Mucons

Mucic acid [526-99-8] Mucoadhesives Muconic acid [505-70-4] Mucopolysaccharidoses Mucor circinelloides Mucor spp. 

Conversion of Cyclic to Acyclic Structures. Upon oxidation, the aromatic rings of lignin may be converted direcdy to acycHc stmctures, eg, muconic acid derivatives, or indirectly by oxidative splitting of o-quinoid rings. Further oxidation creates carboxyUc acid fragments attached to the lignin network. 

Neither the mechanism by which benzene damages bone marrow nor its role in the leukemia process are well understood. It is generally beheved that the toxic factor(s) is a metaboHte of benzene (107). Benzene is oxidized in the fiver to phenol [108-95-2] as the primary metabolite with hydroquinone [123-31-9] catechol [120-80-9] muconic acid [505-70-4] and 1,2,4-trihydroxybenzene [533-73-3] as significant secondary metabolites (108). Although the identity of the actual toxic metabolite or combination of metabolites responsible for the hematological abnormalities is not known, evidence suggests that benzene oxide, hydroquinone, benzoquinone, or muconic acid derivatives are possibly the ultimate carcinogenic species (96,103,107—112). 

Norite, is heated to boiling by introduction of steam, filtered through a Norite filter pad by suction, and cooled in an ice-salt bath. The muconic acid is precipitated by the addition of a large excess (1500 ml.) (sp. gr. 1.18) of concentrated hydrochloric acid to the cold solution. The acid is added in a thin stream to the well-stirred solution. After 2 hours the muconic acid is filtered, washed first with two 400-ml. portions of cold water and then with 200 ml. of methyl alcohol, and dried at 85°. The yield of nearly colorless product melting at 296-298°, with decomposition, amounts to 165-195 g. (37-43%). 

Muconic acid has been obtained in a variety of ways. The procedures that seem most important from a preparative point of view are by treatment of ethyl o ,5-dibromoadipate with alcoholic potassium hydroxide, by condensation of glyoxal (as the sodium bisulfite addition product) with malonic acid, by heating ethyl l-acetoxy-l,4-dihydromuconate (obtained by condensing ethyl oxalate and ethyl crotonate, acetylating, and reducing),and by oxidation of phenol with peracetic acid. ... 

Figure 4.9 Mechanisms of the reactions catalyzed by the enzymes mandelate racemase (a) and muconate lactonizing enzyme (b). The two overall reactions are quite different a change of configuration of a carbon atom for mandelate racemase versus ring closure for the lactonizing enzyme. However, one crucial step (red) in the two reactions is the same addition of a proton (blue) to an intermediate of the substrate (red) from a lysine residue of the enzyme (E) or. In the reverse direction, formation of an intermediate by proton abstraction from the carbon atom adjacent to the carboxylate group.

Goldman, A., Ollis, D.L., Steitz, T.A. Crystal structure of muconate lactonizing enzyme at 3 A resolution. 

Neidhart, D.J., et al. Mandelate racemase and muconate lactonizing enzyme are mechanistically distinct and structurally homologous. Nature 347 ... 

Certain monomers crystallize in a conformation such that they can be zipped together without changing the symmetry of the crystal lattice. In the crystalline state, the arrangement of monomers is strictly determined by crystal packing. Polymerization is usually initialed by irradiation with UV, X- or y-rays and is assumed to proceed by a radical mechanism. For example, muconic acid esters (25, 27, 29) and ammonium salts (26,28, 30) can be stcrcospccifically polymerized in the crystalline state to high conversion.224-227228 This form of... 

Hydroxylation and dioxygenation are not, however, mntnally exclusive, because the toluene dioxygenase from Pseudomonasputida FI hydroxylates both phenol and 2,5-dichloro-phenol with the introduction of only one atom of oxygen (Spain et al. 1989). Snbsequent degradation by dioxygenation follows established pathways in which chloride is eliminated from muconic acids after ring fission. 

Fluorinated Muconates Formed from Fluorophenols by Phenol Hydroxylase and Catechol 1,2-Dioxygenase from Exophilia jeanselmei Fluoromuconate Metabolite Phenolic Substrate(s)... 

---