Diastereodivergent Aldol Reactions of β-Alkoxy Ethyl Ketones: Modular Access to (1,4)-<i>syn</i> and -<i>anti</i> Polypropionates
作者:Fatih Arikan、Jun Li、Dirk Menche
DOI:10.1021/ol801292t
日期:2008.8.21
Asymmetric substrate-controlled aldol reactions of ethyl ketones of type 4 with aldehyde 3 are reported. Modular access to all possible syn- and anti-aldol products was obtained by careful choice of reaction conditions. To achieve good selectivities in this diastereodivergent approach, selection of the protective group on the beta-oxygen of the enolate (R (2)) was of critical importance.
A highlystereoselective joint total synthesis of the potent polyketide macrolide antibiotics etnangien and etnangien methyl ester was accomplished by a convergent strategy and proceeds in 23 steps (longest linear sequence). Notable synthetic features include a sequence of highlystereoselective substrate-controlled aldolreactions to set the characteristic assembly of methyl- and hydroxyl-bearing