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

Abstract

In recent decades, the synthesis of amino acid - triazole conjugates has become an emerging area. L- And D-azidohomoalanine derivs. readily undergo copper(I)-catalyzed azide-alkyne dipolar cycloaddn. reaction. The expected 4-substituted-1H-1,2,3-triazol-1-yl-homoalanines are obtained in the reactions of either N- and O-protected or protecting-group-free azidohomoalanines with various alkynes. 1,2,3-Triazole conjugate formation tolerates various functional groups. The synthetic approach that uses N- and O-protected starling materials relays on the std. chromatog. purifn. of intermediates that are further deprotected by hydrogenolysis. In this way, the purifn. of final products is not required. The synthetic approach that uses protecting-group-free azidohomoalanine is faster from a synthetic point of view as it includes only one step. However, the purifn. of protecting-group-free amino acid derivs. is laborious. Addnl., we have shown that the chiral stationary phase CROWNPAK CR(+), which is based on chiral crown ether as a selector, is applicable for direct chromatog. detn. of enantiomeric ratio of the title products. [on SciFinder(R)]