title: Syntheses of 11C- and 18F-labeled carboxylic esters within a hydrodynamically-driven micro-reactor.
abstract: Carboxylic esters were successfully labeled with one of two short-lived positron-emitters, carbon-11 or fluorine-18, within a hydrodynamically-driven micro-reactor. The non-radioactive methyl ester was obtained at room temperature; its yield increased with higher substrate concentration and with reduced infusion rate. Radioactive methyl ester was obtained from the reaction of (10 mM) with in 56% decay-corrected radiochemical yield (RCY) at an infusion rate of 10 microL min(-1), and when the infusion rate was reduced to 1 microL min(-1), the RCY increased to 88%. The synthesis of the non-radioactive fluoroethyl ester from and required heating of the micro-reactor on a heating block at 80 degrees C (14-17% RCY), whilst the corresponding radioactive from and was obtained in 10% RCY. The radioactive 'peripheral' benzodiazepine receptor ligand was obtained from the reaction of acid with labeling agent in 45% RCY at an infusion rate of 10 microL min(-1). When the infusion rate was reduced to 1 microL min(-1), the RCY increased to 65%. The results exemplify a new methodology for producing radiotracers for imaging with positron emission tomography that has many potential advantages, including a requirement for small quantities of substrates, enhanced reaction, rapid reaction optimisation and easy product purification.
authors.affiliation: PET Radiopharmaceutical Sciences, Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-1003, USA. Shuiyu.Lu@mail.nih.gov
authors.forename: Shui-Yu
authors.initials: SY
authors.lastname: Lu
authors.forename: Paul
authors.initials: P
authors.lastname: Watts
authors.forename: Frederick T
authors.initials: FT
authors.lastname: Chin
authors.forename: Jinsoo
authors.initials: J
authors.lastname: Hong
authors.forename: John L
authors.initials: JL
authors.lastname: Musachio
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Briard
authors.forename: Victor W
authors.initials: VW
authors.lastname: Pike
mesh_terms: D002245:Carbon Dioxide; D002250:Carbon Radioisotopes / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D004952:Esters; D005462:Fluorine Radioisotopes / Q000737:chemistry*; D007553:Isotope Labeling / Q000379:methods*; D008832:Microchemistry / Q000295:instrumentation / Q000379:methods; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D008904:Miniaturization; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis*
chemical_list: D002250:Carbon Radioisotopes; D002264:Carboxylic Acids; D004952:Esters; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D002245:Carbon Dioxide; C041069:carboxyl radical