Asymmetric Metal‐Templated Route to Amino Acids with 3‐Spiropyrrolidine Oxindole Core via a 1,3‐Dipolar Addition of Azomethine Ylides to a Chiral Dehydroalanine Ni(II) Complex

We herein developed a protocol for the asymmetric synthesis of artificial AAs featuring a 3-spiropyrrolidine oxindole skeletal with continuous tetrasubstituted carbon stereocenters by a 1,3-dipolar cycloaddition reaction of in situ generated azomethine ylides with a chiral dehydroalanine Ni(II) complex. A three-component reaction of the Ni(II) complex with various isatins and AAs in green solvent (ethanol) provided series of diastereomeric complexes with high dr (>20:1) in 40–86% yields. The formation of different regioisomers in the case of sarcosine and proline was explained using quantum chemical calculation. The acidic decomposition of the obtained Ni(II) complexes led to the target unnatural complex AAs with a 3-spiropyrrolidine oxindole core. The chiral auxiliary ligand was recovered after decomposition and reused for the synthesis of the starting dehydroalanine complex-substrate.