Gluconic acid, crystalline

A methoxylated polyamide 78 analogous to Nylon 6 was obtained in several steps fi om D-glucose [61, 63] through the preparation of a dimeric active ester of 6-amino-6-deoxy-2,3,4,5-tetra-(9-methyl-D-gluconic acid (49). This polyamide was highly crystalline, and gave resistant films with a spherulitic texture. 

The preferred method of preparing 74 for laboratory use is by the dehydration of D-xt/lo-5-hexulosonic ( 5-keto-D-gluconic ) acid in refluxing, 5% methanolic hydrogen chloride the crystalline, methyl ester of 74 can then be isolated in 17.4% yield.110 Crystalline 74 is readily prepared from the methyl ester by saponification. Pure 74 has m.p. 200-201° and kmaX = 286 nm (e = 18,000) in water. 

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. 

Chain-extension reactions constitute a more widely used approach. Thus, the cyanohydrin synthesis followed by base-catalyzed cyclization and /1-elimination to iminolactones, which then undergo stepwise hydrolysis, affords 3-deoxy-2-glyculosonic acids.313 The overall yield of this reaction is low. Paerels314 used this method to prepare the first crystalline members of this group, namely 3-deoxy-D-m //iro-hex-2-ulosopyranosonic acid (2-keto-3-deoxy-D-gluconic acid, KDG, 119), and the L isomer, starting from D-ribose and L-arabinose, respectively. The synthesis of 119 is illustrated in Scheme 10. 

The trimethyl-D-glucose proved instead to be 2,3,5-trimethyl-D-glucose, which had been synthesized by Smith.14 It was characterized as the crystalline phenylhydrazide of the corresponding trimethyl-D-gluconic acid, the derivative being identical with an authentic sample of 2,3,5-trimethyl-D-gluconic acid phenylhydrazide prepared by Smith.14... 

Tiemann studied the further oxidation of D-gluconic acid with bromine at 100 a reducing sirup was formed which was isolated as an amorphous barium salt or a crystalline osazone. Ruff repeated the work and could find no oxygluconic acid in the oxidation mixture most of the D-gluconic acid was unaltered and the reducing power was very low, especially in comparison with that obtained when keto aldonic acids were prepared by the action of hydrogen peroxide and ferrous salts. By ether extraction and distillation the formation of formic, oxalic and glycolic acids was shown. 

The structure of the second di-O-isopropyl idene-D-fructose has been defined (181). It is known that carbon 1 in this isomer is open since, on oxidation with alkaline permanganate, an acid was obtained, without acetone removal, which on acid hydrolysis yielded 1-C-carboxy-D-arabinose (2-keto-D-gluconic acid) (182). Acid hydrolysis yielded a mono-O-isopropylidene-D-fructose characterized as a crystalline triacetate. Deacetylation of this nonreducing compound yielded a product consuming one mole of periodate per mole of substance. Only two possible nonreducing mono-O-isopropyli-dene derivatives are compatible with this analysis 1,2-0-isopropylidene-D-fructofuranose and 2,3-0-isopropylidene-D-fructopyranose. The former is eliminated by the formation of a carboxyl group at carbon 1. Since hydrolysis by aqueous acid will not shift the position of an attached isopropylidene group, the structure of this mono-O-isopropylidene-D-fructose is therefore established as 2,3-0-isopropylidene-D-fructopyranose and the second diiso-propylidene derivative is established as 2,3 4,5-di-0-isopropylidene-D-fructose (II). 

A convenient and high-yielding method for the synthesis of crystalline sodium D-arabinonate involves oxidation of D-glucose with oxygen in alkaline methanol-water mixtures. Conditions have been optimised for the catalytic hydrogenation of D-Jcy/o-5-hexulosonic acid so as to give a 3 1 preponderance of L-idonic acid over D-gluconic acid in a very efficient reaction. ... 

An investigation of the structure of threitol, which includes n.nLr. studies, is referred to in Charter 22 (section 3.9). The (/2)-stereocheniistry at C-5 of the 7-deoxy-4-heptulose 2, obtained in an enzyme-catalysed aldol condensation (see Chapter 2) has been ascertained by extensive n.nu . experiments, especially n.O.e. studies." The stmaural properties of the alkali metal salts of D-gluconic acid in the crystalline state and in solution have been examined by F.t.i.r. and "C-n.mjr. spectroscopy."... 

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