604-70-6Relevant articles and documents
1,2-Acyloxyl Migration in Pyranosyl Radicals
Korth, Hans-Gert,Sustmann, Reiner,Groeninger, Kay Stefan,Leisung, Michael,Giese, Bernd
, p. 4364 - 4369 (1988)
Tetra-O-acetylgalactosyl radical (5) and tetra-O-acetylglucosyl radical (10) undergo a 1,2-migration of acetoxyl groups to the corresponding 2-deoxytetra-O-acetylpyranosan-2-yl radicals.The activation parameters for the rearrangement of tetra-O-acetylgalactosyl radical, as determined by ESR spectroscopy, are ΔH(excit.) = 12.2 +/- 0.3 kcal/mol and ΔS(excit.) = -6.7 +/- 1.0 eu.Labeling studies with 18 O support a five-membered cyclic transition state for the rearrangement with exchange of the oxygen atoms of the carboxy group.The driving force for the rearrangement, which is unfavorable in terms of the stability of the radical centers, derives from the gain in anomeric stabilization of the product radical.
Pachymoside A - A novel glycolipid isolated from the marine sponge Pachymatisma johnstonia
Warabi, Kaoru,Zimmerman, William T.,Shen, Jingkai,Gauthier, Annick,Robertson, Marilyn,Finlay, B. Brett,Van Soest, Rob,Andersen, Raymond J.
, p. 102 - 112 (2004)
Crude extracts of the North Sea marine sponge Pachymatisma johnstonia showed promising activity in a new assay for inhibitors of bacterial type III secretion. Bioassay-guided fractionation resulted in the isolation of the pachymosides, a new family of sponge glycolipids. A major part of the structural diversity in this family of glycolipids involves increasing degrees of acetylation and differing positions of acetylation on a common pachymoside glycolipid template. All of the metabolites with these variations in acetylation pattern were converted into the same peracetylpachymoside methyl ester (2) for purification and spectroscopic analysis. Pachymoside A (1) is the component of the mixture that has natural acetylation at the eight galactose hydroxyls and at the C-6 hydroxyls of glucose-B and glucose-D. Chemical degradation and transformation in conjunction with extensive analysis of 800 MHz NMR data was used to elucidate the structure of pachymoside A (1).
General Strategy for the Synthesis of Rare Sugars via Ru(II)-Catalyzed and Boron-Mediated Selective Epimerization of 1,2- trans-Diols to 1,2- cis-Diols
Li, Xiaolei,Tang, Weiping,Wu, Jicheng
, p. 3727 - 3736 (2022/03/02)
Human glycans are primarily composed of nine common sugar building blocks. On the other hand, several hundred monosaccharides have been discovered in bacteria and most of them are not readily available. The ability to access these rare sugars and the corresponding glycoconjugates can facilitate the studies of various fundamentally important biological processes in bacteria, including interactions between microbiota and the human host. Many rare sugars also exist in a variety of natural products and pharmaceutical reagents with significant biological activities. Although several methods have been developed for the synthesis of rare monosaccharides, most of them involve lengthy steps. Herein, we report an efficient and general strategy that can provide access to rare sugars from commercially available common monosaccharides via a one-step Ru(II)-catalyzed and boron-mediated selective epimerization of 1,2-trans-diols to 1,2-cis-diols. The formation of boronate esters drives the equilibrium toward 1,2-cis-diol products, which can be immediately used for further selective functionalization and glycosylation. The utility of this strategy was demonstrated by the efficient construction of glycoside skeletons in natural products or bioactive compounds.
Direct dehydrative glycosylation catalyzed by diphenylammonium triflate
Hsu, Mei-Yuan,Lam, Sarah,Lin, Mei-Huei,Lin, Su-Ching,Wang, Cheng-Chung,Wu, Chia-Hui
supporting information, (2020/03/13)
Methods for direct dehydrative glycosylations of carbohydrate hemiacetals catalyzed by diphenylammonium triflate under microwave irradiation are described. Both armed and disarmed glycosyl-C1-hemiacetal donors were efficiently glycosylated in moderate to excellent yields without the need for any drying agents and stoichiometric additives. This method has been successfully applied to a solid-phase glycosylation.
Phosphotungstic acid as a novel acidic catalyst for carbohydrate protection and glycosylation
Chen, Jyun-Siao,Sankar, Arumugam,Lin, Yi-Jyun,Huang, Po-Hsun,Liao, Chih-Hsiang,Wu, Shen-Shen,Wu, Hsin-Ru,Luo, Shun-Yuan
, p. 33853 - 33862 (2019/11/11)
This work demonstrates the utilization of phosphotungstic acid (PTA) as a novel acidic catalyst for carbohydrate reactions, such as per-O-acetylation, regioselective O-4,6 benzylidene acetal formation, regioselective O-4 ring-opening, and glycosylation. These reactions are basic and salient during the synthesis of carbohydrate-based bioactive oligomers. Phosphotungstic acid's high acidity and eco-friendly character make it a tempting alternative to corrosive homogeneous acids. The various homogenous acid catalysts were replaced by the phosphotungstic acid solely for different carbohydrate reactions. It can be widely used as a catalyst for organic reactions as it is thermally stable and easy to handle. In our work, the reactions are operated smoothly under ambient conditions; the temperature varies from 0 °C to room temperature. Good to excellent yields were obtained in all four kinds of reactions.
