Synthesis of Chondroitin Sulfate Oligosaccharides Using N‐(Tetrachlorophthaloyl)‐ and N‐(Trifluoroacetyl)galactosamine Building Blocks

Abstract

We have explored synthetic routes for the preparation of chondroitin sulfate (CS) oligosaccharides based on the use of N‐tetrachlorophthaloyl‐ (N‐TCP) and N‐trifluoroacetyl‐substituted (N‐TFA) galactosamine building blocks. Using N‐TCP units, we carried out the total synthesis of two CS disaccharides, demonstrating the compatibility of TCP protection with the final deprotection/sulfation steps. However, an attempted 2 + 2 coupling of N‐TCP‐containing disaccharides for the synthesis of CS tetrasaccharides failed. In contrast, a synthetic route using N‐TFA galactosamine units efficiently led to biologically relevant CS‐like oligosaccharides. The N‐TFA groups could easily be removed at the end of the synthesis, and microwave irradiation greatly facilitated the sulfation reactions. The utility of this approach is illustrated with the total synthesis of two CS‐like tetrasaccharides with different sulfate distribution patterns. Finally, we used a fluorescence polarization assay to estimate the relative abilities of the synthesized compounds to inhibit the interaction between FGF‐2 and heparin.

Improvement on binding of chondroitin sulfate derivatives to midkine by increasing hydrophobicity

“…IC50 values in the range of 17-20 µM were obtained (Table 1 and Figure S2, supporting information). These results were in sharp contrast with that displayed by fully deprotected CS-E disaccharide 7, 23 which did not inhibit the fluorescent probe-midkine interaction (IC50 > 250 µM). 21 Therefore, protected disaccharides 4-6 displayed equivalent relative affinities, much higher than that showed by the naturally occurring CS-E disaccharide.…”

Chondroitin Sulfate Tetrasaccharides: Synthesis, Three‐Dimensional Structure and Interaction with Midkine

“…We previously developed a synthetic strategy for the preparation of CS‐like tetrasaccharides in the GlcA–GalNAc sequence (see below) . This approach was based on the use of N ‐trifluoroacetyl ( N ‐TFA)‐protected galactosamine building blocks .…”

“…Next, we studied the interactions between midkine and our collection of chemically synthesised heparin and CS oligosaccharides (Figure ) . The library comprises CS‐like di‐ and tetrasaccharides, which differ in sulfation pattern and sequence, including compounds 14 and 15 .…”

“…Next, we studied the interactions betweenm idkine and our collection of chemically synthesised heparin [16] andC So ligosaccharides ( Figure 1). [11,12] The library comprises CS-liked i-and tetrasaccharides, which differ in sulfation pattern and sequence, including compounds 14 and 15.T etrasaccharides 16 and 17 have the alternative GlcA-GalNAc sequence and contain seven sulfateg roups, which is as ulfation pattern corresponding to CS-T [9a] with an additional sulfate group at position 4ofthe non-reducing end. Analysis of the binding properties of these CS analogues, which are only accessible through chemicals ynthesis, is interesting because it has been recently reported that oligosaccharides with novel "synthetic" sulfation profiles display relevant biological properties.…”

“…We previously developed as ynthetic strategy for the preparation of CS-like tetrasaccharides in the GlcA-GalNAc sequence (see below). [11] This approach was based on the use of N-trifluoroacetyl (N-TFA)-protectedg alactosamine building blocks. [12] We showedt hat this type of GalNAc units was very convenient for the synthesis of CS oligomers, since the N-TFA protecting group ensured the selectivef ormation of the required 1,2-trans-glycosidic bond and could be easily removed at the end of the synthetic route to install the naturally occurring 2-acetamido moiety.A part from the length and sulfation pattern,t he sequence (GlcA-GalNAc or GalNAc-GlcA) is another important feature to consider when studying the interactions between CS oligosaccharides and proteins.…”