title: Synthesis of no-carrier-added C-11 labeled D- and L-enantiomers of phenylalanine and tyrosine for comparative PET Studies.
abstract: The natural amino acids tyrosine (Tyr) and phenylalanine (Phe) were labeled with carbon-11 via a modified Bucherer-Strecker synthesis. A rapid reaction of the sodium bisulfite adduct of the aldehyde precursor with ammonia provided the precursor for radiosynthesis. [(11)C]Cyanide displacement followed by base hydrolysis afforded the corresponding (11)C-labeled amino acids. The purification and chiral separation were simply achieved by using a combination of solid-phase extraction and chiral HPLC to afford individual enantiomers of each amino acid. The decay corrected radiochemical yields for each of the enantiomers were 12-16% with respect to the [(11)C]cyanide after 40-45 min of radiosynthesis. Radiochemical purity of the products was >97% (typically >99%), enantiomeric excess was >98% with the specific radioactivity 2-3 Ci/micromol at the end of bombardment. Because of its simplicity and wide applicability, the described procedure could be the method of choice to produce [(11)C]amino acids for PET studies.
authors.affiliation: Brookhaven National Laboratory, Chemistry Department, Upton, NY 11973, USA.
authors.forename: Andrei R
authors.initials: AR
authors.lastname: Studenov
authors.forename: Dava E
authors.initials: DE
authors.lastname: Szalda
authors.forename: Yu-Shin
authors.initials: YS
authors.lastname: Ding
mesh_terms: D002250:Carbon Radioisotopes / Q000737:chemistry*; D007553:Isotope Labeling / Q000379:methods; D010649:Phenylalanine / Q000737:chemistry*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis*; D013237:Stereoisomerism; D014055:Tomography, Emission-Computed / Q000379:methods*; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D014443:Tyrosine; D010649:Phenylalanine