Development of a reliable remote-controlled synthesis of β-[11C]-5-hydroxy-L-tryptophan on a Zymark robotic system

• Published in: Journal of labelled compounds & radiopharmaceuticals Vol. 49; no. 10; pp. 889 - 895
• Main Authors: Neels, O. C., Jager, P. L., Koopmans, K. P., Eriks, E., de Vries, E. G. E., Kema, I. P., Elsinga, P. H.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-09-2006; Wiley
• Subjects: [11C]-5-HTP; Bioconversions. Hemisynthesis; Biological and medical sciences; Biotechnology; carbon-11; Contrast media. Radiopharmaceuticals; enzyme; Fundamental and applied biological sciences. Psychology; Medical sciences; Methods. Procedures. Technologies; neuroendocrine tumors; Pharmacology. Drug treatments; robot; Enantioselectivity; [11C]-5-HTP; Carbon Isotopes; Pyruvic acid; Lyases; Tryptophanase; robot; Catalase; Carbon 11; carbon-11; Chemical synthesis; Alanine; Automation; Radiolabelling; Enzyme; Transferases; D-Amino-acid oxidase; α-Aminoacid; Carbon-carbon lyases; Peroxidases; Transaminases; Alanine transaminase; Oxidoreductases; Iodomethane; Neuroendocrine tumor; neuroendocrine tumors; Enzymatic reaction
• ISSN: 0362-4803; 1099-1344
• DOI: 10.1002/jlcr.1110

Precise staging of neuroendocrine tumors (NET) using positron emission tomography (PET) tracers visualizing their specific metabolic activity is of interest. Besides [18F]FDOPA, staging NET with carbon‐11 labeled 5‐hydroxytryptophan (5‐HTP) is reported in recent literature. We implemented the multi‐enzymatic synthesis of enantiomerically pure [11C]‐L‐5‐HTP on a Zymark robotic system to compare both tracers in patient studies. [11C]‐5‐HTP can be synthesized in up to 24% radiochemical yields (EOB). Average specific activity is 44 000 GBq/mmol in ca. 50 min from [11C]methyl iodide in radiochemical purities >99 %. The synthesis of 5‐HTP is difficult due to its multi‐enzymatic reaction steps but typical yields can be achieved of ca. 400 MBq. [11C]‐5‐HTP is now reliably used in ongoing studies for staging NET. Copyright © 2006 John Wiley & Sons, Ltd.