Synthesis of selectively labeled histidine and its methylderivatives with deuterium, tritium, and carbon-14.

Isotopologues of l-histidine and its N-methylderivatives labeled with deuterium and tritium at the 5-position in the imidazole ring were obtained using the isotope exchange method. The deuterium-labeled isotopologues [5-(2)H]-l-histidine, [5-(2)H]-N(τ) -methyl-l-histidine, [5-(2)H]-N(π) -methyl-l-histidine, and [2,5-(2)H(2)]-l-histidine were synthesized by isotope exchange method carried out in a fully deuterated medium with. The same reaction conditions were applied to synthesize [5-(3)H]-N(τ) -methyl-l-histidine, [5-(3)H]-N(π) -methyl-l-histidine, and [5-(3)H]-l-histidine with specific activity of 2.0, 5.0, and 2.6 MBq/mmol, respectively. The N(π) -[methyl-(14)C]-histamine was obtained with specific activity of 0.23 MBq/mmol in a one-step reaction by the direct methylation of histamine by [(14)C]iodomethane.