甘露糖醛酸酯供体的糖基化高度选择性地进行以产生1,2-顺式连接的产物。基于C5-羧酸酯的远程立体定向作用,我们在此提出了这种与直觉相反的选择性的机械原理,已使用没有C5-羧酸酯以外的环取代基的吡喃糖基尿酸酯来证明。据推测,C 5-羧酸酯优选在草碳en中间体中占据轴向位置,从而比4 H 3构象异构体更倾向于形成3 H 4半椅。对3 H 4的亲核攻击半椅中间体以β的形式出现,为1,2-顺式-甘露糖醛酸酯提供了出色的立体选择性。在利用会聚的正交糖基化策略构建甘露糖醛酸海藻酸酯五聚体中,已经利用了甘露糖酸酯供体在形成β-甘露糖苷键中的潜力。
Synthetic preparation and immunological evaluation of β-mannosylceramide and related <i>N</i>-acyl analogues
作者:Sage A. Robinson、Jessica Yau、Masaki Terabe、Jay A. Berzofsky、Gavin F. Painter、Benjamin J. Compton、David S. Larsen
DOI:10.1039/d0ob00223b
日期:——
The synthesis of the invariant natural killer (iNK) T cell agonist β-mannosylceramide along with a series of fatty amide analogues is reported. Of the six β-glycosylation protocols investigated, the sulfoxide methodology developed by Crich and co-workers proved to be the most effective where the reaction of a mannosyl sulfoxide and phytosphingosine derivative gave a key glycolipid intermediate as a
Studies Related to Norway Spruce Galactoglucomannans: Chemical Synthesis, Conformation Analysis, NMR Spectroscopic Characterization, and Molecular Recognition of Model Compounds
作者:Filip S. Ekholm、Ana Ardá、Patrik Eklund、Sabine André、Hans-Joachim Gabius、Jesús Jiménez-Barbero、Reko Leino
DOI:10.1002/chem.201200510
日期:2012.11.5
and medical industries, attempts to synthesize and study distinct fragments of this polysaccharide have not been reported previously. Herein, the synthesis of one of the core trisaccharide units of GGM together with a less‐abundant tetrasaccharide fragment is described. In addition, detailed NMR spectroscopic characterization of the modelcompounds, comparison of the spectral data with natural GGM,
The methylsulfonylethoxymethyl (Msem) as a hydroxyl protecting group in oligosaccharide synthesis
作者:Asghar Ali、Richard J.B.H.N. van den Berg、Herman S. Overkleeft、Gijsbert A. van der Marel、Jeroen D.C. Codée
DOI:10.1016/j.tet.2010.06.007
日期:2010.8
The methylsulfonylethoxymethyl (Msem) is introduced as a base-labile, non-participating protecting group in carbohydrate chemistry. Conditions to introduce the Msem on primary and secondary alcohols are described. Removal of the Msem is best achieved using a catalytic amount of tetrabutylammonium fluoride (TBAF), with or without a nucleophilic scavenger. Applicability of the Msem group is illustrated in the assembly of an all 1,3-cis-linked mannotrioside. (c) 2010 Elsevier Ltd. All rights reserved.