Chiral polyamides amino acids

The molar ellipticity of these dendrimers was found to increase proportional to the number of chiral end groups. This is to be expected, in the absence of interactions between the terminal tryptophane moieties. No higher-generation dendrimers of this type have been reported. Other amino-acid-containing chiral dendrimers have been described by Meijer et al. who attached various amino acid derivatives to the periphery of poly(propylene imine) dendrimers (see Sect. 3) and more recently by Liskamp et al. (modification of polyamide dendra) [22] and Ritter et al. (synthesis of grafted polymerizable dendrimers containing L-aspartic acid components) [23]. 

Proteins are composed of 20 different alpha-amino acids and contain peptide linkages similar to those present in polyamides. With the exception of glycine, all the amino acids contain a chiral carbon. The geometrical shape and behavior of the giant proteins is a product of the various preferred geometries that allow the molecules to balance factors... 

The stereochemistry of step polymerization is considered now. Bond formation during step polymerization almost never results in the formation of a stereocenter. For example, neither the ester nor the amide groups in polyesters and polyamides, respectively, possess stereocenters. Stereoregular polymers are possible when there is a chiral stereocenter in the monomer(s) [Oishi and Kawakami, 2000 Orgueira and Varela, 2001 Vanhaecht et al., 2001], An example would be the polymerization of (R) or (S)-H2NCHRCOOH. Naturally occurring polypeptides are stereoregular polymers formed from optically active a-amino acids. 

Since pyrrolidinodiphosphines, e.g., Ph-CAPP, and BPPM, gave excellent stereoselectivities, we prepared a series of new chiral pyrrolidinodiphosphines, in which the nitrogen atom of PPM (, 11) is linked up with a variety of a-aminoacyl groups. The rhodium complexes with these ligands may serve as good bio-mimetic models of reductase when they are anchored on polymers especially polyamides. a-Aminoacyl-PPMs ( ) were prepared by the condensation of PPM with an N-CBZ-a-amino acid or an N-CBZ-dipep-tide in the presence of dicyclohexylcarbodiimide (DCC) and 1-hy-droxybenztriazole (HOBT)(eq. 3). 

IV. Chiral A,B-Type Polyamides (Nylons-n) Based on Amino Acids ... 

D-and L-Poly(lysine) both occur in a helical conformation in aqueous solution above pH 10. A 1 1 mixture of both helices in water precipitates in the form of regular, silk-like P-sheets (Fig. 9.5.3). This is a polypeptide example of the chiral bilayer effect. It demonstrates the importance of chiral uniformity not only for noncovalent, soft-membrane systems, but also for covalent polyamides. Helical fibers in aqueous gels do not survive the addition of enantiomeric fibers with the single exception of DNA (see Fig. 8.6.1). The precipitation of enantiomeric peptides containing more than one kind of amino acid has, however, not been reported so far. 

Orgueira H.A., Bueno M., Runes J.L., Varela O., Galbis J.A., Synthesis and characterization of chiral polyamides derived from glycine and (S)-5-amino-4-methoxypentanoic acid, J. Polym. Sci Part A Polym. Chem., 36, 1998, 2741-2748. 

Figure 3 shows examples of the polymer-type CSPs [4, 5, 8]. Various chiral polymers including polymethacrylates (3,4), poly[(meth)acrylamides] (5,6), polymaleimide (7), polyacetylenes (8,9), poly(a-amino acid) (10,11), polyamides (12-14), polyurethane (15), proteins (16), and polysaccharide derivatives (17,18) have been evaluated as CSPs. 

PepNAs are achiral and insensitive to CD, but optically pure polyamide nucleic acid analogues were also reported. Monomer 28 (Scheme 8) has naturally occurring amino acid units, which will confer chirality on the resulting polymers [65]. Although stereocenters on the backbones were expected to influence the complexation of the PepNAs, no details were reported. Polymer 29... 

In 1971, Davankov et al. achieved the first baseline separation of enantiomers using a small molecule-based CSP consisting of L-proline [1], Since then, a wide range of chiral small compounds, which include amino acids, cyclodextrins, macrocyclic glycopeptides, cinchona alkaloids, crown ethers, jt-basic or rt-acidic aromatic compounds, etc., have been used as CSPs [2—6], On the other hand, the polymer-based CSPs are further divided into two categories, i.e., synthetic and natural chiral polymers [7, 8]. Typical examples of the synthetic polymers are molecularly imprinted polymer gels, poly(meth)acrylamides, polymethacrylates, polymaleimides, and polyamides, and those of the natural polymers include polysaccharide derivatives and proteins. 

A chiral p-polyamide 83 of the Nylon 3 type was also synthesized [68, 69] by Galbis et al. by ring-opening polymerization of the p-lactam derived from 3-amino-3-deoxy-2,4,5,6-tetra-(9-methyl-D-altronic acid. 

Garcia-Martin M.G., De Paz Bdnez M.V., Galbis J.A., Preptuation of 3-amino-3-deoxy-2,4,5,6-tetra-0-methyl-D-altronic acid hydrochloride, an intermediate in the preparation of a chiral p-polyamide (nylon 3 antilog), J. Carbohyd. Chem., 19, 2000, 805-815. 

Protease was used as catalyst for polymer modification. Phenylalanine residues at the side chain of methacrylamide polymers were coupled with alanine (-butyl ester by Q -ch3nnotrypsin catalyst in water-chloroform solvent (71). Up to 35% peptide-bond formation was achieved for 7 days at room temperature. Polyamide synthesis was performed by cellulase-assisted polycondensation of chiral fiuorinated compoimd having carboxylic acid and amino groups (72). 

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