Acyclic Ureides

The acyl derivatives of urea are called as ureides which include barbiturates an substitution products of pyrimidine and purine. The amino groups of urea may be acylated by monobasic or polybasic acids to yield either acyclic or cyclic ureides. An acyclic monoureide has the structure R-CO-NH-CONH; an acyclic diureide is R-CO-NH-CO-NH-COR. In all ureides at least one of the nitrogen atoms is joined by two carbonyl groups (-NHCO-NH) which will form a water-soluble salt in the presence of alkali hydroxide. In general ureides are neutral compounds.

The acyclic ureides are prepared from the corresponding alkyl or dialkylmalonic acid. Acetic acid is formed by decarboxylation. The acid halides of these or their α-halo derivatives are condensed with urea to form the desired ureides.

Ureides are hydrolyzed by hot, dilute alkalis with formation of hydrolysis products of urea and a salt of the particular acid.

The acyclic ureides possess weak depressant activity. Relatively high doses are required to produce hypnosis. They are mainly used as sedative in the treatment of simple anxiety and nervous tension.

Bromisovalum and ectylurea are the acyclic ureides.

Amidés and imides

Glutethimide, methyprylon and methaqualone are the cyclic amides and imides effective as sedative and hypnotic drugs.

Alcohol and their Carbamates

Ethanol is a prominent compound used as sedative and hypnotic. The hypnotic activity of the normal alcohols increases as the molecular weight and lipid solubility increase. Branching of the alkyl chain increases activity. Substitution of a hydrogen by a halogen also increases the action..

Amylene hydrate, chlorobutanol, ethchlorvynol, meparfynol and ethinamate are some alcohols used as hypnotic drugs.