Refernces
10.1016/S0040-4020(97)00377-3
The study presents an enantioselective synthetic route to trans-2,6-disubstituted piperidines, focusing on the synthesis of (S)-2-methyl tetrahydropyridine-N-oxide, a key intermediate. This compound is crucial for constructing trans-2,6-disubstituted piperidines via a [3+2] nitrone cycloaddition reaction. The research demonstrates the utility of this method by synthesizing the fire ant venom alkaloid, (+)-solenopsin-A, through a series of steps including nitrone formation, cycloaddition, and reductive cleavage. The methodology is highlighted for its potential application in synthesizing similar piperidine-based alkaloids, with implications for pharmaceuticals, such as treatments for Alzheimer's disease.
10.1021/jo802371z
The research focuses on the dual stereoselectivity in the dialkylzinc reaction using (-)-α-pinene derived amino alcohol chiral auxiliaries. The study involves the synthesis of two regioisomeric amino alcohols, 3-MAP and 2-MAP, from (+)-nopinone, which is prepared from naturally occurring (-)-α-pinene. These amino alcohols serve as chiral auxiliaries in the addition of diethylzinc to benzaldehyde, yielding secondary alcohols with high enantiomeric excess (ee). The experiments utilize various reactants, including (+)-nopinone, lithium aluminum hydride, and diethylzinc, and employ techniques such as X-ray crystallography, two-dimensional NMR, and NOE correlations for characterization and confirmation of stereochemistry. The research also explores the use of these amino alcohols in the dimethylzinc addition reaction and provides mechanistic insights into the observed dual stereoselectivity. The analyses include chiral gas chromatography to determine the enantiomeric excess and optical rotation to assign the absolute configuration of the products.
10.1055/s-0031-1289746
The research focuses on a divergent synthetic strategy based on the regioselective reductive ring-opening of a cyclic 1,2-p-methoxybenzylidene acetal. The study employs a common intermediate, (1S)-N,N-dibenzyl-1-[(4R)-2-(4-methoxyphenyl)-1,3-dioxolan-4-yl]ethanamine, synthesized in five steps from an α-bromo-α'-(R)-sulfinyl ketone, to produce p-methoxybenzyl-protected primary and secondary alcohols. These alcohols serve as precursors for the synthesis of a fully protected syn-3-amino-2-hydroxybutanoic acid and an N-benzyl 2-hydroxymethylaziridine. Key reactants include α-bromo-α'-(R)-sulfinyl ketones, diisobutylaluminum hydride, p-anisaldehyde, and various other reagents used in the synthesis and purification processes. The research involves a series of chemical reactions, such as Pummerer rearrangement, reduction with lithium aluminum hydride, and reductive cleavage using diisobutylaluminum hydride. Analytical techniques used to characterize the compounds include NMR spectroscopy, high-resolution mass spectrometry (HRMS), and optical rotation measurements. The experiments demonstrate a regioselective approach to synthesize the desired alcohols and further transform them into the target molecules, showcasing the synthetic potential of the methodology for creating biologically important molecules.
10.1021/jo00126a079
The research focuses on the development of a simplified six-step synthesis method for supercryptands, which are spherical macrotricyclic ligands known for their exceptional complexing abilities, particularly with alkali metal cations like rubidium and cesium, as well as ammonium cations and organic molecules. The study aimed to improve upon the previously lengthy and complex synthesis process, making supercryptands more accessible for further study of their complexing properties. The chemicals used in this process include p-toluenesulfonamide, diamino ethers, sodium or potassium carbonate (Na2CO3 or K2CO3), lithium aluminum hydride (LiAlH4), and various diiodo compounds. The synthesis involved the formation of ditosyl-substituted cryptands, removal of tosyl protecting groups, and subsequent cyclization to form supercryptands with yields of 30-40%. The conclusions of the research indicate that this new synthetic route is efficient and provides a practical means to prepare supercryptands for more in-depth studies of their complexing properties.
10.1007/s10600-007-0065-6
The research focuses on the synthesis of N-methyl urocanates of hydroxy derivatives of isocembrol, which are proposed biomimetics of taxol and exhibit cytotoxic activity similar to eleutherobin and sarcodictyins. The experiments involved stereospecific hydroxylation of isocembrol to prepare alcohols, which were then esterified into N-methylurocanates. Key reactants included isocembrol, t-butylhydroperoxide (TBHP), VO(acac)2, LiAlH4, (i-Bu)2AlH, SeO2, and N-methylurocanic acid, among others. The analyses used to characterize the products and intermediates were primarily nuclear magnetic resonance (NMR) spectroscopy, including both proton (PMR) and carbon (13C NMR) variants, as well as thin-layer chromatography (TLC), optical rotation measurements, and melting point determinations. These techniques were crucial in establishing the regio- and stereochemistry of the synthesized compounds.
10.1016/S0040-4039(00)87637-6
The research aimed to investigate the stereochemistry of the reduction of gem-dibromo and monobromocyclopropanes using lithium aluminum hydride (LAH), sodium bis(2-methoxyethoxy)aluminum hydride (SMEAH), and tributyltin hydride (TBTH). The purpose was to understand the reaction mechanisms and intermediates involved in these reductions, particularly focusing on the role of cyclopropyl radicals. The study concluded that the reductions proceed through configurationally equilibrated cyclopropyl radicals as intermediates, with LAH and TBTH reductions showing similar results, while SMEAH reductions suggested an anion mechanism. The research also provided evidence for the nature of the product-forming step in these reductions and tested for deuterium incorporation through the work-up media, which supported the proposed mechanisms. The chemicals used in the process included the cyclopropanes themselves, LAH, SMEAH, TBTH, and various solvents and reagents for the reduction and work-up steps.
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