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Cuperus, F.P. and J.T.P. Derksen. 1996. High Value-Added Applications from Vernolic Acid. p. 354-356. In: J. Janick (ed.), Progress in new crops. ASHS Press, Alexandria, VA.

High Value-Added Applications from Vernolic Acid*

F. Petrus Cuperus and Johannes T.P. Derksen

  1. METHODOLOGY
  2. RESULTS
    1. Bombykol
    2. Traumatic Acid
  3. CONCLUSIONS
  4. REFERENCES
  5. Fig. 1
  6. Fig. 2
In 1994 the total world production of vegetable oils amounted to approximately 68 million tonnes, of which 80% originated from five crops: soybean, oil palm, rapeseed, sunflower, and coconut. Although the exact composition of the oil from these crops can vary, the number of different fatty acid species available from these crops is rather limited. For food uses this is not a major problem, however, for non-food applications the limited range of oil and fat feed-stocks available for the production of fatty acids and derivatives can present a severe constraint. Therefore there is an increasing industrial interest in the development of new crops, which are optimized for specific applications. The new crops of interest include those that contain a higher percentage of a desirable fatty acid or a lower percentage of undesirable fatty acids and those that contain unique fatty acids. Such unusual fatty acids could on the one hand replace raw materials from petrochemical origins with renewable resources, and on the other hand expand the existing range of raw materials available and potentially lead to novel end products. Moreover, consumer products made from renewable resources may also carry an appealling environment-friendly or "green" label.

Currently, many oils are converted through more or less extensive oleochemical processing to value-added products, such as lubricants, polymer additives or surfactants. In most cases these products are based on fatty acids, their methyl esters or fatty alcohols as intermediates, because the reactive headgroup of these compounds is a ready candidate for chemical derivatization.

The limited availability of fatty acids that are functionalized (e.g., oxygenated) in the fatty acyl chain is especially noteworthy in this respect. In fact, the to date only commercially available, naturally occurring functionalized fatty acid is ricinoleic acid, which is recovered from castor bean oil. However, because of the chemical versatility of such functionalized fatty acids, researchers around the world are studying new oilseed species that may add to the oleochemists' palette of raw materials. In particular, oilseed crops that can supply new, hydroxylated (Lesquerella spp., Dimorphotheca spp.) or epoxidated fatty acids (Vernonia spp, Euphorbia lagascae) are of interest. However, the transformation of a new oilseed crop from an experimental plant species to an industrial commodity would be greatly facilitated if during the introductory phase a commercially viable specialty or niche application could be found in which agronomical (e.g., yield, harvesting techniques) and economic issues (e.g., available volume, raw materials costs) are less paramount than in bulk applications.

Therefore, as part of the mission of the Agrotechnological Research Institute (ATO-DLO) in The Netherlands to increase the added value of agricultural products in the post-harvest phase, preferably in close cooperations with industries that are knowledgeable in the field of specific applications, industrial scale processing and marketing, we have started to explore the oleochemistry and potential use of two unusual, functionalized fatty acids, i.e. vernolic and dimorphecolic acid, in a variety of high value products. In this paper attention will be focussed mainly on vernolic acid (12,13-epoxy, 9c-octadecenoic acid), which contains an epoxy group in combination with a cis double bond and which makes this fatty acid an interesting building block for specialty products.

METHODOLOGY

Starting from locally grown Euphorbia lagascae seeds, oil was recovered by cold pressing with a Komet single screw oil expeller, yielding a 94% recovery of good quality oil, as described before (Derksen et al. 1993). From this oil vernolic acid by enzymatic hydrolysis of the oil, using Candida rugosa lipase, followed by purification of the resulting vernolic acid by wiped-film vacuum distillation of the oily phase. The purity of vernolic acid recovered was approximately 95%.

The resulting vernolic acid was subsequently used to explore several synthesis routes on a lab scale towards new fine chemical products. High value substances synthesized include bombykol, bombykal, traumatinic acid, and lactones. Synthesis routes employed are indicated in the results section.

RESULTS

Vernolic acid is a natural epoxy fatty acid that is present in new oil seed crops like Euphorbia lagascae and Vernonia spp. Their seed oils consist over 60% vernolic acid allowing a relatively easy recovery of this versatile starting material for the synthesis of a wide range of (fine) chemicals. We have explored several synthesis routes for the production of selected specialty chemicals in which the vernolic acid epoxy group serves as a key functionality. A few examples are described below.

Bombykol

Bombykol, 10(E),12(Z)-hexadienol, has been identified as a sex pheromone of the silkworm Bombyx mori and can be used in pest control. It has been synthesized on a gram scale according to the route indicated in Fig. 1. Starting from vernolic acid (1), first the epoxy group was ring-opened, resulting in a diol product (2). This diol could be selectively cleaved to the aldehyde (3) without affecting the carbon-carbon double bond and leaving hexenal (4) as a side-product, that in itself may find useful applications in the flavor industry. Protecting the carboxylic acid group and isomerization of the double bond yielded a reactive intermediary product [12-oxo-10(E)-dodecenoic acid (5)] which contained a carboxylic ester and also an aldehyde functionality in conjugation with the carbon-carbon double bond. Subsequent Wittig olefination of (5) leads to the 10(E), 12(Z)-product (6), which is selectively reduced to bombykol (7).

Traumatic Acid

Traumatic acid, (2(E)-dodecenoic acid, is active as wound hormone of plants and can be used as an intermediate in prostaglandine synthesis. The first part of the synthesis (Fig. 2) is identical to the synthesis of bombykol. Mild oxidation of the reactive aldehyde 12-oxo-10(E)-dodecenoic acid (5) leads to the formation of a carboxylic acid functionality while leaving the carbon-carbon double bond unaffected [product (8)]. Cleavage of the ester part of (8) yields traumatic acid (9) a base for certain pharmaceuticals.

CONCLUSIONS

The synthesis described above, using functionalized fatty acids as a renewable starting material, provide good alternatives for existing syntheses (Dasardhi et al. 1991) and can reduce the amount of hazardous chemicals required. On-going research will extend the range of products derived from vernolic acid far beyond the products mentioned here, leading already in the near future, to an increased interest in natural starting materials in general and specifically in unusual fatty acids for the chemical syntheses of, particularly, fine chemicals.

The successful introduction of a new agricultural raw material must start with the identification of initial "niche" markets of high added-value products. When a raw material-product combination is established, further development of the source material and processing technology is warranted for further market expansion, including towards large volume-low added-value markets. Ideally, this will then result in a firm foothold for the new crop in question.

REFERENCES

*The authors wish to thank Drs. G. Kramer, R. Stienstra, and A. Mekkering for their contribution to this study.
Fig. 1. Synthesis route from vernolic acid to bombykol.
Fig. 2. Synthesis of traumatic acid from the vernolic acid-derived intermediate 12-oxo-10-E-dodecenoic acid.
Last update August 21, 1997 aw