PURPOSE: To facilitate the separation and the purification of a lactone which is an intermediate of L-ascorbic acid useful as a food additive, by oxidizing an easily available, low-cost glucofuranose in an organic solvent in the presence of a specific metal catalyst.
CONSTITUTION: A lactone of formula II is prepared by oxidizing a glucofuranose of formula I with O2 or O2-contaning gas, in an organic solvent such as ethers, amides, etc., in the presence of Pd metal and a metal or its compound selected from Pb, Tl and Hg. After the reaction, the catalyst is removed by filtration, a part of the solvent is distilled away, and the residue is concentrated to obtain the objective lactone in high purity. The amount of Pd is 0.001W1mol per 1mol of the starting compound, and the atomic ratio of Pd to the other metal is 1 to 0.01W30. The compound I can be easily prepared from glucose and acetone.
FUKUOKA YOUHEI
TAMURA WATAHIKO
