Bisamidates, symmetrical

A C2-symmetrical conformation was deduced for the bisamides 123a and 123b in solution on the basis of their NMR spectra244 (e.g. two doublets for OCH2CO, four doublets for ArCH2Ar and four doublets for ArH protons), and further established by X-ray analysis for 123a. 

Figure 12-5 The Relationship of Enantioselective Desymmetrization to Sense of Phosphine Orientation in C2-Symmetric Bisphosphine-Bisamide Ligands 562...

When the amide is derived from an amino acid, achieving a neutral species requires esterificatiOTi of the carboxyl group as well (e.g., 60). After examination of a series of 25 diamidates for activity against HCV [120] and HIV replication, and anti-proliferative effects in several cell lines, it was found that this strategy is sufficient to afford good cellular activity with several different nucleoside analogues [119]. Preparation of symmetrical bisamidates from the symmetrical diesters also has been reported (Fig. 12) [121]. 

Anhydrides of the chelator react with primary amines of the biomolecules. Symmetrical dianhydride of DTPA is commercially available and the conjugation may be performed in both aqueous and nonaqueous media. As the dianhydride might react to form a DTPA-monoamide as well as a DTPA-bisamide, cross-linkage of two biomolecules may occur. To circumvent this, asymmetric anhydrides of DTPA but also of DOTA have been developed and used (Sherry et al. 1989 Sieving et al. 1990). 

Owing to their superior mechanical properties derived from the symmetrical bisamide-diols and succinyl chloride groups, poly(ester amides) have been investigated as potential candidates for bioresorbable suture materials [18]. Attempts have also been made to increase the degradation rate of poly(ester amides)... 

Stapert H R, Dijkstra P J, Feijen J (1998), Synthesis and characterization of aliphatic poly(ester-amide)s containing symmetrical bisamide blocks , Macromol. Symp., 130, 91-102. 

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