Catalytic asymmetric epoxidation of alkenes with arabinose-derived ketones containing a cyclohexane-1,2-diacetal

The effect of diol blocking groups, cyclohexane-1,2-diacetal verses butane-1,2-diacetal, on the asymmetric epoxidation of trans- and cis-alkenes by arabinose-derived ketones is reported. The ketone catalysts with a cyclohexane-1,2-acetal display similar asymmetric induction as those catalysts with a butane-1,2-diacetal in most cases. For (E)-1-benzyloxy-4-hexene, the ee of the enantioselective epoxidation has reached 61% with the cyclohexane-1,2-dineopentyl acetal ketone catalyst.

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Benzyl 2,3-O-[(1′R,2′R)-dimethoxy-cyclohexane-1,2-dione diacetal]-β-l-arabinopyranosideC20H28O7Ee = 100%[α]D20=+38.7 (c 0.83, CHCl3)Source of chirality: l-arabinose as starting material

Benzyl 2,3-O-[(1′R,2′R)-dimethoxy-cyclohexane-1,2-dione diacetal]-β-l-arabinopyran-3-ulosideC20H26O7Ee = 100%[α]D20=+34.2 (c 1.42, CHCl3)Source of chirality: l-arabinose as starting material

Benzyl 2,3-O-[(1′R,2′R)-dineopentoxy-cyclohexane-1,2-dione diacetal]-β-l-arabinopyranosideC28H44O7Ee = 100%[α]D20=+36.4 (c 0.66, CHCl3)Source of chirality: l-arabinose as starting material

Benzyl 2,3-O-[(1′R,2′R)-dineopentoxy-cyclohexane-1,2-dione diacetal]-β-l-arabinopyran-3-ulosideC28H42O7Ee = 100%[α]D20=+18.8 (c 1.03, CHCl3)Source of chirality: l-arabinose as starting material