Polyamines reduction

Monoalkylation of polyamines. Reductive cleavage of aminals and am idines by DIBAH can be used to effect monoalkylation of polyamines.5 Examples ... 

Reduction of azides is a classical approach to primary amine synthesis. Treatment of 17 with sodium azide in DMF or in THF/H2O mixtures in the presence of phase transfer catalysts effects a quantitative conversion to the corresponding polymeric azide, 27. Recently the reduction of azides to primary amines via hydrolysis of iminophosphoranes produced by interaction of the azide with triethyl phosphite was reported.30 Application of this technique to the azidomethyl polymer, 27, as shown below, failed to produce a soluble polyamine. 

Combinatorial approach to unsymmetrically tiered macromolecules [214] is a brand new area of research which would allow dendrimerization of materials (e. g., glass, classical polymers, fibers) and thus enable fine tuning of macromole-cular properties. For example, treatment of an amine terminated dendrimer with a mixture of complementary, isocyanate-based monomers [215, 216] affords a heterogeneous surfaced dendrimer. Selective transformation of the surface nitrile moieties via metal-catalyzed reduction to obtain a new polyamine dendrimer allows further combinatorial-based elaboration as illustrated in Fig. 42. 

The laccases, classed as polyphenol oxidases, catalyze the oxidation of diphenols, polyamines, as well as some inorganic ions, coupled to the four-electron reduction of oxygen to water see Fig. 12.4 for the proposed catalytic cycle. Due to this broad specificity, and the recognition that this specificity can be extended by the use of redox mediators [27], laccases show promise in a range of applications [28], from biosensors [29-32], biobleaching [27, 33-35] or biodegradation [36], to biocatalytic fuel cells [1-3, 18, 26, 37-42]. 

Sequential hydroformylation/reductive amination of dendritic perallylated polyglycerols with various amines in a one-pot procedure to give dendritic polyamines in high yields (73-99%). Furthermore, the use of protected amines provides reactive core-shell-type architectures after deprotection. These soluble but membrane filterable multifunctional dendritic polyamines are of high interest as reagents in synthesis or as supports in homogeneous catalysis as well as nonviral vectors for DNA-transfection (Scheme 18) [65]. 

The electrocatalytic reduction of nitrous oxide to dinitrogen has been achieved at a mercury electrode using Ni(II) complexes of macrocyclic polyamines [355]. 

Recently another family of dendrimers has become commercially available. These polyamines were developed by Meijer and de Brabander-van den Berg of DSM Research and are based on Vogtle s initial synthesis [7]. In this case the troublesome reduction step was performed using a Raney cobalt hydrogenation catalyst and other process improvements have permitted this synthesis to be continued up to the fifth generation with multikilogram quantities available. 

Peptides can be chemically transformed on insoluble supports to yield other types of oligomer. These transformations include N-alkylation and reduction. N-Alkylation of polystyrene-bound peptides enables the preparation of peptide mimetics with improved enzymatic stability [270], Polyamines have been prepared by exhaustive reduction of peptides with borane [271] (see Section 10.1.6). N-Alkylated polyamines can be prepared on solid phase by reduction of the corresponding N-alkylated peptides [272]. 

Again, the precise roles of coordination-compound chemical sensitizers, in most cases, are not understood. In fact, their effects may have little to do with their own coordination chemistry. Many simple salts of gold and other noble metals are effective sensitizers. They also may be added to solutions during silver halide precipitation to produce doped emulsions that have special properties. A variety of compounds that can act as ligands to metal ions are also effective alone as chemical sensitizers, the result of complicated oxidation-reduction, ion replacement and adsorption reactions on the silver halide grain surface. These include polyamines, phosphines and thioether- or thiol-containing compounds. The chemistry of these materials with the silver halide surface is discussed in the reference literature. 

Reduction of dihydropyrimidines by the use of excess sodium borohydride in methanol, at 60 °C, has been used as a route to substituted polyamines (equation 76). The reaction occurs in a stereocontrolled fashion and gives reasonable yields. These latter molecules are synthetic targets due to their potential in chemotherapy. 

Vakurov et al. [46] evaluated a strategy to improve the covalent binding of AChE to screen-printed carbon electrodes modified with polyamines. To improve the extent of dialdehyde modification, electrodes were aminated. Initially, this was performed by electrochemical reduction of 4-nitrobenzenediazonium to a nitroaryl radical permitting attachment to the carbon surface subsequent reduction of the 4-nitrobenzene yielded a 4-aminobenzene-modified carbon surface. The obtained biosensors resulted in very sensitive devices measuring as low as 10 10 M of OPs. 

We suggested that an early release of DNA during or after penetration into the cell, probably promoted by the reduction of a disulfide bridge placed between the polyamine and the lipid, implies a total loss of... 

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