Untitled

Synthesis of tritium labeled isotopomers of L‐tyrosine

“…The tritium label was introduced into the methylene group of malonic acid, 3, as a result of isotope exchange between malonic acid and tritiated water at elevated temperature. 21 Knovenagel condensation of [2][3] H]malonic acid, 3, with benzaldehyde leads to [2][3] H]cinnamic acid, 22 4, which in turn was converted 23 by the enzyme PAL (Phenylalanine ammonia lyase, EC 4.3.5.1) to [2-3 H]-l-Phe. Finally, as shown in Figure 2, tritiated l-Phe The hydroxylation of l-Phe to l-Tyr was carried out in the presence of a cofactor and the enzyme catalase that protects l-Tyr from hydrogen peroxide formed during incubation.…”

Untitled

“…Passing strange! More accurate half-lives for some electron-capture isotopes have been reported 197 [ 7 Be t 1/2 53.42 d, 54 Mn t 1/2 312.6 d, 83 Rb t 1/2 , 86.2 d, 84 Rb t 1/2 33.1 d] and holmium-166m [t 1/2 1200 yr] has been proposed 198 as a suitable source for the standardisation of gamma ray spectrometers because it emits a large number of gamma rays throughout the range 89-1400 keV. A novel use for neptunium has been proposed, 199 as an electrode in a redox flow battery.…”

“…Thus the label in [ 14 C]glinkgolide A 79 was introduced via [ 14 C]methyl propionate, into a cyclic tetrapeptide 80 from 1-[ 14 C]benzoyl chloride, into fadrozole 81 from potassium [ 14 C]cyanide and into an insulin derivative NN304 82 by the use of 1-[ 14 C]myristic acid. The labelling of erucic acid 83 was effected by Wittig coupling with a [ 14 C]nonyl aldehyde but the preparation of [ 14 C]benzaldehyde, 84 required for the synthesis of 3-[ 14 C]cinnamic acid, was most easily done by enzymatic oxidation of 1-[ 14 C]benzyl alcohol.…”

Synthesis of carbon‐14 labeled [1‐14C]‐, and [2‐14C]‐L‐tyrosine

“…To avoid this loss we applied enzymes in the key steps of the synthetic 14 C]-l-phenylalanine, l-Phe, in the presence of the enzyme PAL. [29][30][31][32] In the next step labeled l-Phe was oxidized to l-Tyr using an enzyme l-phenylalanine hydroxylase (EC 1.14.16.1 -lphenylalanine 4 0 -monooxygenase) from rat liver. 16 To stimulate the hydroxylation of l-Phe to l-Tyr the reaction was carried out in the presence of d,l-6-methyl-5,6,7,8-tetrahydropterine (cofactor) and 0 -monooxygenase (EC.…”