Resolution of the enantiomers of tetrahydrozoline by chiral HPLC. The racemization of the enantiomers via an imine–enamine tautomerism

Resolution of the enantiomers of the sympathomimetic drug tetrahydrozoline was obtained by chiral HPLC. The isolated enantiomers racemize easily and chiral HPLC experiments allowed the determination of the racemization rate constant. This process occurs via an imine–enamine tautomerism which was studied by UV and ¹H NMR spectroscopies.     

Enantioselective aldol reactions of α,β-unsaturated ketones with trifluoroacetophenone catalyzed by a chiral primary amine

Chiral primary amine catalyzed direct asymmetric aldol reactions of ketones with trifluoroacetophenone, afforded trifluoromethylated β-hydroxycarbonyl aldol products bearing a quaternary carbon stereogenic center in high yields (up to 93% yield) and with high to excellent enantioselectivities of up to 99% ee.     

Highly enantioselective aldol reaction of acetone with β,γ-unsaturated α-keto esters promoted by simple chiral primary-tertiary diamine catalysts

A series of primary-tertiary diamine catalysts were successfully applied to promote the enantioselective aldol reaction of acetone with β,γ-unsaturated α-keto esters in excellent yields (up to 99%) and enantioselectivities (up to 96% ee).     

Stereoselective cyanation of chiral α-amino aldehydes by reaction with Nagata's reagent: a route to enantiopure β-amino-α-hydroxy acids

Chiral α-dibenzylamino aldehydes react with diethylaluminum cyanide leading to anti-β-dibenzylamino-α-hydroxycyanides as the major diastereoisomers in good yields and diastereomeric excesses. Hydrolysis of the nitrile derivatives allows the synthesis of enantiopure β-amino-α-hydroxy acids.     

An approach towards the formation of an ester bond between the primary hydroxyl of a β-D-galactopyranoside and 2-aminoethylphosphonic acid and N-methyl substituted derivatives

An expeditious method for the preparation of the phosphonylating reagent 2-bromoethylphosphonic acid is presented. The latter compound as well as salicylchlorophosphite proved to be suitable for the synthesis of methyl 0-6-(2′-aminoethylphosphonyl)-β-D-galactopyranoside and N-mono- or dimethylated derivatives thereof.     

One-Pot Synthesis of Enantioenriched β-Amino Secondary Amides via an Enantioselective [4+2] Cycloaddition Reaction of Vinyl Azides with N-Acyl Imines Catalyzed by a Chiral Brønsted Acid

A catalytic enantioselective synthesis of β-amino secondary amides was achieved using vinyl azides as the enamine-type nucleophile and chiral N-Tf phosphoramide as the chiral Brønsted acid catalyst through a five-step sequential transformation in one pot. The established sequential transformation involves an enantioselective [4+2] cycloaddition reaction of vinyl azides with N-acyl imines as the key stereo-determining step that is efficiently accelerated by a chiral N-Tf phosphoramide catalyst in a highly enantioselective manner in most cases. Further generation of the iminodiazonium ion intermediate through ring opening of the cycloaddition product and subsequent skeletal rearrangement involving Schmidt-type 1,2-aryl group migration followed by recyclization of the resulting nitrilium ion were also initiated by the same acid catalyst. Final acid hydrolysis of the recyclized products in the same pot gave rise to enantioenriched β-amino amides through C−C bond formation at the α-position of the secondary amides.