Stereospecific Synthesis of 1,2-cis Glycosides by Vinyl-Mediated IAD
摘要:
(GRAPHICS)Stereospecific 1,2-cis glycosylation of 2-O-vinyl thioglycosides, synthesized from the corresponding alcohols by Ir-catalyzed transvinylation with vinyl acetate, is achieved by iodine-mediated tethering of a range of primary and secondary carbohydrate acceptors, followed by intramolecular aglycon delivery (IAD). The use of such an intramolecular glycosylation strategy furnishes the desired alpha-gluco and beta-manno disaccharides in an entirely stereoselective manner.
2-<i>O</i>-<i>N</i>-Benzylcarbamoyl as a Protecting Group To Promote β-Selective Glycosylation and Its Applications in the Stereoselective Synthesis of Oligosaccharides
This study examines the utility of the N-benzylcarbamoyl (BnCar) protecting group in glycosylation reactions of the parent O-2 protected carbohydratedonor. It was found that the BnCar group imparted exclusively β-selectivity with primary and secondary alcohols. A mechanistic study revealed the activated intermediate to be the glycosyl triflate in a skew conformation, which results in β-selective glycosylation
这项研究研究了N-苄氨基甲酰基(BnCar)保护基在亲本O -2保护的碳水化合物供体的糖基化反应中的作用。发现BnCar基团仅赋予伯醇和仲醇β-选择性。一项机理研究表明,活化的中间体为偏构型的三氟甲磺酸糖基酯,可通过类似S N 2的途径导致β选择性糖基化。BnCar基团可以使用亚硝酸四丁铵容易地裂解,而不会影响酯和醚保护基。综上所述,这些结果表明BnCar可用于合成复杂的低聚糖,这项工作需要对各种保护基进行精细的化学区分。
Total Synthesis of a Glycoglycerolipid from<i>Meiothermus taiwanensis</i>through a One-Pot Glycosylation Reaction and Exploration of its Immunological Properties
作者:Bhaswati Ghosh、Yen-Hsun Lai、Yu-Yin Shih、Tapan Kumar Pradhan、Chun-Hung Lin、Kwok-Kong Tony Mong
DOI:10.1002/asia.201300933
日期:2013.12
The totalsynthesis of a glycoglycerolipid isolate of Meiothermus taiwanensis and its truncated structural analogues is reported. Our synthesis employed DMF‐modulated and low‐concentration glycosylationreactions for the construction of α‐ and β‐glycosidic bonds in the absence of participating protecting groups. Further simplification of the synthesis was achieved by employing a low‐concentration one‐pot
Iterative α-Glycosylation Strategy for 2-Deoxy- and 2,6-Dideoxysugars: Application to the One-Pot Synthesis of Deoxysugar-Containing Oligosaccharides
作者:Jiun-Han Chen、Jyh-Herng Ruei、Kwok-Kong Tony Mong
DOI:10.1002/ejoc.201400006
日期:2014.3
This paper describes the development of an iterative and α-selective glycosylation method for 2-deoxyglycosyl and 2,6-dideoxythioglycoside donors based on the DMF modulation concept. We used NMR spectroscopy to probe the 2-deoxyglycosyl imidinium intermediate and elucidated the conditions to decrease the formation of glycal and thus to increase the reaction yields. Further elaboration of the glycosylation
Neighboring-Group Participation by C-2 Ether Functions in Glycosylations Directed by Nitrile Solvents
作者:Chin-Sheng Chao、Ching-Yu Lin、Shaheen Mulani、Wei-Cheng Hung、Kwok-kong Tony Mong
DOI:10.1002/chem.201100732
日期:2011.10.17
Ether‐protecting functions at C‐2 hydroxy groups have been found to play participating roles in glycosylations when the reactions are conducted in nitrile solvent mixtures. The participation mechanism is based on intramolecular interaction between the lone electron pair of the oxygen atom of the C‐2 ether function and the nitrile molecule when they are positioned in a cis configuration. A 1,2‐cis glycosyl
Iterative One-Pot α-Glycosylation Strategy: Application to Oligosaccharide Synthesis
作者:Chih-Yueh Ivan Liu、Shaheen Mulani、Kwok-Kong Tony Mong
DOI:10.1002/adsc.201200396
日期:2012.11.26
three iterativeone-potα-glycosylation methods, i.e., one-pot (α,α)-, one-pot (β,α)-, and one-pot (α,β)-glycosylations, were developed. These methods are applicable to a range of thioglycosyl donors, confer stereocontrol in α-/β-glycosidic bond formation, and thus provide for rapid access to oligosaccharides with various permutations of anomeric configurations. The utility of these one-pot glycosylation