TY - JOUR
AU1 - Gee, Antony D.
AU2 - Långström, Bengt
AB - The synthesis of α-([C]methyl)tyrosine  and α-([C]methyl)phenylalanine  from dimethyl 2-(4-methoxybenzyl)-2-([C] methyl)malonate  and dimethyl 2-benzyl-2-([C] methyl)malonate , respectively is reported. After the alkylation of dimethyl 2-(4-methoxybenzyl)malonate or dimethyl 2-benzylmalonate with [C]methyl iodide, a selective enzymatic hydrolysis to monomethyl 2-(4-methoxybenzyl)-2-([C]methyl) malonic acid  or monomethyl 2-benzy-2-([C]methyl)malonic acid  was carried out using pig liver esterase (EC 3.1.1.1). Conversion of the carboxylic acid moiety of  into the corresponding isocyanate  was achieved by a modified Curtius rearrangement using diphenylphosphoryl azide (DPPA). The simultaneous hydrolysis of the isocyanate and ester moieties of  using conc. hydrochloric acid produced the desired amino acids . In the case of α-([C]methyl)tyrosine, the methyl ether protecting group was removed using trimethylsilyl chloride-sodium iodide prior to acidic hydrolysis. The amino acids were obtained in 12–20% decay corrected radiochemical yields in a synthesis time of 45–50 min, counted from the start of [C] methyl iodide synthesis, and with a radiochemical purity greater than 98% after preparative HPLC purification. Enantiomeric purities of  were determined by the HPLC separation of the respective. 1-fluoro-5-(2,4-dinitrophenyl)--alanine amide (FDAA) diastereoisomers, which showed an enantiomeric excess of 62% for  but no observable enantiomeric induction for . To confirm the position of labelling, a C synthesis was carried out using (C)methyl iodide in the same reaction sequence, and the product analysed by C NMR spectroscopy.
TI - The synthesis of α-([11C]methyl)phenylalanine and α-([11C]methyl)tyrosine from 11C-labelled malonic esters
JF - Journal of the Chemical Society, Perkin Transactions 1
DO - 10.1039/p19910000215
DA - 1991-01-01
UR - https://www.deepdyve.com/lp/royal-society-of-chemistry/the-synthesis-of-11c-methyl-phenylalanine-and-11c-methyl-tyrosine-from-lJxv1vXg88
SP - 215
EP - 218
VL - 
IS - 1
DP - DeepDyve
ER -