1911 Encyclopædia Britannica/Asparagine

ASPARAGINE, C₄H₈N₂O₃, a naturally occurring base, found in plants belonging to the natural orders Leguminosae and Cruciferae. It occurs in two optically active forms, namely, as laevo-asparagine and dextro-asparagine. Laevo-asparagine was isolated in 1805 by L. N. Vauquelin. A. Piutti (Gazz. chim. Ital., 1887, 17, p. 126; 1888, 18, p. 457) synthesized the asparagines from the monomethyl ester of inactive aspartic acid by heating it with alcoholic ammonia. In this way a mixture of the two asparagines was obtained, which were separated by picking out the hemihedral crystals.

HOOC·CH·NH₂·CH₂·COOC₂H₅ + NH₃＝C₂H₅OH + HOOC·CH·NH₂·CH₂·CONH₂.

Laevo-asparagine is slightly soluble in cold water and readily soluble in hot water. It crystallizes in prisms, containing one molecule of water of crystallization, the anhydrous form melting at 234–235° C. Nitrous acid converts it into malic acid, HOOC·CHOH·CH₂·COOH. It is laevo-rotatory in aqueous or in alkaline solution, and dextro-rotatory in acid solution (L. Pasteur, Ann. Chim. Phys., 1851 [2], 31, p. 67). Dextro-asparagine was first found in 1886 in the shoots of the vetch (Piutti). It forms rhombic crystals possessing a sweet taste. It is dextro-rotatory in aqueous or alkaline solution, and laevo-rotatory in acid solution.

Hydrolysis by means of acids or alkalis converts the asparagines into aspartic acid; whilst on heating with water in a sealed tube they are converted into ammonium aspartate. The constitution of the asparagines has been determined by A. Piutti (Gazz. chim. Ital., 1888, 18, p. 457).