Isolated amine groups

Figure 21.6 SPDP can be used to activate an antibody molecule through its available amine groups to form a sulfhydryl-reactive derivative. Toxin molecules containing disulfide-linked A-B chains may be reduced with DTT to isolate the A-chain component containing a free thiol. The SPDP-activated antibody is then mixed with the reduced A chain to effect the final conjugate by disulfide bond formation.

The equilibrium between the amino and imino forms of cytosine has also been studied by Cieplak et al.9 Their results agree with those of Colominas et al. In this study, the related 2-oxopyridine and 2-oxopyrimidine molecules were also treated. In both these molecules the amine group of cytosine is not present, and in oxopyridine only one ring nitrogen is present. This enabled the keto-imino tautomerism to be studied in isolation. In both cases the imino form dominates in the gas phase, but the keto form is stabilised by solvation, and dominates in solution, in agreement with experiment. 

Didemnum rodriguesi from New Caledonia contained the unusual peptidyl alkaloid caledonin (76), that formed a complex with Zn2+ and Cu+ ions between thiol and primary amine groups [100], The minalemines D-F (77-79) are peptide guanidine derivatives isolated from a Caribbean collection of D. rodriguesi and contain a sulfamic acid group [101]. The stereochemistry of cyclodidemniserinol trisulfate (80) from a Palauan specimen of Didemnum guttatum was partially determined [102]. 

Deamination. Amine groups can be removed oxidatively via a deamination reaction, which may be catalyzed by cytochromes P-450. Other enzymes, such as monoamine oxidases, may also be involved in deamination reactions (see below). The product of deamination of a primary amine is the corresponding ketone. For example, amphetamine is metabolized in the rabbit to phenylacetone (Fig. 4.27). The mechanism probably involves oxidation of the carbon atom to yield a carbinolamine, which can rearrange to the ketone with loss of ammonia. Alternatively, the reaction may proceed via phenylacetoneoxime, which has been isolated as a metabolite and for which there are several possible routes of formation. The phenylacetoneoxime is hydrolyzed to phenylacetone. Also N-hydroxylation of amphetamine may take place and give rise to phenylacetone as a metabolite. This illustrates that there may be several routes to a particular metabolite. 

Most of the reactions of the 1,4-dicarbonyl compounds are the conventional reactions expected for isolated carbonyl groups. An important exception is formation of azacyclopentadiene (pyrrole) derivatives from 1,4-dicarbonyl compounds and ammonia or primary amines ... 

Dance and Guerney248 isolated a number of water-soluble complexes of (38) and X-ray analysis of a complex of Pb11 demonstrated its N—S coordination. The cyclic molecule 5-methyl-l-thia-5-azacyclooctane (39) forms complexes with Pd11 chloride and iodide in which it adopts a boat-chair configuration. These provide the first examples of bidentate chelates in which both thioether and tertiary amine groups are coordinated.132 H NMR analysis shows the inflexible chloride complex to remain bidentate in solution, whereas in the iodide chelate the ligand is S monodentate in dichloromethane. 

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