Organocatalytic double Michael reaction of 7-oxohept-2-enoates and nitrostyrene -: Formal synthesis of (-)-α- and (-)-β-lycorane

Organocatalytic conjugate addition of 7-oxohept-2-enoate to nitrostyrene provided an omega-nitro-alpha,beta-unsaturated ester. Subsequent intramolecular cyclization afforded the highly functionalized cyclohexane carboester with four stereogenic centers with high diastereoselectivity and high enantioselectivity (> 99% ee). Some adducts were transformed into the intermediates of the synthesis of (-)-alpha- and (-)-beta-lycorane. Application of the reactions to the corresponding dialdehyde provided bicyclo [2.2.2]octanes. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).