Highly Regio- and Enantioselective Organocatalytic Conjugate Addition of Alkyl Methyl Ketones to a β-Silylmethylene Malonate
作者:Raghunath Chowdhury、Sunil K. Ghosh
DOI:10.1021/ol900803n
日期:2009.8.6
(S)-N-(2-Pyrrolidinylmethyl)pyrrolidine/trifluoroacetic acid (3:1) combination catalyzed the direct addition of alkyl methyl ketones to β-dimethyl(phenyl)silylmethylene malonate at the methyl terminal with high yield and excellent regio- and enantioselectivity. The silyl group played crucial roles in regioselection and substrate reactivity.
Enantioselective Route to β-Silyl-δ-keto Esters by Organocatalyzed Regioselective Michael Addition of Methyl Ketones to a (Silylmethylene)malonate and Their Use in Natural Product Synthesis
作者:Sunil Ghosh、Raghunath Chowdhury
DOI:10.1055/s-0030-1260036
日期:2011.6
potential. This has been demonstrated by the synthesis of a suitably substituted β-silyl-δ-keto ester as an advanced intermediate for a chiral hydroxylated pyrrolidine natural product, (+)-preussin. Silicon-controlled diastereoselective reduction of the ketone functionality of β-silyl-δ-keto esters followed by lactonization of the resulting hydroxy esters gave disubstituted δ-valerolactones. Advanced