The preparation of sterically hindered and polyfunctional C α, α-disubstituted α-amino acids (ααAAs) via alkylation of ethyl nitroacetate and transformation into derivatives ready for incorporation into peptides are described. Treatment of ethyl nitroacetate with N, N- diisopropylethylamine (DIEA) in the presence of a catalytic amount of tetraalkylammonium salt, followed by the addition of an activated alkyl halide or Michael acceptor, gives the ...