Synthesis and Structure-Activity Relationships of Pyridoxal-6-arylazo-5′-phosphate and Phosphonate Derivatives as P2 Receptor Antagonists

摘要

Novel analogs of the P2 receptor antagonist pyridoxal-5′-phosphate-6-phenylazo-2′,4′-disulfonate (PPADS) were synthesized. Modifications were made through functional group substitution on the sulfophenyl ring and at the phosphate moiety through the inclusion of phosphonates, demonstrating that a phosphate linkage is not required for P2 receptor antagonism. Substituted 6-phenylazo and 6-naphthylazo derivatives were also evaluated. Among the 6-phenylazo derivatives, 5′-methyl, ethyl, propyl, vinyl, and allyl phosphonates were included. The compounds were tested as antagonists at turkey erythrocyte and guinea-pig taenia coli P2Y1 receptors, in guinea-pig vas deferens and bladder P2X1 receptors, and in ion flux experiments by using recombinant rat P2X2 receptors expressed in Xenopus oocytes. Competitive binding assay at human P2X1 receptors in differentiated HL-60 cell membranes was carried out by using [³⁵S]ATP-γ-S. A 2′-chloro-5′-sulfo analog of PPADS (C14H12O9N3ClPSNa), a vinyl phosphonate derivative (C15H12O11N3PS2Na3), and a naphthylazo derivative (C18H14O₁₂N₃PS₂Na₂), were particularly potent in binding to human P2X₁ receptors. The potencies of phosphate derivatives at P2Y₁ receptors were generally similar to PPADS itself, except for the p-carboxyphenylazo phosphate derivative C₁₅H₁₃O₈N₃PNa and its m-chloro analog C₁₅H₁₂O₈N₃ClPNa, which were selective for P2X vs. P2Y₁ receptors. C₁₅H₁₂O₈N₃ClPNa was very potent at rat P2X₂ receptors with an IC₅₀ value of 0.82 μM. Among the phosphonate derivatives, [4-formyl-3-hydroxy-2-methyl-6-(2-chloro-5-sulfonylphenylazo)-pyrid-5-yl]methylphosphonic acid (C₁₄H₁₂-O₈N₃ClPSNa) showed high potency at P2Y₁ receptors with an IC₅₀ of 7.23 μM. The corresponding 2,5-disulfonylphenyl derivative was nearly inactive at turkey erythrocyte P2Y₁ receptors, whereas at recombinant P2X₂ receptors had an IC₅₀ value of 1.1 μM. An ethyl phosphonate derivative (C₁₅H₁₅O₁₁N₃PS₂Na₃), whereas inactive at turkey erythrocyte P2Y₁ receptors, was particularly potent at recombinant P2X₂ receptors.