Chemical Synthesis of Glycosides of N-Acetylneuraminic Acid

Conformationally Constrained Glycosyl Donors as Tools to Control Glycosylation Outcomes

“…The stereoselective glycosylation of sialic acids is extremely challenging due to the lack of a C -3 group to direct glycosylation and the presence of a destabilizing electron-withdrawing group attached to the anomeric center, which often results in 2,3-elimination and poor selectivity . In 2006, the De Meo group reported the synthesis of α-selective neuraminic acid thioglycoside 79 , bearing an O -4, N -5-oxazolidinone protecting group (Scheme a) .…”

“…The stereoselective glycosylation of sialic acids is extremely challenging due to the lack of a C-3 group 74 to direct glycosylation and the presence of a destabilizing electronwithdrawing group attached to the anomeric center, which often results in 2,3-elimination and poor selectivity. 75 oxazolidinone protecting group (Scheme 15a). 76 This bicyclic donor showed higher α-selectivity than monocyclic donors 80 and 81.…”

Exhaustive Conformational Search for Sialyl Cation Reveals Possibility of Remote Participation of Acyl Groups

“…Such structure makes sialic acids the key participants in carbohydrate-protein interactions, [1,2] supporting a wide range of biological processes [3] ranging from cell mobility and adhesion, recognition by viruses [4] and bacteria to immune response [5,6] and oncogenesis. [7] In synthetic chemistry sialic acids are attached to other carbohydrates by means of a glycosylation reaction called sialylation [8][9][10][11][12] (Scheme 1). Understanding the sialylation reaction mechanism at large is a profound scientific task, required to gain the control over the reaction outcome and, hence, to obtain the desired anomer (usually, α-anomer, which is ubiquitously present in living organisms).…”

Diversity-Oriented Chemoenzymatic Synthesis of Sulfated and Nonsulfated Core 2 O-GalNAc Glycans

“…Given the difficulties in obtaining homogeneous glycans isolated from natural sources in high purity and sufficient quantity, chemical or chemoenzymatic approaches have been developed for the preparation of core 2 O- GalNAc glycans. Although elegant chemical methods for the synthesis of core 2 O- GalNAc glycans have been reported, − these approaches could only provide one compound at the time or small numbers of related compounds, and stereoselective formation of the sialic acid linkage is a critical challenge in carbohydrate chemistry. − Alternatively, a chemoenzymatic strategy has been employed to an efficient assembly of mono- or disialyl core 2 O- GalNAc glycans. − Nevertheless, the synthesis of diverse sulfated core 2 O- GalNAc glycans has not yet been reported. Herein, we report a diversity-oriented chemoenzymatic approach for the collective synthesis of sulfated core 2 O- GalNAc glycans 1 – 18 and their nonsulfated counterparts 19 – 36 (Figure ).…”