Roccellic acid

The rearrangement of a trichloropyrrolidin-2-one, prepared by the CuCl-TMEDA-catalysed atom transfer radical cyclization of A-alkyl-AM3-chloroprop-2-enyl)-2,2-dichloromyristamide, with m-propyl amine or CfbONa-CHsOH, is the key step in a route to chaetomellic anhydride C and ( yerythro -roccellic acid.169... 

These lichens contain a number of peculiar acids (lecanoric acid erythric acid, roccellic acid, c.), which are split up by alkalies, the final products being orcin, CeH3CH3(OH)2, and erythrite, C4H10O,. 

Lecanora rupicola Atranorin Chloroatranorin Roccellic acid Sordidone Thiophanic acid Eugenitin Eugenitol Roccellic acid Sordidone Fox and Huneck (1969)... 

Deriv Dimethyl roccellate, mp 28.5-30.5 °C, from roccellic acid with ethereal CHjNj [aJo + 14.5 (CHCI3)... 

Foo LY, Gwyn SA (1978) The identification of norlobariol, a new lichen constituent from Xanthoparmelia scabrosa (Tayl.) Hale. Experientia 34 970-971 Fox CH, Huneck S (1969) The formation of roccellic acid, eugenitol, eugenitin, and rupicolon by the mycobiont Lecanora rupicola. Phytochemistry 8 1301-1304... 

Garcia F, Espinoza CA, Coltantes SGG, Rios VV, Quilhot PW (1982) Lichen substances and the plant growth. III. The effects of roccellic acid on the growth of germlings of Ulva lactuca L. J Hattori Bot Lab 53 443-447... 

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 dibasic fatty acid (+)-roccellic acid is ( -)-2S-nlethyl-3R-dodecyl-succinic acid (11) and can be synthesized as a racemate through anodic coupling of lauric acid with erythro-3,4-dimethoxycarbonylpentanoic acid. 

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. 

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.

Scheme 25. Isomerization of roccellic acid, reduction of dimethyl roccellate and oxidation...

Keto acids (5-keto-15 0,5-keto-16 0,5-keto-18 0,5-keto-21 0,5-keto-23 0) have been isolated from Cetraria delisei and C. islandica (659, 658). Fatty acids from Xanthoriaparietina collected at different elevations (400, 800 and 1300 m a.s.) have been analyzed (576). The main fatty acid at the lowest elevation was 18 2, while 14 0 was the major component at the other two elevations. The isomerization of roccellic acid to threo-roccellic acid (see Scheme 25) has been studied 407). Reduction of dimethyl roccellate with LiAlH4 gave the corresponding diol which yielded two isomeric y-lactones with Jones reagent (see Scheme 25). 

Structure 17 with unknown stereochemistry has been proposed (502) for angardianic acid from Leproloma angardianum. If its biosynthesis is similar to that of roccellic acid angardianic acid should have stereo-structure 17a. 

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