- Strategies to reduce hERG K+ channel blockade. Exploring heteroaromaticity and rigidity in novel pyridine analogues of dofetilide
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Drug-induced blockade of the human ether-a-go-go-related gene K+ channel (hERG) represents one of the major antitarget concerns in pharmaceutical industry. SAR studies of this ion channel have shed light on the structural requirements for hERG
- Carvalho, Jo?o F. S.,Louvel, Julien,Doornbos, Maarten L. J.,Klaasse, Elisabeth,Yu, Zhiyi,Brussee, Johannes,Ijzerman, Adriaan P.
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p. 2828 - 2840
(2013/05/22)
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- Defunctionalized lobeline analogues: Structure-activity of novel ligands for the vesicular monoamine transporter
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(-)-Lobeline (2R,6S,10S; 1a), an antagonist at nicotinic acetylcholine receptors (nAChRs), inhibits the neurochemical and behavioral effects of methamphetamine and inhibits dopamine transporter (DAT) and vesicular monoamine transporter (VMAT2) function. VMAT2 is a target for the development of treatments for methamphetamine abuse. Structural modification of lobeline affords the defunctionalized analogues meso-transdiene (MTD) and lobelane, which have high potency and selectivity for VMAT2. To establish the structure-activity relationships within this novel class of VMAT2 ligands, specific stereochemical forms of MTD, lobelane, and other structurally related analogues have been synthesized. These compounds have been evaluated for inhibition of [3H]nicotine ([3H]NIC) binding (α4β2* nAChR), [3H]methyllycaconitine ([ 3H]MLA) binding (α7* nAChR), and [3H] dihydrotetrabenazine ([3H]DTBZ) binding (VMAT2). Generally, all of these analogues had lower affinities at α4β2* and α7* nAChRs compared to lobeline, thereby increasing selectivity for VMAT2. The following structural modifications resulted in only modest changes in affinity for VMAT2, affording analogues that were less potent than the lead compound, lobelane: (1) altering the stereochemistry at the C-2 and C-6 positions of the piperidino ring, (2) varying unsaturation in the piperidino C-2 and C-6 substituents, (3) introducing unsaturation into the piperidine ring, (4) ring-opening or eliminating the piperidine ring, and (5) removing the piperidino N-methyl group. Furthermore, incorporating a quaternary ammonium group into defunctionalized lobeline molecules in the cis-series resulted in significant loss of affinity for VMAT2, whereas only a modest change in affinity was obtained in the trans-series. The most potent (Ki = 630 nM) and VMAT2-selective compound evaluated was the N-methyl-2,6-cts- bis(naphthaleneethyl)piperidine analogue 28b (1-NAP-lobelane), in which the phenyl groups of lobelane were replaced with 1-naphthyl moieties. Thus, initial structure-activity relationship studies reveal that the most promising structural changes to the lobeline molecule that lead to enhancement of VMAT2 affinity and selectivity are defunctionalization, affording lobelane and MTD, and replacement of the phenyl rings of lobelane with other aromatic moieties that have a π-extended structure.
- Zheng, Guangrong,Dwoskin, Linda P.,Deaciuc, Agripina G.,Norrholm, Seth D.,Crooks, Peter A.
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p. 5551 - 5560
(2007/10/03)
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- PYRIDINES. PARTIE IX - PLURIBENZYLATION DE LA S-COLLIDINE ET DE LA LUTIDINE-2,6
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A literature survey of the polymetalation of 2,6-lutidine 2 shows different results about the site(s) of deprotonation and condensation with various electrophiles.This discrepancy prompts us to examine the polylithiation (PhLi 3 equivalents, Et2O) of s-collidine 1, 2,6-lutidine 2 and more briefly of 2,4-lutidine 3.Polylithiation takes place exclusively at the methyl groups of the same position vs the ring nitrogen : 2- and/or 6-methyl of 1.The previous regioselectivity observed in the case of the monometalation in Et2O is maintained.From 1 and 2, polylithiation gives picolyl anions which lead by reaction with PhCH2Cl, simultaneously to mono-, di-symmetrical, di-non-symmetrical α-derivatives, and tri- and tetra-symmetrical α,α'-compounds; but no product is formed from a benzylic β-anion.In the same way, the deprotonation of 2-methyl-6-(2-phenylethyl) pyridine 17 leads to 2,6-bis (2-phenylethyl) pyridine 19 and 2-methyl-6-dibenzylmethyl pyridine 18, to the exclusion of the β-compound 2-methyl-6-(2,3-diphenylpropyl) pyridine 21.The latter compound is formed in low yield, besides 19 and 18, in the conditions of the Tchitchibabine reaction (NaNH2, toluene).The structure of the benzylated compounds was established mainly from the 1H-nmr data.No product was isolated which would result from the nucleophilic attack of the generated carbanions at the pyridine carbons.
- Compagnon, Paul-Louis,Kimny, Tan,Gasquez, Francoise
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p. 803 - 816
(2007/10/02)
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