TY - JOUR
T1 - A rapid and highly enantioselective C-11C bond formation of l-[11C]phenylalanine via chiral phase-transfer catalysis
AU - Pekošak, Aleksandra
AU - Filp, Ulrike
AU - Škrinjar, Janja
AU - Poot, Alex J.
AU - Windhorst, Albert D.
PY - 2017
Y1 - 2017
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85009834048&partnerID=8YFLogxK
U2 - https://doi.org/10.1039/c6ob02633h
DO - https://doi.org/10.1039/c6ob02633h
M3 - Article
C2 - 27991625
SN - 1477-0520
VL - 15
SP - 570
EP - 575
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
IS - 3
ER -