501330-87-6Relevant academic research and scientific papers
Enantioselective synthesis of α-alkyl-β-ketoesters: Asymmetric Roskamp reaction catalyzed by an oxazaborolidinium ion
Gao, Lizhu,Kang, Byung Chul,Hwang, Geum-Sook,Ryu, Do Hyun
supporting information; experimental part, p. 8322 - 8325 (2012/09/08)
Breaking kamp: A catalytic route toward chiral α-alkyl-β- ketoesters using the title reaction of α-alkyl diazoester with aldehydes has been developed (see scheme). The reaction proceeds with high to excellent enantioselectivities and this methodology was applied to a concise two-step synthesis of the natural pheromone sitophilate. Copyright
Substrate range of the titanium TADDOLate catalyzed asymmetric fluorination of activated carbonyl compounds
Bertogg, Andreas,Hintermann, Lukas,Huber, Dominique P.,Perseghini, Mauro,Sanna, Maria,Togni, Antonio
experimental part, p. 353 - 403 (2012/05/07)
The substrate range of the [TiCl2(TADDOLate)] (TADDOL=α,α,α′,α′-tetraaryl-1,3-dioxolane-4, 5-dimethanol)-catalyzed asymmetric α-fluorination of activated β-carbonyl compounds has been investigated. Optimal conditions for catalysis are characterized by using 5 mol-% of TiCl2(naphthalen-1- yl)-TADDOLate) as catalyst in a saturated (0.14 mol/l) MeCN solution of F-TEDA (1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis- [tetrafluoroborate]) at room temperature. A series of α-methylated β-keto esters (3-oxobutanoates, 3-oxopentanoates) with bulky benzyl ester groups (60-90% ee) or phenyl ester (67-88% ee) have been fluorinated readily, whereas α-acyl lactones were also readily fluorinated, but gave lower inductions (13-46% ee). Double stereochemical differentiation in β-keto esters with chiral ester groups raised the stereoselectivity to a diastereomeric ratio (dr) of up to 96.5:3.5. For the first time, β-keto S-thioesters were asymmetrically fluorinated (62-91.5% ee) and chlorinated (83% ee). Lower inductions were observed in fluorinations of 1,3-diketones (up to 40% ee) and β-keto amides (up to 59% ee). General strategies for preparing activated β-carbonyl compounds as important model substrates for asymmetric catalytic α-functionalizations are presented (>60 examples). Copyright
Efficient synthesis of enantiomerically pure β2-amino acids via chiral isoxazolidinones
Lee, Hee-Seung,Park, Jin-Seong,Kim, Byeong Moon,Gellman, Samuel H.
, p. 1575 - 1578 (2007/10/03)
We report a practical and scalable synthetic route for the preparation of α-substituted β-amino acids (β2-amino acids). Michael addition of a chiral hydroxylamine, derived from α-methylbenzylamine, to an α-alkylacrylate followed by cyclization gives a diastereomeric mixture of α-substituted isoxazolidinones. These diastereomers are separable by column chromatography. Subsequent hydrogenation of the purified isoxazolidinones followed by Fmoc protection affords enantiomerically pure Fmoc-β2-amino acids, which are useful for β-peptide synthesis. This route provides access to both enantiomers of a protected β2-amino acid.
