The synthesis of heterosaccharides related to the fucoidan from Chordaria flagelliformis bearing an α-l-fucofuranosyl unit

Abstract

Sulfated polysaccharides, fucoidans, from brown algae are built up mainly of α-L-fucopyranosyl units and form a group of natural biopolymers with a wide spectrum of biological activities. Systematic synthesis of oligosaccharides representing fucoidans' fragments gives molecular probes for detecting pharmacophores within fucoidan polysaccharide chains. Recently, it was discovered that the fucoidan from brown seaweed Chordaria flagelliformis contains not only α-L-fucopyranosyl units but also α-L-fucofuranosyl ones. To establish the influence of the unusual α-L-fucofuranose residue on the biological activity and conformational properties of fucoidans, the synthesis of selectively O-sulfated pentasaccharides, which represent the main repeating unit of the fucoidan from C. flagelliformis, was performed. The features of the synthesis were the use of the pyranoside-into-furanoside rearrangement to prepare the fucofuranoside precursor and remote stereocontrolling participation of O-acyl groups to manage stereoselective α-bond formation in glycosylation reactions.

Design of α-Selective Glycopyranosyl Donors Relying on Remote Anchimeric Assistance

“…There are few examples when bis‐acylated donors were successfully applied for the preparation of complex oligosaccharides containing 1,2‐ cis ‐linkages. In particular, 3,4‐di‐O‐acylated fucosyl donors were extensively used for the preparation of sulfated oligofucosides and fragments of Lewis X structures . They were also used in other, stereoselectivity unrelated, investigations in which they proved to be completely α‐selective …”

Pyranoside‐into‐Furanoside Rearrangement of 4‐Pentenyl Glycosides in the Synthesis of a Tetrasaccharide‐Related to Galactan I of Klebsiella pneumoniae

“…Previously, a preparative protocol for the PIF rearrangement of different glycosides bearing an allyl group as a temporary protecting group at anomeric position was developed . In this communication, we expand the scope of this process by using an aglycon that can act as a leaving group during glycosylation.…”

“…This was then subjected to the PIF rearrangement (Scheme ). The standard protocol for this rearrangement, which was successfully applied in the synthesis of oligosaccharides related to polysaccharides from Aspergillus fumigatus ,, Enterococcus feacalis , Chordaria flagelliformis , involves treatment with a Py · SO 3 /HSO 3 Cl mixture, followed by neutralization with NaHCO 3 , and solvolytic desulfation in the presence of acidic resin IR‐120 (H + ). Unfortunately, under these conditions substrate 9 gave only 27 % of target disaccharide 16 (Scheme , Table , entry 1).…”

Fucoidan-Mimetic Glycopolymers : Synthesis and Biomedical Applications

“…Since 2000 this group has synthesized a broad series of mono-, di-, tri-, tetra-, hexa-, octa-, dodeca-, and hexadeca-α-L-fucosides (see Figure 1.2 C) bearing various glycosidic linkage patterns, branching, and sulfation degree and patterns [35][36][37][38][39][40][41][42]. Recently, this group synthesized a fragment from the brown seaweed Chordaria flagelliformis containing an α-L-fucofuranosyl unit (see Figure 1.2 D), which is unusual compared to the α-L-fucopyranosyl conformation that constitutes the vast majority of the L-fucosides found in fucoidan [43]. The conformation of all of these fucosides have been carefully studied by NMR spectroscopy, but their biological properties have remained almost entirely unpublished [35][36][37][38][39][40][41][42][43].…”

“…Recently, this group synthesized a fragment from the brown seaweed Chordaria flagelliformis containing an α-L-fucofuranosyl unit (see Figure 1.2 D), which is unusual compared to the α-L-fucopyranosyl conformation that constitutes the vast majority of the L-fucosides found in fucoidan [43]. The conformation of all of these fucosides have been carefully studied by NMR spectroscopy, but their biological properties have remained almost entirely unpublished [35][36][37][38][39][40][41][42][43]. As an exception a recent study showed that a fully sulfated α(1→3) octa-L-fucoside displayed no or decreased antibacterial phagocytic activity compared to fucoidan of larger molecular weights from natural sources [44].…”