374573-40-7Relevant articles and documents
Donor-Reactivity-Controlled Sialylation Reactions
Asressu, Kesatebrhan Haile,Chang, Chun-Wei,Lam, Sarah,Wang, Cheng-Chung
supporting information, p. 4525 - 4530 (2021/08/09)
Although tremendous efforts have been made for the efficient preparation of sialosides, controlling the stereochemical outcome of sialylation reaction still remains one of the most challenging tasks due to the unique chemical structure of sialic acid. We developed a new strategy to statistically analyze the stereoselectivity of sialylation reactions on six types of p-tolyl thiosialosides in NIS/TfOH system using Relative Reactivity Value (RRV) as the indicator. Analysis of the reaction mechanism showed the formation of the relatively stable glycosyl bromide and glycosyl chloride intermediates from halide- and triflate-containing promotors in the absence of an acceptor. We found that the α/β-stereoselectivity, yields, and intermediate changes were associated with their donor reactivity. These findings enable to tailor the most suitable building blocks for stereo-controlled sialylation reactions.
Comparative studies on the O-sialylation with four different α/β-oriented (N-acetyl)-5-N,4-O-carbonyl-protected p-toluenethiosialosides as donors
Zhang, Xiao-Tai,Gu, Zhen-Yuan,Xing, Guo-Wen
, p. 1 - 7 (2014/03/21)
Four types of 5-N,4-O-carbonyl-protected p-toluenethiosialosides were synthesized and their couplings with different acceptors were thoroughly investigated. The results indicate that the sialyl donor structure, the amount of glycosyl acceptor, and the detailed promotion conditions have great influence on the sialylation stereoselectivties and product yields. Under the (p-Tol)2SO/Tf2O activation conditions, the glycosylations with simple alcohols provided declined α-selectivities and higher yields with increasing the amounts of acceptors from 1.1 equiv to 2.0 equiv. However, the outcome of same sialylation was independent of the relative amounts of sugar alcohol acceptors. With NIS/TfOH as promoter, the α-selectivities of the sialylations were significantly improved compared with the cases activated by (p-Tol)2SO/Tf2O. In general, the difference in configuration of N-acetylated sialyl donors (D2 and D4) has little effect on the sialylation yield and stereoselectivity. In contrast, the N-deacetylated α/β sialyl donors (D1 and D3) show complex sialylation profiles with different acceptors.
α-Selective sialylations with N-acetyl-5-N,4-O-oxazolidinone- protected p-toluenethiosialoside
Liang, Fen-Fen,Chen, Li,Xing, Guo-Wen
body text, p. 425 - 428 (2009/08/09)
A novel N-acetyl-5-N,4-O-oxazolidinone-protected p-toluenethiosialoside was readily prepared from sialic acid and p-toluenethiol. It was demonstrated that the p-toluenethiosialoside could be successfully applied to the α-selective sialylations with variou