Structural features of azidopyridinyl neonicotinoid probes conferring high affinity and selectivity for mammalian alpha4beta2 and Drosophila nicotinic receptors.

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Zhang N, Tomizawa M, Casida JE

Structural features of azidopyridinyl neonicotinoid probes conferring high affinity and selectivity for mammalian alpha4beta2 and Drosophila nicotinic receptors.

J Med Chem. 2002 Jun 20;45(13):2832-40.

PubMed ID

12061885 [ View in PubMed

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Abstract

The higher toxicity of neonicotinoid insecticides such as N-(6-chloropyridin-3-ylmethyl)-2-nitroiminoimidazolidine (imidacloprid) to insects than mammals is due in large part to target site specificity at the corresponding nicotinic acetylcholine receptors (nAChRs). We propose that neonicotinoids with a protonated N-unsubstituted imine or equivalent substituent recognize the anionic subsite of the mammalian alpha4beta2 nAChR whereas the negatively charged (delta(-)) tip of the neonicotinoid insecticides interacts with a putative cationic subsite of the insect nAChR. This hypothesis can be tested by using two photoaffinity probes that differ only in the N-unsubstituted imine vs negatively charged (delta(-)) tip. Synthesis methodology was developed for compounds combining three moieties: pyridin-3-ylmethyl or 6-chloropyridin-3-ylmethyl and their 4- and 5-azido analogues; imidazolidine, 4-imidazoline or 4-thiazoline; and N-unsubstituted imine, nitroimine, cyanoimine, or nitromethylene. Structure-activity studies compared displacement of [(3)H]nicotine binding in mammalian alpha4beta2 nAChR and [(3)H]imidacloprid binding in Drosophila nAChR. Preferred compounds are N-(5-azido-6-chloropyridin-3-ylmethyl) with 2-iminothiazoline for alpha4beta2 (K(i) = 0.47 nM) and with 2-nitroiminothiazoline or 2-nitromethyleneimidazolidine for Drosophila (K(i) = 0.72-3.9 nM).

DrugBank Data that Cites this Article

Binding Properties

Drug	Target	Property	Measurement	pH	Temperature (°C)
Nicotine	Neuronal acetylcholine receptor subunit beta-2	Ki (nM)	2	N/A	N/A	Details