3534
E. Kiljunen, L. T. Kanerva / Tetrahedron: Asymmetry 10 (1999) 3529–3535
4.2. Enantioselective oxidation of glycidol
A freshly distilled glycidol (56 µl, 0.85 mmol) was added into a 4 ml vial containing hexane (450
µl), ethyl acetate (450 µl) and a citrate buffer (100 mM; pH 4.0–7.0; 200 µl). The mixture was stirred
for 10 min followed by the addition of CPO (0.65 mg). The stirring was continued for an hour at room
temperature (25°C) or at 5°C. The reaction was initiated by adding tert-butyl hydroperoxide (1.0 mmol in
seven portions within 24 hours). The progress of the reaction against decane as an internal standard and
the enantiomeric excess values for the prevailing alcohol enantiomer were determined by taking samples
from the reaction mixture and analysing them by the chiral GLC method. The absolute configuration
of the less reactive (R)-glycidol was determined by using commercial enantiomers as reference for gas
chromatograms. The presence of the aldehyde in the reaction mixture was confirmed using spectroscopic
13
methods directly on the sample and substracting the glycidol from the spectra. C NMR: 171.04 (C-1);
1
4
3.72 (C-2) and 50.58 (C-3). H NMR: 2.97–2.98 and 3.02–3.05 (m, 2H, 3-H); 3.26–3.30 (m, 1H, 2-H)
and 8.89 and 8.87 (d, 1H, J=6.4 Hz, 1-H).
13
These data can be compared to the spectroscopic data for glycidol. C NMR: 44.23 (C-1); 61.91 (C-2)
1
and 52.23 (C-3). H NMR: 2.73–2.93 (m, 2H, 3-H); 3.07–3.13 (m, 1H, 2-H); 3.51–3.56 and 3.83–3.88
(m, 2H, 1-H) and 4.93 (m, 1H, OH).
4.3. Enantioselective oxidation of cis-2,3-epoxyhexanol
cis-2,3-Epoxyhexanol (50 µl, 0.43 mmol) was added into a 4 ml vial containing hexane (1.8 ml) and
a citrate buffer (100 mM; pH 5.0–6.5; 200 µl). The mixture was stirred for 10 min followed by the
addition of CPO (0.65 mg). The stirring was continued for an hour at 5°C. The reaction was initiated
by adding tert-butyl hydroperoxide (0.58 mmol in 4 portions within 10 hours). The progress of the
reaction and enantiomeric excess values were determined as decribed above. The absolute configuration
8
of less reactive starting material and the produced aldehyde were assigned in the previous work. The
spectroscopic data below were previously determined for the separated resolution products.
1
3
(
2S,3R)-Epoxyhexanol: C NMR: 60.85 (C-1); 57.08 (C-2); 56.79 (C-3); 29.86 (C-4); 19.86 (C-5)
1
and 13.82 (C-6). H NMR: 0.95 (t, 3H, 6-H); 1.5–1.6 (m, 4H, 5-H and 4-H); 2.3 (br., 1H, OH).
13
(
2S,3S)-Epoxyhexanal: C NMR: 199.18 (C-1); 57.82 (C-2); 56.00 (C-3); 30.02 (C-4); 26.34 (C-5)
1
and 13.66 (C-6). H NMR: 0.95 (t, 3H, 6-H); 1.45–1.75 (m, 4H, 4-H and 5-H); 3.25 (m, 1H, 3-H); 3.31
m, 1H, 2-H); 9.44 and 9.33 (d, 1H, J=5.2 Hz, 1-H).
(
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