Caperatic 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...

Brandange S, Morch L, Vallen S (1975) The structure of caperatic acid. Acta Chem Scand B 29 889-890 Brasch J, Jacobsen P (1991) Flechten und ihre Allergene. AUergologie 14 99-103... 

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... 

A comparison of the mass spectral fragmentation patterns of the dimethyl ester of caperatic acid (41) and the corresponding di(trideutero-methyl) ester located the position of the ester function in this molecule and established the structure as methyl 3,4-dicarboxy-3-hydroxyoctadecanoate (41) (25). In a corroborative chemical degradation (41) was oxidized by treatment with sodium bismuthate, whereupon methyl 3-oxo-octadecano-ate (42), the decarboxylation product of the initially formed P-keto-carboxylic acid, was detected (25). 

A homologous aliphatic acid, methyl 3,4-dicarboxy-3-hydroxy-19-oxoeicosanoate (43), has been isolated from Usnea meridensis 210). The structure of this compound followed from the spectroscopic and chemical properties, by comparison with the properties of caperatic acid (41) and by sodium bismuthate oxidation to methyl 3,19-dioxoeicosanoate (44) 210). Caperatic acid (41) and methyl 3,4-dicarboxy-3-hydroxy-19-oxoeico-sanoate (43) have similar optical rotations but the absolute configuration of these acids remains to be determined. 

Brandange, S., L. Morch, and S. Valten The Structure of Caperatic Acid. Acta. Chem. Scand. 29B, 889 (1975). 

Rangiformic acid is the monomethylester of (12). Caperatic acid (13) is derived from rangiformic acid by hydroxylation. 

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

Deriv Dimethyl caperatate, needles (MeOH), mp 56.5-57.5 °C, from norcaperatic acid with... 

The higher fatty acids and their lactones occurring in lichens can be divided into three groups ) -lactone acid derivatives [nine members, e.g., protolichesterinic acid (1)] dibasic fatty acids [roccellic acid (2)] and tri-basic fatty acids [caperatic, nor- and rangiformic acids (3)]. In addition, two tetrahydroxy fatty acids, e.g., ventosic acid [CH3(CH2)8(CHOH)2-CH2— (CH0H)2(CH2)7C00H] have been reported (Solberg, 1957). All aliphatic lichen acids are optically active. 

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