Synthesis and evaluation of copper complexes of Schiff-base condensates from 5-substituted-2-hydroxybenzaldehyde and 2-substituted-benzenamine as selective inhibitors of protein tyrosine phosphatases

Five copper complexes, [Cu(bhbb,chbb,nhbb)(H2O)n] (tridentate-ligands: H2bhbb = 2-(5-bromo-2-hydroxylbenzylideneamino)benzoic acid, 1; H2chbb = 2-(5-chloro-2-hydroxylbenzylideneamino)benzoic acid, 2; H2nhbb = 2-(5-nitro-2-hydroxyl-benzylideneamino)benzoic acid, 3) and [Cu(cpmp,npmp)2] (bidentate-ligands: Hcpmp = 4-chloro-2-((phenylimino)methyl)phenol, 4; Hnpmp = 4-bromo-2-((phenyl-imino)methyl)phenol, 5) have been prepared and characterized by EA, IR, EPR UV–Vis, and ESI-MS. Structure–activity relationship of copper complexes in inhibiting protein tyrosine phosphatases (protein tyrosine phosphatase 1B, PTP1B; T-cell protein tyrosine phosphatase, TCPTP; megakaryocyte protein-tyrosine phosphatase, PTP-MEG2; Src homology phosphatase 1, SHP-1 and Src homology phosphatase 2, SHP-2) is investigated. Inhibitory activities of complexes against the five PTPs indicate that they potently inhibit PTP1B, TCPTP, PTP-MEG2 and SHP-1, but do not inhibit SHP-2. In the complexes, 5 exhibits very strong inhibition (IC50, 0.059 μM) and better selectivity against PTP1B while 1 and 2 show very strong inhibition (IC50 = 0.089 and 0.067 μM) and a little selectivity against TCPTP. Compared with the oxovanadium(IV) complexes of same ligands, the copper complexes increase the inhibitory ability against TCPTP, PTP-MEG2 and SHP-1 but decrease the inhibition against SHP-2. For complex 5, the inhibition over PTP1B, TCPTP, PTP-MEG2 and SHP-1 are all improved about 5- to 15-fold compared with the oxovanadium(IV) complex. The results demonstrate that both the ligand structures and the center metals influence the inhibition and selectivity against different PTPs.