STEREOCHEMICAL ANALYSIS OF SULFOXIDES OBTAINED BY DIVERTED DESATURATION

被引:84
作者
BUIST, PH
MARECAK, DM
机构
[1] Department of Chemistry, Carleton University, Ottawa, Ontario
关键词
D O I
10.1021/ja00039a018
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
We have shown that the DELTA-9-desaturase of Saccharomyces cerevisiae can behave as a regio- and enantioselective oxygenating agent. The stereochemistry of oxygenation matches that of hydrogen removal in the desaturation process. Thus methyl 9-thiastearate S-oxide (>96% ee), obtained via incubation of the corresponding sulfide with S. cerevisiae ATCC 12341, was shown to possess the R configuration. (R)-Methyl 10-thiastearate S-oxide (91% ee) was produced from the corresponding sulfide via the same catalytic system although less efficiently. (S)-(+)-alpha-Methoxyphenylacetic acid was used as a chiral NMR shift reagent to determine the optical purity and absolute configuration of these quasisymmetrical dialkyl sulfoxides. (S)-S-Benzyl-8-mercaptooctanoic acid methyl ester S-oxide was obtained by DELTA-9-desaturase-mediated sulfoxidation in 40-50% isolated yield and with high enantioselectivity (>98% ee). The absolute configuration was established by synthesizing both optical antipodes of benzyl decyl sulfoxide from the corresponding diastereomeric menthyl phenylmethanesulfinates. The correlation was then established by polarimetry, circular dichroism, and chiral shift reagent H-1 NMR. S-Benzyl-9-mercaptononanoic acid methyl ester S-oxide (88% ee) was produced far less efficiently and was also shown to have the S configuration. In both the dialkyl and benzyl series, sulfoxidation at the 9-position is consistently more efficient than at the 10-position, which seems to indicate that dehydrogenation of stearoyl CoA is initiated at C-9.
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页码:5073 / 5080
页数:8
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