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Chosen biweekly by Rachel Grabenhofer, editor of Cosmetics & Toiletries magazine, for their relevance to personal care, Patent Picks are taken from publicly available sources.This special edition features a varietal "cornucopia" of recently issued patents relevant to cosmetic product development.
Method for preparing crystalline 3-0-alkyl-ascorbic acid
US Patent 7838690
Publication date: Nov. 23, 2010
Assignee: Cosmol Co. Ltd (Kyeongki-do, Korea)
The present invention relates to a method for preparing 3-O-substituted ascorbic acid derivatives represented in which 5,6-O-isopropylidene ascorbic acid is reacted with a halide in an organic solvent in the presence of the anion exchange resin absorbed with multi-iodine anions and then deprotected. This method is proven beneficial in that it provides a target compound with high purity and high yield by finishing the reaction within a short period of time at room temperature.
According to this patent, L-ascorbic acid is a bioactive material with strong antioxidative activity that has been used as a medicine for treating scurvy and applied in cosmetics owing to its wide physiological activities including inhibiting the accumulation of melanic pigments, a known cause of chloasma or freckles. In addition, owing to its effects of increasing collagen bio-synthesis and stimulating fibroblast growth, L-ascorbic acid has been used to prevent browning of food, preserve incense and maintain freshness. However, ascorbic acid is easily oxidized by heat, light and oxygen in the air to lose its activity and is insoluble in oil, so that it has been limited in use.
To improve stability of the ascorbic acid, numbers of ascorbic acid derivatives have been developed. However, with one derivative, the substitution of the third hydroxyl group of the ascorbic acid with alkyl is limited and the generation of by-products is a problem. And in another derivative, the use of a strong polar solvent results in the decrease of yield. The object of the present invention was to solve the problems of these conventional methods for preparing ascorbic acids.