NEW MATERIAL: 5,6-Sulfinyl-L-ascorbic acid expressed by the formula.

USE: An anti-oxidizing agent for wine, feed, a material for producing and developing a film, a printing material, plastic and rubber.

PROCESS: Ascorbic acid or a corresponding stereoisomer is sulfinylized. In the sulfinylization, an equal mol amount of thionyl chloride is used as a sulfinylizing agent and the reaction is executed at -10 to 25°C preferably. Moreover, the reaction is executed preferably in the presence of an inert solvent, especially a polar non-protonic solvent, for example tetrahydrofuran, etc.