An asymmetric synthesis of L-[3-C-13]phenylalanine and L-[3-C-13]tyrosine from [C-13]carbon monoxide

L-[3-C-13]Phenylalanine and L-[3-C-13]tyrosine were synthesized. [alpha-C-1 3]Benzyl bromides were prepared from [C-13]carbon monoxide via the palladiu m-catalyzed carboalkoxylation of aryl halides. The asymmetric carbon corres ponding to the 2-position in phenylalanine was introduced by the diastereos elective alkylation of Dellaria's oxazinone with [alpha-C-13]benzyl bromide s. Finally, ethanolysis, deprotection, hydrogenolysis and acid hydrolysis o f the resulting alkylated oxazinones gave L-[3-C-13]phenylalanine and L-[3- C-13]tyrosine in high optical purity. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.