Chain extenders traditional

An interesting thiosugar, salacinol 45, containing sulfur atoms in two different oxidation states was isolated and found to be the active principle of the Indian plant Salacia reticulata which is used in local traditional medicine for treatment of diabetes [96]. The compound was shown to be a potent inhibitor of intestinal a-glucosidases comparable in its activity with the powerful aminosugar derivative acarbose [97]. Kotalanol (46), a chain-extended homolog of salacinol, was discovered around the same time [98]. 

In parallel to this push for extending the borders of chemical process systems engineering to areas that have been traditionally the reserve of industrial engineers, a new concept of supply chemical chain was recently discussed in detail by Grossmann and Westerberg (2000), and in the United States National Academies report by Breslow and Tirrell (2003). The chemical supply chain extends from the molecule level to the whole enterprise. Breslow and Tirrell (2003) suggest that ... 

For these reasons, among the family of segmented polyurethanes currently used in cardiovascular applications for their desirable properties, poly-urethane-maleamides (PUMAs) appear to be of particular interest. PUMAs are obtained with dicarbojQ lic acids as chain extenders, instead of traditional diols and diamines. The use of maleic acid as chain extender allows the insertion in the polymer chain of activated double bonds, which can perform as grafting sites for further derivatisation in aqueous solutions and mild conditions. ... 

The traditional method for preparing activated esters of A -protected dipeptides is combination of the A-protected amino acid with the amino acid ester (Figure 7.16). The latter is obtained by A-deprotection of the diprotected amino acid in an acidic milieu. Coupling is achievable using the carbodiimide, mixed-anhydride, and acyl-azide methods. Success with this approach indicates that the esterified residues react preferentially with the other derivatives and not among themselves. The chain cannot be extended to the protected tripeptide ester because the dipeptide ester cyclizes too... 

---