Synthesis of Enantiopure 5-Substituted 2,3-Methanopyrrolidines by Cyclization of Enantiopure α-Branched α-N-Homoallylamino Nitriles

The preparation of 5-substituted 2,3-methanopyrrolidines by the stereoselective cyclization of zincated α-amino nitriles derived from enantiopure α-branched homoallylamines has been investigated. The formation of trans adducts in excellent diastereoselectivities (up to >98:2) and good yields (up to 71%) is observed. The absolute configuration and enantiomeric excess are dependent on the nitrogen protecting group.