New analogues of epiboxidine incorporating the 4,5-dihydroisoxazole nucleus: synthesis, binding affinity at neuronal nicotinic acetylcholine receptors, and molecular modeling investigations

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Clelia Dallanoce, Pietro Magrone, Paola Bazza, Giovanni Grazioso, Luca Rizzi, Loredana Riganti, Cecilia Gotti, Francesco Clementi, Karla Andrea Frydenvang, Marco De Amici

A group of novel 4,5-dihydro-3-methylisoxazolyl derivatives, structurally related to epiboxidine (=(1R,4S,6S)-6-(3-methylisoxazol-5-yl)-7-azabicyclo[2.2.1]heptane), was prepared via 1,3-dipolar cycloaddition of acetonitrile oxide to different olefins. Target compounds 1a and 1b, 2a and 2b, 3, 4, and 5 were tested for affinity at neuronal nicotinic heteromeric (alpha4beta2) and homomeric (alpha7) acetylcholine receptors. Notably, diastereoisomers 1a and 1b were characterized by a massive drop of the affinity at the alpha4beta2 subtypes (K(i) values spanning the range 4.3-126 microM), when compared with that of epiboxidine (K(i)=0.6 nM). Therefore, the replacement of the 3-methylisoxazole ring of epiboxidine with the 4,5-dihydro-3-methylisoxazole nucleus is detrimental for the affinity at alpha4beta2 receptors. A comparable lack of affinity/selectivity for the two nAChR subtypes under study was evidenced for the remaining epiboxidine-related dihydroisoxazole derivatives 2a and 2b, and 3-5. Diastereoisomers 1a and 1b, and spirocyclic derivative 3 were docked into molecular models of the receptor subtypes under study, and their binding mode was compared with that of reference ligands endowed with high binding affinity.
Original languageEnglish
JournalChemistry & Biodiversity
Volume6
Issue number2
Pages (from-to)244-259
ISSN1612-1872
DOIs
Publication statusPublished - 2009

ID: 11172887