Coniferyl derivatives

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

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... 

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). 

Well-defined reaction and catalytic systems enable the development of fundamental knowledge that helps in with long term and more exhaustive problem solving possibilities. Thus the debate is not whether studies on model compounds are useful or not, but the choice of model compounds themselves. These should represent the nature and characteristic of the biomass fraction that one is studying. Not surprisingly, efforts to identify representative model compounds are gaining attention. 4-Hydroxyphenylpropane derivatives such as coniferyl, cou-... 

Evidence for the participation in lignification of radicals in the form Rfl was not obtained from lignols extracted from simulated lignification experiments with coniferyl alcohol in vitro. Actually more direct proof was obtained here structures, e.g. (XII), that must have arisen from this form of the coniferyl radical were isolated from natural lignins by mild hydrolysis (see Section I). So far only structures derived from combinations of Rd type radicals with Rj, t5rpe radicals have been isolated 47, 705, 776, 777), but evidence for combinations of Rd radicals with Ra radicals has been secured by the detection of 40-(3,4-dimethox3q)henyl)-... 

Figure 4. Degradation of DHcP 5 by lignin peroxidase/H2O2 system. In DHcP 5> the portion enclosed with rectangular represents the portion derived from coniferyl alcohol. LP lignin peroxidase.

Lignin has a complex structure that varies with the source, growing conditions, etc. This complex and varied structure is typical of many plant-derived macromolecules. Lignin is generally considered as being formed from three different phenylpropanoid alcohols— coniferyl, coumaryl, and sinapyl alcohols, which are synthesized from phenylalanine via various cinnamic acid derivatives and commercially is sometimes treated as being composed of a Cg repeat unit where the superstructure contains aromatic and aliphatic alcohols and ethers, and aliphatic aldehydes and vinyl units. 

Figure 2. 13C NMR solid state difference spectra of (a) L. leucocephala and (b) T. aestivum (24) root tissue previously administered [1-13C] ferulic acid 5a. Fig. 2c shows the difference spectrum of a DHP polymer, derived from [1-13C] coniferyl alcohol 2a (29). CP/MAS spectra were obtained at 50 MHz on a Varian XL-200 Spectrophotometer equipped with a Doty Scientific MAS Probe. SSB = spinning side band.

Figure 7. Preparation of synthetic lignin 16, ethylated copolymer of coniferyl alcohol 7 and arylglycerol-/ -syringaresinol ether 6. In 16, the rectangular enclosure represents an assumed structure of the moiety derived from 7.

Coniferyl alcohol [4-hydroxy-3-methoxy-cinnamyl alcohol, 3-(4-hydroxy-3-methoxyphenyl)-2-propen-l-ol] [458-35-5] M 180.2, m 73-75°, 73-75°, b 163-165°/3mm. It is soluble in EtOH and insoluble in H2O. It can be recrystd from EtOH and distd in a vacuum. It polymerises in dilute acid. The benzoyl derivative has m 95-96° (from pet ether), and the tosylate has m 66°. [derivatives Freudenberg and Achtzehn B 88 10 1955, UV Herzog and HillmerR64 1288 1931. ... 

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. 

Already in 1897 Klason [52] suggested that gymnosperm lignin is derived from coniferyl alcohol. On the basis of experiments using isoeugenol as a model substance, Erdtman [53] advanced the hypothesis that lignin is a product of the oxidative polymerization of coniferyl alcohol ... 

Guaiacylglycerol-/3-coniferyl ether is a dimeric decomposition product of coniferous lignin dehydrodivanillin may be also formed by dimerization of vanillin after formation from lignin. Among the lignin decomposition products are mono-, di- and triphenol derivatives which are derived from the different types of lignin of needle trees, deciduous trees, or graminees. 

From a physiological standpoint, molecular and biochemical studies have suggested that ozone stimulates phenolic metabolism and the biosynthesis of lignin or other substances partly derived from coniferyl alcohol [89]. Lignification of mesophyll cell walls might confer some protection against oxidation, and thus be a defence response against ozone [90]. 

The second type of data is derived from biochemical experiments related to the three cinnamyl alcohols—/>-coumaryl alcohol (I), coniferyl alcohol (II), and sinapyl alcohol (III) and their phenolic glucosides— >-glucocoumaryl alcohol (IV), coniferin (V), and syringin (VI). These and the following formulas do not differentiate between cis and trans isomers. 

Dehydrodiconiferaldehyde (XVIII) 25) is an unsaturated aldehyde corresponding to XVII and is formed partly by condensation of free radicals derived from coniferyl alcohol and coniferaldehyde. 

The yield of guaiacylglycerol 0-coniferyl ether (XXII) 31) probably surpasses even pinoresinol (XIX) and dehydrodiconiferyl alcohol (XVII). So far it has not been obtained in crystalline form, possibly because of its labile benzyl alcohol group. A derivative has been obtained in the crystalline state and has also been synthesized 15). Guaiacylglycerol 0-coniferyl ether also occurs to a small extent in spruce cambium and has been isolated from spruce lignin as a crystalline derivative 42). 

The most significant conclusion that may be drawn from these results is that palladium-charcoal exhibits similar catalytic properties as does Raney nickel if used under similar conditions. The same types of lignin hydrogenolysis products are obtained, and as before the major fraction under neutral conditions is the phenylpropanol derivative, dihydro-coniferyl alcohol. With a minimum temperature ca. 150°C. required for any reaction to occur and an optimum temperature ca. 195°C. for maxi-... 

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