Functionalizing the Amino Group

Isothiocyanates react with nucleophiles such as amines, thiols and hydrojy groups however, the only stable product of these reactions is with 

Seheme 1.10 Reaction of primary amines with sulfonyl chlorides. 

This type of functionalization is common in polysaccharide chemistry but it also has applications in other fields. It has been employed for the introduction of self-fluorescence of nanocomposites as well as for the transformation of aldehyde end-capped polymers into amine end-capped ones.  

Reductive amination, which has been described in Section 1.2.1.5, is applicable in this case as well. Using a mild reducing agent, the Schiff bases 

This type of synthetic approach to create aldehyde groups, which react with nucleophiles in a subsequent step, is common for the modification of carbohydrates. 

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By appending sLe epitopes to an aromatic template and functionalizing the amino group of sLe with a large, hydrophobic residue 21 (O Fig. 15), a compound more effective (8-fold) than the aforementioned dimers was generated. The small increases in functional affinities obtained with these bivalent compounds suggest that they may make favorable contacts outside of the... 

Pyridoxal Derivatives. Various aldehydes of pyridoxal (Table 3) react with hemoglobin at sites that can be somewhat controlled by the state of oxygenation (36,59). It is thereby possible to achieve derivatives having a wide range of functional properties. The reaction, shown for PLP in Figure 3, involves first the formation of a Schiff s base between the amino groups of hemoglobin and the aldehyde(s) of the pyridoxal compound, followed by reduction of the Schiff s base with sodium borohydride, to yield a covalendy-linked pyridoxyl derivative in the form of a secondary amine. 

The reactivity of the amino groups at the pteridine nucleus depends very much upon their position. All amino groups form part of amidine or guanidine systems and therefore do not behave like benzenoid amino functions which can usually be diazotized. The 4-, 6-and 7-amino groups are in general subject to hydrolysis by acid and alkali, whereas the 2-amino group is more stable under these conditions but is often more susceptible to removal by nitrous acid. 

Amino acids undergo reactions characteristic of both their anine and carboxylic acid functional groups. Acylation is a typical reaction of the amino group. 

In addition to illustrating the mechanics of translation. Figure 28.12 is important in that it shows the mechanism of peptide bond formation as a straightforward nucleophilic acyl substitution. Both methionine and alanine are attached to their respective tRNAs as esters. The amino group of alanine attacks the methionine carbonyl, displacing methionine from its tRNA and converting the carbonyl group of methionine from an ester to an anide function. 

In the next step, the best candidate from the series 2-oxo-4-(9-phenanthryl)-dihy-dropyrimidine 22 was prepared and isolated in enantiomerically pure form, then attached to a macroporous polymer support. To attach the isolated selector to the amino functionalized macroporous polymethacrylate support, a suitable reactive handle had to be introduced into the dihydropyrimidine. We chose to functionalize the methyl group at the C6 carbon atom by a simple bromination to afford (-)-22. Coupling of this compound to the amino functionalized support then gave the desired chiral stationary phase CSP 12 (Scheme 3-6) containing 0.20 mmol g of the selector. 

Compound 14 can be dismantled in a productive fashion by ret-rosynthetic cleavage of the indicated bonds (see Scheme 4). The intermolecular attack of the amino group in 15 upon the keto function in 16 would be expected to result in the formation of the desired oxime ether after loss of a water molecule. A few functional group manipulations would then complete the synthesis of intermediate 14. A valuable structural feature of 15 is the C-2 oxygen substituent. Although this oxygen atom is not expressed in the natural product, it would certainly play an important role in our... 

The base of the aniline derivative has zero charge, and therefore H0 has to be used in 2-aminothiazole the heterocyclic nitrogen is protonated first and at much lower acidities than is the amino group (see Sec. 3.2). The protonation of the amino group of a cationic species therefore has to be treated using the H+ function (Rochester, 1970). 

In each case, the N atom is sp hybridized, with one lone pair of electrons and three o-bonds. A quaternary ammonium ion is a tetrahedral ion of the form R4N, where as many as three of the R groups (which may all be different) can be replaced by H atoms. For example, the tetramethylammonium ion, (CH3)4N+, and the trimethylammonium ion, (CH3)3NH+, are quaternary ammonium ions. The amino group, the parent functional group of amines, is —NH2. 

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