title: An improved method for the synthesis of radiolabeled McN5652 via thioester precursors.
abstract: An improved procedure that facilitates routine production and increases the radiochemical yield of [11C]McN5652 (trans-1,2,3,5,6,10b-hexahydro-6-[4-([11C]methylthio)-phenyl]pyrrolo- [2,1-alpha]-isoquinoline) is presented. Specifically, thiol acetate, butyrate, and benzoate derivatives of McN5652 were prepared as the precursors for the [11C]McN5652 synthesis. These thioesters offer greater stability than the previously used thiol precursor (desmethyl McN5652) and enable a single batch of material to be used for multiple radiolabelings. Hydrolysis of the thioester functionality (tetrabutylammonium hydroxide, 10 min) unmasked the free thiol which, without purification, was reacted with [11C]iodomethane in DMF at 40-45 degrees C for 1 min. The average decay-corrected radiochemical yield for [11C]McN5652 was 26% with an average specific activity of 2290 mCi/mumol (end of synthesis). This facile radiolabeling method, utilizing the butyrate thioester of McN5652, was also employed in the preparation of [3H](+)- and (-)McN5652 [trans-1,2,3,5,6S (or 6R),10bR, (or 10bS)-hexahydro-6-[4-([3H]methylthio)phenyl]pyrrolo-[2,1,alpha]- isoquinoline] from [3H]iodomethane.
authors.affiliation: Division of Nuclear Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21205-2179, USA.
authors.forename: M
authors.initials: M
authors.lastname: Suehiro
authors.forename: J L
authors.initials: JL
authors.lastname: Musachio
authors.forename: R F
authors.initials: RF
authors.lastname: Dannals
authors.forename: W B
authors.initials: WB
authors.lastname: Mathews
authors.forename: H T
authors.initials: HT
authors.lastname: Ravert
authors.forename: U
authors.initials: U
authors.lastname: Scheffel
authors.forename: H N
authors.initials: HN
authors.lastname: Wagner
mesh_terms: D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D007202:Indicators and Reagents; D007546:Isoquinolines; D007553:Isotope Labeling / Q000379:methods; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D012702:Serotonin Antagonists; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D007202:Indicators and Reagents; D007546:Isoquinolines; D012702:Serotonin Antagonists; D014316:Tritium; C058079:McN 5652