Arylstibonic acids are potent and isoform-selective inhibitors of Cdc25a and Cdc25b phosphatases

Arylstibonates structurally resemble phosphotyrosine side chains in proteins and here we addressed the ability of such compounds to act as inhibitors of a panel of mammalian tyrosine and dual-specificity phosphatases. Two arylstibonates both possessing a carboxylate side chain were identified as potent inhibitors of the protein tyrosine phosphatase PTP-β. In addition, they inhibited the dual-specificity, cell cycle regulatory phosphatases Cdc25a and Cdc25b with sub-micromolar potency. However, the Cdc25c phosphatase was not affected demonstrating that arylstibonates may be viable leads from which to develop isoform specific Cdc25 inhibitors

The synthesis of novel organofluorines by electrophilic fluorination and their evaluation as inhibitors of protein tyrosine phosphatase 1B

grantor: University of TorontoCompounds bearing non-hydrolyzable phosphate mimetics were prepared and examined as inhibitors of protein tyrosine phosphatase 1B (PTP1B). These studies begin with a brief look at the importance of the phosphate group to PTP1B-peptide interactions. This was accomplished by examining peptides bearing unnatural, non-phosphorylated tyrosine or phenylalanine derivatives as PTP1B inhibitors. These studies indicate that the presence of a phosphate group or phosphate mimetic is crucial to peptide binding. We then examine non-peptidyl aryl derivatives bearing the most commonly used phosphate mimetic, the difluoromethylenephosphonic acid (DFMP) group, as PTP1B inhibitors. This involved developing a new approach, based on electrophilic fluorination of Ã-phosphoryl carbanions, to the synthesis of aryl DFMP's. Factors affecting the electrophilic fluorination yields, such as temperature, base and counterion were examined. Inhibition studies revealed that these compounds were not significantly more potent inhibitors than the parent compound, Ã,Ã-difluorobenzylphosphonic acid, with the exception being the 'meta'-phenyl substituted species which decreased the IC50 by approximately 17-fold relative to (Ã,Ã-difluorobenzylphosphonic acid. However, certain compounds bearing two DFMP moieties were very potent inhibitors. Possible reasons for this are discussed. Further studies involved examining chiral (Ã-monofluorophosphonates as PTP1B inhibitors. This work includes the first description of a general method for preparing this class of compounds. The key step in this procedure was the diastereoselective electrophilic fluorination of Ã-carbanions of asymmetric phosphonamidates bearing (-)-ephedrine as a chiral auxiliary. Removal of the ephedrine auxiliary afforded Ã-monofluorophosphonic acids in modest to good yields. Inhibition studies revealed that the R-enantiomers: were approximately 10-fold more potent inhibitors than the corresponding S-enantiomers, but 10-fold less potent than their Ã,Ã-difluoro analogues. Possible reasons for these differences are discussed. Finally, we turned our attention to novel organofluorine functionalities that may be either more amenable to cellular penetration or more readily converted to caged compounds than DFMP-bearing compounds. Thus, compounds bearing monoanionic moieties, such as the Ã-fluoro-tetrazole, carboxylate, malonyl and Sultanate groups were prepared using electrophilic fluorination and then examined as PTP1B inhibitors. Of these compounds, those bearing the Ã-fluorosulfonate moiety were the most effective PTP1B inhibitors although these were not as potent inhibitors as their DFMP analogues.Ph.D

Rapid detection of single nucleotide polymorphisms associated with spinal muscular atrophy by use of a reusable fibre-optic biosensor

Rapid (<2 min) and quantitative genotyping for single nucleotide polymorphisms (SNPs) associated with spinal muscular atrophy was done using a reusable (approximately 80 cycles of application) fibre-optic biosensor over a clinically relevant range (0–4 gene copies). Sensors were functionalized with oligonucleotide probes immobilized at high density (∼7 pmol/cm(2)) to impart enhanced selectivity for SNP discrimination and used in a total internal reflection fluorescence detection motif to detect 202 bp PCR amplicons from patient samples. Real-time detection may be done over a range of ionic strength conditions (0.1–1.0 M) without stringency rinsing to remove non-selectively bound materials and without loss of selectivity, permitting a means for facile sample preparation. By using the time-derivative of fluorescence intensity as the analytical parameter, linearity of response may be maintained while allowing for significant reductions in analysis time (10–100-fold), permitting for the completion of measurements in under 1 min