Synthetic Approach to Phenylalanine-Proline, and Tyrosine-Proline Hybrid Amino Acids

Substituted proline derivatives represent an important class of conformationally constrained amino acids. The combination of the structural properties of proline and the side-chain of another amino acid could help the development of peptidomimetics and SAR study of active compounds. The presence of a phenyl or a p-hydroxy-phenyl ring on the pyrrolidine ring could be considered as phenylalanine- or thyrosine-proline hybrids. These compounds have shown the potential to mimic natural occurring peptides and can activate or inhibit the respective receptor. This review will focus on the chemical strategy applied to synthesize these analogues.