Pentasaccharide, sulfated

Certain recent models of mass spectrometer allow the use of a considerably easier injection technique. A solution of the sample to be analysed is injected directly into the apparatus by means of a syringe. Perfectly separated molecular peaks are observed. Here we will give the example of a sulfated pentasaccharide sodium salt, 9.11. In Chapter 17 we will come back to this synthetic compound (Lubineau et al. 1994), which is the best known human- selectin ligand today. Using the electrospray technique we observe the following peaks [M - Na ] 932.2, [M + Na ] 978.3, and [M + 2 Na ] 500.7. 

The synthesis of a collection of sulfated or sialylated oligosaccharides has confirmed that sulfates are the best inhibitors. The most active is the sulfated pentasaccharide 17.31 which is, until the present, the best ligand known of E-selectin, giving 50% inhibition at the very low concentration of 5 x 10 M (Lubineau et al. 1994). 

Figure 2 The heparin and heparan sulfate pentasaccharide sequence binding to AT III.

A synthetic 3-0-sulfated pentasaccharide, representing heparin s ATIII binding site (Figure 3) was first prepared by Choay, et.al., in a multi-step synthesis.24 clinical studies on this pentasaccharide, as an antithrombotic agent, demonstrated that it was not as effective as heparin itself and its cost probably precludes its use as a therapeutic... 

Additional studies have delineated more clearly the specificities of the acceptor and donor molecules in the cartil e system. Besides the hexa-sacoharide from chondroitin 4-sulfate, the homologous compounds from chondroitin and chondroitin 6-suIfate, as well as the tetrasaccharide from chondroitin 4-suIfate, also served as acceptors for Af-acetylgalactosaminyl transfer. Glucurono l transfer occurred wdth the sulfated pentasaccharide from chondroitin 6-sulfate, but, interestingly, the pentasaccharide from chondroitin 4-sulfate was completely inactive as acceptor. These acceptor specificities are summarized in Table IV. 

The most obvious conclusion from the work presented above appears to be that a great many aspects of the sulfation process are still unknown and that the mosaic of details cannot yet be integrated into a comprehensible overall picture. At this stage, it would seem reasonable to surest, however, that the process of sulfation in vivo most likely occurs concomitantly with the elongation of the polysaccharide chmns. The observ a-tion that the 4-sulfated pentasaccharide from chondroitin sulfate does not serve as an acceptor for glucuronosyl transfer indicates that sulfation must lag behind the elongation of the chain to some extent, but the exact relationship between polymerization and sulfation remains to be established. 

Degradation of heparin followed by affinity chromatography on immobilized AT III led to the identification of a pentasaccharide unit with high antithrombin affinity. This pentasaccharide 3 is characterized by a imique highly sulfated central glucosamine unit with a 3-0-sulfate group (Structures 2). 

This pentasaccharide sequence induces a conformational change in AT III which probably causes the complex to be more accessible to the active site of the proteases. The most relevant protease affected by the pentasaccharide 3 is factor Xa, but factor Xlla and plasma kallikrein activities can also be potentiated. Sequence 3 occurs in heparin as well as in various heparan sulfate proteoglycans of different origin including the vascular endothelium. 

For the inhibition of AT Ill-mediated thrombin activity, derivatives of 8 were prepared containing a flexible spacer of around 50 atoms plus a sulfated maltooligosaccharide or another AT III binding pentasaccharide [35]. 

Sdieme 2. Synthesis of sulfated Trestatin A pentasaccharide substructure 13... 

Scheme 6. [2+2+1] Block synthesis of heparan sulfate model pentasaccharide 20...

Fondaparinux is a chemically synthesized pentasaccharide that mimics the antithrombin-binding site of heparin and LMWH. Its molecular size (1728Da) is too small to bind to thrombin molecules while it is bound to antithrombin, Therefore, it is a pure anti-Xa inhibitor. It binds very little to platelets, proteins, or endothelium and is excreted in the urine, It does not form a complex with PF4 or other positively charged molecules. It is not neutralizable by protamine sulfate, Recent clinical trials have resulted in FDA approval for prophylaxis of deep vein thrombosis in orthopedic surgery, It has been shown to be effective and safe for the treatment of pulmonary embolism (20,21) and ACS (non-ST-elevation Ml) (OASIS 5—Michelangelo Trial) (17). 

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