Easy access to orthogonally protected α-alkyl aspartic acid and α-alkyl asparagine derivatives by controlled opening of β-lactams

The controlled opening of the N1C2 bond in 1-carbamate-substituted 2-azetidinones derived from amino acids by O- and N-nucleophiles provided a straightforward access to orthogonally protected α-alkyl aspartic acid and asparagine derivatives. The use of DBU or sodium azide as additive is essential for expedient cleavage by amino acids to the corresponding β-aspartic acid dipeptides.