1H-Imidazole-4-ethanamine 2-(4-imidazolyl)ethylamine 4-(2-Aminoethyl)-1H-imidazole 4-Imidazoleethylamine 5-Imidazoleethylamine 51-45-6 HSM Histamine Histamine Base beta-aminoethylimidazole beta-aminothethylglyoxaline