Novel asymmetric oxy‐michael addition reaction of the chiral ketones to the achiral γ‐ or δ‐hydroxy‐α,β‐unsaturated carbonyl compounds

A novel asymmetric oxy-Michael addition reaction was developed. In the presence of a catalytic amount of base, chiral ketones 1 and 2, derived from D-glucose and D-fructose, respectively, reacted with omega-hydroxy enones or enoates 3a-e, 17 and 21 to form the hemiacetal-derived alkoxide which underwent stereoselective intramolecular Michael addition to give cyclic acetals. Although the stereoselectivities in the formation of the five-membered acetal rings were modest, six-membered ring formation proceeded with high stereoselectivity and the utility of the reaction was demonstrated by a simple syntheses of natural products.