Terminal moieties branched chains

In this proposed process, p-hydride elimination first yields a putative hydride olefin rc-complex. Rotation of the -coordinated olefin moiety about its co-ordination axis, followed by reinsertion produces a secondary carbon unit and therefore a branching point. Consecutive repetitions of this process allows the metal center to migrate down the polymer chain, thus producing longer chain branches. Chain termination occurs via monomer assisted p-hydrogen elimination, either in a fully concerted fashion as illustrated in Figure 2b or in a multistep associative mechanism as implicated by Johnson1 et al. 

Fig. 3.6 Zinc porphyrins bearing oligoaniline with a pyridine moiety at the terminal of the chain. AFM image of the self-assembled branched polymer complex...

Liquid crystals based on aliphatic isocyanides and aromatic alkynyls (compounds 16) show enantiotropic nematic phases between 110 and 160 °C. Important reductions in the transition temperatures, mainly in clearing points (<100 °C), areobtained when a branched octyl isocyanide is used. The nematic phase stability is also reduced and the complexes are thermally more stable than derivatives of aliphatic alkynes. Other structural variations such as the introduction of a lateral chlorine atom on one ring of the phenyl benzoate moiety or the use of a branched terminal alkyl chain produce a decrease of the transition temperatures enhancing the formation of enantiotropic nematic phases without decomposition. 

The simplest approach to isosteric replacement of one or both sulfur atoms of the cystine disulfide with a methylene or ethylene moiety is given for natural bioactive peptides when one cysteine residue is located in the N-terminal sequence position and the related amino group or peptide extension is not involved in the bioactivity. This allows for direct side chain to backbone (N-terminus) cyclization via amide bonds with suitable 5-carboxyalkyl derivatives of the second cysteine residue, or with the oo-carboxy group of aminodicarboxylic adds containing an alkyl side chain that mimics the Ca to Ca spacer in cystine. Thereby, the length and degree of branching of the sulfide or alkyl spacer can additionally be varied. 

Starburst PAMAM dendrimers (Fig. 1), a specific class of commercially available dendrimers that have repeating amine/amide branching units, have drawn considerable interest in recent years due to their potential applications in medicine, nanotechnology, and catalysis [3-7]. These dendrimers are readily functionalized to terminate in diverse moieties such as primary amines, carboxylates, hydroxyls, or hydrophobic alkyl chains. Because dendrimer size and end groups can be varied, they are typically named by their generation (Gl, G2, etc.) and exterior functionality (- NH2, - OH). 

The three types of singlet or doublet aromatic protons correspond to aromatic protons in the monomer, the terminal unit and the repeating polymer unit, respectively. The two types of trans-olefinic protons are assigned respectively to those in the monomer and the terminal unit. The protons of the ethyl ester moiety are distinguished as three different types those in the monomer, in the branched group attached to cyclobutane next to the terminal unit, and in the polymer chain. 

Chemical structure elucidation of the carbohydrate moiety of a glycoprotein is a difficult problem because there is often chain branching and because the individual carbohydrate chains are not always identical. Specific exoglycosidases which release monosaccharide units only from the terminal nonreducing end of the carbohydrate chain are most useful in structural analysis. Among the enzymes available for sequence analysis... 

Other glycolipids are carbohydrate esters of fatty acids (such as mycolic acids). Mycosides are also part of this group and they contain a branched aliphatic chain with hydroxyl groups esterified by fatty acids and terminated at one end by a phenol group to which the carbohydrate moiety is linked. 

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