Targeting the ribose and phosphate binding site of p38 mitogen-activated protein (MAP) kinase: synthesis and biological testing of 2-alkylsulfanyl-, 4(5)-aryl-, 5(4)-heteroaryl-substituted imidazoles.

Three series of substituted 2-alkylsulfanyl-4-(4-fluorophenyl)imidazoles, 5-pyridinyl-, 1-methyl-5-pyridinyl-, and 5-(2-aminopyridin-4-yl)-imidazoles, were prepared and tested for their ability to inhibit p38 MAP kinase and TNF-alpha release. These compounds were prepared by using different synthetic routes. They were tested by applying a nonradioactive p38 MAP kinase assay and by measurement of TNF-alpha release in human whole blood. Potent inhibitors (IC50 values in the low nanomolar range, as low as 2 nM in the enzyme assay and 37 nM in the human whole blood test) were identified by variation of substituents at the imidazole- C2-thio position as well as at the 2-aminopyridinyl functionality. In contrast to other known kinase inhibitors, these novel imidazole derivatives with the substituents at the imidazole-C2-thio position may interact with the ribose as well as with the phosphate binding site of the p38 MAP kinase.