Glucitol oxidation

A series of sorbitol-based nonionic surfactants are used ia foods as water-ia-oil emulsifiers and defoamers. They are produced by reaction of fatty acids with sorbitol. During reaction, cycHc dehydration as well as esterification (primary hydroxyl group) occurs so that the hydrophilic portion is not only sorbitol but also its mono- and dianhydride. The product known as sorbitan monostearate [1338-41 -6] for example, is a mixture of partial stearic and palmitic acid esters (sorbitan monopalmitate [26266-57-9]) of sorbitol, 1,5-anhydro-D-glucitol [154-58-8] 1,4-sorbitan [27299-12-3] and isosorbide [652-67-5]. Sorbitan esters, such as the foregoing and also sorbitan monolaurate [1338-39-2] and sorbitan monooleate [1338-43-8], can be further modified by reaction with ethylene oxide to produce ethoxylated sorbitan esters, also nonionic detergents FDA approved for food use. 

A somewhat similar configurational correlation between (leva)-glyceraldehyde and (dexfro)-lactic acid has been made by Wolfrom, Lemieux, Olin and Weisblat.36 Reductive desulfurization of tetra-acetyl-2-methyl-D-glucose diethyl thioacetal (XXVII) and hydrolysis of the product gave 2-methyl-l-desoxy-D-glucitol (XXVIII) oxidation... 

Photolysis of three 2,4-dinitroanilino-substituted carbohydrates, compounds that differ considerably from each other in photochemical reactivity, has been reported.150,151 l-Deoxy-l-(2,4-dinitroanilino)-D-glucitol (73) is photochemically unreactive in contrast, sodium 2-deoxy-2-(2,4-dinitroanilino)-D-gluconate (74) produces D-arabinose in 52% yield upon irradiation.150 The behavior of compounds 73 and 74 indicates that oxidative loss of the 2,4-dinitroanilino group during photolysis is only possible when it is accompanied by simultaneous decarboxylation. The evidence gathered from the considerable study of this reaction for noncarbohydrate systems suggested that this process is quite complex. Although useful, mechanistic proposals have... 

Both L-gulose12,13 (9) and D-gulose (d-9, see Ref. 10) have been oxidized with bromine to L- or D-gulonic acid, respectively (see Scheme 1). L-Gulose (9) has been prepared by a number of different procedures. Schemes 2 and 3 show two early procedures that afforded L-gu-lose, but the overall yields were low (<30%). In the first procedure12 (see Scheme 2), D-glucitol (10) was converted into 2,4-O-benzylidene-D-glucitol (11), which was then oxidized with lead tetraacetate to 2,4-O-benzylidene-L-xylose (12). Nitromethane was added to 12 to afford crystalline 13 in 50% yield. Hydrolysis of 13 provided 14, which was treated with sodium hydroxide, followed by sulfuric acid, to afford 9, which was isolated in 52% yield as the 2-benzyl-2-phenylhydrazone. 

In the second procedure13 (see Scheme 3), D-glucitol (10) was converted into 5-O-benzoyl-1,3 2,4-di-O-ethyl idene-6-O-trityl-D-glucitol (17) by successive treatment with acetaldehyde to produce 15, with chlorotriphenylmethane to provide 16, and with benzoyl chloride to afford 17. Selective removal of the trityl protecting group from 17, to give 18, followed by oxidation of 18, provided 19 which, on hydrolysis, afforded L-gulose (9). 

The simple cleavage of lactones 1 or 2 with alcohol and acid has not been reported. However, when 1 is treated with benzaldehyde diethyl acetal and hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (47) is formed in >90% yield.77,78 No other isomers were observed, and other acetals of benzaldehyde, as well as aliphatic aldehydes, afford similar products in good yield.77 D Addieco prepared36 similarly protected derivatives of L-gulonic acid by oxidation of l,3 2,4-di-0-ethylidene-D-glucitol (15), followed by esterification of the resulting acid with diazomethane. 

Anhydro-L-gulono-1,4-lactone (62) was prepared100 in 62% yield by the platinum-catalyzed oxidation of 1,4-anhydro-D-glucitol. Methyl 3,4,5-tri-0-acetyl-2,6-anhydro-L-gulonate (63, R = H) was obtained from D-glucuronic acid by way of the tetraacetate (63, R = OAc) and the thioglycoside101,102 (63, R = SPh) (76%), followed by reduction in the presence of Raney nickel to afford 63 (R= H) (68%). 

Lemer (29) reported a simple synthesis of L-erythrose that involves 2,3-di-O-isopropylidene-D-gulono-1,4-lactone (7b) as a key intermediate. Reduction of the lactone group of 7b with sodium borohydride, followed by periodate oxidation of the L-glucitol derivative, afforded 2,3-O-isopropy-lidene-L-erythrose. The free sugar may be readily obtained by acidic hydrolysis of the latter. 

Oxidation of secondary or primary alcohols by dehydrogenases is usually not performed biocatalytically. The reaction destroys a stereocentre, it is thermodynamically not favoured and product inhibition is a problem. It is attractive only in cases where it is necessary to discern between several hydroxy groups in a molecule. Microbial oxidation of D-glucitol to yield L-sorbose is the key step in production of vitamin C (Reichstein and Griissner, 1934). 

Oxepane (seven-membered) rings (1,6-anhydrohexitols)52 have been prepared from the 3,4-isopropylidene acetals of D-mannitol, D-glucitol, and L-iditol, by way of alkaline hydrolysis of the corresponding 1,2 5,6-dianhydrides. The ring structures of the products were established through periodate oxidation and lead tetraacetate oxidation the requisite amount of formic acid was produced, and 3 equivalents of lead tetraacetate were consumed. No inversions at any of the asymmetric centers were involved in the reactions conducted, so the oxepanes had retained the configurations of the starting hexitols. 

In the synthesis of 1,6-anhydro-D-glucitol, at least, a 2,6-anhydride is a byproduct.53 Its structure was assigned on the basis of its i.r. spectrum, in comparison with those of the 1,6- and 1,5-anhydro-D-glucitols, and the fact that no diglycolic acid was obtained after periodate oxidation followed by oxidation with hypobromite. 

Periodate oxidation of 2-acetamido-1,2-dideoxy-3,4-0-isopropylidene-D-glucitol (33) affords 4-acetamido-4,5-dideoxy-2,3-0-isopropylidene-aldehydo-c-xylose, which, on hydrolysis with acetic acid, gives31 the pyrrolidine 34. The same series of reactions was performed31" on the... 

The presence of alkoxide ion would enhance the rate of ammonolysis, and the formation of bis(amido) derivatives by an ortho-ester mechanism (see Section VI, p. 110) would be partially suppressed in the competitive set of reactions. Thus, ammonolysis of penta-O-benzoyl-D-glucose in the presence of 5 mmolar proportions of sodium meth-oxide showed a decrease of 11% in the yield of the bis(benzamido)-glucitol derivative as compared with the same reaction conducted without added methoxide ion.47... 

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