Phenolics birch

HPLC method with amperometric detection was applied for detenuination of phenols in sea sediment and some dmg preparation. Peaks of phenol, guaiacol, cresols, hydroquinon and resorcinol were identified on chromatogram of birch tai. The HPLC method with electrochemical detectors was used for detenuination of some drug prepai ation of aminophenol derivate. So p-acetaminophenol (paracetamol) was determined in some drug. 

For a particular phenol, the authors required a protective group that would be stable to reduction (by complex metals, catalytic hydrogenation, and Birch conditions) and that could be easily and selectively removed. 

A carbonyl group cannot be protected as its ethylene ketal during the Birch reduction of an aromatic phenolic ether if one desires to regenerate the ketone and to retain the 1,4-dihydroaromatic system, since an enol ether is hydrolyzed by acid more rapidly than is an ethylene ketal. 1,4-Dihydro-estrone 3-methyl ether is usually prepared by the Birch reduction of estradiol 3-methyl ether followed by Oppenauer oxidation to reform the C-17 carbonyl function. However, the C-17 carbonyl group may be protected as its diethyl ketal and, following a Birch reduction of the A-ring, this ketal function may be hydrolyzed in preference to the 3-enol ether, provided carefully controlled conditions are employed. Conditions for such a selective hydrolysis are illustrated in Procedure 4. 

Occasionally we have found iron contaminants in aromatic steroids that have not been adequately purified. The methylation of a phenolic steroid with methyl sulfate and alkali is often carried out just prior to a Birch reduction and iron in the tap water precipitates with the steroid during the... 

Direct Electron Transfer. We have already met some reactions in which the reduction is a direct gain of electrons or the oxidation a direct loss of them. An example is the Birch reduction (15-14), where sodium directly transfers an electron to an aromatic ring. An example from this chapter is found in the bimolecular reduction of ketones (19-55), where again it is a metal that supplies the electrons. This kind of mechanism is found largely in three types of reaction, (a) the oxidation or reduction of a free radical (oxidation to a positive or reduction to a negative ion), (b) the oxidation of a negative ion or the reduction of a positive ion to a comparatively stable free radical, and (c) electrolytic oxidations or reductions (an example is the Kolbe reaction, 14-36). An important example of (b) is oxidation of amines and phenolate ions ... 

The isolated double bonds in the dihydro product are much less easily reduced than the conjugated ring, so the reduction stops at the dihydro stage. Alkyl and alkoxy aromatics, phenols, and benzoate anions are the most useful reactants for Birch reduction. In aromatic ketones and nitro compounds, the substituents are reduced in preference to the Dissoiving-Memi... 

In Table 15 are recorded the dissociation constants of certain phenolic compounds. From these data it becomes obvious that the introduction of aldehyde groups, or other substituents, changes the dissociation constant of phenolic hydroxyls by over one-hundred fold. Moreover, oxidation studies carried out in this laboratory have shown that the native lignins from bagasse, white Scots pine and birch contain... 

The nutritional value of the diet influences the ability of herbivores to detoxify plant secondary metabolites (Schwass and Finley, 1985). For instance, voles in winter have to consume the bark of birch Betula sp.). This causes stress and leads to poor growth and high mortality among young animals. Birch bark contains phenolics and terpenoids. Both are metabolized by cytochrome P450 monooxidases in phase I and conjugated with glucuronic acid in phase II. 

Differences in digestive ability can reflect different ecological lifestyles of related species. The mountain hare feeds on hirch in winter and grass in summer. when fed birch that is high in phenolics, the hare suffers no sodium loss but detoxifies instead. The European hare does not eat birch in winter but eats grass year round. When forced to eat a high-phenolic diet, it loses much sodium through its urine (lason and Palo, 1991). 

Palo, R. T., Pehrson, A., and Knutsson, D. G. (1983). Can birch phenolics be of importance in the defense against browsing vertebrates Finnish Game Research 41,75-80. 

Palo, R. T., Sunnerheim, K., and Theander, 0.(1985). Seasonal variation of phenols, crude protein and cell wall content of birch Betulapendula Roth.) in relation to ruminant in vitro digestibility. Oecohgia 65,314—318. 

Sunnerheim, K., Palo, R. T., Theander, 0., and Knutsson, P. G. (1988). Chemical defense in birch. Platyphylloside a phenol from Betula pendula inhibiting digestibility. Joamfll of ChemicalEcobgy 14,549. 

Laitinen, M.-L., Julkunen-Tiitto, R., and Rousi, M., Foliar phenolic composition of European white birch during bud unfolding and leaf development. Physiol. Plant., 114, 450, 2002. 

Early Synthesis. Reported by Kolbe in 1859, the synthetic route for preparing the acid was by treating phenol with carbon dioxide in the presence of metallic sodium (6). During this early period, the only practical route for large quantities of salicylic acid was the saponification of methyl salicylate obtained from the leaves of wintergreen or the bark of sweet birch. The first suitable commercial synthetic process was introduced by Kolbe 15 years later in 1874 and is the route most commonly used in the 1990s. In this process, dry sodium phenate reacts with carbon dioxide under pressure at elevated (180—200°C) temperature (7). There were limitations, however not only was the reaction reversible, but the best possible yield of salicylic acid was 50%. An improvement by Schmitt was the control of temperature, and the separation of the reaction into two parts. At lower (120—140°C) temperatures and under pressures of 500—700 kPa (5—7 atm), the absorption of carbon dioxide forms the intermediate phenyl carbonate almost quantitatively (8,9). The sodium phenyl carbonate rearranges predominately to the 07 0-isomer, sodium salicylate (eq. 8). 

Over a period of a month, tanning coefficients increased dramatically, and seasonal (2 month) increases in hydrolyzable tannins were observed in trees undergoing defoliation. Preliminary studies of yellow birch and sugar maple suggest that day-to-day responses in phenolic production may be generated by damage to leaves (39). 

Catalytic hydrogenation of benzo [6]thiophene (mainly to ethylbenzene) has been studied in the presence of a molybdenum trisulfide catalyst.40 Birch reduction of benzo[6]thiophene 428 429 and its 5-methyl derivative428 affords 2-ethyl- and 2-ethyl-4-methylthio-phenol, respectively. 

The phenolic hydroxy group is deprotected in the course of the Birch reduction, so it must again be protected. 

Since the phenolic hydroxy group is deacetylated during the Birch reduction it must once again be acetylated in a third step. 

---