Double addition of grignard reagents to N-glycosyl nitrones: a new tool for the construction of enantiopure azaheterocycles.

[Reaction: see text] C-Phenyl-N-erythrosylnitrone 3 behaves as a C1,C1' bis-electrophile, undergoing a double addition of Grignard reagents in a domino fashion to afford acyclic hydroxylamines 4. The reaction proceeds at 0 degrees C with variable degrees of diastereoselectivity, from moderate to good, mainly depending on the organomagnesium reagent used. The usefulness of compounds 4 has been exemplified with the synthesis of pyrroloazepine 12 through a ring closing metathesis key step.