Lichesterinic acid

A further family of aromatic compounds produced by lichens is derived from shikimic add via phenylalanine and is exemplified by vulpinic acid (7.55), which was isolated from Letharia vulpina. Vulpinic acid has been synthesized by the lead tetra-acetate oxidation of polyporic acid. Lichens also produce some alkylated citric acid derivatives such as lichesterinic acid (7.56) and some sterols. 

Protolichesterinic acid MuroUc acid Lichesterinic acid Neuropogonic acid... 

Fig. 14. A Mixture of acaranoic acid and acarenoic acid, GE. Bar 100 jim. B Caperatic acid, GE. Bar 100 im. C Caperatic acid, GE. Bar lOjim. D Lichesterinic acid, GE. Bar lOjim...

Deriv Methyl lichesterinate, mp 53-54 °C, [a]J, - 28.1, from lichesterinic acid with CHjNj StL Cetraria ericetorum Opiz MC Fig. 14D... 

The fatty acids of lichens show some resemblance to those in non-lichen-forming fungi, but none are identical. Aliphatic acids, much rarer in lichens than in other plant groups, appear to be formed in a very different manner through the tricarboxylic acid cycle. Known higher aliphatic acids and related substances are acaranoic acid, acarenoic acid, (+)-aspicilin, (—)-caperatic acid, (—)-lichesterinic acid, linoleic acid, (—)-nephromopsinic acid, (+)-nephrosteranic acid, (+)-nephrosterinic... 

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). 

The stereochemistry of these acids has been elucidated in part by past workers. The absolute configuration of some of these lactones has been determined from ORD and CD data. Compound (16), for example, has a negative Cotton-effect at 260 nm. Protolichesterinic acid with an UV maximum at 217 nm (log, e = 5.5) can be isomerized easily to lichesterinic acid by heating with acetic anhydride. 

The antibiotic effects are based on lichen substances of which the most effective are usnic acid, the lichesterinic acid group, as well as orcinol-type depsides and depsidones. 

The situation in vivo usually presents new problems and difficulties questions of resorption, toxicity, effect of serum albumin, allergic reactions and so on. The fate of the lichesterinic acid group was disturbed in vitro when serum albumin was present. Tests with mice gave no positive result (Vartia and Tervilla, 1952). 

Caperatic acid Rangiformic acid Protolichesterinic acid Oihydroprotolichesterinic acid Lichesterinic acid Oihydrolichesterinic acid Lichesterylic acid... 

Lichesterylic acid and methyl protolichesterinate have been found in Cetraria islandica (555) the latter ester was prepared from the potassium salt of protolichesterinic acid and methyl iodide 413). Allo-protolichesterinic acid adds diazomethane to form isomeric pyrazoline methylesters, the stereochemistry of which was established by their respective CD spectra. Hydrogenation of allo-protolichesterinic acid with Pd-C in acetic acid produces a mixture of (-)-dihydro-allo-protolichesterinic acid (33), (-)-nephromopsinic acid (34) and (-)-lichesterinic acid (35) (see Scheme 34). 

The cytotoxicity of diploicin (77) was evaluated by Millot and coworkers in 2009 against B16 (murine melanoma) and HaCaT (human keratinocyte) cell lines [100]. Pannarin (66), a secondary metabolite from lichen Diploicia canescens, was tested by two different research groups for its inhibitory potential against DU-145 prostate carcinoma [100] and M14 (human melanoma) cell lines with positive results [96]. Recently, the cytotoxicity of proto-lichesterinic acid (8) against HeLa cell lines has been evaluated by Brisdelli and coworkers. Its activity is based on its abdity to induce cell death through activation of caspases-3, -8, and -9 [101]. 

Leurocristine, K15 Leurosidine, K15 Levopimaric acid, T32 Liatrin A, T29 Lichesterinic acid, A12 ... 

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