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[6‐chloro‐3‐pyridylmethyl‐ 3 H] neonicotinoids as high‐affinity radioligands for the nicotinic acetylcholine receptor: Preparation using NaB 3 H 4 and LiB 3 H 4
Author(s) -
Latli Bachir,
Than Chit,
Morimoto Hiromi,
Williams Philip G.,
Casida John E.
Publication year - 1996
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/(sici)1099-1344(199611)38:11<971::aid-jlcr923>3.0.co;2-u
Subject(s) - chemistry , ethylenediamine , medicinal chemistry , methanol , ethanol , metabolite , tetrahydrofuran , nuclear chemistry , stereochemistry , organic chemistry , biochemistry , solvent
NaB 3 H 4 and LiB 3 H 4 at 78% and 97% isotopic enrichments, respectively, were used in the synthesis of 3 H‐labeled 1‐(6‐chloro‐3‐pyridyl)‐methyl‐2‐nitromethyleneimidazolidine (CH‐IMI) and N ′‐[(6‐chloro‐3‐pyridyl)methyl]‐ N ″‐cyano‐ N ′‐methylacetamidine (acetamiprid) (two very potent insecticides) and of 1‐(6‐chloro‐3‐pyridyl)methyl‐2‐iminoimidazolidine (desnitro‐IMI) (a metabolite of the commercial insecticide imidacloprid). 6‐Chloronicotinoyl chloride was treated with either NaB 3 H 4 in methanol or LiB 3 H 4 in tetrahydrofuran and the resulting alcohol transformed to 2‐chloro‐5‐chloromethylpyridine, which was then coupled to N ‐cyano‐ N ′‐methylacetamidine to give [ 3 H]acetamiprid (45 Ci/mmol). 2‐Chloro‐5‐chloro[ 3 H]methylpyridine was also reacted with ethylenediamine and the product was either refluxed in absolute ethanol with 1,1‐bis(methylthio)‐2‐nitro‐ethylene to provide [ 3 H]CH‐IMI or reacted in toluene with a solution of cyanogen bromide to produce [ 3 H]desnitro‐IMI (each 55 Ci/mmol).