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High-yield synthesis of a tau PET radioligand and its nonradioactive ligand using an alternative protection and deprotection strategy.
- Source :
-
Journal of labelled compounds & radiopharmaceuticals [J Labelled Comp Radiopharm] 2021 Apr; Vol. 64 (4), pp. 150-158. Date of Electronic Publication: 2020 Nov 26. - Publication Year :
- 2021
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Abstract
- Recently developed tau imaging radiopharmaceuticals show specific uptake in tau protein-rich regions in human brains without off-target binding. These radiopharmaceuticals and their nonradioactive reference ligands are generally obtained in low (radio)chemical yields. In the present study, we investigated high-yield synthesis of <superscript>18</superscript> F-RO948 ([ <superscript>18</superscript> F]1) and its nonradioactive ligand (1). The ligand 1 was synthesized by a Suzuki-Miyaura coupling reaction between 9-(4-methoxybenzyl)-9H-pyrrolo[2,3-b:4,5-c']dipyridin-2-yl trifluoromethanesulfonate (3) and 2-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (4), followed by oxidative removal of the para-methoxybenzyl (PMB) group with ceric ammonium nitrate (CAN). This two-step reaction gave 1 in 55.8% yield. The precursor for [ <superscript>18</superscript> F]1 was synthesized from 3 and 2-nitro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (6). The resulting PMB-protected precursor 8 was obtained in 74.5% yield. [ <superscript>18</superscript> F]1 was synthesized by radiofluorination of 8 (radiochemical conversion (RCC): 95.7 ± 1.7%), followed by deprotection of the PMB group with CAN. This one-pot, two-step radiochemical synthesis followed by HPLC purification gave [ <superscript>18</superscript> F]1 in high decay-corrected radiochemical yield (54-60%). The RCC of [ <superscript>18</superscript> F]fluoride to [ <superscript>18</superscript> F]1 in our two-step synthesis method was similar to that in a one-step radiofluorination reaction of a tert-butoxycarbonyl (BOC)-protected precursor 10 that proceeds with concomitant thermal deprotection of the BOC group. Taken together, the results of this study suggest that this high-yield synthesis method is useful for the synthesis of <superscript>18</superscript> F-labeled (NH)heteroarene compounds.<br /> (© 2020 John Wiley & Sons, Ltd.)
Details
- Language :
- English
- ISSN :
- 1099-1344
- Volume :
- 64
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Journal of labelled compounds & radiopharmaceuticals
- Publication Type :
- Academic Journal
- Accession number :
- 33125755
- Full Text :
- https://doi.org/10.1002/jlcr.3894