Radioiodinated azide and isothiocyanate derivatives of cocaine for irreversible labeling of dopamine transporters: synthesis and covalent binding studies.
Two novel N-substituted-3beta-phenyltropane alkaloids have been labeled with iodine-125 for use as irreversible probes of dopamine transporter (DAT) binding sites. One contains an iodoaryl azide moiety for photolabeling, while the other bears an iodoaryl isothiocyanate for direct conjugation. Both radioligands were prepared in a one-flask procedure by electrophilic radioiodination of the corresponding aniline under no-carrier-added conditions, followed either by diazotization and treatment with sodium azide, or by addition of thiophosgene under basic conditions. Specifically, (-)-N-[4-(3-[(125)I]iodo-4-azidophenyl)butyl]-2beta-carbomethoxy-3beta-(4-chlorophenyl)tropane ([(125)I]MFZ-2-24) and (-)-N-[4-(3-[(125)I]iodo-4-isothiocyanophenyl)butyl]-2beta-carbomethoxy-3beta-(4-chlorophenyl)tropane ([(125)I]MFZ 3-37) were synthesized. Isolation by reversed-phase HPLC and solid-phase extraction gave good average yields of [(125)I]MFZ-2-24 (67%, n = 5) and [(125)I]MFZ-3-37 (45%, n = 3) with high radiochemical purities (96-99%) and specific radioactivities (>2000 mCi/micromol). The utility of the radioligands was demonstrated by their covalent linkage to rat striatal membranes, and immunoprecipitation of a single radiolabeled band at 80 kDa corresponding to the full-length DAT.
Lever
John R
JR
Departments of Radiology, University of Missouri-Columbia, Missouri 65212, USA. leverj@health.missouri.edu
Zou
Mu-Fa
MF
Parnas
M Laura
ML
Duval
Romain A
RA
Wirtz
Sara E
SE
Justice
Joseph B
JB
Vaughan
Roxanne A
RA
Newman
Amy Hauck
AH
D000818:Animals; D001386:Azides / Q000737:chemistry*; D050482:Catecholamine Plasma Membrane Transport Proteins; D002851:Chromatography, High Pressure Liquid; D003042:Cocaine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D007457:Iodine Radioisotopes; D017879:Isothiocyanates / Q000737:chemistry*; D026901:Membrane Transport Proteins / Q000032:analysis* / Q000378:metabolism*; D015394:Molecular Structure; D051381:Rats
D001386:Azides; D050482:Catecholamine Plasma Membrane Transport Proteins; D007457:Iodine Radioisotopes; D017879:Isothiocyanates; D026901:Membrane Transport Proteins; C493212:Slc22a1 protein, rat; C037152:isothiocyanic acid; D003042:Cocaine