Gomphidic acid

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... 

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... 

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. ... 

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. 

Synthesis of Permethylated Derivatives of Pinastric Acid and Gomphidic Acid,... 

In 1991, Pattenden exploited the inherent regioselectivity of nucleophilic additions on P-methoxy maleic anhydrides to prepare gomphidic acid (30) by two different routes (Scheme 1.10) [63]. The first one involves an HWE reaction between phosphonate 80 and aryl pyruvate 81 [63b], and the second one is based on a Reformatsky-type reaction of 77 with zinc enolates derived from aryl acetate 79 [63cj. 

Scheme 1.10 Total syntheses of gomphidic acid by Pattenden.

Knight, D. W., and G. Pattenden Syntheses of Permethylated Derivatives of Pinastric Acid and Gomphidic Acid, Pulvinic Acid Pigments of Lichen and Fungi. J. Chem. Soc. (London) Perkin Trans. I 1979, 84. 

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