61474-61-1Relevant articles and documents
Tris(4-bromophenyl)aminium hexachloroantimonate-mediated glycosylations of selenoglycosides and thioglycosides. Evidence for single electron transfer?
Mehta, Seema,Pinto, B. Mario
, p. 43 - 51 (1998)
Radical cation-initiated glycosylation reactions of phenyl selenoglycosides are described. Glycosylations of phenyl selenoglycosides effected by the single-electron-transfer (SET) reagent, tris(4-bromophenyl)aminium hexachloroantimonate (BAHA), are examined with primary and secondary hydroxyl acceptors. The corresponding reaction of an ethyl thioglycoside with a primary hydroxyl acceptor is also examined. Reactions are performed in the presence of the SET quenching reagent, 1,2,4,5-tetramethoxybenzene, to assess whether BAHA-mediated glycosylation reactions involve SET. These experiments indicate that the reactions are completely quenched in dichloromethane but only partially in acetonitrile. The results provide support for the SET mechanism but an alternative mechanism involving electrophilic activation cannot be discounted. The oxidation potentials of various selenoglycosides are determined by cyclic voltammetry. Copyright (C) 1998 Elsevier Science Ltd.
Stereoselective O-Glycosylations by Pyrylium Salt Organocatalysis**
Nielsen, Michael Martin,Holmstr?m, Thomas,Pedersen, Christian Marcus
supporting information, (2021/12/30)
Despite many years of invention, the field of carbohydrate chemistry remains rather inaccessible to non-specialists, which limits the scientific impact and reach of the discoveries made in the field. Aiming to increase the availability of stereoselective
Leveraging Trifluoromethylated Benzyl Groups toward the Highly 1,2- Cis-Selective Glucosylation of Reactive Alcohols
Njeri, Dancan K.,Ragains, Justin R.,Valenzuela, Erik Alvarez
supporting information, p. 8214 - 8218 (2021/11/13)
Here, we demonstrate that substitution of the benzyl groups of glucosyl imidate donors with trifluoromethyl results in a substantial increase in 1,2-cis-selectivity when activated with TMS-I in the presence of triphenylphosphine oxide. Stereoselectivity is dependent on the number of trifluoromethyl groups (4-trifluoromethylbenzyl vs 3,5-bis-trifluoromethylbenzyl). Particularly encouraging is that we observe high 1,2-cis-selectivity with reactive alcohol acceptors.
A Streamlined Regenerative Glycosylation Reaction: Direct, Acid-Free Activation of Thioglycosides
Escopy, Samira,Singh, Yashapal,Stine, Keith J.,Demchenko, Alexei V.
, p. 354 - 361 (2020/12/02)
Our group has previously reported that 3,3-difluoroxindole (HOFox) is able to mediate glycosylations via intermediacy of OFox imidates. Thioglycoside precursors were first converted into the corresponding glycosyl bromides that were then converted into the OFox imidates in the presence of Ag2O followed by the activation with catalytic Lewis acid in a regenerative fashion. Reported herein is a direct conversion of thioglycosides via the regenerative approach that bypasses the intermediacy of bromides and eliminates the need for heavy-metal-based promoters. The direct regenerative activation of thioglycosides is achieved under neutral reaction conditions using only 1 equiv. NIS and catalytic HOFox without the acidic additives.
