Syntheses of 6-fluoro-meta-tyrosine and of its metabolites

6-Fluoro-meta-tyrosine (1) was prepared from 2-fluoro-5-hydroxybenzaldehyde (6) based on an Erlenmeyer–Plöchl azlactone strategy. Products of expected metabolism of the amino acid, including 6-fluoro-meta-tyramine (2) and its O-sulfate conjugate (3), (2-fluoro-5-hydrxoyphenyl)acetic acid (4), and 6-fluoro-meta-octopamine (5) also were prepared from 1. The use of a recently reported ultrasound-catalyzed Henry reaction facilitated the preparation of the tyramine derivative 2. The compounds synthesized are available for high performance liquid chromatography (HPLC) standards in positron emission tomography (PET) studies employing 6-[18F]fluoro-meta-tyrosine and as reference samples for metabolic studies of the amino acid.