Ketamine is a specific drug for noninhalation narcosis that is used in brief surgical procedures. It causes a condition known as dissociative anesthesia, which ensures amnesia and analgesia, and preserves normal respiration and muscle tonicity in the patient. Ketamine is practically void of muscle relaxant capabilities.
Preanesthetic medications such as morphine, scopolamine, benzodiazepine, and buty-rophenones lower dysphoric effects of ketamine. Synonyms for this drug are ketanest, ketalar, and others.
Etomidate: Etomidate, ethyl ester of 1-(a-methylbenzyl)imidazole-5-carboxylic acid (1.2.8), is prepared by the following procedure. It illustrates a special case of obtaining derivatives of imidazole by interaction of a-aminocarbonyl compounds with thiocyanates. The reaction of a-methylbenzylamine with ethyl chloroacetate gives N-ethoxycarbonylmethyl-N-1-phenylethylamine (1.2.5), which undergoes further formylation by formic acid. The resulting N-ethoxycarbonylmethyl-N-formyl-N-1-phenylethylamine (1.2.6) undergoes further C-formylation by ethylformate in the presence of sodium ethoxide. The product is further processed (without being isolated) by a solution of potassium thiocyanate in hydrochloric acid. As a result of the reaction of thiocyanate ions with the amino group which occurs as a result of acidic hydrolysis of the N-formamide protecting group and further interaction of the obtained intermediate with the newly inserted aldehyde group, a Marckwald reaction type heterocyclization takes place, resulting in formation of 5-ethoxycarbonyl-2-mercapto-1-(1-phenylethyl)imidazole (1.2.7). Finally, the thiol group is removed by oxidative dethionation upon interaction with a mixture of nitric and nitrous acids (nitric acid in the presence of sodium nitrite), which evidently occurs through formation of unstable sulfinic acid, which easily loses sulfur dioxide resulting the desired etomidate [14,15].
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