DIASTEREOSELECTIVE PREPARATION OF CYCLOPROPANE AMINO-ACIDS - SYNTHESIS OF NORCORONAMIC ACID

The 2-(benzylamino)-4-chlorobutyronitrile (3b), resulting from the addition of benzylamine to the cyanohydrin 2 (4-chloro-2-hydroxybutyronitrile), undergoes Swern N-oxidation followed by quantitative base-induced cyclization to provide the 1-aminocyclopropanecarboxylic acid (ACC) precursor 5d (1-benzylideneaminocyclopropanecarbonitrile). Analogously prepared from the chiral beta-hydroxyester 7 [(S)-(+)-methyl 3-hydroxy-2-methylpropionate], the nitrile amines 10a,b [2-(benzylamino)-4-chloro-3-methylbutyronitrile] undergo Swern N-oxidation and diastereoselective cyclization leading readily to the natural Norcoronamic acid [6; (1S,2S)-1-amino-2-methylcyclopropanecarboxylic acid (ds > 84%)].