Rhizocarpic acid

Alectorialic acid Rhizocarpic acid y-Carotene Mutatoxanthin Methyl 3,5-dichlorolecanorate Acetyltylolupenol B Vittatolic acid 25-Acetoxy-20(S),24(R)-epoxy-dammaran-3 3-ol p-Amyrone Ovoic acid Tenuiorin Crustinic acid Tetrahydroxyfatty acids Camphor Conorlobaridone Protosiphulin 9-Methyl 4-hydroxypannarate Pseudoplacodiolic acid I -Chloronephroarctin Subpaludosic acid p-Carotene... 

Deriv Rhizocarpic acid methyl ether, pale cream needles (n-hexane), mp 139-140.5 °C, from rhizocarpic acid with CHjNj in EtjO StL Rhizocarpon geographicum (L.) DC. 

Although the pulvinic acid amide derivatives rhizocarpic acid and epanorin (58) could originate from simple coupling between the appropriate amino acid and the pulvinic acid, Maass (66) has proposed a direct route to pulvinamide itself (viz 58, R = H), involving condensation between phenylalanine and phenylpyruvic acid. 

Studies have also demonstrated that the production and/or content of secondary metabolites in lichens varied with changes in elevation. For example, it has been reported for Umbilicaria americana that lichen secondary metabolite production decreases with increasing elevation (Swanson et al. 1996). In contrast, Rubio et al. (2002) found increasing levels of rhizocarpic acid in Acarospora schleicheri with increasing elevation. The direct effects of elevation on the production of phenolic compounds by lichens may in fact be complicated by the dynamic interaction of various environmental factors. 

Only two terphenylquinones, polyporic acid and thelephoric acid, are known, while pulvinic acid derivates are more numerous (calycin, epanorin, leprapinic acid, leprapinic acid methyl ether, pinastric acid, pulvinic acid, pulvinic dUactone, rhizocarpic acid, stictaurin, vulpinic acid). 

Acarospora chlorophana has been found to exist in two chemical races (777), one producing ( —)-acaranoic acid (71) and (— )-acarenoic acid (73) in addition to rhizocarpic acid, and the other with ( + )-roccellic acid (76) and rhizocarpic acid. Acarospora oxytona (177) however produces rhizocarpic acid and (+ )-lichesterinic acid (77). The acids (71), (73), (76) and (77) have the same chirality at C-2 and C-3 and this circumstantial evidence led Huneck (777) to propose the biogenetic pathway outlined in Scheme 9, elaborating that proposed earlier by Mosbach (244). 

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