title: Potent P2X7Receptor Antagonists: Tyrosyl Derivatives Synthesized Using a Sequential Parallel Synthetic Approach.
abstract: Novel analogs of 1-(N,O-bis[5-isoquinolinesulfonyl]-N-methyl-L-tyrosyl)-4-phenylpiperazine (KN-62,1) were synthesized and found to be potent antagonists in a functional assay, inhibition of ATP-induced K+efflux in HEK293 cells expressing recombinant human P2X7receptors. Antagonism of murine P2X7receptors was also observed. The analogs consisted of L-tyrosine derivatives, of the general structure R1-Tyr(OR2)-piperazinyl-R3, in which three positions were systematically varied in structure through facile acylation reactions. Each of the three positions was optimized in sequence through parallel synthesis alternating with biological evaluation, leading to the identification and optimization of potent P2X7antagonists. The optimal groups at R1were found to be large hydrophobic groups, linked to the α-amino position through carbamate, amide, or sulfonamide groups. The benzyloxycarbonyl (Cbz) group was preferred over most sulfonamides and other acyl groups examined, except for quinoline sulfonyl. At R2, an arylsulfonate ester was preferred, and the order of potency was p-tolyl, p-methoxyphenyl, phenyl > α-naphthyl, β-naphthyl. A benzoyl ester was of intermediate potency. Aliphatic esters and carbonate derivatives at the tyrosyl phenol were inactive, while a tyrosyl O-benzyl ether was relatively potent. The most potent P2X7receptor antagonists identified in this study contained Cbz at the R1position, an aryl sulfonate at the R2position, and various acyl groups at the R3position. At R3,t-butyloxycarbonyl- and benzoyl groups were preferred. The opening of the piperazinyl ring to an ethylene diamine moiety abolished antagonism. In concentration-response studies, a di-isoquinolinyl, Boc derivative,4(MRS2306), displayed an IC50value of 40 nM as an antagonist of P2X7receptor-mediated ion flux and was more potent than the reference compound1. Nα-Cbz, Boc-piperazinyl derivatives,11(MRS2317),22(MRS2326), and41(MRS2409) were less potent than1, with IC50values of 200-300 nM.
authors.affiliation: Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.
authors.forename: R Gnana
authors.initials: RG
authors.lastname: Ravi
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio.
authors.forename: Sylvia B
authors.initials: SB
authors.lastname: Kertesy
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio.
authors.forename: George R
authors.initials: GR
authors.lastname: Dubyak
authors.affiliation: Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Jacobson
keywords: KN-62; ion channels; isoquinolines; nucleotides; purines; structure activity relationships