Of polyporic acid

The dimethoxy derivative of polyporic acid, betulinan A (4), is another of the few known />-terphenyls with unsubstituted side rings. It has recently been isolated from fruiting bodies of Lenzites betulina, together with the related betulinan B (113, see Section 4.1) [27], Betulinan A and B are potent inhibitors of lipid peroxidation in rat liver microsomes (thiobarbituric acid method), and 4 showed the highest activity (IC50 = 0.46 pg/mL). 

The structure of the 4,3 ,4 -trihydroxy derivative of polyporic acid was assigned in 1942 by Akagi to the brown pigment leucomelone (47) isolated from the black edible mushroom Polyporus leucomelas (.Boletopsis leucomelaena) collected in Japan [68], From the same fungus, Akagi obtained also a colourless compound named protoleucomelone (48), established as the leuco-peracetate of 47. 

Among the early synthetic works, we wish to mention here the synthesis of polyporic acid (3) [115] and thelephoric acid (82) [78]. As summarised in Scheme 3a, several terphenylquinones have been synthesized with moderate yields starting from 2,5-dichlorobenzoquinone by arylation with V-nitrosoacetanilides or diazonium salts and subsequent alkaline hydrolysis. This method allowed preparation of symmetrical and unsymmetrical terphenylquinones, this latters with low yields. 

The authors investigated the possible relationship between poisoning due to ingestion of H. rutilans and DHO-DH inhibiton by 3, and concluded that the intoxication symptoms are due to the high content of polyporic acid. 

A further family of aromatic compounds produced by lichens is derived from shikimic add via phenylalanine and is exemplified by vulpinic acid (7.55), which was isolated from Letharia vulpina. Vulpinic acid has been synthesized by the lead tetra-acetate oxidation of polyporic acid. Lichens also produce some alkylated citric acid derivatives such as lichesterinic acid (7.56) and some sterols. 

C gH 204, Mr 292.29, bronze-colored plates, mp. 310-312°C. P. forms red solvates from pyridine and yellow solvates from dioxan it has the parent skeleton of the terphenylquinones. P. is found in some tree fungi of the order Aphyllophorales and in the frondous lichen Sticta coronata. The cinnamon-colored fruit bodies of Hapalopilus rutilans consist of up to 43.5% dry weight of polyporic acid. P. is formed biosynthet-ically by condensation of two molecules of phenyl-pyruvic acid and exhibits weak antileukemic activity. The dimethylether is called betulinan A . 

Stahlschmidt (59/, 592), Thorner (653, 654), Zellner (726), and ZoPF (732). Much of the chemistry which emerged from these pioneering studies has been reviewed in the older literature (//2, J74, 363, 424, 519). The elucidation of the structures of polyporic acid and atro-mentin by Kogl (423, 425, 426, 431, 433) represented a significant advance in this field but later work by this author, principally on bole-toT (427, 428), muscarufin (429) and the structure of thelephoric acid (430), has unfortunately not withstood the test of time and meanwhile has caused considerable confusion. 

The isolation of polyporic acid (11) [Stahlschmidt, 1877 (597, 592)], atromentin (13) [Thorner, 1878 (653)] and thelephoric acid (16) [ZOPF, 1889 (730)] marked the start of the chemical investigation of fungal pigments. The structure elucidation and chemistry of these compounds has been amply covered in Thomson s book (655) and does not need to be repeated here. In recent years several papers dealing with ultraviolet (311), infrared (208) and mass spectra (304, 465) and with the chromatography (267) and detection (274) of simple terphenyl-quinones have been published. Details of their known distribution in fungi are given in Table 3 and their physical properties are summarised in Table 4. 

The structures of phlebiarubrone (23) and its dihydroxy derivative (25) were confirmed by synthesis involving methylenation of the potassium salts of polyporic acid (11) and atromentin (13), respectively, with methylene sulphate in the presence of sodium bicarbonate (22,... 

Hapalopilus rutilans Brown - purple Ionisation of Polyporic acid (11)... 

JiRAWONGSE, V., E. Ramstad, and J. Wolinsky Isolation of Polyporic Acid from Lopharia papyraceae. J. Pharm. Sci. 51, 1108 (1962). 

Wilkins (1979) studied the MS of di- and tri-oxygenated stictane triterpenoids and their trimethylsUyl derivatives. A paper by Grigsby et al. (1974) deals with the MS of derivatives of polyporic acid, and Krause (1976) investigated the MS fragmentation of depsides, depsidones, usnic acid, terpenoids, fatty acids, di- and triglycerides and carbohydrates from lichens. Some papers deal with the MS of usnic acid and derivatives Kutney et al. (1974), Huneck and Schmidt (1980), and Schmidt et al. (1981). Ruef (1990) reported on the MS of numerous lichen xanthones. 

Deriv Diacetylpolyporic acid, yellow needles (benzene), mp 212 °C, by acetylation of polyporic acid with AcjO-pyridine StL Pseudocyphellaria coronata (Mull.Arg.) Malme... 

Grigsby RD, Jamieson WD, Mclnnes AG, Maass WSG, Taylor A (1974) The mass spectra of derivatives of polyporic acid. Can J Chem 52 4117-4122 Grove JF, Mac Millan J, MulhoUand TPC, Zealley J (1952) Griseofulvin. Part III. The structures of the oxidation products C9H9O5CI and C14H15O7CI. J Chem Soc 3967-3977... 

Burton JF, Cain BF (1959) Antileuksemic activity of polyporic acid. Nature 184 1326-1327 Cain BF (1966) Potential anti-tumour agents. IV. Polyporic acid series. J Chem Soc Perkin 11 1041-1045... 

Grigsby RD, Jamieson WD, Mclnnes AG, Maass WSG, Taylor A (1974) The Mass Spectra of Derivatives of Polyporic Acid. Can J Chem 52 4117... 

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