Enzymatic synthesis of dopamine ring labeled with hydrogen isotopes

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 4.1.1.25). (author)