Catechol urushiol

The reason why synthesis of natural urushiols involves multistep, tedious procedures is that the reactive unsaturated group cannot be directly introduced on the catechol moiety protection and deprotection of the catechol moiety are... 

Over the past hundred years numerous experimental methods have been used for the study of urushi and the finished lacquer ware. The first recorded reports on chemical experiments are those of Ishimatsu (14), Yoshida (13) and Korschelt and Yoshida (15). Miyama gave the name urushiol to urushic acid (16), and he and Majima and coworkers (17-26) further explored the composition of urushi. Work by Sunthanker, Dawson, and Symmes (27,28) helped to determine that it contained three substituted catechol derivatives containing various diflFerent side chains. The previously mentioned reports by Kumanotani and coworkers (1-7) have allowed us to understand more of the details of the raw urushi, the complex mechanism of film hardening, and some properties of the hardened layers. 

The same intermediate (A) has led to the synthesis of urushiols by Japanese workers and with 3-(8-oxooctyl)veratrole has been employed firstly for the synthesis of the dimethyl ethers of 3-[(8Z,11Z,14)-pentadecatrienyl- and 3-[(8Z,11E,13E)-pentadecatrienylurushiol (ref.160). Secondly a related procedure (ref. 161), has been used for the free phenol, 8(Z),11(Z),14-urushiol by way of the diacetate of the ArCg intermediate employed earlier, (ref. 150, 151) namely 3-(8-oxooctyl)catechol diacetate. This was prepared by the modified synthetic route depicted rather than by semi-synthesis from a natural product. 

The sap from Rhus vemicifera by extraction with light petroleum affords urushiol a mixture which is considerably more sensitive to oxidative deterioration and polymerisation than the cashew phenols since it is both a catechol and even more highly unsaturated. The composition of the sap is to some extent dependent on the source but typically it contains urushiol (55-65%), water (20-30%), glycoprotein (2-3%), polysaccharides (5-7%) and laccase (-c 1%) (ref. 196 ). 

Not only a wide range of cations complex with the catechol system of urushiol but the borate anion also undergoes quite strong association. Thus urushiol together with Aliquat 336 was valuable for the solvent extraction of this anion probably through the formation of 1 1 and 2 1 chelates (ref.293). 

The cleavage of urushiol by catechol-2,3-dioxygenase has been studied (ref. 324) and the oxidation of anacardic aldehyde to urushiol with manganeses dioxide (ref. 325), an alternative to the Dakin reaction descibed some years ago (ref. 88). Experiments on the methylation of urushiol (refs. 88,89) Indicate that the 3-hydroxyl group reacts preferentially under mild conditions. Hydrogenated urushiol, 1,2-dihydroxy-3-pentadecylbenzene, reacted similarly to form 1-methoxy-2-hydroxy-3-... 

A component of urushiol, the active constituent of the irritating oil of poison ivy, is 3-pentadecyl-l,2-dihydroxy-benzene. Synthesize this compound from catechol. 

The antigenic component of poison ivy, poison oak and poison sumac, called urushiol, is found within secretory canals located in the plant s leaves, roots and phloem, which is just below the bark [30]. The active ingredient in poison ivy mostly comprises penta-dec(en)yl catechols [18], and for poison oak it is mostly comprises heptadec(en)yl catechols. In the case of T. radicansy exposure may occur to the tiny brown rootlets that attach the vine to the tree or post on which it climbs, but usually it occurs when the leaf surface is broken so that the sap containing the... 

Toxicodendrons contain varying amounts of alk(en)yl catechols which are highly antigenic [18]. Poison-ivy urushiol has mostly pentadec(en)yl catechols, while poison oak urushiol has mostly heptadec(en)yl catechols. The two-carbon difference in the two side chains is of relatively minor importance. However, the... 

Johnson RA, Baer H, Kirkpatrick CH, et al. (1972) Comparison of the contact allergenicity of the four pentadecyl catechols derived from poison ivy urushiol in human subjects. J Allergy Clin Immunol 49 27-35... 

Urushiol, the first constituent mentioned, is a mixture of 3-substituted catechol derivatives with a 15 or 17 carbon chain having a olefin number 0-3253,5. The average number of olefins in the side chain of urushiol is 2.0-2.5. Constituents of this Japanese lacquer urushiol are seen to be the same as those of urushiol in poison ivy of U.S.A.5... 

By a series of studies of the enzymatic and non-enzymatic polymerization mechanism of urushiol. Scheme 2 has been established. Urushiol (1) is oxidized into the corresponding quinone (2)26 d formed quinone (2) undergoes C-C and C-0 coupling reaction with catechol nucleuse or the triene side chain urushiol, a major component of urushiol, giving dimeric urushiol (3), (4) and (5) 27-30 ... 

