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Towards stereoselective radiosynthesis of α-[11C]methylsubtituted aromatic α-amino acids ? a challenge of creation of quaternary asymmetric centre in a very short time.
Authors: Popkov Alexandr | Nádvorník Milan | Kružberská Pavla | Lyčka Antonín | Lehel Szabolcs | Gillings Nicholas
Year: 2007
Type of publication: článek v odborném periodiku
Name of source: Journal of Labelled Compounds and Radiopharmaceuticals
Publisher name: John Wiley & Sons Ltd.
Place: Chichester
Page from-to: 370-374
Titles:
Language Name Abstract Keywords
cze Towards stereoselective radiosynthesis of α-[11C]methylsubtituted aromatic α-amino acids ? a challenge of creation of quaternary asymmetric centre in a very short time. In positron emission tomography (PET) a-methyl amino acids have two potential applications: As analogues of neutransmitter precursors for the study of neurodegenerative diseases, and as non-metabolised analogues of proteinogenic amino acids for the study of amino acid uptake into normal and cancer cells. Clinical applications of such amino acids are strongly limited due to their poor availability. We carried out [11C]methylation of metalocomplex synthons derived from protected DOPA or tyrosine. For [11C]methylation, sodium hydroxide (5mg of fine dry powder) was sealed in a vial, which was flushed with dry nitrogen before addition of a solution of the complex (10 mg) and 11CH3I in 1,3-dimethylimidazolidin-2-one (300 ml). After 10 min at 258C, a 9% radiochemical yield (decay-corrected) of a mixture of the diastereomeric a-[11C]methylDOPA complexes or a 7% radiochemical yield of a mixture of the diastereomeric a-[11C]methyltyrosine complexes was achieved. Individual diastereomers were successfully separated by preparative HPLC, diluted with excess of water and extracted on C18 cartridges. Optimisation of the procedure including hydrolysis of the complexes (hydrolytic deprotection of enantiomerically pure amino acids) and subsequent purification of the enantiomers of a-[11C]methylDOPA and a-[11C]methyltyrosine is underway.
eng Towards stereoselective radiosynthesis of α-[11C]methylsubtituted aromatic α-amino acids ? a challenge of creation of quaternary asymmetric centre in a very short time. In positron emission tomography (PET) a-methyl amino acids have two potential applications: As analogues of neutransmitter precursors for the study of neurodegenerative diseases, and as non-metabolised analogues of proteinogenic amino acids for the study of amino acid uptake into normal and cancer cells. Clinical applications of such amino acids are strongly limited due to their poor availability. We carried out [11C]methylation of metalocomplex synthons derived from protected DOPA or tyrosine. For [11C]methylation, sodium hydroxide (5mg of fine dry powder) was sealed in a vial, which was flushed with dry nitrogen before addition of a solution of the complex (10 mg) and 11CH3I in 1,3-dimethylimidazolidin-2-one (300 ml). After 10 min at 258C, a 9% radiochemical yield (decay-corrected) of a mixture of the diastereomeric a-[11C]methylDOPA complexes or a 7% radiochemical yield of a mixture of the diastereomeric a-[11C]methyltyrosine complexes was achieved. Individual diastereomers were successfully separated by preparative HPLC, diluted with excess of water and extracted on C18 cartridges. Optimisation of the procedure including hydrolysis of the complexes (hydrolytic deprotection of enantiomerically pure amino acids) and subsequent purification of the enantiomers of a-[11C]methylDOPA and a-[11C]methyltyrosine is underway. asymetris synthesis; a-methyl amino acids; carbon-11; [11C]methylation; DOPA; tyrosine; nickel; complexes

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