Furanoid fatty acid

Natural products find a place not as such but at points where, once again, their chemistry illustrates the behavior of their furan nuclei. There are now so many naturally occurring furans (the sea adds its quota to the land plant count every week) that even to make a list, as in the previous review, was too big a task and would have taken too much room happily, reference to almost any issue of Phytochemistry will immediately supply examples and there are already some good lists available elsewhere (eremophilane2 and farnesane23 furans, butenolides,3 furanoid fatty acids,4 marine products5). 

Epoxides (oxirans) and 1,2-diols can also be looked upon as disguised ketones capable of being unmasked by acids. Since its development by Spencer et al49 the idea has been utilized by several other groups who used protic acids in work aimed at syntheses of methyl lambertianate,50 a rare furanoid fatty acid from an Exocarpus species,51 and a terpenoid furan,... 

Methyl-2,4-nonanedione Soy beans Tea Butter Furanoid fatty acids [80]... 

Each new discovery of unusual fatty acids in marine organisms leads to concerns that eventually dissipate. An example is the furanoid fatty acids that were once well documented as common in most oils (26). More recent papers and books on omega-3 fatty acids simply ignore the subject. 

The odorants of green tea, powder and brew, are detailed in Table 6.54. 3-Methyl-2,4-nonanedione (no. 3) is of special interest among the odorants showing high OAV. It smells green and strawy and was detected at first in soybean oil showing a light-induced off-flavour (Table 6.55). Precursors of no. 3 are furanoid fatty acids [23, 107[. 

Guth, H., Grosch, W. (1993) Furanoid fatty acids as precursors of a key aroma compound of green tea. In Schreier, P., Winterhalter, P. (eds.) Progress in Flavour Precursor Studies. Allured Publishing, Carol Stream, pp. 401-407... 

CMPF in humans remain unknown (Gil). Furan fatty acids have yet to be found in human lipids. However, urofuranic acids are present in the urine of babies and adults who have not consumed fish products for months (S3). Consequently, ingestion of fish does not appear to be the source of these furanoid fatty acids. Although the metabolic role of these compounds remains to be elucidated, substituted furan substances may be involved in the metabolism of uronic acid and carbohydrates (M40). 

Reaction with a, (-unsaturated ketone. Attempted Baeyer-Villiger reaction of 1, readily available from methyl ricinoleate, with tn-chloroperbenzoic acid under usual conditions unexpectedly leads to the known furanoid fatty acid (3), although in only 25% yield. When the epoxidation is conducted under milder conditions, the expected epoxide (2) is obtained readily. When this epoxide is refluxed in chloroform containing trace amounts of hydrogen chloride, 3 is obtained in 80% yield. This reaction may be relevant to biosynthesis of natural furanoid fatty acids such as 3. ... 

F-acids (furan fatty acids, furanoid fatty acids). The F-a., first isolated in 1966 from Exocarpus seed oil and then in 1974 from fish oils, are multiply substituted furan derivatives of fatty acids. 

Glass, R.L., Krick, T.P., Sand, D.M., Rahn, C.H., and Schlenk, H. (1975) Furanoid Fatty Acids from Fish Lipids, Lipids 10, 695-702. 

Hasma, H., and Subramaniam, A. (1978) The Occurrence of a Furanoid Fatty Acids in Hevea brasiliensis Latex, Lipids 13, 905-907. 

Bach and Krueger used a Negishi coupling to synthesize a derivative of the naturally occurring furanoid fatty acid Treatment of 3-... 

Lie Ken lie, M.S.F., and M.S.K. Syed-Rabmatullah, Chemical and Enzymatic Preparation of Acylglycerols Containing Cjg Furanoid Fatty Acids, Lipids 30 79-84 (1995). 

Marson, C.M., and S. Harper, Total Synthesis of the Naturally Occurring Furanoid Fatty Acid, F5, Tetrahedron Lett. 39 333-334 (1998). 

Furanoid fatty acids (FuFAs) have a furanoid ring in their principal chain. One example of a furanoid fatty acid has the formula, C22H38O3, and has the systematic name of 3,4-dimethyl-5-pentyl-2-fur-anundecanoic acid (Figure 15). 

Figure 11.7. Proposed mechanism for the formation of 3-methylnonane-2,4-dione by photosensitized oxidation of furanoid fatty acids. From Grosch et al (1992).

Recent studies of photooxidized butter and butter oil identified by aroma extract dilution analysis, 3-methylnonane-2,4-dione, a potent volatile compound derived from furanoid fatty acids (see Section C.4) (Figure 11.7). Six different furanoid fatty acids were established as dione precursors, and were found in various samples of butter made from either sweet cream (116 76 mg/ kg), or from sour cream (153-173 mg/kg), or from butter oil (395 mg/kg). Similar precursors of the dione were identified in stored boiled beef and vegetable oils. This flavor defect arising by photooxidation of butter or butter oil is apparently different from the light-activated flavor in milk,that involves the interaction of sulfur-containing proteins and riboflavin. However, more sensory comparisons are needed to distinguish between these two flavor defects due to light oxidation. 

Among less volatile breakdown products, furan fatty acids were reported when air was bubbled through CLA dissolved in a mixture of methanol and water at 50°C. (20). Furanoid fatty acids might also arise in preparation of fatty acid methyl esters (FAME) for GC. To our knowledge, furan fatty acids have not been reported as an oxidative breakdown product in dry oil preparations of CLA. 

Furanoid fatty acids are present in some seed oils, but more interestingly perhaps they are found in the reproductive tissues of fish. The chromatographic analysis of these compounds has been reviewed by Lie Ken Jie [547]. It is apparent that the methyl ester derivatives can readily be subjected to GC analysis, and retention data have been published for a number of synthetic [4,548,549] and naturally occurring compounds [300,301,335,790,825],... 

Epoxyl groups are cleaved directly with periodic acid in halogenated solvents [100] or in diethyl ether [530], and the position of the ring is established by GC analysis of the products. Furanoid fatty acids, separated on TLC plates, can be detected by spraying with a 2 % solution of tetracyanoethylene in acetone, which reacts to give blue spots on a yellow background [300]. 

Methyl esters of furanoid fatty acids give good El mass spectra with characteristic ions being produced by fragmentations alpha to the furan ring [790]. 

Guth, H. Grosch, W. Detection of furanoid fatty acids in soya-bean oil—Cause for the hght-induced off-flavor. Fat Sci. Technol. 1991, 93, 249-255. 

Methyl-2,4-nonanedione Soybeans, green tea Furanoid fatty acids 39... 

Groweiss, A. and Kashman, Y. (1978a) A new furanoid fatty acid from the soft corals Sarcophyton aucum and S. gemmatum. Experientia, 34, 299. 

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