Synthesis and testing of a p-H2 hyperpolarized 13C probe based on the pyrazolo[1,5-a]pyrimidineacetamide DPA-713, an MRI vector to target the peripheral benzodiazepine receptors
✍ Scribed by Erika Cerutti; Alessandra Viale; Annelaure Damont; Frédéric Dollé; Silvio Aime
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 156 KB
- Volume
- 49
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.2839
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✦ Synopsis
DPA‐713 is the lead compound of a recently developed 2‐phenylpyrazolo[1,5‐a]pyrimidineacetamide series that has been shown to display a good targeting capability toward peripheral benzodiazepine receptors, recently renamed translocator protein (18 kDa) or in short TSPO. On the basis of this structure, a novel derivative bearing a [^13^C]butynoate moiety has been designed and synthesized (three steps—42% overall yield) providing, upon rapid and quantitative para‐hydrogenation, the corresponding hyperpolarized [^13^C]alkene. Para‐hydrogen‐induced polarization effects have been detected in both ^1^H and ^13^C‐NMR spectra. Upon applying a field cycling procedure, the spin order of para‐H~2~ added hydrogens is transferred on the ^13^ C carboxylate moiety yielding a signal enhancement of approximately 4500 times. T~1~ of the carboxylate carbon atom is approximately 21.9 s (at 9.37 T). A ^13^ C‐MR image has been acquired by using the ^13^ C RARE (Rapid Acquisition by Relaxation Enhancement) acquisition protocol on a 10‐mM solution. The main limitation to the in vivo use of this novel para‐hydrogenated [^13^ C]derivative is its relatively low solubility in aqueous systems. Copyright © 2011 John Wiley & Sons, Ltd.