NEW MATERIAL:The compound of formula (M is potassium or sodium).

USE: Antidote.

PROCESS: For example, L-cysteine, D-glucuronolactone and sodium bicarbonate are dissolved in water, and the reaction occurs evolving carbon dioxide gas. The reaction mixture is left at room temperature for 30W40min with occasional shaking to precipitate colorless acicular crystals. Methyl alcohol is added to the mixture to complete the precipitation of the crystal, and the crystals are separated by filtration. The separated crystals are purified by recrystallization from a water-methyl alcohol mixture to obtain the compound of formula. The objective compound can also be prepared by neutralizing cysteine-glucuronolactone with equimolar amount of sodium hydroxide, etc. in a solvent such as water, aqueous alcohol, etc.