The catechol nucleus of these dimeric urushiol undergoes enzymatic oxidation into the corresponding quinones following the same type C-C and C-0 coupling reaction with urushiol or with each other. Thus urushiol grows in its polymerization up to of 20,000-30,000 in the lacquer-making process from sap. 

Furthermore, as substituents for urushiol, we found that catechol derivative, made by the Friedel-Craftes type alkylation of catechol with linseed oil, linseed oil alcohol made by the reduction of linseed oil or oligomeric butadiene can be used.Though there are number of papers relating to synthesis of urushiol components39 synthesis of the triene side chain urushiol is faced with difficulties. On the other hand, recently, a report appeared about the formation of urushiol by tissue cell structures of Rhus vernicifera stock This method seems to be the most interesting to synthesize urushiol, suggesting a need for a further studying. 

This review gives an overview of enzymatic synthesis and the properties of polymers derived from polyphenols. Catechol derivatives were enzymatically oxidized to form polymers. Urushiol analogues were designed and cured by laccase catalyst to produce artificial urushi of good elasticity. 

Cardanol is a main component of thermally treated cashew nut shell liquid (CNSL), and is a phenolic compound with a long unsaturated hydrocarbon chain substituted in the meta position (Figure 2.17a). Urushiol, which is obtained from lacquer tree, poison ivy, poison oak, and poison sumac (Toxicodendron), and used for a raw material of a lacquer (urushi) in East Asia, is also a phenolic compound of catechol with a long unsaturated or saturated hydrocarbon chain (Figure 2.17b). Cardanol-based polymers have been reported very often, while there are a few research reports on urushiol-based polymers. Research on polymers synthesized from cardanol or CNSL are reviewed elsewhere.In the late 1980s, cardanol or CNSL-based polymers began to be reported as novel phenol-formaldehyde type resins and novel epoxy resins.Thereafter, Pillai and his co-workers have vigorously studied synthesis of various type of cardanol-based polymers polymers obtained... 

Concurrently, the Egyptians, Japanese, and Chinese were beginning to develop lacquers (Stillman, I960). Some time before 200 b.c., the Chinese used the exudation (sap) from the conifer Rhus vemicifera (which became known as the sumac or varnish tree) as a coating. This plant has also been called the urushi tree. The tree belongs to the same family as the poison ivy plant, and like it, all parts of the tree are toxic— tree, sap, and latex. Those who tap the tree must wear gloves and protective clothing. The active irritant is urushiol, a catechol derivative. 

The oriental lacquer is prepared from the sap of the varnish tree" Rhus verni-ciflua, which is an emulsion of an aqueous phase and an organic phase called urushi-ol. The urushi fraction consists of a mixture of catechol derivatives substituted in 3-po-sition with aliphatic C- 5 or C- 7 side chains. About 60% of these side chains are trie-nes. The structure of the trienes is similar to that in linseed or tung oil and is essential for the effectiveness of the oxidative curing of oriental lacquer. We have utilized new techniques and used combinations of modern techniques to analyze the urushiol mixtures and to characterize and identify each individual compound. We have also developed ultraviolet stabilizers for oriental lacquer, stabilizers that could be incorporated into the polymerizing mixture during the curing process to result in ultraviolet stabilized oriental lacquer. 

In addition, especially in the processed urushi samples, peaks with masses [M]K" =665 daltons and [M]K" =667 daltons which are the expected products of the dimerization reaction by oxidation of the phenol part of the catechol derivatives of urushiol. Supercritical fluid chromatography in combination with electron bombardment mass spectrometry was then used for the identification of some of the major components of the urushiol samples. Most prominently were found the trienes with [M]=314 daltons, and [M]=317 daltons and the monoenes. Again the compound with the mass of [M]=332 daltons was noticed which was the water adduct of the triene [M]=314 daltons. 

We have made it our objective to develop UV stabilizers that could be added to urushi and "cocured" to obtain a photo-stabilized oriental lacquer. We have synthesized several 2(2-hydroxyphenyl)2H-benzotriazole UV stabilizers, stearic, oleic, linoleic and linolenic acid esters of 2[2-hydroxy-3-tert-butyl-5(3 -hydroxypropyl)-phenyl]2H-benzotriazole [Equation] [7]. The compounds, pale yellow oils were characterized by their UV and K IDS mass spectra [Figure 6] [7]. All four compounds showed nearly identical UV spectra with two maxima at 305 and 340 nm. Those UV stabilizers have aliphatic side chains that are by six carbon atoms longer than the carbon side chains of the catechol derivatives of the urushi components. The unsaturated esters, especially the linolenic ester could readily be incorporated into urushiol or drying oil compositions and the unsaturated esters can be "co-cured" into UV stabilized oriental lacquer films. They could also be added to linseed oil and cured into films of drying oils. 

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