Mannonic acids preparation

Watters, Hockett and Hudson1 have prepared a non-crystalline monomethylmannose which forms an osazone with the same properties as those of 6-methyl-n-glucosazone. The synthesis was achieved by methylation of methyl 2,3,4-triacetyl-a-D-mannopyranoside, followed by hydrolysis. Schmidt and Heiss,13 studying the epimerization of 6-methyl-D-gluconic acid, have claimed to have isolated the phenyl-hydrazide of 6-methyl-n-mannonic acid. 

D-Mannonic acid was prepared by Fischer and Hirschberger since the calcium, barium and cadmium salts were all amorphous, the crystalline phenylhydrazide was isolated. Hydrolysis with barium hydroxide followed by removal of the phenylhydrazine with ether and the barium with sulfuric acid gave the crystalline lactone. The phenylhydrazide could also be obtained (15% yield) by the oxidation of hydrolyzed ivory-nut meal. D,L-Mannose was converted by Fischer to D,L-mannonic acid and isolated as the phenylhydrazide. 

A solution of D-mannose (100 g) in water (21) was treated with calcium bromide (17.7 g) and calcium carbonate (55 g) and electrolysed, with stirring, in a suitable cylinder. Carbon electrodes, of 12 mm diameter, were placed about 8 cm apart the current density was 0.5 to 0.7 amp. After 50-55 hours the reducing power of the solution was negligible, so the solution was filtered, evaporated as far as possible, and left to solidify. The gelatinous mass was powdered and dried. The original papers should be consulted for preparation of crystalline calcium mannonate. To obtain the lactone of D-mannonic acid one part of the calcium salt is dissolved in 3 parts of water on the water-bath, an excess of oxalic acid is slowly added, the precipitated calcium oxalate is filtered off, and the filtrate is concentrated until its weight equals that of the calcium salt used this material is then left to crystallize. 

Aldonic acids are made on a preparative scale by oxidation of aldoses with bromine in buffered aqueous solution (pH = 5-6). For example, o-mannose yields D-mannonic acid in this way. Upon subsequent evaporation of solvent from the aqueous solution of the aldonic acid, the y-lactone (Section 20-4) forms spontaneously. 

Bierenstiel and Schlaf [22] were able to prepare and isolate for the first time the less stable 8-D-galactonolactone by oxidation of galactose with the Schvo s catalytic system, which is based on the dimeric ruthenium complex [(C4Pli4CO)(CO)2Ru]2. The transformation led to the 5-galactonolactone in 93% yield, against 7% of the isolated y-lactone isomer. This procedure also allowed the preparation of 5-D-man-nonolactone in a much better yield (94%) than that reported in an early procedure [23] based on crystallization from a solution of calcium mannonate in aqueous oxahc acid. 

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... 

Esters of aldonic acids are prepared from 6-lactones, slowly from 7-lac-tones, by reaction with alcohols in the presence of hydrogen chloride or of the free aldonic acid (26). The acids may be recrystallized from boiling methanol without much esterification taking place (27). At the melting point, ethyl mannonate is converted to the 7-lactone with the loss of ethyl alcohol. 

---