The research focuses on the synthesis of novel chiral aryl diphosphite ligands derived from the pyranoside backbones of glucose and galactose. These ligands were applied in copper-catalyzed asymmetric conjugate addition reactions of diethylzinc to cyclic enones, aiming to form new carbon-carbon bonds and chiral compounds with high enantioselectivity. The study investigated the impact of the ligand's stereochemistry on the reaction's enantioselectivity, revealing that it was influenced by the ligand's backbone stereocenters and the binaphthyl phosphite moieties' configuration. The experiments utilized various reactants, including different cyclic enones, Cu(OTf)2 as the copper source, and the newly synthesized ligands. Analyses of the products were conducted using techniques such as gas chromatography-mass spectrometry (GC-MS) and gas chromatography with a Chiraldex A-TA column to determine conversion, yield, and enantiomeric excess. The research also explored the effects of solvent and reaction temperature on enantioselectivity, finding that ethereal solvents and lower temperatures generally yielded better results.
The research focuses on the synthesis and evaluation of fluorescently labeled and internally quenched UDP-Gal probes, which are sugar nucleotide analogs with a fluorescence emitter and a quencher. These probes were designed to assess their recognition and usage by various galactosyltransferases, enzymes crucial for the biosynthesis of mammalian oligosaccharides. The study involved detailed chemical syntheses of the UDP-Gal analogs, utilizing a range of reactants such as uridine, galactose, and phosphorus oxychloride, among others, and employing techniques like palladium-catalyzed coupling, hydrogenation, and ion-exchange chromatography. The experiments aimed to determine the rate of galactose transfer by several galactosyltransferases, including blood group B a-(1!3) galactosyltransferase, a-(1!3) galactosyltransferase, and milk bovine b-(1!4) galactosyltransferase, using the synthesized UDP-Gal analogs as substrates. Analytical methods employed to monitor the reactions and characterize the products included TLC, MALDI TOF mass spectrometry, and NMR spectroscopy. The results demonstrated that the modified UDP-Gal analogs were recognized as weak substrates by the tested galactosyltransferases, with the ability to transfer their galactose unit to the acceptor molecules.
The study presents a detailed account of the synthesis of Plakoside A, a prenylated and immunosuppressive marine galactosphingolipid isolated from the marine sponge Plakortis simplex. The research involves the synthesis of two diastereoisomers of Plakoside A, which are structurally unique glycosphingolipids containing a prenylated D-galactose moiety and cyclopropane-containing alkyl chains. The study utilized a variety of chemicals, including sphingosine, α-hydroxy acids, prenylated sugars, and various reagents for protection and deprotection of functional groups, as well as for the construction of the complex molecular framework. These chemicals served the purpose of constructing the three main building blocks of Plakoside A: the sugar part, the sphingosine part, and the hydroxy acid part. The synthesis involved multiple steps, including enzymatic methods, Wittig reactions, and prenylation, with the ultimate goal of obtaining the target compounds and elucidating their absolute configuration.
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