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Articles 1 - 5 of 5
Full-Text Articles in Chemistry
Convenient Synthesis Of 1,3-Dithiolane-2-Thiones: Cyclic Trithiocarbonates As Conformational Locks, Irina A. Dotsenko, Qinliang Zhao, Andreas H. Franz, Patrick Batoon, Nataliya M. Samoshina, Vyacheslav V. Samoshin
Convenient Synthesis Of 1,3-Dithiolane-2-Thiones: Cyclic Trithiocarbonates As Conformational Locks, Irina A. Dotsenko, Qinliang Zhao, Andreas H. Franz, Patrick Batoon, Nataliya M. Samoshina, Vyacheslav V. Samoshin
Andreas H. Franz
A series of novel 1,3-dithiolane-2-thiones, or cyclic trithiocarbonates, has been prepared by a new simple procedure: a treatment of the corresponding epoxides with the commercially available potassium ethyl xanthogenate, KSC(S)OEt. The stereochemistry of the products was determined by 1 H NMR and in some cases by single-crystal X-ray data. Cyclohexane-based 1,3- dithiolane-2-thiones revealed a trans-fusion of the carbo- and hetero-cycles. The products obtained from the mono-substituted cyclohexene oxides demonstrated an axial position of the substituents. Thus the epoxide transformation into trithiocarbonate can be used as a method for locking cyclic compounds in unstable conformations.
Synthesis And Nmr-Characterization Of Three Quinamide-Based Disaccharide Mimetics With Unusual Cyclohexane Twist-Conformation, Thuy Trang M. Nguyen, Paul H. Gross, Andreas H. Franz
Synthesis And Nmr-Characterization Of Three Quinamide-Based Disaccharide Mimetics With Unusual Cyclohexane Twist-Conformation, Thuy Trang M. Nguyen, Paul H. Gross, Andreas H. Franz
Andreas H. Franz
The synthesis of amide-linked disaccharide mimetics has been explored starting with carbohydrate-based amines and a protected quinic acid lactone. Benzyl-2-amino-4,6-Obenzylidene-2-deoxy-α/β-D-glucopyranose (12) and D-glucamine (14) were successfully coupled to give the corresponding quinamides (13 and 15), while the quinoylation of Oacetylated L-fucopyranosyl methylamine (7) failed. The latter was prepared from per-O-acetylL-fucopyranose via the improved multigram scale synthesis of the corresponding per-O-acetylL-fucopyranosyl cyanide (3). Compound 3 was subsequently hydrogenated to yield a mixture of compound 7 and the per-O-acetylated bis-(fucopyranosylmethyl) amine (5). The vicinal coupling constants in the NMR spectra of all quinamide products revealed considerable flexibility of the cyclohexane ring in …
Structure Assignment And H/D-Exchange Behavior Of Several Glycosylated Polyphenols, Andreas H. Franz, Ilona Serebnitskaya, Gurbir Gudial, Christopher Wallis
Structure Assignment And H/D-Exchange Behavior Of Several Glycosylated Polyphenols, Andreas H. Franz, Ilona Serebnitskaya, Gurbir Gudial, Christopher Wallis
Andreas H. Franz
The NMR-structures of six polyphenols, resveratrol (1), (-)-epicatechin (2), pelargonidin chloride (3), cyanidin chloride (4), cyanin chloride (5), and keracyanin chloride (6), were fully assigned. For the glycosylated polyphenols 5 and 6, the three-dimensional solution structure and long-range 1 H- 13C-coupling constants across the glycosidic bond were measured. Satisfactory fit to standard Karplus-equations was achieved for glycosides directly attached to the aromatic core in cyanin chloride. Molecular dynamics simulation data in vacuum at the AM1-level of theory were shown to approximate the NMR-solution data reasonably well. Selective HCl-catalyzed H/D-exchange was observed for aromatic protons H6 and H8 in flavonoid structures …
Syntheses Of Small Cluster Oligosaccharide Mimetics, Andreas H. Franz, Paul H. Gross, Vyacheslav V. Samoshin
Syntheses Of Small Cluster Oligosaccharide Mimetics, Andreas H. Franz, Paul H. Gross, Vyacheslav V. Samoshin
Andreas H. Franz
We designed multiple Small Cluster Oligosaccharide Mimetics (SCOMs) - potential glycosidase inhibitors - to be metabolically stable and small enough to enter cells or bacteria. Therefore, minimal scaffolds (urea, amide, ammonia) or simply non-glycosidic linkages of carbohydrate structures were central to our synthetic strategy, including: (a) coupling of several natural carbohydrate precursors; (b) total syntheses of aminomethyl tetrahydropyrans and their chiral amides with quinic acid; (c) glycopyranosyl cyanide reduction to prepare crowded clusters on a urea scaffold; (d) total syntheses via cycloadditions leading to amide-linked C-glycosides; (e) reduction of nitromethyl C-glycosides; and (f) a synthesis of hydroxylated 1,2- cyclohexanedicarboxylic acids.
Solution Conformations Of Three Small Cluster Oligosaccharide Mimetics (Scom) From D-Glucosamine, D-Altrosamine, And (-)-Quinic Acid, Q. L. Nguyen, L. Olmstead, S. Bains, Andreas H. Franz
Solution Conformations Of Three Small Cluster Oligosaccharide Mimetics (Scom) From D-Glucosamine, D-Altrosamine, And (-)-Quinic Acid, Q. L. Nguyen, L. Olmstead, S. Bains, Andreas H. Franz
Andreas H. Franz
Three small cluster oligosaccharide mimetics were synthesized, and their CDCl3 solution conformations were determined with NMR experiments. In this paper, we confirmed conformational similarities in rings A and B in all three compounds, and we provide the overall solution geometries. In all cases, an unusual cyclohexane twist-boat conformation with longrange 4 J-(W)-coupling was observed. The origin of the bias towards the twist-boat was attributed primarily to the fused ring system between the cyclohexane ring and the dioxacyclopentane (acetal) including hydrogen bonding. Temperature-annealed molecular dynamics simulations complemented the NMR experiments and supported the overall assignment.