4'-O-[2-(2-FLUOROMALONYL)]-L-TYROSINE - A PHOSPHOTYROSYL MIMIC FOR THE PREPARATION OF SIGNAL-TRANSDUCTION INHIBITORY PEPTIDES

Development of phosphotyrosyl (pTyr) mimetics which are stable to prot ein-tyrosine phosphatases (PTPs), yet can retain biological potency wh en incorporated into peptides, is an active area of drug development. Since a majority of pTyr mimetics derive their ''phosphofunctionality' ' from phosphorus-containing moieties, such as phosphonates, evolution of new inhibitors and modes of prodrug derivatization have been restr icted to chemistries appropriate for phosphorus-containing moieties. A new, nonphosphorus-containing pTyr mimetic has recently been reported , L-O-(2-malonyl)tyrosine (OMT, 5), which can be incorporated into pep tides that exhibit good PTP and Src homology 2 (SH2) domain inhibitory potency. For phosphonate-based pTyr mimetics such as phosphonomethyl phenylalanine (Pmp, 2), introduction of fluorines a to the phosphorus has provided higher affinity pTyr mimetics. This strategy has now been applied to OR IT, and herein is reported 4'-O-[2-(2-fluoromalonyl)]-L -tyrosine (FOMT) 6), a new fluorine-containing nonphosphorus pTyr mime tic. Incorporation of FOMT into appropriate peptides results in good i nhibition of both PTP and SH2 domains. In an assay measuring the inhib ition of PTP 1B-mediated dephosphorylation of phosphorylated insulin r eceptor, the peptide Ac-DA-D-E-X-L-amide exhibited a 10-fold enhanceme nt in inhibitory potency for X = FOMT (19) (IC50 = 1 mu M) relative to the unfluorinated peptide, X = OMT (18) (IC50 = 10 mu M). Molecular m odeling indicated that this increased affinity may be attributable to new hydrogen-bonding interactions between the fluorine and the enzyme catalytic site, and not due to lowering of pK(a) values. In a competit ion binding assay using the p85 PI 3-kinase C-terminal SH2 domain GST fusion construct, the inhibitory peptide, Ac-D-X-V-P-M-L-amide, showed no enhancement of inhibitory potency for X = FOMT (22) (IC50 = 18 mu M) relative to the unfluorinated peptide, X = OMT (21) (IC50 = 14 mu M ). The use of FOMT would therefore appear to have particular potential for the development of PTP inhibitors.