Erythraric acid

To the names of aldaric acids that are symmetrical, which therefore have no D- or L- prefix, the prefix meso- may be added for the sake of clarity. Examples mero-erythraric acid, meso-ribaric acid, meso-xylaric acid, meso-allaric acid, meso-galactaric acid. 

DL-galactonic acid (39). 1,4-Anhydro-DL-talitol (3,6-anhydro-DL-altritol) (40) gave 2-0-(carboxymethyl)-DL-threaric acid (41) and 1,4-anhydro-D-mannitol (42) gave 2-0-(carboxymethyl)erythraric acid (43). 

Some interest also attaches, on stereochemical grounds, to the effects of the isomers of tartaric acid and malic acid. At 0.01 M, erythraric acid (meso-tartaric acid) caused slight competitive inhibition,181 183 186 whilst d- or L-threaric acid (levo- or dextro-tartaric acid) had no effect138181 commercial DL-threaric acid ( racemic acid ) had a small effect that disappeared on purification.181 Some authors have noted slight inhibition with L-tartaric acid.147 166 183 L-Malic acid resembled erythraric acid in its action,136 147 1 65 188,185 but n-malic acid appeared to be non-inhibitory.136-183 Unsubstituted w-dicarboxylic acids cause little, if any, inhibition.135 147 166183... 

The term aric is used with the normal configurational prefix the tartaric acids are threaric or erythraric acids, mucic acid is galactaric acid, and -saccharic acid is glucaric acid. The name xylaric acid is much shorter than xylo-trihy-droxyglutaric acid. For an additional discussion see below and Chapter I, particularly p. 28. In the present text both forms are used, but the new usage is preferred. 

Tartaric (2,3-dihydroxysuccinic) acid is an important representative of dihydroxydicarboxylic (aldaric) acids and the most prominent acid in wine. In nature it occurs almost exclusively as (-l-)-L-tartaric acid (8-66), also known as dextrotartaric acid or L-threaric acid, which is (2J ,3J )-isomer. Occasionally tartaric acid occurs as (-)-tartaric, laevotartaric acid, which is the (2S,3S)-isomer, also known as D-threaric acid (8-66). An optically inactive racemic mixture of both isomers, called racemic (uvic) acid, has been demonstrated in grape juice, the optically active symmetric (2J ,3S)-tartaric acid (8-66) called meso-tartaric or erythraric acid does not occur in nature. Synthetic racemic and meso-tartaric acids are used as acidulants. 

There are two naturally occurring aldotetroses, D-erythrose and o-threose (16.49 and 16.50), and one ketotetrose, o-erythrulose (16.51). Erythrose and threose can be distinguished by nitric acid oxidation (notice the less usual but water-soluble oxidant, selective for the aldehyde and primary alcohol over the secondary alcohols) threose leads to a chiral diacid, while the diacid from erythrose is a meso-compound and achiral. Although, in a formal nomenclature sense, these diacids would be threaric acid and erythraric acid, they always go by their more common name of tartaric acid. 

---