L-Rhamnal was acylated under a variety of conditions with various acylating reagents. Substitution of the hydroxyl group in the allylic position was favored when acetyl chloride, N-acetylimidazole, benzoyl chloride, and N-benzoylimidazole were used (40-60% net yields), whereas the homoallylic group of L-rhamnal was selectively protected when acetic anhydride-pyridine was employed for the acylation. The monoacetates of L-fucal underwent O-3----O-4 migration of the acetyl group, and selective acylation of this glycal could not be achieved.
General Strategy for Stereoselective Synthesis of β-<i>N</i>-Glycosyl Sulfonamides via Palladium-Catalyzed Glycosylation
作者:Yuanwei Dai、Jianfeng Zheng、Qiang Zhang
DOI:10.1021/acs.orglett.8b01506
日期:2018.7.6
A highly efficient and mild glycosylation reaction between 3,4-O-carbonate glycal and N-tosyl functionalized aliphatic and aromatic amines via palladium-catalyzed decarboxylative allylation is disclosed. A wide range of highly functionalized 2,3-unsaturated β-N-glycosides are furnished in good to excellent yields and complete regioselectivity and stereoselectivity. In addition, applications of the
Selective deprotection of esters using magnesium and methanol
作者:Yao-Chang Xu、Elaine Lebeau、Clint Walker
DOI:10.1016/s0040-4039(00)73392-2
日期:1994.8
The use of magnesium metal in methanol for the deprotection of alkyl esters is described. This mild reagent also provides good to excellent selectivity to cleave different esters. The order of the reactivity of this reagent towards acyl cleavages was found to be: p-nitrobenzoate > acetate > benzoate > pivaloate > trifluroacetamide.
concise, diversity‐oriented approach for the synthesis of naturally occurring 3‐amino‐ and 3‐nitro‐2,3,6‐trideoxypyranose derivatives and analogues thereof from simple sugars has been developed. In addition, we investigated the synthesis of various 3‐aminoglycosyl donors and their application in glycosylation reactions. These studies led to the successful synthesis of a tetrasaccharide containing four different
Umpolung Reactivity in the Stereoselective Synthesis of S-Linked 2-Deoxyglycosides
作者:Kedar N. Baryal、Danyang Zhu、Xiaohua Li、Jianglong Zhu
DOI:10.1002/anie.201301682
日期:2013.7.29
Take control! An unprecedented sulfenylation of stereochemically defined 2‐deoxyglycosyl lithium species with asymmetric sugar‐derived disulfide acceptors enabled the stereoselectivesynthesis of both α‐ and β‐S‐linked 2‐deoxyoligosaccharides. Reductive lithiation of 2‐deoxyglycosyl phenylsulfides at −78 °C provides predominantly axial glycosyl lithium species, which upon warming isomerize to predominantly
Chemical synthesis of the <i>Pseudomonas aeruginosa</i> O11 O-antigen trisaccharide based on neighboring electron-donating effect
作者:Chunjun Qin、Zhonghua Liu、Meiru Ding、Juntao Cai、Junjie Fu、Jing Hu、Peter H. Seeberger、Jian Yin
DOI:10.1080/07328303.2020.1839479
日期:2020.10.12
but an exact protective epitope has not yet been identified. Synthesis of O11 O-antigen trisaccharide is of importance for identifying the epitopes. Here, neighboring electron-donating effects are keys to enhance the nucleophilicity of the C3 hydroxyl groups of D- and L-fucosamines, to facilitate the efficient synthesis of the trisaccharide. The disarmed peracetylated glycosyl donor with low glycosylation