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Enzymatic synthesis of no-carrier-added 6-[18F]fluoro-l-dopa with β-tyrosinase

Authors
Journal
Applied Radiation and Isotopes
0969-8043
Publisher
Elsevier
Publication Date
Volume
50
Issue
6
Identifiers
DOI: 10.1016/s0969-8043(98)00173-0
Disciplines
  • Biology
  • Chemistry

Abstract

Abstract An enzymatic synthesis of nca 6-[ 18F]fluoro- l-dopa has been developed. The process consists of a chemical synthesis of 4-[ 18F]fluorocatechol and its enzymatic reaction with β-tyrosinase. The 4-[ 18F]fluorocatechol was prepared by nucleophilic aromatic substitution of the NO 2 group on 6-nitroveratoraldehyde with [K/222] +18F −, followed by decarbonylation with tris(triphenylphosphine) rhodium(I) chloride and hydrolysis with hydroiodic acid. By C18 Sep-Pak purification, 4-[ 18F]fluorocatechol was obtained in ethanol with a radiochemical yield of 9.2%. An enzymatic reaction of 4-[ 18F]fluorocatechol, ammonium and pyruvate catalyzed by β-tyrosinase in an ethanolic Tris–HCl buffer (pH 9.0) containing ascorbate gave within 5 min 6-[ 18F]fluoro- l-dopa with an approximate radiochemical yield of 60% without any isomers. The deproteinized reaction mixture was applied to a preparative reverse phase column, and the radiochemically and enantiomerically pure 6-[ 18F]fluoro- l-dopa was obtained with a radiochemical yield of 2.0% based on [ 18F]F − (decay-corrected). The synthesis time was 150 min from the EOB and the specific activity was >200 GBq/μmol.

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