Pannaric acid

Condidymic acid (256), pannaric acid (259), schizopeltic acid (112), and di-O-methylstrepsilin (145) have been synthesized. 

CigHisO, Mr 344.32, yellow prisms, mp. 203 °C, [a] +495° and -495° (CHCl,), respectively. A biologically highly active dibenzofuran derivative, occurring both as the (+)- and the (-)-forms in numerous lichens (especially in Usnea species) antibiotic, antileukemic, growth regulatory (in plants), and antifeedant (in insects) activities have been described. It is used as the free acid and as the sodium salt in pharmaceutical preparations. The biosynthesis presumably proceeds via phenolic oxidation. Other dibenzofuran derivatives from lichens are didymic acid, pannaric acid, pla-codiolic acid, and schizopeltic acid. 

Elix JA (1972) Annelated fiirans. VIII. A synthesis of pannaric acid. Aust J Chem 25 1129-1133... 

Elix JA, Pratt SJ, Laundon JR (1990e) A synthesis of the lichen dibenzofuran pannaric acid 6-methyl ester. Aust J Chem 43 2107-2111... 

The synthesis of the lichen dibenzofuran pannaric acid (470) from pannarol (471) was reported by Elix 110) (Scheme 59). Pannarol has been synthesized via a mixed Ullmann reaction and subsequent hydrobromic acid induced cyclisation of the unsymmetrical biphenyl separated from the mixture of three products (2). Pannarol (471) was methylated and then acetylated to yield a mixture of 2,6-diacetyl-3,9-dimethoxy-l,7-dimethyl-dibenzofuran (472) and 4,6-diacetyl-3,9-dimethoxy-l,7-dimethyldibenzo-furan (473), which were separated by preparative t.l.c. The major product (472) was then oxidized and demethylated to yield pannaric acid (470). 

Akermark, B., H. Erdtman, and C. A. Wachtmeister Chemistry of Lichens. XIII. Structure of Pannaric Acid. Acta Chem. Scand. 13, 1855 (1959). 

Elix, J. A. Annelated Furans. Vlll. A Synthesis of Pannaric Acid. Austral. J. Chem. 25, 1129 (1972). 

Fig. 4. Structural relationships and possible formation of the five types of condensation products of orsellinic acid (6) or its homologues taking place in lichens. (9a) = olivetoric acid, (9b) = dihydropicrolichenic acid, (10) = physodic acid, (11) = picrolichenic acid, (12) = pannaric acid, (13) = pyxiferin.

PD—, K—, C+ greenish Didymic acid, pannaric acid, porphyrilic acid, strepsilin... 

Pannaric acid 10-methylester 489 pale yellow crysta... 

Elix JA, Naidu R, Laundon JR (1992) A Synthesis of the Lichen Dibenzofuran Pannaric Acid 2-Methyl Ester and its Isomer 3-0-Methylpannaric Add. Aust J Chem 45 785... 

---