Xerocomic acid

Boletes bruising yellow - deep blue Variegatic acid, Xerocomic acid... 

C (decomp.). A pulvinic acid derivative from the mushroom Gomphidius glutinosus (Basidio-mycetes). Together with xerocomic acid G. is responsible for the yellow color of the stem base. 

CIgH12O5, Mr 308.29, orange prisms, mp. 216- 217 °C. A pigment of numerous lichens. The biosynthesis proceeds from polyporic acid. The methyl ester of R, vulp(in)ic acid, is a typical lichen acid. Hydroxylated P. derivatives are important mushroom pigments, e. g., gomphidic acid, variegatic acid, and xerocomic acid the latter two compounds are responsible for the typical blue color reaction of many Boletus and Xero-comus species on bruising the fruit bodies. 

C15H14O5, Mr 322.32, yellow cryst., mp. 148-149°C (other reports 145-146 °C), soluble in chloroform. A typical lichen acid, e. g., in Letharia vulpina. V. a. also occurs in some mushrooms of the order Boletales. Saponification of V. a. affords pulvinic acid (see also gomphidic acid, xerocomic acid). V. a. has antibacterial as well as antiviral activities and inhibits the growth of plants. V. a. is used in some countries as a natural dye for wool. ... 

Hydroxylated pulvinic acids are responsible for the yellow and red colours of most boletes. They also cause the characteristic blueing of the flesh which occurs when the fruit bodies of many species are cut or bruised. Because the distribution of the hydroxylated pulvinic acids such as variegatic acid (73) and xerocomic acid (72) is restricted to the order Boletales, their isolation from Gomphidius 608), Omphalotus 128, 397, 584), Hygrophoropsis 91, 126, 127, 198), Coniophora 86,... 

Table 10. Data for Xerocomic Acid (72) and Isoxerocomic Acid (84) (S values,...

As can be anticipated from the relative position of the catechol ring and the enolic hydroxy group only xerocomic acid (72) could... 

Besides atromentic acid, xerocomic acid, and variegatic acid a number of less common pulvinic acid derivatives have been isolated from Basidiomycetes (Table 11). 

The fruiting bodies of Pulveroboletus auriflammeus collected in Japan contain a series of extensively methylated atromentic acid and xerocomic acid derivatives, several of them in chlorinated form 474). The presence of traces of a chlorinated xerocomic acid had been noted before in sporophores of Xerocomus chrysenteron 607). 

Most of the hydroxylated pulvinic acids from Basidiomycetes were first synthesised (7i, 200, 607, 608, 609) using the classical methods of VoLHARD 687) and Asano (52). For unsymmetrically substituted pulvinic acids such as xerocomic acid (72) the procedure is shown in Scheme 12 202). The use of sodium hydride as base in the second condensation step is recommended ( ) in order to reduce contamination of the dinitrile (99) with symmetrical by-products which arise via retro-aldol processes when sodium ethoxide is used. This route has also been followed for the synthesis of " C-labelled compounds 514). 

In the cases of xerocomic acid and gomphidic acid the classical route afforded mixtures of the natural pigments and their regioisomers. Edwards and Gill 202) were able to separate the mixture of (72) and (84) obtained from the dilactone (100) by fractional crystallisation. Interestingly, when the mixture of (72) and (84) was heated with hy-droiodic acid in acetic acid for longer than one hour exclusive formation of xerocomic acid (72) was observed. 

Ramage and coworkers (537) have developed a biomimetic synthesis of pulvinic acids which relies for its success on the facility with which dioxolanones of type (110) undergo nucleophilic attack at the lactone carbonyl group with subsequent extrusion of cyclohexanone. In the synthesis of xerocomic acid (Scheme 15) the dioxolanone (110), obtained as the predominant isomer from reaction between the phos-phorane (109) and methyl (3,4-dibenzyloxyphenyl)glyoxalate, was cleaved with the lithium enolate of /-butyl (4-benzyloxyphenyl)acetate. The intermediate dianion (111) probably exists at first as the chelate (112) which is then broken down on aqueous work up and subsequently cyclised specifically at the less hindered carbonyl group to produce the ester (113). The dianion (111) is analogous to the hypothetical... 

Xerocomic acid exhibits moderate antibiotic activity against several bacteria 533, but compare 76). In recent years numerous pulvinic acid derivatives have been synthesised, and many have been shown to possess useful anti-inflammatory properties 710). 

The biosynthesis of badione-A seems to occur via oxidative dimer-isation of xerocomic acid (72). The feasibility of this hypothesis has been demonstrated in vivo by applying an aqueous solution of xerocomic acid to the cap of Xerocomus badius from which part of the... 

Boletus spp., Xerocomus spp., Suillus variegatus and other boletes (Table 8) Yellow - blue Variegatic acid (73) and/or Xerocomic acid (72) - Anions of the type (77) (Scheme 10)... 

Variegatic and xerocomic acids co-occur with atromentic acid (57) in Xerocomus chrysenteron 56), and atromentic acid has also been isolated from cultures of the mushrooms Paxillus atrotomentosus 61), Clitocyre illudens 64) and Leccinum aurantiacum 65). 

Beaumont, P. C., and R. L. Edwards Constituents of the Higher Fungi, Part XI. Boviquinone-3(2,5-Dihydroxy-3-farnesyl-l,4-benzoquinone), Diboviquinone-3,4, Me-thylenediboviquinone-3,3, and Xerocomic Acid from Gomphidius rutilus Fr. and Diboviquinone-4,4 from Voletus (Suillus) bovinus (Linn ex Fr.) Kuntze. J. Chem. Soc. (C) (London) 2582 (1971). 

In a series of reports, banger s group studied the synthesis of pulvinic acids via a TMSOTf-catalyzed [3-f2] cyclization of l,3-bis-(trimethylsilyloxy)-l,3-dienes (e.g., 83) with oxalyl chloride followed by Suzuki couphng of product triflates (Scheme 1.11) [64]. banger s versatile method was apphed to the synthesis of almost all natural pulvinic acids (e.g., xerocomic acid 29), including norbadione A (37) by be Gall et al. [65]. In a modification of banger s protocol, Mioskowski dimerized simple silyl ketene acetals (e.g., 85) to obtain symmetrical pulvinic acids via an uncatalyzed reaction with (COCl)2 (Scheme 1.11) [66]. 

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