| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1345898 | Tetrahedron: Asymmetry | 2013 | 7 Pages |
Herein we report results of the chemoenzymatic deracemization of a range of secondary benzylic acetates 1a–9a via a sequence of hydrolysis with CAL-B lipase in non-conventional media, combined with esterification of the recovered alcohol according to the Mitsunobu protocol following an enzymatic kinetic resolution (KR). The KR of racemic acetates 1a–9a via an enzymatic hydrolysis, with CAL-B lipase and Na2CO3, in non-aqueous media was optimized and gave high selectivities (E ≫ 200) at good conversions (C >49%) for all of the substrates studied. This method competes well with the traditional one performed in a phosphate buffer solution. The deracemization using Mitsunobu inversion gave the (S)-acetates in moderate to excellent enantiomeric excess 75% < ee < 99%, in acceptable isolated yields 70% < yield < 89%, and with some variations according to the acetate structure.
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(S)-(−)-1-Phenylethyl acetateC10H12O2Ee >99%. By GC on CHIRALSIL-DEX CB column[α]D20=-136 (c 0.1, CHCl3)Source of chirality: asymmetric catalysis.Absolute configuration: (S)
(S)-(−)-1-(4-Methoxyphenyl)ethyl acetateC11H14O3Ee = 57%. By GC on CHIRALSIL-DEX CB column[α]D20=-8 (c 0.2, CHCl3)Source of chirality: asymmetric catalysis.Absolute configuration: (S)
(S)-(−)-1-(4-Ethoxyphenyl)ethyl acetateC12H16O3Ee = 60%. By GC on CHIRALSIL-DEX CB column[α]D20=-70.8 (c 0.5, CHCl3)Source of chirality: asymmetric catalysis.Absolute configuration: (S)
(S)-(−)-1-(Naphthalen-1-yl)ethyl acetateC14H14O2Ee = 99%. By HPLC on CHIRACEL OD-H column[α]D20=-46.5 (c 0.2, CHCl3)Source of chirality: asymmetric catalysisAbsolute configuration: (S)
(S)-(−)-1-(Naphthalen-2-yl)ethyl acetateC14H14O2Ee = 92%. By GC on CHIRALSIL-DEX CB column[α]D20=-104 (c 0.2, CHCl3)Source of chirality: asymmetric catalysisAbsolute configuration: (S)
(S)-(−)-1-(6-Methoxynaphthalen-2-yl) ethyl acetateC15H16O3Ee = 65%. By GC on CHIRALSIL-DEX CB column[α]D20=-64.5 (c 0.3, CHCl3)Source of chirality: asymmetric catalysisAbsolute configuration: (S)
(S)-(−)-2,3-Dihydro-1H-indenyl acetateC11H12O2Ee = 90%. By GC on CHIRALSIL-DEX CB column[α]D20=-100 (c 0.5, CHCl3)Source of chirality: asymmetric catalysis.Absolute configuration: (S)
(S)-(−)-1,2,3,4-Tetrahydronaphthalen-1-yl acetateC12H14O2Ee = 90%. By GC on CHIRALSIL-DEX CB column[α]D20=-97.5 (c 0.5, CHCl3)Source of chirality: asymmetric catalysisAbsolute configuration: (S)
(S)-(−)-1-Acenaphthyl acetateC14H12O2Ee = 90%. By HPLC on (Chiralcel® ODH) column[α]D20=-79.4 (c 0.2, CHCl3)Source of chirality: asymmetric catalysisAbsolute configuration: (S)
