14125-75-8Relevant articles and documents
Mechanistic insights into the gold(I)-Catalyzed activation of glycosyl Ortho -Alkynylbenzoates for Glycosidation
Tang, Yu,Li, Jiakun,Zhu, Yugen,Li, Yao,Yu, Biao
supporting information, p. 18396 - 18405 (2014/01/06)
Anomerization, which involves cleavage and formation of the anomeric C-O bond, is of fundamental importance in the carbohydrate chemistry. Herein, the unexpected gold(I)-catalyzed anomerization of glycosyl ortho-alkynylbenzoates has been studied in detail. Especially, crossover experiments in the presence of an exogenous isochromen-4-yl gold(I) complex confirm that the anomerization proceeds via the exocleavage mechanism, involving (surprisingly) the addition of the isochromen-4-yl gold(I) complex onto a sugar oxocarbenium (or dioxolenium) and an elimination of LAu+ from the vinyl gold(I) complex. The inhibitory effect of the exogenous isochromen-4-yl gold(I) complex when in stoichiometric amount on the anomerization has guided us to disclose an isochromen-4-yl gem-gold(I) complex, which is inactive in catalysis but in equilibrium with the monogold(I) complex and the LAu+ catalyst. The proposed key intermediate in the anomerization, a transient glycosyloxypyrylium species, is successfully trapped via a cycloaddition reaction with n-butyl vinyl ether as a dienophile. SN2-like substitution of the initially formed glycosyloxypyrylium intermediate has then been achieved to a large extent via charging with acceptors in an excess amount to lead to the corresponding glycosides in a stereoselective manner.
A method for the syntheses of Enopyranosides
Khan, Khalid M.,Perveen, Shahnaz,Al-Qawasmeh, Raed A.S,Shekhani, Mohammed S.,Shah, Syed T. Ali,Voelter, Wolfgang
experimental part, p. 191 - 196 (2010/04/23)
Sodium hydride (NaH) in hexamethylphosphoric triamide (HMPA) has been introduced as an economical and efficient reagent towards the creation of 1, 2- or 5, 6-enopyranosides from the corresponding halogenated or tosylated pyranosides. NaH/HMPA has several advantages compared to NaH/DMF: elimination products are produced in high yields even from sterically-hindered halides as well as tosylates. 2009 Bentham Science Publishers Ltd.
S-thiazolinyl (STaz) glycosides as versatile building blocks for convergent selective, chemoselective, and orthogonal oligosaccharide synthesis
Pornsuriyasak, Papapida,Demchenko, Alexei V.
, p. 6630 - 6646 (2008/09/17)
In the aim of developing new procedures for efficient oligosaccharide assembly, a range of 5-thiazolinyl (STaz) glycosides have been synthesized. These novel derivatives were evaluated against a variety of reaction conditions and were shown to be capable of being chemoselectively activated in the armed-disarmed fashion. More over, the S-thiazolinyl moiety exhibited a remarkable propensity for selective activation over other common leaving groups. Conversely, a variety of leaving groups could be selectively activated over the STaz moiety, which, in turn, allowed STaz/S-ethyl and STaz/S-phenyl orthogonal approaches. To demonstrate versatility of novel STaz derivatives, a number of oligosaccharide targets have been synthesized in a convergent selective, orthogonal, and chemoselective fashion.