The first enzymatic resolution of quaternary α′-acetoxy α,β-unsaturated cyclohexenones and cyclopentenones

The enantioselective resolution of various quaternary α′-acetoxy α,β-unsaturated cyclohexenones and cyclopentenones was performed with the commercially available enzyme CCL in pH = 8.0 phosphate buffer. Various parameters that would affect the enantioselectivities were tested and the best enzymatic resolution conditions were found to afford the enantiomerically enriched quaternary acetoxylated substrates with high ee varying between 36% and 99%.

Figure optionsDownload as PowerPoint slide

(−)-6-Acetoxy-3,6-dimethyl-2-cyclohexen-1-oneC10H14O3Ee = 99%[α]D20=-13.1 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-6-Acetoxy-3,5,5,6-tetramethyl-2-cyclohexen-1-oneC12H18O3Ee = 62%[α]D20=-1.8 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-6-Acetoxy-4,4,6-trimethyl-2-cyclohexen-1-oneC11H16O3Ee = 94%[α]D20=-42.2 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-6-Acetoxy-6-methyl-4,4-diphenyl-2-cyclohexen-1-oneC21H20O3Ee = 73%[α]D20=-29.2 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-6-Acetoxy-6-ethyl-3-methyl-2-cyclohexen-1-oneC11H16O3Ee = 71%[α]D20=-12.5 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(+)-6-Acetoxy-6-benzyl-3-methyl-2-cyclohexen-1-oneC16H18O3Ee = 61%[α]D20=+0.4 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-6-Acetoxy-6-ethyl-3,5,5-trimethyl-2-cyclohexen-1-oneC13H20O3Ee = 45%[α]D20=-3.2 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(+)-6-Acetoxy-6-benzyl-3,5,5-trimethyl-2-cyclohexen-1-oneC18H22O3Ee = 36%[α]D20=+0.2 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-5-Acetoxy-3,5-dimethyl-2-cyclopenten-1-oneC9H12O3Ee = 99%[α]D20=-33.6 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-5-Acetoxy-5-ethyl-3-methyl-2-cyclopenten-1-oneC10H14O3Ee = 53%[α]D20=-8.4 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(+)-5-Acetoxy-5-benzyl-3-methyl-2-cyclopenten-1-oneC15H16O3Ee = 43%[α]D20=+1.2 (c 1.0, CHCl3)Source of chirality: enzymatic resolution

(−)-5-Acetoxy-2,3,5-trimethyl-2-cyclopenten-1-oneC10H14O3Ee = 90%[α]D20=-23.8 (c 1.0, CHCl3)Source of chirality: enzymatic resolution