acid epoxidizes ‘itself’ in an uncatalyzed Prileshajev epoxidation (hence ‘chemo-
enzymatic’). In the cases we examined the reaction is definitely intermolecular;
however, for certain C¼C-bond positions an intramolecular reaction is likely
(compare Corey et al., 1979).
Terminal as well as internal unsaturated fatty acids were epoxidized with good
yields (see Table 1) and excellent selectivity (98 %). Neither the position and
configuration of the C¼C bond influence the results, nor is the secondary hydroxyl
group in ricinoleic acid involved. In the case of linoleic acid it is possible to obtain
selectively the diepoxide or the isomeric mono-epoxides by simply changing the
C¼C/H 2 O 2 ratio.
In addition to our own results, the method has been applied successfully by Fryk-
mann and Isbell (1997) for the epoxidation of meadowfoam fatty acids.
The heterogeneous biocatalyst can be recovered by a simple filtration after the
reaction, and surprisingly, it can be reused for multiple runs with little loss of ac-
tivity. Using only 200 mg of NovozymÒ435 (enzyme immobilized on carrier), we
were able to produce about 40 g of 9,10-epoxystearic acid, which is equal to a turn-
over of about 200 000 mol product per mol catalyst. Based on this observation, the
construction of a fixed-bed reactor for continuous operation is now in progress.
120 7 Lipase-Catalyzed Peroxy Fatty Acid Generation and Lipid Oxidation
Table 1.Chemo-enzymatic ‘self’-epoxidation of unsaturated fatty acids by NovozymÒ435/H 2 O 2.
No. Substrate Product Yield (GC)
(mol%)
1–1 9-decenoic acid 9,10-epoxy decanoic acid 72
1–2 10-undecenoic acid 10,11-epoxy undecanoic acid 77
1–3 13-tetradecenoic acid 13,14-epoxy tetradecanoic acid 78
1–4 oleic acid cis-9,10-epoxy stearic acid 72/88^1
1–5 elaidic acid trans-9,10-epoxy stearic acid 82
1–6 petroselinic acid 6,7-epoxy stearic acid 77
1–7 linoleic acid 9,10–12,13-diepoxy stearic acid 83
1–8 linoleic acid 9,10-epoxy octadec-12-enoic acid
12,13- epoxy octadec-9-enoic acid
9121–9 ricinoleic acid 9,10-epoxy-12-hydroxy stearic acid 95
(^1) Preparative scale; isolated yield.
(^2) Excess linoleic acid.
C¼C/H 2 O 2 (60 %)¼1 : 1.5; 0.05 mol C¼C/g enzyme.
16 h at room temperature (72 h at 40 8 C for terminal C¼C) in toluene.