A new method of synthesis of phenyl glycine labelled with deuterium and tritium was elaborated. Labelled phenyl glycine was obtained by isotope exchange method between phenyl glycine and deuterated or tritiated water at elevated temperature in hydrochloric acid medium using K2PtCl4 as a catalyst. 37 GBq /1 Ci/ HTO was used for the synthesis of tritiated phenyl glycine and labelled product with specific activity of 185 MBq/mole /5 mCi/mole/ was obtained.
The kinetic behavior of deuteriation of nitrobenzoic acids has been studied at 130 °C in the presence of homogenous platinum salt catalyst in a medium containing deuteriated acetic acid in heavy water. The quasiunimolecular H/D exchange rate constants for particular position of aromatic ring hydrogens were determined by proton NMR integration signal. The difference in the kinetics patterns of H/D exchange has been shown for the 2-nitro-, 3-nitro- and 4-nitrobenzoic acid.
The isotope exchange between substituted /p-OH, p-CH3O, p-C2H5O, H, p-NO2/ phenylalanines and deuterated water in the presence of K2PtCl4 as a catalyst was studied. It was found that isotope exchange is centered in the aromatic ring, in the methoxy and methyl groups. Electron donating groups accelerate the reaction and electron with-drawing groups retard it.
K2PtCl4 was found to be an efficient and very useful homogenous catalyst for deuterium and tritium exchange of the aromatic hydrogens of phenylalanines and phenylglycine. The exchange reactions of the aromatic ring hydrogens, observed in the 80–130°C temperature interval proceed according to an electrophilic substitution mechanisms. The investigated hydrogen exchange processes involve the reversible formation of -complexes with the aromatic ring, analogous to -complexes postulated in deuterium exchange studies with alkylbenzenes. The probable mechanisms of the platinum(II) catalyzed homogeneous deuterium and tritium exchange of aromatic ring hydrogens and of the methoxy and ethoxy para-substituents are discussed.
The synthesis of two isotopomers of L-DOPA, the precursors for labeled dopamine is reported. The ring labeled with deuterium
or tritium [2′,5′,6-2H3]-L-DOPA, and [2′,5′,6-3H3]-L-DOPA were obtained using acid catalyzed isotopic exchange between L-DOPA and heavy or tritiated water, respectively. Their
derivatives, i.e., [2′,5′,6-2H3], and [2′,5′,6-3H3]-dopamine were obtained by enzymatic decarboxylation of deuterated or tritiated isotopomers of L-DOPA using enzyme tyrosine
decarboxylase (EC 22.214.171.124).
The enzymatic synthesis of three isotopomers of l-DOPA labeled with deuterium and tritium at α carbon atom was elaborated. These compounds were converted into [(1S)-2H]–, [(1S)-3H]–, and doubly labeled [(1S)-2H/3H]-dopamines using enzyme tyrosine decarboxylase. Doubly labeled (1R) isotopologue, i.e., [(1R)-2H/3H]-dopamine, was afforded by enzymatic decarboxylation of authentic l-DOPA carried out in deuteriated and tritiated incubation medium.
One step method for deuteriation of methoxybenzoic acids in the presence of homogeneous divalent platinum salt in medium containing solution of deuteriated acetic acid in heavy water has been elaborated. The quasiunimolecular H/D exchange rate constants at 130 °C for particular position of proton of aromatic ring have been determined by 1H NMR integration signals. The difference of the kinetics patterns of H/D exchange has been shown for the 2-methoxy-, 3-methoxy- and 4-methoxybenzoic acid.
A one-step method has been elaborated for the deuteriation of hydroxybenzoic acids in the presence of homogeneous divalent platinum salt in a medium containing solution of deuteriated acetic acid in heavy water. The quasiunimolecular H/D exchange rate constants have been determined at 130 °C for the particular position of proton on the aromatic ring by 1H NMR integration signals. Different kinetic patterns of H/D exchange are shown for 2-hydroxy-, 3-hydroxy-, and 4-hydroxybenzoic acid.
The kinetics of deuteration of 4-methylbenzoic acid in the presence of a homogenous K2PtCl4 in a medium containing 50% solution of deuteriated acetic acid in heavy water has been studied at 130°C. The quasiunimolecular H/D rate constants for the methyl group, the ortho and meta aromatic ring hydrogens were determined by NMR.
The kinetics of deuteriation of phenylacetic acid with D2O acidified with DCl in the presence of homogeneous K2PtCl4 catalyst has been investigated in the 100–130°C temperature interval. The quasiunimolecular H/D rate constants at 100 and 130°C corresponding exchange processes in -position in side chain and para position of the substituted benzene ring were determined by NMR integration signal. The same constants for ortho and meta positions have been deduced by analysis of the composite NMR signal, and the Arrhenius activation energies for the exchange reactions were estimated.