Pigments pulvinic acids

Simple alkylated polyhydroxyterphenyls like penioflavin (114), isolated from Peniophora sanguinea, can be derived formally from a C-18 terphenylquinone as precursor and subsequent formation of a new carbon-carbon bond [94]. The biosynthesis of xylerithrin (118) and related pigments from P. sanguinea, according to the studies of Von Massow [113, 114], requires the insertion of a third unbranched phenylpropanoid unity on a pulvinic acid intermediate derived from a terphenylquinone, as indicated in Scheme 2. 

Tryptophan and its relative indolylpyruvic acid (3.42) have been shown to precursors of hinnuliquinone (3.41), which is a pigment of Nodulisporium hin-nuleum. Typical of many fungal indoles in which alkylation by a dimethylallyl or isopentenyl group has occurred, mevalonate was also a precursor. However, the stage at which prenylation of a monomer or a dimer took place was unclear. Asterriquinone (3.43) from Aspergillus terreus and cochliodinol (3.44) from Chaetomium cochliodes are similar metabolites. Fission of the hydroxyquinone in the latter followed by lactonization leads to cochliodinone (3.45) in a sequence that is similar to that which inter-relates the terphenyls and pulvinic acids described in Chapter 7. 

Cleavage of the hydroxyquinone ring system and relactonization affords another series of pigments known as the pulvinic acids, which may be exemplified by gomphidic acid (7.23). The dry-rot fungus, Serpula lacrimans, produces xerocomorubin (7.24), which is another example. These pulvinic acid moieties form part of a complex group of metabolites known as the badiones. They are... 

Screening pigments Pulvinic dilactone Pulvinic acid derivative 1672 1405 >246 290 367 431 422... 

Potassium hydroxide, 20, 239, 303-304 Potassium persulfate, 274 Potassium superoxide, 304-307 Potassium tri-sec-butylborohydride, 307 Prins reaction, 159 Progesterone, 107 Proline, 10, 307 1,3-Propanediol, 37 Propargylic alcohols, 8, 53 Propargylic chlorides, 155 (E)-Propenyllithium, 141 Propiolaldehyde diethyl acetal, 79-80 Propiolamidium salts, 124 Fropiolate esters, 8 Propiolic add, 295 Propylene carbonate, 74 Propylene oxide, 74 Protolichesterinic add, 412 Pterocarpins, 114 Pulegone, 287, 288, 308-309 tosylhydrazones, 375-376 Pulvinic acid pigments, 291 Pumiliotoxin, 28... 

Dehydration. British chemists have developed a total synthesis of un-symmetrical pulvinic acid pigments of lichens and fungi. The method is illustrated for the synthesis of the permethylated derivative of gomphidic acid (4), the... 

The hydroxylated pulvinic acids such as variegatic acid (73) may be characterised in the form of their dilactone peracetates, e.g. (75) (Scheme 10), which exhibit sharp melting points, in contrast to the parent pigments, and give rise to diagnostic infrared absorption above 1800 cm 73). Dilactone formation also occurs on electron impact and the mass spectral fragmentation of pulvinic dilactones has proved valuable in structural elucidation 452, 453, 607, 608). On treatment with diazomethane the hydroxypulvinic acids are converted into the... 

Alternatively, the pulvinone nucleus of pigment (115) could derive via oxidative decarboxylation of the hypothetical intermediate (9) already implicated in the biosynthesis of grevillins, terphenylquinones (and hence pulvinic acids), and the pigment (10). 

Badione-A is accompanied in the cap skins of X. badius by the closely related pigments norbadione-A (127), bisnorbadioquinone-A (128) and pulviquinone-A (129). The structures of these naphthalenoid pulvinic acids followed from detailed analysis of the H- and C-n.m.r. spectra and from their close chemical and spectroscopic relationship... 

The postulated chemotaxonomic link between Sclerodermataceae and Boletales is further strengthened by the detection of sclerocitrin-D (141), a terphenylquinone analogue of the naphthalenoid pulvinic acids, in Scleroderma citrinum (250). The pigment has been isolated in the form of its yellow nonamethyl derivative by permethylation of the complex mixture of closely related pigments which are to be found... 

In Polyporus tumulosus, the pigment (245) co-occurs with hydroxy-lated phenylacetic acids 173, 535) from which it may be derived biosyn-thetically. In Serpula lacrimans and in Paxillus statuum the formation of (245) by degradation of a pulvinic acid may be suggested. 

It is of intenjst to note in passing the occurrence in various Chaeto-mium species (133, 394), and elsewhere among the lower fungi (724), of analogues of the terphenylquinone (Section 2.1.2) and pulvinic acid pigments (Section 2.1.3) which derive not from phenylalanine or from tyrosine but from tryptophan. 

Synthesis of the Pulvinic Acid Pigments of Lichen and Fungi. Chem. Commun. 

Knight DW, Pattenden G (1979) Syntheses of per-methylated derivatives of pinastric acid and gamphidic acid, pulvinic acid pigments of lichen and fungi. J Chem Soc Perkin Trans 1 84-88... 

Formulation (43) shows the basic pulvinic acid carbon skeleton, and all known natural pulvinic acids show variations which include either hydroxylation of methoxylation of the benzene rings or lactonisations involving the carboxy function (Table 2). In addition, a few methyl ester and amide derivatives of the acids occur naturally. Early studies of the constitutions of pulvinic acids found in lichens have been summarized by Dean (7), and a useful account of pigments found in mushrooms, which includes pulvinic acid pigments, has been presented recently by Steglich 47). 

The group of 4-ylidenetetronic acid pigments known as pulvinones are closely related to the pulvinic acids and possess the general structure (60). It is interesting that pulvinones have only very recently been... 

Carbon-14 work has shown that the pulvinic acid pigments found in lichens are derived via the shikimic acid pathway, and that the unsaturated ylidenebutenolides found with polyacetylenic compounds in the Compositae are derived from oleic acid. No biosynthetic studies have been reported for the terpenoid ylidenebutenolides freelingyne, peridinin and the several sesterterpenes from marine sponges. 

Knight, D. W., and G. Pattenden Synthesis of the Pulvinic Acid Pigments of Lichen and Fungi. Chem. Commun. 660 (1976). 

Steglich, W., H. Besl, and K. Zipfel Pigments of Fungi XIX. Structural Determination of Pulvinic Acids by NMR Spectroscopy. Z. Naturforsch. 29b, 96 (1974). 

Asano, M., and S. Huziwara Lichen Pigments of the Pulvinic Acid Series. VI. Synthesis of Atromentinic Acid. J. Pharmac. Soc. Japan 59, 675 (1939). 

Polyporic acid is biosynthesised by condensation of two molecules of phenylpyruvic acid in the shikimate pathway via the intermediate 2,5-diphenyl-3-hydroxy-4-oxohex-2-enoic acid and by oxidation of the resulting hydroquinone. Terphenylquinones are transformed by enzymatic reactions into pulvinic acids and many other products, some of which are also characteristic pigments of lichens and fungi. 

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