De Novo Synthesis of 2-Substituted syn-1,3-Diols via an Iterative Asymmetric Hydration Strategy
摘要:
The enantioselective syntheses of several protected 4-substituted syn-3,5-dihydroxy carboxylic esters have been achieved from the corresponding achiral (E,E)- or (E,Z)-1,3-dienoates. The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-catalyzed reduction to form gamma-substituted delta-hydroxy-1-enoates. The resulting delta-hydroxy-1-enoates are subsequently converted into benzylidene-protected 4-substituted syn-3,5-dihydroxy carboxylic esters in one step. The benzylidene-protected 3,5-dihydroxy carboxylic esters are produced in good overall yields (20-54%) and high enantiomeric excess (73- 97% ee).
Silylene-Mediated Polarity Reversal of Dienoates: Additions of Dienoates to Aldehydes at the δ-Position To Form <i>trans</i>-Dioxasilacyclononenes
作者:Christian C. Ventocilla、K. A. Woerpel
DOI:10.1021/ja109631z
日期:2011.1.26
trans-dioxasilacyclononenes as single stereoisomers. This reaction, which converts the δ-position of the unsaturated carbonyl compound into a nucleophilic center, represents an inversion of polarity from the normal pattern of reactivity. The stereospecificity of the reaction suggests that the addition to aldehydes occurred through a closed, chairlike six-membered transition state. This reaction can be