title: Improved synthesis of beta-CIT and [11C]beta-CIT labeled at nitrogen or oxygen positions.
abstract: The important radiotracer precursor 2 beta-carbomethoxy-3 beta-(4-idophenyl)-tropane (beta-CIT, RTI-55) was made in 52% overall yield from cocaine. Key steps were improved conjugate Grignard addition to anhydroecgonine methyl ester with > 3.5:1 2 beta: 2 alpha-isomer selectivity, and a mild new direct aromatic iodination with I2 and silver triflate in CH2Cl2. The [11C]beta-CIT was labeled at either the N or O positions with [11C]methyl triflate; and efficient reversed-phase HPLC was used to preparatively separate [N-11C]beta-CIT from N-nor-beta-CIT for the first time, and a fast solid-phase extraction (SPE) method was applied to preparatively separate [O-11C]beta-CIT from beta-CIT-acid precursor.
authors.affiliation: Department of Radiology, Indiana University School of Medicine, Indianapolis 46202-5121, USA.
authors.forename: Q H
authors.initials: QH
authors.lastname: Zheng
authors.forename: G K
authors.initials: GK
authors.lastname: Mulholland
mesh_terms: D002250:Carbon Radioisotopes / Q000737:chemistry*; D003042:Cocaine / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D007553:Isotope Labeling / Q000379:methods*; D008698:Mesylates / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis*
chemical_list: D002250:Carbon Radioisotopes; D008698:Mesylates; D019275:Radiopharmaceuticals; C078465:methyl triflate; C069723:2beta-carbomethoxy-3beta-(4-iodophenyl)tropane; D003042:Cocaine; D009584:Nitrogen; D010100:Oxygen