Biomedical subjects
Publications and source records attributed to Jotham W Coe.
[Structure: see text] The development of a concise enantioselective synthesis of nicotinic alkaloid 1 is presented. The route features the synthesis and use of a "stable" aliphatic triflate 21 in an alkylation step to generate Heck precursor 24 and an enantioselective cyclization to establish a compound with the key [3.2.1]-bicyclic core, 29.
3,5-Bicyclic aryl piperidines are a new class of high-affinity alpha4beta2 nicotinic receptor agents. We have sought nicotinic receptor partial agonists of the alpha4beta2 nicotinic acetylcholine receptor for smoking cessation, and a number of compounds fulfill potency, selectivity, and efficacy requirements in vitro. In vivo, selected agents demonstrate potent partial agonist efficacy on the mesolimbic dopamine system, a key measure of therapeutic potential for smoking cessation.
The metabolism and disposition of varenicline (7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine), a partial agonist of the nicotinic acetylcholine receptor for the treatment of tobacco addiction, was examined in rats, mice, monkeys, and humans after oral administration of [14C]varenicline. In the circulation of all species, the majority of drug-related material was composed of unchanged varenicline. In all four species, drug-related material was primarily excreted in the urine. A large percentage was excreted as unchanged parent drug (90, 84, 75, and 81% of the dose in mouse, rat, monkey, and human, respectively). Metabolites observed in excreta arose via N-carbamoyl glucuronidation and oxidation. These metabolites were also observed in the circulation, in addition to metabolites that arose via N-formylation and formation of a novel hexose conjugate. Experiments were conducted using in vitro systems to gain an understanding of the enzymes involved in the formation of the N-carbamoylglucuronide metabolite in humans. N-Carbamoyl glucuronidation was catalyzed by UGT2B7 in human liver microsomes when incubations were conducted under a CO2 atmosphere. The straightforward dispositional profile of varenicline should simplify its use in the clinic as an aid in smoking cessation.
The preparation and biological activity of analogs of (-)-cytisine, an alpha4beta2 nicotinic receptor partial agonist, are discussed. All-carbon-containing phenyl ring replacements of the pyridone ring system, generated via Heck cyclization protocols, exhibited weaker affinity and lower efficacy partial agonist profiles relative to (-)-cytisine. In vivo, selected compounds exhibit lower efficacy partial agonist profiles than that of (-)-cytisine.
Herein we describe a novel series of compounds from which varenicline (1, 6,7,8,9-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine) has been identified for smoking cessation. Neuronal nicotinic acetylcholine receptors (nAChRs) mediate the dependence-producing effects of nicotine. We have pursued alpha4beta2 nicotinic receptor partial agonists to inhibit dopaminergic activation produced by smoking while simultaneously providing relief from the craving and withdrawal syndrome that accompanies cessation attempts. Varenicline displays high alpha4beta2 nAChR affinity and the desired in vivo dopaminergic profile.
The key elimination step for the formation of 3-chloro- and 3-fluorobenzyne from 2-chloro-6-fluorophenyllithium displays a pronounced solvent-dependent regioselectivity. 6Li and 13C NMR spectroscopic studies on 2-chloro-6-fluorophenyllithium reveal a single monomeric aryllithium, suggested by DFT computational studies to be a trisolvate. Rate studies indicate that the elimination of LiCl and LiF proceeds via trisolvated and disolvated monomers, respectively.
Noncoordinating solvents permit the halogen-metal exchange-induced formation of benzyne (aryne) from di- and trihalobenzene precursors in the presence of cyclopentadiene to give 1,4-dihydro-1,4-methano-naphthalenes. Studies with mixed halide precursors and nonacidic Diels-Alder diene traps reveal that ethereal and hydrocarbon solvents influence the halide leaving group facility, resulting in a reversal of 3-halobenzyne regioselectivity.
Oxidative ring closure of alkyl-substituted 2-hydroxyacetophenone trifluoromethanesulfonate esters (triflates) occurs upon exposure to base in anaerobic DMF at 20-90 degrees C. Alkyl substitution is required for ring closure. A migrated enol triflate product forms at lower temperature in high yield via migration of the trifluoromethanesulfonate in the unsubstituted and monoalkyl-substituted cases. The alkyl-substituted enol triflates also enter into the benzofuran-3-one ring-forming process under thermal cyclization conditions. Potential mechanistic pathways are evaluated.
A synthesis of 4,5-benzo-1-aza-tricyclo[4.3.1.1(3,8)]undecane (1), a benzo-1-aza-adamantane derivative, is described and features a previously unknown application of the Wolff-Kishner reduction of a nonresonance stabilized or "twisted" amide. An intermediate amino ester is converted to a severely "twisted amide", which, when exposed to hydrazine in alcohol, provides the corresponding "twisted" amino hydrazone. Wolff-Kishner conditions (KOH/ethylene glycol, 200 degrees C) provide the reduced target 1 without hydrolysis to amino acid derivatives. These operations are conveniently performed in a single flask in high yield.