Synthesis of Modified Tripeptides and Tetrapeptides as potential bisubstrate inhibitors of the epidermal growth factor receptor protein tyrosine kinase

Abstract

AbstractThe synthesis of a series of bisubstrate inhibitors of the epidermal growth factor receptor protein kinase (EGF‐R PTK) consisting of small pep tides linked covalently to adenosine via appropriate triphosphate substitutes is described. Boc‐Glu(OtBu)‐Tyr‐Leu‐OBzl (5) and Ac‐Glu(OtBu)‐Tyr‐Leu‐Arg(Pmc)‐NH2 (8; Pmc = 2,2,5,7,8‐pentamethylchroman‐6‐sulfonyl) were prepared by standard peptide chemistry, (Scheme 1), then modified at the OH group of tyrosine either with adipic anhydride or with 4‐(chlorosulfonyl)benzoic acid, 4‐(chlorosulfonyl)‐2‐hydroxybenzoic acid, or benzene‐1,4‐disulfonyldichloride (Scheme 2), and finally coupled with the 5′‐OH group of 2′,3′‐O‐isopropylideneadenosine (Scheme 3). In addition, N6‐[(benzyloxy)carbonyl]‐2′,3′‐O‐isopropylidene‐adenosine 5′‐(hydrogenhexanedioate) (26), an ATP substitute, was coupled with the morpholide of 5 (Scheme 4). Removal of the protecting groups gave the bisubstrate analogs 23, 24, and 28. The compounds synthesized were tested as inhibitors of the EGF‐R PTK. The most active bisubstrate‐type inhibitor was 24, composed of the tripeptide sequence H‐Glu‐Tyr‐Leu‐OBzl, the 2‐hydroxy‐4‐sulfonylbenzoyl moiety, and adenosine; it showed an IC50 value of 33 μM.