Coniferyl alcohol synthesis

The synthesis of tetrahydrofuran derivatives from unsaturated alcohols via hydroformylation intermediates was developed many years ago. Moderate yields are obtained from but-2-en-l,4-diol (Scheme 54)94 but hydroformylation is not the major pathway when coniferyl alcohol is subjected to the oxo process (Scheme 55).9S A more complicated reaction is involved... 

Silica gel successfully catalyzed the stereoselective synthesis of several glucoside terpenoids. Treatment of 49a with propan-2-ol, geraniol, the tetrahydropyranyl (THP) ether of coniferyl alcohol, and (—)-perillyl alcohol gave glucosides 52a-d in good yields (Scheme 12). The acid-labile THP group was retained under these reaction... 

Benzodioxanes (6, 516). The earlier synthesis of benzodioxanes by oxidative coupling of catechol derivatives with methoxypropenylphenols has been extended to the first synthesis of the complex benzodioxane silybin (3) shown in equation (I).2 The starting materials are (2R,3R)-dihydroqucrcctin (I) and coniferyl alcohol (2). In this case, the reaction is not regioselective, 3 and the isomeric 4 being obtained in nearly equal amounts. 

Oxidative coupling polymerization provides great utility for the synthesis of high-performance polymers. Oxidative polymerization is also observed in vivo as important biosynthetic processes that, when catalyzed by metalloenzymes, proceed smoothly under an air atmosphere at room temperature. For example, lignin, which composes 30% of wood tissue, is produced by the oxidative polymerization of coniferyl alcohol catalyzed by laccase, an enzyme containing a copper complex as a reactive center. Tyrosine is an a-amino acid and is oxidatively polymerized by tyrosinase (Cu enzyme) to melanin, the black pigment in animals. These reactions proceed efficiently at room temperature in the presence of 02 by means of catalysis by metalloenzymes. Oxidative polymerization is observed in vivo as an important biosynthetic process that proceeds efficiently by oxidases. 

Irradiation of 2,2-dimethyl chromene through Pyrex using a 550-W Hanovia lamp initiates a retro 4 + 2 reaction to form the extended quinone methide 4, which reacts with methanol to form a pair of methyl ethers (Scheme 6A).18 Flash photolysis of coniferyl alcohol 5 generates the quinone methide 6 (Scheme 6B) by elimination of hydroxide ion from the excited-state reaction intermediate.19 The kinetics for the thermal reactions of 6 in water were characterized,20 but not the reaction products. These were assumed to be the starting alcohol 5 from 1,8-addition of water to 6 and the benzylic alcohol from 1,6-addition of water (Scheme 6). A second quinone methide has been proposed to form as a central intermediate in the biosynthesis of several neolignans,21a and chemical synthesis of neolignans has been achieved... 

Digestion yields the active anti-PTH aglycone Coniferyl alcohol [lignin synthesis precursor]... 

Intramolecular oxidative coupling of phenols (6, 516). A biomimetic synthesis of natural silybin (3), an interesting antihepatotoxic agent, involves oxidation of a mixture of optically active 1 and coniferyl alcohol (2) with AgO in a benzene-acetone mixture at 55°. This reaction affords a mixture of silybin (3) and isosilybin (4) in 78% yield. The products 3 and 4 are diastereomeric mixtures at C2 and Cs- relative to C2 and... 

Schmid, G. and Grisebach, H. (1982) Enzymic synthesis of lignin precursors purification and properties of UDP-glucose coniferyl alcohol glucosyltransferase from cambial sap of spruce (Picea abies L.). Eur.. Biochem., 123, 363-70. 

Lignin is synthesized by a polycondensation process involving free radicals in plant cells from three phenol propane building blocks coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol (Jeffries, 1994). Due to the random nature of its synthesis, lignin does not show a specific structure (Paul and Clark, 1996) and the relative proportions of the phenol propanoid units will vary... 

