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Preparation of tritium‐labelled meta ‐aminolevamisole of high specific radioactivity by catalytic dehalogenation
Author(s) -
Lewis James A.,
Paterson Ian
Publication year - 1984
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580211009
Subject(s) - chemistry , tritium , halogenation , potassium hydroxide , specific activity , extraction (chemistry) , radiochemistry , iodine monochloride , catalysis , chromatography , iodine , nuclear chemistry , organic chemistry , enzyme , physics , nuclear physics
Abstract We describe the synthesis of tritiated meta ‐aminolevamisole (MAL) of high specific radioactivity. Unlabelled MAL was iodinated with iodine monochloride in aqueous hydrochloric acid. The major reaction product, L[‐]2,3,5,6‐tetrahydro‐6‐(5‐amino‐2‐iodophenyl)imidazo [2,1‐b]thiazole, was catalytically dehalogenated with carrier‐free tritium gas in methanolic potassium hydroxide over 10% palladium‐carbon. After extraction and chromatography, a radioactive species ([ 3 H]‐MAL) was identified with the same chromatographic mobility as unlabelled MAL, [ 3 H]‐MAL possesses the same high biological activity in contracting nematode muscle as authentic unlabelled MAL, co‐chromatographs with unlabelled MAL in three different TLC systems and is about 90% radiochemically pure. By bioassay and competitive inhibition studies, the specific radioactivity of [ 3 H]‐MAL appears greater than 15 Ci /mmole and is probably close to 29 Ci /mmole. [ 3 H]‐MAL was shown to be useful for detecting a high affinity, saturable binding activity in extracts of the nematode Caenorhabditis elegans .