Asymmetric Synthesis of α‐Methyl α‐Amino Acids by Diastereoselective Alkylation of Optically Active 6‐Isopropyl‐3‐methyl‐2,3—dihydro‐6H‐1,4‐oxazin‐2‐ones

At room temperature already highly diastereoselective alkylation of the new, cyclic, chiral alanine ester derivatives (6R)-1 can been achieved with either K2CO3 as base under solid–liquid phase-transfer catalysis or Pd catalysis unter neutral conditions. The products (3S,6R)-2 can be easily hydrolyzed to form (S)-α-methyl α-amino acids.