Nitrone Cycloaddition in the Stereoselective Synthesis of β-Carbolines from N-Hydroxytryptophan

Article abstract of DOI:10.1021/jo00353a007

The cycloaddition chemistry of nitrone 6, obtained by treatment of N-hydroxytryptophan ester 4 with methyl orthoformate, has been evaluated. 1,3-Dipolar cycloadditions with alkenes proceed with high or complete regioselectivity to yield 4'- or 5'-substituted isoxazolidines (Scheme II).Complete C(3) C(1) trans induction as well as high or complete stereoselectivity at the other newly introduced chiral center C(4') or C(5') is observed.The regiochemical course of these reactions is as predicted by frontier molecular orbital theory.