Chemical Synthesis of Sialosides

Synthesis and Stereocontrolled Equatorially Selective Glycosylation Reactions of a Pseudaminic Acid Donor: Importance of the Side-Chain Conformation and Regioselective Reduction of Azide Protecting Groups

“…37–39 NeuAc on the other hand is found exclusively in the form of its equatorial glycosides, 40–44 for whose preparation a number of effective chemical methods are now available. 45–51 Leg differs from NeuAc, with whom it shares the D- glycero -D- galacto configuration only by the absence of a C-O bond at the 9-position and by replacement of a C-O by a C-N bond at the 7-position, whereas Pse with the L- glycero -L- manno configuration differs from NeuAc in configuration at both the 5- and 7-positions in addition to the deoxygenation at C9 and the N for O substitution at C7 (Figure 1). Other members of the class include acinetaminic acid 4 and fusaminic acid 5 (Figure 1), and the 4- and 8-epimers of legionaminic acid (not shown).…”

“…The bacterial sialic acids legionaminic (Leg) 1 and pseudaminic acid (Pse) 2 and their glycosides, congeners of the ubiquitous N -acetyl neuraminic acid (NeuAc) 3 glycosides, are a case in point (Figure ). Leg and Pse are found in a diverse range of bacterial capsular and lipopolysaccharides in the form of both axial and equatorial glycosides , and offer broad opportunities for the development of antibacterial therapeutics and/or vaccines. − NeuAc on the other hand is found exclusively in the form of its equatorial glycosides, − for whose preparation a number of effective chemical methods are now available. − Leg differs from NeuAc, with whom it shares the d - glycero - d - galacto configuration only by the absence of a C–O bond at the 9-position and by replacement of a C–O by a C–N bond at the 7-position, whereas Pse with the l - glycero - l - manno configuration differs from NeuAc in configuration at both the 5- and 7-positions in addition to the deoxygenation at C9 and the N for O substitution at C7 (Figure ). Other members of the class include acinetaminic acid 4 and fusaminic acid 5 (Figure ) and the 4- and 8-epimers of legionaminic acid (not shown). ,,− …”

Comparison of glycosyl donors: a supramer approach

“…The development of effective means for the preparation of α-sialosides through chemical glycosylation (sialylation) received considerable attention since sialo-containing saccharides and conjugates are im-portant for advancing glycobiology [12,13] and glyco-medicine [14,15]. However, the reliable installation of sialic acid residues in oligosaccharides is a rather difficult issue and poor predictability remains characteristic of the sialylation reaction [16][17][18][19][20][21]. As in other glycosylation reactions [22][23][24][25][26][27][28][29], the result of sialylation is affected by a variety of variables [30][31][32][33][34][35][36][37][38][39] including the nature of protective groups on either partner [26,38,[40][41][42][43][44][45] and concentration of reagents [31,33,34,37,39,43,44,46].…”

Comparison of glycosyl donors: a supramer approach

“…The development of effective means for the preparation of -sialosides through chemical glycosylation (sialylation) received considerable attention since sialo-containing saccharides and conjugates are important for advancing glycobiology [12,13] and glyco-medicine [14,15]. However, the reliable installation of sialic acid residues in oligosaccharides is a rather difficult issue and poor predictability remains characteristic of the sialylation reaction [16][17][18][19][20][21]. As in other glycosylation reactions [22][23][24][25][26][27][28][29], the result of sialylation is affected by a variety of variables [30][31][32][33][34][35][36][37][38][39] including the nature of protective groups on either partner [26,38,[40][41][42][43][44][45] and concentration of reagents [31,33,34,37,39,43,44,46].…”