ASYMMETRIC SYNTHESIS OF 2-HYDROXY FATTY ACIDS
211
tion by Immobilized Bakers’ Yeast in Hexane, J. Org. Chem.
53:2589–2593 (1988).
6. Wong, C.-H., and J.R. Matos, Enantioselective Oxidation of 1,2-
2-oxazolidinone as a chiral auxiliary to give 5f–5i in high
yields (Scheme 1). As shown in Table 2 (Entries 6–9), their
ee of 4f–4i are 98% with no observable double-bond isomer-
ization for all cases.
Diols to -α-Hydroxy Acids Using Coimmobilized Alcohol and
L
Aldehyde Dehydrogenases as Catalysts, Ibid. 50:1992–1994
(1985).
The position of the hydroxy group in the products was con-
firmed by 13C NMR and mass spectra. The chemical shifts of
the C-2 (70.5 or 70.4 ppm) in the methyl esters of 2-hydroxy
fatty acids 4a–4i are consistent with the values in the litera-
ture (15). Further confirmation was obtained by silylating the
methyl esters of 2-hydroxy fatty acids 4a–4i with a silylating
reagent (Supelco Sylon BTZ mixture) followed by GC–MS
analyses. The EI mass spectra of the silylated products obey
a fragmentation pattern of 2-hydroxy fatty acids in the litera-
ture (16). The typical peaks for silylated 2-hydroxy fatty acids
by loss of CH3 (m/z = 369 for 4a–4h, m/z = 367 for 4i) and
loss of COOCH3 (m/z = 325 for 4a–4h, m/z = 323 for 4i) were
obtained in the EI mass spectra.
7. Adam, W., W. Boland, J. Hartmann-Schreier, H.-U. Humpf, M.
Lazarus, A. Saffert, C.R. Saha-Moller, and P. Schreier, α-Hy-
droxylation of Carboxylic Acids with Molecular Oxygen Cat-
alyzed by the α-Oxidase of Peas (Pisum sativum): A Novel Bio-
catalytic Synthesis of Enantiomerically Pure (R)-2-Hydroxy
Acids, J. Am. Chem. Soc. 120:11044–11048 (1998).
8. Adam, W., W. Lazarus, A. Saffert, C.R. Saha-Moller, and P.
Schreier, Enantioselective α-Hydroxylation of Carboxylic Acids
with Molecular Oxygen Catalyzed by the α-Oxidation Enzyme
System of Young Pea Leaves (Pisum sativum): A Substrate Se-
lectivity Study, Tetrahedron: Asymmetry 7:2287–2292 (1996).
9. Corey, E.J., J.O. Link, and Y. Shao, Two Effective Procedures
for the Synthesis of Trichloromethyl Ketones, Useful Precursors
of Chiral α-Amino and α-Hydroxy Acids, Tetrahedron Lett. 33:
3435–3438 (1992).
10. Gamboni, R., P. Mohr, N. Waespe-Sarcevic, and C. Tamm,
Asymmetric Synthesis of α-Hydroxy-Ester via Ester Enolates,
Ibid. 26:203–206 (1985).
11. Davis, F., and L.C. Vishwakaram, Asymmetric Synthesis of α-
Hydroxy Carboxylic Acids: Direct Oxidation of Chiral Amide
Enolates Using 2-Sulfonyloxaziridines, Ibid. 26:3539–3542
(1985).
This research provides a convenient route to enantiomeri-
cally pure 2-hydroxy fatty acid methyl esters and could be
similarly applied to prepare other functionalized fatty acid es-
ters such as 2-amino fatty acid esters and 2-halo fatty acid es-
ters.
12. Evans, D.A., M.M. Morrissey, and R.L. Dorow, Asymmetric
Oxygenation of Chiral Imide Enolates. A General Approach to
the Synthesis of Enantiomerically Pure α-Hydroxy Carboxylic
Acid Synthons, J. Am. Chem. Soc. 107:4346–4348 (1985).
13. Davis, F.A., S. Chattopadhyay, J.C. Towson, S. Lal, and T.
Reddy, Chemistry of Oxaziridines. 9. Synthesis of 2-Sulfonyl-
and 2-Sulfamyloxaziridines Using Potassium Peroxymonosul-
fate (Oxone), J. Org. Chem. 53:2087–2089 (1988).
14. El-Shearkaway, S.H., W. Yang, L. Dostal, and J.P.N. Rosazza,
Microbial Oxidation of Oleic Acid, Appl. Environ. Microbiol.
58:2116–2122 (1992).
15. Tulloch, A.P., Carbon-13 NMR Spectra of All the Isomeric
Methyl Hydroxy- and Acetoxyoctadecanoates, Org. Magn.
Reson. 11:109–115 (1978).
ACKNOWLEDGMENTS
We thank Dr. Gerhard Knothe for sincere comments and Dr. David
Weisleder for the nuclear magnetic resonance spectra.
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[Received May 8, 2000; accepted October 10, 2000]
JAOCS, Vol. 78, no. 2 (2001)