Metasaccharinic acids

The saccharinic acids formed from hexoses have been especially examined because of the relationships of the a and /8 isomers (C-2 epi-mers). Structures of saccharinic acids derived from D-glucose are glu-cometasaccharinic acid (51), glucoisosaccharinic acid (52), and glucosaccharinic acid (53). The a- and /3- isomers of metasaccharinic acid can reversibly isomerize when exposed to base because of the labile proton at C-2. 

All of the 4-carbon saccharinic acids possible have been prepared and characterized.132 The 4-carbon metasaccharinic acid has been encountered frequently,1,133-137 and a racemic mixture of the 2-methyl-glyceric acids (2,3-dihydroxy-2-methylpropanoic acids) was obtained from 4-O-methyl-D-threose.136... 

The 3-deoxyaldonic acids (metasaccharinic acids) arise by alkaline treatment of monosaccharides, especially those substituted at C-3.288 They have also been obtained from (1 - 3)-linked oligo- and polysaccharides. The most common ones are 3-deoxy-D-n Z>o-hexonic acid (a-D-glucometasaccharinic acid, 109) and 3-deoxy-o-arabino-hexonic acid (jS-D-glucometasaccharinic acid, 110), which can most conveniently be... 

The metasaccharinic acids produced by the action of lime water on D-glucose may be used for this synthesis without isolation. Both the 5-phosphates and the 6-phosphates of mixtures of 109 and 110 have been prepared.292... 

The 3-deoxyosone (1 ), is thought to be a precursor of "metasaccharinic acid" in basic solution and of... 

Fig. 7 -31. Peeling and stopping reactions of polysaccharides (Sjostrom, 1977). R = polysaccharide chain and R = CH2OH (cellulose and glucomannans) or H (xylan). Cellulose and glucomannans (R = CH2OH) (1) 3-Deoxyhexonic acid end groups (metasaccharinic acid), (2) 2-C-methylglyceric acid end groups, (3) 3-deoxy-2-C-hydroxymethylpentonic acid (glucoisosaccharinic acid), (4) 2-hydroxypropanoic acid (lactic acid), and (5) 3,4-dideoxypentonic acid (2,5-dihydroxypentanoic acid). Xylan (R = H) (3) 3-Deoxy-2-C-hydroxymethyltetronic acid (xyloisosaccharinic acid), (4) 2-hydroxypropanoic acid (lactic acid), and (5) 2-hydroxybutanoic acid. 1977. TAPPI. Reprinted from Tappi 60(9), p. 152, with permission.

Machell and Richards and Colbran and Davidson. . . assumed that degradation ceased not only when the reducing terminal unit of cellulose was converted into a metasaccharinic acid residue but also when the reactant end of the molecule reached inaccessible (crystalline) regions of the cellulose fiber... . The available data indicate that the less ordered portions of cellulose are the more reactive. Thus the rate of oxidation of... 

Dianhydro-i)-mannitol, amygdalin a-n-Galacto-metasaccharinic acid 3-Hydroxypropyl 8-D-glucopyraiioside L-Fucose... 

Posternak employed permanganate oxidation of quercitol and obtained the conclusive derivative, metasaccharinic acid, which from data already published, he showed to have the configuration XLVIII. From this it may be seen that formula XLIV represents dea [Pg.67]

Three structurally isomeric forms have been established for the six-carbon saccharinic acids. In the order of their discovery, these are the sac-charinic or 2-C -methylpentonic acids, the isosaccharinic or 3-deoxy-2-C -(hydroxymethyl)-pentonic acids, and the metasaccharinic or 3-deoxy-hexonic acids. Although none of these six-carbon, deoxyaldonic acids has been crystallized, six are known in the form of crystalline lactones (saccharins). All the possible metasaccharinic acids of less than six-carbon content have been obtained, in the form of crystalline derivatives, by the sugar-alkali reaction. Only one example of a branched-chain deoxyaldonic acid (the racemic, five-carbon isosaccharinic acid) of other than six-carbon content has been so obtained. The formation of saccharinic acids containing more than six carbon atoms remains to be explored. 

Only the racemic form of this acid is obtained from the sugar-alkali reaction. As in the formation of lactic acid, a non-asymmetric enediol is an intermediate in its production (see Section III), and hence the racemate is the sole representative of the four-carbon metasaccharinic acid class. 

These four acids comprise all the possible five-carbon metasaccharinic acids and all were obtained by Nef, in the form of crystalline derivatives, from the pentose-alkali reaction. 

Kiliani and Sanda s directions for the preparation of a -D-galacto-metasaccharinic acid follow. 

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