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The short-lived radionuclide 11C (t1/2 = 20.4 min) has been used in the asymmetric synthesis of L-2-amino[3-11C]butyric acid, L-[3-11C]-norvaline and L-[3-11C]valine. The syntheses were performed by alkylation of [(+)-2-hydroxypinanyl-3-idene]-glycine tert-butyl ester under anhydrous conditions in tetrahydrofuran/1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone with lithiated 2,2,6,6-tetramethylpiperidine as base, using the appropriate 11C-alkyl iodides prepared in a one-pot reactor from [11C]carbon dioxide. Following removal of the protecting groups, the -[3-11C]amino acids were obtained in 80-82% enantiomeric excess and in 9-25% radiochemical yields, decay corrected and calculated on the basis of the amount of [11C]carbon dioxide at the start of the syntheses within 50-55 min.

acta chemica scandinavica/acta chemica scandinavica. b, organic chemistry and biochemistry/acta chemica scandinavica. a, physical and inorganic chemistry/acta chemica scandinavica. series b. organic chemistry and biochemistry/acta chemica scandinavica. series a, physical and inorganic chemistry

Asymmetric Synthesis of L-2-Amino[3-11C]butyric Acid, L-[3-11C]Norvaline and L-[3-11C]Valine.