Xylaric acid

To the names of aldaric acids that are symmetrical, which therefore have no D- or L- prefix, the prefix meso- may be added for the sake of clarity. Examples mero-erythraric acid, meso-ribaric acid, meso-xylaric acid, meso-allaric acid, meso-galactaric acid. 

Dihexylxylaramide (2). To a 250 mL round-bottom flask equipped with a magnetic stirrer was added methanol (150 mL), and the flask then cooled to 5 C. Acetyl chloride (5 mL) was added to the cold methanol and then xylaric acid (18 g, 0.18 mol, reference 18) was added to the methanolic HCl solution. The reaction mixture was refluxed for 16 h, concentrated to a syrup, and residual water removed from the syrup by azeotropic distillation with benzene. Esterification was complete but the product (1) contained more than one ester component as both ester and 5-membered lactone functions were observed in its IR spectrum (neat, 1745 and 1795 cm, ester and lactone C=0 respectively). 

Dimethylxylaramide 1- To a 250 mL round-bottom flask equipped with a magnetic stirrer was added methanol (50 mL) and the xylaric acid - methanol esterification product (6.7 mmol in 10 mL of methanol) prepared as described above. Triethylamine (6.5 mL, 46 mmol) and methylammonium chloride (1.0 g, 14.7 mmol) were then added to the methanol solution and the reaction mixture was refluxed with stirring overnight. The mixture was concentrated and the residue was washed several times with methanol. The... 

Galbis et al. described a variety of carbohydrate-based linear polyesters 61 of the poly(alkylene dicarboxylate) type that were obtained by polycondensation reactions of the alditols 2,3,4-tri-(9-methyl-L-arabinitol (9) and 2,3,4-tri-O-methyl-xylitol (10), and the aldaric acids 2,3,4-tri-(9-methyl-L-arabinaric acid (26) and 2,3,4-tri-(9-methyl-xylaric acid (27), butanediol, and adipic acid were also used as comonomers [28]. Copolyesters of the poly(aIkylene-c )-arylene dicarboxylate) type were obtained using bisphenols as comonomers (Scheme 1). Chemical polycondensation reactions were conducted in bulk or in solution. Enzymatic polycondensation reactions of adipic acid with the above-mentioned alditols were carried out successfully using Lipozyme and Novozyme 435. The hydrolytic degradations of some of these polyesters were also described. 

Galbis et al. [31] described the preparation of the pentachlorophenyl esters of 2,3,4-tri-O-methyl-L-arabinaric and xylaric acids (26 and 27) as suitable bifunctional monomers for linear polycondensations. 

The xylose produced via enzymatic hydrolysis of the hemicellulose fraction could be converted via microbial fermentation into xylitol (which has been listed by the US Department of Energy among the top 12 value-added platform chemicals) for the production of a range of chemicals, including xylaric acid, propylene glycol, ethylene glycol and a mixture of hydroxyl-furans and polyesters (Werpy and Petersen, 2004). 

FIGURE 1.5 D-Arabinaric acid (7), D-ribaric acid (8), D-xylaric acid (9), D-glucaric acid (10), L-glucaric acid (11). 

COOH Xylaric acid A mvso compound inactive... 

Typically, condensations to polyamide (II), are carried out between an activated, i.e., esterified (diester, ester/lactone, dilactone) form of the aldaric acid (I), and a primary diamine in a polar protic solvent such as methanol at room temperature. Under those conditions any starting single ester form of a five or six carbon aldaric acid is rapidly converted to an equilibrium mixture of acyclic diester and ester/lactone forms. Dilactone, if formed at all, is present in only small amounts. The starting monomer esterified form(s) of the aldaric acid differ from one acid to an other. For example, the monomers of choice for L-tartaric acid (1) and weso-galactaric acid (4) are simple diesters, while for D-glucaric acid suitable monomers are ester/lactones, dilactone, or even the entire alcohol esterified mixture (10). Xylaric acid is also conveniently polymerized as its esterification mixture while the D-mannaric acid monomer is the 1,4 6,3-dilactone (13a). 

Figure 5. Some branched cycloses, cyclitols and alpha, beta-unsaturated cyclic ketones derived from xylaric acid some acyclic c> /o (8 - 9) and ribo (10) ring precurors.

Propylene glycol, ethylene glycol, glycerol, xylaric acid, furfural... 

Xylaric acid, 9CI. iLyXo-Saccharic acid. Xylosaccharic acid [10158-64-2]... 

The structure of nogalamycin, an antibiotic containing the branched-chain sugar nogalose, and that of o-hamamelose in solution are mentioned in Chapters 18 and 20, respectively. The preparation of an unusual trihalogenated, branched-chain heptulose (147) from xylaric acid has been discussed in Chapter 7. 

The syntheses of several dialkyl xylarates from xylaric acid, and their conversion to 2,4-0-isopropylidene acetals and thence 3-O-methacryloyl derivatives have been described. " The copper(n) catalysed oxidation of tartaric acid by hexacyanoferrate in alkaline medium has been reported. ... 

The term aric is used with the normal configurational prefix the tartaric acids are threaric or erythraric acids, mucic acid is galactaric acid, and -saccharic acid is glucaric acid. The name xylaric acid is much shorter than xylo-trihy-droxyglutaric acid. For an additional discussion see below and Chapter I, particularly p. 28. In the present text both forms are used, but the new usage is preferred. 

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