LBT-999 (8-((E)-4-fluoro-but-2-enyl)-3-beta-p-tolyl-8-aza-bicyclo[3.2.1]octane-2-beta-carboxylicacid methyl ester) is a recently developed cocaine derivative belonging to a new generation of highly selective dopamine transporter (DAT) ligands (KD: 9 nM for the DAT and IC50 > 1000 nM for the serotonin and norepinephrine transporter). Initial fluorine-18-labelling of LBT-999 was based on the robust and reliable two-step radiochemical pathway often reported for such tropane derivatives, involving first the preparation of (E)-1-[18F]fluoro-4-tosyloxybut-2-ene followed by a N-alkylation reaction with the appropriate nor-tropane moiety. In the present work, a simple one-step fluorine-18-labelling of LBT-999 is reported, based on a chlorine-for-fluorine nucleophilic aliphatic substitution, facilitating as expected both automation and final high-performance liquid chromatography (HPLC) purification. The process involves: (A) reaction of K[18F]F–Kryptofix®222 with the chlorinated precursor (3.5–4.5 mg) at 165°C for 10 min in DMSO (0.6 mL) followed by (B) C-18 PrepSep cartridge pre-purification and finally (C) semi-preparative HPLC purification on a Waters Symmetry® C-18. Typically, 3.70–5.92 GBq of [18F]LBT-999 (> 95% chemically and radiochemically pure) could be obtained with specific radioactivities ranging from 37 to 111 GBq/µmol within 85–90 min (HPLC purification and Sep-Pak-based formulation included), starting from a 37.0 GBq [18F]fluoride batch (overall radiochemical yields: 10–16%, non-decay-corrected). Copyright © 2007 John Wiley & Sons, Ltd.
LBT-999(8-((E)-4-
氟-丁-2-烯基)-3-β-
对甲苯基-8-氮杂
双环[3.2.1]辛烷-2-β-
羧酸甲酯)是最近开发的一种
可卡因衍
生物,属于新一代高选择性
多巴胺转运体(
DAT)
配体(
DAT 的 KD:9 nM,5-羟
色胺和
去甲肾上腺素转运体的 IC50 > 1000 nM)。LBT-999 最初的
氟-18 标记是基于此类托烷衍
生物经常报道的稳健可靠的两步放射
化学途径,首先制备 (E)-1-[18F]
氟-4-tosyloxybut-2-ene,然后与适当的正托烷分子进行 N- 烷基化反应。本研究报告了一种简单的一步法
氟-18 标记 LBT-999,该方法基于
氯对
氟的亲核脂肪族取代,有助于实现自动化和最终的高效
液相色谱(HPLC)纯化。该过程包括:(A) K[18F]F-Kryptofix®222 与
氯化前体(3.5-4.5 毫克)在 165°C 下于
DMSO(0.6 毫升)中反应 10 分钟,然后 (B) C-18 PrepSep 滤芯预纯化,最后 (C) 在 Waters Symmetry® C-18 上进行半制备型 HPLC 纯化。通常情况下,从 37.0 GBq [18F]
氟化物批次开始,在 85-90 分钟内可获得 3.70-5.92 GBq [18F]LBT-999(
化学纯度和放射
化学纯度大于 95%),特定放射性活度范围为 37-111 GBq/µmol(包括 HPLC 纯化和基于 Sep-Pak 的配方)(总体放射
化学收率:10-16%,非衰变校正)。Copyright © 2007 John Wiley & Sons, Ltd. All Rights Reserved.