Dimeric anthraquinone pigments

CHCI3). A member of a group of unusual dimeric anthraquinone pigments from the mycelium of the Tasmanian agaric Dermocybe canaria (Basidiomycetes). Some preanthraquinones of the same type occur in Cortinarius sinapicolor and Australian Dermocybe species. 

Stereochemical Studies on Pre-Anthraquinones and Dimeric Anthraquinone Pigments... 

For example, chrysotalunin (33), an anthraquinone dimer, is a red pigment which occurs in many soils worldwide (McGrath, 1967 Foo and Tate, 1977 Fujitake... 

Dimeric pre-anthraquinones probably are formed by initial phenolic coupling of two dihydroanthracenone units. The sites in the respective aromatic nucL i at which this coupling occurs form the basis for the classification of pigments followed below. 

Oxidative dimerisation at the dihydroanthracenone level may be followed by enzymatic or chemical modifications which transform portions of the molecule into anthrone or anthraquinone moieties. The majority of th( dimers is present in the form of their di-, tri- or tetra-O-methyl ethers, in which case the pigments become more stable as the methylation increases. Ultimately, bianthraquinones may result and these compounds too are conveniently included in this section. 

The stereochemical complexity and chemical sensitivity of many dimeric pre-anthraquinones makes them less amenable to chromatographic identification than the anthraquinones themselves. Consequently, they have proved somewhat more difficult to use for the taxonomy of Phlegmacium (118, 265, 371, 509, 515, 617) than have the anthraquinones to the systematics of Dermocybe. Chemical instability of many pigments causes marked colour changes when sporophores of certain Phlegmacium species are stored in the herbarium (617),... 

Besl and Bresinsky 86) discovered in Leucopaxillus tricolor (Tri-cholomataceae), besides endocrocin (303), two yellow pigments which bore superficial resemblances to asperflavin (329) and to phlegmacin (371). Closer chemical investigations, however, have revealed that these substances represent a new type of dimeric pre-anthraquinone 94,515). 

The quinones are a rather heterogeneous collection of compounds with structures based on an unsaturated system of cyclic diketones. The biologically important plastoquinones, ubiquinones, and vitamin K are included in this group however, as pigments the most widespread and important quinones are the 1,4-naphthaquinones (Fig. 18) and the 9,10-anthraquinones (Fig. 19, Table 10). Methyl, methoxyl, and hydroxyl groups are the most common substituents, and O- and C-glycosides (see Fig. 20) are frequently present in the anthraquinone group. Several structural modifications exist due to reduction, dimerization (Fig. 21), and addition of side chains. 

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