Abstract A wide range of cyclic and open-chain α, α-disubstituted α-amino acids 1a-p were prepared. The racemic N-acylated α, α-disubstituted amino acids were resolved by coupling to chiral amines 15-18 derived from (S)-phenylalanine to form diastereoisomers 19/20 or 21/22 that could be separated by crystallization and/or flash chromatography on silica gel (Scheme 3). Selective cleavage via the 1, 3-oxazol-5 (4H)-ones 10a-p gave the ...