4‐[¹⁸F]fluorophenyl ureas via carbamate‐4‐nitrophenyl esters and 4‐[¹⁸F]fluoroaniline

Abstract

Four different no carrier added (n.c.a.) 4‐[18F]fluorophenylurea derivatives are synthesized as model compounds via two alternative routes. In both cases carbamate‐4‐nitrophenylesters are used as intermediates. Either n.c.a. 4‐[18F]fluoroaniline reacts with carbamates of several amines, or the carbamate of n.c.a. 4‐[18F]fluoroaniline is formed at first and an amine is added subsequently to yield the urea derivative. The choice of the appropriate way of reaction depends on the possibilities of precursor synthesis.The radiochemical yields reach up to 80% after 50 min of synthesis time while no radiochemical by‐products can be determined. These high yields were possible due to an optimized preparation of n.c.a. 4‐[18F]fluoroaniline with a radiochemical yield of up to 90%. From the various ways of its radiosynthesis, the substitution with n.c.a. [18F]fluoride on dinitrobenzene is chosen, using phosphorous acid and palladium black for reduction of the second nitro group. Copyright © 2006 John Wiley & Sons, Ltd.

The synthesis and biological evaluation of para-substituted phenolic N-alkyl carbamates as endocannabinoid hydrolyzing enzyme inhibitors

“…The majority of the carbamates were obtained by treating various phenols with suitable alkyl isocyanates in the presence of triethylamine; the O-phenyl carbamates 9-29, 30 [51], 31-33, 35 [53,54], 37-39 [55], 40 [52,55], 41, 42 [53,56], 43 [57], 44, 46, and 48-51 were prepared from the corresponding phenols, and in the case of N-phenyl carbamate 52, from cyclohexanol by a route described in Schemes 1 and 2. On the contrary, the O-phenyl carbamates 34 [52,55,[58][59][60] and 36 [61] were prepared from 4-nitrophenyl chloroformate and the appropriate amine, yielding the desired products in 32-99% yield, with shorter reaction time than in the isocyanate method. The O-phenyl N-n-hexylcarbamates 45 and 47 were prepared from the corresponding methyl benzoates (Scheme 2).…”

Rhodium‐mediated [11C]carbonylation: a library of N‐phenyl‐N′‐{4‐(4‐quinolyloxy)‐phenyl}‐[11C]‐urea derivatives as potential PET angiogenic probes

“…14 These derivatives offer different labelling approaches at various positions and with different positron emitters such as 18 F (b 1 , t 1/2 = 109.8 min) or 11 C (b 1 , t 1/2 = 20.4 min) ( Figure 1). General 18 F-labelling procedure of diaryl-urea containing molecules using either 4-nitrophenyl chloroformate 15 or triphosgene 16 was developed. In the latter article, complete chemical characterization, evaluation of receptor phosphorylation inhibitory potency and selectivity toward other RTKs were described.…”

Metabolic stability of 6,7-dialkoxy-4-(2-, 3- and 4-[18F]fluoroanilino)quinazolines, potential EGFR imaging probes

“…27–30 The incorporation of [ 18 F]fluoride into the 1,3-substituted dinitrobenzene has historically been a low yielding (< 17%) reaction. 27 The use of 3-nitro- N , N , N -trimethylanilinium triflate gave 3-[ 18 F]fluoronitrobenzene in reasonable yield (44 ± 4 %) after 5 min using a modified method.…”