Tryptophan and its metabolites are involved in different physiological and pathophysiological processes. Consequently, positron emission tomography (PET) tracers addressing tryptophan metabolic pathways should allow the detection of different pathologies like neurological disorders and cancer. Herein we report an efficient method for the preparation of fluorotryptophans labeled in different positions with F and their biological evaluation. 4-7-[F]Fluorotryptophans ([F]FTrps) were prepared according to a modified protocol of alcohol-enhanced Cu-mediated radiofluorination in 30-53% radiochemical yields. In vitro experiments demonstrated high cellular uptake of 4-7-[F]FTrps in different tumor cell lines. 4, 5-, and 6-[F]FTrps, although stable in vitro, suffered from rapid in vivo defluorination. In contrast, 7-[F]FTrp demonstrated a high in vivo stability and enabled a clear delineation of serotonergic areas and melatonin-producing pineal gland in rat brains. Moreover 7-[F]FTrp accumulated in different tumor xenografts in a chick embryo CAM model. Thus, 7-[F]FTrp represents a highly promising PET probe for imaging of Trp metabolism.

18F‐Labeled aromatic amino acids exhibit great potential for diagnostic applications using positron emission tomography. However, the introduction of 18F into aromatic compounds remains challenging, and novel fluorination methods facilitating easy access to 18F‐labeled arenes are highly sought after. In recent years, novel metal‐mediated fluorination methods have been reported and transferred into radiochemistry. Based on Cu‐mediated radiofluorination, a two‐step synthesis of no‐carrier‐added (n.c.a.) 6‐[18F]fluoro‐l‐tryptophan was developed. 6‐[18F]Fluoro‐l‐tryptophan was synthesized with an overall radochemical yield of 16 ± 4% within 110 min and a specific activity of 280 GBq µmol–1. The radiochemical purity was more than 99 %. The developed method allowed access to radiofluorinated tryptophan derivatives in high radiochemical yields and opens new ways to provide radiofluorinated amino acids. Furthermore, the reaction conditions were optimized to facilitate automation.

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Short Notes K25 phys. stat. s o l . 10, K25 (1965) Physikalisches I n s t i t u t der Karl-Max-Universitst, Leipeig, Abteilung Technische Physik Diffusionsnachwirkung an Mn-Zn-Perriten i n f o h e momentaner h d e r u n g des inneren Spannungszustandes Von D. SCH&?ER, H.-Ch.

Die Reaktion von Monazit mit Kohlenstoff und Quarz wurde bei Temperaturen zwischen 1400°C und 1700°C untersucht. Es bilden sich neben elementarem Phosphor die Silikate der Seltenen Erden und des Thoriums. Diese lassen sich mit Salzsäure extrahieren.