Water-Soluble Pyrazolo[4,3-<i>e</i>][1,2,4]triazolo[1,5-<i>c</i>]pyrimidines as Human A<sub>3</sub> Adenosine Receptor Antagonists
作者:Pier Giovanni Baraldi、Giulia Saponaro、Romeo Romagnoli、Mojgan Aghazadeh Tabrizi、Stefania Baraldi、Allan R. Moorman、Sandro Cosconati、Salvatore Di Maro、Luciana Marinelli、Stefania Gessi、Stefania Merighi、Katia Varani、Pier Andrea Borea、Delia Preti
DOI:10.1021/jm300323t
日期:2012.6.14
A relevant problem of the pyrazolo[4,3-e]-[1,2,4]triazolo[1,5-c]pyrimidine nucleus, an attractive scaffold for the preparation of adenosine receptor antagonists, is the low water solubility. We originally functionalized the C-5 position with a salifiable 4-pyridylcarbamoyl moiety that conferred good water solubility at low pH (<4.0) but poor solubility at physiologic pH, indicative of the dissociation of the pyridinium species. Here we replaced the pyridin-4-yl moiety with a 1-(substituted)piperidin-4-yl ring to exploit the higher basicity of this nucleus and for the the possibility to generate stable, water-soluble salts. The hydrochloride salt of the 1-(cyclohexylmethyl)piperidin-4-yl derivative (10, K-i(hA(3)) = 9.7 nM, IC50(hA(3)) = 30 nM, K-i(hA(1)/hA(3)) = 351, K-i(hA(2A)/hA(3)) > 515, IC50(HA(2B)) > 5 mu M) showed a solubility of 8 mg/mL at physiological pH and gave a stable aqueous system suitable for, intravenous infusion. Molecular modeling studies were helpful in rationalizing the available structure-activity relationships and the selectivity profile of the new ligands.