Lewis acid-catalyzed stereoselective lactonization and subsequent glycosidation of 2-C-malonyl carbohydrates.
نویسندگان
چکیده
Gold(III) bromide is a suitable catalyst for the stereoselective cyclization of 2-C-malonyl carbohydrates to the anomeric center under retention of one ester group. Reopening of the lactones with alcohols in the presence of TMSOTf affords allyl, propargyl and benzyl glycosides with high α-selectivity.
منابع مشابه
Carbohydrates as Chiral Templates : Stereoselective Synthesis of ( R ) - and ( S ) - ~ - Aminophosphonic Acid Derivatives
The stereoselective synthesis of diethyl (S)or (R)-IX-[( O-pivaloylhexapyranosyl)amino]benzylphosphonates is achieved via Lewis acid catalyzed addition of diethyl phosphite to O-pivaloylated Nbenzylidene-{3-D-galactosylamine or N-benzylidene-IX-D-arabinopyranosylamine. The process can also be performed by a one-pot procedure selectively giving (S)-aminophosphonic acid derivatives from galactosy...
متن کاملHighly trans-stereoselective synthesis of bicyclic isoxazolidines via copper-catalyzed triple cascade catalysis.
A triple cascade was developed using a simple copper catalyst to trans-selectively access bicyclic isoxazolidines in a one-pot synthesis. This strategy features the in situ generation of nitrones and subsequent trapping by [3 + 2] cycloaddition. In this method, copper serves three catalytic functions: as a Lewis acid for the ene reaction, as an organometallic for aerobic oxidation, and as a Lew...
متن کاملUnderstanding the cooperative NHC/LA catalysis for stereoselective annulation reactions with homoenolates. A DFT study.
The role of Ti(Oi-Pr)(4) Lewis acid (LA) in the cooperative N-heterocyclic carbene (NHC)/LA catalyzed addition of enals to enones to yield cis-cyclopentenes has been investigated using DFT methods at the B3LYP/6-31G** computational level. Ti(IV) effectively catalyzes the reaction by formation of a complex with cinnamaldehyde 1, which favors the nucleophilic attack of NHC 5 on 1, and the subsequ...
متن کاملCatalytic Kinetic Resolution of a Dynamic Racemate: Highly Stereoselective β-Lactone Formation by N-Heterocyclic Carbene Catalysis.
This study describes the combined experimental and computational elucidation of the mechanism and origins of stereoselectivities in the NHC-catalyzed dynamic kinetic resolution (DKR) of α-substituted-β-ketoesters. Density functional theory computations reveal that the NHC-catalyzed DKR proceeds by two mechanisms, depending on the stereochemistry around the forming bond: 1) a concerted, asynchro...
متن کاملRegio- and stereoselective selenium dioxide allylic oxidation of (E)-dialkyl alkylidenesuccinates to (Z)-allylic alcohols: synthesis of natural and unnatural butenolides.
The first SeO(2) induced (Z)-selective allylic alcohol formation of dialkyl alkylidenesuccinates has been demonstrated to accomplish one-step syntheses of several essential butenolides and fused butenolides via an unusual E- to Z- carbon-carbon double bond isomerisation followed by the lactonization pathway. The observed regio- and stereoselective SeO(2) allylic oxidation protocol has also been...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Chemical communications
دوره 47 37 شماره
صفحات -
تاریخ انتشار 2011