Tartaric acid from glyoxal

German name, Trauben-saure, is derived from the word for grapes. It is probable that it does not exist in grapes as racemic acid but that it is formed from the dextro acid as this transformation can easily be effected by the action of acids or even by water alone. When tartaric acid is prepared synthetically from succinic acid, from glyoxal, or from malic, maleic or fumaric acids either racemic acid or meso-tartaric acid is always formed. That is, synthetic reactions result in the formation of an inactive form. The methods of splitting racemic acid into its optically active components has been fully discussed. The sodium-ammonium racemate is the only salt that is of importance. This has been spoken of in connection with the method of splitting racemic acid into its components.. Like the free acid this salt exists, in dilute solution, as equal molecular parts of the dextro and levo forms. Only in concentrated solution does it exist as the racemate itself. 

Such an acid as this ketone acid is known and is called oxal acetic acid, and tartaric acid does not yield this acid on heating nor does it show any properties of a ketone acid. We, thus, have no evidence that tartaric acid is the unsymmetrical di-hydroxy succinic acid. That tartaric acid is, in fact, the symmetrical di-hydroxy succinic acid is proven by its synthesis from glyoxal, and also by its synthesis from succinic acid itself. 

Synthesis from Glyoxal.—Glyoxal, being a di-aldehyde, (p. 261), forms a di-addition product with hydrogen cyanide, HCN, and this di-cyanide addition product hydrolyzes and yields tartaric acid. The reaction may be expressed as follows,... 

Chiral boron complexes derived from tartaric acid derivatives and from P-aminoalcohols act as mild Lewis acids and asymmetric catalysts for the reaction of aldehydes (94T979) and methyl glyoxalate (94CC1563) with Danishefsky dienes. The resulting 2,3-dihydropyran-4-ones are obtained in high optic purity. 

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