Non-Imidazole Histamine H3 Ligands. Part VI. Synthesis and Preliminary Pharmacological Investigation of Thiazole-Type Histamine H3-Receptor Antagonists with Lacking a Nitrogen Nucleus in the Side Chain

Background: Antagonists to the H3 receptor are considered to be potential drugs for the treatment of Alzheimer’s disease, attention deficit-hyperactive disorder, memory and learning deficits, and epilepsy. The initial development of potent H3 receptor antagonists focused on extensive modification of the natural ligand histamine. However, it has appeared that imidazole-containing ligands are associated with inhibition of cytochrome P450 enzymes, caused by imidazole nitrogen complexation to heme iron in the active site of the enzyme. For these reasons, the development of potent non-imidazole H3 receptor antagonists was eagerly awaited. Keywords: Histamine H3-receptor/non-imidazole H3-antagonists/ 1-(2-thiazol-4-yl)- and 1-(2-thiazol-5-yl)-4-npropylpiperazines.