Nitrogen nucleus, properties

N — H Protons Protons on nitrogen often show broadened signals in the NMR, both because of moderate rates of exchange and because of the magnetic properties of the nitrogen nucleus. Depending on the rate of exchange and other factors, N—H protons... 

Lactam antibiotics are natural or semisynthetic compounds whose basic nuclear structure consists of a -lactam ring coupled to a thiazolidine (five-membered) or a dihydrothiazine (six-membered) ring to form the penicillin or cephalosporin nucleus, respectively. To those nuclei, various side chains that determine most of the properties of the different -lactams are attached. All members of this group of antibiotics are readily attacked at the -lactam nitrogen by nucleophilic reagents such as hydroxyl ions, alcohols, and primary amines, as well as by secondary amines. They are also susceptible to electrophilic attack at both the... 

Investigation of replacement of the 5-methoxy group by substituents with different electronic and lipophilic properties and methylation of the indole nitrogen or its replacement by a sulfur atom was evidence for the shift of the 5-methoxy group to the 4-position of the indole nucleus led to the most active radical scavenger but much less effective as a cytoprotectant [135]. 5-alkoxy-2-(N-acylaminoethyl)indole (Fig. 15) appeared as the key feature to confer both antioxidant and cytoprotective activity to the structure. Antioxidant activity seems essential for cytoprotection, but it is not sufficient, and there is no statistically significant correlation between the two types of activity. 

The three carbon atoms and one nitrogen atom of the nucleus contribute four 7r-electrons, and the nitrogen atom in position 1, which is not involved in double bond formation, donates its electron pair, thus creating an aromatic sextet of 77-electrons. At the same time the 1-position nitrogen loses its basic properties, although the nitrogen atom in position 2 remains weakly basic. 

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