Abstract
New derivatives of the closo-decaborate anion [B(10)H(9)-O(CH(2))(2)O(CH(2))(3)C(O)-L-OCH(3)](2-) (An) (1: L = Trp; 2: L = His; 3: L = Met; 4: L = Ala(2-oxopyrrolidin-3-yl) (Pld) were synthesized and isolated as tetraphenylphosphonium salts (Ph(4)P)(2)An. Anions 1(2-); 2(2-); 3(2-), and 4(2-) contain a pendant functional group from the L-tryptophan methyl ester, L-histidine methyl ester, L-methionine methyl ester, or methyl 2-amino-3-(2-oxopyrrolidin-3-yl)propanoate (-Trp-OCH(3), -His-OCH(3), -Met-OCH(3), or -Pld-OCH(3)) residue, respectively, bonded with the boron cluster anion through the oxybis[(ethane-2,1-diyl)oxy] spacer. This pacer is formed as a result of the nucleophilic opening of the attached dioxane molecule in the [B(10)H(9)O(CH(2))(4)O](-) starting derivative. Sodium salts of the target compounds were isolated and used in biological experiments. It was established that among compounds Na(2)An (An = 1-4), not all are capable of inhibiting the cytopathic effect of the virus in vitro. Sodium salts Na(2)An have a low toxic effect on a monolayer of continuous canine embryonic kidney (MDCK) cell line. Compounds Na(2)1 and Na(2)2 had IC(50) of 5.0 and 20.0 μg/mL, respectively, while for compounds Na(2)3 and Na(2)4, IC(50) values could not be achieved at the concentrations studied. The studies performed for molecular docking of the anionic part of 1(2-) and 2(2-) with the transmembrane domain of viroporin M2 show some differences in the location of these two ligands inside the M2 canal pore.