Enantiopure 1,2,3-Triazolyl-β-amino Acids via Click Cycloaddition Reaction on Racemic Alkynyl Precursors Followed by Separation of Stereoisomers

In recent years, peptidomimetics have gained enormous importance in drug design aiming to achieve increased drug metabolic stability and higher selectivity. In the field of peptidomimetics, β-peptides incorporating β2- and β3-amino acids (the higher homologs of natural α-amino acids) provide a powerful method for the synthesis of peptidomimetics with particular secondary structures. In this regard, 1,2,3-triazole-modified peptidomimetics can act as effective peptide surrogates, and therefore have gained considerable attention. In the present report, 1,4-disubstituted 1,2,3-triazoles attached to β-amino acids were prepared selectively from the corresponding alkynyl-β2-amino acids according to Huisgen’s copper-catalyzed 1,3-dipolar cycloaddition (CuAAC), under mild conditions and with very high efficiency. Different azide derivatives, including some incorporating α-amino acids, were employed in this cycloaddition reaction. The enantiopure compounds were obtained via diastereomeric salt formation with chiral adjuvants, and subsequent separation.