Glycolipids scheme

To investigate the possibihty of ordered molecular assemblies forming in ionic liquids, the solubilities of glycolipids. Schemes 11.3 and 11.4, were tested. L-Glutamate derivatives 4 (n= 12, 16) were employed because they are insoluble in water, even at a concentration of 1 mM. It was found that these water-insoluble... 

V-hydroxyglycine ethyl ester affords nitrones in good yields (187). Several a-aryl-iV-methylnitrones have been produced in yields of 80% to 100% without solvents, in the presence of 3A molecular sieves (188). Using 4A molecular sieves, it was possible to carry out the synthesis of novel glycolipidic nitrones — potential antioxidant dmgs for neurodegenerative disorders (Scheme 2.22) (189). 

The multibranched dodeca-arabinosaccharide 174 (Scheme 5.38) is a relevant part of the of LAM glycolipid of M. tuberculosis, illustrated in Figure 5.2. The structure features a repeated 3,5-branched motif, represented by the encircled units, along with linear catenated arabino-1 —> 5 units. Lu and Fraser-Reid proposed two retro-synthetic plans (based on dissections A and B, Scheme 5.38), which employ as the sole source NPOE 175 [102,103]. In option A, a nona-arabinan donor would be delivered to the primary hydroxy] of a tri-arabinan acceptor, whereas in option B two identical tetra-arabinan donors would be delivered to the tetra-arabino acceptor. 

For this purpose, Ag zeolite and Ag, developed by Garegg25 and Paulsen,26 respectively, have been widely employed (Scheme 7.6). Reactions using these activators have found practical use in synthetic studies on glycoprotein glycans and glycolipids. For instance, Paulsen reported the chemical synthesis of the core pentasaccharide structure 6 common to all types of Asn-linked glycans, using the Ag... 

About 10-20% of all transmembrane proteins that are targeted to the ER and subsequently enter the secretory pathway are subject to post-translational modification with glycosylphosphatidyl-inositol (GPI). Proteins bearing the GPI anchor are involved in signal transduction, immune response, cancer cell invasion, and metastasis and the pathobiology of trypanosomal parasites. The structure of the GPI anchor has been analyzed for mammals, protozoa, and yeast. The general structure of the glycolipid structure is shown in Scheme 4. 

Scheme 1 Separation procedure for the cytokine-inducing glycolipids.

SCHEME 3.9 Synthesis of the a-glycolipid 14 using a glycosyl iodide. DIPEA, diisopro-pylethylamine PMB, p-methoxybenzyl. 

Mimetics of sialyl Lewis X, the terminal tetrasaccharide of glycoproteins and glycolipids that are known to interact with selectins in the inflammatory process, have been efficiently synthesized through the use of the enzymatic aldol condensation (Scheme 5.26).29 This straightforward approach involved the condensation of mannosyl aldehyde derivatives with DHAP in the presence of DHAP-dependent aldolases. The aldehyde acceptors are generated from mannose by protection of the anomeric center as allyl ether, followed by... 

Glycosylphosphatidyl inositol anchors constitute a class of glycolipids that link proteins and glycoproteins via their C-terminus to eukaryotic cell membranes. The first structure of a GPI anchor, that of Trypanosoma brucei, was published by Ferguson et al. [262]. Since then quite a few examples of GPI anchors were described, allowing the definition of the core structure depicted inO Scheme 37 [263]. 

---