Efficient stereoselective nucleophilic addition of pyrroles to chiral nitrones

Abstract

Regioselective additions of pyrroles to a variety of optically active nitrones under smooth acidic conditions lead to chiral pyrrolic N-hydroxylamines in good to excellent yields. Depending on the position of the chirality on the nitrone partner, the addition products have been isolated with high diastereoselectivity levels. Reaction of glyoxylate based chiral nitrones either at the C-2 or at the C-3 position of the pyrrole nucleus afforded N-hydroxyamino esters in high yields as single diastereoisomers. These adducts allow access to enantio-enriched non proteinogenic 2′- and 3′-pyrrolylglycines (13 and 19 respectively).