Quinolinium ring system

Other Radioprotective Chemicals. The bis-methylthio- and methylthioamino-derivatives of 1-methylquinolinium iodide and l-methylpyridinium-2-dithioacetic acid provide reasonable protection to mice at much lower doses than the aminothiols, which suggests a different mechanism of action (139). One of these compounds, the 2-(methylthio)-2-piperidino derivative of the l-methyl-2-vinyl quinolinium iodide (VQ), interacts with supercoUed plasmic DNA primarily by intercalation. Minor substitutions on the aromatic quinolinium ring system markedly influence this interaction. Like WR-1065, VQ is positively charged at physiological pH, and the DNA-binding affinities of VQ and WR-1065 appear to be similar. 

Dequalinium salts can be purchased from Sigma Chemical Co., St. Louis, Missouri, U.S.A. Analogues of dequalinium, however, are not commercially available they can be synthesized according to protocols by Galanakis et al. (44 6). In a structure-activity relationship study (38), we found that the methyl group in ortho position to the quaternary nitrogen at the quinolinium ring system seems to play an essential role in the... 

The oxoaporphine alkaloids Teliglazine (126), Corunnine (127), Nandazurine (128), PO-3 (129), A-Methylliriodendronine (130), and A,(9-Dimethylliriodendronine (131) contain the 6-methyl-7-oxo-dibenzo [Je,g]quinolinium-l-olate ring system 125 which is isoconjugate with the l-methyl-7-methylene-7H-benzo[Je]anthracene anion (Scheme 46). Therefore, these alkaloids belong to class 1, i.e., heterocyclic mesomeric betaines isoconjugate with odd alternant hydrocarbon anions. Another... 

Other fused ring systems in which C-protonation in the five-membered ring leads to pyridinium or quinolinium aromatic rings, respectively, are 2-phenyl-2-pyrindine (Anderson and Harrison, 1964) and 3-acyl-l,2-dihydro-4H-j3-quinindines (Kholodov et al., 1969). 

Protonation of the nitrogen atoms in azine ring systems results in an appreciable increase in the screening of the nitrogen nucleus, (Id) according to the general trend in the shifts produced upon coordination of the lone electron pair in an unsaturated system. Some accurate data have recently been reported for the pyridinium [48b] and quinolinium... 

Attempts to achieve the thermal ring closure of the Meerwein salt 137 to the benzo[c]phenanthridine system failed the major product was the 4-acyliso-quinolinium salt 138 (79T1861). The reaction between )V-benzylaminoacetal-dehyde dialkyl acetals (139) with methyl vinyl ketone in acidic solution, leading to benzo[h]quinolizine derivatives, was newly investigated. The... 

The properties of pyrylium cations are best compared with those of pyridinium cations the system does not undergo electrophilic substitution nor, indeed, are benzopyrylium cations substituted in the benzene ring. This is a considerable contrast with the chemistry of quinolinium and isoquinolinium cations and is a comment on the stronger deactivating effect of the positively charged oxygen. 

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