Issue 3, 2011

Enantiospecific synthesis of 2-[18F]fluoro-l-phenylalanine and 2-[18F]fluoro-l-tyrosine by isotopic exchange

Abstract

2-[18F]Fluoro-L-phenylalanine and 2-[18F]fluoro-L-tyrosine have been developed as promising radiopharmaceuticals for molecular imaging using positron emission tomography (PET). However, the lack of a convenient radiosynthetic pathway has limited their practical use. In this work a new three-step nucleophilic synthesis of these compounds starting from [18F]fluoride is described. Corresponding precursors (1a and 1b) were 18F-fluorinated by isotopic exchange, followed by the removal of an activating formyl group with Rh(PPh3)3Cl and subsequent hydrolysis of protecting groups in acidic medium. All reactions were carried out using both conventional and microwave heating. Conventional heated reactions yielded the desired products 2-[18F]Fphe and 2-[18F]Ftyr in 43% and 49% whereas radiochemical yields of 34% and 43%, respectively, were obtained when they were heated by microwaves. Under optimized conditions the enantiomeric purity was ≥94% for both radiopharmaceuticals.

Graphical abstract: Enantiospecific synthesis of 2-[18F]fluoro-l-phenylalanine and 2-[18F]fluoro-l-tyrosine by isotopic exchange

Article information

Article type
Paper
Submitted
16 Jul 2010
Accepted
04 Oct 2010
First published
19 Nov 2010

Org. Biomol. Chem., 2011,9, 765-769

Enantiospecific synthesis of 2-[18F]fluoro-L-phenylalanine and 2-[18F]fluoro-L-tyrosine by isotopic exchange

J. Castillo Meleán, J. Ermert and H. H. Coenen, Org. Biomol. Chem., 2011, 9, 765 DOI: 10.1039/C0OB00440E

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