A new method for the synthesis of the highly selective delta opioid receptor (DOR) antagonist radiotracer N1 '-([11 C]methyl)naltrindole ([11 C]MeNTI) is described. The original synthesis required hydrogentation of a benzyl protecting group after 11 C-labeling, which is challenging in modern radiochemistry laboratories that tend to be heavily automated and operate according to current Good Manufacturing Practice. To address this challenge we describe development of a novel MeNTI precursor bearing a methoxymethyl acetal (MOM) protecting group which is easily removed with HCl, and employ it in an updated synthesis of [11 C]MeNTI. The new synthesis is fully automated and validated for clinical use. The total synthesis time is 45 min and provides [11 C]MeNTI in good activity yield (49 ± 8 mCi), molar activity (3926 ± 326 Ci/mmol) and radiochemical purity (97 ± 2%).

中文翻译：

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用于δ阿片受体正电子发射断层扫描成像的 N 1 '-([ 11 C]甲基)纳曲吲哚的更新合成

描述了一种合成高选择性δ阿片受体（DOR）拮抗剂放射性示踪剂N1'-（[11 C]甲基）纳曲吲哚（[11 C]MeNTI）的新方法。最初的合成需要在 11 C 标记后氢化苄基保护基团，这在现代放射化学实验室中具有挑战性，这些实验室往往高度自动化并根据当前的良好生产规范进行操作。为了应对这一挑战，我们描述了一种新型 MeNTI 前体的开发，该前体带有一个可以用 HCl 轻松去除的甲氧基甲基缩醛 (MOM) 保护基团，并将其用于 [11 C]MeNTI 的更新合成中。新的合成是完全自动化的，并且经过验证可用于临床。总合成时间为 45 分钟，并以良好的活性产率 (49 ± 8 mCi) 提供 [11 C]MeNTI，