Synthesis of Enantiomerically Enriched 1,2,3- Triazole-derivatized Homoalanines

In recent decades, the synthesis of amino acid –triazole conjugates has become an emerging area. L- and Dazidohomoalaninederivatives readily undergo copper(I)-catalyzed azide-alkyne dipolar cycloaddition reaction. Theexpected 4-substituted-1H-1,2,3-triazol-1-yl-homoalanines areobtained in the reactions of either N- and O-protected orprotecting-group-free azidohomoalanines with various alkynes.1,2,3-Triazole conjugate formation tolerates various functionalgroups. The synthetic approach that uses N- and O-protectedstarting materials relays on the standard chromatographicpurification of intermediates that are further deprotected byhydrogenolysis. In this way, the purification of final products isnot required. The synthetic approach that uses protecting-groupfreeazidohomoalanine is faster from a synthetic point of view asit includes only one step. However, the purification of protectinggroup-free amino acid derivatives is laborious. Additionally, wehave shown that the chiral stationary phase CROWNPAK® CR(+),which is based on chiral crown ether as a selector, is applicablefor direct chromatographic determination of enantiomeric ratioof the title products