Amino group, structure

Insight into the effects of amino group structure on the carbon basicity of enamines is also available from data on the protonation of indoles and pyrroles Although the absolute basicities of these compounds are a good deal less than those of simple aliphatic enamines, the effects of A-alkylation should be transferable to ordinary enamines. Alkylation at nitrogen (that is, conversion of a secondary to a tertiary indole or pyrrole) enhances C-basicity by 0.6-2.0 pK units, the increment depending on other structural details. Predictably, A-phenyl-2,5-dimethylpyrrole is less basic (by 1.3 pK units) than 2,5-dimethylpyrrole itself. ... 

Hen egg-white lysozyme has been partially N-acetylated in order to facilitate a study of the interactions between the carboxylic acid groups and amino-groups. Structural considerations and the results of pH titration indicated that the carboxylic acid groups of aspartic acid-48, -66, and -87 are not titratable in the acetylated lysozyme, which contains fewer titratable groups in the pH range 7—10 than does the native enzyme. 

The terminal amino group of 2-hydrazino-4-phenylthiazole is also the reactive center in reactions with activated aryl halides such as 288. A solution of the product (289) obtained from this reaction when shaken with PbOj gives a deeply colored radical, whose structure has been studied by ESR (Scheme 173) (532. 533). 

The 3-amino group brings a second nucleophilic center in these structures thus 2-imino-3-amino-4-methyl-4-thia201ine (409) reacts with methyl diloroformate to give the bicyclic compound (410) (Scheme 234). Other thiazolo-s-triazoles of the [3.2-l>] type have been obtained by... 

Compounds of this type possess a definite Aj-selenazoline structure, while homologous compounds with at least one labile hydrogen on the 2-amino group can exist as a tautomeric equilibrium (Scheme 64). 

Another important correlation between structure and properties in the pteridine series is seen in the solubilities, to which insufficient attention has been paid in general. Introduction of an amino group into pteridine (1) lowers the solubility in all solvents despite the fact... 

The two NH2 stretching vibrations of aminopyrazoles follow the Bellamy-Williams relation [r-jlNH) = 345.5-0.876r <,s(NH)] (76AHC(Sl)l) establishing the amino tautomeric structure of (91). Azidopyrazoles also show the Vs and Vas bands of the azido group. The... 

In the search for new structures with antiinflammatory activities some 1-substituted 3-dimethylaminoalkoxy-lJ/-indazoles (704) have been synthesized and pharmacologically tested (66JMC38). Doses of 20-40 mg g i.p. produced sedation, muscle relaxation and motor incoordination, whereas doses of 80-100 mg kg produced depression. Toxicity was fairly constant in all series, varying from 120 to 150 mg kg i.p., with the exception of compounds possessing a nitro group or an amino group in the indazole nucleus, which provoked cyanosis. 

As can be seen from Table 3, only modifications at the 6/3-amino groups have been successful in producing penicillins of medical significance up to this time. Several reviews have dealt with the structure-activity relationship in this area in considerable detail B-80MI51102, B-77MI51106, B-75MI51102) and should be consulted for the actual effects of structural modification on antibacterial activity. 

Notice that the MO picture gives the same qualitative picture of the substituent effects as described by resonance structures. The amino group is pictured by resonance as an electron donor which causes a buildup of electron density at the /3 carbon, whereas the formyl group is an electron acceptor which diminishes electron density at the /3 carbon. 

Analogous compounds with a secondary amino group (a,j8-unsaturated secondary amines) can, in principle, exist in either the form of imines (6) or the tautomeric form of enamines (7). As they practically occur and react in the former structure, it is more convenient to use the group designation imines. ... 

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