Evaluation of [11C]methyl-losartan and [11C]methyl-EXP3174 for PET imaging of renal AT1receptor in rats

Radiosynthesis of the 11C‐methyl derivative of LBQ657 for PET investigation of the neprilysin inhibitor sacubitril

“…18,19 In order to improve the RCY of the reaction, both methylating agents were tested, [ C]7 t R = 3.7 min), UV in black (λ = 254 nm, t R = 3.8 minutes) and the nonradioactive standard 7 in red (UV, λ = 254 nm, t R = 3.8 min). 11 C-Methylation was carried out in the presence of Kryptofix 222 and potassium carbonate.…”

“…Utilization of this cryptant was previously reported to enhance the reactivity of the base increasing the formation of the carboxylate ion for methylation. 18,19 In order to improve the RCY of the reaction, both methylating agents were tested, [ 11 . The difference in the retention times between radiation and UV detection is due to detectors being in series deprotection reaction times resulted in lower RCY, various concentrations of HCl were tested for the deprotection reaction, while minimizing the potential degradation of the 11 C-methyl ester derivative.…”

Synthesis and Evaluation of [18F]FEtLos and [18F]AMBF3Los as Novel 18F-Labelled Losartan Derivatives for Molecular Imaging of Angiotensin II Type 1 Receptors

“…Although a few PET AT 1 R radioligands have been evaluated for cardiovascular [39,40], renal [22][23][24][41][42][43][44] and brain [18,45] AT 1 R imaging, most of them were labeled with 11 C, which brings some disadvantages over 18 F in the clinical practice, such as the presence of an in-site cyclotron. Recently, it was reported the synthesis of [ 18 F]FPyKYNE-losartan (Figure 1), a losartan-derivative containing a hydrophobic motif that could favor a non-specific liver uptake [21].…”

“…PET imaging uses radiopharmaceuticals labelled with positron-emitting radioisotopes such as carbon-11 ( 11 C) and fluorine-18 ( 18 F). Several AT 1 R radioligands have been designed, synthesized and evaluated for molecular imaging of AT 1 receptors [15][16][17][18][19][20][21][22][23][24]. Most of these AT 1 R radioligands (Figure 1), mostly derivatives from commercial angiotensin receptor blockers (ARBs), were labeled with 11 C which is a drawback in the clinic practice due to the very short half-life of 20.4 min [25].…”

“…Therefore, we designed the novel analog [ 18 F]fluoroethyl-losartan ([ 18 F]FEtLos; Figure 2) following a similar reaction scheme to the one reported for [ 11 C]methyl-losartan ( Figure 1). [15][16][17][18][19][20][21][22][23][24]. Therefore, here we described the synthesis and 18 F-labeling of two novel losartan derivatives using less hydrophobic motifs such as: 2-fluoroethoxy and ammoniomethyltrifluoroborate (AMBF3), [ 18 F]FEtLos and [ 18 F]AMBF3Los, respectively ( Figure 2).…”