Sinapyl-alcohol

According to a widely accepted concept, lignin [8068-00-6] may be defined as an amorphous, polyphenoHc material arising from enzymatic dehydrogenative polymerization of three phenylpropanoid monomers, namely, coniferyl alcohol [485-35-5] (2), sinapyl alcohol [537-35-7] (3), and /)-coumaryl alcohol (1). 

Coniferyl and sinapyl alcohol derivatives Ligularia duciformis SiOj B + Me2CO B + AcOEt UV 254 nm H2SO4 + temperature Identification 74... 

Lignin polymerization is a natural process initiated by the enzymatic oxidation of hydroxycinnamyl alcohols such as /)-coumaryl (CM), coniferyl (CF), and sinapyl alcohols (SN), which are known as monolignols (Scheme 2.20).60... 

Tobimatsu, Y. Takano, T. Kamitakahara, H. Nakatsubo, F. Azide ion as a quinone methide scavenger in the horseradish peroxidase catalyzed polymerization of sinapyl alcohol. J. WoodSci. 2008, 54, 87-89. 

Lu, F. Ralph, J. Morreel, K. Messens, E. Boerjan, W. Preparation and relevance of a cross-coupling product between sinapyl alcohol and sinapyl p-hydroxybenzoate. Org. Biomol. Chem. 2004, 2, 2888-2890. 

Zanarotti, A. Preparation and reactivity of 2,6-dimethoxy-4-allylidene-2,5-cyclohexa-dien-l-one (vinyl quinone methide). A novel synthesis of sinapyl alcohol. Tetrahedron Lett, 1982, 23, 3815-3818. 

Aoyama, W. Sasaki, S. Matsumura, S. Mitsunaga, T. Hirai, H. Tsutsumi, Y. Nishida, T. Sinapyl alcohol-specific peroxidase isoenzyme catalyzes the formation of the dehy-drogenative polymer from sinapyl alcohol. J. Wood Sci. 2002, 48, 497-504. 

Takahama, U. Oniki T. Shimokawa H. A possible mechanism for the oxidation of sinapyl alcohol hy peroxidase-dependent reactions in the apoplast enhancement of the oxidation hy hydroxycinnamic acids and components of the apoplast. Plant Cell Physiol. 1996, 37, 499-504. 

Takahama, U. Oniki, T. Enhancement of peroxidase-dependent oxidation of sinapyl alcohol hy esters of 4-coumaric and ferulic acid. In Plant Peroxidases, Biochemistry and Physiology Ohinger, C. Burner, U. Ebermann, R. Penel, C. Greppin, H., Eds. Universite de Geneve, Geneve Switzerland, 1996 pp. 118-123. 

Recent work by Atalla(H) supports the idea that lignin is at least a semi-ordered substance in wood with the plane of the aromatic ring parallel to the cell wall surface. Woody plants synthesize lignin from trans-coniferyl alcohol (pines), trans-sinapyl alcohol 2 (deciduous), and trans-4-coumaryl alcohol 3 by free radical crosslinking initiated by enzymatic dehydrogenation(l2). Structures of these alcohols are given in Figure 1. 

Whilst it is not possible to give a completely detailed structure for lignin, a great deal is known about the molecule. All lignins appear to be polymers of 4-hydroxycinnamyl alcohol (/>-coumaryl alcohol) or its 3- and/or 3,5-methoxylated derivatives, respectively coniferyl and sinapyl alcohol (Figure 3.1). 

Since the oxidative polymerization of phenols is the industrial process used to produce poly(phenyleneoxide)s (Scheme 4), the application of polymer catalysts may well be of interest. Furthermore, enzymic, oxidative polymerization of phenols is an important pathway in biosynthesis. For example, black pigment of animal kingdom "melanin" is the polymeric product of 2,6-dihydroxyindole which is the oxidative product of tyrosine, catalyzed by copper enzyme "tyrosinase". In plants "lignin" is the natural polymer of phenols, such as coniferyl alcohol 2 and sinapyl alcohol 3. Tyrosinase contains four Cu ions in cataly-tically active site which are considered to act cooperatively. These Cu ions are presumed to be surrounded by the non-polar apoprotein, and their reactivities in substitution and redox reactions are controlled by the environmental protein. 

It has also been observed that syringyl-type precursors arc transformed in part into guaiacyl-type lignin 78, 90, 91), i.e. a demethoxyla-tion, not merely a dcmcthylation has taken place. It has also been found that sweet almond emulsin hydrolyses syringin only extremely slowly 143) and that pure peroxidase does not oxidize sinapyl alcohol well 71). The metabolism of the sinapyl component of lignin is perhaps not quite as simple as the analogy between its />-coumaryl and conifcryl components suggests. 

Furthermore, lignin is synthesised from the monomers p-coumaryl, coniferyl and sinapyl alcohols, see Figure 49 [65]. 

Figure 49 The precursors of lignin biosynthesis, p-coumaryl alcohol (I), coniferyl alcohol (II) and sinapyl alcohol (III). [65]...

On the other hand, biosynthetic pathways that do not involve the conversion from coniferyl alcohol to matairesinol have been proposed for lignans composed of two syringyl (3,5-dimethoxy-4-hydroxyphenyl) groups (+)-syringaresinol formation in Liriodendron tulipifera [50] and (H-)-lyoniresinol biosynthesis in Lyonia ovalifolia var. elliptica [51]. Enantioselective coupling of two sinapyl alcohol units was proposed for the selective formation of (H-)-syringaresinol [50], On the other hand, a non-enantioselective dimerization of sinapyl alcohol was proposed for (+)-lyoniresinol biosynthesis and the enantioselectivity in the biosynthesis was ascribed... 

Katayama T, Ogaki A (2001) Biosynthesis of (-l-)-syringaresinol in Liriodendron tulipifera I feeding experiments with L-[U- C]phenylalanine and [8- C]sinapyl alcohol. J Wood Sci... 

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