Novel Benzofuran and Benzothiophene Biphenyls as Inhibitors of Protein Tyrosine Phosphatase 1B with Antihyperglycemic Properties

Abstract

Insulin resistance in the liver and peripheral tissues, together with a pancreatic cell defect, are the common causes of Type 2 diabetes. It is now appreciated that insulin resistance can result from a defect in the insulin receptor signaling system, at a site post binding of insulin to its receptor. Protein tyrosine phosphatases (PTPases) have been shown to be negative regulators of the insulin receptor. Inhibition of PTPases may be an effective method in the treatment of Type 2 diabetes. We have identified two novel series of benzofuran/benzothiophene biphenyl oxo-acetic acids and sulfonyl-salicylic acids as potent inhibitors of PTP1B with good oral antihyperglycemic activity. To assist in the design of these inhibitors, crystallographic studies have attempted to identify enzyme inhibitor interactions. Resolution of crystal complexes has suggested that the inhibitors bind to the enzyme active site and are held in place through hydrogen bonding and van der Waals interactions formed within two hydrophobic pockets. In the oxo-acetic acid series, hydrophobic substitutents at position-2 of the benzofuran/benzothiophene biphenyl framework interacted with Phe182 of the catalytic site and were very critical to the intrinsic activity of the molecule. The hydrophobic region of the catalytic-site pocket was exploited and taken advantage by hydrophobic substituents at either the alpha-carbon or the ortho aromatic positions of the oxo-acetic acid moiety. Similar ortho aromatic substitutions on the salicylic acid-type inhibitors had no effect, primarily due to the different orientation of these inhibitors in the catalytic site. The most active inhibitors of both series inhibited recombinant human PTP1B with phosphotyrosyl dodecapeptide TRDI(P)YETD(P)Y(P)YRK as the source of the substrate with IC(50) values in the range of 20-50 nM. Compound 68 was one of the most active compounds in vivo, normalizing plasma glucose levels at the 25 mg/kg dose (po) and the 1 mg/kg dose (ip). Compound 68 was also selective against several other PTPases.

Cross-coupling of Aryl Sulfides Powered by <i><b>N</b></i>-Heterocyclic Carbene Ligands

“…22 Phenol underwent the extended Pummerer annulation with ketene dithioacetal monoxide 27 on treatment with tri uoroacetic anhydride to afford 2 methylsulfanylbenzofuran 28 in 61% yield. The following cross coupling alkylations resulted in short syntheses of 29a and 29b.…”

Docking Studies on Formylchromone Derivatives as Protein Tyrosine Phosphatase 1B (PTP1B) Inhibitors

“…Surprisingly, they all showed "right" preference, suggesting that van der Waals interaction between the hydrophobic group and the active-site residues is a major driving force for such directionality. In the X-ray structures by Malamas et al;26 however, no specific residues were mentioned except saying that the lipophilic 2-benzyl-benzothiophene tail-piece of ligand S formed nonspecific van der Waals contact with the protein. Characteristic score, rank and bond distance between aldehyde carbon and surfur atom of Cys215, d(C-S) of the best pose from each run are listed in Table 5.…”

“…25 Recently surprising X-ray structures of PTP1B with a benzothiophene biphenyl (R) and a sulfono biphenyl (S) (see Figure 2) were reported by Malamas and coworkers. 26 In their study, the orientations of large hydrophobic groups show opposite directionality in the active site of PTP1B. In the case of R, the large hydrophobic group points toward Lys120, Lys116 and Phe182 forming van der Waals interaction and we define such orientation as "left".…”

Docking Simulations and in Vitro Assay Unveil Potent Inhibitory Action of Papaverine against Protein Tyrosine Phosphatase 1B

“…The assay as described previously 31) and adapted for the plate reader, was used for the nanomolar detection of liberated phosphate by recombinant h-PTP 1B. 13,27,32,33) The assay used the phosphopeptide Asp-AlaAsp-Glu-phosphoTyr-Leu-Ile-Pro-Gln-Gln-Gly as substrate. This phosphorylated peptide corresponds to the 988-998 catalytic domain of epidermal growth factor receptor, and it is one of the most efficient peptide substrates known for h-PTP 1B.…”

“…88-682. 32,33,35) The color was allowed to develop at room temperature for 30 min, and the sample absorbance was determined at 630 nm using a plate reader (Bio-Tek instruments ELx 800, U.S.A.). Samples and blanks were prepared in duplicates.…”