Stereoselective synthesis of chiral oxepanes and pyrans through intramolecular nitrone cycloaddition in organized aqueous media.

[reaction: see text] A highly stereoselective surfactant-catalyzed intramolecular nitrone (formed by dehydration in water) cycloaddition in aqueous media leading to exclusive formation of a single isomer is reported. Either oxepane or pyran is formed from 3-O-allyl furanoside derivatives, which constitute the framework of a large number of biologically active compounds. Therefore, the environmentally friendly, efficient, and highly stereoselective syntheses of these chiral intermediates are still a meaningful pursuit.