Syringic acid

This type of cement has been further improved by the substitution of -hexyl van ill ate [84375-71-3] and similar esters of vanillic acid [121 -34-6] and/or syringic acid [530-57 ] for eugenol (93—95). These substituted cements are strong, resistant to dissolution, and, unlike ZOE and EBA cements, do not inhibit the polymerization of resin-base materials. Noneugenol cements based on the acid—base reaction of zinc and similar oxides with carboxyhc acids have been investigated, and several promising types have been developed based on dimer and trimer acids (82). 

This was confirmed by Spath s synthesis of sinapine iodide by the following method. Syringic acid was converted into carbethoxysyringic acid, and this through the acid chloride into the aldehyde,... 

Synthese, /. synthesis, synthesieren, v.t. synthesize, synthetisch, a. synthetic, synthetisieren, v.t. synthetize, synthesize. Syringasaure, /. syringic acid, syrisch, a. Syrian, syrup-. Syrup-, see sirup-. Sirup-. 

Laccase (PCL) as well as peroxidases (HRP and SBP) induced a new type of oxidative polymerization of the 4-hydroxybenzoic acid derivatives, 3,5-dimethoxy-4-hydroxybenzoic acid (syringic acid) and 3,5-dimethyl-4-hydroxybenzoic acid. The polymerization involved elimination of carbon dioxide and hydrogen from the monomer to give PPO derivatives with molecular weight up to 1.8 x lO (Scheme 22). - ... 

The total phenolic content in XRPP was 1.10%. The major components were found to be p-hydroxybenzoic acid (0.44%), vanillin (0.19%), syringic acid (0.13%), and syringaldehyde (0.13%). The contents of p-hydroybenzaldehyde, vanillic acid and ferulic acid were 0.032, 0.015 and 0.020%, respectively. Gallic acid, protocatechuic acid and cinnamic acid were detected in trace amounts. 

FIGURE 4.8 Reaction between 2,4,5-trichlorophenol and syringic acid catalyzed by laccase. 

Bollag J-M, S-Y Liu (1985) Copolymerization of halogenated phenols and syringic acid. Pest Biochem Physiol 23 261-272. 

All cements that contain eugenol inhibit the polymerization of acrylates, and those of EBA-eugenol are no exception. In order to remedy this and other defects, Brauer and his coworkers examined alternatives to eugenol (Figure 9.7). These included the esters of vanillic acid (3-methoxy-4-hydroxybenzoic acid, HV) and syringic acid (3,5-dimethoxy-4-hydroxy-benzoic acid). Both are 3-methoxy-4-hydroxy compounds and are thus chemically related to eugenol and guaiacol. Both are solids and have to be dissolved in EBA where they form satisfactory cements with EBA zinc oxide powder. The vanillate (EBA-HV) cements are the more important. 

Syringate cements possess similar advantages to the vanillate cements. In addition, syringic acid possesses cariostatic properties, so syringates may inhibit the development of caries (dental decay). Again these advantages need to be confirmed. 

Brauer, G. M. Stansbury, J. W. (1984a). Cements containing syringic acid ester-o-ethoxybenzoic acid and zinc oxide. Journal of Dental Research, 63, 137 0. 

Syringic acid (4-hydroxy-3,5- +0.75 (calomel) glassy carbon 268... 

Wang et al. (62) reported the oxidative polymerization of a mixture of phenolic compounds in aqueous solution containing mont-morillonlte, illite, and kaolinite, each of which had been mixed with quartz in a 3 7 ratio, and by quartz alone. The mixture of phenolic compounds contained gallic acid, pyrogallol, protocatechuic acid, caffeic acid, orcinol, ferulic acid, p-coumaric acid, syringic acid, vanillic acid, and p-hydroxybenzoic acid. The oxidative... 

Fig. 2.79. Chromatograms of a white (I) and red wine sample (II). (LC-DAD signals at three different wavelenghts 256, 324, 365 nm). Peak identification 1 = gallic acid 2 = protocatechuic acid 3 = p-hydroxybenzoic acid 4 = vanillic acid 5 = caffeic acid 6 = (+)-catechin 7 = syringic acid 8 = p-coumaric acid 9 = ( — )-epicatechin 10 = ferulic acid 11 = fraras-resveratrol 12 = rutin 13 = myricetin 14 = cw-resveratrol 15 = quercetin A = caftaric acid B = coutaric acid. Reprinted with permission from M. Castellari et al. [196],...

The fungal enzyme from R. praticola was able to catalyze the oxidative coupling of pentachlorophenol (PCP) and syringic acid, a representative of phenol carboxylic acids from lignin occurring in HS structures. 

A lactase from the fungus Trameles aversicolor was shown to catalyze the copolymerization of syringic acid and 2,6-xylenol, a major pollutant in streams and other water resources, which is known to be toxic to fish and other organisms. 

The GC/MS study of methylated fulvic acid showed the presence of -hydroxybenzoic acid (ff 166), vanillic acid (Nr " 196), a methyldihydroxybenzoic acid (M " 210), coumaric acid (M+ 192), syringic acid (M" " 226), caffeic acid (fT " 222), ferulic acid (M" " 222), and stearic acid (M" " 298). The same compounds were present in humic acid, along with palmitic acid (M" " 270). The presence of these compounds was confirmed by TLC, using standard compounds. 

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