抄録
d-Dethiobiotin tritiated at selective positions can be prepared by reductive desulfurization of d-biotin with Raney nickel catalyst. Three combinations of the solvent (water) and the catalyst (Raney nickel) were examined as follows : 1) Tritiated water and ordinal Raney nickel (W-2) 2) Tritiated water and 3H2 gas-adsorbed Raney nickel 3) Non-labeled water, and Raney nickel adsorbed with tritium gas. Although d-dethiobiotin was labeled with tritium by any of these combinations, labeled products with high specific radioactivity were obtained with 3H2-adsorbed Raney nickel in 2) and 3). In order to clarify whether the tritium incorporated into 3H-d-dethiobiotin is derived from tritium water or 3H2-adsorbed catalyst, the tritiation mechanisms were investigated. Tritium atoms were shown to be freely interchangeable between the solvent (3H2O) and the catalyst (3H2-adsorbed Raney nickel) during the catalytic desulfurization of d-biotin. The tritiated d-dethiobiotin obtained was assumed to be predominantly 5-methyl[3H]-2-oxo-4-imidazolidinehexanoic [6-methylene-3H] acid from infrared and nuclear magnetic resonance data of 2H-d-dethiobiotin prepared by the reductive deuterization of d-biotin using an analogous method.
