MNBA-mediated β-lactone formation: Mechanistic studies and application for the asymmetric total synthesis of tetrahydrolipstatin
Various β-lactones were prepared from β-hydroxycarboxylic acids by intramolecular dehydration condensation using MNBA, an effective coupling reagent, along with a nucleophilic catalyst. The transition state that provides the desired 4-membered ring model system is disclosed by density functional theory (DFT) calculations, and the structural features of the transition form are discussed. This method was successfully applied to the asymmetric total synthesis of tetrahydrolipstatin (THL), an antiobestic drug used in clinical treatment to inhibit the activity of pancreatic lipase.
The catalytic asymmetric aldol reaction of aldehydes with unsubstituted and monosubstituted silyl ketene acetals: Formation of anti-β-hydroxy-α-methyl esters
The title rection with unsubstituted and monosubstituted silyl ketene acetals proceeds with high enantioselectivity, and in the latter case good diastereoselectivity favoring the anti-β-hydroxy-α-methyl esters in all reported cases.
Parmee,Hong,Tempkin,Masamune
p. 1729 - 1732
(2007/10/02)
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