Crepenynic

Crepenynic acid 18 2 (9c, 12a) Accounts for 60% of the fatty acids in seeds of Crepis foetida, a member of the compositae family... 

Another alteration of unsaturated fatty acids is the formation of acetylenic groups (-OC-). This apparently occurs by dehydrogenation of -CH=CH- Examples of naturally occurring acetylenes are crepenynic acid (p. 381), alloxanthin (p. 1240), and the following remarkable hydrocarbon from the common cornflower Centaurea cyanusm ... 

These are average values from recent years crops bContains 89.2% ricinoleic and 1.4% dihydroxystearic acids Contains 59.8% crepenynic acid "Contains 78.0% licanic acid and 4.0% hydroxy acids eHigh-erucic-acid variety Contains 71.3% vemolic acid 6Contains 78.5% vemolic acid and 5.8% hydroxy fatty acids. 

No real evidence exists concerning the in vino formation of the carbon-carbon triple bond but dehydrogenation via cis double bonds was favoured speculatively and appears probable on account of the similar incorporations observed for linoleate and crepenynate (5) - and the better incorporations of 14-c( r- than 14-rra is-dehydrocrepenynate (43) into several fungal metabolites (e.g. 35, 36, 40) . Biosynthetic experiments with leaf homogenates of Chrysanthemum f/oscii/osum indicate that the enzymes required for the desaturation of oleic acid are located within the chloroplasts whilst the final oxidation of the C13 triyne skipped-ene... 

Acetylenic Crepenynic acid 18 2AM2yne Crepis foetida Polymers -... 

Crepenynic Triple bond Crepis alpina 70 A. thaliana 25 15... 

Few recent studies have been made on alkyne biosynthesis. Crepenynic acid has been shown to be a precursor of C9 to C14 polyalkynes in fungal cultures, and was also demonstrated to be a precursor of falcarinol cf 4, falcarinone) in tissue cultures of Daucus car Ota (carrot). (14-Z)-14,15-didehydrocrepenynic acid (67, Figure 10) is predominately converted into 68 by fungi of Lepista spp whereas Caprinis spp yield 69. ... 

Crepenynic add see polyynes. p-Cresol mettiyl ether see ylang-ylang oil. Cribrochalnainiiie oxide A. 

Crepenynic acid (18 2 9cl2a) is of special interest because it is recognized as an important biosynthetic intermediate between the more conventional Cig fatty acids and a large number of polyacetylenes of varying chain length but most commonly C9, C13 or C17. This acid, first recognized in Crepis foetida seed oil (35-60%), occurs in other Crepis species, in Saus-surea candicans seed oil (—33%) and in seed oils of the Afzelia species where it is sometimes accompanied by a more unsaturated compound (dehydro-crepenynic acid). 

The most important monoacetylenic acids are tariric (18 1 6a) and crepenynic (18 2 9cl2a) though other examples have also been recognized. Tariric acid has long been known as a component of seed oils of the Picramnia species. Its isomer, stearolic acid, though easily made in the laboratory from oleic acid, occurs only rarely as a minor component in Santalaceae seed oils where more unsaturated mono- and poly-acetylenic compounds are also present (see below). Two rare acids related to stearolic acid are 17 1 (8 ) and 18 2 (9al7e). 

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