Structure-activity relationships in reactivators of organophosphorus-inhibited acetylcholinesterase. V. Quaternary salts of hydroxyiminomethylimidazoles.
The methiodides of (E)-1-methyl-2-hydroxyiminomethylimidazole, (E)-1-benzyl-2-hydroxyiminomethylimidazole, and (Z)-1-methyl-5-hydroxyiminomethylimidazole were tested in vitro as reactivators of phosphorylated acetylcholinesterase. From the hydrolysis rate measurements, it was ascertained that only the compounds derived from 2-hydroxyiminomethylimidazole had an activity comparable with that of methiodide of 2-hydroxyiminomethylpyridine, whereas the methiodide of (Z)-1-methyl-5-hydroxyiminomethylimidazole was inactive. The structure-activity relationships of these reactivators are briefly discussed.
Reactivators of Inhibited Acetylcholinesterase. I. the Preparation and Properties of 4‐Hydroxyminomethyl‐1‐Methylpyrimidinium Iodide
4-Hydroximinomethyl-pyrimidine (VIII) has been prepared from 4-methylpyrimidine (III) by nitrosation or, more preferably, by the Ortoleva-King procedure. The oxime VIII has a syn configuration and yields, upon alkylation with iodomethane, 4-hydroximinomethyl-1-methyl-pyrimidinium iodide (IX). The latter proved to be a reactivator of phosphorylated acetylcholine esterase in vitro. In combination with low doses of atropine it also protected mice against organophosphate intoxication.
Syntheses Using Pyridinium Salts (IV)
Cleavage of N-phenylpyridinium or N-vinylpyridinium salts with secondary aliphatic amines leads to aromatic amino compounds or enamines which are often unobtainable by other routes. The other fragment, glutacondialdehyde or its monoanil, gives azulenes, as shown by Ziegler and Hafner, as well as Konig; these compounds can also be prepared from alkylpyridinium salts with cyclopentadienylsodium (Hafner). Syntheses of labile aldehydes which are otherwise difficult to obtain and of α-ketocarboxylic acids, starting from pyridinium salts and proceeding via nitrones or α-cyanoanils, are illustrated by many new examples. Benzimidazoles, benzothiazoles, and amidines are accessible from pyridinium salts via nitrones or α-cyanoanils; cyanoanils can be transformed into quinoxalines (including xanthopterine), perimidines, etc. Furthermore, nitrosonaphthols and nitrosonaphthylamines react with pyridinium salts containing an active methylene group on the nitrogen, leading to new ring systems. Further synthetic possibilities arise from nucleophilic displacements of the pyridine in pyridinium salts by SN 2 reactions. Combination of the route via nitrones with the methods of Arndt-Eistert, Ortoleva-King, or with chloromethylation constitutes a significant enlargement of its range of application. The formation of α-cyanoanils from diazoketones permits synthesis of α-keto-β-amino acids from α-amino acids, or of phenylglyoxylic acids from benzoic acids by chain extension.