Kdo glycosides

Deoxv-D-manno-2-octulosonic acid (KDO) has been linked with the following sugars allyl KDO glycoside (4-linkage, a- and 6-anomers), D-glucosamine 4-phosphate(6-a-linkage), and... 

The synthesis of glycosylating agents for the preparation of a- and /3-linked KDO glycosides is referred to in Chapter 16. 

A similar approach was used by Sinay (Scheme 6) for a new synthesis of Kdo glycosides and disaccharides [8]. The mannose derived hydroxyheptenitol 30 was converted into the exo-enol ether 31 through a multistep synthesis. Cyclization was achieved using potassium t-butoxide and iodine at low temperature to give the dis-accharidic derivative 32 as the only product of the reaction. The transformation of the iodomethyl appendage into the carboxylic group required a difficult nucleo-... 

Paul Kosma contribution describes the latest findings in Kdo glycosidation, a demanding research area for the development of glycoarrays, immunoreagents and vaccines that can be accessed by reading Chapter 4. 

This chapter reports selected relevant contributions to Kdo glycoside chemistry with an emphasis on progress in stereoselectivity, yield and suppression of the elimination side reaction, it mainly covers examples from the past decade. 

Donor 53 was first evaluated in a test reaction with 2-propanol in the presence of BFg EtaO as promoter, which gave the a-glycoside 54 in 83% yield with a low amount of elimination product 4 (5%). Removal of the 3-iodo-group was accomplished under hydrogen atom transfer conditions to furnish the Kdo glycoside 55 (Scheme 10). The method vras further extended to include the azido spacer derivative 56 and the dehalogenated spacer derivative 57 in similar yields. 

Scheme 33 Synthesis of p-Kdo glycosides from a 1-C-aryl glycal derivative.Adapted with permission from Y. Qian, J. Feng, M. Parvez and C.-C. Ling, J. Org. Chem., 2012, 77, 96-107. Copyright (2012) American Chemical Society.

Dha and Kdo being destroyed under the acidic conditions used to cleave glycosidic linkages [11] their methyl ethers could not be analyzed in this study. 

RG-n, Rhamnogalacturonan II Kdo, 3-deoxy-D-manno-octulosonic acid Dha, 3-deoxy-D-/yxo-heptulosaric acid aceric acid, 3-C- carboxy-5-deoxy-L-xylose TMS, per-0-trimethylsilylated methyl glycosides. 

Scheme 8. Scope of samarium chemistryf in the synthesis of UC -glycosides of KDO. Where Rl and R2 are H, alkyl or saccharide moieties.

It was rationalized that the KDO C-glycoside is generated only in the a-configuration because the a-face of the samarium enolate intermediate 38 is much less sterically hindered than P-face (Scheme 9b). 

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