Monocarboxylic-based phosphotyrosyl mimetics in the design of Grb2 SH2 domain inhibitors

Three monocarboxylic-containing analogues, O-carboxymethyltyrosine (cmT, 5), 4-(carboxymethyl)phenylalanine (cmF, 6), and 4-(carboxydifluoromethyl)phenylalanine (F(2)cmF, 7) were utilized as phosphotyrosyl (pTyr) replacements in a high affinity a-bend mimicking platform, where they exhibited IC50 values of 2.5 mu M, 65 mu M and 28 mu M, respectively, in a Grb2 SH2 domain Biacore binding assay. When a terminal Na-oxalyl axillary was utilized to enhance ligand interactions with a critical SH2 domain Arg67 residue (alpha A-helix), binding potencies increased from 4- to 10-fold, resulting in submicromolar affinity for cmF (IC50 = 0.6 mu M) and low micromolar affinity for F(2)cmF (IC50 = 2 mu M) Cell lysate binding studies also showed inhibition of cognate Grb2 binding to the p185(erbB-2) phosphoprotein in the same rank order of potency as observed in the Biacore assay. These results indicate the potential value of cmF and F(2)cmF residues as pTyr mimetics for the study of Grb2 SH2 domains and suggest new strategies for improvements in inhibitor design. (C) 1999 Published by Elsevier Science Ltd.