A rapid and highly enantioselective C-11C bond formation of l-[11C]phenylalanine via chiral phase-transfer catalysis

Aleksandra Pekošak*, Ulrike Filp, Janja Škrinjar, Alex J. Poot, Albert D. Windhorst

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

A rapid method for the synthesis of carbon-11 radiolabeled phenylalanine was developed using a chiral phase-transfer catalyst and a sub-nanomolar quantity of [11C]benzyl iodide as a radio-precursor. Based on a reported synthesis of [11C]benzyl iodide, a Schiff base precursor was evaluated for stereoselective [11C]benzylation. Extensive and interactive screening of the precursor, catalyst, base, stirring and temperature was required to achieve high stereoinduction. The result is an efficient 5-step radiolabeling method to reliably synthesize l- or d-[11C]phenylalanine with an excellent enantiomeric excess of >90% and almost quantitative radiochemical conversion of >95% (n > 5). Additionally, a phase-transfer catalyzed alkylation was utilized on the preparative scale using automated platform. The application resulted in high specific activity ranging from 85-135 GBq μmol−1 of the enantiomerically pure [11C]phenylalanine, showing that the process is robust and amenable to broad use in PET.

Original languageEnglish
Pages (from-to)570-575
Number of pages6
JournalOrganic and Biomolecular Chemistry
Volume15
Issue number3
DOIs
Publication statusPublished - 2017

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