A. Halldorsson et al. / Tetrahedron Letters 42 (2001) 7675–7677
7677
its ethyl ester into the end positions by a 1,3-regioselec-
tive lipase. This approach has various drawbacks
related to the three equivalents of pure highly valuable
EPA or DHA required as well as a waste excess of the
MCFA or its ester. Besides that, rather complicated
mixtures were obtained requiring tedious separation
and purification procedures. Shimada and co-workers17
have managed to simplify that. Finally, Yamane and
co-workers18 have reported on a modification of their
approach based on a highly 1,3-regioselective lipase
catalyzed ethanolysis of the homogeneous EPA and
DHA triacylglycerol intermediates and a subsequent
lipase promoted esterification of the resulting 2-
monoacylglycerols with a different lipase. Currently, we
are highly successfully working on improving the yields
of the 1,3-regioselective enzymatic reaction to make the
reported approach even more feasible and efficient for
the synthesis of the structured triacylglycerols
described.
3. Haraldsson, G. G.; Halldorsson, A.; Kula˚s, E. J. Am. Oil
Chem. Soc. 2000, 77, 1139–1145.
4. Christensen, M. S.; Ho¨y, C.-E.; Becker, C. C.; Redgrave,
T. G. Am. J. Clin. Nutr. 1995, 61, 56–61.
5. Nettleton, J. A. Omega-3 Fatty Acids and Health; Chapman
and Hall: New York, 1995.
6. Haumann, B. F. INFORM 1997, 8, 428–447.
7. Haraldsson, G. G. In Enzymes in Lipid Modification;
Bornscheuer, U. T., Ed. Enrichment of lipids with EPA and
DHA by lipase; Wiley-VCH: Weinheim, 2000; pp. 170–189.
8. Yamane, T. In Enzymes in Lipid Modification; Bornscheuer,
U. T., Ed. Lipase-catalyzed synthesis of structured tri-
acylglycerols containing polyunsaturated fatty acids: mon-
itoring the reaction and increasing the yield; Wiley-VCH:
Weinheim, 2000; pp. 148–169.
8
8
9. Haraldsson, G. G.; Gudmundsson, B. O.; Almarsson, O.
Tetrahedron 1995, 51, 941–952.
10. Bloomer, S.; Adlercreutz, P.; Mattiasson, B. Biocatalysis
1991, 5, 145–162.
11. Haraldsson, G. G. In The Chemistry of the Functional
Groups, Supplement B2: The Chemistry of Acid Derivatives;
Patai, S., Ed. The application of lipases in organic synthesis;
John Wiley and Sons: Chichester, 1992; Vol. 2, pp.
1395–1473.
Acknowledgements
12. Berger, M.; Laumen, K.; Schneider, M. P. J. Am. Oil Chem.
Soc. 1992, 69, 955–960.
13. Waldinger, C.; Schneider, M. J. Am. Oil Chem. Soc. 1996,
73, 1513–1519.
14. Rosu, R.; Yasui, M.; Iwasaki, Y.; Yamane, T. J. Am. Oil
Chem. Soc. 1999, 76, 839–843.
15. Irimescu, R.; Yasui, M.; Iwasaki, Y.; Shimidzu, N.;
Yamane, T. J. Am. Oil Chem. Soc. 2000, 77, 501–506.
16. Irimescu, R.; Hata, K.; Iwasaki, Y.; Yamane, T. J. Am. Oil
Chem. Soc. 2001, 78, 65–70.
The University of Iceland Research Fund is acknowl-
edged for financial support, Novo Nordisk in Denmark
for providing the lipase free of charge, Dr. Sigridur
Jonsdottir at the Science Institute for running the
NMR analysis and Norsk Hydro in Porsgrunn, Nor-
way, for providing virtually pure EPA and DHA.
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