Synthesis of unnatural amino acids: spiro[4.5]-2-aza-decan-3-carboxylic acid

Spiro[4.n]-2-aza-alkan-carboxylic acids represent bulky proline analogues with increased lipophilicity. They are readily available from cyclic nitriles via alkylation with bromoacetaldehyde acetals, reduction to the corresponding amine, cyclisation to the imine and subsequent Strecker synthesis.