Efficient kinetic resolution of racemic 3-nitro-cyclopent(or hex)-2-en-1-yl acetates (original) (raw)
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Tetrahedron-asymmetry, 2011
Possible routes for the enzymatic transformation of various substituted 1-(5-phenylfuran-2-yl)ethane-1,2-diols and their mono- and diacetylated counterparts were studied. Combining the regioselectivity of LPS mediated acylation of the starting racemic diols, the stereoselectivity of LAK shown in the enantiomer selective transformation of the previously formed racemic primary acetates and the LPS mediated mild hydrolysis–alcoholysis of the resolution products, an efficient preparative scale procedure for the synthesis of various highly enantiomerically enriched (R)- and (S)-phenylfuran-2-yl-ethane-1,2-diols has been developed.(S)-2-(5-(2-Chlorophenyl)furan-2-yl)-2-hydroxyethyl acetateC14H13ClO4Ee = 97% on Chiralpak AS-H HPLC column[α]D25=-6.7 (c 0.5, CHCl3)Source of chirality: lipase mediated kinetic resolutionAbsolute configuration: (S)(S)-2-(5-(4-Bromophenyl)furan-2-yl)-2-hydroxyethyl acetateC14H13BrO4Ee = 96% on Chiralpak AS-H HPLC column[α]D25=-10.4 (c 0.5, CHCl3)Source of chirality: lipase mediated kinetic resolutionAbsolute configuration: (S)(S)-2-Hydroxy-2-(5-(2-nitrophenyl)furan-2-yl)ethyl acetateC14H13NO6Ee = 95% on Chiralpak AS-H HPLC column[α]D25=-23.8 (c 0.5, CHCl3)Source of chirality: lipase mediated kinetic resolutionAbsolute configuration: (S)(S)-2-Hydroxy-2-(5-(4-nitrophenyl)furan-2-yl)ethyl acetateC14H13NO6Ee = 93% on Chiralpak IB HPLC column[α]D25=-18.7 (c 0.5, CHCl3)Source of chirality: lipase mediated kinetic resolutionAbsolute configuration: (S)
2021
In this work, a racemization method of (S)-1-phenylethanol by niobium salts was developed. Among the salts available, the niobium phosphate hydrate (NbOPO4.nH2O) reduced the enantiomeric excess (ee) of the chiral alcohol from 95 to 0% after 24 h at 60 oC in toluene. This new racemization agent was combined with a lipase (CALB) in order to achieve a chemoenzymatic dynamic kinetic resolution (DKR). Experiments demonstrated that the DKR process is feasible and the corresponding (R)-1-phenylethyl acetate was obtained with 92% conversion and 85% ee.
Lipase-catalyzed solvent-free kinetic resolution of substituted racemic e-caprolactones
Tetrahedron Asymmetry, 2002
The kinetic resolution of racemic seven-membered lactones is reported, for the first time in bulk (solvent-free) conditions, by lipase-catalysed butanolysis. The lactones studied were substituted at either the 4- or the 6-position. With these lactones, Novozym-435 lipase (from Candida antarctica) induced (S)-selective butanololysis, and (R)-lactones were recovered unreacted with >97% enantiomeric excess (e.e.). The reactions were studied at different reaction temperatures, viz. 0, 23, 40 and 60°C. A comparative study of the effect of temperature on the kinetic resolution is presented.Graphic(R)-(+)-4-Methyl-ε-caprolactoneC7H12O2E.e. >97%[α]D23=+40 (c 0.5, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: R(R)-(+)-4-Ethyl-ε-caprolactoneC8H14O2E.e. >99%[α]D23=+42 (c 0.5, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: R(R)-(+)-6-Methyl-ε-caprolactoneC7H12O2E.e. >99%[α]D23=+18 (c 0.5, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: R(S)-n-Butyl 6-acetoxy-4-methylhexanoateC13H24O4E.e. >99%[α]D23=−2.2 (c 1, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: S(S)-n-Butyl 6-acetoxy-4-ethylhexanoateC14H26O4E.e. >99%[α]D23=−0.7 (c 0.7, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: S