1219934-97-0Relevant academic research and scientific papers
Mechanistic insights into the gold(I)-Catalyzed activation of glycosyl Ortho -Alkynylbenzoates for Glycosidation
Tang, Yu,Li, Jiakun,Zhu, Yugen,Li, Yao,Yu, Biao
, 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.
Gold(I)-Catalyzed glycosylation with glycosyl ortho-alkynylbenzoates as donors: General scope and application in the synthesis of a cyclic triterpene saponin
Li, Yao,Yang, Xiaoyu,Liu, Yunpeng,Zhu, Cunsheng,Yang, You,Yu, Biao
supporting information; experimental part, p. 1871 - 1882 (2010/06/20)
Glycosyl ortho-alkynylbenzoates have emerged as a new generation of donors for glycosidation under the catalysis of gold(I) complexes such as Ph 3PAuOTf and Ph3PAuNTf2 (Tf= trifluoromethanesulfonate). A wide variety of these donors, including 2-deoxy sugar and sialyl donors, are easily prepared and shelf stable. The glycosidic coupling yields with alcohols are gener-ally excellent; even direct coupling with the poorly nucleophilic amides gives satisfactory yields. Moreover, excellent α-selective glycosylation with a 2-deoxy sugar donor and β-selective sialylation have been realized. Application of the present glycosylation protocol in the efficient synthesis of a cyclic triterpene tetrasaccharide have further demonstrated the versatility and efficacy of this new method, in that a novel chemoselective glycosylation of the carboxylic acid and a new one-pot sequential glycosylation sequence have been implemented.
Total synthesis and structural revision of TMG-chitotriomycin, a specific inhibitor of insect and fungal β-N-acetylglucosaminidases
Yang, You,Li, Yao,Yu, Biao
supporting information; experimental part, p. 12076 - 12077 (2010/01/30)
(Chemical Equation Presented) TMG-chitotriomycin, a potent and selective inhibitor of the β-N-acetylglucosaminidases that possesses an unique N,N,N-trimethyl-D-glucosamine (TMG) residue, is revised to be the TMG-β-(1→4)-chitotriose instead of the original
