Amine deamination

The products formed in deamination depend on the lifetimes of the different ion-pair species, which, in turn, depend on the structure of the amine and the nature of the solvent. The counter-ion in such reactions can conveniently be varied by using N-nitrosoamides as starting materials. These compounds react to give diazonium ion-pairs in reactions that closely resemble amine deamination, and the lifetime of the ion-pairs can be studied by using lsO-labelled ni-trosoamides (see Scheme 2, XH = solvent or added nucleophile). 

The difference between the behavior of the 6-amino-6-deoxy-D-glucose and -L-idose derivatives can be rationalized as follows. In the transition states for the formation of the 3,6-anhydro ring from the Tt-gluco isomers, the oxygen (or hetero) atoms attached to C-4 and C-5 are in a sterically unfavorable, cis relationship. The transition states from the h-ido amines involve a trans relationship of these hetero atoms. Thus, for the D-gluco amine, deamination reactions other than 3,6-anhydro ring-formation compete more effectively. 

The reaction mechanism of amine deamination and disproportionation has been put forward by analogy with other eliminations, namely dehydration and dehydrochlorination [149,155], its characteristic feature being the cooperation of acidic and basic sites. In the deamination, /3-hydrogen and the NR2 group (R is hydrogen or alkyl) are eliminated by an E2-like mechanism on alumina, but by an El-like mechanism on silica-alumina. The nature of the acidic sites is not clear, protons from surface hydroxyls or aluminium ions are possible candidates. However, it seems... 

Esterolysis, decarboxylation, amination, deamination and oxidoreduction are catabolic enzyme activities of proteinoids and proteinoid microspheres. The formation... 

Coenzymes and vitamins are Nature s versions of common organic reagents Reductions with NADH Reductive amination, deamination, and decarboxylation with pyridoxal Enol chemistry with lysine enamines, with coenzyme A, and with phosphoenolpyruvate Umpolung chemistry with thiamine as a d reagent... 

We have reviewed the early history of primary aliphatic amine deaminations up to the 1950 s in Section 7.1. The mechanisms that were postulated and evaluated until the late 1960 s or mid-1970 s have been discussed by various authors (White and... 

Nucleophilic substitution reactions that occur under conditions of amine deamination often differ significantly in stereochemistry, compared with that seen in halide or arenesulfonate solvolysis. The results of four key substrates are summarized in Table 5.13. It can be seen (entry 1) that displacement of nitrogen on the 1-butyldiazonium ion is much less stereospecific than the 100% inversion observed on acetolysis of the corresponding brosylate. Similarly, the secondary system (entry 2) affords 2-butyl acetate with only 28% inversion of configuration. Furthermore, a crossover to net retention of configuration is observed as the alkyl group becomes better able to stabilize a carbonium ion. The small net retention (10%) observed in deamination of 1-phenylethylamine increases to 28% retention in the tertiary benzylic system 2-phenyl-2-butylamine. 

What appears to be happening in amine deaminations can be understood in terms of a modified ion-pair scheme. The positively charged diazonium ion will be strongly solvated in the vicinity of nitrogen by acetic acid. Since the leaving group is... 

Interconversions of the cytidine and uridine series are depicted in Fig. 12-1 it is apparent that only a few amination-deamination reactions link... 

A single reagent (53) is offered in place of the combination of ninhydrin and phenylacetaldehyde for the fluorimetric assay of primary amines. Deamination of primary amines leads to the same product distribution whether nitrogen or nitrous oxide is the gas molecule expelled once again, the existence of disorder in the product-forming steps is invoked. Micellar stereochemical control in nitrous acid deamination has been reported. ... 

In the buffered hydrolysis of N-methyl-4-(chrysanthemyloxy)-pyri-dinium iodide (16-OPy-hI ), a leaving group which is expected to minimize internal return, the naturally occurring allylic isomers, artemisia and yomogi alcohols (18 and 19) are the major products, but a small amount (0.5%) of santolina alcohol (17) is present (66, 67). Similar results have been reported for amine deamination (69) and dinitro-benzoate solvolysis (66, 67, 70). The absolute configuration of natural santolina alcohol corresponds to that of chrysanthemic acid, as predicted by the Bates and Paknikar biogenesis (73). 

Under the kinetically controlled conditions of the solvolysis reactions and amine deamination, there is no evidence for either 1,3-hydrogen elimination to trachylobane or 1,3-hydrogen shift. Trachylobane formation (12%) has, however, been observed in the decomposition of the tosyl-hydrazone (279) under high temperature, protic conditions 346). Since aprotic decomposition (presumably via carbene), produces only olefinic products, it would appear that the cyclopropane ring is formed through a cationic pathway. 

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