Unexpected synthesis of aziridines under CU(I) catalyzed kinugasa conditions assisted by microwave irradiation

International audienceCu(I)-catalyzed 1,3-dipolar cycloaddition between chiral nitrone and terminal alkynes under microwave irradiation afforded a series of enantiopure aziridines with the creation of two contiguous stereogenic centers

Crystal structure of 2-isopropyl-5,7'-dimethyl-1',3',3a',6',8a',8b'-hexa-hydro-spiro-[cyclo-hexane-1,6-furo[3,4-d]imidazo[1,5-b]isoxazol]-8'(7'H)-one

International audienceIn the title compound, C17H28N2O3, the isoxazolidine ring adopts an envelope conformation with the O atom deviating from the mean plane of the other four ring atoms by 0.617 (1) Å. In the crystal, mol-ecules are linked via weak C-H⋯O hydrogen bonds, forming chains which extend along the b-axis direction

Study of the Regio- and Stereoselectivity of [3+2] Cycloaddition of Nitrile Oxides to Various Racemic 3-acyloxy and 3-hydroxybut-1-enes

International audience1,3-Dipolar cycloadditions of aryl nitrile oxides 2d-f to various racemic 3-hydroxy- and 3-acyloxy-but-1-enes 1a-c proceeded with complete regioselectivity to afford the corresponding 3,5-disubstituted isoxazolines in good yields. The steric and/or electronic effect of an acyloxy group at the allylic position on the stereoselectivity has been studied

Study of the Regio- and Stereoselectivity of [3+2] Cycloaddition of Nitrile Oxides to Various Racemic 3-acyloxy and 3-hydroxybut-1-enes

International audience1,3-Dipolar cycloadditions of aryl nitrile oxides 2d-f to various racemic 3-hydroxy- and 3-acyloxy-but-1-enes 1a-c proceeded with complete regioselectivity to afford the corresponding 3,5-disubstituted isoxazolines in good yields. The steric and/or electronic effect of an acyloxy group at the allylic position on the stereoselectivity has been studied

Crystal structure of 2-isopropyl-5,7'-dimethyl-1',3',3a',6',8a',8b'-hexa-hydro-spiro-[cyclo-hexane-1,6-furo[3,4-d]imidazo[1,5-b]isoxazol]-8'(7'H)-one

International audienceIn the title compound, C17H28N2O3, the isoxazolidine ring adopts an envelope conformation with the O atom deviating from the mean plane of the other four ring atoms by 0.617 (1) Å. In the crystal, mol-ecules are linked via weak C-H⋯O hydrogen bonds, forming chains which extend along the b-axis direction

Stereoselective synthesis of enantiopure cycloalkylglycines by 1,3-dipolar cycloaddition of a chiral nitrone to cycloalkenes

International audienceThe design of cyclic analogues of 4-hydroxyisoleucine, a natural remedy used by type-2 diabetic patients, can provide putative hypoglycemic drugs. To this end, the 1,3-dipolar cycloaddition of a (–)-menthone-derived nitrone to cycloalkenes afforded isoxazolidines in high yields and with high stereoselectivity. The cycloadducts led to α-amino lactones after a one-pot cleavage of the N–O, amide, and N–C–N bonds. Subsequent base-catalyzed hydrolysis provided enantiopure cycloalkylglycine derivatives in good overall yields (>40 %) in three simple synthetic steps from the menthone-based chiral nitrone. The conformational analysis of these analogues by DFT calculations highlight some interesting features of the volume occupied by the cycloalkyl residues in comparison to that occupied by the natural 4-hydroxyisoleucine