Radiosynthesis of N5-[18F]fluoroacetylornithine (N5-[18F]FAO) for PET imaging of ornithine decarboxylase (ODC) in malignant tumors
作者:Nashaat Turkman、Juri G. Gelovani、Mian M. Alauddin
DOI:10.1002/jlcr.1799
日期:2011.1
Polyamines are naturally occurring polycations derived from amino acids via decarboxylation by ornithine decarboxylase (ODC). Ornithine is a substrate for ODC; decarboxylation of ornithine is inhibited by difluoromethylornithine (DFMO) and its derivatives. Polyamine contents are increased in many epithelial cancers, including breast cancer, melanoma, and prostate cancer. In order to image and measure the levels of ODC expression in malignant tumors, we have synthesized a derivative of ornithine, N5-[18F]fluoroacetylornithine (N5-[18F]FAO), for use in positron emission tomography. The precursor compound N2-Boc-N5-bromoacetylornithine-t-butyl ester 2 was synthesized from 5-amino-2-(tert-butoxycarbonylamino)pentanoic acid, which was reacted with bromoacetyl chloride followed by esterification with tert-butyl-2,2,2-trichloroacetamidate. Fluorination of the precursor produced a fluoro-derivative, which was hydrolyzed in acid to obtain the desired compound, N5-fluoroacetylornithine. The radiosynthesis of N5-[18F]FAO was accomplished by radiofluorination of 2 with n-Bu4N[18F], followed by high-performance liquid chromatography (HPLC) purification and then by acid hydrolysis. The radiochemical yield was 6–10% (decay corrected) with an average of 8% (n=10) at the end of synthesis. The radiochemical purity was >99%, and specific activity was >1500 mCi/µmol. The synthesis time was 95–100 min from the end of bombardment. Copyright © 2010 John Wiley & Sons, Ltd.
多胺是一类天然存在的多价阳离子,来源于氨基酸,通过鸟氨酸脱羧酶(ODC)的脱羧作用形成。鸟氨酸是ODC的底物;鸟氨酸的脱羧作用被双氟甲基鸟氨酸(DFMO)及其衍生物抑制。许多上皮癌中的多胺含量增加,包括乳腺癌、黑色素瘤和前列腺癌。为了成像和测量恶性肿瘤中ODC的表达水平,我们合成了一种鸟氨酸衍生物,N5-[18F]氟乙酰鸟氨酸(N5-[18F]FAO),用于正电子发射断层扫描。前体化合物N2-Boc-N5-溴乙酰鸟氨酸-叔丁酯2是通过5-氨基-2-(叔丁氧羰基氨基)戊酸与溴乙酰氯反应,然后与叔丁基-2,2,2-三氯乙酰胺酯化得到的。前体的氟化产生了氟衍生物,该衍生物在酸性条件下水解,得到所需的化合物,N5-氟乙酰鸟氨酸。N5-[18F]FAO的放射合成是通过2与n-Bu4N[18F]的放射氟化实现的,随后进行高效液相色谱(HPLC)纯化,然后进行酸水解。放射化学产率为6-10%(衰减校正),平均为8%(n=10)在合成结束时。放射化学纯度>99%,比活性>1500 mCi/µmol。合成时间从轰击结束开始为95-100分钟。版权所有 © 2010 John Wiley & Sons, Ltd.