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This paper describes an efficient synthesis of fluorobenzyloxoimidazolidinone derivatives. The title compounds 1a, 1b and 1c could be prepared with high diasteromeric purity (>99%) and overall yields of 19%, 48% and 41% in a ten or six-step synthetic procedure, respectively. These compounds are used as precursors for isotopic 18F-labelling. 相似文献
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Synthesis of no-carrier-added 4-[18F]fluorophenol from 4-benzyloxyphenyl-(2-thienyl)iodonium bromide
4-[(18)F]Fluorophenol is a versatile synthon for the synthesis of more complex radiopharmaceuticals bearing a 4-[(18)F]fluorophenoxy moiety. In order to prepare 4-[(18)F]fluorophenol in no-carrier-added (n.c.a.) form only a nucleophilic labelling method starting from [(18)F]fluoride is suitable. In this paper a new, two step radiosynthesis starting from 4-benzyloxyphenyl-(2-thienyl)iodonium bromide and [(18)F]fluoride with subsequent deprotection is described, yielding n.c.a. [(18)F]fluorophenol in 34 to 36% radiochemical yield. 相似文献
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2-[(18)F]Fluoro-L-phenylalanine and 2-[(18)F]fluoro-L-tyrosine have been developed as promising radiopharmaceuticals for molecular imaging using positron emission tomography (PET). However, the lack of a convenient radiosynthetic pathway has limited their practical use. In this work a new three-step nucleophilic synthesis of these compounds starting from [(18)F]fluoride is described. Corresponding precursors (1a and 1b) were (18)F-fluorinated by isotopic exchange, followed by the removal of an activating formyl group with Rh(PPh(3))(3)Cl and subsequent hydrolysis of protecting groups in acidic medium. All reactions were carried out using both conventional and microwave heating. Conventional heated reactions yielded the desired products 2-[(18)F]Fphe and 2-[(18)F]Ftyr in 43% and 49% whereas radiochemical yields of 34% and 43%, respectively, were obtained when they were heated by microwaves. Under optimized conditions the enantiomeric purity was ≥94% for both radiopharmaceuticals. 相似文献
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V. R. Bom P. C. Coops R. W. Hollander E. Coenen K. Deneffe P. Van Duppen M. Huyse 《Zeitschrift für Physik A Hadrons and Nuclei》1986,325(2):149-155
Theβ +-spectra of the neutron deficient indium nuclei, produced in the reactionnatMo(16O,pxn), have been measured using a solid state beta detector, and mass separated sources. Values forQ EC have been determined for105–108In anc for105Cd and106Ag. 相似文献
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Oscillatory flow about a pair of circular cylinders is considered.The distance between the cylinders can be varied as can theangle that the undisturbed oscillatory flow makes with the linejoining the cylinder centres. In common with other fluid flowsdominated by oscillatory flow, a time-independent, or steadystreaming, motion develops. Attention is focused on the caseof high streaming Reynolds numbers and the resulting jets thaterupt from the surfaces of the cylinders. 相似文献
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In order to study the effect of substitution of Fe3+ by Al3+ and Cr3+ in Li0.5Fe2.5O4 on its structural and magnetic properties, the spinel system Li0.5Al x Cr x Fe2.5?2x O4 (x=0.0, 0.2, 0.4, 0.5, 0.6 and 0.8) has been characterized by X-ray diffraction, high field magnetization, low field ac susceptibility and 57Fe Mossbauer spectroscopy. Contrary to the earlier reports, about 50% of Al3+ is found to occupy the tetrahedral sites. The system exhibits canted spin structure and a central paramagnetic doublet was found superimposed on magnetic sextet in the Mössbauer spectra (x>0.5). 相似文献
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In situ generated iodine monofluoride (IF) has for the first time been used on sub-micromolar scale for iodination of model arenes. Reactivity and selectivity of the reagent have been determined by the radiotracer method using [123,131I]IF. 相似文献