Enantioselective, Organocatalytic Oxy-Michael Addition to γ/δ-Hydroxy-α,β-enones: Boronate-Amine Complexes as Chiral Hydroxide Synthons
作者:De Run Li、Andiappan Murugan、J. R. Falck
DOI:10.1021/ja076802c
日期:2008.1.1
An organocatalytic, enantioselective oxy-Michael addition to achiral gamma- and delta-hydroxy-alpha, beta-enones was developed. The key transformation is an unprecedented, asymmetric conjugate addition triggered by complexation between an in situ generated boronic acid hemiester and a chiral amine catalyst. Functionally, the intermediate amine-boronate complex acts as a chiral hydroxide surrogate or synthon. The resultant chiral beta-hydroxy-ketones are obtained in good to excellent yields and high ee following mild oxidative removal of the cyclic boronate. Natural products (R,12Z,15Z)-2-hydroxy-4-oxohenicosa-12,15-dienyl acetate and (+)-(S)-streptenol A were synthesized to demonstrate the utility of this reaction.
Synthesis of the Spirocyclic Framework of Sesterterpenoid Natural Products
作者:Jonathan G. Hubert、Daniel. P. Furkert、Margaret A. Brimble
DOI:10.1021/jo502897u
日期:2015.3.6
A convergent synthetic route to the sesterterpenoid framework of the bioactive phorbaketal and alotaketal natural product families has been established. The synthetic approach hinges on a Hosomi–Sakurai coupling of complex acetal and allylsilane coupling partners, followed by DDQ-promoted oxidative cyclization of highly unsaturated advanced intermediates. This robust synthetic approach enables further