- Chemoenzymatic approach to optically active phenylglycidates: Resolution of bromo- and iodohydrins
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Enantiomerically enriched phenylglycidates, precursors of the taxol C-13 phenylisoserine side chain and diltiazem, were prepared by kinetic resolution of anti-2-bromo-3-hydroxy- and anti-3-hydroxy-2-iodophenylpropanoates to provide enantioriched (2R,3R)- and (2S,3S)-halohydrins. The bulkiness and inflexibility of bromo and iodo groups in halohydrins have made them inaccessible to the active site of most of the lipases utilized for the hydrolysis of their acyloxy derivatives. In a set of 22 hydrolases screened herein, including native as well as commercial enzymes, only Aspergillus niger (Lipase AS, AMANO) could catalyze the hydrolysis with high enantioselectivity (E = 176). The resolved halohydrins easily underwent transformation to the corresponding (2S,3R)- and (2R,3S)-phenylglycidates.
- Anand, Naveen,Kapoor, Munish,Koul, Surrinder,Taneja, Subhash C.,Sharma, Rattan L.,Qazi, Ghulam N.
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p. 3131 - 3138
(2007/10/03)
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- A new enantioselective synthesis of (2R,3S)-3-(4-methoxyphenyl)glycidic ester via the enzymatic hydrolysis of erythro-N-acetyl-β-(4- methoxyphenyl)serine
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Enantioselective synthesis of (2R,3S)-3-(4-methoxyphenyl)glycidic ester ((2R,3S)-1) via the enzymatic hydrolysis of erythro-N-acetyl-β-(4- methoxyphenyl)serine (9) was investigated. Treatment of the obtained α- amino acid (-)-10 with NaNO2-KBr-dilute H2SO4, esterification, and subsequent oxiran-ring closure of the halohydrin gave the target compound (2R,3S)-1 with high enantiomeric excess (94% ee).
- Inoue,Matsuki,Oh-Ishi
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p. 1521 - 1523
(2007/10/02)
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