Acarenoic acid

A Mixture of acaranoic and acarenoic acids short fan-shaped lamellae... 

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...

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... 

Acaranoic acid and acarenoic acid isolated from Acarospora chloro-phana have now been assigned the six-membered 8-lactone structures (71) and (73) respectively 182) rather than the previously accepted y-lactone structures (74) and (75). 

The negative Cotton effect exhibited by ( —)-acaranoic acid (71) fixed the chirality as shown in (72) and the absolute configuration as ( —)-2(5)-methyl-3 (i )-carboxypentadecyl-1 5(5)-olide. Catalytic hydrogenation of ( —)-acarenoic acid (73) produced ( —)-acaranoic acid (71) and hence established the configuration of the former compound as 3 (R). 

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). 

Structure of Acaranoic Acid and Acarenoic Acid. Phytochem. 19, 2713 (1980). 

Fig. 2. Probable biosynthesis of protolichesterinic acid (1), roccellic acid (2), rangiformic acid (3), and acarenoic acid (5). The labeling given for (1) is the one expected after administration of the likely precursor oxalacetate by analogy with the results reported for succinate.

Acarenoic and acaranoic acids, obtained from the lichen... 

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