GLYOXALINES owe their interest to the fact that they are degradation products of certain alkaloids (q.v.), and that a member of the group arises from the decomposition of sugars such as glucose with ammonia. They are organic compounds of carbon, hydrogen and nitrogen, and contain the ring system shown in I. They are also called iminazoles.
The glyoxalines are generally colourless, crystalline bases, and can be produced synthetically by the condensation of glyoxal and similar ortlio-diketones with ammonia and aldehydes.
Glyoxaline itself (formula I.) is obtained by condensing to gether glyoxal, ammonia and formaldehyde; it melts at 9o° C. and boils at 263° C, 4(or 5)-Methylglyoxaline (formula II.) is formed by the action of zinc hydroxide and ammonia on grape sugar (glucose) and other hexoses and pentoses. The methylation of 4-methylglyoxaline with dimethyl sulphate and alkali gives rise simultaneously to 1:4- and 1:5-dimethylglyoxalines indicating that methylglyoxaline behaves during methylation as a tautomeric substance (see IsoMERIsM).
Glyoxaline has a marked physiological activity—substitution of methyl for hydrogen in the imino-group increases the toxic action. The pilocarpine alkaloids, which contain the glyoxaline or iminazole nucleus and yield glyoxaline derivatives on distilla tion with soda lime, are substances of therapeutic interest (see