Highly reactive quinone methide can be utilized as intermediates in organic synthesis. From the viewpoint of biomimetic synthesis, silybin (782) bearing a benzodioxane skeleton was synthesized in 44.5% yield, together with isosilybin (784) (33.5%), by AgiO-mediated oxidation of equimolar amounts of 27 ,37 -dihydroquercetin (783) and coniferyl alcohol (298) in benzene-acetone. The p-quinone methide 785 must be generated as a reactive intermediate (Scheme 156) °. 

Biomimetic synthesis of model compounds for dibenzodioxocines occurring in wood lignins was carried out, as follows. On oxidation with Ag20 in CH2CI2 (room temp., 45 h), the reaction of dehydrodipropylguaiacol (786) with coniferyl alcohol (298) provided... 

A model system for the synthesis of lignin-like polymers showed that jols would react with the quinone-methlde intermediates in this system by a 1-6 addition (J ). Utilizing this model system, chloroanilines were copolymerized with coniferyl alcohol in the presence of horseradish peroxidase Type II enzyme, hydrogen peroxide, vanillyl alcohol initiator and pH 7.2 buffer (J57). The mechanism of this copolymerization reaction is shown in Equation 36. The... 

The xanthonolignoid kielcorin (35) has been isolated from several Hypericum species [15,19]. Gottlieb et al. accomplished the synthesis of kielcorin in low yield by oxidative coupling of 3,4-dihydroxy-2-methoxyxanthone and coniferyl alcohol with silver oxide [62]. Then, a facile synthesis of kielcorin (35) from readily available materials 3-benzyloxy-4-hydroxy-2-methoxyxanthone (30) and ethyl 2-bromo-3-(4-benzyloxy-3-methoxyphenyl)-... 

Ralph, J., and Zhang, Y. (1998) A new synthesis of (Zj-coniferyl alcohol, and characterization of its derived synthetic lignin. Tetrahedron 54, 1349-1354. 

Plants - Lignin, tannins, and pigments, flavor components of spices (cinnamon oil, wintergreen oil, bitter almond, nutmeg, cayenne pepper, vanilla bean, clove, and ginger) are derived from coniferyl alcohol. Coniferyl alcohol, in turn, is derived from phenylalanine and tyrosine. Phenylalanine is also a precursor of plant pigments and related polyphenolic compounds called flavonoids. The biosynthetic scheme leads to a class of flavonoids called anthocyanins, which are common flower pigments.. An offshoot of this pathway leads to the synthesis of cocaine. 

Lignin, tannins, pigments, and flavor components of spices (cinnamon oil, wintergreen oil, bitter almond, nutmeg, cayenne pepper, vanilla bean, clove, and ginger) are all derived from coniferyl alcohol, which is also the central intermediate in lignin synthesis. 

In the synthesis of DHP, two different modes have been employed, the Zulauf and the Zutropf methods. The former involves a stepwise addition of enzyme to a solution of coniferyl alcohol whereas in the latter, the reverse is used. From a structural point of view, the two methods give slightly different DHPs but the Zutropf-DHP is considered as being somewhat more lignin-like [43]. For both types of DHPs, however, considerable structural differences are encountered in comparison with MWL. 

In vitro synthesis of lignin, a typical phenolic biopolymer, was claimed by the HRP-catalyzed terpolymerization of lignin monomers, p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol (14 80 6 mol%) in an extremely dilute aqueous solution at pH 5.5 (282). Dialysis membrane method was applied to the polymerization of coniferyl and sinapyl alcohols, yielding insoluble polymeric materials (283). In the HRP-polymerization of coniferyl alcohol in the presence of a small amount of lignin component, the molecular weight distribution became much broader than that in the absence of lignin (284). 

The (Z)-monolignols (hydroxycinnamyl alcohols) 49 were found along with their predominant ( )-isomers in a number of plants. Still-Gennarri reaction was successful applied to the preparation of (Z)-unsaturated esters 48 from aldehyde 47. The ester 48 was further converted to (Z)-coniferyl alcohol 49 in the synthesis of (Z)-monolignols. ... 

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