Lichen substances biosynthesis

Biosynthesis of lichen substances, products of a symbiotic association, K. Mosbach, Angew. Chem. Int. Ed. Engl., 1969, 8, 240. 

Mosbach, K. On the Biosynthesis of Lichen Substances 2. The Pulvinic Acid Derivative Vulpinic Acid. Biochem. Biophys. Res. Commun. 17, 363 (1964). 

Maass, W. S. G., and A. C. Neish Lichen Substances II. Biosynthesis of Calycin and Pulvinic Dilactone by the Lichen, Pseudocyphellaria crocata. Canad. J. Botany 45, 59 (1967). 

Lichen substances are organic compounds synthesized by lichens. They have long attracted the attention of organic chemists, and their chemistry, structure, properties, and distribution have been treated in detail recently in major works by Asahina and Shibata (1954) and Culberson (1969,1970). This field is also reviewed by Huneck (1968, 1971). Further details on the biosynthesis of lichen substances may be found in Chapter 16 by Mosbach. 

Fig. 12. Biosynthesis of aromatic lichen substances of the shikimate group from Q — C3 fragments. In compounds, whoseformation was demonstrated experimentally after administration of phenylalanine, the C-labeling obtained has been marked with an asterisk.

Besides the lichen substances discussed, a number of compounds have been isolated which simply represent general constituents of living cells, biosynthesis of which will not be taken up here. Sufficient to mention choline sulfate and ethanol sulfate esters, with which S-labeling studies have recently been carried out (Feige and Simonis, 1969). Finally, attention should be drawn to a report by Jackson and Keller (1970) on the formation of an unusual ferric oxide mineral through the action by a tropical lichen on basalt as an example of indirect biosynthesis. 

Fox, C. H., and Mosbach, K. (1967). On the biosynthesis of lichen substances. Part 3. Lichen acids as products of a symbiosis. Acta Chem. Scand. 21, 2327. 

Yamazaki, M., and Shibata, S. (1966). Biosynthesis of lichen substances. II. Participation of Cj-unit to the formation of -orcinol type lichen depside. Chem. Pharm. Bull. 14,96. 

Chapter 16. Biosynthesis of Lichen Substances Klaus Mosbach... 

Lichen chemistry continues to be a flourishing branch of natural product chemistry. Since the last major review by Elix et al. in volume 35 of this series 274) many new and interesting lichen substances have been isolated and synthesized. This suggests that an update is desirable. As in the previous articles new methods for structure elucidation and synthesis, biosynthesis, chemotaxonomy and biological activities of lichen substances will be discussed. Some other relatively recent treatments of the subject need to be mentioned A short chapter by... 

Only a few papers concerning the biosynthesis of lichen substances have been published between 1984 and 1998. Biogenesis of the diphenyl derivative contortin (see Scheme 183) very likely proceeds by phenolic coupling of two molecules of C-methylphloracetophenone methyla-... 

Usnic Acid. 2I6 Diacetyl 7t9-dihydraxy 8i9b-di-methyl-It3(2H,9bH)-dibenzofurandione usninic acid usnein Usniacin. C H,407 mol wt 344.31. C 62.79%. H 4.68%, O 32.53%. Antibacterial substance found in lichens. Isolation from varieties of Usnea barbota (L.) Wigg., Usneaceae Rochleder, Heidi> Ann. 48, If (1843) Widman Ann. 310, 230 (1900) 324, 139 (1902). Isoin from Ramalina reticulata Marshak, Public Health Reports 62, 3 (1947) Stark et of., J. Am. Chem. Soc. 72, 1819 (1950). Occurs in nature in both the d- and /-forms as well as a racemic mixture. Structure Curd, Robertson, J. Chem. Soc. 1937, 894 Schopf, Ross, Ann. 546, (1941) Barton, Brunn, /. Chem. Soc. 1953, 603. Resolution of ( )-usnic acid Dean et ai, ibid. 1250. Synthesis Barton et a/., ibid. 1956, 530. Biosynthesis in vitro Penttila, FaJes, Chem. Commun 1966, 656. Abs config of (+)-fomv S. Huneck et aL, Tetrahedron Letters 22, 351 (1981). 

Biosynthesis The aromatic hydroxycarboxylic acid is first formed from polyacetates and then esterified enzymatically. Besides in lichens, D. also occur in tanning substances, e.g., in coffee or savory a well-known representative is digallic acid (see tannins). Lit. Culberson Karrer, No. 1023-1053 Zechmeister 41, 1-46 45, 103-234. 

---