A straighforward synthesis of 3-substituted azetidinic amino acids

Abstract

A series of enantiomerically pure N,N-disubstituted β-amino alcohols were chlorinated by treatment with thionyl chloride. This reaction afforded a mixture of regioisomeric β-amino chlorides that could be equilibrated to the more stable regioisomer by heating in DMF. The secondary chlorides thus obtained were engaged in an intramolecular anionic ring-closure to give access to fully protected enantio- and diastereoisomerically pure 2,3-cis-disubstituted azetidinic amino acid. One of the latter was deprotected for inclusion in a tripeptide sequence. This synthetic methodology was applied for N,N-disubstituted γ-amino alcohols, leading to 3- or 5- substituted proline derivatives but with a low 2,3- or 2,5- diastereoselectivity. ©ARKAT-USA, Inc.