Optically pure alpha-methyl-alpha-alkyl amino aldehydes were efficiently synthesized from the cyclohexylimine of propanal bearing an alpha-4(R),5(S)-diphenyl-2-oxazolidinone by asymmetric alkylation of the imine anion. alpha-Methylphenylalanine and alpha-methylleucine were synthesized in two steps from the corresponding amino aldehydes. Utilizing an oxaziridine rearrangement, amino aldehydes were converted to dipeptides in which both the amino and carboxy components were alpha,alpha-disubstituted.