Stereocontrolled Synthesis of Some Novel Azaheterocyclic beta-Amino Ester Stereoisomers with Multiple Stereogenic Centers

The synthesis of some new functionalized azaheterocyclic beta-amino esters with multiple stereocenters has been achieved from readily available unsaturated bicyclic beta-amino acids by a stereocontrolled synthetic protocol involving N-allylation/propargylation, ring-opening metathesis, and selective ring closure with chemodifferentiation through ring-closing metathesis (RCM). The RCM transformation was investigated under various experimental conditions to analyze the scope of the catalyst, yield, conversion, and substrate effect. The structure of the starting (oxa)norbornene beta-amino acids predetermined the structure of the new azaheterocyclic derivatives; the synthetic procedure proceeded with conservation of the configuration of the stereogenic centers.