13N-ammonia

Nitrogen-13 labelled / -phenethylamine [13N]-309 has been synthesized294 by Hoffman rearrangement of [13N]phenylpropionamide, prepared in turn from phenylpropio-nyl chloride and aqueous [13N]ammonia solution (equation 127). 

The higher yields of amides achieved by using organic solution of [13N]ammonia as a precursor are due to the higher stability and higher reactivity of the acid chlorides in organic solvents compared with water and because ammonia in water is hydrated and is less reactive. 

The administered 13N-amines are rapidly transferred to the tissues and oxidized by MAO to 13N-ammonia and an aldehyde which is rapidly oxidized to an acid. Some of the acids undergo further metabolism, such as -oxidation, which can be traced by using C-fatty acids297, or are excreted as such298. 13N-ammonia produced by MAO from... 

What are the clinical uses of 18F-FDG, 18F-FLT, 6-18F-L-Fluorodopa, lsO-Water, 13N-Ammonia, 11C-Sodium acetate, and 11C-Methylspiperone. 

Welch MJ, Kilbourn MR (1985). A remote system for the routine production of oxygen-15 radiopharmaceuticals. J Label Comp Radiopharm 22 1193 Wester HJ, Herz M, Weber W et al (1999). Synthesis and radiopharmacology of 0-2-[18F] fluoroethyl-L-tyrosine for tumor imaging. J Nucl Med 40 205 Wieland D, Bida G, Padgett H et al (1991). In-target production of [13N]ammonia via proton irradiation of dilute aqueous ethanol and acetic acid mixtures. Appl Radiat Isot 42 1095... 

Includes [i N]ammonia in cerebral blood as well as in brain sample. Since [13N]ammonia is continuously infused into the cerebral circulation until the moment of sacrifice, an indeterminate amount of [ N]ammonia will necessarily be trapped with the vascular component of the brain sample. 

Interestingly, hydroboration-amination as an isotope incorporation methodology has led to the synthesis of isomerically pure 13N- and 15N-labeled primary amines from labeled ammonia [23-25] (Scheme 8). These labeled amines are valuable intermediates in pharmacology. 

Nitrogen-13-labeled ammonia (ty2 = 10 min) is produced by reduction of 13N-labeled nitrates and nitrites that are produced by proton irradiation of water in a cyclotron. The reduction is carried out with titanium chloride in alkaline medium. 13N-NH3 is then distilled and finally trapped in acidic saline solution. Wester et al (1991) has used a pressurized target of aqueous ethanol, in which ethanol acts as a hydroxyl free radical scavenger to improve the... 

The radio-labelled PEP experiments have shown that the pre-adsorbed oxygen favours the dissociation of ammonia, which leads to production of N2, N2O and NO. The product selectivity strongly depends on the temperature. Below 423 K, mainly nitrogen and nitrous oxide were formed and above this temperature, NO was formed. The PEP experiments indicate that all ammonia reacts at the beginning of the catalyst bed, and that [13n]-NH3 is partly converted into gaseous products and partly remains... 

Figure 23 further shows that after changing the flow to NHs/He, [ N]-NH3 desorbs and travels as a pulse through the reactor. This indicates that [13N]-NH3 exchanges rapidly with [ Nj-NHs. At first sight, this exchange process is very similar to the experiment shown in Figure 22. However, in this case, radio-labelled ammonia is not in full equilibrium on 7-almnina. After switching to imlabelled ammonia, first of all, the available Lewis sites are saturated. The time to satmate the 7-alumina bed with ammonia, measured with the mass spectrometer at the outlet of the reactor, is equal to the retention time of radiolabelled ammonia in the catalyst bed. Thus, the radiolabelled ammonia moves with the saturation front, where aimnonia adsorption/desorption is in quasi equilibrium. We conclude that gas phase anunonia clearly facilitates desorption of [ Nj-NHs it remains adsorbed at the same bed position without ammonia in the gas phase. This proves that Adsorption Assisted Desorption takes place for aimnonia desorption from 7-alumina.

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