Kojic acid chemical synthesis

Kojic acid, 5-hydroxy-2-(hydroxymethyl)-4//-pyran-4-one1 (II), is produced from carbohydrate sources in an aerobic process by a variety of microorganisms. The acid was discovered in 1907, its structure was established in 1924, and its chemical synthesis from D-glucose was achieved in 1930. Since then, a considerable amount of study has been devoted to the biosynthesis of kojic acid, and numerous publications have dealt with its chemical and biological properties. After nearly half a century, kojic acid remains a scientists curiosity, without industrial importance. It con-... 

The starting materials for the chemical synthesis of kojic acid are also carbohydrates, but only hexoses and their derivatives have been used for this purpose. Maurer and his coworkers studied the synthesis extensively in order to clarify the mode of formation of the 7-pyrone system from carbohydrates. They succeeded in preparing di-O-acetylkojic acid (XLIII) by purely chemical means, first from D-glucose54 and then from D-galac-tose.67 The mechanism of formation of XLIII, which does not contain any asymmetric carbon atoms, was apparently not dependent on the configura-... 

The first successful synthesis of maltol started from pyromeconic acid, which itself was an expensive material, and gave maltol in low yields. Today, industrial production is carried out by fermentation (kojic acid produced by an Aspergillus fungus) combined with chemical synthesis [10,20]. The synthetic routes include oxidation of kojic acid and addition of formaldehyde. By substituting acetaldehyde for formaldehyde, ethyl maltol (Fig. 3.60) is produced [20]. 

A companion volume has been published which brings up to date an important treatise on flavonoids. The final part of a comprehensive review of pyrylium salts provides full documentation of this field which has also been reviewed in Russian. The synthesis and reactions of kojic acid have been reviewed as also (in Japanese) have those of 1,4-dithiins. The proceedings of the 6th International Symposium on Flavonoids and Bioflavonoids (1981) have been published and contain both reviews and shorter original contributions. Amongst the former are reviews on such topics as the reactions of chromones with hydroxylamine, the synthesis and reactions of 3-acylchromones, chemical and biomimetic studies on condensed... 

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