An unexpected transformation by reduction of isoxazolines

Remarkable electronic effect on the total stereoselectivity of the cycloaddition reaction of arylnitrile oxides with pyrrol-2-one derivatives

The regiospecific 1,3-dipolar cycloaddition of 1,5-dihydropyrrol-2-one and arylnitrile oxides derivatives have been investigated. The asymmetric induction expected by the chiral centre of the 5-hydroxy-3-methyl-1,5-dihydropyrrol-2-one derivatives was very effective, single diastereoisomers anti-3 was formed. The diastereoselectivity was linked to the destabilization of the syn transition state as a result of the electrostatic repulsion between the hydroxy group of the dihydropyrrol-2-one derivatives and the atom oxygen of the dipole.

Synthesis of carbohydrate-substituted isoxazoles and evaluation of their antitubercular activity

Eight new sugar-substituted isoxazoles were synthesized by a 1,3-dipolar cycloaddition reaction of aromatic nitrile oxides with carbohydrate-substituted alkynes. Products were screened for antimycobacterial activity against the Mycobacterium tuberculosis H37Rv strain. Four compounds, 5e–h, significantly inhibit growth of the bacterial strain with a minimum inhibitory concentration (MIC) of 3.125 μg/mL.