,77a、79h and 81o possess the best selectivity of 3-,6-and 7-fold for PTP1B over TCPTP, respectively. The docking results showed that the -COOH group could well bind into the active site, and the lipophilic 2-fluorobenzyl group of 77a lies on top of a largely hydrophobic region of the protein, consisted of Ile219, Met258. These results are consistent to our original assumption and the bioassay results.(2) As is well documented in the literature, a number of naturally occurring chalcones have been reported to possess better inhibition activity against PTP1B and the position and the number of the hydroxyl group attached to the chalcone rings are of major importance in the improvement of potential inhibitory effects against PTP1B. Therefore, a series of hydroxyflavonoids were designed and synthesized considering the effect of different skeletons (2,4,6-trihydroxychalcones,2,4-dihydroxychalcones, and 5,7-dihydroxyflavanone). The bioassay showed that these compounds had good inhibition activity against PTP1B, and were identified as reversible and competitive PTP1B inhibitors. These compounds also displayed better selectivity for other PTPase,85d possesses the best selectivity of 9-fold for PTP1B over TCPTP. Further evaluation in cell models illustrated that 87m enhanced insulin receptor phosphorylation in CHO/hIR cells.(3) Considering the advantages of inhibition activity against PTP1B of chalcones, 4-(((5Z)-5-(4-((E)-3-phenyl-3-oxoprop-1-enyl)benzylidene)-2,4-dioxothiazoli din-3-yl)methyl)benzoic acid derivatives and (2E)-methyl 2-((5Z)-5-(4-((E)-3-(3-chlorophenyl)-3-oxoprop-1-enyl)benzylidene)-4-oxothiazolidin-2-ylidene-amino)thiazole-5-carboxylate derivatives were designed and synthesized using structure-based design programs. The bioassay showed that these compounds had good inhibition activity against PTP1B with IC50 values in a range of 0.56-16.3μM, and further bioassays are in progress.(4) Considering the advantages of inhibition activity against PTP1B of chalcones, (4Z)-4-(4-((E)-3-phenyl-3-oxoprop-1-enyl)benzylidene)-2-aryloxazol-5(4H)-one derivatives and N-(4-phenyl-thiazol-2-yl)-4-((E)-3-phenyl-3-oxoprop-l-en-1-yl)benzaldehyde hydrazone derivatives were designed and synthesized using heterocyclic pTyr mimetics. The bioassay showed that these compounds had good inhibition activity against PTP1B with IC50 values in a range of 1.16-15.31μM, and further bioassays are in progress.In this paper,190 compounds were designed and synthesized, and the structures of all synthesized compounds were characterized by 1H-NMR and MS. Part of the compounds were characterized by 13C-NMR. The structure-activity relationships were also discussed. And the results will provide experimental and theoretical clues for designing of novel potent and specific PTP1B inhibitors.