Calcium D-galactonate

Calcium D-galactonate, I, 70 Calcium D-gluconate, III, 141, 142, 149, 152, 155, 156, 161 IV, 331 Calcium hypochlorite, III, 165 Calcium 2-keto-D-gIuconate, III, 148, 155 Calcium 5-keto-D-gluconate, III, 156 Calcium lactobionate, calcium bromide double salt, III, 155 Calcium Ievulinate, IV, 311 Calcium maltobionate, III, 161 Calcium D-mannonate, III, 152 Calcium pectate, I, 334 Calcium D-rhamnonate, III, 144 Calcium salts, in preparation of aldonic acids with NaCN, I, 23 Calcium vicianobionate, III, 154 Calcium D-xylonate, III, 155 Camphor, optically active, formed from inactive (racemic) camphor carboxylic acid in the presence of quinine, quinidine or nicotine, V, 53 Camphor carboxylic acid. See Camphor. Camphor, 3-hydroxy-, IV, 89 Camphorquinone, phytochemical reduction of, IV, 89... 

The first attempt to maintain a low acidity was carried out by Clowes and Tollens in 1899. A mixture of D-galactose, water and calcium carbonate was shaken with an excess of bromine for twelve to twenty-four hours. Carbon dioxide was evolved and the solution was concentrated at 100°. A thin sirup was obtained, from which calcium D-galactonate crystallized upon the addition of ethanol. The same procedure was... 

Kiliani reported very favorably on the electrolytic method and was quick to apply it to the preparation of calcium D-galactonate. In 1935, the electrolytic preparation of calcium D-xylonate was reported by Isbell and Frush the earlier work had been delayed by failure to obtain the salt in crystalline condition. The preparation of calcium lactobionate-calcium bromide was reported by Isbell the double salt was suggested as a sedative in place of calcium bromide. 

Ruff applied the reaction to the easily available salts of the aldonic acids and showed that the oxidation takes place by the cleavage of carbon-carbon bonds and the direct formation of sugars. The yields are modest, but the sugars usually crystallize readily. n-Arabinose is produced from calcium D-gluconate in 50% of the theoretical quantity. The use of ion-exchange resins to remove ionic materials from the reaction mixture prior to isolation of the sugar is beneficial. By this technique, the yield of D-lyxose from calcium D-galactonate is increased from 17 to 41 % 186), Salts other than the... 

In most cases, after the hydrogen bromide had been removed, the resulting solutions were treated with various carbonates or with ammonium hydroxide to form the desired salts. The salts could be recrystallized directly from water or precipitated into ethanol. The choice of salt depended on circumstances thus, calcium D-gluconate crystallized well, but in the case of n-galactonic acid, the cadmium salt was preferable. The lead or cadmium salt was preferred when the free acid was desired since treatment of the aqueous solution or suspension with hydrogen sulfide easily removed the cation. The barium salts could be treated with the calculated amount of sulfuric acid and the calcium salts with oxalic acid for the same purpose. 

Ruff reduced the amount of bromine in the preparation of larger amounts of the aldonic acids, so that one part of bromine was used with one part of sugar. A yield of 75 g. of calcium D-gluconate was obtained from 100 g. of D-glucose and 49.5 g. of cadmium D-galactonate from 100 g. of lactose. 

It is interesting that, when 14 was treated with calcium hydroxide, D-arabtno-5-hexulosonic acid (125) was formed in good yield.580,581 By a similar procedure, D-glucuronic acid (54) was converted in 60-70% yield into D-/yxo-5-hexulosonic acid (126).582,583 Stereoselective reduction of 125 or 126, could, potentially, afford L-galactonic acid or L-gu-lonic acid, respectively, which could then be converted into 1. 

Another method of preparing keto aldonic acids, those of the 2-keto type, is by oxidation of the corresponding osone. Neuberg and Kitasato obtained 18 g. of calcium 2-keto-D-gluconate from 20 g. of the osone by the action of bromine at 20 . Similarly, 2-keto-n-galactonic and 2-keto-maltobionic acids were prepared by Kitasato. The substances were characterized generally as the brucine salts because of the amorphous nature of the calcium salts. 

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