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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
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 .