Pyrogallol derivatives

Xanthotoxin, Cj HgO, is isomeric with bergaptene, and is present in the oil of Fagara xanthoxyloides. It is a solid compound, melting at 145° to 146°, and is a pyrogallol derivative, having the constitution—... 

In situ quantitation The absorption photometric analysis in reflectance was carried out either at the absorption maximum of the pyrogallol derivative at = 350 nm (Fig. lA) or at the absorption maximum of the phloroglucinol derivative at = 420 nm (Fig. IB). 

Synthetic antioxidants are safer, cheaper and purer than natural antioxidants but, nevertheless, the majority of consumers still prefer natural antioxidants. This trend will surely persist in the near future. The mechanisms for the changes of synthetic antioxidants are well known, but the same cannot be stated in the case of natural phenolic antioxidants. They are usually pyrocatechol or pyrogallol derivatives, where the changes during oxidation could be different from those of synthetic antioxidants, which are mostly 1,4-substituted. 

Table III. Molar Absorptivity in the Total Phenol Assay and Precipitability with Acidic Formaldehyde Pyrogallol Derivatives...

Namely, these series show that monophenols react according to their oxidizability, catechols react similarly except twice as much (presumably via o-quinone production), and pyrogallol derivatives generally react as catechols if vicinal hydroxyls are free and as monophenols if not. Ellagic acid appears perhaps anomalous, but it is known that two of the four hydroxyls are considerably more acidic than the other two (II). 

Most pyrogallol derivatives did not precipitate either (Table III). A small precipitation occurred with pyrogallol (which may be considered as a hydroxyresorcinol) and it reacts with vanillin/HCl also (7). However, any additional substitution eliminates this reactivity, e.g., gallic acid (Table IV). Purpurogallin did precipitate with formaldehyde. It is not very soluble in the reaction mixture, and it is a tropolone. Structures of this type might interfere, but in tea and probably in wine the known tropolone derivatives are flavonoids (I, 25). 

Many patents have been issued on the use of pyrogallol derivatives as pharmaceuticals. Pyrogallol has been used externally in the form of an ointment or a solution in the treatment of skin diseases, eg, psoriasis, ringworm, and lupus erythematosus. Gallamine triethiodide (16) is an important muscle relaxant in surgery it also is used in convulsive-shock therapy. Trimethoprim (2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine) is an antimicrobial and is a component of Bactrin and Septra. Trimetazidine (l(2,3,4-trimethoxybenzyl)piperazine (Vastarel, Yosimilon) is used as a coronary vasodilator. l,2,3,4-Tetrahydro-6-methoxy-l-(3,4,5-trimethoxyphenyl)-9.H-pyrido[3,4- ]indole hydrochloride is useful as a tranquilizer (52) (see HYPNOTICS, SEDATIVES, anticonvulsants, and anxiolytics). Substituted indanones made from pyrogallol trimethyl ether depress the central nervous system (CNS) (53). Tyrosine-and glycine(2,3,4-trihydroxybenzyl)hydrazides are characterized by antidepressant and anti-Parkinson activity (54). 

Figure 2.17. Infrared spectra of the synthesized FA (MW > 1000 Da) in the Mn(IV) oxide-pyrogallol system and the FA extracted from a Borosaprist (Terric Humisol). Reprinted from Wang, M. C., and Huang, P. M. (2000). Characteristics of pyrogallol-derived polymers formed by catalysis of oxides. Soil Sci. 165, 737-747, with permission from Lippincott Williams Wilkins.

Wang, M. C., and Huang, P. M. (2000a). Characteristics of pyrogallol-derived polymers formed by catalysis of oxides. Soil Sci. 165,737-747. 

Fig. 8-16. Reaction of pyrogallol-derived free radicals with glycine (Wang and Huang, 1987).

Tetrahalogenocyclohexanones can also be dehydrohalogenated, hydrolysed and tautomerised to pyrogallol derivatives although the yields are only in the region of 20% (ref.4). 

Pyrimidines la 266,438,439 lb 32,430 Pyrimidine nucleoside derivatives lb 290 Pyrocatechol lb 170,172,185 -, 4-rerr-butyl- lb 201 Pyrocatechol derivatives lb 119 Pyrocatechol violet reagent la 398 Pyrogallol lb 383,399,400 Pyrogallol derivatives lb 312 Pyrolysis of organic substances la 92,96 a-Pyrone derivatives la 288 lb 387,388 Pyrrole lb 268,270 Pyrrole alkaloids la 66 lb 279 Pyrrole derivatives la 266.269,270 lb 63 Pyrrolidine derivatives lb 290 Pynolizidine alkaloids lb 243,246,291... 

Yamamoto and Ishihara et al. developed enantioselective polyene cyclization with predictable absolute configurations and excellent enantioselectivities using the chiral LBA (Scheme 10.23) [45]. They further succeeded in produdng new chiral LBA consisting of chiral pyrogallol derivatives and SnCU, which effedively promotes the cyclization of 2-geranylphenol derivatives (Scheme 10.24) [46]. 

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