Metabolism, environmental fate, and low concentration food residue studies would be facilitated by the use of radiolabeled test articles that can be readily quantified within complex matrices. However, radiochemical approaches for such studies require high specific activities to allow analytical detection of correspondingly low masses of test article. The synthesis of high specific activity (>50 μCi/μmol) [14C]-radiolabeled phenylbutazone presents a challenge using existing methodology, mainly due to the low solvent volumes required and vigorous refluxing needed to close the pyrazolidinedione ring. Herein, we report on the significant modification of an existing method that allows the synthesis of low masses of high specific activity (>50 μCi/μmol) [14C]-phenylbutazone under mild conditions with simple purification and high yield. The closure of the pyrazolidinedione ring of 1,2-diphenyl-3,5-pyrazolidinedione was accomplished as a first step with unlabeled 1,2-diphenylhydrazine and diethyl malonate in 32% yield under gram-scale conditions, which avoided the challenges of low solvent use and vigorous refluxing. Low mass of high specific activity n-[1-14C]-butyl bromide was then added via a nucleophilic substitution reaction as a final step. Yields ranged from 65% to 92% during multiple synthetic attempts with unlabeled butyl bromide and were greatly influenced by reaction stoichiometry and the selection of base.
代谢、环境命运和低浓度食品残留物研究可以通过使用可在复杂基质中易于定量的放射性标记测试物来促进。然而,这类研究所需的放射
化学方法要求具有高比活性,以便对相应低质量的测试物进行分析检测。合成高比活性(>50 μCi/μmol)的[14C]-标记苯基丁氮(phenylbutazone)在现有方法中面临挑战,主要是由于所需的低溶剂体积和紧缩
吡唑烷二酮环(pyrazolidinedione)所需的剧烈回流。在此,我们报告了一种显著改进的现有方法,允许在温和条件下合成低质量的高比活性(>50 μCi/μmol)[14C]-苯基丁氮,且纯化简单、产率高。首先,以非标记的1,2-二苯
肼(1,2-diphenylhydrazine)和二
乙基马来酸酯(diethyl malonate)在克级条件下以32%的产率完成了
吡唑烷二酮环的闭合,从而避免了低溶剂使用和剧烈回流的挑战。然后,通过亲核取代反应将低质量的高比活性n-[1-14C]-
溴丁烷(butyl bromide)添加为最后一步。在多次合成尝试中,非标记的
溴丁烷的产率范围为65%到92%,受反应
化学计量比和碱的选择的显著影响。